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IEEE Transactions on Electron Devices
Journal Prestige (SJR): 0.839
Citation Impact (citeScore): 3
Number of Followers: 18  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9383
Published by IEEE Homepage  [228 journals]
  • IEEE ELECTRON DEVICES SOCIETY

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      Pages: C2 - C2
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • IEEE Transactions on Electron Devices Information for Authors

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      Pages: C3 - C3
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Blank Page

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      Pages: C4 - C4
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Guest Editorial Special Issue on Vacuum Electronic Devices, “From Mega
           to Nano: Beyond One Century of Vacuum Electronics”

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      Authors: Claudio Paoloni;
      Pages: 2639 - 2642
      Abstract: I am delighted and honored to open the sixth Special Issue on Vacuum Electronics published by IEEE TRANSACTIONS ON ELECTRON DEVICES (T-ED) “From Mega to Nano: Beyond One Century of Vacuum Electronics” following the successful Special Issues published in January 2001, May 2005, May 2009, June 2014, and June 2018.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Frontiers in the Application of RF Vacuum Electronics

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      Authors: Carter M. Armstrong;Emma C. Snively;Muhammad Shumail;Christopher Nantista;Zenghai Li;Sami Tantawi;Bill W. Loo;Richard J. Temkin;Robert G. Griffin;Jinjun Feng;Roberto Dionisio;Felix Mentgen;Natanael Ayllon;Mark A. Henderson;Timothy P. Goodman;
      Pages: 2643 - 2655
      Abstract: The application of radio frequency (RF) vacuum electronics for the betterment of the human condition began soon after the invention of the first vacuum tubes in the 1920s and has not stopped since. Today, microwave vacuum devices are powering important applications in health treatment, material and biological science, wireless communication—terrestrial and space, Earth environment remote sensing, and the promise of safe, reliable, and inexhaustible energy. This article highlights some of the exciting application frontiers of vacuum electronics.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • An Overview of Multibeam Klystron Technology

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      Authors: Yaogen Ding;David K. Abe;Bin Shen;Dongping Gao;Haibing Ding;
      Pages: 2656 - 2665
      Abstract: The multibeam klystron (MBK) is a compact high-power microwave vacuum electronic device that features low beam voltage, high efficiency, wide bandwidth, and low volume and weight. Since the 1960s, high-performance broadband MBKs have been developed that cover the entire microwave frequency band with relative instantaneous bandwidths $>$ 15%, peak power $>$ 1 MW, average power up to 40 kW, and efficiencies $>$ 40%. In recent years, driven by the needs of high-energy particle accelerators, ultra high frequency (UHF) and ${L}$ -band MBKs with peak powers of more than 20 MW and efficiencies of nearly 80% are being developed. This article presents an overview of the development of broadband MBKs used in microwave electronic systems, such as radar and communication, and high-power MBKs used in the RF systems of particle accelerators. It also introduces the latest progress and development trends in MBKs leading to higher frequency, output power, bandwidth, efficiency, and lifetime.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • First Principles Codes and Analysis Environments for Vacuum Electronics
           Simulation

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      Authors: John J. Petillo;Simon J. Cooke;Thomas M. Antonsen;Serguei G. Ovtchinnikov;Aaron J. Jensen;Eric M. Nelson;Kevin L. Jensen;Baruch Levush;
      Pages: 2666 - 2679
      Abstract: The status of first principles modeling and simulation tools for vacuum electronics (VEs) is presented. These tools, when combined with parametric beam-wave interaction tools, comprise the suite of tools that enable the design and optimization of VE devices, such as RF amplifiers. Although many basic algorithms discussed in the article have been around for decades, the advances in electromagnetic and electrostatic particle-in-cell and meshless beam codes have revolutionized the VE device development process where first-pass design has become the standard. These include advances in emission physics, disparate-mesh geometry resolution, advanced boundary conditions, intercode operability, multimodule simulation pipelines, exploitation of computer hardware, optimization and sensitivity analysis, and advanced user simulation environments with multimodule pipelines. The article presents these advances.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Advances in the Theory and Modeling of Linear Beam VE Amplifiers

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      Authors: Thomas M. Antonsen;Igor A. Chernyavskiy;David Chernin;Alexander N. Vlasov;Baruch Levush;
      Pages: 2680 - 2692
      Abstract: We present an overview of the progress made by our Naval Research Laboratory (NRL)-based group over the last 25 years in the development of computational tools used in the large-signal modeling and design of linear-beam vacuum electronic (VE) amplifiers, klystrons, and traveling-wave tubes (TWTs). These tools belong to a class of codes that we call parametric beam–wave interaction (PBWI) codes, which includes family of the codes CHRISTINE and TESLA. Notable progress includes the formulation and application of an impedance matrix description of a general class of slow wave circuits, the tracking of slow or reversed particles in klystrons, parallel modeling of multiple-beam devices, linear stability analysis based on Nyquist theory, and geometrical and electrical tolerance analysis and optimization based on solutions to the adjoint equations that govern the beam–wave interaction. The impedance matrix description, in particular, has allowed the detailed effects of circuit geometry, including complex terminations, matching sections, and severs, to be included in PBWI simulations for the first time.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Advanced Fabrication of Vacuum Electron Devices

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      Authors: R. Lawrence Ives;
      Pages: 2693 - 2701
      Abstract: RF source scientist and engineers continuously push the envelope with new designs, striving for improved performance with higher efficiency, higher frequency, greater bandwidth, increased gain, smaller size, lower voltage, and myriad other parameters required for ever more demanding applications. Invariably, it becomes more challenging to achieve the required fabrication and assembly performance with increasing complexity and precision. This publication reviews recent development on advanced fabrication technologies and describes the current state of the art in machining, assembly, and alignment capabilities.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Assessing Surface Roughness Effect in Gyrotrons With the Gradient
           Conductivity Model

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      Authors: Yu Huang;Houxiu Xiao;Xianfei Chen;Zhenglei Wang;Zhiyu Qiu;
      Pages: 2702 - 2706
      Abstract: To accurately characterize the effect of the cavity surface roughness on the ohmic loss in gyrotron oscillators, this article proposes a method by using the gradient conductivity (GC) assessment model, in which a derived effective conductivity parameter is used to characterize the surface roughness. The results show that it has higher accuracy than the conventional methods such as the H-B formula, especially in the terahertz frequency band. This model also provides a reasonable explanation for the low-efficiency problem in terahertz gyrotrons, and it is beneficial to promote the design and analysis of gyrotrons.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Investigation of a Novel Biperiodic Reltron for High-Power Microwave
           Generation

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      Authors: Manpuran Mahto;Pradip Kumar Jain;
      Pages: 2707 - 2711
      Abstract: A novel configuration of a reltron, referred to as the biperiodic reltron, has been proposed to generate gigawatts-level RF radiation. It uses a modified modulation cavity, in which double-side coupled modulation cavities are biperiodically associated instead of a single-side coupled modulation cavity as in the conventional case. All three feasible resonating modes, i.e., 0, $pi $ /2, and $pi $ modes, generated concurrently at the two different resonant frequencies provided a good field stability against unwanted perturbations. With the input beam current and voltage of ~53 kA and 400 kV, respectively, the proposed biperiodic reltron has predicted ~12-GW RF power generation with ~57% efficiency using particle-in-cell (PIC) simulation.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Experiment of an X-Band High-Efficiency Gyro-TWT Demonstrating
           100-kW 1-Second Long-Pulse Radiations

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      Authors: Peng Hu;Jun Guo;Dimin Sun;Linlin Hu;Qili Huang;Tingting Zhuo;Xu Yao;Yi Jiang;Wenqiang Lei;Luqi Zhang;Rui Song;Zaojin Zeng;Guowu Ma;
      Pages: 2712 - 2718
      Abstract: In this article, the design and test results of an ${X}$ -band high-efficiency long-pulse gyrotron traveling wave tube (gyro-TWT) based on a lossy ceramic-loaded high-frequency (HF) circuit with an operation mode of TE11 are presented. In the design, a pill-box input window, a magnetron injection gun (MIG), a room-temperature coil magnet, and a double-disk output window are adopted. A single-stage depressed collector (SSDC) is applied to enhance the efficiency of this amplifier and to reduce the dissipated beam power. In the hot test, with the beam parameter of 70 kV and 5 A, and the depressed voltage of 20 kV, this ${X}$ -band gyro-TWT produces 104 kW, 1-s long-pulse radiations at 7.8 GHz, corresponding to a saturation gain of 32.2 dB and a maximum overall efficiency of 41.6%, the measured −3-dB power bandwidth exceeds 0.4 GHz.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Preliminary Experiment of Room-Temperature Bitter Magnet for
           Compact Gyrotron

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      Authors: Dun Lu;Wenjie Fu;Meng Han;Chaoyang Zhang;Shijie Hu;Lin He;Yang Yan;
      Pages: 2719 - 2724
      Abstract: Magnetic field system is one of the most crucial components for gyrotron operation. A compact gyrotron with a custom-designed magnet would be a promising continuous radiation source for millimeter-wave power applications. In this article, a design and preliminary experiment of a room-temperature Bitter magnet for developing compact gyrotron are presented. To lengthen the magnetic field homogeneity region without dramatically improving power consumption, a special design that every Bitter segment with different outer radii is adopted. Both in simulation and experimental measurement, the length of the homogeneity region is 120 mm, and homogeneity $Delta {B}/{B}$ is ±0.9% is obtained. A 5 kV magnetron injection gun (MIG) was designed based on the experimental measurement of this Bitter magnet, in which a velocity ratio of 1.3 and transverse velocity spread of 12% were obtained at current 0.5 A in simulation.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Suppression of Circularly Polarized Microwave Dielectric Multipactor by
           Normal Gyromagnetic Field

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      Authors: Huihui Wang;Xianchen Bai;Laqun Liu;Dagang Liu;Lin Meng;
      Pages: 2725 - 2729
      Abstract: This article shows that multipactor on a dielectric window exposed to circularly polarized microwave can be suppressed by a proper normal gyromagnetic field, while a normal gyromagnetic field is traditionally considered to strengthen multipactor in a linearly polarized wave. The dc electric field and the deposited power of multipactor in circularly polarized microwave with normal gyromagnetic field are predicted theoretically and validated by particle-in-cell simulations. The results show that the multipactor threshold ${E}_{{0}}$ is about $pi vert omega +omega _{c} vert ({m}varepsilon _{text {low}}/{(}{8}{e}^{{2}}{)})^{1/2} $ for left-handed circularly polarized waves or $pi vert omega -omega _{c} vert ({m}varepsilon _{text {low}}/{(}{8}{e}^{{2}}{)})^{1/2} $ for right-handed circularly polarized waves, where ${E}_{{0}}$ is the amplitude of RF electric field, $omega $ is the angular frequency of RF electric field, $omega _{c}$ is the cyclotron angular frequency due to the normal magnetic field ${B}$ ( $omega _{c}> 0$ if ${B}$ is pointing to the surface, while $omega _{c} < 0$ if ${B}$ is away from the surface), ${m}$ is the electron mass, ${e}$ is the element charge, and $varepsilon _{text {low}}$ is the first crossover energy in the unit of secondary electron yield.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Novel Folded Rectangular-Grating Slow Wave Structure for Dual-Beam
           Traveling Wave Tube

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      Authors: Peng Gao;Zhigang Lu;Jingrui Duan;Junwan Zhu;Zhanliang Wang;Huarong Gong;Yubin Gong;
      Pages: 2730 - 2737
      Abstract: Increasing the input current is an important method to achieve the high-power output for the traveling wave tubes (TWTs) operating in the ${W}$ -band and higher terahertz (THz) band. For the folded waveguide (FW) TWT, increasing the height of the straight waveguide section of slow wave structure (SWS) can realize a double tunnel to increase the input current, but its electromagnetic characteristics, such as the operating passband, interaction impedance, and ohmic loss, become worse. Thus, a novel SWS, called folded rectangular-grating (FRG), with two tunnels for more input current, was proposed. Its two beam tunnels, where the electromagnetic wave in the operating band is cutoff, are located on the upper and lower edges of the grating, respectively, which makes the FRG-SWS have a wider operating passband, higher interaction impedance, and lower ohmic loss by freely adjusting its grating height. More importantly, its structural complexity is the same as that of FW-SWS. First, the electromagnetic characteristics, including dispersion, interaction impedance, and ohmic loss, are analyzed. Then, the particle-in-cell (PIC) simulation was carried out to verify that the saturated power, gain, and electron efficiency of TWT using FRG-SWS have been significantly improved compared with the TWT using FW-SWS. In the end, the cold test of transmission characteristics for FRG-SWS was done, and the experimental results are basically in good agreement with the simulation ones when the conductivity is set as $2.25times 10^{{7}}$ S/m.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Staggered-Vane Traveling-Wave Tube (SVTWT) Amplifier for High-Power V-Band
           Applications: Design, Fabrication, and Test

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      Authors: Young-Min Shin;B. Stockwell;R. Begum;A. Moyer;K. Childs;C. Nilsen;L. Roeder;M. Cusick;P. Kolda;T. Grant;
      Pages: 2738 - 2745
      Abstract: As a part of the plan to deploy a wideband high-power module (HPM) to very high-throughput satellite (VHTS) network systems, Communications and Power Industries LLC (CPI) has been developing a ${V}$ -band high-power traveling-wave tube (TWT) amplifier. The power amplifier is designed with a staggered-vane TWT (SVTWT) circuit and a circular beam, operating at beam voltage ( ${E}_{k}{)} =18$ –20 kV and beam current ( ${I}_{k}{)} =400$ –500 mA with the perveance of $0.168 mu text{P}$ . Within the development program, three prototypes have been built and tested so far—the first two prototypes only include simple features in their circuit configuration, excluding servers and complex tuning elements. The signal amplification process in the novel beam–wave scheme was demonstrated with the first prototype, showing 35 dBm of output power ( ${P}_{text {out}}{)}$ with 10–15 dB of small-signal gain and 4 GHz of 1-dB bandwidth (47.2–51.2 GHz). ${P}_{text {out}} =57$ dBm (500 W) and 24 dB of small-signal gain (SSG) were demonstrated over 4.2 GHz (47.2–51.4 GHz) of 1-dB bandwidth with the second prototype. During the RF test, the tube operated at the continuous wave (CW) mode (100% of duty cycle) with extra external cooling fans. The third prototype is designed with more complex features, including servers, mode anode, and multistage depressed collector (MDC). Its test results showed ${P}_{text {out}} =54$ dBm (250 W) and 24 dB of SSG over 5.2 GHz (47.2–52.4 GHz) of 1-dB bandwidth, running at CW mode with extra external cooling fans.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Modified Double Staggered Grating Waveguide Slow Wave Structure for
           Sub-THz Traveling Wave Tubes

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      Authors: Chen Zhao;Hang Xu;
      Pages: 2746 - 2752
      Abstract: A modified double staggered grating waveguide (DSGW) slow wave structure (SWS) is proposed for millimeter-wave and sub-THz traveling wave tubes (TWTs). Gratings with a cross Section outline of exponential curves are applied instead of the traditional rectangular cross section. The proposed SWS owns a higher interaction impedance compared to DSGW, resulting in higher output power and gain. With proper design and optimization of the input–output couplers, the proposed SWS can have a wide −15 dB impedance bandwidth, extending from 192 to 230 GHz. Particle-in-cell (PIC) simulations are carried out for a TWT with sheet electron beam (SEB) and the main SWS having 70 periods. Such a TWT provides a maximum power of 116.64 W which indicates a significant improvement compared with the traditional DSGW.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Experimental Demonstration of a Circular Beam Electron Gun and
           a PPM System for D-Band TWTs

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      Authors: Zugen Guo;Ruifeng Zhang;Han Lai;Feng Lan;Zhanliang Wang;Zhigang Lu;Zhaoyun Duan;Yubin Gong;Huarong Gong;
      Pages: 2753 - 2759
      Abstract: In this article, we present a design scheme of an electron-optical system (EOS) for terahertz vacuum electron amplifiers. The performance characteristics are studied by simulation, and the feasibility is verified by transmission experiment. Based on the Pierce design method, an electron gun with an isolated beam focus electrode (BFE) is designed, which has been simulated and confirmed by CST particle tracking solver and OPERA charged particle solver. A periodic permanent magnet (PPM) system including dual D-magnets of RF signal coupling port is utilized for focusing beam transportation in the 0.15-mm-radius tunnel. The experimental results of the magnetic field are in good agreement with the simulation results. The simulation results show that the beam-focusing system with the axial peak magnetic field of 5.2 kGs can confine the electron beam within the beam tunnel. Additionally, the EOS is successfully developed and used in the ${D}$ -band folded waveguide traveling-wave tube (TWT). The experimental results of electron transmission show that the thermionic cathode with a cathode load of 5 A/cm2 can provide a beam current of 56 mA, and 90% beam current is transmitted through the beam tunnel to the collector.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • The Effects of Electron Cyclotron Absorption in Powerful Narrow-Band
           Sub-THz Oscillators Exploiting Volume and Surface Modes

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      Authors: A. J. MacLachlan;C. W. Robertson;Adrian W. Cross;A. D. R. Phelps;
      Pages: 2760 - 2766
      Abstract: We present the theory, design, and numerical modeling of novel, pulsed sub-THz oscillators based on cylindrical, 2-D periodic surface lattice (PSL) interaction cavities. Investigation of the electronic efficiency and power dependence on the magnitude of the magnetic guide field and the electron beam current is investigated. While cyclotron absorption effects have been studied in low-order, 1-D backward wave oscillators (BWOs), few studies have considered cyclotron absorption in highly overmoded, 2D-PSL oscillators. Here we investigate certain behavior associated with cyclotron absorption in 2D-PSL devices with over 400 modes. This electron cyclotron absorption is shown to be a universal process, independent of frequency and transverse cavity size. Dispersive behavior shows minimal group velocity at the point of interaction and demonstrates similarities with degenerate band edge (DBE) phenomena. In this work, the fundamental mode selection mechanism relies on the coupling of high-order volume and surface waves. Good agreement between theory and modeling is presented.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Novel Design of G-Band Broadband Low-Gain Fluctuation Slow-Wave
           Structure With Improved Folded Waveguides

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      Authors: Yuan Feng;Pan Pan;Changqing Zhang;Hanwen Tian;Jinjun Feng;
      Pages: 2767 - 2772
      Abstract: The design method for ultrawideband amplification with low-gain fluctuation is explored for the terahertz folded-waveguide traveling-wave tube (TWT). Although the folded-waveguide circuit has a large cold bandwidth (~30%), effective amplification with a flat gain characteristic can only be achieved in a limited range due to sharply reduced interaction impedance. The situation further deteriorates in the design of a terahertz TWT where an oversized beam tunnel has to be used to facilitate the transport of the beam. Through careful analysis of the folded-waveguide (FWG) design characteristics, a modification to the geometry of the circuit has been proposed, leading to a significant enhancement in design capability. As a result, the interaction impedance is increased by 26% over a wide operation frequency band in comparison to the normal folded-waveguide circuit. This makes it possible to use the phase velocity tapering technology to increase efficiency and balance the gain at the same time. A design example in G-band is presented. The interaction circuit is capable of producing 18-W output power over 30 GHz from 202 to 232 GHz with a gain fluctuation of less than 1.5 dB.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Fabrication of E-Band Traveling Wave Tube for High Data Rate
           Wireless Links

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      Authors: Claudio Paoloni;Rupa Basu;Purushothaman Narasimhan;Jonathan Gates;Rosa Letizia;
      Pages: 2773 - 2779
      Abstract: ${E}$ -band (71–76 and 81–86 GHz) is widely used for wireless point to point (PtP) links with a few gigabit/second data rate. ${E}$ -band front ends are powered by solid-state amplifiers with about 1-W output power per module. This level of output power limits range and spectral efficiency in rain condition and has to be compensated by high gain antennas or backup low-frequency links with reduced capacity. The availability of tens of watts of transmission power would allows higher spectral efficiency and long range, and the use of lower gain antennas for multibeam and area coverage. Millimeter wave traveling wave tubes (TWTs) are gaining interest due to their higher power, more than one order of magnitude, in comparison with solid-state devices. Helix TWTs, typically built at microwaves, are very arduous to fabricate due to the extremely small diameter of a helix at ${E}$ -band. This article reports the design and fabrication of the first ever ${E}$ -band TWT based on a full metal slow wave structure (SWS), the double corrugated waveguide (DCW). The TWT is designed to provide about 70-W power and more than 35-dB gain in the 71–76-GHz band. A test TWT using a single Section interaction structure is in the final assembly phase as proof of concept with about 2-W output power. The ${E}$ -band TWT performance will open new perspectives in the availability of long range wireless links with multi-Gb/s data rate needed for enabling 5G and 6G new networks.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Novel 2-D Slotted Structure Extended Interaction Oscillator

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      Authors: Jielong Li;Diwei Liu;Ruizhe Ren;Chuanhong Xiao;Zongjun Shi;Tao Zhao;Min Hu;Yanyu Wei;Zhaoyun Duan;Yubin Gong;Zhenhua Wu;
      Pages: 2780 - 2785
      Abstract: Numerous vacuum electronic devices (VEDs) have been widely studied, among which extended interaction oscillators (EIO) exhibit appealing characteristics, such as high frequency, high efficiency, lightweight, low working voltage, and stable working frequency. The slow wave structure typically adopts the coupled-cavity, folded-waveguide, ladder line, and other structures. The ladder line has a simple structure and is easy to process, with desirable heat dissipation and large power capacity. In this study, a novel slow wave structure being longitudinally slotted in the transverse grating of the original ladder line is proposed, and the 2-D slotted structure can be obtained. Encouragingly, the structure not only increases the cross-sectional area of the electron beam but also, more importantly, increases the effective interaction area to considerably improve the output power. The dispersion characteristics and field distribution are first studied through numerical and simulation calculations, and the optimal slotted structure parameters and working parameters are analyzed using PIC software. Next, a 94-GHz 2-D slotted structure EIO is designed. Finally, compared with the ladder line, the cavity characteristic impedance ${R}/{Q}$ is increased by 52.5%, and the output power is increased by 21.1%. This novel structure is expected to provide a new idea for the power enhancement of millimeter-wave and terahertz EIOs.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Modified Fold Waveguide Slow Wave Structure for W-Band
           Dual-Beam TWT

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      Authors: Jingrui Duan;Zhigang Lu;Junwan Zhu;Zhanliang Wang;Shaomeng Wang;Huarong Gong;Yubin Gong;
      Pages: 2786 - 2791
      Abstract: Increasing the interaction current capacity and the interaction impedance is crucial to achieving high output power for traveling wave tubes (TWTs) in ${W}$ -band and terahertz (THz)-band. With the increased distance between the upper and lower metal walls of folded waveguide (FW), the slow wave structure (SWS) named dual-tunnel FW (DTFW) is formed. Benefiting from such a rational design, the electric field in the noninteracting region decreased and naturally formed dual electron beam tunnels. Meanwhile, the operating mode is cutoff at the beam tunnel, the electromagnetic wave in DTFW can be propagated along the path similar to FW and operate in the fundamental mode. Furthermore, compared with FW, due to its larger size, the DTFW has the same structural complexity and less manufacturing difficulty, which is significant for ${W}$ -band and THz-band. In this article, through the analysis of the high-frequency characteristics of the SWS using FW and DTFW, the physical mechanism of bandwidth and interaction impedance improvement of DTFW-SWS are revealed. Moreover, the particle-in-cell (PIC) simulation results reveal that, compared with a TWT using unprecedentedly excellent FW-SWS, the performance of TWT using DTFW-SWS has been significantly further improved in the aspects of saturated power, gain, and electron efficiency. Therefore, DTFW-SWS is a promising SWS for high-power and wide-bandwidth TWT in ${W}$ -band and THz-band.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • The Research on the High-Current-Density Shielded Sheet Electron Beam
           Matching Focusing Magnetic Field

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      Authors: Pengcheng Yin;Jin Xu;Jinchi Cai;Yanyu Wei;
      Pages: 2792 - 2797
      Abstract: Increasing beam current density is a very effective approach to boost the output power in millimeter wave and terahertz vacuum devices. However, the current density of sheet electron beam (SEB) is severely limited, due to instabilities in the SEB transport, especially in the case of high current density. To overcome this limitation, a new approach for stably transporting a high-current-density SEB, named shielded SEB matching focusing magnetic field (shielded SEB-MFM), is presented in this article. This new focusing magnetic field consists of a small transverse magnetic field and a conventional shielded uniform magnetic field (shielded UM). Compared with the conventional shielded UM, about double the maximum beam current density can be transported by the shielded SEB-MFM, in the same strength as the magnetic field. In addition, an implementable scheme of an electron optical system based on the shielded SEB-MFM is designed and calculated to verify the feasibility of the shielded SEB-MFM. The results indicate that the SEB with a 636-A/cm2 current density can be well focused by a 0.8-T shielded SEB-MFM in a 40-mm tunnel. To achieve the same expansion degree of thickness, the conventional shielded UM must be around 1.5 T.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Demonstration of a PCM-Focused Sheet Beam TWT Amplifier at
           G-Band

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      Authors: Changqing Zhang;Pan Pan;Jun Cai;Xueliang Chen;Hanwen Tian;Siming Su;Kangcheng Zhou;Weisi Meng;Ying Li;Bowen Song;Yubin Gong;Jinjun Feng;
      Pages: 2798 - 2803
      Abstract: A sheet beam traveling-wave tube (TWT) amplifier focused by periodically cusped-magnetic (PCM) fields has been successfully developed. The amplifier produces ~115 W of peak power at 212.4 GHz with a voltage of 25.8 kV. The output power is more than 100 W from 210.2 to 213.6 GHz. The measured transport current is about 106 mA accounting for 81.5% of the total current. The high-efficiency circuit design, along with the novel coupling structure, makes it possible to greatly reduce the required current, enabling the use of the PCM focusing. As a result, large power and a wide band have been achieved in a compact volume with an overall weight of less than 1.8 kg. The results demonstrate a significant breakthrough in developing the sheet-beam amplifier at terahertz frequencies. Although a single-section circuit without the attenuator is used at this stage, we have verified all the key technologies. The measured results are in good agreement with the design.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Theoretical Study of a Novel G-Band Sheet Beam Slots-Loaded Coupled-Cavity
           Traveling Wave Tube

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      Authors: Hanwen Tian;Changqing Zhang;Jun Cai;Pan Pan;Jinjun Feng;
      Pages: 2804 - 2809
      Abstract: In this article, the design of a novel symmetrical double slots coupled-cavity (SDSCC) traveling wave tube (TWT) operating in ${G}$ -band is presented. The novel slow wave structure (SWS) suits sheet electron beam and has a large sheet beam channel and high coupling impedance. The novel structure shows great potential in high-power terahertz amplifier field. The dispersion characteristics are studied by both theory and simulation. An equivalent circuit of SDSCC SWS is built. The coupling impedance and electric field of operating mode are simulated. A suitable input–output structure is designed for this novel SWS. The transition characteristics are exhibited. The beam-wave interaction process is also simulated. The peak output power arrives at 384 W at 218 GHz by the usage of a sheet beam with 26.2 kV and 300 mA. The average dc current density in the sheet beam tunnel is around 160 A/cm2. The spectrum of the output signal is pure, and the risk of mode competition is very low.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Electron Beam Third Harmonic Amplification Generates High-Power Tunable
           Terahertz Radiation

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      Authors: Shaojie Chang;Zhenhua Wu;Diwei Liu;Renbin Zhong;Zhaoyun Duan;Yanyu Wei;Yubin Gong;Min Hu;
      Pages: 2810 - 2813
      Abstract: A novel approach to extract and amplify the third harmonic of electron beam to generate high-power terahertz radiation is presented. Three planar grating structures operating in the backwave region are used for the extraction and amplification of the electron beam from the fundamental modulation, the fundamental amplification, and the third harmonic. This results in an amplified output of the fundamental wave and a high power output of the fundamental triplet frequency. The planar grating structure is easier to machine and assemble than conventional harmonic amplifiers and increases the flow rate of the electron beam. Calculations show that with an input signal of 119.5–120.6 GHz at 80 mW and a 35-A/cm2 electron beam in adjustment from 27.5 to 29.3 keV, the structure has an output signal of hundreds of milliwatts in the range of 358.5–361.8 GHz, with a power output of 583.2 mW at the central frequency point of 360 GHz. The harmonic signal is output while a watt-level fundamental signal can be output.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Analysis of a 0.33-THz Sine-Shaped Folded Waveguide Traveling
           Wave Tube

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      Authors: Jinjing Luo;Jin Xu;Pengcheng Yin;Jian Zhang;Dongdong Jia;Wuyang Fan;Yue Ouyang;Lingna Yue;Jinchi Cai;Hairong Yin;Gangxiong Wu;Zhanliang Wang;Yubin Gong;Yanyu Wei;
      Pages: 2814 - 2820
      Abstract: Folded waveguide (FWG) traveling wave tube (TWT) is an attractive choice for a high-power amplifier. This article proposes a novel slow wave structure (SWS) called sine-shaped FWG (S-FWG), which is derived from conventional FWG. With the feature of transforming the arc-shaped segment of the traditional FWG into the sinusoidal waveguide, the proposed structure could be quickly optimized by modifying the amplitude of the two sine curves, and it has an ability to produce a greater interaction impedance compared to the traditional FWG SWS with the same frequency band, which, under the same operating conditions, is expected to result in a higher output power. Using CST Microwave Studio, the high-frequency properties and beam–wave interaction were simulated. Simulation results indicate that the S-FWG TWT reaches a maximum output power of 16.82 W and a gain of 32.25 dB at 330 GHz with an operating voltage of 19.4 kV, a beam current of 30 mA, and an input power of 10 mW. The S-FWG SWS should therefore be regarded as a promising SWS for the high-power terahertz (THz) traveling wave amplifier.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Metamaterial-Based Novel S-Band Coaxial Slow Wave
           Structure

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      Authors: Rajnish Kumar;Mohit Kumar Singh;Manpuran Mahto;Pradip Kumar Jain;
      Pages: 2821 - 2827
      Abstract: In this article, a novel ${S}$ -band metamaterial-based coaxial slow wave structure (MCSWS) is proposed for high-power microwave (HPM) applications. The electromagnetic features of the proposed MCSWS and conventional coaxial slow wave structure (CCSWS) are investigated. The dispersion curve and coupling impedance of the two models have been compared to ascertain the advantages of MCSWS over CCSWS. For the same structural dimensions, the $pi $ mode resonant frequency of the fundamental mode (TM00) of MCSWS is 2.49 GHz, whereas it is 3.82 GHz for the CCSWS. The coupling impedance of the MCSWS at its resonant frequency is $sim 2000~Omega $ , while it is $sim 115~Omega $ for the CCSWS. Furthermore, the transmission characteristics of the fabricated MCSWS have been measured with the help of Anritsu MS2037C VNA Master. The measured reflection coefficient confirms the operation of MCSWS at 2.48 GHz. Moreover, a magnetically insulated line oscillator (MILO) configured using the proposed MCSWS has been investigated in the presence of electron beams to predict its RF performance. The particle-in-cell simulation predicted an output power of 6 GW at a frequency of 2.4 GHz with a power conversion efficiency of 21%.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Ka-Band Low-Voltage Multiple-Beam Mini-TWT

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      Authors: Colin D. Joye;Alexander N. Vlasov;Reginald Jaynes;Igor A. Chernyavskiy;Khanh T. Nguyen;John Pasour;John C. Rodgers;Franklin N. Wood;Vadim Jabotinski;Thomas M. Antonsen;Simon J. Cooke;Alan M. Cook;Baruch Levush;
      Pages: 2828 - 2833
      Abstract: We describe the design, development, and initial testing of a very compact, multiple-beam folded-waveguide traveling wave tube (TWT) operating in Ka -band at $sim $ 6 kV. A proof-of-principle four-beam, $sim $ 100 mA/beam device has been fabricated and tested, and a 16-beam version of the device has been designed and is predicted to produce an output power up to 1 kW. Here, we describe the design approach we devised and implemented to overcome two fundamental challenges: 1) generating and transporting the tightly spaced beams required to operate in the millimeter-wave regime and 2) developing folded waveguide circuits that can provide high interaction impedance for each of the beams as well as stable operation in a dense high-order-mode environment.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Quasi-Optical Mode Converter Based on All-Dielectric Metamaterial for
           High-Order Mode Vacuum Electronics Devices

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      Authors: Meng Han;Wenjie Fu;Dun Lu;Chaoyang Zhang;Shijie Hu;Yang Yan;
      Pages: 2834 - 2839
      Abstract: All-dielectric metamaterials (ADMs) have recently attracted much attention due to their ability to achieve wavefront control with high power capability. In this article, an investigation on quasi-optical mode converter (QOC) based on ADM for high-order vacuum electronics devices (VEDs) is presented. Specifically, four ADM QOCs are designed to convert the cylindrical waveguide TE01, TE21, TE31, and TM01 modes into linear polarized Gaussian beams at 35 GHz. Electromagnetic simulations show that the Gaussian mode contents of the output waves from four mode converters are all over 94% with high polarization contents. Furthermore, a Ka-band ADM mode converter with the input mode of circular waveguide TE01 mode is fabricated and measured. Experimental results show that the output fields with scalar Gaussian content over 90% can be obtained at 30–38.85 GHz, corresponding to a relative bandwidth of 25.3% around 35 GHz. The maximum scalar Gaussian mode content of 99.18% is observed at 34.56 GHz in the experiment. The investigation opens new avenues toward high-order mode conversion technology based on ADM.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Performance Improvement of Helix Traveling- Wave Tubes Based on
           Multiobjective Optimization Technique

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      Authors: Wen-Kai Deng;Yu-Lu Hu;Gu-Bin Li;Zhong-Hai Yang;Bin Li;Tao Huang;
      Pages: 2840 - 2845
      Abstract: An optimization design tool for helix traveling-wave tubes (TWTs) is developed by combining the nondominated sorting genetic algorithm II (NSGA-II) and the beam–wave interaction simulator (BWIS), which can realize multiobjective optimization of various TWT figures of merit (FoMs). FoMs include the output power, gain, efficiency, and nonlinear distortion characteristics. This optimization design tool can automatically construct a Pareto-optimal solution set according to FoMs. Then, the final simulation design can be obtained by analyzing the output power variation over the operating band of the individuals in the optimized solution set. In order to ensure the comprehensiveness and accuracy of FoMs, a workflow is established in the optimization tool, which can simulate the physical process by transferring the data between different computing tasks automatically during the design of beam–wave interaction. Based on this design tool, the performance of an L-band helix TWT has been improved significantly. For the demonstrated interaction, the output power, phase distortion, interaction, and recovery efficiency are taken as objectives. After analyzing the output power variation over the operating band, the final parameter set is determined from the Pareto-optimal solution set.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A 0.34-THz Quasi-Optical Resonant Cavity-Based Klystron Amplifier

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      Authors: Jingyu Guo;Yang Dong;Xianzhu Liu;Ping Zhang;Shaomeng Wang;Zhanliang Wang;Huarong Gong;Zhigang Lu;Zhaoyun Duan;Yubin Gong;
      Pages: 2846 - 2851
      Abstract: A klystron amplifier based on Smith–Purcell (SP) radiation and the quasi-optical resonator cavity (QORC) is proposed for terahertz (THz) waves. Benefits from high interaction impedance and simple grating structure of QORC, the proposed klystron amplifier can operate at a low voltage and can achieve a high gain. The verification of the novel concept amplifier is carried out successfully by the particle-in-cell (PIC) simulations of a 0.34-THz klystron amplifier using three QORCs. The results show that with the voltage of 11.5 kV and a current of 70 mA, the klystron amplifier obtains an output power of 11.78 W for an input power of 8 mW, corresponding the gain of 31.7 dB. Besides, in the case of reduced period length of grating, QORC klystron amplifier can operate with the same cavity mode at lower dc power, and the saturated input power is significantly reduced, but the output performance is weakened. The grating of 0.34-THz QORC is fabricated by using computer numerical control (CNC) milling, showing the maximum fabrication deviation of thickness of grating facet less than $5~mu text{m}$ , which proves the fabrication feasibility of the 0.34-THz QORC klystron amplifier.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A 10-kW Output Power Ka- to W-Band Klystron Harmonic Generator

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      Authors: Sayed Mohsen Razavi;Emad Hamidi;Sayed Mohammad Javad Razavi;
      Pages: 2852 - 2859
      Abstract: The growing interest in high-power millimeter (mm)-wave amplifiers for various applications, such as high-resolution radar, active mm-wave imaging and atmospheric sensing, near object analysis, and 5G communications leading to novel solutions through which the researchers can overcome difficulty, complexity, and high expenses involved in fabrication technology of conventional vacuum electron devices including gyrotron, klystron, and traveling wave tube at ${W}$ -band frequency. Ka -band to ${W}$ -band klystron harmonics generator (KHG) can be an ideal solution to overcome these challenges. This article presents the design and simulation of a Ka -band to ${W}$ -band KHG, which triples input frequency and amplifies third harmonics. In the design of the beam–wave interaction region, two methods, including the Friedlander method and the core oscillation method, have been used. In the output cavity, TM130 higher mode was applied. Using high-order mode increases the dimensions of the output cavity and decreases mechanical complexity and cost. The results gained from simulation in particle-in-cell computer simulation technology (CST) solver showed that the output power could reach higher than 10.7 kW with 53-dB gain and 24% beam efficiency in TM310 output cavity mode. The electron beam voltage is 45 kV with a 1-A beam current.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Grating Optimization for Smith–Purcell Radiation: Direct Correlation
           Between Spatial Growth Rate and Starting Current

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      Authors: Md Arifuzzaman Faisal;Peng Zhang;
      Pages: 2860 - 2863
      Abstract: Smith–Purcell radiation (SPR) is generated when electrons travel close to a metallic periodic grating. It was found that the starting current of SPR varies by orders of magnitude by simply varying the grating parameters (groove’s heights and widths) while keeping the grating period and the electron beam properties fixed. In this article, we demonstrate that this strong dependence of starting current on the grating parameters is directly related to the spatial growth rate of the SPR. Using the hot-tube dispersion relation, we optimize the grating parameters to minimize the starting current to excite coherent SPR.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Thermionic Emission Characterization of M-Type Cathodes Using Kelvin Probe
           in an Ultra-High Vacuum Environment

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      Authors: Antonio M. Mantica;Michael J. Detisch;T. John Balk;
      Pages: 2864 - 2871
      Abstract: Thermionic emission characterization is vital for understanding the performance and lifetime of the many vacuum electron devices (VEDs) that make use of cathodes. To characterize the performance of thermionically emitting cathode surfaces with efficiency in one test setup, the Cathode Characterization Chamber (C3) has been assembled at the University of Kentucky. The C3 principally monitors the work function change and the current density emitted by thermionic surfaces using a Kelvin probe in an ultra-high vacuum (UHV) chamber (approaching $10^{-{10}}$ torr). The chamber also employs ion polishing, optical pyrometry, and residual gas analysis to produce a single comprehensive cathode characterization apparatus. One widely used cathode in VEDs is the M-type cathode, developed in the mid-1960s. M-type cathodes are useful because of their relatively high current densities of emission (< 10 A/cm2) at only moderately high activation temperatures ( $< 1100 ^{circ }text{C}$ ) for tens of thousands of hours. Using the M-type cathode as a “standard candle,” the capabilities and limits of the C3 are highlighted here and the results are compared to those from pure tungsten samples—all of which are presented as a powerful and comprehensive tool for thermionic emission characterization.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Miniaturized Ionization Vacuum Sensor Based on Thermionic Electron
           Emission From Carbon Nanotubes

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      Authors: Yuwei Wang;Yidan He;Shuyu Mao;Zhenzheng Zhao;Wei Yang;Peng Liu;Xianlong Wei;
      Pages: 2872 - 2875
      Abstract: Traditional hot-cathode ionization vacuum sensor (IVS) has long suffered from bulky size and integration difficulties. Here, to overcome these problems, a hot-cathode IVS is scaled down to nail size by utilizing micro-electromechanical system (MEMS) technology and exploiting carbon nanotubes (CNTs) as microscale filaments for the first time. Silicon-based grid and ion collector are bonded vertically on the hot-cathode chip to form a compact and scalable MEMS-type device with dimensions of $13times 9times2.7$ mm. The ratio of ion current ( ${I}_{i}$ ) to emission current ( ${I}_{e}$ ) shows measurement linearity from 0.05 to 6.50 Pa. Also, benefiting from the good reproducibility of the CNT thermionic electron emission, a minor variation (< 10%) is observed when the vacuum level is toggled repeatedly between 0.02 and 1.00 Pa. All these features make our miniaturized hot-cathode IVS a promising device for vacuum detection.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Observation of Ultrathin Sc-Containing Surface Layer on Life-Tested
           Scandate Cathodes

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      Authors: Xiaotao Liu;Bernard K. Vancil;Daniel B. Durham;D. Frank Ogletree;Edward S. Barnard;T. John Balk;
      Pages: 2876 - 2882
      Abstract: To explain enhanced levels of electron emission from scandate cathodes, models invoking surface layers ( $sim $ 100 nm thick) of Ba-Sc-O, or alternatively a Ba-Sc-O monolayer, have been frequently employed to describe the lowered work function that is thought to lead to these improved emission capabilities. However, limited direct experimental proof has been provided, primarily involving Auger electron spectroscopy (AES) for depth profile analyses of elemental composition. In this article, we report direct observations of an Sc-containing surface layer on scandate cathodes, as indicated by independent, complementary measurements using scanning nanobeam AES and electron energy loss spectroscopy (EELS) techniques. The ultrathin Sc-containing layer on these cathodes is no more than 3–4 nm thick and is likely even thinner than this. The surface layer may consist of amorphous or nanoscale polycrystalline materials, as suggested by scanning nanobeam electron diffraction and analytical mapping.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Investigation of a La2Hf2O7 Direct-Heated
           Long Lifetime Cathode

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      Authors: Xingqi Wang;Xiaoxia Wang;Jirun Luo;Shikai Qi;Yun Li;
      Pages: 2883 - 2889
      Abstract: In order to prolong the service life and high-temperature stability of direct-heated cathode, a novel cathode is proposed and prepared, in which La2O3, Gd2O3, and HfO2 are used as raw materials for the first time. The X-ray diffraction (XRD) structure characterization shows that emission material consists of La2O3 and La2Hf2O7 two compounds. The thermionic emission results indicate that this kind cathode can supply a current density of about 5.5 A/cm2 at 1600 °C. The energy dispersive spectroscopy (EDS) detection manifests the emission material distributes homogeneously around the W–Re base. The cathode has been working stably for 10 920 h without obvious fall at 1550 °C with the loading of 0.65 A/cm2 in life test process.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Current Loss Mechanism of Magnetic Insulation Transmission Line With
           Helical Inductance Support

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      Authors: Pengfei Zhang;Aici Qiu;Hailiang Yang;Jiahui Yin;Yang Hu;Jiang Sun;Yongdong Li;Wei Luo;Peitian Cong;
      Pages: 2890 - 2896
      Abstract: Accurate adjustment of long magnetic insulation transmission lines (MITLs) is crucial in high-power pulsed systems, which must guarantee insulation and high transmission efficiency of current under complicated electromagnetic environment. In this study, a spiral inductance-supported insulation structure in a coaxial MITL was designed, which achieved high efficiency of current transmission up to 90%. Moreover, the current transmission efficiency of the MITL under various working states and specific mechanism of the current loss was investigated by combining circuit with particle-in-cell (PIC) simulations. Results show that the current loss of the inductance-supported MITL in the under-matched state is caused by the inductance current on the support structure, as the electron charge layer is strongly constrained by magnetic field. However, the charge constraint among MITL electrodes is relatively weak in self-limited flow. The electrons bombard the supporting rod, which results in charge accumulation and unneglectable current loss in self-limited flow. This work uncovers the mechanism of current loss in the spiral inductance-supported MITL, which provides guidance for engineering design.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Investigation on Multipactor in Double-Sided Dielectric-Loaded Microwave
           Components

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      Authors: Yonggui Zhai;Hongguang Wang;Meng Cao;Shu Lin;Min Peng;Yun Li;Wanzhao Cui;Yongdong Li;Rui Wang;
      Pages: 2897 - 2904
      Abstract: This article presents a study of the multipactor effect in a double-sided dielectric-loaded parallel-plate waveguide. To this end, a 1-D electrostatic particle-in-cell model is established, which considers the radio frequency electric fields, space charge fields, and surface charge fields generated by the accumulated charge on the dielectric surface. The dynamic evolution of multipactor breakdown for different operating voltages and dielectric materials with different secondary electron yield (SEY) properties is investigated by numerical calculation. The results obtained show that multipactor does occur self-extinguishing phenomenon due to the presence of the surface charge fields under certain circumstances in the double-sided dielectric-loaded parallel-plate waveguide. Moreover, a comparative study of multipactor between metal, single-sided, and double-sided dielectric-loaded parallel-plate waveguides is carried out. The simulation results show that the self-extinguishing time of the multipactor in the double-sided dielectric-loaded model is less than that in the single-sided dielectric-loaded model. Finally, a multipactor susceptibility diagram for the SEY curve of different bottom dielectric materials in the parallel-plate waveguide is constructed. The results show that the single-sided dielectric-loaded microwave components are more beneficial to suppress the multipactor effect. The results reported in this study can be used to guide the design of space high-power microwave components.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Enhancement of Silicon Critical Breakdown Field by Reducing the Avalanche
           Breakdown Distance to Improve the Breakdown Voltage of Thin SOI Device

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      Authors: Yulong Wang;Baoxing Duan;Yintang Yang;
      Pages: 2905 - 2910
      Abstract: This article presents an analytical model for a thin silicon-on-insulator (SOI) device based on the enhancement of silicon critical breakdown field technology. Solving the 2-D Poisson equation in the thin drift region reasonably explains the physical mechanism that the thin silicon layer enhances the critical breakdown field of silicon material. Meanwhile, a new ultrathin SOI lateral double diffused metal oxide semiconductor field effect transistor with electron accumulation layer is proposed, named EA SOI LDMOS, to verify the proposed model and improve the tradeoff between breakdown voltage (BV) and specific ON-resistance ( ${R}_{text {on,sp}}{)}$ . The electron accumulation provides a new conduction path under the gate oxide layer, resulting in a lower resistance compared with conventional thin SOI LDMOS. The various thickness of the thin silicon layer enhances the critical breakdown field of silicon, which increases the BV of EA SOI LDMOS. The results show that the ${R}_{text {on,sp}}$ of EA SOI LDMOS is decreased from 303 $text{m}Omega cdot $ cm2 of the conventional ultrathin SOI LDMOS to 207 $text{m}Omega cdot $ cm2, which is 32% lower with the same BV. The analytical results of the electrical characteristics are in good agreement with the results from numerical simulations.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Compact Model of a Bulk FinFET Quantum Dot Toward Single Chip Integration
           of Qubits and Control Electronics for Quantum Computing Applications

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      Authors: Sujit Kumar Singh;Deepesh Sharma;Reinaldo A. Vega;Abhisek Dixit;
      Pages: 2911 - 2918
      Abstract: In this work, we thoroughly investigate the drain current oscillations induced by quantum confinement in short channel bulk FinFETs, while operating in coulomb blockade (CB) regime at cryogenic temperature. Various device geometries and layouts of narrow fin-based FinFETs are analyzed experimentally to comprehend the development of quantum dots (QDs). The results demonstrate that the size of QD in the channel is crucial in defining the sensitivity of confinement-related parameters to modifications in device design. To capture the gate and drain bias dependence associated with drain current oscillations in CB regime, we have proposed analytical equations to augment the existing BSIM-CMG compact model. Model-hardware correlation is also presented for n- and p-type bulk FinFETs with different device geometries. The proposed model marks the initial steps toward developing a unified compact model that accurately captures both: the classical behavior of bulk FinFETs and its QD-based tunneling behavior at cryogenic temperatures.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Study of Impact Ionization Coefficients in Silicon With Low Gain Avalanche
           Diodes

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      Authors: Esteban Currás Rivera;Michael Moll;
      Pages: 2919 - 2926
      Abstract: Impact ionization in silicon devices has been extensively studied and several models for a quantitative description of the impact ionization coefficients have been proposed. We evaluate those models against gain measurements on low-gain avalanche diodes (LGADs) and derive new parameterizations for the impact ionization coefficients optimized to describe a large set of experimental data. We present pulsed infrared (IR)-laser-based gain measurements on five different types of $50 boldsymbol {mu }text{m}$ -thick LGADs from two different producers centro nacional de microelectrónica (CNM) and Hamamatsu Photonics (HPK) performed in a temperature range from $- 15,,{^{circ} }text{C}$ to $40 {^{circ} }text{C}$ . Detailed technology computer-aided design (TCAD) device models are conceived based on secondary ion mass spectrometry (SIMS) doping profile measurements and tuning of the device models to measure ${C}$ – ${V}$ characteristics. Electric field profiles are extracted from the TCAD simulations and used as input to an optimization procedure (least squares fit) of the impact ionization model parameters to the experimental data. It is demonstrated that the new parameterizations give a good agreement between all measured data and TCAD simulations which is not achieved with the existing models. Finally, we provide an error analysis and compare the obtained values for the electron and hole impact ionization coefficients against existing models.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Tunnel Field-Effect Transistor Triggered Silicon-Controlled Rectifier

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      Authors: Zhaonian Yang;Jinghao Xu;Shi Pu;Panqi Gao;Yue Zhang;Yuan Yang;Yan Zhang;
      Pages: 2927 - 2933
      Abstract: In this article, a tunnel field-effect transistor (TFET) triggered silicon-controlled rectifier (SCR) device is proposed. A TFET is embedded into the SCR enabling an early carrier’s transportation through the n-well/p-well reverse-biased junction. This accelerates the junction breakdown and helps to establish the SCR’s positive feedback regeneration. The applications of the TFET-triggered SCR (TTSCR) in electrostatic discharge (ESD) protection are explored and the electrical characteristics are investigated. Moreover, the impact of the device structure on the device performance is discussed. The principle of the proposed device is verified using technology computer-aided design (TCAD) simulation. The simulation results show that compared to the prevalent diode-triggered SCR, the proposed device has a small layout area, a low leakage current, and a low overshoot voltage.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Electro-Thermal Characteristics of Junctionless Nanowire Gate-All-Around
           Transistors Using Compact Thermal Conductivity Model

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      Authors: Nitish Kumar;Sushil Kumar;Pragyey Kumar Kaushik;Ankur Gupta;Pushpapraj Singh;
      Pages: 2934 - 2940
      Abstract: The electrothermal performance of a junctionless nanowire [JL-nanowire (NW)] gate-all-around (GAA) transistors under self-heating effect (SHE) is examined for sub-5 nm technology nodes. These devices are generally fabricated on silicon-on-insulator (SOI) wafers, in which the thin active device layer confines silicon thermal conductivity ( $kappa {)}$ and provokes SHE in the device. In this work, we proposed and upgraded the early reported compact thermal conductivity model (C-TCM) by considering the phosphorus doping effect for SHE analysis with any combination of doping, such as phosphorus/boron and arsenic/boron doping, which is validated with reported experimental data. The C-TCM is also compared with the existing Sentaurus TCAD Connelly thermal conductivity model (CN-TCM). The CN-TCM is only valid for undoped conditions at room temperature. This work shows that C-TCM can be used to simulate the realistic thermal behavior of the device with ambient temperature ( ${T}_{A}{)}$ variation. With C-TCM, the nonuniform lattice temperature ( ${T}_{L}{)}$ and heat generation were observed along the channel length due to the non-uniformity $kappa $ of the device. The influence of SHE on the device performance in terms of electrical characteristics and hot-carrier injection (HCI) is also observed along with ${T}_{A}$ variation. SHE rises the peak of ${T}_{L}{,}$ causing $sim $ 10% ON-current and $sim $ 0.7% mobility degradation. The SHE implication on HCI is also examined, and it was found that gate leakage current ( ${I}_{text {G}}{)}$ is enhanced by a factor of $sim $ 55, highlighting the importance of thermal study for next-generation high-performance devices that do not compromise reliability.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Analytical Parasitic Resistance and Capacitance Models for Nanosheet
           Field-Effect Transistors

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      Authors: Junha Suk;Yohan Kim;JungHo Do;Garoom Kim;SangHoon Baek;Jongwook Kye;Soyoung Kim;
      Pages: 2941 - 2946
      Abstract: We developed analytical compact models of parasitic resistance and capacitance (RC) for nanosheet field-effect transistors (NSFETs) with metal contact structures. The proposed model accurately captures the number of sheets, sheet geometry, gate, source, drain, and contact sizes. The parasitic resistance model generated in each region was modeled using the transmission line method (TLM) and the spread resistance model. The parasitic capacitance model was modeled using the conformal mapping method based on the distribution of the electric field. The developed models were validated by changing the structural parameters. The proposed models were implemented in Berkeley short-channel IGFET model (BSIM)-common multi-gate (CMG) to enable circuit performance prediction. With our proposed model, we can accurately predict the circuit performance of NSFETs, capturing the recent scaling trends and process variations in the proposed NSFET.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Degradation of VDMOS Under Simultaneous and Sequential Stress of Gamma Ray
           Irradiation and Annealing Process

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      Authors: Xinyu Li;Yunpeng Jia;Xintian Zhou;Yuanfu Zhao;Liang Wang;Tongde Li;Xingyu Fang;Guo Jia;Zhonghan Deng;
      Pages: 2947 - 2955
      Abstract: In this article, the degradation mechanisms of radiation-hardened vertical double-diffused MOSFETs (VD-MOSFET) experiencing gamma ray irradiation and annealing sequentially experiment device and simultaneously experiment device (Si-ED) are studied and compared. Experiments demonstrate that the Si-ED irradiated with gate bias (+12 V) has a lower oxide-trapped charges increment ( $Delta {N}_{text {ot}})$ and higher interface states increment ( $Delta {N}_{text {it}})$ , compared to those of sequential experiment device (Se-ED). However, for Si-ED irradiated with drain bias (200 V), it shows lower $Delta {N}_{text {ot}}$ and $Delta {N}_{text {it}}$ than those of Se-EDs, which is similar to that observed in the case of devices irradiated with three-terminal bias (200-V drain bias, −10-V gate bias, and source grounded). In addition, for all cases, it is seen that the drain-biased devices own a larger $Delta {N}_{text {ot}}$ but a smaller $Delta {N}_{text {it}}$ , compared to those of gate-biased ones, and the three-terminal-biased devices show the lowest, especially in Si-ED. As a result, the variations of $Delta {N}_{text {ot}}$ and $Delta {N}_{text {it}}$ could cause different degradations of threshold voltage, breakdown voltage, leakage current, and ON-state resistance of devices, which would inevitably threaten the proper functioning of electrical systems. Moreov-r, in this article, it is concluded that the existing standard, i.e., accelerated annealing after irradiation, cannot reflect the actual radiation reliability of devices. Other evaluation methods regarding total ionizing dose (TID) need to be further explored comprehensively.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Performance Boost of Si TFETs by Insertion of III–V Dipole Formation
           Layer: A First Principle Study

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      Authors: Yeongjun Lim;Junbeom Seo;Mincheol Shin;
      Pages: 2956 - 2961
      Abstract: Silicon channel tunnel field-effect transistors (TFETs) are known to exhibit low ON-state current due to the wide indirect band gap. In this work, to achieve high ON-state current, we propose a Si TFET with an ultra-thin dipole formation layer (DFL) inserted at the source/channel junction. The inserted DFL forms charge transfer dipoles at the interface, resulting in a staggered band gap. As the consequence, the effective tunnel barrier for electrons is significantly lowered so that ON-state current increases by orders of magnitude. To analyze the characteristics of DFL-inserted Si TFETs, we have solved nonequilibrium Green’s function (NEGF) and Poisson’s equation using density functional theory (DFT) Hamiltonians. We demonstrate that DFL-inserted Si TFETs show boosted performance over conventional TFETs, exhibiting high ON-state current and steep subthreshold swing (SS).
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Interfacial Layer Engineering in Sub-5-nm HZO: Enabling Low-Temperature
           Process, Low-Voltage Operation, and High Robustness

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      Authors: Eunseon Yu;Xiao Lyu;Mengwei Si;Peide D. Ye;Kaushik Roy;
      Pages: 2962 - 2969
      Abstract: For low-voltage reliable operation of ferroelectric devices, the scaling of Hf $_{{1}-{x}}$ ZrxO2 (HZO) thickness ( ${t}_{text {HZO}}$ ) is important. Despite the importance of scaling, ferroelectricity degradation and increased process thermal budget hinder progress. In this work, we propose the use of an interfacial layer (IL) to mitigate these scaling issues and validate its effectiveness in thin ${t}_{text {HZO}}$ . Our findings demonstrate that IL can activate ferroelectricity below the critical temperature of ferroelectric HZO. Moreover, we report $2times $ polarization improvement, reduced operation voltage from 1.5 to 1.2 V, and substantially improved endurance with $>$ 10 years of reliability, all based on experimental results. We believe this systematic work offers a simple yet efficient route toward HZO scaling in ferroelectric devices.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Analysis of VTH Degradation and Recovery Behaviors of p-GaN Gate HEMTs
           Under Forward Gate Bias

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      Authors: Xin Chao;Chengkang Tang;Jingjing Tan;Lin Chen;Hao Zhu;Qingqing Sun;David Wei Zhang;
      Pages: 2970 - 2974
      Abstract: In this work, detailed ${V}_{text {TH}}$ degradation and recovery behaviors of p-GaN gate high electron mobility transistors (HEMTs) are studied under forward gate bias and elevated temperatures. Based on multiple time-evolving stress/recovery experiments, the abrupt negative $Delta {V}_{text {TH}}$ behavior at initial recovery time at low ${V}_{text {GS}}$ level as well as the suppressed ${V}_{text {TH}}$ shift at high temperature have been observed. It is experimentally found that trapped electrons are more rapid-recoverable than the holes, and the carrier trapping effect is mitigated due to the strengthened carrier emission and recombination process across the AlGaN barrier at elevated temperatures. The ON-resistance ( ${R}_{ mathrm{scriptscriptstyle ON}}{)}$ degradation behavior is also investigated within the same experiment, and the trapped holes at the passivation/AlGaN interface result in a decrease in ${R}_{ mathrm{scriptscriptstyle ON}}$ .
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Substrate Biasing Effect in a High-Voltage Monolithically-Integrated
           GaN-on-SOI Half Bridge With Partial Recessed-Gate HEMTs

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      Authors: Da Wang;Li Zheng;Xinhong Cheng;Lingyan Shen;Xiaobo Liu;Shaoyu Liu;Yufei Tian;Junhong Feng;Yuehui Yu;
      Pages: 2975 - 2980
      Abstract: The physical mechanism of the substrate biasing effect (SBE) in a high-voltage monolithically-integrated GaN-on-SOI half bridge with partial recessed-gate high-electron-mobility transistors (HEMTs) is comprehensively analyzed by TCAD simulation. The SBE originates from the capacitive coupling of the buffer layer and the buffer traps, which can be effectively suppressed by the GaN-on-SOI platform with the top Si shorted to the source technology. The simulations show that the ${R}_{text {ON}}$ of high side HEMT on the GaN-on-SOI platform with the top Si shorted to the source is $0.223 {Omega }$ and does not degrade with the bus voltage increase, while the ${R}_{text {ON}}$ increases from 0.223 to $0.900 {Omega }$ for the case on GaN-on-Si platform when the bus voltage increases to 400 V. In addition, for GaN-on-SOI platform with the top Si shorted to the source of HEMTs, the crosstalk can be effectively suppressed and the self-heating effect does not aggravate. Moreover, the integrated half bridge on GaN-on-SOI platform with the top Si shorted to the source shows lower overshoot current, tail current and switching power consumption compared to the half bridge made of two discrete HEMTs on GaN-on-Si platform.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Deep Learning-Monte Carlo Combined Prediction of Side-Effect Impact
           Ionization in Highly Doped GaN Diodes

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      Authors: S. García-Sánchez;R. Rengel;S. Pérez;T. González;J. Mateos;
      Pages: 2981 - 2987
      Abstract: The existence of leakage current pathways leading to the appearance of impact ionization and the potential device breakdown in planar Gunn GaN diodes is analyzed by means of a combined Monte Carlo (MC)-deep learning approach. Front-view (lateral) MC simulations of the devices show the appearance of a high-field hotspot at the anode corner of the etched region, just at the boundaries between the dielectric, the GaN-doped layer, and the buffer. Thus, if the isolation created by the etched trenches is not complete, a relevant hot carrier population within the buffer is observed at sufficiently high applied voltages, provoking the appearance of a very significant number of impact ionizations and the consequent avalanche process before the onset of Gunn oscillations. A neural network trained from MC simulations allows predicting with extremely good precision the breakdown voltage of the diodes depending on the doping of the GaN active layer, the permittivity of the isolating dielectric, and the lattice temperature. Low doping, high temperature, and high permittivity provide larger operational voltages, which implies a tradeoff with the conditions required to achieve terahertz (THz) Gunn oscillations at low voltages.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Performance Enhancement of AlGaN/GaN HEMT via Trap-State Improvement Using
           O2 Plasma Treatment

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      Authors: Walid Amir;Ju-Won Shin;Ki-Yong Shin;Surajit Chakraborty;Chu-Young Cho;Jae-Moo Kim;Sang-Tae Lee;Takuya Hoshi;Takuya Tsutsumi;Hiroki Sugiyama;Hideaki Matsuzaki;Dae-Hyun Kim;Tae-Woo Kim;
      Pages: 2988 - 2993
      Abstract: Herein, we present a detailed analysis of the effects of O2 plasma treatment on the AlGaN barrier volume trap states in an Al0.45Ga0.45N/GaN high-electron mobility transistor. Compared to that of the as-grown sample, the single short-pulse ${I}_{D}$ – ${V}_{text {GS}}$ characterization of the plasma-treated sample exhibited lower charge trapping inside the AlGaN barrier. The 1/ ${f}$ low-frequency noise characterization revealed a significant reduction of approximately 67% in the volume trap density of the AlGaN barrier layer after O2 plasma treatment. This was achieved by the formation of Al–O and Ga–O bonds via the penetration of oxygen ions into the AlGaN bulk, which resulted in reduced trap state density in the AlGaN barrier. In addition, the Schottky characteristics were improved notably. Consequently, the O2 plasma-treated sample did not display current collapse and showed steady drain current output under the reverse-sweep drain-stress bias conditions. Furthermore, the plasma treatment significantly reduced the RF transconductance ( ${g}_{m}$ ) collapse in the as-grown sample, and significantly increased the ${f}_{T}/{f}_{text {max}}$ of the plasma-treated sample from 65/70 to 120/230 GHz for ${L}_{g}$ = 80 nm devices, respectively. Last, the O2 plasma-treated sample showed substantial improvements in ${P}_{text {out}_max}$ , power added efficiency (PAE), and linear gain from 1.25 W/-m, 20%, and 15 dB to 2.4 W/mm, 50%, and 19 dB, respectively.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Micro-Transfer Printing for Heterogeneous Integration of GaN and GaAs
           HEMTs

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      Authors: Brian P. Downey;Shawn Mack;Andy Xie;D. Scott Katzer;Andrew C. Lang;James G. Champlain;Yu Cao;Neeraj Nepal;Tyler A. Growden;Vikrant J. Gokhale;Matthew T. Hardy;Edward Beam;Cathy Lee;David J. Meyer;
      Pages: 2994 - 3000
      Abstract: Here, we use the micro-transfer printing technique to demonstrate the device-level heterogeneous integration of two solid-state RF device technologies on the same interposer: GaN and GaAs high-electron-mobility transistors. The devices are released from their growth substrate using an epitaxial sacrificial layer while a thin polymer adhesion layer facilitates a strong bond between the target substrate and the compound semiconductor devices, allowing for post-transfer microfabrication processing. Transmission electron microscopy reveals no voids at the device/interposer interface and a polymer adhesion layer thickness of 5 ± 2 nm. No significant degradation in dc electrical characteristics is observed after device transfer for either device technology. Improvement in thermal performance of GaN devices was demonstrated when transferred to a diamond substrate, even with the thin polymer adhesion layer at the device/interposer interface, illustrating a pathway for enhanced thermal management for GaN and other high-output-power density semiconductor technologies. The ability to combine various solid-state technologies at the device level with high density provides an approach to meet next-generation demands for RF and mixed-signal circuits.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Scaled InAlN/GaN HEMT on Sapphire With fT/fmax of
           190/301 GHz

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      Authors: Yawei He;Lian Zhang;Zhe Cheng;Chengcheng Li;Jiaheng He;Shujie Xie;Xuankun Wu;Chang Wu;Yun Zhang;
      Pages: 3001 - 3004
      Abstract: In this brief, a scaled In $_{{0}.{17}}$ Al $_{{0}.{83}}text{N}$ /GaN high-electron-mobility transistor (HEMT) was fabricated on sapphire substrate with 47-nm ${T}$ -gate length, 300-nm source–drain distance, and selective area regrown $text{n}^{+}$ -GaN. The device exhibits cutoff frequencies ${f}_{text {T}}/{f}_{text {max}}$ of 190/301 GHz, which gives a record sqrt ( ${f}_{text {T}} times {f}_{text {max}}{)}$ = 239 GHz among reported Ga-polar GaN-on-sapphire HEMTs. The device shows a maximum current density, a peak external direct current transconductance, and an ${I}_{text {on}}/{I}_{text {off}}$ ratio of 1.45 A/mm, 610 mS/mm, and $2.9times 10^{6}$ , respectively. Drain-induced barrier lowering of 75 mV/V is measured at ${I}_{text {ds}}$ = 1 mA/mm between ${V}_{text {ds}}$ = 1 V and 5 V. The three-terminal OFF-state breakdown voltage is 14.7 V. The effective electron velocity of the 2-D electron gas (2DEG) under the gate foot is estimated to be $1.4times 10^{7}$ cm/s. These characteristics of this Ga-polar millimeter wave (mm-wave) GaN-on-sapphire HEMT are comparable with those state-of-the-art counterparts on SiC substrates.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Transconductance Overshoot, a New Trap-Related Effect in AlGaN/GaN HEMTs

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      Authors: Gao Zhan;Fabiana Rampazzo;Carlo De Santi;Mirko Fornasier;Gaudenzio Meneghesso;Matteo Meneghini;Hervé Blanck;Jan Grünenpütt;Daniel Sommer;Ding Yuan Chen;Kai-Hsin Wen;Jr-Tai Chen;Enrico Zanoni;
      Pages: 3005 - 3010
      Abstract: DC characteristics of AlGaN/GaN HEMTs with different thickness values of the undoped GaN channel layer were compared. An abnormal transconductance ( ${g}_{m}{)}$ overshoot accompanied by a negative threshold voltage ( ${V}_{text {TH}}{)}$ shift was observed during ${I}_{text {DS}}$ – ${V}_{text {GS}}$ sweep in devices with thinner GaN layer. At the same time, a non-monotonic increase in gate current was observed. In OFF-state, electron trapping occurs in the undoped GaN layer or at the GaN/AlN interface, leading to a positive ${V}_{text {TH}}$ shift. When the device is turning on at a sufficiently high ${V}_{text {DS}}$ , electron de-trapping occurs due to trap impact-ionization; consequently, ${V}_{text {TH}}$ and therefore ${I}_{text {D}}$ suddenly recovers, leading to the ${g}_{m}$ overshoot effect. These effects are attributed to electron trap impact-ionization and consequent modulation of the device’s electric field.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Physical Insights Into Electron Trapping Mechanism in the Carbon-Doped GaN
           Buffer in AlGaN/GaN HEMTs and Its Impact on Dynamic On-Resistance

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      Authors: Vipin Joshi;Rajarshi Roy Chaudhuri;Sayak Dutta Gupta;Mayank Shrivastava;
      Pages: 3011 - 3018
      Abstract: In this work, a well-calibrated computational framework is used to probe the physical mechanisms leading to electron trapping in the carbon-doped GaN buffer in AlGaN/GaN HEMTs. Device variants having higher lateral electric field were found to exhibit a drastic increase in dynamic ON resistance beyond a critical drain stress voltage. Computations were done while considering trapping on the device surface, with and without accounting for hot electrons, as well as trapping in the GaN buffer. Detailed analysis established electron injection and trapping in the C-doped GaN buffer to be responsible for the observed dynamic ON resistance behavior. Physical insights are provided into the electron injection and trapping behavior by analyzing field evolution near the field plate edge, field-enhanced trapping, and its impact on the leakage current path within the GaN buffer. Finally, the proposed mechanism of field-enhanced electron trapping is validated by computations with device variants having field-independent trapping process and different buffer trap activation energies.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • “Cold” Tunneling Ohmic Contact With p-GaAs Nanolayer 10 nm
           Thick

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      Authors: Valery M. Mikoushkin;Elena A. Makarevskaya;Dmitry A. Novikov;Sergei Y. Nikonov;Irina B. Suslova;
      Pages: 3019 - 3025
      Abstract: To elucidate the possibility of creating an ohmic contact with an extremely thin p-GaAs nanolayer, we have studied the properties of the contact deposited without annealing (“cold” contact) with a p-layer $sim $ 8 nm thick formed on the n-GaAs wafer by low-energy Ar $^{+}$ ions due to the conductivity type conversion (n $to $ p). Exclusion of annealing prevents metallization of the semiconductor nanolayer. Despite the obvious formation of the Schottky barrier and the presence of a residual oxide layer, the current–voltage characteristics of the ion-induced p-n structure indicates the ohmic nature of the contact. It is shown that high concentration of defects in the irradiated p-layer leads to a decrease in the barrier width down to the value ${W}$ = 0.3 nm, which is much smaller than the de Broglie wavelength of p-layer charge carriers ( $lambda>$ 2–19 nm). Therefore, the ohmic character of the contact is provided by holes and electrons of the p-layer tunneling through the barrier. It is shown that the “cold” tunneling ohmic contact on p-GaAs can be formed with any metal if a defect or doping density is ${N}_{text {D}}> 10^{20}$ cm $^{-{3}}$ , which is an order of magnitude higher than the value ( ${N}_{text {D}}> 10^{19}$ cm $^{-{3}}{)}$ considered as providing efficient tunneling of carriers through a contact with heavily doped n-type semiconductors.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Effects of Neutron Irradiation on Electrical Performance of β-Ga2 O3
           Schottky Barrier Diodes

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      Authors: Shaozhong Yue;Xuefeng Zheng;Yuehua Hong;Xiangyu Zhang;Fang Zhang;Yingzhe Wang;Xiaohua Ma;Yue Hao;
      Pages: 3026 - 3030
      Abstract: The effect of neutron irradiation on the electrical performance of the $beta $ -Ga2O3 Schottky barrier diode (SBD) device has been studied in this work. After equivalent 1 MeV neutron irradiation with a fluence of $1times 10^{{14}}$ n/cm2, a 20% decrease in the forward current density ( ${J}_{text {F}}{)}$ , a 75% reduction in the reverse current density ( ${J}_{text {R}}{)}$ , and a 300 V increase in the breakdown voltage ( ${V}_{text {br}}{)}$ have been observed according to current–voltage ( ${I}$ – ${V}{)}$ measurements. Utilizing the frequency-dependent conductance technique, it is found that the density of interface states located at Pt/Ga2O3 increases slightly from $2.6times 10^{{12}}$ – $6.4times 10^{{12}}$ to $2.9times 10^{{12}}$ – $7.0times 10^{{12}}$ cm $^{-{2}}$ eV $^{-{1}}$ with an increase in trap activation energy from 0.09–0.122 to 0.096–0.134 eV after neutron irradiation. Fur-hermore, based on the capacitance–voltage ( ${C}$ – ${V}{)}$ measurement, it is observed that the carrier concentration across the Ga2O3 drift layer was decreased from $1.80times 10^{{16}}$ to $1.35times 10^{{16}}$ cm $^{-{3}}$ after neutron irradiation. Considering the device performance change, it indicates that the bulk traps within the Ga2O3 drift layer instead of interface states dominate the device degradation.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Understanding Rhythmic Synchronization of Oscillatory Neural Networks
           Based on NbOx Artificial Neurons for Edge Detection

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      Authors: Hyun Wook Kim;Seonuk Jeon;Heebum Kang;Eunryeong Hong;Nayeon Kim;Jiyong Woo;
      Pages: 3031 - 3036
      Abstract: Oscillatory neural networks (ONNs) directly emulate signal communication between biological neurons in the human brain by encoding the data in phase domain, enabling energy-efficient associative memory. An oscillation neuron (ON) element that generates continuous voltage spikes with a specific frequency needs to be designed for hardware implementation. Thus, we systematically investigate the role of the ON in edge detection in ONN systems through simulation. First, a threshold switch is experimentally fabricated for the ON using niobium oxide (NbO $_{x}{)}$ material, and voltage oscillation is realized in HSPICE and MATLAB. Subsequently, we examine how each voltage oscillation in a coupled-ON system, in which two NbOx-based ONs are connected with a coupling resistance, is mutually synchronized. Simulation results reveal that a small (or large) coupling resistance strengthens the in-phase (or out-of-phase) synchronization of the two independent oscillations. The synchronized phase expressed in the form of period is found to be adjusted by tuning various components. As two clearly distinguishable phases are obtained, ONN systems, where multiple ONs are cross-coupled, can be utilized for edge detection during image processing. Patterns are trained using Hebbian learning rule in an ONN system comprising ten ONs, and a feature of the handwritten digit image is accurately extracted. Moreover, the feasibility of accelerating the edge detection step is further explored through various engineering approaches to change the characteristics of the NbOx-based ONs.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Analytical Procedure for the Extraction of Material Parameters in
           Antiferroelectric ZrO2

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      Authors: Mattia Segatto;Filippo Rupil;David Esseni;
      Pages: 3037 - 3042
      Abstract: Here, we present an analytical procedure to extract the anisotropy constants of antiferroelectric (AFE) materials from a few key features of the experimental polarization versus field curves. Our approach is validated for two experimental datasets of ZrO2 capacitors, and the extracted parameters are consistent with the microscopically nonpolar nature of the zero-field state of the AFE ZrO2. The methodology has applications in AFE nonvolatile memories and memristors, as well as in electron devices exploiting the negative capacitance (NC) operation of ZrO2.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Investigation of Endurance Degradation Mechanism of Si FeFET With HfZrO
           Ferroelectric by an In Situ Vth Measurement

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      Authors: Xianzhou Shao;Junshuai Chai;Fengbin Tian;Shujing Zhao;Jiahui Duan;Xiaoyu Ke;Xiaoqing Sun;Jinjuan Xiang;Kai Han;Yanrong Wang;Hao Xu;Xiaolei Wang;Jing Zhang;Wenwu Wang;Tianchun Ye;
      Pages: 3043 - 3050
      Abstract: We propose an in situ ${V}_{text {th}}$ measurement method to investigate the endurance fatigue mechanism of Si ferroelectric field-effect transistor (FeFET) with HfZrO ferroelectric. The in situ ${V}_{text {th}}$ measurement method means that a pulsed current-voltage measurement is embedded during the quasi-static capacitance-voltage (QSCV) measurement. Based on this method, the trapped charges can be extracted as a function of the gate voltage ( ${V}_{g}{)}$ . We find that: First, the trapped electrons and holes show asymmetric de-trapping dynamics. Excess electrons continuously de-trap within the ${V}_{g}$ ranging from the maximum positive value to ferroelectric reverse switching. However, the trapped holes do not de-trap when the ${V}_{g}$ changes from the minimum negative value to 0 V. Second, the increase of donor trap density is the key to endurance fatigue. During endurance fatigue, the total amounts of trapped electrons are unchanged near the maximum positive voltage, but the amounts of de-trapped electrons decrease when the ${V}_{g}$ returns to 0 V due to donor trap density increases. In addition, we apply our method in the scaled FeFET to overcome the measurement limitation of gate charges ( ${Q}_{m}{)}$ by the nowadays equipment.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Fully Inkjet-Printed Unipolar Metal Oxide Memristor for Nonvolatile
           Memory in Printed Electronics

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      Authors: Hongrong Hu;Alexander Scholz;Yan Liu;Yushu Tang;Gabriel Cadilha Marques;Jasmin Aghassi-Hagmann;
      Pages: 3051 - 3056
      Abstract: Memristors are an interesting novel class of devices for memory and beyond von Neumann computing. Besides classical CMOS technology, memristors can also be manufactured by additive printing techniques and hold great potential for printable neuromorphic circuits and memories. In this work, we report a fully inkjet-printed unipolar metal oxide memristor with a low forming voltage. The memristor is based on a sandwich-like Ag/ZnO/Ag structure. The device exhibits excellent performance parameters, such as high cycle-to-cycle and device-to-device uniformity and a long retention time of ${geq } {10}^{{4}}$ s. Furthermore, the inkjet-printed memristor shows an exceptionally high $R_{mathrm{OFF}} / R_{mathrm{ON}}$ ratio of ${10}^{{7}}$ over 100 pulsed switching cycles.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Noble-Metal-Free, Polarity-Switchable IGZO Schottky Barrier Diodes

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      Authors: Yuzhi Li;Yue Zhou;Chan Guo;Shenghan Zou;Linfeng Lan;Zheng Gong;
      Pages: 3057 - 3063
      Abstract: In this work, noble-metal-free, polarity-switchable indium-gallium-zinc oxide (IGZO) Schottky barrier diodes (SBDs) with a vertically stacked structure of copper (Cu)/AlOx/IGZO/indium-tin oxide (ITO) were demonstrated for the first time. The polarity of the SBDs can be manipulated through a simple postannealing process in $text{N}_{{2}}$ . Without annealing, the as-fabricated IGZO SBD works in a negative operation mode (i.e., the dominating current flow direction is from the bottom ITO electrode to the top Cu electrode). The optimized SBD working in the negative mode exhibits excellent electrical properties with a rectification ratio of $2.12times 10^{6}$ , a Schottky barrier height of 0.87 eV, and an ideality factor of 1.26. After annealing in $text{N}_{{2}}$ , the IGZO SBD switches to a positive operation mode. Through optimization, the positive SBD exhibits a rectification ratio of $4.24times 10^{5}$ , a Schottky barrier height of 0.83 eV, and an ideality factor of 1.43. The mechanism of polarity inversion behavior for the IGZO SBDs was discussed in detail by taking the Cu diffusion and contact modification via the AlOx inserting layer into account. This work sheds light on the development of noble-metal-free metal oxide (MO) SBDs with controllable polarities and the future integration of MO SBDs with other electron devices.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Improvement of Voltage Linearity and Leakage Current of MIM Capacitors
           With Atomic Layer Deposited Ti-Doped ZrO2 Insulators

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      Authors: Guang Zheng;Yu-Li He;Bao Zhu;Xiaohan Wu;David Wei Zhang;Shi-Jin Ding;
      Pages: 3064 - 3070
      Abstract: MIM capacitors have been widely investigated as passive devices in integrated circuits. In this work, Ti-doped ZrO2 (ZTO) thin films prepared by plasma-enhanced atomic layer deposition (PEALD) are explored as the dielectrics of MIM capacitors. First, modulation of capacitance density and quadratic voltage coefficient of capacitance ( $alpha {)}$ is achieved for the MIM capacitors by adjusting the ALD cycle ratio of TiO2/ZrO2 (Ti/Zr). The $alpha $ -value exhibits a decreasing trend with increasing the content of Ti, even down to a negative value. In terms of Ti/Zr=1/2, the capacitor shows a minimum $vert alpha vert $ value of 219 ppm/ $text{V}^{{2}}$ , accompanied by a capacitance density of 11.64 fF/ $mu text{m}^{{2}}$ . Furthermore, an additional $text{O}_{{2}}$ plasma treatment (5 min) of the ZTO dielectric significantly reduces the leakage current by three orders of magnitude; meanwhile, the $alpha $ -value decreases by $sim $ 42%. In a word, the optimized capacitor demonstrates good electrical properties including a capacitance density of 12.21 fF/ $mu text{m}^{{2}}$ , $alpha $ of 128 ppm/ $text{V}^{{2}}$ , leakage current of ${7}.{85} times {10} ^{-{7}}$ A/cm2 at 1 V, and temperature coefficient of capacitance (TCC) of 194 ppm/ $text{V}^{{2}}$ . This is related to the passivation of oxygen vacancies in ZTO caused by $text{O}_{{2}}$ plasma treatment.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Stacked HZO/α-In2Se3 Ferroelectric Dielectric/Semiconductor FET With
           Ultrahigh Speed and Large Memory Window

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      Authors: Jiali Huo;Zhaohao Zhang;Yadong Zhang;Fan Zhang;Gangping Yan;Guoliang Tian;Haoqing Xu;Guohui Zhan;Gaobo Xu;Qingzhu Zhang;Huaxiang Yin;Zhenhua Wu;
      Pages: 3071 - 3075
      Abstract: In this work, by integrating the ferroelectric Hf0.5Zr0.5O2 (HZO) gate insulator and 2-D ferroelectric semiconductor $alpha $ -In2Se3 channel, ferroelectric field effect transistors (FeFETs) featured with both enhanced large memory windows (MWs) and ultrahigh-speed are demonstrated. Contributing to HZO/ ${alpha }$ -In2Se3 stacked ferroelectrics and the adoption of HZO gate dielectric with the high coercive electric field ( ${E}_{c}{}$ ), large MWs (4.2 V at ${V}_{text {GS}}$ sweep range (SR) of ±4 V) are obtained. Besides, owing to the enhanced cross-electric field and the fast polarization switching speed of the HZO layer, the FeFETs show an ultrahigh writing speed of 10 ns. Furthermore, the FeFETs exhibit excellent performances with a high drain current ON/ OFF ratio ( $10^{{7}}$ ), high endurance cycles ( $10^{{4}}$ cycles), and long retention time ( $10^{{4}}$ s). These results demonstrate that the FeFETs have considerable potential in ultra-fast nonvolatile memory (NVM) applications.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Piezoelectric Strain FET (PeFET)-Based Nonvolatile Memories

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      Authors: Niharika Thakuria;Reena Elangovan;Anand Raghunathan;Sumeet K. Gupta;
      Pages: 3076 - 3084
      Abstract: We propose nonvolatile memory (NVM) designs based on piezoelectric strain FET (PeFET) utilizing piezoelectric/ferroelectric material (PE/FE such as PZT) coupled with 2-D transition metal dichalcogenide (2-D-TMD such as MoS $_{{2}}{)}$ -based transistor. The proposed NVMs store bit information in the form of polarization ( ${P}$ ) of FE/PE, use electric-field driven ${P}$ -switching for write, and employ piezoelectricity-induced dynamic bandgap modulation of 2-D-TMD channel for bit sensing. We analyze PeFET with COMSOL-based 3-D modeling, showing that circuit-driven optimization of PeFET geometry is essential to achieve effective strain transduction and adequate bandgap modulation for NVM read. We achieve distinguishability of up to $11times $ in binary states of PeFETs. We propose various flavors of PeFET NVMs, namely: 1) high-density (HD) NVM featuring a compact access-transistor-less bit-cell; 2) 1T-1PeFET NVM with segmented architecture, targeted for optimized write energy and latency; and 3) cross-coupled (CC) NVM offering a tradeoff between area and latency. PeFET NVMs offer up to $7times $ smaller cell area, 66% lower write energy, 87% lower read energy, and 44% faster read compared to 2-D-FET static random access memory (SRAM). This comes at the cost of high write latency in PeFET NVMs, which can be minimized by virtue of optimized PE geometry.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Heterojunction Channel Engineering in Performance Enhancement of
           Solution-Processed Oxide Thin-Film Transistors

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      Authors: Wensi Cai;Mengchao Li;Shirong Lu;Qingkai Qian;Zhigang Zang;
      Pages: 3085 - 3091
      Abstract: With the continuous development of next-generation display techniques, more and more attention has been put on solution-processed oxide thin-film transistors (TFTs). Here, we report the solution-based growth of InZnO/AlInZnO (IZO/AIZO) heterojunction channel layers and their implementation in high-performance TFTs. It is found that the heterojunction transistors exhibit a band-like electron transport, with both current ON/OFF ratio and mobility values significantly higher than single-layer IZO and AIZO devices by more than one order of magnitude. The marked improvement here is demonstrated to originate from the presence of confined free electrons at the atomically sharp heterointerface induced by the large conduction band offset between IZO and AIZO. Further channel engineering including the modification of In:Zn ratios, IZO, and AIZO thicknesses allows us to obtain high-performance heterojunction oxide TFTs with a high current ON/OFF ratio of $5times 10^{{7}}$ , a mobility of 14.4±1 cm2/Vs, a turn-on voltage close to zero-volt, and a superb stability against bias stresses and long-term storage. The high performance combined with the solution-processability enables the great potential of our reported TFTs in next-generation printable electronics.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Fine-Tunable Emission Pulse Generation Circuit Based on p-Type
           Low-Temperature Poly-Si Thin-Film Transistors for Active Matrix Organic
           Light-Emitting Diode Displays

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      Authors: Min Kyu Chang;Ji Hoon Kim;Hyoungsik Nam;
      Pages: 3092 - 3099
      Abstract: Active matrix organic light-emitting diode (AMOLED) displays have deployed the compensation techniques to cope with the luminance non-uniformity issues caused by variations on electrical characteristics of thin-film transistors (TFTs). While some compensation circuits require control signals of longer pulse widths than a line time, the luminance control as well as the higher bit depth representation have been also accomplished by adjusting the pulse widths. A proposed EM pulse generation circuit consists of 11 p-type low-temperature poly-Si (LTPS) TFTs and a one coupling capacitor. While previous tunable circuits could address pulse widths of either even or odd multiples of a line time, the proposed circuit can generate any multiples by changing phases of additional clock signals. In particular, the internal inverter is implemented with a load connected to the output of a previous stage’s inverter to reduce the power consumption over pulse widths. The coupling capacitor is also connected between two adjacent stages through one TFT, eliminating coupling noises on the output pulses. The proposed EM circuit is simulated at a line time of $3.8~mu text{s}$ for a 120 Hz ${3840} times {2160}$ display. The results ensure that pulse widths from three to 2160 lines are generated successfully without coupling noises and the small variation on power consumption from 1.23 to 0.33 mW is achieved at 30 stages for the whole range of pulse widths, compared to the large range from 1.26 to 76.91 mW with the inverter of a diode-connected load.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Electrical Evolution of p-Type SnOx Film and Transistor Deposited by RF
           Magnetron Sputtering

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      Authors: Yuyan Zhou;Yu Song;Ruohao Hong;Xingqiang Liu;Xuming Zou;Benjamin Iníguez;Denis Flandre;Guoli Li;Lei Liao;
      Pages: 3100 - 3105
      Abstract: In this work, by altering oxygen partial pressure (OPP) and sputtering power ( ${P}_{text {RF}}$ ) of the radio frequency (RF) magnetron sputtering process, we investigate electrical evolution of the p-type SnOx film and transistor. Herein, combining device current–voltage (such as ON-state current and field-effect mobility), low-frequency noise (LFN), and gate-bias-stress characteristics, we find that the optimal OPP range is 4.8%–7.2% for the SnOx film deposition at ${P}_{text {RF}}$ of 70 and 30 W. Based on X-ray photoelectron spectroscopy (XPS), the SnOx films deposited at high power (70 W) show less sensitivity to OPP, which leads to the slow transition of internal Sn2+, Sn4+ states, and a relatively large process window. Furthermore, the defect states inside the SnOx are analyzed. The oxygen interstitials (Oi), as deep acceptors, keep inactive regardless of the external bias. The oxygen vacancies (Vo) and the ionized Vo2+ states, which act as the electron traps, get suppressed and are attributed to the ambipolar behavior in the SnOx transistor, while increasing the OPP. This work benefit lies in a comprehensive analysis of the sputtering process parameters impact on SnOx film and transistor properties and their underlying defects.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Conformable Carbon Nanotube Thin Film Transistors on Ultrathin Flexible
           Substrates

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      Authors: Li Xiang;Huaidong Ye;Hui Wang;Yuwei Wang;
      Pages: 3106 - 3111
      Abstract: Skin-like electronics that enable robust, intimate, and comfortable contact for direct biotic/abiotic interface are highly expected in next-generation wearable clinical and biological technologies. Carbon nanotubes (CNTs) have emerged as one of the leading candidates of flexible semiconducting materials due to their high carrier mobility, mechanical flexibility, and solution-processed fabrication, which could make important contributions to skin-like electronics. In this work, incorporating device fabrication on ultrathin substrate ( $1.4 mu text{m}$ thick) and capillary-assisted electrochemical delamination (CAED) process, CNT-based thin film transistors (TFTs) were realized with great conformability to biological surfaces, even contacting with the ridges and valleys on human fingertips. Excellent flexibility was also achieved with little performance degradation of CNT TFT after being deformed by bending or wrapping onto human hairs. The CNT TFT on ultrathin substrate demonstrates good electrical properties with mobility of 23 cm $^{{2}}text{V}^{-{1}}text{s}^{-{1}}$ , current ON- OFF ratio of $10^{{5}}$ , and subthreshold swing of 109 mV/dec. A flexible amplifier was constructed based on the CNT TFTs with a low voltage supply (±1 V) and wide bandwidth (3.7 kHz). Such simultaneously achieved great conformability, low-voltage supply, and wide bandwidth of the flexible amplifier provide important capabilities and opportunities for CNT-based electronics in future advanced biological or clinical applications.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Low-Voltage Operated High DC Gain Amplification Stage Based on Large-Area
           Manufacturable Amorphous Oxide Semiconductor Thin-Film Transistor

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      Authors: Li’Ang Deng;Lei Han;Bang Ouyang;Xiaokuan Yin;Xiaojun Guo;
      Pages: 3112 - 3116
      Abstract: The industry-standard amorphous metal–oxide–semiconductor (AOS) thin-film transistor (TFT) technology is demonstrated for making low-voltage high intrinsic gain devices. It is revealed by the technology computer-aided design (TCAD) simulation that, without need of making Schottky barrier contacts, large output resistance and high intrinsic gain can be achieved in a subthreshold regime for AOS TFTs. It is further proved by the measurement results with the fabricated AOS TFT from a Gen-4.5 manufacturing line. A simple single-stage zero- ${V}_{text {GS}}$ load amplifier is implemented as a proof of concept, achieving a voltage gain larger than 50 for weak signal detection at a supply voltage of 5 V.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Performance Enhancement of Thin-Film Transistor Based on In2O3:F/In2O3
           Homojunction

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      Authors: Bowen Yan;Yanan Ding;Tongzheng Li;Haiyang Qiu;Yepeng Shi;Guoxia Liu;Fukai Shan;
      Pages: 3117 - 3121
      Abstract: In this article, we demonstrate a high-performance thin film transistor (TFT) based on a double-stack fluorine-doped In2O3/In2O3(InFO/InO) homojunction channel. The InFO and In2O3 semiconductor thin films were fabricated by solution process and acted as front and back channels, respectively. By using the unique bandgap characteristic of fluorine dopant, the TFT based on the InFO/InO homojunction channel exhibits improved electrical performance, including a field-effect mobility ( $mu _{text {FE}}{)}$ of 5.69 cm2/Vs and a high ON/OFF current ( ${I}_{text {on}}/{I}_{text {off}}{)}$ ratio of $10^{{8}}$ . X-ray photoelectron spectroscopy (XPS) analysis proves the importance of the InFO film as the front channel. Furthermore, the InFO/InO TFT was integrated with the Al2O3 dielectric. The TFT exhibits great improvement in electrical performance, including a large $mu _{text {FE}}$ of 31.49 cm2/Vs, high ${I}_{text {on}}/{I}_{text {off}}$ ( $sim 10^{{8}}{)}$ , and a small threshold voltage of 1.4 V. These results indicate that the TFT based on InFO/InO homojunction channel exhibits great potential in the field of low-power, flexible and printable electronic devices.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Vertical Ion-Coupling Ga2O3 TFT With Spatiotemporal
           Logic Encryption

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      Authors: Yanran Li;Honglin Song;Jie Jiang;
      Pages: 3122 - 3125
      Abstract: The security of critical hardware components is of great importance for spawning an era of an integrated circuit. Here, a vertical short-channel Ga2O3 thin-film transistor (TFT) is proposed for addressing such security threats. The device has an ultrashort channel of ~10 nm due to the vertical architecture. It not only operates well at a low voltage (2 V) with a reasonable current ON- OFF ratio ( ${I}_{ mathrm{scriptscriptstyle ON}}/{I}_{ mathrm{scriptscriptstyle OFF}}$ ) ( $10^{{3}}$ ), but also realizes the spatiotemporal logic encryption by tuning the ion-coupling path. Moreover, the decryption function of AND logic can only be unlocked by reducing the distance between the gate and channel. Therefore, the proposed device can be regarded as a great step to realize safe electronics in the future.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Extraction Technique for the Conduction Band Minimum Energy in Amorphous
           Indium–Gallium–Zinc–Oxide Thin Film Transistors

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      Authors: Haesung Kim;Han Bin Yoo;Heesung Lee;Ji Hee Ryu;Ju Young Park;Seung Hyeop Han;Hyojin Yang;Jong-Ho Bae;Sung-Jin Choi;Dae Hwan Kim;Dong Myong Kim;
      Pages: 3126 - 3130
      Abstract: The conduction band minimum energy in amorphous oxide semiconductor-based thin film transistors (AOS TFTs) is a key parameter governing the accurate extraction of energy distribution for the subgap density-of-states (DOSs) and carrier mobility. We report a technique for extraction of the gate voltage ( ${V}_{text {CBM}}{)}$ and corresponding energy ( ${E}_{text {F},{text {CBM}}}$ = ${E}_{text {C}-{text {EREF}}}{)}$ for the quasi-Fermi level ( ${E}_{text {F}}{)}$ equal to the conduction band minimum ( ${E}_{text {C}}{)}$ as ${V}_{text {CBM}}$ = ${V}_{text {GS}}$ ( ${E}_{text {F}}$ = ${E}_{text {C}}{)}$ and ${E}_{text {F},{text {CBM}}}$ = ${E}_{text {F}}$ ( ${V}_{text {GS}}$ = ${V}_{text {CBM}}{)}$ . In order to confirm this technique through optoelectronic experimental data, amorphous indium–gallium–zinc–oxide (a-IGZO)-based thin film transistor was irradiated with various wave-engths and power, and obtained ${V}_{text {CBM}}$ = 7.1 V and ${E}_{text {F} {text {CBM}}}$ = 71 meV in the dark state. This technique is expected to be useful in the accurate characterization of the subgap DOS and the effective mobility in AOS TFTs through a simple and effective extraction process.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Efficient Single-Pixel Batch Measurement Method for Optical Properties of
           Micro-Sized LED Array

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      Authors: Zhen Li;Li-Hong Zhu;Ya-Yong Chen;Zhi-Jie Ke;Yu-Lin Gao;Zi-Quan Guo;Wei-Jie Guo;Li-Li Zheng;Zhong Chen;Yi-Jun Lu;
      Pages: 3131 - 3135
      Abstract: The evaluation of single-pixel mini-/micro-light-emitting diode (LED) optical properties among an array or module faces difficulties in total acquisition of weak signal at small driven current and avoiding optical crosstalk from the adjacent chips simultaneously. In this work, we propose an efficient single-pixel batch measurement method, which combines microscopic hyperspectral imaging ( $mu $ -HSI) and a silicon-based micro-integrating sphere array ( $mu $ -ISA). Truncated-inverted-pyramid microcavities coated with gold reflective layer are designed and fabricated in the $mu $ - ISA, which can effectively collect the total optical power of micro-sized LEDs and avoid optical crosstalk from the adjacent chips simultaneously. A 1-in integrating sphere and halogen lamp coupled by optical fiber are used as calibration light source. A two-step procedure is proposed to calibrate the absolute optical power distribution of the $mu $ - HSI measurement method. Comparative studies on optical properties, including photometry and colorimetry, are carried out to demonstrate the advantages of the proposed method in accuracy, capabilities of avoiding optical crosstalk, and batch detection of micro-sized LED (Micro-/Mini-LED) array.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Pinned Photodiode Imaging Pixel With Floating Gate Readout and Dual Gain

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      Authors: Konstantin D. Stefanov;Martin J. Prest;
      Pages: 3136 - 3139
      Abstract: We present an imaging pixel featuring dual conversion gain in a single exposure based on the pinned photodiode (PPD). The signal charge is first converted to voltage nondestructively using a floating gate, and a second conversion is done at a p-n junction-based sense node (SN). Higher signal dynamic range (DR) is achieved due to the sensing of the same charge with two different conversion gains. The results from a prototype 10- $mu text{m}$ -pitch pixel manufactured in a 180-nm CMOS image sensor process demonstrate a gain ratio of 3, DR of 90 dB, 3.6 e− rms readout noise, and negligible image lag.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • High Resolution Micro-LED Arrays Using Au–Sn Flip-Chip Bonding

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      Authors: Haojie Zhou;Kefeng Wang;Xiaoxiao Ji;Luqiao Yin;Jianhua Zhang;
      Pages: 3140 - 3144
      Abstract: In this article, a 0.39-in $512times384$ monochrome micro-light-emitting diode (Micro-LED) array was demonstrated using GaN epi-wafers on sapphire. The array, with a pixel size of $13~mu text{m}$ and a pixel pitch of $15~mu text{m}$ , is connected to the sapphire substrate by Au–Sn flip-chip bonding. A single pixel of Micro-LED shows an extremely low leakage current of 0.2 pA at −5 V and a low threshold voltage of 2.5 V. In the optical aspect, it has a maximum brightness of 10591.8 cd/ $text{m}^{{2}}$ (50.79%) at 700 mA, uniformity of 52.88% (4213.185 cd/ $text{m}^{{2}}{)}$ at small current 180 mA and 54.43% (10225.35 cd/ $text{m}^{{2}}{)}$ at high current 550 mA. The full width at half maxima (FWHM) of the array ranges from 14.5 to 18.4 nm and the peak wavelength variation is 2.1 nm. And it shows a deep-blue emission with CIE coordinates of (0.1506, 0.0289) at 100 mA. The use of high density Au–Sn flip-chip bonding in this work demonstrates a promising solution for the future bonding technology of Micro-LEDs with CMOS, as well as a new direction for the study of high resolution microdisplays.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Filterless and High-Speed InP Near-Infrared Photodetector With an
           Ultra-Small Full-Width at Half Maximum

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      Authors: Li Wang;Xiu-Dong He;Quan-You Wang;Ning Qi;Song-Yun Tian;Mo-Lin Wang;Chun-Yan Wu;Ji-Gang Hu;Lin-Bao Luo;
      Pages: 3145 - 3148
      Abstract: Near-infrared narrowband photodetection between 920 and 960 nm is quite appealing for many applications, such as optical communication, security monitoring, and machine vision, owing to the weak photon-scattering effect and the low intensity of sunlight in this range. Herein, a self-powered narrowband InP photodetector is realized based on a junction-controlled charge-collection narrowing (JCCN) mechanism, exhibiting a peak response centered at 954 nm with a full width at half maximum (FWHM) of 17 nm. Thanks to the reflection of the Schottky electrode and the passivation of the Al2O3 layer, the peak specific detectivity of the device can be up to $4.5times 10^{{11}}$ Jones and a linear dynamic range (LDR) of $sim $ 99 dB is achieved under the illumination of 954 nm. Moreover, the device shows long-term stability and excellent repeatability with a −3 dB frequency of 87.3 kHz. Furthermore, unless the wavelength of the background light is in the range of 945–967 nm, the crosstalk value of the device remains below −10 dB. These results signify that the present InP photodetector is a promising building block for future near-infrared optoelectronic systems.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Self-Powered Implantable CMOS Photovoltaic Cell With 18.6%
           Efficiency

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      Authors: Jinwei Zhao;Roghaieh Parvizi;Rami Ghannam;Man-Kay Law;Finlay Walton;Muhammad Ali Imran;Hadi Heidari;
      Pages: 3149 - 3154
      Abstract: Harvesters for implantable medical applications need to generate enough energy to power their loads, but their efficiency is reduced when implanted under the tissue. Conventional photovoltaic (PV) cell harvesters made with CMOS technology stack cells in series, which raises output voltage but lowers power conversion efficiency. In addition, it is difficult to assess harvester performance prior to fabrication. To address these challenges, we developed a novel parallel PV cell configuration that fully utilizes all triple-well diodes and responds efficiently to near-infrared light. Using an optimized structure, the PV cells were fabricated through standard TSMC 65-nm CMOS technology, achieving an efficiency of 18.6%, open circuit voltage of 0.45 V, and short circuit current of 1.9 mA cm $^{-{2}}$ . These results confirm the ability of the device to generate sufficient energy even when implanted beneath the tissue. Multiphysics finite element modeling (FEM) was used to optimize the stacking structure of the CMOS PV cell, and experimental results showed a successfully delivered power density of 1.2 mW cm $^{-{2}}$ (single cell 1.04 mm2) when placed 2 mm below porcine skin. Different array configurations of six PV cells were also experimentally studied using external wire switching, demonstrating the flexibility of the PV array in delivering different output energy for various implantable devices.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Investigation of the Global Shutter Operation of the Quantum-Dot
           Short-Wave Infrared Image Sensor

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      Authors: Jaenam Kim;Joo-Hyoung Kim;Yun-Tzu Chang;Jihoon Park;Minhyun Jin;Vladimir Pejović;Epimitheas Georgitzikis;Steven Thijs;Itai Lieberman;Yunlong Li;Paul Heremans;Paweł Malinowski;Jung-Hoon Chun;Jiwon Lee;
      Pages: 3155 - 3159
      Abstract: Quantum dot (QD) thin-film photodiodes (TFPDs) are studied extensively in the image sensor field as they can pave the way toward the cost-efficient implementation of short-wave infrared (SWIR) cameras. Interestingly, the QD TFPD image sensors can be operated in the global shutter (GS) mode by turning on the photodiode (PD) only during integration time and subsequently turning it off during the readout. This offers the substantial advantage of reducing the pixel size as it eliminates the need for additional transistors or capacitors that are otherwise typically used in conventional GS pixels. So far, no comprehensive study has yet been performed on this PD turn on/off operation mode. Therefore, in this work, we investigated the PD turn on/off GS operation mode in comparison with the conventional voltage domain (VD) GS operation—a first in-depth report of its kind. We confirm that the PD turn on/off GS mode has the advantage of a small pixel size but comes at the cost of an increasing nonlinearity as the integration time approaches the PD speed limitation. We report a parasitic light sensitivity (PLS) of −70 dB over the visible (VIS) and SWIR range and moreover demonstrate that the PLS has the potential to reach $< -100$ dB based on the discrete PD measurement.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Dynamic Nonlinear Impedance Model of a Single Photon Avalanche Diode

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      Authors: Akito Inoue;Shinzo Koyama;Yutaka Hirose;
      Pages: 3160 - 3165
      Abstract: A nonlinear LCR parallel circuit model of a single photon avalanche diode (SPAD) is derived from a Lienard-type nonlinear differential equation. The resistance and the inductance associated with avalanche multiplication (AM) are time-dependent and governed by the avalanche time constant due to the impact ionization ratio. Time dependences of current, voltage, resistance, and inductance in the model are analyzed by numerically solving the equation. During the initial generation of a Geiger-mode pulse, when the voltage reaches the breakdown voltage, the resistance diverges to limit the maximum current and the inductance reduces to give the maximum speed of the voltage variation with the avalanche time constant. In the frequency domain, avalanche impedance (AI) spectra are obtained as a ratio of voltage and current spectra calculated as Fourier transforms of the time domain signals. The AI spectra exhibit a negative-resistance and an inductance. An analytic expression for the impedance is derived and found to comprise only a quenching resistance and a stray capacitance as indicated by a constant radius of a Nyquist plot. Finally, the present model is shown to incorporate the models of impact-ionization-avalanche transit-time (IMPATT) diodes when a very small-signal limit is assumed.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Degradation of High-Power UVC Light-Emitting Diodes via Emission-Activated
           Nitrogen Vacancy Generation

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      Authors: Chia-Yen Huang;Wen-Hsuan Hsieh;Teng-Li Shao;Chang-Hsien Wu;Tien-Chang Lu;
      Pages: 3166 - 3171
      Abstract: We reported an unexpected power degradation mechanism in high-power ultraviolet C (UVC) light-emitting diodes (LEDs) grown on high-quality AlN templates. The LED underwent an ${I}$ = 350 mA stress for 250 h. After stress, the output power under ${I}$ = 350 mA degraded by 65%. Although the ${I}$ – ${V}$ curve and ${C}$ – ${V}$ curve measurements suggested a strong carrier leakage, the electroluminescence (EL) spectrum did not suggest any significant crystal quality degradation in the active region. Cross-sectional transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) mapping revealed new defects nucleated and propagated from the p-GaN/electron blocking layer (EBL) interface. An observable nitrogen loss was introduced to the p-GaN contact layer under EDS. We inferred that the nitrogen desorption was activated by the UVC photon emitted from the active region. The nitrogen vacancies created a continuous leakage path from the active region to the p-electrode via various trap-assisted transport mechanisms.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • 3-D Segmented Gate Concept: A New IGBT Solution for Reduced Loss and
           Improved Safe-Operating Area

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      Authors: Gaoqiang Deng;Jun Wang;Yifan Wu;Chen Tan;Shiwei Liang;
      Pages: 3172 - 3178
      Abstract: In this article, the “segmented gate (SG)” concept is proposed and implemented in trench gate to realize both low loss and wide safe-operating area (SOA) for insulated-gate bipolar transistors (IGBTs). The poly gate of the proposed IGBT is split into segments along the trench and each segmented poly gate is surrounded by the poly emitter. This unique 3-D trench architecture is demonstrated under numerical studies to be highly effective in enhancing the short-circuit ruggedness, the turn-off capability, and the latch-up immunity. It enables a 37% reduction in saturation current and a 90% reduction in Miller capacitance. The proposed design also shows an improved trade-off relationship between ON-state voltage and turn-off loss. For the same turn-off loss, the ON-state voltage of the proposed IGBT is reduced by 0.25 V when compared with the conventional carrier-stored trench IGBT.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Superjunction Reliability Analysis Under Extreme High Positive and
           Negative Gate Voltage Stress

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      Authors: Hang Xu;Tianyang Feng;Xianghui Li;Yafen Yang;David Wei Zhang;
      Pages: 3179 - 3184
      Abstract: High gate stress test is an extremely important part of power device reliability test. On this basis, a 650 V super junction device is designed and fabricated, conventional stress test including high temperature gate bias (HTGB), high temperature reverse bias (HTRB) test results show that the device possess good reliability. The degradation of performance parameters under extreme high gate stress (including positive and negative) and the corresponding mechanism is further studied. It is found that the main performance parameters of superjunction MOSFET (SJ-MOSFET) will change significantly when the gate voltage stress is greater than 70 V. Under the positive high gate voltage stress, the threshold voltage decreases significantly. Under the negative high gate voltage stress, the threshold voltage also shifted to the left. Comparing the device under the same value of positive and negative high gate stress, it is found that the degradation degree of the device under positive stress is far greater than that under negative stress. Theoretical analysis combined with experimental data believes that the two degradation mechanisms are different. For positive stress, tunneling electrons collide on their way to the gate electrode creating electron–hole pairs, and the holes are captured by traps. But for negative gate voltage, holes tunnel and serve as extra gate positive charge directly. The electron injection efficiency is much higher than hole injection efficiency. Besides, the n-type region is larger at the bottom of the gate. Simultaneously, ${C}$ – ${V}$ measurement is also taken to prove the hypothesis.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Insight Into the Leakage Current Transport Mechanism Transformation in
           β-Ga2O3 SBDs Under Forward Bias Stress

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      Authors: Ailing Pan;Yingzhe Wang;Xuefeng Zheng;Yuehua Hong;Fang Zhang;Xiangyu Zhang;Ling Lv;Yanrong Cao;Xiaohua Ma;Yue Hao;
      Pages: 3185 - 3190
      Abstract: The electrical stress-induced increase in forward and reverse leakage current has been commonly observed in beta-gallium oxide ( $beta $ -Ga2O3) Schottky barrier diodes (SBDs). However, the transformation of the current transport mechanism during stress has not been investigated. Its correlation with defects in the devices has also not been established. In this work, the transformation of the current transport mechanism and the defect behavior for $beta $ -Ga2O3 SBDs during constant forward bias stress are investigated by the temperature-dependent current–voltage ( ${I}$ – ${V}$ – ${T}{)}$ and deep-level transient spectroscopy (DLTS) techniques, respectively. For the forward leakage current, the predominant transport mechanism transforms from thermionic emission (TE) to trap-assisted tunneling (TAT) after stress. The enhancement of TAT after stress is derived from a shorter tunneling path, which can be attributed to the generation of a shallow-level defect ( ${E}_{C}$ -0.2 eV), while for the reverse leakage current transport mechanism, the predominant transport mechanism transforms from Poole–Frenkel (PF) emission to TAT after stress. The ionization of newly generated shallow donors narrows the depletion region and reduces the distance of tunneling, which makes the carriers more likely to tunnel assisted by the defects in the stressed devices than thermally emitted.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Charge Trapping Layer Enabled Normally-Off β-Ga2O3 MOSFET

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      Authors: Minghao He;Kangyao Wen;Chenkai Deng;Mujun Li;Yifan Cui;Qing Wang;Hongyu Yu;Kah-Wee Ang;
      Pages: 3191 - 3195
      Abstract: In this work, a normally-OFF $beta $ -Ga2O3 MOSFET enabled by charge trapping layer (CTL) is demonstrated for the first time. The CTL consists of Al:HfO $_{x} 1$ :5 and the tunneling barrier (TB) is Al2O3/HfOx/Al2O3 stack. The developed Ga2O3 MOSFET exhibits a wide ${V}_{text {th}}$ tuning range to normally-OFF operation and a long-lasting retention characteristic of −0.3 V (ten years). The device obtains a breakdown voltage (BV) of 1815 V, showing high reverse blocking capability based on the proposed CTL technique. ${I}$ – ${V}$ and ${C}$ – ${V}$ analyses are carried out under various temperatures to study the mechanism and explore the charge trapping and de-trapping processes. The results indicate a promising method to achieve E-mode operation for Ga2O3 MOSFET with low charge loss and stable ${V}_{text {th}}$ .
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Sensitivity and Mechanism Study of Single-Event Burnout in 4H-SiC Devices
           With FLRs Termination

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      Authors: Keyu Liu;Xiaoyan Tang;Hao Yuan;Qingwen Song;Yancong Liu;Yu Zhou;Fengyu Du;Yuming Zhang;
      Pages: 3196 - 3201
      Abstract: The 4H-silicon carbide (SiC) junction barrier Schottky with field limiting rings (FLRs-JBS) termination was fabricated and analyzed to evaluate its radiation tolerance of the single-event burnout (SEB). Experimental and simulation results show that the SiC/SiO2/metal intersection is the most sensitive position in the FLRs-JBS. This work proposes that there are different mechanisms between the active and the terminal regions under heavy-ion irradiation for the first time. The simulation results show that the FLRs terminal area is more likely to burn out under single-event irradiation than the active area due to the serious current crowding effect. This work redefines the sensitive volume of the conventional FLRs-JBS under single-event irradiation, including the transition ring of the terminal zone, the part of the active area near the terminal zone, and the p+ island spacing of the active area.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Fabrication and Sintering Behavior of Nano Cu–Ag Composite Paste
           for High-Power Device

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      Authors: Weishan Lv;Jiaxin Liu;Yun Mou;Yongjie Ding;Mingxiang Chen;Fulong Zhu;
      Pages: 3202 - 3207
      Abstract: Cu and Ag nanoparticle (NP) paste has emerged as a promising choice for high-power devices because of its excellent thermal and electrical properties. However, easy oxidation, high sintering temperature of Cu NPs, high cost, and high porosity of Ag NPs restrict the practical application. Although Cu–Ag composite paste can improve bonding reliability, there have been no reports of fabricating stable and reliable Cu–Ag composite paste joints. In this work, we reported a novel method for fabricating a nano Cu–Ag composite paste with excellent dispersibility and relatively uniform particle size distribution via polyol one-step reduction. These composite NPs exhibit outstanding antioxidant capacity. The sintering behavior of the composite NPs at different temperatures was analyzed. The electrical and mechanical reliability of nano Cu–Ag composite paste joints with different ratios were investigated. With the increase in Ag content, the porosity and resistivity of the joint decrease, and the shear strength increases. The bonding joint presents a low porosity of 1.92% and a high shear strength of 32.6 MPa under a 1:3 ratio of Cu to Ag. The molecular dynamics (MDs) simulation results imply that Ag-rich composite system can achieve low-temperature sintering and maintain the stability of the sintering process.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Ab Initio Investigations of Gallium Nitride Nanoribbons for Spin Filter
           and Negative Differential Behavior

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      Authors: Neelesh Pratap Singh;Jayanta Ghosh;Neeraj K. Jaiswal;
      Pages: 3208 - 3214
      Abstract: This work demonstrates the influence of alternative edge passivation via H/F on the electronic and magnetic characteristics of gallium nitride nanoribbons (GaNNRs). For this study, the first-principles density functional theory (DFT) and non-equilibrium green function (NEGF) frameworks are deployed. Our study demonstrates that the selective edge passivation with F/H zigzag GaN nanoribbon (NR) is a strong contender for spintronics due to its half-metallic property under specific conditions. Various nano-configurations for the H/F ZGaNNRs passivation are investigated here. Thermodynamically, most stable configuration is alternate fluorinated F-GaN-F NR. Further, the negative differential resistance (NDR) behavior is also reported along with the perfect spin-filtering properties. This study paves the way to employ these 2-D nanostructures-based devices for spin filters, spin logic switches, and steep switching nanoelectronic devices.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Low-Frequency and Random Telegraph Noise in 14-nm Bulk Si Charge-Trap
           Transistors

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      Authors: Mariia Gorchichko;En Xia Zhang;Mahmud Reaz;Kan Li;Peng Fei Wang;Jingchen Cao;Rachel M. Brewer;Ronald D. Schrimpf;Robert A. Reed;Brian D. Sierawski;Michael L. Alles;Jonathan Cox;Steven L. Moran;Subramanian S. Iyer;Daniel M. Fleetwood;
      Pages: 3215 - 3222
      Abstract: Effects of programming/erasing (P/E) and total-ionizing dose (TID) are investigated on 2- and 40-fin charge-trap transistors (CTTs) fabricated in a 14-nm bulk-Si CMOS technology. Significant random telegraph noise (RTN) is observed in as-processed CTTs, especially for 2-fin devices. Trapped charge in programed devices does not significantly affect 1/ ${f}$ noise magnitudes, but P/E leads to trap activation/deactivation, causing changes in border-trap energy and spatial distributions. TID irradiation activates a large number of stable radiation-induced traps.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Highly Integrated, High-Sensitivity Magnetometer Based on Diamond
           Nitrogen-Vacancy Centers

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      Authors: Guihao Ran;Zichuan Zhang;Kun Huang;Lin Cheng;Shuai Qu;Qieyu Huang;Xiaobiao Mao;
      Pages: 3223 - 3227
      Abstract: Solid-state quantum sensing technology based on diamond nitrogen-vacancy (NV) centers has become a powerful tool for magnetic field detection and has great promise for applications. However, the environmental requirements and bulky instrumentation associated with optically detected magnetic resonance (ODMR) measurement methods need to be avoided in practical applications, and the magnetometric sensitivity of the system needs to be further improved. In this article, we propose a high-precision integrated portable magnetometer (HIPM) with a volume limit of 150 cm3. The system integrates larger equipment and bulky instruments, which greatly improves the integration of the system, and also designs the corresponding signal conditioning circuit (SCC) to process the fluorescence signal, which ensures the integration of the system and makes the sensitivity improved. In addition, according to our test comparison, the interference between microwave (MW) signal and SCC is effectively and strongly shielded during the experiment, which is a guideline for the future integration design. Subsequently, we verified that the magnetic sensitivity of the system is about 16.03 nT/Hz $^{{1}/{2}}$ . This new sensing system has a high level of integration and possesses good magnetometric sensitivity.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Low-Frequency Noise of 4H-SiC CMOS Technology for Analog ICs

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      Authors: Masahiro Masunaga;
      Pages: 3228 - 3233
      Abstract: To design low-noise analog ICs for nuclear power plants, low-frequency noise (LFN) of 4H-SiC CMOS technology was studied in the frequency range of 3 Hz–10 kHz at room temperature. The LFN of the long-channel MOS devices was systematically studied in terms of gate length, gate width, drain current, and drain voltage. It was found to follow the noise model for carrier number fluctuation regardless of conduction type. In addition, the standard deviation of spectral noise density ( ${S}_{text {id}}$ ) at 10 Hz for the p-channel MOS was experimentally found to be $4.6times $ larger than that for the n-channel MOS. This was caused by the increase in random telegraph noise (RTN) caused by oxide hole traps with nitrogen incorporation at the SiO2/SiC interface. The flicker noise coefficient (KF) in the noise model was estimated to be ${4.1} times {10}^{-{26}}$ and ${1.2} times {10}^{-{27}},,text{s}^{text {1-EF}}text{A}^{text {2-AF}}text{F}^{^{^{^{}}}}$ for the n- and p-channel MOS, respectively.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • One-Dimensional Sulfur Nanowires: A Potential n-Type Material of Channel
           Used in Sub-5-nm Transistors

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      Authors: Xingyi Tan;Qiang Li;Dahua Ren;
      Pages: 3234 - 3238
      Abstract: Materials with low dimensionalities have been presented as new choices of field-effect transistors (FETs), whose channel materials are based on silicon to eliminate the restriction related to scaling. An approach called ab initio quantum transport is employed to simulate a gate-all-around (GAA) sulfur nanowire (NW) FETs. The GAA sulfur FETs having a gate length ( ${L}_{g}$ , where ${L}_{g}$ taking 5, 3, and 1 nm) and a suitable underlap (UL) could gratify the current of ON-state ( ${I}_{ mathrm{ON}}$ ), power dissipation (PDP), and delay period ( $tau $ ) concerning the needs of 2028 to achieve higher performance (HP) and a lower dissipation (LP) request of International Technology Roadmap for Semiconductors (ITRS) in 2013. Therefore, the GAA sulfur FETs can be a latent choice for scaling Moore’s law downward to 1 nm.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Enabling Scalable, Ultralow-Voltage Flexible Organic Field-Effect
           Transistors via Blade-Coated Cross-Linked Thick Polyvinyl Alcohol Gate
           Dielectric

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      Authors: Huaijie Fu;Jinlei Peng;Liuzhi Xiang;Qiaoming Zhang;Xingwen Tan;Yanlian Lei;
      Pages: 3239 - 3244
      Abstract: A scalable ultralow-voltage flexible organic field-effect transistor (OFET) design has been accomplished through utilization of a blade-deposited thick cross-linked polyvinyl alcohol (c-PVA) dielectric. This blade-deposited thick c-PVA dielectric film is capable of suppressing device leakage, enabling high-performing OFETs with benchmark electrical properties of ultr- alow operation voltage (< 1 V), high field-effect mobility close to 10 cm2/ $text{V}cdot text{s}$ , and excellent subthreshold swing < 100 mV/decade. In addition, the OFETs with blade-deposited c-PVA gate dielectric have exhibited excellent mechanical stress stability, with only minimum performance degradation after 2 h of static bending or $10^{{3}}$ cycles of bending. These results will enable realization of a simple low-cost manufacturing process for high-performance, low-voltage flexible OFETs for a great variety of organic electronics.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Synaptic Transistor Arrays Based on PVA/Lignin Composite Electrolyte Films

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      Authors: Wenkui Zhang;Jun Li;Lian Cheng;Wenhui Shi;Yuxing Lei;Shengkai Wen;Fei Wang;Jiewei Jiang;Pan Wen;Jianhua Zhang;
      Pages: 3245 - 3250
      Abstract: With the development of information society, the traditional von Neumann-based computing system is facing significant challenges. The search for an intelligent computing system similar to the biological brain would be a very effective solution to the present-day von Neumann bottleneck. Electrolyte-gated transistors (EGTs) have received much attention because they can simulate biological synaptic behavior very effectively. However, large-scale EGTs arrays are still lacking because most of the existing reported EGTs use organic or liquid electrolytes, which poses a significant challenge to the current production methods for manufacturing integration using photolithography. Although synaptic transistor arrays using solid-state electrolytes have the potential for large-scale fabrication, the power consumption required for individual transistors is relatively high. In this work, an electrolyte transistor array ( $10times10$ ) fabricated by the photolithography process was successfully proposed, where the individual transistors in the array used a composite polyvinyl alcohol (PVA)/lignin electrolyte as the gate dielectric layer. The switching ratio of a single transistor can reach 106, and the maximum gate leakage current is 43.96 pA in the voltage range of −3 to 3 V. In addition, the synaptic properties, such as excitatory postsynaptic current (EPSC) and paired-pulse-facilitation (PPF), were successfully achieved. When the pulse duration is 100 ms, the energy consumption of the transistor is 0.63 nJ. The number’s dynamic memory and forgetting functions were also successfully simulated by the artificial synaptic transistor array. This work will provide a useful idea for large-scale array integration of EGTs using organic and liquid electrolytes as gate dielectric layers.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Effective Coercive Field of PMN-PT Single Crystal Inside a Curved Array
           Ultrasonic Transducer at High Frequencies

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      Authors: Lian Cui;Wenwu Cao;
      Pages: 3251 - 3254
      Abstract: The effective coercive field ${E}_{text {c}}^{text {eff}} $ has been investigated as a function of frequency ${f}$ from 10 kHz to 4 MHz for [001]c poled 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-0.29PT) single crystals inside an ultrasonic curved array transducer. The results show that ${E}_{text {c}}^{text {eff}} $ monotonically increase with ${f}$ in the form of ${f} ^{beta }$ , reached more than 6 kV/cm at 4 MHz, which is three times of conventionally defined coercive field (~2 kV/cm). The $beta $ value changes at about 400 kHz due to the transition from non-180° domain switching to 180° domain switching. Our results showed that the ${E}_{text {c}}^{text {eff}} $ of PMN-0.29PT single crystals under clamped boundary conditions is larger than that of under free boundary conditions, which revealed the fact that strain confinemfent hinders domain switching in ferroelectric crystals. These quantitative results of ${E}_{text {c}}^{text {eff}} $ versus ${f}$ can provide very useful guidelines for the design of high-frequency medical array transducers using PMN-PT single crystals.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • A Dynamic Concentration-Dependent Analytical I,–V Model for LG-GFET
           Biosensor

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      Authors: Yunqiu Wu;Tao Xu;Ke Jiang;Duoduo Lv;Ying Shi;Hong Tang;Chenxi Zhao;Yiming Yu;Huihua Liu;Yuehang Xu;Kai Kang;
      Pages: 3255 - 3262
      Abstract: In the past few years, liquid-gated graphene field-effect transistors (LG-GFETs) have been widely used in biological detection due to their unique advantages. An accurate transistor model is the basis of biological detection circuit design, however, the reported GFET models are mainly focusing on solid-gated GFETs. Therefore, it is essential to conduct the research on LG-GFET model. In this article, an improved ${I}$ – ${V}$ model of LG-GFET is presented based on Fregonese’s model. An improved electric double-layer capacitor model is proposed for LG-GFET. Then, the relationship among iron concentration, bias voltages, and current is studied comprehensively. Furthermore, the drain current response change with time is taken into account and the dynamic concentration-dependent model is established. To verify the accuracy of the proposed model, LG-GFET is simulated in TCAD software and fabricated to perform the measurement. The simulation results and measurement results are compared with the model results, respectively. These results show that the relative root-mean-square error (RMSE) to both simulation and measurement results is less than 5.7%. It is revealed that the proposed model can be applied to biological detection and achieve high accuracy.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Highly Linear RMS Microwave Power Sensor Joule-Heating-Based Using CMOS
           Technology

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      Authors: Jian-Hua Li;Xiaoping Liao;
      Pages: 3263 - 3268
      Abstract: This article presents the design and implementation of a high-power handing capacity, wideband, and excellent microwave-dc linearity root-mean-square (rms) microwave power sensor (PS) in 180-nm standard RF CMOS technology. The detection technique utilizes two well-matched microwave power absorbers and a balanced Wheatstone full bridge (WFB) with thermistors to produce a dc output proportional to incident microwave power. The lateral spacing between the hot and cold zones of WFB with 80, 100, 120, 140,and $160 {mu }text{m}$ has been investigated experimentally, which provides insight into the proper adjustment of the layout parameters. The experimental result of the vector network analyzer (VNA) shows that the input reflection loss is less than −22.3 dB in the frequency range of 0–20 GHz. This indicates that the designed microwave PSs have good impedance matching characteristics. Moreover, it is demonstrated that the inherent linear relationship between the output dc voltage and the incident microwave power is less than 1.6% over a dynamic range of 1–500 mW. The proposed microwave PS can be further integrated in ${X}$ -band RF transceivers, offering high microwave-dc linearity, acceptable sensitivity, small size, and low cost for improving power transfer efficiency and optimizing the performance of the transmitting and receiving chain.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Analysis of Near-Field Thermophotovoltaic Devices Using
           Graphene–Germanium Schottky Cell

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      Authors: Zhimin Yang;Jaeman Song;Bong Jae Lee;
      Pages: 3269 - 3274
      Abstract: In this work, we investigate the performance of graphene-based Schottky junction thermophotovoltaic (TPV) devices in near-field conditions. Despite the low cost and excellent photoelectric properties of graphene, earlier studies have focused primarily on the contribution of the graphene layer to the photocurrent, assuming an internal quantum efficiency (IQE) of 100%. Our numerical model of a graphene/germanium Schottky junction TPV device reveals that the semiconductor layer predominates in the generation photocurrent, with an IQE of graphene less than 40%. We also evaluate the photocurrent densities generated by the semiconductor and graphene at an emitter temperature of 1000 K and a vacuum gap of 100 nm. Results show that using an indium tin oxide (ITO)-covered tungsten (W) emitter can increase photocurrents by a factor of around 10 and 11 for the semiconductor and graphene, respectively. Additionally, using a hyperbolic metamaterial (HMM) emitter can enhance photocurrents by around 4.7 and 5.2 times for the semiconductor and graphene, respectively. However, this comes at the cost of higher heat flux from the HMM emitter. Our findings will provide valuable insights for the design and optimization of TPV devices to improve their photocurrent and efficiency.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Reduced Graphene-Oxide-Based Silk-FET: A Facile Platform for Low Power and
           Room Temperature Detection of Formaldehyde

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      Authors: Lisa Sarkar;Avik Sett;Santanab Majumdar;Tarun Kanti Bhattacharyya;
      Pages: 3275 - 3281
      Abstract: This article demonstrates the potential of silk film as gate dielectric in FET-based gas sensor. L-ascorbic acid (LAA) reduced graphene oxide (rGO) was used as semiconducting channel which acts as the sensing layer of the FET-based sensor. The morphology and capacitance of silk film were investigated to introspect two seldomly explored quantities: porosity and dielectric constant. The measured dielectric constant of silk film lies in the range of 32–13 in the low-frequency regime (40–100 Hz). Silk film also exhibited uniform, nonporous, smooth morphology. The Silk-FET device exhibited selective response toward formaldehyde (HCHO) among seven volatile organic compounds (VOCs), and rGO ensured room temperature sensing. During the adsorption of formaldehyde, electrons’ transfer takes place from formaldehyde to rGO, reducing the hole concentration of the channel. This leads to reduction in output current, revealing p-type characteristics of the device. The transfer and output characteristics also exhibited similar p-type nature. Device’s threshold voltage shift is also prominent with the exposure to formaldehyde. The gate bias played a pivotal role in improving the device performance. At 1.15-V gate voltage, the response was enhanced by 2.8 times for 45-ppm formaldehyde. The device exhibited maximum response at a gate voltage of 1.15 V, ensuring low-power operation of the FET device. The device’s response and recovery time were calculated as 97 and 280 s, respectively, at 180-ppm formaldehyde. The sensing behavior of the system was also reaffirmed through the TCAD SILVACO simulations. The energy band diagram revealed the depletion of carriers at rGO with adsorption of formaldehyde.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Design and Experiments of a 0.66-THz Short-Pulse TE14,5 Mode
           Second-Harmonic Gyrotron

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      Authors: Tao Song;Xu Qi;Taotao Mao;Chen Zhang;Jie Huang;Peisheng Liang;Aiqin Wang;Jiao Jiao;Na Yao;Kaichun Zhang;Xiaoqiuyan Zhang;Tao Zhao;Zhenhua Wu;Min Hu;Yanyu Wei;Yubin Gong;Wei Wang;Diwei Liu;
      Pages: 3282 - 3287
      Abstract: Experimental investigations on a 0.66-THz gyrotron have been accomplished. Meanwhile, the magnetic injection gun and the gyrotron beam–wave interaction cavity are designed and optimized. The gyrotron cavity is a traditional three-section cavity. The experimental results demonstrate that this gyrotron is under the stable operation of the second cyclotron harmonic. The operating mode is TE $_{text {14, {5}}}$ mode and the pulselength is $80 mu text{s}$ . By tuning the beam energy and the operating magnetic field, the maximum frequency of this gyrotron reaches 656.95 GHz and the output power is up to 282 W. Furthermore, this gyrotron can be utilized as a frequency-tunable source, the frequency-tunable range is about 70 MHz. This gyrotron is specially designed to meet the requirement of the experiment of irradiating THz waves on living bodies.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Simulation Study on a Planar Quasi-Optical Waveguide Circuit for a W-Band
           Gyro-TWT With Stability Improvement

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      Authors: Yelei Yao;Yibin Sun;Xinge Dai;Guo Liu;Jianxun Wang;Yingjian Cao;Wei Jiang;Yong Luo;
      Pages: 3288 - 3294
      Abstract: In this article, a planar quasi-optical waveguide (PQOW) circuit is proposed for vacuum electron devices (VEDs) for the first time. The circuit is made of a series of metamaterial pillars attached to a pair of parallel plates for phase compensation. It can propagate quasi-optical modes as a pair of concave mirrors does, while the lower order HE $_{{0}{n}}$ modes experience much heavier circuit loss compared to that of convention confocal waveguide circuits, which can improve the backward oscillation (BWO) stability of gyro-amplifiers. As an example, a W-band gyro-amplifier with PQOW circuits to replace conventional confocal circuits is designed. The 3-D particle-in-cell simulation demonstrated that the circuit is capable of producing stable high-power radiation within 96–108 GHz, with an electron efficiency of about 15% over the entire bandwidth.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Half-Height Pin Gap Waveguide-Based Slow-Wave Structure for Millimeter
           Wave Traveling-Wave Tubes

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      Authors: Amira Zied Abozied;Jonathan Gates;Rosa Letizia;
      Pages: 3295 - 3301
      Abstract: The design of a ${W}$ -band traveling-wave tube (TWT) power amplifier based on a groove gap waveguide (GW) slow-wave circuit is presented in this article. The technology of GW is analyzed to aid the design of electromagnetic band gap-based slow-wave structures (SWSs) in the upper millimeter wave range of the spectrum while alleviating some of the typical fabrication challenges at these frequencies. The results of particle-in-cell (PIC) simulations numerically demonstrate a 10-GHz instantaneous 3-dB bandwidth in the range 89–99 GHz with a minimum power gain of 25 dB. A prototype of the complete SWS is manufactured via computer numerical control (CNC) machining and measured to verify the cold simulation results. Machining tolerances and surface roughness are also investigated. The design approach via groove GW is flexible and can be extended to alternative rectangular waveguide-based SWSs.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Transparent Flat Panel X-Ray Source Using ITO Transmission Anode and ZnO
           Nanowire Cold Cathode

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      Authors: Song Kang;Yicong Chen;Chengyun Wang;Guofu Zhang;Shaozhi Deng;Jun Chen;
      Pages: 3302 - 3307
      Abstract: X-ray sources have important applications in medical diagnosis, industrial inspection, etc. Transparent X-ray source has not been reported before, which enables the applications such as simultaneous imaging using X-ray and visible light. In this article, a fully vacuum-encapsulated transparent flat-panel X-ray source was prepared by using ZnO nanowires cold cathode and indium-tin-oxide (ITO) transmission anode. The effect of thicknesses of ITO film on X-ray radiation intensity was studied. A radiation dose rate of 6.85 mGy/s measured at 5 cm in front of the flat-panel X-ray source (FPXS) under 48-kV anode voltage and an optical transmittance of 72.63% at 550-nm light were achieved. X-ray spectra show the indium is the main element to generate the X-ray. By adopting the device in an X-ray and visible light dual-functional inspection set-up, the X-ray and visible light imaging of objects were demonstrated simultaneously.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Inverse-Cherenkov Dielectric Laser Accelerator With a Prism-Slab Structure
           Driven by Single-Side Laser

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      Authors: Liwen Zhang;Weihao Liu;Qika Jia;Hongliang Xu;Yalin Lu;
      Pages: 3308 - 3314
      Abstract: The dielectric laser accelerator (DLA) based on the inverse Cherenkov effect (ICR) is one of the promising options for developing next-generation desktop or even ON-chip particle accelerators. In order to realize efficient acceleration and to counteract bunch deflection in the tiny-size bunch channel, especially in the subrelativistic region, the available inverse-Cherenkov DLAs exclusively resort to the double-side driven scheme, which uses two identical laser beams to simultaneously and symmetrically drive a mirror dual-prism structure. This complicates the optical system and increases the difficulty of implementation in practice. Here we propose a novel inverse-Cherenkov DLA scheme that uses a single-side laser beam to drive a dielectric prism-slab structure. The laser-induced fields are reflected on both sides of the dielectric slab, which changes the field distribution in the bunch channel. By properly choosing the thickness of the slab and the laser wavelength, the fields in the bunch channel can be symmetrically distributed, which is just like that in the double-driven scheme. So the single-side driven model can realize the same acceleration gradient and focusing effects as the double-driven scheme, which doubles the acceleration efficiency and simplifies the optical system in practice. Detailed theoretical analyses are performed, the results of which are verified by full-field and particle-tracking simulations. This proposed scheme is of significance for developing miniaturized inverse-Cherenkov DLAs.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Mode Distortion and Performance Degradation Caused by Electron-Beam
           Misalignment in W-Band Gyro-TWTs

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      Authors: Yu Wang;Guo Liu;Yingjian Cao;Weijie Wang;Wei Jiang;Yelei Yao;Jianxun Wang;Yong Luo;
      Pages: 3315 - 3321
      Abstract: Mode distortion and performance degradation caused by an OFF-axis gyrating electron beam in our W-band gyrotron traveling wave tube (gyro-TWT) were studied by the particle-in-cell (PIC) simulation and verified with the hot test experiments. The simulated electron beam misalignment may lead to a mixed pattern, mainly composed of TE01, TE02, TE21, and TE22 modes. They will further deteriorate the performance by disturbing the bunched electron beam. When the misalignment is over 0.1 mm, the operating mode shows a significant distortion, and the output power is reduced to 66% of that without misalignment at 93 GHz. For the prototype gyro-TWT with an estimated beam misalignment of about 0.1 mm, the measured saturated output power drops by more than 57% below 93.5 GHz compared with the normal one, whose estimated misalignment is less than 0.05 mm. The downward trend proves that the beam misalignment is the main factor causing the performance degradation at the W-band and above.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Demonstration of Artificial Afferent Nerve Properties With Forming-Free
           and SiO2-Based Memristive Synapses

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      Authors: G. Kleitsiotis;P. Bousoulas;C. Tsioustas;D. Tsoukalas;
      Pages: 3322 - 3328
      Abstract: The development of artificial nerve systems is considered of great significance for the fabrication of artificial appendages or intelligent robotics with environmental communication and awareness. Along these lines, in this work, the synaptic properties of a SiO2-based conductive bridge random access memory (CBRAM) were thoroughly investigated. Initially, a detailed study was conducted to understand and catalog the short- and long-term properties of the device, and their underlying physical mechanisms. To that end, a numerical model was introduced for interpreting the synaptic pattern within the device and its results were validated with the acquired experimental data. In addition, an artificial afferent nerve concept was demonstrated, comprising a piezoelectric sensory receptor, to generate electrical signals in response to either impulsive (“touch and go”) or continuous external stimuli (“touch and stay”), a microcontroller-emulated leaky-integrate-and-fire neural node converting the signals into spiking action potentials, and the CBRAM element as a terminal synapse, responsible for processing/attenuating the action potentials Throughout these procedures, the synaptic adaptation and the memory consolidation processes were recorded and analyzed.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Phase Change Behavior of Si/Sb Superlattice-Like Thin Film on a Flexible
           Substrate

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      Authors: Cheng Wang;Yifeng Hu;
      Pages: 3329 - 3334
      Abstract: As an important part of flexible electronic devices, high-performance and flexible memory is essential for the further development of integrated circuits. In this article, Si/Sb superlattice-like (SLL) films with different components were prepared on flexible polyether ether ketone (PEEK) substrates, and their phase transition performance was verified by an in situ heating station. After 104 bending cycles, the film still achieved an effective amorphous–crystalline transition with a small resistance fluctuation. The multiple bending made the surface texture of the flexible film more ordered as well as a smaller surface roughness. The bending also resulted in refined grains and higher crystalline resistance. Phase change memory (PCM) device cells with Si/Sb SLL films on PEEK substrates were fabricated. A reversible operation of RESET and SET could be achieved with over two orders of magnitude difference between high and low resistances. All these experimental results showed that Si/Sb SLL films with PEEK as the substrate had promising applications in flexible memories.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Research on Photothermal Co-Analysis Model of a
           Thermoelectric–Photoelectric Power Generator

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      Authors: Min Sun;Xiaoping Liao;
      Pages: 3335 - 3340
      Abstract: In this article, a novel co-analysis model for photovoltaic and thermoelectric is proposed. A newly developed experimental platform is presented to verify the theoretical results of the model. The manufacturing process of the integrated power generator is compatible with the CMOS process and MEMS technology. All analyses are based on the premise that light and heat act simultaneously on the integrated power generator. The modeling of the thermoelectric generator (TEG) shows that the imposition of sunlight will impact its output performance. The reason is that one portion of the solar energy will be converted into heat for the cold side of the thermal leg. Hence, a new structure of the TEG, which has longer thermal legs to reduce the area of the cold side, is tested in the experiment. The experimental results show that the output voltage per area of the thermocouple decreases linearly from 1.625 to 0.344 mV/cm2 with light enhancement when the temperature of the bottom is 60.25 °C. In the Section of the solar cell, the output performance remains relatively stable when the temperature of the chip varies.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Memcapacitive to Memristive Transition in
           Al/Y2O3/GZO Crossbar Array

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      Authors: Sanjay Kumar;Mohit Kumar Gautam;Saurabh Yadav;Shaibal Mukherjee;
      Pages: 3341 - 3346
      Abstract: Here, we report both memcapacitive and memristive behaviors in a $text{Y}_{{2}}text{O}_{{3}}$ -based crossbar array size of ( $4times4$ ), which is fabricated by utilizing dual ion beam sputtering (DIBS) system. The fabricated crossbar array shows the memcapacitive behavior under the application of lower input voltage, while under the comparatively higher input voltage, it shows memristive behavior in switching response. Moreover, the transition from memcapacitive to memristive behavior is stable and reversible in nature and depends on the amplitude of the applied input voltage. The crossbar array devices show stable switching response in multiple switching cycles, excellent endurance (80 000 cycles) and retention ( $12times 10^{{3}}$ s) properties, low device-to-device (D2D), and cycle-to-cycle (C2C) variabilities in device switching voltages, i.e., ${V}_{text {SET}}$ and ${V}_{text {RESET}}$ . The synaptic functionalities are demonstrated in terms of potentiation (P) and depression (D) mechanisms and achieve least value of nonlinearity factor, i.e., 0.05 under the lower input voltage (1 V), wherein memcapacitive behavior is dominated.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Dual-Junctions Field Effect Transistor Based on
           MoS2/Te/MoS2

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      Authors: Kai Zhang;Sina Li;Jianru Chen;Lingyu Zhu;Yiming Sun;Jingbo Li;Nengjie Huo;
      Pages: 3347 - 3353
      Abstract: In the applications of low-power device design and large-scale integrated circuit, MOSFETs play an important role but suffer from the doping complexity and short channel effect when the technology node is further shrinking. Thus, it is of great interest to develop new transistor architecture with atomically thin channel materials to meet the demand for high-density integration and low-power consumption electronics. Here, we develop a dual-junctions field-effect transistor (DJFET) consisting of van der Waals MoS2/Te/MoS2 heterojunctions where the MoS2 on top and bottom serves as dual-gate and the tellurium (Te) in middle is the carrier transport channel. The novel transistor exhibits superior transfer and output characteristics with p-type behavior, high mobility of 270.3 cm $^{{2}}text{V}^{-{1}}text{s}^{-{1}}$ and large transconductance of $16.4~mu text{S}$ , competing with widely-reported MOSFETs based on 2-D semiconductors. Additionally, the devices can be operated as a self-driven photodetector with a high responsivity of 879.2 mAW $^{-{1}}$ and a specific detectivity of $3.47times 10^{{11}}$ Jones. This work proposes a new dual-junctions transistor as a highly desirable candidate for next-generation electronic applications.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Improvement of Rectification Characteristics of TaOx/Al2O3 Memristors by
           Oxygen Anion Migration and Barrier Modulation

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      Authors: Zexia Ma;Fang Wang;Xin Shan;Xin Lin;Yupeng Zhang;Xiaowei Guo;Wanning Liu;Yemei Han;Xuanyu Zhao;Zhitang Song;Kailiang Zhang;
      Pages: 3354 - 3359
      Abstract: As we all know, when memories are integrated into arrays on a large scale, the phenomenon of current leakage may occur, which leads to array crosstalk. The selection of memristors with self-rectifying effects can be used to solve crosstalk problems without adding additional device cells, allowing for a higher level of array integration under the same conditions. In this article, by optimizing the thickness of the Al2O3 switching layer in the Au/TaO $_{{text {x}}}$ /Al2O3/TiN self-rectifying memristor (SRM), it is found that the rectification ratio can reach $sim $ 403.79 and the nA level of sneak current can be achieved. The fitting analysis shows that the self-rectification phenomenon related to the thickness of Al2O3 may be related to the effective Schottky barrier between Au/TaO $_{{text {x}}}$ and TaOx/Al2O3 layers and the tunneling effect with increasing voltage. Under the premise of a 10% read margin (RM), it is calculated that the size of the passive array can reach ${N}$ = 1425. Changing the thickness of the switching layer in the SRM of the stacked structure can significantly improve the rectification effect, thereby increasing the adaptive scale of the array. Our work provides a feasible path for the subsequent optimization of SRMs, which effectively promotes the development of high-density integrated arrays.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • The Analysis of Multiwall Carbon Nanotubes as Through Silicon Via by
           Equivalent Circuit Model at Different Operating Temperatures in
           Multilayers Stacking Scheme

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      Authors: Y. -C. Chan;Nilabh Basu;T. -W. Chen;Y. -T. Tsai;H. -Y. Lin;S. -C. Chen;M. -H. Lee;M. -H. Liao;
      Pages: 3360 - 3364
      Abstract: In nowadays 3-D integrated circuits (3DICs) technology, through silicon via (TSV) is the most important component, which connects homogeneous or heterogeneous dies vertically with each other. Based on our previous research, carbon nanotubes (CNTs) have been considered as TSV filling materials due to their outstanding mechanical and electrical properties. However, the operating temperatures would significantly affect the performance of signal transmission in CNT TSV. To evaluate the electrical characteristics of CNT TSV with different realistic temperatures, the considerations of temperature-dependent electron mean free path (MFP, $lambda$ ), and number of conducting channels of CNTs are necessary. In this work, the equivalent circuit model of CNTs as TSV is presented and the simulated electrical behaviors are benchmarked with other literatures. Based on our proposed model, multiwall (MW) CNTs’ electrical performance in multilayers stacking system under different operating temperatures is investigated. In addition, we also compare the electrical performance of CNTs as TSV with the conventional filling material (Cu). It shows that CNT TSV has more advantages than Cu TSV when the operating temperature becomes higher. In summary, the proposed equivalent circuit model in this work is more comprehensive and yields more realistic results. Meanwhile, CNT is a promising material for TSV under varying operation temperatures.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Physical Insights of Si-Core-SiGe-Shell Gate-All-Around Nanosheet pFET for
           3 nm Technology Node

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      Authors: Haoqing Xu;Jiaxin Yao;Zhizhen Yang;Lei Cao;Qingzhu Zhang;Yongliang Li;Anyan Du;Huaxiang Yin;Zhenhua Wu;
      Pages: 3365 - 3371
      Abstract: This article presents a physics-based simulation study of a Si-core-SiGe-shell gate-all-around (GAA) nanosheet FET (NSFET). The numerical simulations employ various models including 1) an elastic model for lattice mismatch-induced stress in the core/shell structure; 2) the ${k}cdot {p}$ method with a Poisson solver for the electrostatics; 3) Kubo-Greenwood model for low-field mobility calculation with surface roughness fit with experimental results; and 4) multi-subband Boltzmann transport equation (SBTE) for the high-field transfer characteristics. The study evaluates the effect of channel/wafer orientation, Ge component ratio ${x}$ in SiGe-shell region, core thickness ${T} _{text {core}}$ , and surface roughness on electrostatics and transport properties. The Si/SiGe core/shell structure can be an additional performance knob for advanced technology node beyond 3 nm due to the following key physics: 1) thin SiGe-shell region with a high Ge component ratio tends to exhibit higher compressive stress in the shell region due to lattice mismatch; 2) holes are mainly confined in the SiGe-shell region under compressive strain at ON-state, leading to a significant enhancement in ${I} _{ mathrm{ON}}$ for pMOS devices; and 3) core/shell devices exhibit lower hole density at OFF-state in the channel compared with Si-channel device, resulting in current leakage reduction. Finally, the proposed Si-core-SiGe-shell pMOS device achieves a 30.5% enhancement of ${I} _{ mathrm{ON}}$ at ${T} _{text {c-re}}= {3}$ nm and ${x}$ = 0.1, and two orders of magnitude higher ON- OFF ratio at ${T} _{text {core}}$ = 2 nm and ${x}$ = 0.1, compared to the single Si-channel pMOS device. The results suggest that the proposed core-shell structure is a potential candidate for 3-nm node pMOS and beyond.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Fully Ferroelectric-FETs Reservoir Computing Network for Temporal and
           Random Signal Processing

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      Authors: Mingfeng Tang;Junyao Mei;Xuepeng Zhan;Chengcheng Wang;Junshuai Chai;Hao Xu;Xiaolei Wang;Jixuan Wu;Jiezhi Chen;
      Pages: 3372 - 3377
      Abstract: Reservoir computing (RC), a derivation of recurrent neural networks (RNNs), is an energy-efficient computational framework suitable for temporal signal processing. Owing to the short-term and long-term memory capability, the ferroelectric field-effect transistor (FeFET) is regarded as a promising hardware component for implementing RC networks. This article aims to optimize the fully FeFETs RC network by evaluating the recognition accuracy in various classification tasks, which includes the operating voltage sequence, device numbers as well as connection methods. The physical random telegraph noise (RTN), working as an ideal temporal and random signal, is investigated and extended by using the optimized fully FeFET RC network, resulting in a rapid time constant extraction method. Our findings may provide the broad potential for hardware security and cyber security based on the fully FeFET RC network.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Driving Strategy Based on Artificial Neuron Device for Array Circuits

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      Authors: Zhengxian Zhou;Xianghong Zhang;Weixi Ye;Di Liu;Yongjie Lin;Jiaming Lin;Tailiang Guo;Huipeng Chen;
      Pages: 3378 - 3381
      Abstract: Over the past many years, array circuits, as an important part of electronic systems, show a wide range of application scenarios. However, the pursuit of high-density array circuits will certainly lead to a steep increase in the area of the array driving circuit. In this article, we present a switching array circuit with an artificial neuron, where the neuron acts as a discrete control center for the array circuit, which can effectively reduce the area of the array driving circuit by 75%. In this work, we found that the value of load resistance can affect the switching of individual devices and control the branch threshold voltage range, thus affecting the information processing capability of the branch. This new paradigm of optimized array circuit driving strategy can be used to tune the set and reset threshold voltage of neurons, while processing and outputting information by using this type of configuration. This work provides a potential platform for promoting the development of electronic devices and future high-density array circuits.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Metal–Ferroelectric–Semiconductor Tunnel Junction: Essential Physics
           and Design Explorations

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      Authors: Ning Feng;Hao Li;Baokang Peng;Fangxing Zhang;Puyang Cai;Lining Zhang;Runsheng Wang;Ru Huang;
      Pages: 3382 - 3389
      Abstract: The essential physics of the ferroelectric tunnel junction (FTJ) is assessed with technology computer-aided design (TCAD) simulations and analytical models. With experimental data calibrations, a TCAD simulation framework including electrostatic potentials, ferroelectric (FE) polarizations, and nonlocal tunneling is built. Full regions of the FTJ operations, including the read/write, are then explored. Key parameters such as the memory state threshold voltages ( ${V}_{text {mth}}$ ) and the region boundary voltages are defined, and their model formulations are developed. With the essential physics captured, FTJ figure-of-merits (FoMs) are accessed with not only tunneling electroresistance (TER), but also power consumption. Design parameters from FE layer thickness, polarizations, and coercive field to silicon doping and metal work functions are studied, with their impacts on key FTJ FoMs evaluated.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Study of Electrical Characteristics for Dual-Gate TFTs With Asymmetric
           Defect Distributions and Gate Work Functions

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      Authors: Chih-Chieh Hsu;Jin-Xian Li;Po-Cheng Huang;Wun-Ciang Jhang;Mojtaba Joodaki;
      Pages: 3390 - 3393
      Abstract: Combined effects of asymmetric defect distributions and asymmetric gate work functions (WFs) on the performances of self-aligned dual-gate poly-Si TFTs are investigated. Normally, small grains with plentiful grain boundaries (GBs) or other structural defects appear at different positions of the poly-Si film, which is dependent on the growth process of the film. Subgap states of acceptor-like tail, acceptor-like deep-level, donor-like tail, and donor-like deep-level states are used to emulate the defects. Two sets of density of states (DOS) are employed. We find that defects at different positions of the source-side and drain-side channels exhibit different influences on TFT performance and the influences are dependent on the WFs of the gates. TFTs with a higher gate WF can have a higher tolerance to the depth of the defect region. Besides the electrical characteristics, the combined effects of defects and gate WFs on current density distributions and electric field distributions in the channel regions are explored. The performance variations caused by the asymmetric defects along with asymmetric gate WFs can be explained.
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power
           Applications

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      Pages: 3394 - 3395
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
  • TechRxiv: Share Your Preprint Research with the World!

    • Free pre-print version: Loading...

      Pages: 3396 - 3396
      PubDate: June 2023
      Issue No: Vol. 70, No. 6 (2023)
       
 
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