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Journal Cover physica status solidi (c)
  [SJR: 0.471]   [H-I: 31]   [1 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642
   Published by John Wiley and Sons Homepage  [1597 journals]
  • HgCdTe p+‐n structures grown by MBE on Si (013) substrates for high
           operating temperature SWIR detectors
    • Authors: V. M. Bazovkin; S. A. Dvoretskiy, A. A. Guzev, A. P. Kovchavtsev, D. V. Marin, Z. V. Panova, I. V. Sabinina, Yu. G. Sidorov, G. Yu. Sidorov, A. V. Tsarenko, V. S. Varavin, V. V. Vasiliev, M. V. Yakushev
      Abstract: Electrophysical properties of multilayered heteroepitaxial structures of Hg1‐xCdxTe with x=0.3‐0.4 grown by molecular beam epitaxy on silicon substrates are presented. The passivating effect of thin CdTe layers grown on top of the structures in single process is demonstrated. Comparison between experimental and theoretical temperature dependencies of reverse currents in n‐on‐p and p‐on‐n diodes fabricated by boron and arsenic ion implantation in vacancy‐doped p‐type and In‐doped n‐type Hg1‐xCdxTe films, respectively, are presented. The influence of p‐n junction position in double‐layer heterostructure on temperature dependencies of reverse currents is examined. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-13T06:30:15.827321-05:
      DOI: 10.1002/pssc.201510259
       
  • ZnSe:Mn aqueous colloidal quantum dots for optical and biomedical
           applications
    • Authors: Thiago G. Silva; Igor M. R. Moura, Paulo E. Cabral Filho, Maria I. A. Pereira, Clayton A. Azevedo Filho, Goreti Pereira, Giovannia A. L. Pereira, Adriana Fontes, Beate S. Santos
      Abstract: In this study, we present the optimization of the optical properties of Mn2+ doped ZnSe QDs (also referred to as d‐dots) coated with thioglycolic acid in aqueous medium. The nanoparticles were characterized by ionic coupled plasma, electron paramagnetic resonance, transmission electron microscopy and X‐ray diffractometry. By applying a controlled dose of UV irradiation, we obtained efficient orange emitting d‐dots (4T1→ 6A1 transition centered at 580 nm). The results point out to a doping fraction in the nanoparticles smaller than 1% (0.89%), and that the Mn2+ ions are preferentially located close to the particle's surface. The UV photoactivation procedure has a definite influence on the emission intensity and on the colloidal stability of the particles. Photoactivated Mn2+ d‐dots were conjugated to Concanavalin A and labeled specifically Candida albicans yeast cells, by targeting carbohydrate residues depicting the successful use of these QDs as fluorescent probes. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-13T06:30:14.725451-05:
      DOI: 10.1002/pssc.201510300
       
  • The nature of boron‐oxygen lifetimedegrading centres in silicon
    • Authors: Vladimir Voronkov; Robert Falster
      Abstract: Light‐induced degradation of minority carrier lifetime in silicon is caused by the formation of two B‐O recombination centres: fast‐stage centres (FRC) and slow‐stage centres (SRC). FRC were concluded to emerge by a carrier‐assisted reconfiguration of a latent BO2 defect composed of a substitutional boron atom and an oxygen dimer. The nature of SRC however remained uncertain; this defect appeared to involve an interstitial boron atom rather than a substitutional one. More recent data on SRC in boron‐containing compensated p‐Si and n‐Si now show that the SRC actually emerge in the same way as FRC: by a reconfiguration of BO2, but from a different latent form. The two latent BO2 defects (the precursors for FRC and for SRC) are created during a cooling stage after the last high‐temperature anneal, and their concentration, proportional to the boron concentration and squared oxygen concentration, depends on the cooling rate. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-13T06:30:13.688865-05:
      DOI: 10.1002/pssc.201600016
       
  • Comparison between Si/SiO2 mid‐gap interface states and deep levels
           associated with silicon‐oxygen superlattices in p‐type silicon
           
    • Authors: Eddy Simoen; S. Jayachandran, A. Delabie, M. Caymax, M. Heyns
      Abstract: In this paper, the deep levels found by deep‐level transient spectroscopy in Si‐O superlattices on p‐type silicon substrates are compared with the band of near mid‐gap hole traps typically observed at the Si/SiO2 interface. In addition, the impact of a post‐deposition Forming Gas Annealing is investigated. A large similarity between the two material systems is reported, which indicates that similar silicon‐oxygen bonds may be responsible for the deep hole traps.(© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-13T06:30:12.682755-05:
      DOI: 10.1002/pssc.201600018
       
  • Towards multifunctional heterostructured materials: ZnO nanowires growth
           on mesoscale periodically patterned Si
    • Authors: Anisha Gokarna; Agnieszka Gwiazda, Hind Kadiri, Anna Rumyantseva, Komla Nomenyo, Roy Aad, Gilles Lerondel
      Abstract: We report the growth of ZnO nanowires on mesoscale periodically patterned silicon. The aim of this work is to go towards fabrication of multifunctional heterostructured materials for increasing the specific surface area and light absorption properties. ZnO nanowires (NWs) were grown by chemical bath deposition technique on patterned silicon. Silicon patterning was conducted by two methods, namely, laser interference lithography and nanosphere lithography. We have studied the structural and optical properties of the ZnO NWs grown on these silicon patterns. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-03T03:40:48.47202-05:0
      DOI: 10.1002/pssc.201510295
       
  • Structural, electronic and thermodynamic properties of SrxCa1‐xS: A
           first‐principles study
    • Authors: S. Labidi; M. Boudjendlia, M. Labidi, J. Zeroual, R. Bensalem, F. El Haj Hassan
      Abstract: The principal purpose of this work is to further the understanding of the structural, electronic, and thermodynamic properties of the SrxCa1–xS alloys (0≤x ≤1) in Rock‐salt phase using the full potential augmented plane wave (FP‐LAPW) method within density functional theory. The exchange‐correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE) and the new form of GGA (WC) which is an improved form of the most popular Perdew‐Burke‐Ernzerhof (PBE), while for electronic properties, the alternative form of GGA modified by Becke‐Johnson exchange correlation potential (MBJ) was also applied. It is shown that investigation on the effect of composition on lattice constant, bulk modulus, and band gap for ternary alloys shows almost nonlinear dependence on the composition. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-03T03:40:47.247638-05:
      DOI: 10.1002/pssc.201510247
       
  • Analysis of the Hall‐effect data on Mn‐doped GaAs with taking
           into account the Hall factor for nearest‐neighbor hopping conduction
           
    • Authors: Yasutomo Kajikawa
      Abstract: The experimental data of the temperature‐dependent Hall‐effect measurements on Mn‐doped p ‐GaAs reported by Wolos et al. [Phys. Status Solidi C 6, 2769 (2009)], which exhibit the characteristic of nearest‐neighbor hoping (NNH) conduction, have been analyzed. For NNH conduction, it is assumed that the conductivity is expressed as σib (T) ∝︁ T−3/2 exp(−T0/T) while the Hall factor is expressed as Aib (T) ∝︁ T exp(−T0H/T), where T0 and T0H are adjustable parameters. It is found that kBT0 increases from 9 to 21 meV in proportion to the cube root of the substitutional Mn acceptor concentration, being consistent with the theory for NNH conduction. It is also found that KNNH = T0H/T0 decreases from 1.45 to 1.15 with increasing the substitutional Mn acceptor concentration from 0.8×1017 to 4×1017 cm‐3, being different from the concentration‐independent value of KNNH = 2/3 or 1/6 predicted by the theories. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-02T06:10:06.853976-05:
      DOI: 10.1002/pssc.201600014
       
  • Effect of electron blocking layers on the conduction and valence band
           profiles of InGaN/GaN LEDs
    • Abstract: In this paper we investigate the effect of including an electron blocking layer between the quantum well active region and the p‐type layers of a light emitting diode has on the conduction and valence band profile of a light emitting diode. Two light emitting diode structures with nominally identical quantum well active regions one containing an electron blocking layer and one without were grown for the purposes of this investigation. The conduction and valence band profiles for both structures were then calculated using a commercially available Schrödinger‐Poisson calculator, and a modification to the electric field across the QWs observed. The results of these calculations were then compared to photoluminescence and photoluminescence time decay measurements. The modification in electric field across the quantum wells of the structures resulted in slower radiative recombination in the sample containing an electron blocking layers. The sample containing an electron blocking layer was also found to exhibit a lower internal quantum efficiency, which we attribute to the observed slower radiative recombination lifetime making radiative recombination less competitive. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-05-02T06:10:04.718911-05:
      DOI: 10.1002/pssc.201510288
       
  • Back Cover: Phys. Status Solidi C 4/2016
    • Abstract: Luminescent silicon nanoparticles, apart from their potential use in optoelectronics or photovoltaics, are also very promising for biological applications, as fluorescent labels, biological sensors, drug‐delivery systems or scaffolds for various tissues. Aqueous or isotonic colloidal solutions of stable, nontoxic and strongly luminescing nanoparticles with sizes in the range of tens to hundreds of nanometers are required for biological research. In their work on pp. 142–145, K. Herynková and coauthors prepared nanoclusters of luminescent, highly porous silicon by electrochemical etching. Additional “post‐etching” in a hydrogen peroxide bath resulted in oxidized nanoparticle surfaces and hydrophilic behavior with good dispersibility in water. However, the nanoparticles revealed a clear tendency to agglomerate, the typical size of the agglomerates increased from 60 nm in fresh samples to 400 nm in one‐month‐old samples. In addition, insufficient surface electric charge to electrostatically repel the nanoparticles was confirmed by zeta‐potential measurements.The authors present the first attempt at steric stabilization by simple organic compounds, bovine serum albumin, glycine, glutamic acid and dextran. Increased stability was observed in the glycine‐terminated samples.
      PubDate: 2016-04-20T05:43:34.985474-05:
      DOI: 10.1002/pssc.201670122
       
  • Cover Picture: Phys. Status Solidi C 4/2016
    • Abstract: Combining a complex microfabrication process of miniaturized sensors or other devices with chemical modifications may be challenging and may limit possible configurations, especially when it comes to merging different receptor chemistries on one chip. A. M. Steinbach and coworkers (see pp. 135–141) took this as a challenge to develop a gas phase method that can be used to introduce a range of chemical functions to any hydroxylated surface, without the need to consider material or resist compatibilities with solvents. The developed gas phase silanization set‐up is shown in the lower right corner and represents a versatile tool for instance for lab‐on‐a‐chip systems, MEMS and other micro devices. The resulting silane layers were thoroughly characterized by several surface analytical methods. The authors additionally studied the electrical properties of silicon nanowire field effect transistors before and after the modification ensur‐ing full functionality. With 30 min needed for the reaction, the method represents a fast way to bring silanes to a surface. Therefore, it is believed that this method is useful for a wide spectrum of applications and thus opens up versatile possibilities for future lab‐on‐a‐chip systems.
      PubDate: 2016-04-20T05:43:34.937086-05:
      DOI: 10.1002/pssc.201670118
       
  • Issue Information: Phys. Status Solidi C 4/2016
    • PubDate: 2016-04-20T05:43:34.84054-05:0
      DOI: 10.1002/pssc.201670119
       
  • High‐voltage photoconductive semiconductor switches fabricated on
           semi‐insulating HVPE GaN:Fe template
    • Authors: Yunfeng Chen; Hai Lu, Dunjun Chen, Fangfang Ren, Rong Zhang, Youdou Zheng
      Abstract: In this work, high‐voltage photoconductive semiconductor switches (PCSSs) with inter‐digitated contact electrodes are directly fabricated on semi‐insultating HVPE GaN:Fe template. The PCSS exhibits a cutoff wavelength of 365 nm and a dark resistivity of ∼1010 Ω cm. A maximum blocking voltage of more than 1100 V is obtained, corresponding to a breakdown electric field higher than 1.57 MV/cm for the GaN:Fe template. When excited by a 266 nm ultraviolet pulsed laser, the PCSS under 550 V bias could produce a peak photocurrent density of 387 A/cm2 within a rise time of ∼20 ns. The fall time of the photocurrent pulse is mainly RC time limited. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:19.711137-05:
      DOI: 10.1002/pssc.201510210
       
  • Properties of two‐dimensional electron gas in AlGaN/GaN HEMT
           structures determined by cavity‐enhanced THz optical Hall effect
    • Abstract: In this work we employ terahertz (THz) ellipsometry to determine two‐dimensional electron gas (2DEG) density, mobility and effective mass in AlGaN/GaN high electron mobility transistor structures grown on 4H‐SiC substrates. The effect of the GaN interface exposure to low‐flow‐rate trimethylaluminum (TMA) on the 2DEG properties is studied. The 2DEG effective mass and sheet density are determined tobe in the range of 0.30‐0.32m0 and 4.3‐5.5×1012 cm–2, respectively. The 2DEG effective mass parameters are found to be higher than the bulk effective mass of GaN, which is discussed in view of 2DEG confinement. It is shown that exposure to TMA flow improves the 2DEG mobility from 2000 cm2/Vs to values above 2200 cm2/Vs. A record mobility of 2332±61 cm2/Vs is determined for the sample with GaN interface exposed to TMA for 30 s. This improvement in mobility is suggested to be due to AlGaN/GaN interface sharpening causing the reduction of interface roughness scattering of electrons in the 2DEG. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:18.561768-05:
      DOI: 10.1002/pssc.201510214
       
  • Admittance of MIS structures based on graded‐gap MBE HgCdTe with
           Al2O3 insulator
    • Authors: Alexander V. Voitsekhovskii; Sergey N. Nesmelov, Stanislav M. Dzyadukh, Vladimir V. Vasil`ev, Vasiliy S. Varavin, Sergey A. Dvoretsky, Nikolay N. Mikhailov, Maxim V. Yakushev, Georgiy Y. Sidorov
      Abstract: The paper presents the results of studies of the admittance of MIS structures based on heteroepitaxial MBE n (p)‐Hg0.78Cd0.22Te with insulator coating SiO2/Si3N4 and Al2O3 in the test signal frequency range 10 kHz‐1 MHz at temperatures ranging from 8 to 220 K. The main parameters of MIS structures with different insulators were determined. MIS structures with Al2O3 have a large enough insulator capacitance (compared to SiO2/Si3N4), a significant modulation capacitance on the CV characteristics, high dielectric strength and low values of the flat‐band voltage. The effective charge density found from the value of the flat‐band voltage and slow interface trap density for structures with Al2O3 comparable with the corresponding densities for structures with SiO2/Si3N4. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:17.329356-05:
      DOI: 10.1002/pssc.201510227
       
  • Electrical and optical studies of a tellurium‐related defect in
           molecular‐beam epitaxy‐grown HgCdTe
    • Abstract: Electrical and optical studies of defects in molecular beam epitaxy (MBE)‐grown HgCdTe films, undoped and doped with arsenic, were carried out. By comparing results of ion milling‐assisted Hall‐effect measurements with micro‐Raman spectroscopy data, it was shown that the films contained electrically neutral defects related to excessive tellurium. It is suggested that these defects are Te nanocomplexes and that they are typical of the MBE HgCdTe technology. Under ion milling, they get electrically activated by interstitial mercury and form donor centers with concentration of ∼1017 cm‐3, which allows for detecting them with measurements of electrical parameters of the material. Also, it can be suggested that in films doped with arsenic with high‐temperature cracking, As2 dimers in the arsenic flux react with excessive tellurium and form As2Te3 donor complexes, thus preventing formation of Te nanocomplexes. Arsenic activation annealing may break As2Te3 complexes and release Te, which can again form the complexes under ion milling. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:16.310419-05:
      DOI: 10.1002/pssc.201510234
       
  • Photosensitive MIS structures with ultrathin dielectric based on
           CdXHg1‐XTe (x ∼ 0.4)
    • Authors: Valeriy G. Kesler; Alexander A. Guzev, Sergey A. Dvoretskiy, Evgeniy R. Zakirov, Anatoliy P. Kovchavtsev, Zoya V. Panova, Maxim V. Yakushev
      Abstract: The work is aimed to studying a possibility of CdHgTe surface passivation and stabilization by tunnel‐thin (∼ 2 nm) native oxide formed by glow discharge plasma oxidation. Kinetics of MCT plasma treatment in two regimes has been obtained. Investigation of the stabilization effect during vacuum annealing and platinum deposition has been performed. It has been established that presence of a native oxide layer on MCT surface results in elimination of mercury out diffusion during the processes. MIS structures with platinum contacts and thin native oxide have been made. They have rectifying behaviour in contrast with structures without the native oxide layer. The barrier height and the detectivity have been determined from the capacitance‐voltage and current‐voltage dependences. The detectivity value of 4×1011cm.Hz1/2W‐1 (at 78 K) determined by dark current shot noise has been reached. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:15.186306-05:
      DOI: 10.1002/pssc.201510275
       
  • Growth of zinc sulfide by mist chemical vapor deposition depending on mist
           size and thermal conditions in susceptor
    • Authors: Kazuyuki Uno; Yuichiro Yamasaki, Ping Gu, Ichiro Tanaka
      Abstract: Zinc sulfide (ZnS) films were successfully grown by using mist chemical vapor deposition (mist‐CVD) with fine‐channel susceptor made of quartz. For the investigation of growth dynamics, two types of mist generators and two types of susceptors were prepared and distribu¬tion profiles of film thickness were examined. Thermal efficiency of susceptor depends on heat¬penetration efficiency and line‐velocity of the mists, which are influenced by the fine‐channel gap‐height of the susceptors. Using larger size of mists requires higher thermal efficiency in susceptor to obtain a flat thickness distribution. This result indicates that the optimization of the mist size and the susceptor structure is important for the film uniformity of grown films by the mist‐CVD. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:13.791215-05:
      DOI: 10.1002/pssc.201510309
       
  • Fabrication and characterization of two‐dimensional cubic AlN
           photonic crystal membranes containing zincblende GaN quantum dots
    • Abstract: We successfully developed a process to fabricate freestanding cubic aluminium nitride (c‐AlN) membranes containing cubic gallium nitride (c‐GaN) quantum dots (QDs). The samples were grown by plasma assisted molecular beam epitaxy (MBE). To realize the photonic crystal (PhC) membrane we have chosen a triangular array of holes. The array was fabricated by electron beam lithography and several steps of reactive ion etching (RIE) with the help of a hard mask and an undercut of the active layer. The r/a‐ ratio of 0.35 was deter‐ mined by numerical simulations to obtain a preferably wide photonic band gap. Micro‐photoluminescence (µ‐PL) measurements of the photonic crystals, in particular of a H1 and a L3 cavity, and the emission of the QD ensemble were performed to characterize the samples. The PhCs show high quality factors of 4400 for the H1 cavity and about 5000/3000 for two different modes of the L3 cavity, respectively. The energy of the fundamental modes is in good agreement to the numerical simulations. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T04:12:12.88812-05:0
      DOI: 10.1002/pssc.201600010
       
  • Fabrication of GaN quantum dots using Ga droplet epitaxy and thermal
           annealing by metal organic chemical vapor deposition
    • Authors: Zhiqiang Qi; Yanyan Fang, Changqing Chen, Jiangnan Dai
      Abstract: Optically active GaN quantum dots are grown by droplet heteroepitaxy and post‐growth annealing. The evolution of morphology and optical properties of thermal annealing GaN QDs have been investigated. The results show that thermal annealing under NH3/N2 ambience is a necessary condition for maintaining the optimal QDs morphology and improving optical properties of GaN QDs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-14T03:42:16.08676-05:0
      DOI: 10.1002/pssc.201510154
       
  • Fabrication and characterization of Au/Zn composite electrode on
           p‐CdZnTe (111) B plane
    • Abstract: Electrode fabrication is a key procedure for preparation of high‐performance CdZnTe detectors, and the metal–semiconductor contact contributes greatly to the performance of detectors. In the present paper, a vacuum evaporation method was used to deposit a Au/Zn composite electrode on the (111) plane of p‐CdZnTe. Based on the AFM, SEM, current–voltage testing and the barrier‐height calculations, the effects of an Au/Zn contact on CdZnTe detector properties were investigated. The results showed that a lower Schottky barrier height was attained by depositing a Au layer on p‐CdZnTe(111) A plane and a Au/Zn double layers on (111) B plane, decreasing the influence of the Te‐enriched surface on the metal–semiconductor contact, and suggesting a better ohmic contact for CdZnTe detectors. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:34:04.771146-05:
      DOI: 10.1002/pssc.201510279
       
  • Exciton recombination in spontaneously formed and artificial quantum wells
           AlxGa1‐xN/AlyGa1‐yN (x
    • Authors: A. A. Toropov; E. A. Shevchenko, T. V. Shubina, V. N. Jmerik, D. V. Nechaev, G. Pozina, P. Bergman, B. Monemar, S. Rouvimov, S. V. Ivanov
      Abstract: We report on photoluminescence (PL) spectroscopy and electron microscopy studies of an AlGaN quantum well (QW) structure grown by molecular beam epitaxy under metal‐rich conditions with substrate rotation. Both techniques reveal unintentional formation within the AlGaN barriers of a quasiperiodic structure of thin Ga‐rich layers, whose period is controlled by both the substrate rotation rate and the AlGaN growth rate. These compositional modulations act as 1‐3 monolayer thick QWs emitting below 250 nm with an internal quantum efficiency (IQE) as high as ∼30% at room temperature under weak excitation. Variational calculations of the QW exciton properties indicate that the observed high IQE can result from strong three‐dimensional localization of the excitons confined in the narrow QWs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:34:03.912289-05:
      DOI: 10.1002/pssc.201600009
       
  • Self‐assembly of tomato bushy stunt viruses on silicon under the
           influence of the drop shape, drop volume and the virus concentration
    • Abstract: Self‐assembled plant viruses, here tomato bushy stunt virus (TBSV), are interesting building blocks in nanobiotechnology. Especially genetically modified virus types show enhanced self‐assembling properties compared to the wild type (wt) virus. In this article important aspects of the self‐assembly of tetra histidine (4xHis) TBSV (histidine side chains on the capsid surface) are presented in detail. Different virus concentrations show a different wetting behavior of the solid substrate. This leads to different coverages depending on the position within the sample. In the center of the virus covered area, the most stable conditions are found and often also the highest coverage. If these central areas are compared to samples prepared with different virus concentrations, a large variation of the coverage can be detected. For the desired homogeneous monolayer of the virus, the concentration has thus to be optimized. In addition, it could be shown that the drop volume does not influence the homogeneity of the surface coverage. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:34:02.867901-05:
      DOI: 10.1002/pssc.201600011
       
  • Effect of superlattice on light output power of InGaN‐based
           light‐emitting diodes fabricated on underlying GaN substrates with
           different dislocation densities
    • Authors: Kohei Sugimoto; Yusho Denpo, Narihito Okada, Kazuyuki Tadatomo
      Abstract: We evaluated the electrical properties of InGaN‐based light‐emitting diodes (LEDs) with a surperlattice (SL) layer just below the MQWs for forming V‐shaped pits (V‐pits) on underlying GaN substrates with different dislocation densities (DDs). The SL was effective for improving the EL intensity for all the LEDs with different DDs. However, the improvement ratio decreased with decreasing DD. The SL is effective for performance improvement of the LEDs with high DDs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:31.796145-05:
      DOI: 10.1002/pssc.201510203
       
  • Analysis of breakdown characteristics in source field‐plate
           AlGaN/GaN HEMTs
    • Authors: Hiraku Onodera; Hideyuki Hanawa, Kazushige Horio
      Abstract: Two‐dimensional analysis of off‐state breakdown characteristics of source field‐plate AlGaN/GaN HEMTs is performed by considering a deep donor and a deep acceptor in a buffer layer. It is shown that the introduction of field plate is effective in improving the breakdown voltage, but it can decrease with the field‐plate length, and hence its optimum length should exist. It is also shown that the breakdown voltage of the source field‐plate structure is a little lower than that of the gate field‐plate structure when the field‐plate length is short, because the electric field at the drain edge of the gate becomes higher. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:30.239737-05:
      DOI: 10.1002/pssc.201510155
       
  • Power density dependent photoluminescence spectroscopy and Raman mapping
           of semi‐polar and polar InGaN/GaN multiple quantum well samples
    • Abstract: We present a study of polar and semi‐polar InGaN/GaN multiple quantum well (MQW) samples. Power density dependent photoluminescence (PL) was conducted on the samples. The polar sample exhibited a large blue shift of 65 nm in the peak PL from low to high power density compared to 10 nm for the semi polar sample. The semi‐polar sample displayed “chevron” shaped surface features. These chevrons were mapped using micro‐PL spectroscopy and showed a red shift of 10 nm at the “join” of the chevron. Raman mapping of the chevron also showed an increase in amplitude of the Raman shift in this area. Angle dependent polarised Raman measurements were conducted on the semi‐polar sample to potentially isolate the scattering from the InGaN layers. However, polarised mapping exhibited similar behaviour to the unpolarised maps at the chevron join, indicating that the GaN bulk layer is responsible for the observed scattering. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:27.423218-05:
      DOI: 10.1002/pssc.201510196
       
  • Comparative performance assessment of SiC and GaN power rectifier
           technologies
    • Authors: Sauvik Chowdhury; T. Paul Chow
      Abstract: Silicon carbide and gallium nitride based Schottky and pin junction power rectifiers offer different performance trade‐offs in terms of metrics such as forward voltage drop, switching energy loss and surge current capability. The goal of this paper is to identify the application space for different rectifier technologies. An analytical comparison between the performance of different power rectifier diodes for breakdown voltages ranging from 600V to over 8 kV is presented. It is shown that although GaN SBD offers some advantage over SiC diodes due to lower losses, low surge current capability of GaN may hinder its widespread adoption in applications. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:25.856495-05:
      DOI: 10.1002/pssc.201510204
       
  • High accuracy equivalent circuit model for GaN GIT bi‐directional
           switch
    • Abstract: The simple and high‐accuracy equivalent circuit model for GaN‐GIT bi‐directional switch have been constructed by eliminating the gate resistance dependence from the capacitance parameters and employing the parallel gate resistance circuit with the diode. By the new methods, the calculated waveforms, switching losses and switching times agree well with the experimental ones, and the accuracy between the calculations and the experiments are more than 90%. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:21.482969-05:
      DOI: 10.1002/pssc.201510205
       
  • 3.2 mΩcm2 enhancement‐mode GaN MOSFETs with breakdown voltage
           of 800 V
    • Authors: Hisashi Saito; Miki Yumoto, Shigeto Fukatsu, Yosuke Kajiwara, Aya Shindome, Kohei Oasa, Yoshiharu Takada, Kunio Tsuda, Masahiko Kuraguchi
      Abstract: Enhancement‐mode GaN metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) have been reported. We utilized the atomic layer deposition (ALD) method for the fabrication process of the gate dielectric, in order to suppress plasma damage and obtain high‐quality dielectric film. In the fabricated devices, the specific on‐state resistance of 3.2 mΩcm2 and the breakdown voltage of 800 V were achieved. Moreover, a 10‐year lifetime with a cumulative failure rate of 0.1% was guaranteed at over 20 V. This voltage was twice the operation voltage of 10 V. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-29T03:24:14.423488-05:
      DOI: 10.1002/pssc.201510225
       
  • Electronic spectrum of Bi‐related defects in crystalline CdTe
    • Authors: Vladimir Krivobok; Sergey Nikolaev, Evgeny Onischenko, Anna Pruchkina, Sergey Kolosov, Yuri Klevkov, Victor Bagaev
      Abstract: Using measurements of conductivity and low‐temperature photoluminescence, we have studied electronic levels in the band gap of CdTe:Bi and CdTe:Bi,Cl single crystals grown by the modified Bridgman technique. Three type of deep levels (EV+0.29 eV, EV+0.4 eV, EV+0.72 eV) and Bi‐related shallow acceptor have been observed depending on the doping conditions. Energy spectrum of a shallow Bi‐related acceptor has been measured and its low symmetry has been established. The tentative interpretation for all the levels observed has been proposed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:15.499157-05:
      DOI: 10.1002/pssc.201510274
       
  • Growth and characterization of Mg1‐xCdxO thin films
    • Abstract: In this paper, we study the growth of thin films of the Mg1–xCdxO alloy in the Mg‐rich range of compositions by using the metal organic chemical vapour deposition (MOCVD) method at low pressure. X‐ray diffraction (XRD) has been used to analyse the compound formation and the progressive incorporation of Cd2+ ions into the cubic MgO lattice. Both, layers with a single‐cubic phase of Mg1–xCdxO and layers with a phase separation, where Cd1–xMgxO and Mg1–xCdxO coexist, have been studied. Finally, a morphological study of the layers has been carried out by using scanning electron microscopy (SEM) and the layers' composition has been measured by energy dispersive X‐ray analysis (EDX). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:14.563297-05:
      DOI: 10.1002/pssc.201510276
       
  • Structural, optical and magnetic characteristics of II‐VI
           semiconductor nanocrystal‐graphene hybrid nanostructures
    • Authors: Andriy I. Savchuk; Ihor D. Stolyarchuk, Serhii A. Savchuk, Eugeniusz M. Sheregij, Jacek Polit
      Abstract: CdS, CdTe, ZnO, and ZnO:Co nanocrystals and related hybrid nanostructures, in which the nanoparticles combined with graphene, have been studied. Different chemical approaches for synthesis of II‐VI semiconductor nanocrystal‐graphene hybrids have been applied depending on chemical composition. Transmission electron microscopy characterizations proved the formation of graphene based hybrid nanostructures. Absorption spectra near band‐gap edge have shown changes due to the interaction of the nanocrystals with graphene. The revealed photoluminescence quenching effect in II‐VI semiconductor nanocrystal‐graphene hybrids can be served as evidence for electron transfer from the nanoparticles to graphene. Results of Faraday rotation measurements in doped ZnO:Co nanocrystals and their hybrids at room temperature demonstrated paramagnetic behaviour for both kinds of samples. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:13.065783-05:
      DOI: 10.1002/pssc.201510283
       
  • Structural properties and vertical transport in ZnSe/CdSe superlattices
           grown on an In0.3Ga0.7As metamorphic buffer layer
    • Authors: E. A. Evropeytsev; S. V. Sorokin, G. V. Klimko, S. V. Gronin, I. V. Sedova, K. G. Belyaev, S. V. Ivanov, G. Pozina, A. A. Toropov
      Abstract: We report on the growth by molecular‐beam epitaxy of short‐period ZnSe/CdSe superlattices (SLs) on an In0.3Ga0.7As metamorphic buffer layer. Such SLs are considered as a promising material for a wide band‐gap photoactive p‐n junction in a hybrid monolithic Ge/InxGa1‐xAs/Iny(Al,Ga)1‐yAs/II‐VI solar cell. Lattice‐matching of the SLs to the In0.3Ga0.7As layer is confirmed by X‐ray diffractometry. Vertical transport of photoexcited carriers is investigated by means of both steady state and time‐resolved photoluminescence techniques in heterostructures containing the ZnSe/CdSe SL with an enlarged quantum well (EQW). Characteristic times of the carrier transport across the SL towards EQW are evaluated in the temperature range 120–300 K. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:11.814723-05:
      DOI: 10.1002/pssc.201510305
       
  • Influence of source transport rate upon fractions of Mg and Se in
           Zn1‐xMgxSeyTe1–y layers grown by metalorganic vapor phase
           epitaxy
    • Authors: Katsuhiko Saito; Masakatsu Abiru, Eiichiro Mori, Yasuhiro Araki, Daichi Tanaka, Tooru Tanaka, Qixin Guo, Mitsuhiro Nishio
      Abstract: The growth of undoped Zn1–xMgx Sey Te1–y layers on (100) ZnTe substrates by metalorganic vapor phase epitaxy has been carried out. The fractions of Mg and Se, Raman property and surface roughness have been characterized as a function of bis‐methylcyclopentadienyl‐magnesium ((MeCp)2Mg) or diethylselenide (DESe) transport rates. It has been demonstrated that the Mg and Se fractions in Zn1–xMgx Sey Te1–y layer can be controlled successfully by these source transport rates. Furthermore, the behaviors of two Raman peaks related to ZnSeTe‐like longitudinal optical phonon mode and MgSeTe‐like one have been clarified for some Mg and Se fractions in Zn1–xMgx Sey Te1–y layers. It has been shown by varying (MeCp)2Mg or DESe transport rates that Zn1‐xMgx Sey Te1–y layer nearly‐lattice‐matched to ZnTe substrate shows low surface roughness. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:10.744695-05:
      DOI: 10.1002/pssc.201510304
       
  • A comparative study of the gas sensing properties of hierarchical ZnO
           nanostructures
    • Abstract: Two types of ZnO nanostructure have been fabricated to make a comparative study on their gas sensing performance: the conventional ZnO nanowire arrays were synthesized by hydrothermal method and the hierarchical ZnO nanowires/nanofibers nanostructures were prepared through a combination of the hydrothermal and electrospinning methods. Field emission scanning electron microscopy study showed a quiet homogeneous morphology both for both nanostructures. Three kinds of commonly used gases, such as ethanol, acetone and ammonia were chosen for ZnO nanostructure gas sensing property study. The UV‐Visible spectroscopy measurements showed a higher detection sensitivity of ZnO NWs for ammonia compared to ethanol and acetone, and an enhanced sensing performance for the hierarchical nano‐ structure, which has a higher surface to volume ratio. On the other hand, the enhancement was more obviously in the case of ethanol sensing. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:09.844942-05:
      DOI: 10.1002/pssc.201510301
       
  • 2D‐localization and delocalization effects in quantum Hall regime in
           HgTe wide quantum wells
    • Authors: Svetlana V. Gudina; Yurii G. Arapov, Vladimir N. Neverov, Sergey M. Podgornykh, Mikhail R. Popov, Nina G. Shelushinina, Mikhail V. Yakunin, Sergey A. Dvoretsky, Nikolay N. Mikhailov
      Abstract: We have measured the longitudinal and Hall resistivities in the quantum Hall regime at magnetic fields B up to 9 T and temperatures T = (2.9–50) K for HgTe/HgCdTe heterostructure with wide HgTe quantum well. The results are analysed within the scaling concept for the conductivity on the delocalized states at the center of the Landau level and within the variable‐range hopping model for the conductivity on the localized states between the Landau levels. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:08.88983-05:0
      DOI: 10.1002/pssc.201510299
       
  • Tamm plasmon polaritons in the visible spectral region and its optical
           properties in ZnSe‐based microcavities
    • Abstract: We report on the formation of Tamm plasmon (TP) modes in the visible spectral region at the interface between a Ag film and a ZnSe‐based distributed Bragg reflector (DBR). The tuning of the TP eigenenergies within the stop‐band in dependence on the DBR top layer thickness is investigated by micro‐reflectivity measurements. The experimental findings are compared with calculations using the transfer matrix method. The latter calculations show that strong coupling can be achieved between quantum well (QW) excitons and the TP modes. In addition, the Rabi‐splitting energy can be enhanced in a simple TP structure by increasing the number of QWs inside the top layer of the DBR. When a metal layer is deposited on a cold MC sample, micro‐reflectivity spectra show a blue shift of the cavity resonance. The TP modes are likewise observed in the same MC sample when reducing the top layer thickness of the DBR. This shift of cavity resonance and formation of TP mode are in good agreement with calculations. These results are rather promising in order to realize a spatial confinement of the polaritons by utilizing metal strips. Such channeling of polaritons opens the way to practical demonstration of exciton‐polariton integrated circuits. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:08.001662-05:
      DOI: 10.1002/pssc.201510296
       
  • Effect of Al doping in the Ag layer of MgZnO/Ag/MgZnO
           
    • Authors: Yukiko Sugimoto; Kanae Igarashi, Shinya Shirasaki, Akihiko Kikuchi
      Abstract: Transparent conductive films (TCFs) with dielectric/metal/dielectric (DMD) structure covering the UVA (λ = 315–380 nm) and visible wavelength region (380–780 nm) were fabricated using Al‐doped Mg0.4Zn0.6O (AMZO) dielectric and 1.7 at% Al‐doped Ag (Ag(Al)) metal layers. The AMZO/Ag(Al)/AMZO‐DMD film with a 7 nm thick Ag(Al) layer after annealing in vacuum at 400 °C showed superior performance as a TCF, i.e., average transmittance from UVA to visible region (315–780 nm) of 88.2% and sheet resistance of 7.6 Ω/sq. The effect of Al doping on optical transmission, sheet resistance, surface morphology, and thermal durability of the AMZO/Ag(Al)/AMZO‐DMD films were also investigated. The 1.7 at% Al doping suppressed the initial island growth of the thin Ag layer and the plasmon resonance absorption dipped in the optical transmission spectra. Al doping in the Ag layer also improved the thermal durability of AMZO/Ag/AMZO‐DMD films. The threshold temperature for Ag void formation caused by metal segregation increased from 300 °C (DMD with a pure Ag layer) to 400 °C (DMD with an Al‐doped Ag layer). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:07.072077-05:
      DOI: 10.1002/pssc.201510290
       
  • Influence of the number of electronically coupled CdSe/ZnSe QD planes on
           characteristics of optically pumped green lasers
    • Authors: I. V. Sedova; E. V. Lutsenko, S. V. Sorokin, A. G. Vainilovich, S. V. Gronin, G. P. Yablonskii, M. Aljoheni, A. Aljerwi, A. Alyamani, S. V. Ivanov
      Abstract: Structural properties and laser characteristics of true green (λ=530‐550 nm) ZnSe‐based optically pumped laser heterostructures with several (up to three) CdSe/ZnSe quantum dot (QD) planes in the active region were studied in details. Optimization of the MBE growth conditions to reduce the non‐equilibrium defect density in the active region as well as the active region design allowed obtaining nearly the same rather low laser threshold values of Ithr∼4 kW/cm2 at Lcav∼100 μm for all the samples. The internal laser parameters were determined by measuring the laser threshold and differential quantum efficiency as functions of the cavity length. The design of laser structures provides high excitation homogeneity of the active region due to strong enough carrier tunneling between QD layers spaced by 5‐nm‐thick ZnSe barriers, which is confirmed by the sub‐linear dependence of the transparency excitation intensity versus number of QD planes in the active region (IT = 0.556, 1.037, and 1.311 kW/cm2). The triple‐QD‐plane laser structure demonstrates significant increase in characteristic gain up to ΓG0=161.62 cm‐1. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:20:05.605287-05:
      DOI: 10.1002/pssc.201510289
       
  • Numerical modeling and simulation of ZnO nanowire devices for energy
           harvesting
    • Abstract: Duo to their multifunctional properties, the piezoelectric ZnO nanowires are of great interest in many applications such as the energy harvesting. In this work, a numerical modelling based on the finite element method was performed to study the potential distribution inside the ZnO nanowire and the impact of the geometric parameters on the generated piezopotential both in bending and compression deformation. In this context, a nanowire discharge behavioural study was carried out in order to obtain an analytic expression which connects the piezopotential and nanowire geometrical parameters in the bending deformation. Furthermore, a heuristic algorithm Particle Swarm Optimization (PSO) has been used in order to improve the electromechanical performance of ZnO nanowire based nanogenerator. It is fount that under the same order of force applied on a nanowire, the compression mode results in a piezopotential 9 times larger than that in the bending deformation. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:17.801655-05:
      DOI: 10.1002/pssc.201510270
       
  • Electron–phonon interaction in II‐VI quantum wells
    • Authors: A. Yu. Maslov; O. V. Proshina
      Abstract: The theory of charge‐particle interaction with polar optical phonons is developed for II‐VI compounds‐based heterostructures in which the symmetries of the quantum well and barrier materials are different. The parameters of the electron–phonon interaction are found for the structures in which the material of hexagonal symmetry is used for creating a quantum well or barriers. It is shown that the electron–phonon interaction depends on the anisotropy of the dielectric parameters of the hexagonal material for both cases. Compared to previously obtained results for a quantum well based on the material of cubic symmetry both enhancing and weakening of polaron effects are possible. The obtained results are applied to the explanation of polaron mass magnitude in the quantum well based on ZnO‐ZnMgO. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:16.973941-05:
      DOI: 10.1002/pssc.201510263
       
  • Investigation of yellow/green II‐VI compound semiconductor laser
           diode structures on InP substrates
    • Authors: Ryohei Kobayashi; Shingo Takamatsu, Koji Fukushima, Katsumi Kishino, Ichirou Nomura
      Abstract: II‐VI‐compound‐semiconductor laser diode (LD) structures on InP substrates were investigated using device simulations and waveguide analysis. Our simulations showed that electron injection from the n‐cladding into the active layer is hindered by the n‐side barrier layer between the n‐cladding and active layer. Consequently, holes are not injected into the active layer but instead leak to the n‐side layers. It was shown that carrier injection efficiency can be improved by removing the n‐barrier. On the contrary, no large differences were observed between the optical confinement factors of the LD structures with and without the n‐barrier layer. In experiments, we have fabricated the LD structures with and without the n‐barrier layer on InP substrates using molecular beam epitaxy. The turn‐on voltage of the device without the n‐barrier was smaller than that for the device with the n‐barrier by about 5 V. Spontaneous orange emissions around 603 nm were observed for the devices without the n‐barrier. In contrast, no emission was observed for the devices with the n‐barrier. These results prove that the carrier injection into the active layer is enhanced by the removal of the n‐barrier, leading to improved the device performances. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:16.108611-05:
      DOI: 10.1002/pssc.201510255
       
  • Effects of strontium concentration on structural, electronic, optical and
           thermodynamic properties of Pb1‐xSrxS
    • Authors: Jazia Zeroual; Salima Labidi, Malika Labidi, Rachid Bensalem
      Abstract: Theoretical investigations of structural, electronic, optical and thermodynamic properties of Pb1‐xSrxS with rocksalt crystal structure are reported, theoretical calculations are mainly based on the full potential linearized augmented plane wave (FP‐LAPW) method within the density functional theory (DFT) the generalized gradient approximation (GGA) of Perdew et al. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, and mixing entropies on the composition x were analyzed mainly for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for Pb1‐xSrxS exhibits a marginal deviation from the Vegard’s law. A significant deviation of the bulk modulus from linear concentration dependence was observed for the alloy. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. Besides, a regular‐solution model is used to investigate the thermodynamic stability of the alloys, which mainly indicates a phase miscibility gap. In fact and since there is a good agreement between our main results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:14.867908-05:
      DOI: 10.1002/pssc.201510237
       
  • Theoretical investigation of the stability of defect complexes in silicon
    • Authors: Karine Abgaryan; Ilya Mutigullin
      Abstract: In this work theoretical investigation of the stability of various defect complexes including vacancies, self‐interstitials and their clusters was performed by means of ab initio as well as molecular dynamic calculations. Meta‐stable defect configurations similar to those observed earlier experimentally were found. Also the software for the molecular dynamic calculations and for the visualization of calculation results was developed. The results of the first‐principles calculations were used for the parametrical fitting of Tersoff potential of silicon. Obtained potential was used to perform molecular dynamic calculations of the various configurations of defects in silicon. This approach allowed us to study the dynamics of the atomic system over time and temperature range. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:13.833628-05:
      DOI: 10.1002/pssc.201510220
       
  • Numerical investigation of nanoscale double‐gate junctionless MOSFET
           with drain and source extensions including interfacial defects
    • Abstract: The use of uniformly doped channel, source and drain regions presents the well‐known problem of the high series resistance associated to the extensions, which degrades the electrical performance of the nanoscale multi‐gate junctionless MOSFETs. Therefore, new designs and accurate investigation of nanoscale double gate junctionless (DGJ) MOSFET including the defects at the interface Si/SiO2 are required for the comprehension of the fundamentals of such device behavior against the ageing phenomenon. Based on 2D numerical investigation of a nanoscale DGJ MOSFET, in the present work a numerical study for I‐V and small signal characteristics, by including both the highly doped extension regions and the interfacial defects, is presented. The investigated design, which is a technologically feasible technique by introducing only one ion implantation step, provides a good solution to improve the device immunity against the interfacial defects under critical conditions, where the channel length is taken equals to 10 nm. In this context, I‐V, analog and linearity characteristics are investigated by an appropriate 2‐D numerical modeling, where the obtained results are compared with those of the conventional DGJ MOSFETs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:12.953254-05:
      DOI: 10.1002/pssc.201510167
       
  • Optimisation and design of PV modules for the application on bus
           roof‐top and system integration for solar cooling
    • Abstract: In this study, an external electrical cooling unit powered by PV modules was installed on the roof‐top of a bus to keep cooled interior atmosphere at a certain temperature level during the journey breaks. All solar cells used in this project were fabricated by Center for Solar Energy Research and Applications (GUNAM) and; then, integrated onto a bus roof together with MAN Turkey A.Ş. For integration of PV modules onto roof of bus, a reliable and commercially applicable method has been developed. Following integration, illumination level on the bus in summer season was measured to investigate the shadow effect on the bus roof while touring in the city. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:11.687839-05:
      DOI: 10.1002/pssc.201510145
       
  • The efficiency droop impact of GaN‐based LEDs on the performance of
           OFDM visible light communication system
    • Authors: Huimin Lu; Tongjun Yu, Chuanyu Jia, Yini Zhang, Jianping Wang, Guoyi Zhang
      Abstract: The physical mechanism in efficiency droop of GaN‐based LEDs fabricated by metal organic chemical vapor deposition (MOCVD) was investigated by experiment and calculation. On this basis, the efficiency droop impact on the performance of orthogonal frequency division multiplexing (OFDM) visible‐light communication (VLC) system was analyzed. The numerical results show that the VLC system performance decreases obviously under the impact of the LED efficiency droop. And, the performance deterioration of OFDM VLC system aggravates as FFT sampling rate increase due to signal dynamic range enlargement. Furthermore, the efficiency droop impact on the VLC performance can be alleviated by adjusting the LED operating condition. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-16T06:10:10.818985-05:
      DOI: 10.1002/pssc.201600002
       
  • Comparative studies of CdSe/ZnSe quantum dot structures epitaxially grown
           with or without a sub‐monolayer CdTe stressor
    • Authors: M. V. Rakhlin; K. G. Belyaev, I. V. Sedova, S. V. Sorokin, S. V. Gronin, A. A. Usikova, A. A. Sitnikova, P. N. Brunkov, S. V. Ivanov, A. A. Toropov
      Abstract: We report on comparative studies of the emission properties of CdSe/ZnSe quantum dots (QDs) grown by molecular beam epitaxy either with or without predeposition of a sub‐monolayer CdTe stressor, and in the latter case, either with or without in‐situ thermal annealing. The emission of a limited number of QDs was registered in all samples by micro‐photoluminescence confocal spectroscopy through 500‐nm‐size round apertures opened in a non‐transparent gold mask by ball assisted etching technique. The measurements reveal the lowest density of emitting QDs in the sample grown with the in‐situ annealing that is attributed to both ripening of the CdSe QDs and strain relaxation in the largest QDs, followed by formation of defects serving as centres of nonradiative recombination. The employment of the CdTe stressor causes narrowing of the total QDs emission band and simultaneous broadening of the single‐QD lines that is consistent with the formation of a relatively homogeneous dense array of type‐I CdSe/ZnSe QDs adjoining type‐II Zn(Cd)Te/ZnSe nanostructures. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:19.330217-05:
      DOI: 10.1002/pssc.201510302
       
  • Growth, structural and optical properties of ZnO/ZnMgO core‐shell
           heterostructures
    • Authors: S. A. Said Hassani; C. Sartel, C. Vilar, G. Amiri, A. Lusson, V. Sallet, P. Galtier
      Abstract: ZnO nanowires have been grown by metalorganic chemical vapor deposition on sapphire substrates. The use of N2O and DEZn as oxygen and zinc precursors combined with high temperature leads to the spontaneous growth of vertical ZnO nanowires (NWs) on underlying three dimensional islands present at the bottom of each nanowire. These nanowires are grown along the c axis of the wurtzite structure, exhibit well defined m‐plane facets and are free of extended defects. This configuration is favorable to band‐gap engineering studies. Based on this, we have grown a series of radial ZnO/ZnMgO shells and quantum wells with different thicknesses and Mg concentrations. ZnxMg1‐xO alloys have been grown using O2, (MCp)2Mg and DEZn as oxygen, magnesium and zinc precursors. Low temperature photoluminescence spectroscopy and transmission electron microscopy have assessed Mg concentrations in the shell up to 20 %. Electron diffraction reveals that the ZnMgO alloyed structure is, at least partially, ordered. Micro‐photoluminescence performed on a single ZnO/ZnMgO coreshell nanowire including a quantum well exhibits luminescence properties, with a lateral quantum confined emission. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:16.824029-05:
      DOI: 10.1002/pssc.201600001
       
  • Electric field inhomogeneity in ohmic‐type CdTe detectors measured
           by time‐of‐flight technique
    • Authors: Kazuhiko Suzuki; Takayuki Sawada, Satoru Seto
      Abstract: The bias‐induced instability of the internal electric field in Ohmic‐type CdTe gamma‐ray detectors is investigated by using the time‐of‐flight technique. Based on the solution of one dimensional Poisson equation, transient current waveforms at different delays of laser excitation from the bias application and at different temperatures are analysed It is shown that under DC bias application, the internal electric field decreases with depth because of the positive space charge buildup in the detectors. Further, the origin of the space charge is attributed to the injection and successive trapping of holes from the anode side at the early stage of evolution and then later to the thermal release of electrons from a deep donor at 0.64 eV. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:14.993931-05:
      DOI: 10.1002/pssc.201510239
       
  • Manifestation of strong d‐p hybridization in photoluminescence
           spectra of ZnO:Ni and ZnO:Co
    • Authors: V. I. Sokolov; N. B. Gruzdev, V. A. Pustovarov, V. N. Churmanov
      Abstract: For the first time photoluminescence and photoluminescence excitation spectra for ZnO:Co and ZnO:Ni crystals were obtained at the excitation by the synchrotron radiation in the interval of energy of (3.7‐21) eV, T = 8 K. It is shown that these spectra are formed by intense radiative transitions through 3d charge transfer states in the band gap. This fact evidences about much stronger hybridization between d‐states of impurity and p‐states of anions in comparison with other II‐VI:3d compounds. It is very important for applications in optoelectronics, for visualization of ultraviolet radiation and understanding of photocatalytic activity of ZnO:3d nanocrystals in the visible region of the spectrum. From the comparison of PLE spectra for ZnO:Co and ZnO:Ni with the spectrum of calculated DOS for ZnO it is revealed a visible transformation of part of valence band states due to a strong d‐p hybridization. Obtained results allow us to consider ZnO:3d as a compounds with a strong correlations. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:08.729506-05:
      DOI: 10.1002/pssc.201510241
       
  • Dislocations in MCT heteroepitaxial structures on (013) substrates and
           possibilities of dislocation density reducing
    • Authors: Yury Sidorov; Ivan Loshkarev, Irina Sabinina, Evgeny Trukhanov, Vasily Varavin, Maksim Yakushev, Aleksei Kolesnikov
      Abstract: Dislocations in heterostructures CdTe/ZnTe/GaAs(013) and CdTe/ZnTe/Si(013) were investigated using selective etching and transmission electron microscopy. The calculations of critical film thickness hc were fulfilled for 12 various slip systems, the experimental results were obtained for 4 of them. Misfit dislocations are introduced in a ZnTe film at the stage of formation of the first monolayers. With their introduction, the crystal lattices of the substrate and the film unfold relative each other that is confirmed by X‐ray diffraction measurements. An increase in the dislocation density into the CdTe and HgCdTe films was observed using layer‐by‐layer etching. That is testifies to the annihilation of threading dislocations during the growth of CdTe and MCT films. The dislocation annihilation rate is higher in films grown on GaAs(013) than on Si(013). Perhaps this is due to the higher proportion of gliding dislocations in CdTe films on GaAs substrates (013). It was made annealing of MCT films under cyclic temperature change in such way that activity of MCT components was changed to enhance the non‐conservative motion of dislocations. As a result, the density of penetrating dislocations in the active areas in MCT films on silicon substrates was decreased to the value of 2.5×106 cm‐2. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:05.639755-05:
      DOI: 10.1002/pssc.201510243
       
  • Development of ZnSe‐based organic–inorganic hybrid
           UV‐APDs array
    • Authors: Tomoki Abe; Ryoichi Inoue, Takeru Fujimoto, Kenta Tanaka, Shigeto Uchida, Hirofumi Kasada, Koshi Ando, Kunio Ichino
      Abstract: Recently, we have developed organic (PEDOT:PSS)–inorganic (ZnSSe) hybrid avalanche photodiode (APD) with long life time and its array. In this article, we review the development of the organic–inorganic hybrid‐type ZnSe‐based UV‐APDs array. We used PEDOT:PSS as UV transparent hole‐transport conducting polymer window layers formed by inkjet printing technique. We have successfully fabricated low dark current ultraviolet hybrid APDs. The hybrid APD device has exhibited very low voltage APD operation at 29 V and extremely low dark current of 10‐11 A/mm2 in the avalanche breakdownregion. The hybrid APD also has shown maximum multiplication factor of 45 and high sensitivity ∼ 3 A/W at the ultraviolet region (∼ 300 nm). A stable device operation is established using polyimide passivation and sealed package with N2 atmosphere. We also demonstrated integrated devices operation in APD mode with very small photosignal cross‐talk of ‐50 dB. The tail of current‐profile was determined as 8 μm by using in‐plane electron‐beam induced current (EBIC) measurement. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:15:02.679457-05:
      DOI: 10.1002/pssc.201510273
       
  • The local electron interaction with crystal defects in wurtzite CdS
    • Authors: Orest Malyk; Volodymyr Rodych, Hryhoriy Il'Chuk
      Abstract: In the present paper the interaction of electrons with different types of defects with the potential of the limited action radius – polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain centers, ionized and neutral impurities – in cadmium sulfide is considered. The dopant concentration in observed CdS crystals was in the limits of 5.5×1015 ÷ 1.1×1019 cm‐3. The dependences of the electron mobility and Hall factor on temperature in the interval 10 ÷ 400 K are investigated. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:14:59.069149-05:
      DOI: 10.1002/pssc.201510281
       
  • Peculiarities of CdS nanocrystal formation at annealing of a
           Langmuir‐ Blodgett matrix
    • Authors: Kirill Svit; Dmitry Protasov, Sergey Teys, Larisa Sveshnikova, Yakushev Maksim, Konstantin Zhuravlev
      Abstract: Formation and assembling of CdS nanocrystals (NC) on highly‐ordered pyrolytic graphite (HOPG) and on oxidized silicon substrates have been investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). NC were initially formed within a Langmuir‐Blodgett (LB) matrix of cadmium behenate. The LB matrix was then removed by annealing in an ammonia atmosphere. It is shown that the NC self‐assembling is mainly determined by the LB matrix wetting properties. In case of wettable HOPG substrate homogeneous matrix evaporation occurs that leads to coarsening of the NC arrays as the main self‐assembly process. Otherwise, NC prepared on non‐wettable SiO2‐Si substrate demonstrate arrays formation determined by the LB matrix dewetting process. For the both cases, the influence of kinetic limitations connected with matrix evaporation rate on the self‐assembly process is observed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-03-03T09:14:57.51281-05:0
      DOI: 10.1002/pssc.201510285
       
  • Observation of topological phase transition by terahertz photoconductivity
           in HgTe‐based transistors
    • Authors: A. M. Kadykov; C. Consejo, M. Marcinkiewicz, L. Viti, M. S. Vitiello, S. S. Krishtopenko, S. Ruffenach, S. V. Morozov, W. Desrat, N. Dyakonova, W. Knap, V. I. Gavrilenko, N. N. Mikhailov, S. A. Dvoretsky, F. Teppe
      Abstract: We have found the possibility to probe the magnetic field‐driven topological phase transition in HgTe‐based transistors by measuring their Terahertz photoconductivity response. At the critical magnetic field to which zero‐mode Landau levels cross, we have observed a pronounced photoconductivity peak independent on incident frequency and carrier concentration. Our results pave the way towards terahertz topological field effect transistors. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:13:04.847987-05:
      DOI: 10.1002/pssc.201510264
       
  • Molecular beam epitaxy of free‐standing bulk wurtzite
           AlxGa1‐xN layers using a highly efficient RF plasma source
    • Abstract: Recent developments with group III nitrides suggest AlxGa1‐xN based LEDs can be new alternative commercially viable deep ultra‐violet light sources. Due to a significant difference in the lattice parameters of GaN and AlN, AlxGa1‐xN substrates would be preferable to either GaN or AlN for ultraviolet device applications. We have studied the growth of free‐standing wurtzite AlxGa1‐xN bulk crystals by plasma‐assisted molecular beam epitaxy (PA‐MBE) using a novel RF plasma source. Thick wurtzite AlxGa1‐xN films were grown by PA‐MBE on 2‐inch GaAs (111)B substrates and were removed from the GaAs substrate after growth to provide free standing AlxGa1‐xN samples. Growth rates of AlxGa1‐xN up to 3 µm/h have been demonstrated. Our novel high efficiency RF plasma source allowed us to achieve free‐standing bulk AlxGa1‐xN layers in a single day's growth, which makes our MBE bulk growth technique commercially viable. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:13:03.548912-05:
      DOI: 10.1002/pssc.201510166
       
  • Towards industrialisation of GaN‐on‐Si based high brightness
           blue LEDs
    • Authors: Liyang Zhang; Wei Sin Tan, Simon Westwater, Antoine Pujol, Andrea Pinos, Samir Mezouari, Kevin Stribley, John Whiteman, John Shannon, Keith Strickland
      Abstract: The manufacturability of blue LED structures grown on 6‐inch Si (111) substrates is reported. The totally epi‐structure thickness is only 3.75 μm, which allows faster epitaxy process throughput and lower manufacturing costs. Well controlled strain engineering leads to a room temperature wafer bow of 0 ± 5 μm and a highly uniform photoluminescence wavelength standard deviation of 1.1 nm. XRD FWHM (002) and (102) are 380 and 390 arcsec, respectively. For a blue 1×1 mm2 vertical thin film die with silicone dome lens, the optical light output power of 563 mW at an operating voltage of 3.05 V is achieved at 350 mA. Excellent leakage current (IR) yield is achieved with over 95% of dies exhibiting IR < 0.1 μA at ‐5 V. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:13:02.54032-05:0
      DOI: 10.1002/pssc.201510168
       
  • Fabrication of nanocomposites based on silicon nanowires and study of
           their optical properties
    • Authors: Stanislau Niauzorau; Kseniya Girel, Alexander Sherstnyov, Eugene Chubenko, Hanna Bandarenka, Vitaly Bondarenko
      Abstract: This article presents the results on a fabrication of silicon nanowires by a two‐step metal‐assisted chemical etching. Morphological and optical properties of the obtained silicon nanostructures depending on the type and resistivity of the initial silicon wafer have been studied. In addition, we have used the silicon nanowires as templates for zinc oxide and silver deposition. The resulting nanocomposites have been shown to demonstrate intensive photoluminescence and activity in the surface enhanced Raman scattering respectively. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:13:01.616803-05:
      DOI: 10.1002/pssc.201510219
       
  • Low pressure MOVPE growth and characterization of ZnTe homoepitaxial
           layers
    • Authors: Mitsuhiro Nishio; Katsuhiko Saito, Masakatsu Abiru, Eiichiro Mori, Yasuhiro Araki, Daichi Tanaka, Tooru Tanaka, Qixin Guo
      Abstract: The growth rate and photoluminescence (PL) spectrum of ZnTe homoepitaxial layer grown at a reactor pressure of 500 Torr by metalorganic vapor phase epitaxy have been clarified as a function of substrate temperature. An optimum substrate temperature for obtaining ZnTe layers with better PL property is determined by taking into account the growth rate behavior. Furthermore, the growth rate, PL spectrum, surface roughness and surface morphology of ZnTe layer have also been investigated by varying reactor pressure. With increasing reactor pressure, both the PL property and surface roughness of ZnTe layer are improved and subsequently become degraded, according as the growth rate increases monotonically and then shows saturated tendency. Change in the surface morphology of ZnTe layer with the increase of reactor pressure resembles that with the decrease of substrate temperature, probably due to the change from mass‐transport regime to surface kinetics one. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:13:00.722975-05:
      DOI: 10.1002/pssc.201510240
       
  • Luminescence dynamics of hybrid ZnO nanowire/CdSe quantum dot structures
    • Abstract: Colloidal CdSe quantum dots (QDs) functionalized with different organic linker molecules are attached to ZnO nanowires (NWs) to investigate the electron transfer dynamics between dots and wires. After linking the quantum dots to the nanowires, the photo‐induced electron transfer (PET) from the QDs into the NWs becomes visible in the PL transients by a decrease of dot luminescence decay time. The different recombination paths inside the QDs and the PET process are discussed in the framework of a rate equation model. Photoconductivity studies confirm the electron transfer by demonstrating a strong enhancement of the wire photocurrent under light irradiation into the dot transition. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:12:59.796045-05:
      DOI: 10.1002/pssc.201510253
       
  • Photoconductive properties of undoped and nitrogen‐doped ZnO single
           crystals in various ambiences
    • Authors: Takami Abe; Shuzo Takahashi, Shuhei Kamada, Akira Nakagawa, Tetsuya Chiba, Michiko Nakagawa, Shigeki Chiba, Yasuhiro Kashiwaba, Masahiro Daibo, Ikuo Niikura, Yasube Kashiwaba, Hiroshi Osada
      Abstract: The effects of ambiences on photoconductive properties of the Zn‐face of undoped ZnO and nitrogen‐doped ZnO (ZnO:N) single crystals are described. Oxygen (O2) gas affected the photocurrent spectra of the Zn‐face of both single crystals. The photocurrent was smallest in O2 gas and was largest in the vacuum ambience. The influence of ambience was very small in the visible light region but was large in the UV region. Regardless of the ambience, photocurrent of the Zn‐face of ZnO:N showed no sensitivity in the visible region. The decay time response of undoped ZnO and ZnO:N single crystals was also affected by the ambience. Decay time responses of both single crystals were fastest in O2 gas and were slowest in the vacuum ambience. The decay time response of the ZnO:N single crystal was faster than that of the undoped ZnO single crystal. These results showed that the effect of oxygen‐mediated surface recombination is strong in both large single crystals with very small surface‐to‐volume ratio and no grain boundary effect. The results also showed that doped nitrogen decreases the density of electron and hole traps near the surface region of the crystals. It is thought that steepness of band bending near the surface of a ZnO:N single crystal is smaller than that of an undoped ZnO single crystal. In conclusion, the Zn‐face of a ZnO:N single crystal sealed with O2 gas is useful as a photoconductive type UV sensor. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:12:58.907655-05:
      DOI: 10.1002/pssc.201510260
       
  • Unintentional nitrogen incorporation in ZnO nanowires detected by electron
           paramagnetic resonance spectroscopy
    • Authors: J. E. Stehr; W. M. Chen, N. K. Reddy, C. W. Tu, I. A. Buyanova
      Abstract: Unintentional incorporation of nitrogen in ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition is unambiguously proven by electron paramagnetic resonance spectroscopy. The nitrogen dopants are suggested to be provided from contaminations in the source gases. The majority of incorporated nitrogen atoms are concluded to reside at oxygen sites, i.e. in the atomic configuration of nitrogen substituting for oxygen (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in a bulk material. This implies that the defect formation energy at the NW surface could be lower than its bulk value, consistent with previous theoretical predictions. The obtained results underline that nitrogen can be easily incorporated in ZnO nanostructures which may be of advantage for realizing p‐type conducting ZnO via N doping. On the other hand, the awareness of this process can help to prevent such unintentional doping in structures with desired n‐type conductivity. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T03:12:58.007038-05:
      DOI: 10.1002/pssc.201510261
       
  • Analysis of lags and current collapse in field‐plate AlGaN/GaN HEMTs
           with deep acceptors in a buffer layer
    • Authors: Naohiro Noda; Ryouhei Tsurumaki, Kazushige Horio
      Abstract: We make 2‐D transient simulations of field‐plate AlGaN/GaN HEMTs with a semi‐insulating buffer layer, where a deep acceptor above the midgap is considered. It is studied how the deep acceptor and the field plate affect lag phenomena and current collapse. It is shown that the drain lag and current collapse could be reduced by introducing a field plate, as in a case with a deep acceptor compensated by a deep donor in the buffer layer. This reduction occurs because electron trapping by the deep acceptors is weakened by the field plate. The dependence on insulator thickness under the field plate is also studied, suggesting that there is an optimum thickness of insulator to minimize the current collapse of AlGaN/GaN HEMTs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-25T02:42:25.357108-05:
      DOI: 10.1002/pssc.201510156
       
  • Current density dependence of transition energy in blue InGaN/GaN MQW LEDs
    • Authors: F. Zhang; M. Ikeda, K. Zhou, Z. S. Liu, J. P. Liu, S. M. Zhang, H. Yang
      Abstract: In this paper we report on the transition energy in InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) under various injection current density from 2 A/cm2 to 200 A/cm2. Various effects including strain, quantum confined Stark effect (QCSE), screening effect by carriers, bandgap renormalization, Stokes‐like shift, band‐filling effect, and quantum levels in triangular quantum wells, are considered quantitatively and analyzed comprehensively. By comparing these effects altogether, we found that when the In‐content in quantum wells is fixed, the transition energy is mainly determined by QCSE and quantum level energy, between which QCSE overweighs the other. The transition energy shift with current density is also mainly governed by the screening effect of QCSE, with detailed competition between band tailing and filling. Additional effect, the coupling between adjacent quantum wells, is investigated in this paper. The coupling between quantum wells with various barrier thicknesses is compared. By calculating the wavefunctions self‐consistently, it is found that for InGaN/GaN MQWs with 5 nm quantum barriers (QBs), the coupling of electron wavefunctions leads to about 2 meV difference in transition energy. While for the MQWs with 3 nm QBs, the influence of electron wave‐function overlap on transition energy is 12.9 meV, which is more significant than that of 5 nm QB case. However, for hole wavefunctions, the coupling effect is too small to be considered, which is mainly due to the much larger effective mass. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-17T04:10:07.772128-05:
      DOI: 10.1002/pssc.201600005
       
  • Characterization of carrier concentration in ZnO nanowires by scanning
           capacitance microscopy
    • Abstract: Scanning capacitance microscopy (SCM) has been investigated on Ga doped ZnO staircase multi‐layers grown by molecular beam epitaxy (MBE) and ZnO NWs grown by chemical bath deposition (CBD). It is found that SCM data amplitude experiences a monotonic decrease with increasing Ga concentration from 2×1017 cm‐3 to 3×1020 cm‐3, indicating SCM being an appropriate technique for two dimensional dopant/carrier profiling in ZnO at nanoscale. For ZnO nanowires (NWs), a planariz‐ation process was developed based on dip‐coating of silica sol‐gel and chemical‐mechanical polishing. Then ZnO NWs were well detected from the silica matrix by SCM and the residual carrier concentration inside them was estimated through calibration method to be between 5×1017 cm‐3 and 2×1018 cm‐3. Finally, the result was compared with that obtained from conventional capacitance‐voltage (C‐V) measrement and their difference was discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-17T04:10:06.765556-05:
      DOI: 10.1002/pssc.201510268
       
  • Role of electron‐phonon interaction in the temperature dependence of
           the phonon mode frequency in II‐VI compound alloys
    • Abstract: We present an experimental investigation of the temperature dependence of the TO‐phonon mode frequencies for the HgTe‐based II‐VI semiconductor solid solutions. In the case of the ternary Hg0.9Zn0.1Te solid solution was shown a discontinuity in the temperature dependence of the HgTe‐like TO‐mode and of the ZnTe‐like TO‐mode, similar to the Hg0.885Cd0.115Te system [Sheregii et al., Phys. Rev. Lett. 102, 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron‐phonon e‐p interaction which in this case is returnable the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg0.885Cd0.115Te and Hg0.9Zn0.1Te containing Dirac point (Eg = Γ6–ΓΓ8 = 0) although one of the two constants describing the anharmonic shift of the HgTe‐like mode should be positive what is abnormal too. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-17T04:10:05.464365-05:
      DOI: 10.1002/pssc.201510236
       
  • Observation of in‐situ reciprocal lattice evolution of AlGaN/InGaN
           on Si (111) through GaN and AlN interlayers by RHEED and reflectance
    • Authors: Ankush Bag; Subhashis Das, Dhrubes Biswas
      Abstract: Due to the wave‐particle duality of high energy electron beam, RHEED describes a thin film surface through the interaction of reciprocal lattice rod (RLR) of the film. The RLR spacing of the crystal has been computed using RHEED streak spacing on a fluorescent screen. Present evolution study of RLR spacing has been performed for AlGaN/InGaN heterostructure on thick GaN buffer layer during plasma‐assisted molecular beam epitaxy. Effect of composition, strain and temperature on the crystal has been identified as the function of lattice spacing during the growth. The calibrated reflectivity of LED signal has also been employed to map the thickness of different growing epilayers. RLR spacing decreases for interlayer GaN as compared to AlN. Initially, the RLR spacing of GaN buffer decreases more as compared to interlayer GaN owing to its increased growth temperature after the interlayer AlN. The RLR spacing of GaN again gradually increases with decrement of growth temperature up to the InGaN channel layer. The InGaN RLR spacing decreases again which attributes to the relaxation of InGaN on GaN. Additionally, AlGaN reveals strained state to InGaN in combination with effect of high growth temperature. The phenomena result in additional decrement of lattice distance in reciprocal space. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-17T03:40:05.498282-05:
      DOI: 10.1002/pssc.201510202
       
  • Effect of electron blocking layers on the conduction and valence band
           profiles of InGaN/GaN LEDs
    • Abstract: In this paper we investigate the effect of including an electron blocking layer between the quantum well active region and the p‐type layers of a light emitting diode has on the conduction and valence band profile of a light emitting diode. Two light emitting diode structures with nominally identical quantum well active regions one containing an electron blocking layer and one without were grown for the purposes of this investigation. The conduction and valence band profiles for both structures were then calculated using a commercially available Schrödinger‐Poisson calculator, and a modification to the electric field across the QWs observed. The results of these calculations were then compared to photoluminescence and photoluminescence time decay measurements. The modification in electric field across the quantum wells of the structures resulted in slower radiative recombination in the sample containing an electron blocking layers. The sample containing an electron blocking layer was also found to exhibit a lower internal quantum efficiency, which we attribute to the observed slower radiative recombination lifetime making radiative recombination less competitive. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-02-17T03:40:04.634358-05:
      DOI: 10.1002/pssc.201510188
       
  • Contents: Phys. Status Solidi C 4/2016
    • Pages: 131 - 132
      PubDate: 2016-04-20T05:43:34.534437-05:
      DOI: 10.1002/pssc.201670120
       
  • Electronic and optical nature of silicon nanostructures: doping, interface
           effects and strain
    • Pages: 133 - 133
      Abstract: This proceedings volume of phys. status solidi (c) contains research presented in Symposium P at the EMRS 2015 Fall Meeting in Warsaw, Poland. The symposium focused on silicon nanostructures in all dimensionalities and intended to cover theoretical, experimental and application aspects with emphasize on doping, surface/interface effects, and advanced metrology methods. Besides the well‐known size dependent quantum confinement effects, Si nanostructures are highly susceptible to their surrounding and any kind of impurities. Many key material properties change due to the influence of an embedding matrix or surface terminating groups. On the other hand, well established technological concepts such as majority carrier generation by impurity doping with e.g. phosphorous or boron are impeded in Si nanostructures due to self‐purification, statistical problems, or failing dopant ionization due to quantum confinement. In the course of the symposium, details on these problems but also approaches on how to circumvent or exploit these effects for novel functionalities or applications were presented and discussed. We thank all invited and contributed speakers as well as all presenters of posters. Furthermore, we appreciate the help and support of our sponsors and the editorial team of pss (c). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-04-20T05:43:34.784618-05:
      DOI: 10.1002/pssc.201670121
       
  • Stabilization of silicon nanoparticles in colloidal solutions
    • Pages: 142 - 145
      Abstract: Silicon nanoparticles, apart from their potential use in optoelectronics or photovoltaics, are very promising also for biological applications. Typical requirements for such nanoparticles used in biological research differ from that for optoelectronics ‐ the aim is to prepare aqueous or isotonic (such as phosphate buffered saline ‐ PBS) colloidal solutions of stable, uniform and strongly luminescing nanoparticles, with sizes suitable for the process of cell endocytosis, ideally in the range of tens to hundreds of nanometers. We have prepared colloidal solutions of luminescing porous silicon nanoparticles (size around 100 nm) obtained by electrochemical etching of silicon wafers. Adding hydrogen peroxide to the etching bath results in oxidized nanoparticle surface and hydrophilic behavior. However, the as‐prepared samples agglomerate – the dynamic light scattering revealed the increase of the agglomerates size from 60 nm in fresh samples to 400 nm in one‐month‐old samples. The tendency to agglomerate was confirmed by zeta‐potential measurements. The first attempt to steric stabilization by bovine serum albumin, glycine, glutamic acid and dextran is presented, where the increased stability was observed in the glycine‐ terminated samples. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-01-29T05:30:22.143788-05:
      DOI: 10.1002/pssc.201510217
       
  • Gas phase silanization for silicon nanowire sensors and other
           lab‐on‐a‐chip systems
    • Authors: Annina M. Steinbach; Tanja Sandner, Boris Mizaikoff, Steffen Strehle
      Pages: 135 - 141
      Abstract: Designing a microfabrication process for lab‐on‐a‐chip systems can at times be challenging, and the need to integrate a chemical surface modification reaction into this process can limit the options. Therefore, a robust set‐up and protocol for the gas phase modification has been developed that can be variably integrated into microfabrication processes. The main improvement compared to similar methods is, besides easy and versatile sample handling, the integration of a continuous argon flow percolating through the liquid organosilane, and impinging directly the surface tobe modified. This measure reduces the argon consumption drastically compared to current reaction schemes, while keeping short reaction periods. Silicon substrates were modified using 3‐mercaptopropyltrimethoxysilane (MPTMS) and 3‐aminopropyltrimethoxysilane (APTMS), thoroughly studied for different reaction stages, and compared to surfaces modified via a common solvent‐based procedure from isopropanolic solution. Water contact angle measurements, infrared spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy verified the successful deposition of the alkylsilane. Additionally, silicon nanowires were assembled, exemplary for a lab‐on‐a‐chip system, in a liquid gate field‐effect‐transistor configuration, and electrically characterized. The devices showed the expected response to applied liquid gate potentials before and after the modification and exhibited characteristic changes in the transconductance curve. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2015-11-19T06:50:22.672789-05:
      DOI: 10.1002/pssc.201510211
       
 
 
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