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Journal Cover Semiconductors and Semimetals
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   ISSN (Print) 0080-8784
   Published by Elsevier Homepage  [3043 journals]
  • Charge Carrier Dynamics in Metal Oxide Photoelectrodes for Water Oxidation
    • Authors: Andreas Kafizas; Robert Godin; James R. Durrant
      Abstract: Publication date: Available online 24 March 2017
      Source:Semiconductors and Semimetals
      Author(s): Andreas Kafizas, Robert Godin, James R. Durrant
      Since the first demonstration by Fujishima and Honda of photoelectrochemical water splitting, this route to renewable hydrogen fuel has been pursued with great endeavor. The oxidation of water has been identified as the kinetic “bottleneck” limiting the overall reaction efficiency, thus there is a pressing need to develop more active photocatalysts that can drive this reaction. Some of the most promising materials that can oxidize water are metal oxide semiconductors. The most popular metal oxide photoanodes for water oxidation are TiO2, α-Fe2O3, BiVO4, and WO3, but even state-of-the-art examples show photocatalytic currents far shy of their theoretical maximum. Numerous strategies have been developed to improve their activity, which include nanostructuring, the use of surface cocatalysts, pacifying surface states, and forming heterojunction architectures. This review focuses on the use of TiO2, α-Fe2O3, BiVO4, and WO3 as photoanodes for water oxidation and studies that probe charge carrier dynamics. Emphasis is placed on evaluation of electrodes under operating conditions. During this review, we will discuss each metal oxide in turn and use these studies of charge carrier dynamics to build an inclusive and complimentary picture of the processes that occur during water oxidation. There will be a general view on how changes in material structure impact charge carrier dynamics and the kinetics of water oxidation.

      PubDate: 2017-03-25T18:20:39Z
      DOI: 10.1016/bs.semsem.2017.02.002
  • Series Page
    • Abstract: Publication date: 2017
      Source:Semiconductors and Semimetals, Volume 96

      PubDate: 2017-01-09T18:10:39Z
  • Contents of Volumes in this Series
    • Abstract: Publication date: 2017
      Source:Semiconductors and Semimetals, Volume 96

      PubDate: 2017-01-09T18:10:39Z
  • Materials Challenges of AlGaN-Based UV Optoelectronic Devices
    • Authors: M.H. Crawford
      Abstract: Publication date: Available online 27 December 2016
      Source:Semiconductors and Semimetals
      Author(s): M.H. Crawford
      Over the past 15 years, tremendous progress has been made in AlGaN-based optoelectronic devices, including light-emitting diodes (LEDs) and laser diodes (LDs) in the deep UV (DUV) region of the spectrum. However, performance levels are still lagging those of InGaN light emitters in the visible region due to outstanding materials challenges of the wider band gap AlGaN alloys. In this review, we focus on two of the most significant materials roadblocks to higher-performing AlGaN devices: doping and substrates. For each topic, we present the state of the art as well as exploratory concepts for enabling future device advances. On the topic of p-type doping, we describe the concomitant challenges of large acceptor activation energy, dopant solubility, and compensating defects and describe growth optimization approaches to mitigate those issues. We further present polarization engineering approaches to enhance p-type doping, including Mg-doped superlattices, distributed polarization doping, and tunnel-junction-enabled LEDs. Limitations to n-type doping for high-Al-composition AlGaN alloys are also reviewed along with insights into the origins these doping challenges. On the topic of substrates, we report the challenges of heteroepitaxy on lattice-mismatched substrates, describe the impact of high dislocation densities on AlGaN emitters, and overview strategies for dislocation reduction. State-of-the-art UV LD performance, enabled by these defect reduction strategies, is also presented. Limitations due to electrically insulating substrates are described as well as promising approaches to achieving vertical-injection UV light emitters. Overall, common themes of employing material and device structures at the micro/nanoscale and leveraging the polarization properties of nitride heterostructures reveal approaches for realizing next-generation UV light emitters.

      PubDate: 2016-12-30T12:51:33Z
      DOI: 10.1016/bs.semsem.2016.11.001
  • Growth of High-Quality AlN on Sapphire and Development of AlGaN-Based
           Deep-Ultraviolet Light-Emitting Diodes
    • Authors: Hirayama
      Abstract: Publication date: Available online 23 December 2016
      Source:Semiconductors and Semimetals
      Author(s): H. Hirayama
      222–351nm AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) are demonstrated, which has been achieved by the development of crystal growth techniques for wide-bandgap AlN and AlGaN. Significant increases in internal quantum efficiency have been achieved for AlGaN quantum-well emissions by introducing low-threading dislocation density AlN grown by an NH3 pulsed-flow multilayer growth method. Electron injection efficiency of the DUV LED was significantly increased by introducing multiquantum barrier. Light extraction efficiency was also improved by using a transparent p-AlGaN contact layer. The maximum external quantum efficiency was increased up to 7% for a 279-nm DUV LED.

      PubDate: 2016-12-30T12:51:33Z
  • Dynamic Atomic Layer Epitaxy of InN on/in GaN and Its Application for
           Fabricating Ordered Alloys in Whole III-N System
    • Authors: K. Kusakabe; A. Yoshikawa
      Abstract: Publication date: Available online 30 November 2016
      Source:Semiconductors and Semimetals
      Author(s): K. Kusakabe, A. Yoshikawa
      A unique epitaxial process, dynamic atomic layer epitaxy (D-ALEp), has been proposed and developed to fabricate coherent monolayer-InN on/in GaN-matrix nanostructures. The D-ALEp utilizes self-limiting and self-ordering surface processes but differs from typical atomic layer epitaxy, because the growth front in D-ALEp dynamically changes stoichiometry or metal coverage through adsorption/desorption of adatoms at a high-temperature regime. The growth front is precisely traced by in situ spectroscopic ellipsometry monitoring, where atomic scale surface behavior is easily/accurately understood by our smart style of an imaginary part of pseudodielectric function normalized by an adlayer thickness (Δ〈ɛ 2〉), instead of complicated spectral analysis. In this chapter, the authors briefly introduce the D-ALEp and also our prime objective to establish ordered alloys in a whole III-nitride system. Subsequently, the authors discuss growth kinetics of monolayer-InN on/in GaN-matrix by the D-ALEp which has been developed in molecular beam epitaxy (MBE) at the beginning to overcome highly mismatched problems in an InN/GaN system, and then investigated in metalorganic vapor phase epitaxy (MOVPE) as well. Finally, the authors represent an extension of the D-ALEp toward fabrication of III-N ordered alloys. The authors have demonstrated InN/GaN ordered alloys grown by MBE and (InN/GaN)-layer/pn-GaN solar cells grown by MOVPE. The authors further discuss a future prospect of AlN/GaN and AlN/InN ordered alloys for potential application to high electron mobility transistors (HEMTs).

      PubDate: 2016-12-01T05:08:30Z
      DOI: 10.1016/bs.semsem.2016.10.001
  • III-N Wide Bandgap Deep-Ultraviolet Lasers and Photodetectors
    • Authors: T. Detchprohm; X. Li; S.-C. Shen; P.D. Yoder; R.D. Dupuis
      Abstract: Publication date: Available online 4 November 2016
      Source:Semiconductors and Semimetals
      Author(s): T. Detchprohm, X. Li, S.-C. Shen, P.D. Yoder, R.D. Dupuis
      The III-N wide-bandgap alloys in the AlInGaN system have many important and unique electrical and optical properties which have been exploited to develop deep-ultraviolet (DUV) optical devices operating at wavelengths <300nm, including light-emitting diodes, optically pumped lasers, and photodetectors. In this chapter, we review some aspects of the development and current state of the art of these DUV materials and devices. We describe the growth of III-N materials in the UV region by metalorganic chemical vapor deposition as well as the properties of epitaxial layers and heterostructure devices. In addition, we discuss the simulation and design of DUV laser diodes, the processing of III-N optical devices, and the description of the current state of the art of DUV lasers and photodetectors.

      PubDate: 2016-11-09T20:08:03Z
      DOI: 10.1016/bs.semsem.2016.09.001
  • Nitride Semiconductor Nanorod Heterostructures for Full-Color and
           White-Light Applications
    • Authors: S. Gwo; Y.J. Lu; H.W. Lin; C.T. Kuo; C.L. Wu; M.Y. Lu; L.J. Chen
      Abstract: Publication date: Available online 31 October 2016
      Source:Semiconductors and Semimetals
      Author(s): S. Gwo, Y.J. Lu, H.W. Lin, C.T. Kuo, C.L. Wu, M.Y. Lu, L.J. Chen
      Development of full-color and white light-emitting diodes (LEDs) and laser diodes (LDs) is tremendously important for energy-efficient lighting and advanced display applications. At present, the InGaN/GaN semiconductor heterostructure system is considered as the most promising device candidate for these applications because the direct band gap of In x Ga1− x N spans from the near-infrared (NIR) to the near-UV, including the complete visible spectrum. However, there are severe issues related to structural imperfection and polarization effects in high-In-content InGaN/GaN semiconductor heterostructures, resulting in low emission efficiency in the long-wavelength spectral region (beyond blue). To overcome the formidable material challenges in InGaN/GaN semiconductor heterostructures, many studies reported recently have suggested a promising solution based on full-color and white solid-sate emitters using one-dimensional (1D) nitride semiconductor nanostructures (nanorods, nanowires, nanocolumns, nanopillars, nanotubes, etc.). Especially, vertically self-aligned GaN nanorod arrays have been applied as strain-free or strain-reduced growth templates for heteroepitaxial growth of InGaN/GaN nanorod heterostructures emitting in the full visible spectrum. Moreover, 1D nitride semiconductor nanorod heterostructures can be grown by plasma-assisted molecular beam epitaxy and metal-organic vapor phase epitaxy with well-defined axial/radial geometries and abruptly modulated compositions to achieve unique device functionalities. In this chapter, we give a detailed discussion about nitride semiconductor nanorod heterostructures, including polarization effects, nanorod growth and polarity control, doping and surface properties, nanorod heterojunction band alignments, axial nanorod heterostructures for full-color and tunable white LEDs, as well as green and full-color core–shell nanorod plasmonic nanolasers. Some future perspectives will also be given for both fundamental studies and new device applications of nitride semiconductor nanorod heterostructures.

      PubDate: 2016-11-02T14:43:53Z
      DOI: 10.1016/bs.semsem.2016.09.002
  • Growth and Structural Characterization of Self-Nucleated III-Nitride
    • Authors: T. Auzelle; B. Daudin
      Abstract: Publication date: Available online 24 September 2016
      Source:Semiconductors and Semimetals
      Author(s): T. Auzelle, B. Daudin
      We review the self-nucleation process of GaN nanowires grown by plasma-assisted molecular beam epitaxy. The role of GaN/Si (111) and of AlN/Si (111) interface chemistry is shown to be determinant and is analyzed in details. The crucial issue of GaN crystalline polarity is shown to depend on both interface chemistry and GaN facet surface energy. The structural properties of self-nucleated GaN NWs are next discussed, with a peculiar focus on stacking faults and inversion domains.

      PubDate: 2016-09-28T18:34:23Z
      DOI: 10.1016/bs.semsem.2016.08.004
  • Development of Deep UV LEDs and Current Problems in Material and Device
    • Authors: M. Shatalov; R. Jain; T. Saxena; A. Dobrinsky; M. Shur
      Abstract: Publication date: Available online 10 September 2016
      Source:Semiconductors and Semimetals
      Author(s): M. Shatalov, R. Jain, T. Saxena, A. Dobrinsky, M. Shur
      We review progress in development of deep ultraviolet light-emitting diodes and discuss key factors currently affecting device performance. Heteroepitaxial growth of AlN and AlGaN by high-temperature epitaxy has resulted in significant improvement of LED efficiency through reduction of density of nonradiative defects. Importance of alloy composition fluctuations is discussed based on results of time-resolved temperature-dependent photoluminescence and light-induced grating measurements of Al0.6Ga0.4N layers with different density of dislocations. Improvement of LED performance achieved by suppression of the nonradiative recombination in epitaxial structures with dislocation density reduced to below 5×108 cm−2, transparent LED structure design, and optimized UV-reflective contacts. Aspects of the LED chip design are discussed for further improvements of light extraction and LED output power. Research is now under way to use these devices for numerous applications including water and air purification, sterilization, biological threat identification, applications in medicine, biology, industrial processes, defense, and homeland security.

      PubDate: 2016-09-19T05:29:48Z
      DOI: 10.1016/bs.semsem.2016.08.002
  • InN Nanowires: Epitaxial Growth, Characterization, and Device Applications
    • Authors: Zhao
      Abstract: Publication date: Available online 6 September 2016
      Source:Semiconductors and Semimetals
      Author(s): S. Zhao, Z. Mi
      In this chapter, we review the recent progress made on the growth, characterization, and device applications of InN nanowires. Early research on InN nanowires is limited by their n-type degenerate characteristics, wherein the Fermi level is located deep in the conduction band, with the presence of high-density surface electrons. Recently, with the improved molecular beam epitaxy growth process, intrinsic and p-type InN nanowires have been realized, which are free of surface electron accumulation and Fermi-level pinning, providing great promise for a broad range of devices and applications.

      PubDate: 2016-09-10T00:56:51Z
  • Selective Area Growth of InGaN/GaN Nanocolumnar Heterostructures by
           Plasma-Assisted Molecular Beam Epitaxy
    • Authors: S. Albert; A.M. Bengoechea-Encabo; M.Á. Sánchez-García; E. Calleja
      Abstract: Publication date: Available online 3 September 2016
      Source:Semiconductors and Semimetals
      Author(s): S. Albert, A.M. Bengoechea-Encabo, M.Á. Sánchez-García, E. Calleja
      The aim of this work is to gain insight into the selective area growth (SAG) of InGaN nanostructures by plasma-assisted molecular beam epitaxy, focusing on their potential as building blocks for next-generation LEDs. Several nanocolumn (NC)-based approaches such as standard axial InGaN/GaN structures and InGaN/GaN core–shell structures are discussed. The first section reports on the growth and characterization of ordered InGaN NCs as well as light-emitting diodes grown on c-plane GaN/sapphire templates. In particular, the growth mechanism of green-emitting InGaN/GaN NCs is discussed. In order to enable white light emission the stacking of red, green, and blue emitting segments is used to achieve the monolithic integration of these structures in one single InGaN NC allowing for the fabrication of ordered broad spectrum emitters. As alternative to axial InGaN/GaN nanostructures, the next section reports on the growth and characterization of InGaN/GaN core–shell structures with emission at around 3.0eV. Furthermore, the successful fabrication of a core–shell pin diode structure is demonstrated. Finally, the SAG of In(Ga)N/GaN NCs on Si(111) substrates is presented. Ordered In(Ga)N/GaN NCs emitting from ultraviolet (3.2eV) to infrared (0.78eV) were grown on top of GaN-buffered Si substrates.

      PubDate: 2016-09-05T02:02:32Z
      DOI: 10.1016/bs.semsem.2016.08.003
  • III-Nitride Electrically Pumped Visible and Near-Infrared Nanowire Lasers
           on (001) Silicon
    • Authors: P. Bhattacharya; A. Hazari; S. Jahangir; W. Guo; T. Frost
      Abstract: Publication date: Available online 25 August 2016
      Source:Semiconductors and Semimetals
      Author(s): P. Bhattacharya, A. Hazari, S. Jahangir, W. Guo, T. Frost
      Ga(Al,In)N nanowires can be grown catalyst-free on silicon and other substrates. The diameter of individual nanowires in an array and the array density can be varied over wide ranges. Single or multiple InGaN disks can be inserted in Ga(Al)N nanowires and the alloy composition in the disk can be varied to tune the luminescence from visible to near infrared. The nanowires have other desirable properties such as very low density of extended defects and minimal strain. They can also be selectively doped n- and p-type, thereby enabling the formation of junction diodes as with planar materials. With adequate passivation the internal quantum efficiency of GaN nanowires and the InGaN disks, which behave as quantum dots, is higher than 50%. We have exploited these favorable attributes to design, epitaxially grow and characterize the first edge-emitting electrically pumped GaN/In(Ga)N disk-in-nanowire lasers with the peak of the coherent emission varying from 533nm (green) to 1.3μm. It may be noted that light sources with emission at wavelengths larger than 590nm cannot be realized with InGaN/GaN quantum wells (QWs). The characteristics of the nanowire heterostructures and the steady-state and small-signal modulation characteristics of the lasers are described. The threshold current, characteristic temperature T 0, differential gain, and modulation bandwidth of the nanowire lasers are comparable to state-of-the-art QW and quantum dot lasers.

      PubDate: 2016-08-26T14:45:29Z
      DOI: 10.1016/bs.semsem.2016.07.002
  • Exploring the Next Phase in Gallium Nitride Photonics: Cubic Phase Light
           Emitters Heterointegrated on Silicon
    • Authors: C. Bayram; R. Liu
      Abstract: Publication date: Available online 29 July 2016
      Source:Semiconductors and Semimetals
      Author(s): C. Bayram, R. Liu
      Gallium nitride (GaN) materials are the backbone of emerging solid-state lighting. To date, GaN research has been primarily focused on hexagonal phase devices due to the natural crystallization. This approach limits the output power and efficiency of light-emitting diodes (LEDs), particularly in the green spectrum. However, GaN can also be engineered to be in cubic phase. Cubic GaN has a lower bandgap (~200meV) than hexagonal GaN that enables green LEDs much easily. Besides, cubic GaN has more isotropic properties (smaller effective masses, higher carrier mobility, higher doping efficiency, and higher optical gain than hexagonal GaN) and cleavage planes. Due to phase instability, however, cubic phase materials and devices have remained mostly unexplored. Here we review a new method of cubic phase GaN generation: hexagonal-to-cubic phase transition, based on novel nanopatterning. We report a new crystallographic modeling of this hexagonal-to-cubic phase transition and systematically study the effects of nanopatterning on the GaN phase transition via transmission electron microscopy, temperature-dependent cathodoluminescence, and electron backscatter diffraction experiments. In summary, silicon-integrated cubic phase GaN light emitters offer a unique opportunity for exploration in next-generation photonics.

      PubDate: 2016-08-06T05:20:06Z
      DOI: 10.1016/bs.semsem.2016.07.001
  • Al(Ga)N Nanowire Deep Ultraviolet Optoelectronics
    • Authors: Zhao
      Abstract: Publication date: Available online 9 July 2016
      Source:Semiconductors and Semimetals
      Author(s): S. Zhao, Z. Mi
      In this chapter, we review the recent progress made on the growth and characterization of Al(Ga)N nanowires and related optoelectronic devices, with a focus on Al-rich Al(Ga)N nanowires and their applications for deep ultraviolet (UV) light-emitting diodes (LEDs) and lasers. The achievement of nearly defect-free Al(Ga)N nanowires by molecular beam epitaxy, the realization of efficient p-type conduction in AlN and Al-rich ternary AlGaN nanowires, and the demonstration of high efficiency Al(Ga)N nanowire LEDs are described. Moreover, the presence of quantum-confined nanostructures in ternary AlGaN nanowires and the first demonstrations of electrically injected semiconductor lasers in the UV-B and UV-C bands are also presented.

      PubDate: 2016-08-06T05:20:06Z
  • Series Page
    • Abstract: Publication date: 2016
      Source:Semiconductors and Semimetals, Volume 95

      PubDate: 2016-08-06T05:20:06Z
  • Contents of Volumes in this Series
    • Abstract: Publication date: 2016
      Source:Semiconductors and Semimetals, Volume 95

      PubDate: 2016-08-06T05:20:06Z
  • 2D Boron Nitride: Synthesis and Applications
    • Authors: G.R. Bhimanapati; N.R. Glavin J.A. Robinson
      Abstract: Publication date: Available online 14 June 2016
      Source:Semiconductors and Semimetals
      Author(s): G.R. Bhimanapati, N.R. Glavin, J.A. Robinson
      Hexagonal boron nitride (h-BN), a layered material isostructural to graphite, has similar exotic properties like graphite. With single atom thick and alternating boron and nitrogen atoms in its atomic structure, h-BN is an insulator with band gap ~5.9eV. As monolayer h-BN or boron nitride nanosheet (BNNS) has been studied for over a decade, a brief overview about the structure and stability is provided. In addition, this chapter provides insight into the different forms of h-BN focusing mainly on the synthesis of single layer h-BN or BNNS via different techniques such as mechanical exfoliation, solvent exfoliation, and chemical vapor deposition. Along with BNNS, h-BN nanoribbon synthesis is also presented as it follows a similar approach to BNNS. As h-BN is the insulating isostructure to graphene, use of h-BN in some of the major applications such as coatings, dielectric, and some device applications are also discussed.

      PubDate: 2016-06-14T16:46:38Z
  • 2D Structures Beyond Graphene: The Brave New World of Layered Materials
           and How Computers Can Help Discover Them
    • Authors: Gould J.F.; Dobson
      Abstract: Publication date: Available online 1 June 2016
      Source:Semiconductors and Semimetals
      Author(s): T. Gould, S. Lebègue, T. Björkman, J.F. Dobson
      In this chapter we will survey the field of 2D materials beyond graphene to summarize the present state of the art in experimentally and theoretically studied layer structures. Some of the general reasons behind the unusual energetic properties of 2D systems will be discussed, and the accuracy of different ab initio techniques will by surveyed. We will also touch on the future of heterostructured materials and highlight how computers and theory, and especially the theory of van der Waals and related forces, will play a role in producing new, useful materials.

      PubDate: 2016-06-14T16:46:38Z
  • Series Page
    • Abstract: Publication date: 2016
      Source:Semiconductors and Semimetals, Volume 94

      PubDate: 2016-01-10T23:34:57Z
  • Contents of Volumes in this Series
    • Abstract: Publication date: 2016
      Source:Semiconductors and Semimetals, Volume 94

      PubDate: 2016-01-10T23:34:57Z
  • Nanowire-Based Visible Light Emitters, Present Status and Outlook
    • Authors: Monemar Jonas; Ohlsson Nathan Gardner Lars Samuelson
      Abstract: Publication date: Available online 29 December 2015
      Source:Semiconductors and Semimetals
      Author(s): Bo Monemar, B. Jonas Ohlsson, Nathan F. Gardner, Lars Samuelson
      So far, the semiconductor nanowire research area has mainly delivered results on growth procedures and related material properties. As the development lately has been successful in producing novel nanowire-based structures for optical or electronic applications, the time is ripe to review the device work that has been done and in some cases has produced devices ready for the market. In this chapter, we shall review the specific area of nanowire-based LEDs (NW-LEDs) for visible light, including the application area of “solid state lighting” (SSL). A brief review of the progress in the area of visible light LEDs over the last half century is presented, this also mentions some of the progress made in the planar technology so far. The most successful way of producing white light is still based on the use of phosphors, just like in the present compact fluorescence lamps (CFLs). The reason for this is the high efficiency (external quantum efficiency>80%) possible at low currents in the violet planar InGaN-based LEDs used to excite the phosphors. These LEDs are presently mainly produced on foreign substrates, leading to a high dislocation density (DD) and a sizeable droop at high injection currents (25–40%). This droop and the down conversion energy loss in the phosphors (20–25%) has motivated the interest for a phosphor-less white light source based on direct mixing of light of different wavelength (such as red, green, and blue; RGB). To be competitive, this solution must be based on highly efficient LEDs for all RGB (red, green, and blue) colors. Since NW-LED structures can be produced basically free of structural defects (even if grown on a foreign substrate), the idea of using the RGB mixing concept for the production of white light sources with an ultimately higher efficiency than for the phosphor-based lamps is a major technical target for a second generation of light sources in the SSL field. Basic concepts behind the design and optical properties of NW-LED structures are discussed in this chapter, with emphasis on the present developments of III-nitride-based structures. The growth procedure relevant for such NW-LED structures is reported in some detail, specifically the core–shell configuration readily produced with metalorganic vapor phase epitaxy (MOVPE). The first generation processing technology for NW-LED structures is briefly described; this is naturally quite different from the established routines for planar LED chips. Experimental data for nitride-based NW-LEDs for blue, green, and even longer wavelengths are given in terms of radiative efficiencies, light outcoupling, droop, and long-term reliability. The experience so far is that for these NW-based emitters, efficiencies can be obtained that are close to those for the corresponding planar LEDs. There are still problems with the reproducibility of the radiative output, as well as a significant droop that would not be expected for m-plane emitters. More work is needed to pinpoint the cause of these problems. Finally, we briefly discuss various applications (also other than white lamps) where the NW-LEDs may have a specific advantage.

      PubDate: 2016-01-01T02:09:44Z
  • Efficient Multiscale Lattice Simulations of Strained and Disordered
    • Authors: N. Leconte; A. Ferreira; J. Jung
      Pages: 35 - 99
      Abstract: Publication date: Available online 1 June 2016
      Source:Semiconductors and Semimetals
      Author(s): N. Leconte, A. Ferreira, J. Jung
      Graphene's electronic and structural properties are often studied using continuum models, such as the Dirac Hamiltonian for its electronic properties or the Born von Karman plate theory for its structural or elastic properties. While long-wavelength continuum approaches generally provide a convenient and accurate theoretical framework to understand graphene, in many scenarios of interest, it is desirable to resort to lattice models accounting for short-range bond transformation effects, eg, induced by defects or chemical substitutions. Here, we present an efficient multiscale methodology that combines information from first-principles calculations and long-range continuum strain fields to inform accurate real-space tight-binding Hamiltonians capturing the effect of both short-range disorder and long-range strains. Efficient numerical algorithms based on Lanczos recursion and kernel polynomial methods are used to extract physical observables of interest in realistic system sizes containing in excess of tens of millions of atoms.

      PubDate: 2016-06-14T16:46:38Z
      DOI: 10.1016/bs.semsem.2016.04.002
  • Elemental Group IV Two-Dimensional Materials Beyond Graphene
    • Authors: M.E. Dávila; L.C. Lew Yan Voon; J. Zhao; G. Le Lay
      Pages: 149 - 188
      Abstract: Publication date: Available online 7 June 2016
      Source:Semiconductors and Semimetals
      Author(s): M.E. Dávila, L.C. Lew Yan Voon, J. Zhao, G. Le Lay
      In the last years, “the growth and properties of silicene” has become one of the hottest research front in Physics and the first in Condensed Matter Physics. In this chapter, we describe the discovery of silicene, its outstanding properties, its amazingly fast development, and the birth of its column IV brothers, germanene and stanene. We further present the fascinating perspectives offered in fundamental research and in applications by these novel elemental two-dimensional materials, which have been created by scientists in the laboratory, since, at variance with graphene, which descents from graphite, they have no layered parent crystal in nature.

      PubDate: 2016-06-14T16:46:38Z
      DOI: 10.1016/bs.semsem.2016.04.003
  • Synthesis, Properties, and Stacking of Two-Dimensional Transition Metal
    • Authors: K. Zhang; Y.-C. Lin; J.A. Robinson
      Pages: 189 - 219
      Abstract: Publication date: Available online 14 June 2016
      Source:Semiconductors and Semimetals
      Author(s): K. Zhang, Y.-C. Lin, J.A. Robinson
      In 2004, the study about monolayer carbon film, namely graphene, opens a new era of materials science research: Two-dimensional (2D) materials. It attracts the tremendous interests in the unique properties when materials’ dimension is reduced (Novoselov et al., 2004). In the recent 10 years, there has been rapidly increasing study focusing on 2D materials beyond graphene (Bhimanapati et al., 2015). A large family of 2D materials have gradually been revealed including conductors (graphene), semiconductors (transition metal dichalcogenides, TMDs), and insulators (hexagonal boron nitride (hBN)). In this family, TMDs fit the application on transistors and photosensors best due to its appropriate band gap (visible light range). Additionally, the band gap of TMDs can be tuned by alloying or stacking different TMDs (Lin et al., 2014a), defect engineering (Chow et al., 2015), and chemical doping. To realize the application, the preparation of TMDs is the first question to the scientific society. In the first part of this chapter, we review widely used synthesis methods of TMDs (mainly focusing on MoS2) and compare the advantages and disadvantages of different synthesis methods. The properties of TMDs synthesized by different methods are correlated to the synthesis techniques. Stacking 2D TMDs layers with other 2D crystals to create “van der Waals” (vdW) heterostructures has been a common technique to explore new properties out of 2D material-based systems. In the second part of this chapter, the very first examples using graphene and hBN that initiated this field of research would be introduced to help readers build a general knowledge on vdW heterostructures. Subsequently, other vdW heterostructures that utilizes TMDs as a component to create novel optoelectronics would also be briefed. In order to place vdW heterostructures on a practical platform that can synthesize and produce their electronics, many synthetic techniques have been developed to grow different 2D materials together. Some cases of synthetic vdW heterostructures that have been developed are presented at the end of Section 7.

      PubDate: 2016-06-18T18:54:18Z
      DOI: 10.1016/bs.semsem.2016.04.005
  • Advances in 2D Materials for Electronic Devices
    • Authors: B.M. Nichols; A.L. Mazzoni; M.L. Chin; P.B. Shah; S. Najmaei; R.A. Burke; M. Dubey
      Pages: 221 - 277
      Abstract: Publication date: Available online 31 May 2016
      Source:Semiconductors and Semimetals
      Author(s): B.M. Nichols, A.L. Mazzoni, M.L. Chin, P.B. Shah, S. Najmaei, R.A. Burke, M. Dubey
      The emergence of graphene as a viable active material for electronic applications has sparked an explosion of research studying the fundamental electrical performance of it and other two-dimensional (2D) materials. As transistors continue to shrink in size, layered 2D materials, such as graphene, phosphorene, and the transition metal dichalcogenides, can fulfill the role as the active channel without the limitations primarily found with silicon. This discussion strives to provide an overview of the emerging research into the electrical behavior of 2D materials from simple field-effect transistors to state-of-the-art integrated circuits and devices. Experimental testing considerations and circuit design issues involving 2D material-based devices are also examined. The potential to harness 2D materials for digital logic circuits, radio frequency applications, and other novice device concepts is explored.

      PubDate: 2016-06-14T16:46:38Z
      DOI: 10.1016/bs.semsem.2016.03.001
  • Black Phosphorus-Based Nanodevices
    • Authors: J.O. Island; A. Castellanos-Gomez
      Pages: 279 - 303
      Abstract: Publication date: Available online 25 April 2016
      Source:Semiconductors and Semimetals
      Author(s): J.O. Island, A. Castellanos-Gomez
      Along this chapter, we summarize the recent advances in research on black phosphorus as an introduction to this young yet rapidly growing field. We provide a thorough selection of the relevant references on this topic and thus believe that this chapter is a suitable starting point for young researchers in the field of black phosphorus. The main characteristics of black phosphorus such as a strong thickness-dependent band structure or marked in-plane anisotropy are discussed, and the recent works applying black phosphorus for electronic, optics, and mechanical nanodevices are summarized.

      PubDate: 2016-04-28T19:38:59Z
      DOI: 10.1016/bs.semsem.2016.03.002
  • Semiconductor Nanowires for Energy Harvesting
    • Authors: Yanhao Xudong; Wang
      Abstract: Publication date: Available online 29 November 2015
      Source:Semiconductors and Semimetals
      Author(s): Yanhao Yu, Xudong Wang
      Semiconductor nanowires (NWs) have been extensively studied for over two decades. Due to their one-dimensional morphology-related novel electronic, electrochemical, thermal, and mechanical properties, semiconductor NWs hold great promises in energy harvesting from light irradiation, temperature gradient, and mechanical deformation. This chapter provides a comprehensive overview of the most recent major advances of semiconductor NWs in the field of energy harvesting. NW-based photovoltaics are first reviewed with an emphasis of solar cells assembled from p–n junction, organic dye, polymer, quantum dots, and organometal perovskite. Developments of NW-based photoelectrochemical reactions are then discussed and compared from the groups of pristine, doped NWs, and NW heterostructures. NW-based thermoelectric and piezoelectric devices are reviewed and their unique advantages in thermal and mechanical energy harvesting are discussed. This chapter concludes with a brief perspective on future research directions and remaining challenges that would need to be overcome for utilizing semiconductor NWs in practical energy-harvesting devices.

      PubDate: 2015-12-04T06:15:43Z
  • Silicon Micro/Nanowire Solar Cells
    • Authors: Chito Kendrick; Joan Redwing
      Abstract: Publication date: Available online 29 November 2015
      Source:Semiconductors and Semimetals
      Author(s): Chito E. Kendrick, Joan M. Redwing
      Photovoltaic (PV) devices based on arrays of silicon wires with diameters in the nanometer to micron range have sparked considerable interest due to their attractive light trapping characteristics and the prospects to enhance carrier collection in radial junction structures. This chapter reviews fabrication techniques, design and testing considerations, and the PV performance of silicon wire devices. Common bottom-up and top-down wire fabrication methods are initially reviewed including vapor–liquid–solid growth, metal-assisted chemical etching, and deep reactive ion etching. Design considerations for wire array solar cells are discussed such as the impact of wire array geometry on light absorption and the effects of wire diameter and doping on PV performance. Device results for three common wire junction geometries are then reviewed including radial and axial junction wire structures and planar junctions with nanowire surface texturing. Methods to form radial junctions in silicon wires are compared such as the use of an electrolyte, thermal diffusion of dopants, and wire-coating techniques based on chemical vapor deposition. Applications for nanowire texturing of silicon monocrystalline and multicrystalline cells are described. The advances in device design and processing have resulted in continual improvements in the PV performance of silicon wire array devices to the point where efficiencies ranging from ~10% for radial junction cells up to as high as 22.1% for nanowire-textured devices have been reported.

      PubDate: 2015-11-29T06:15:53Z
  • Optical Properties of Semiconductor Nanowires: Insights into Band
           Structure and Carrier Dynamics
    • Authors: Howard Jackson; Leigh Smith
      Abstract: Publication date: Available online 29 November 2015
      Source:Semiconductors and Semimetals
      Author(s): Howard E. Jackson, Leigh M. Smith
      This chapter describes how optical experiments on single semiconductor nanowires and nanowire heterostructures have illuminated both new physics and influenced the development of new growth methods that have resulted in nanowires of high quality. New physics here means the understanding of fundamental properties including band structures, the roles of symmetry and of strain in core/shell structures, the dynamics of excited electron–hole plasmas, and the exploration of more complex nanowire heterostructures like quantum well tubes. We will concentrate in this chapter mainly on the III–V materials such as wurtzite and zincblende InP, GaAs and GaAs/AlGaAs core/shell, and core/multishell heterostructures, where incredible improvements in materials quality have enabled the development of many new applications in recent years, from high efficiency solar cells, single nanowire lasers at room temperature, and single photon emitters, to a variety of chemical and biological sensors. We end the chapter with a brief mention of very recent experiments on some very new nanowire materials like InGaAs and GaAsSb whose bandgaps move distinctly into infrared wavelength regime.

      PubDate: 2015-11-29T06:15:53Z
  • Series Page
    • Abstract: Publication date: 2015
      Source:Semiconductors and Semimetals, Volume 93

      PubDate: 2015-11-29T06:15:53Z
  • Compound Semiconductor Nanowire Photodetectors
    • Authors: Xing Dai; Maria Tchernycheva Cesare Soci
      Abstract: Publication date: Available online 2 November 2015
      Source:Semiconductors and Semimetals
      Author(s): Xing Dai, Maria Tchernycheva, Cesare Soci
      Photodetectors based on quasi one-dimensional nanostructures—nanowires—formed of different materials have attracted large attention. The interest in these devices is motivated by the fascinating properties of nanowires, which offer new ways to improve the detector performance as well as to add different functionalities: the high surface-to-volume ratio of nanowires is key to the enhancement of sensitivity of nanowire photoconductors, while radial and axial junctions enable heterostructured nanowire photodetectors. Due to their small size, nanowires allow for ultimate detector miniaturization and facilitate their integration into compact photonic circuits. In this chapter, we review some general nanowire photodetector concepts and illustrate them by examples of recent experimental demonstrations using compound semiconductor materials.

      PubDate: 2015-11-02T22:38:11Z
  • Nanowire Tunneling Field-Effect Transistors
    • Authors: Joachim Knoch
      Abstract: Publication date: Available online 2 November 2015
      Source:Semiconductors and Semimetals
      Author(s): Joachim Knoch
      Field-effect transistors based on band-to-band tunneling (TFETs) have recently attracted a great deal of interest. The strong interest stems from the fact that TFETs potentially allow the realization of transistors with superior switching behavior compared to conventional metal-oxide semiconductor FETs and hence allow reducing the operational voltage as well as the off-state leakage current. As a result, integrated circuits based on TFETs potentially exhibit a substantially reduced dynamic and static power consumption and are therefore particularly well suited for low-power, mobile applications. However, although tremendous progress has been made recently, experimental realizations so far still lack a satisfying performance. While a number of apparent performance boosters have been identified in recent studies, their impact on the performance of TFETs becomes rather intricate and involved when spatial dimensions are reduced to the nanoscale such as in nanowire TFETs. The aim of this chapter is to study the various dependences isolated from each other in order to illuminate the interdependencies, impact, and effectiveness of different TFET performance boosters.

      PubDate: 2015-11-02T22:38:11Z
  • Semiconductor Nanowire Optoelectronic Devices
    • Authors: Sudha Mokkapati; Dhruv Saxena Hark Hoe Tan Chennupati Jagadish
      Abstract: Publication date: Available online 1 October 2015
      Source:Semiconductors and Semimetals
      Author(s): Sudha Mokkapati, Dhruv Saxena, Hark Hoe Tan, Chennupati Jagadish
      Semiconductor nanowires act as waveguides despite very small cross-section dimensions because of high refractive indices. The waveguiding properties of nanowires alter the way the semiconductor material interacts with light. We elaborate on the waveguiding properties of nanowires and the effect of these properties on the spontaneous emission characteristics of nanowires. The effect of waveguiding properties of nanowires on optoelectronic devices like nanowire solar cells and lasers is also discussed.

      PubDate: 2015-10-01T11:42:03Z
  • Quantum Dots in Nanowires
    • Authors: Luca Francaviglia; Yannik Fontana Anna Fontcuberta Morral
      Abstract: Publication date: Available online 1 October 2015
      Source:Semiconductors and Semimetals
      Author(s): Luca Francaviglia, Yannik Fontana, Anna Fontcuberta i Morral
      Nanoscale filamentary crystals known as nanowires (NWs) are the ideal platform for the controlled fabrication of quantum dots (QDs). Thanks to the exquisite control in NW growth mechanisms, nanoscale insertions of foreign materials in NWs forming nanowire-based QDs, NWQDs, are nowadays possible. NW shape and axial dimensions also allow addressing them optically and electronically. Photonic design of the NW shape also guarantees maximized extraction of the QD emission. Overall, this is a vibrating area of research which should soon translate its knowledge into technology.

      PubDate: 2015-10-01T11:42:03Z
  • Mechanical Behaviors of Semiconductor Nanowires
    • Authors: Yujie Chen; Xiaozhou Liao
      Abstract: Publication date: Available online 26 September 2015
      Source:Semiconductors and Semimetals
      Author(s): Yujie Chen, Xiaozhou Liao
      Semiconductor nanowires (NWs) have demonstrated many interesting physical properties that are not seen in bulk semiconductors due to the unique quantum mechanics effect in one-dimensional structures. The mechanical properties of semiconductor NWs, which are expected to be significantly different from those of their bulk materials because of the small NW dimensions, are a crucial factor in designing and manufacturing NW-based devices with predictable and reproducible operation. Because of their small dimensions, mechanical property testing of NWs is not an easy task and errors can be easily introduced in the measured mechanical data. Here, we review the techniques that have been developed to quantify the mechanical properties and to understand the deformation mechanisms of NWs, including bending, resonance, uniaxial loading, and nanoindentation. We also provide a general review of the mechanical properties and deformation behaviors of semiconductor NWs and discuss possible sources responsible for the discrepancy of measured mechanical properties.

      PubDate: 2015-10-01T11:42:03Z
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