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Sample records for gasb-based iii-v alloys

  1. III-V alloy heterostructure high speed avalanche photodiodes

    NASA Technical Reports Server (NTRS)

    Law, H. D.; Nakano, K.; Tomasetta, L. R.

    1979-01-01

    Heterostructure avalanche photodiodes have been successfully fabricated in several III-V alloy systems: GaAlAs/GaAs, GaAlSb/GaAlSb, and InGaAsP/InP. These diodes cover optical wavelengths from 0.4 to 1.8 micron. Early stages of development show very encouraging results. High speed response of less than 35 ps and high quantum efficiency more than 95 percent have been obtained. The dark currents and the excess avalanche noise are also dicussed. A direct comparison of GaAlSb, GaAlAsSb, and In GaAsP avalanche photodiodes is given.

  2. Effective band structure of random III-V alloys

    NASA Astrophysics Data System (ADS)

    Popescu, Voicu; Zunger, Alex

    2010-03-01

    Random substitutional alloys have no long range order (LRO) or translational symmetry so rigorously speaking they have no E(k) band structure or manifestations thereof. Yet, many experiments on alloys are interpreted using the language of band theory, e.g. inferring Van Hove singularities, band dispersion and effective masses. Many standard alloy theories (VCA- or CPA-based) have the LRO imposed on the alloy Hamiltonian, assuming only on-site disorder, so they can not be used to judge the extent of LRO that really exists. We adopt the opposite way, by using large (thousand atom) randomly generated supercells in which chemically identical alloy atoms are allowed to have different local environments (a polymorphous representation). This then drives site-dependent atomic relaxation as well as potential fluctuations. The eigenstates from such supercells are then mapped onto the Brillouin zone (BZ) of the primitive cell, producing effective band dispersion. Results for (In,Ga)X show band-like behaviour only near the centre and faces of the BZ but rapidly lose such characteristics away from γ or for higher bands. We further analyse the effects of stoichiometry variation, internal relaxation, and short-range order on the alloy band structure.

  3. Method for preparing homogeneous single crystal ternary III-V alloys

    DOEpatents

    Ciszek, Theodore F.

    1991-01-01

    A method for producing homogeneous, single-crystal III-V ternary alloys of high crystal perfection using a floating crucible system in which the outer crucible holds a ternary alloy of the composition desired to be produced in the crystal and an inner floating crucible having a narrow, melt-passing channel in its bottom wall holds a small quantity of melt of a pseudo-binary liquidus composition that would freeze into the desired crystal composition. The alloy of the floating crucilbe is maintained at a predetermined lower temperature than the alloy of the outer crucible, and a single crystal of the desired homogeneous alloy is pulled out of the floating crucible melt, as melt from the outer crucible flows into a bottom channel of the floating crucible at a rate that corresponds to the rate of growth of the crystal.

  4. An extended Hückel study of the electronic properties of III-V compounds and their alloys

    NASA Astrophysics Data System (ADS)

    Ribeiro, Ingrid A.; Ribeiro, Fabio J.; Martins, A. S.

    2014-05-01

    In this work, we performed tight binding calculations of the electronic structure of III-V semiconductors compounds and their alloys based on the Extended Hückel Theory (EHT). In particular, this paper is focused on the dependency between band gap and the applied pressure and also the alloy composition.

  5. Theory of band gap bowing of disordered substitutional II-VI and III-V semiconductor alloys

    NASA Astrophysics Data System (ADS)

    Mourad, D.; Czycholl, G.

    2012-05-01

    For a wide class of technologically relevant compound III-V and II-VI semiconductor materials AC and BC mixed crystals (alloys) of the type A x B1- x C can be realized. As the electronic properties like the bulk band gap vary continuously with x, any band gap in between that of the pure AC and BC systems can be obtained by choosing the appropriate concentration x, granted that the respective ratio is miscible and thermodynamically stable. In most cases the band gap does not vary linearly with x, but a pronounced bowing behavior as a function of the concentration is observed. In this paper we show that the electronic properties of such A x B1- x C semiconductors and, in particular, the band gap bowing can well be described and understood starting from empirical tight-binding models for the pure AC and BC systems. The electronic properties of the A x B1- x C system can be described by choosing the tight-binding parameters of the AC or BC system with probabilities x and 1 - x, respectively. We demonstrate this by exact diagonalization of finite but large supercells and by means of calculations within the established coherent potential approximation (CPA) We apply this treatment to the II-VI system Cd x Zn1- x Se, to the III-V system In x Ga1- x As and to the III-nitride system Ga x Al1- x N.

  6. Annealing group III-V compound doped silicon-germanium alloy for improved thermo-electric conversion efficiency

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W. (Inventor); Wood, Charles (Inventor); Draper, Susan L. (Inventor)

    1989-01-01

    The thermoelectric conversion efficiency of a GaP doped SiGe alloy is improved about 30 percent by annealing the alloy at a temperature above the melting point of the alloy, preferably stepwise from 1200 C to 1275 C in air to form large grains having a size over 50 microns and to form a GeGaP rich phase and a silicon rich phase containing SiP and SiO2 particles.

  7. Estimation of Bi induced changes in the direct E0 band gap of III-V-Bi alloys and comparison with experimental data

    NASA Astrophysics Data System (ADS)

    Samajdar, D. P.; Dhar, S.

    2016-03-01

    Quantum dielectric Theory (QDT) is used to explain the band gap bowing effect observed in III-V-Bismides such as InSb1-xBix, InAs1-xBix, InP1-xBix, GaSb1-xBix, GaAs1-xBix and GaP1-xBix. The dependence of the direct E0 band gap for these alloys on Bi mole fraction is calculated using QDT which requires the evaluation of the bowing parameter c. The bowing parameter gives the deviation of the direct E0 band gap from the linear relationship of E0 with Bi mole fraction. The band gap reduction values obtained using QDT are compared with those calculated using Virtual Crystal approximation (VCA) and Valence Band Anticrossing (VBAC) model as well as with the reported experimental data and the results of the comparison shows excellent agreement.

  8. MBE growth and spin injection measurements of ferromagnetic alloy nickel-manganese-indium on III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Xie, Junqing

    In this thesis, ferromagnetic metal/III-V semiconductor heterostructures were investigated for the development of spintronic devices. Particularly, three major research projects were carried out. First, spin injection from Fe into GaAs was studied. Second, the InAs-based resonant tunnel diode (RTD) was developed for spin detection. Third, epitaxial growth of single-crystal ferromagnetic Ni2MnIn thin films as a potential spin contact on InAs was demonstrated by molecular beam epitaxy (MBE). Spin injection from Fe into GaAs was studied by using the Fe/(Al,Ga)As Schottky contact as the spin injector and the GaAs/(Al,Ga)As quantum well as the spin detector. Our results show that high delta-layer doping levels are detrimental to the electroluminescence polarization (ELP) signals while a uniformly doped n+-layer can improve the spin injection efficiency. An ELP signal as high as 20% was obtained for a spin light emitting diode sample with a uniformly doped n+-layer with a doping level of 5 x 1018/cm3. The InAs/AlSb/GaSb/AlSb/GaSb/InAs RTD structure was developed as a potential spin detector. MBE growth procedures for InAs and AlxGa1-x Sb were established. InAs/AlSb/GaSb/AlSb/InAs RTD structures were grown and fabricated. The I-V characteristics of the devices show a peak-to-valley ratio of 3 and 10 at room temperature and 14 K, respectively. As a promising spin contact on InAs, the growth of ferromagnetic Ni 2MnIn thin films on InAs (001) was demonstrated by MBE. At a growth temperature of 120C, a transmission electron microscopy study confirms the epitaxial growth of Ni2MnIn films in the B2 structure on InAs (001). The epitaxial relationship was determined to be Ni2MnIn(001)<100> || InAs(001)<100>. The lower Curie temperature of the films (170 K), compared to that of bulk Ni2MnIn, is believed to result from the growth of Ni2MnIn in the B2 structure rather than the L21 structure. Curie temperatures of the Ni2MnIn thin films can be increased through annealing. For a sample grown at 120C and annealed at 200C, a Curie temperature as high as 330 K was obtained. The high Curie temperature is correlated to the Ni2MnIn in the partially L21-ordered structure.

  9. Dry etching of III-V nitrides

    SciTech Connect

    Pearton, S.J.; Shul, R.J.; McLane, G.F.; Constantine, C.

    1995-12-01

    The chemical inertness and high bond strengths of the III-V nitrides lead to slower plasma etching rates than for more conventional III-V semiconductors under the same conditions. High ion density conditions (>3{times}l0{sup 9}cm{sup {minus}3}) such as those obtained in ECR or magnetron reactors produce etch rates up to an order of magnitude higher than for RIE, where the ion densities are in the 10{sup 9}cm{sup {minus}3} range. We have developed smooth anisotropic dry etches for GaN, InN, AlN and their alloys based on Cl{sub 2}/CH{sub 4}/H{sub 2}/Ar, BCl{sub 3}/Ar, Cl{sub 2}/H{sub 2}, Cl{sub 2}/SF{sub 6}, HBr/H{sub 2} and HI/H{sub 2} plasma chemistries achieving etch rates up to {approximately}4,000{angstrom}/min at moderate dc bias voltages ({le}-150V). Ion-induced damage in the nitrides appears to be less apparent than in other III-V`s. One of the key remaining issues is the achievement of high selectivities for removal of one layer from another.

  10. Progress and Continuing Challenges in GaSb-based III-V Alloys and Heterostructures Grown by Organometallic Vapor Phase Epitaxy

    SciTech Connect

    CA Wang

    2004-05-06

    This paper discusses progress in the preparation of mid-IR GaSb-based III-V materials grown by organometallic vapor phase epitaxy (OMVPE). The growth of these materials is complex, and fundamental and practical issues associated with their growth are outlined. Approaches that have been explored to further improve the properties and performance are briefly reviewed. Recent materials and device results on GaInAsSb bulk layers and GaInAsSb/AlGaAsSb heterostructures, grown lattice matched to GaSb, are presented. State-of-the-art GaInAsSb materials and thermophotovoltaic devices have been achieved. This progress establishes the high potential of OMVPE for mid-IR GaSb-based devices.

  11. Strain engineering of magnetic anisotropy: The epitaxial growth of cobalt-manganese-gallium Heusler alloy films on III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Carr, David Michael

    This research is the first step towards manipulating thin film magnetic anisotropy through control of uniform epitaxial strain. Pseudomorphic Co 2MnGa films with thicknesses of 300 A have been grown on several III-V semiconductors to generate coherently-strained epitaxial films. Growth of Co2MnGa films at 200°C both directly on GaAs substrates and on thermodynamically stable Sc0.3Er0.7As interlayers resulted in similar physical and magnetic properties. The epitaxial strain generated an induced perpendicular anisotropy and magnetic stripe domains. This resulted in a reduced in-plane remnant magnetization, high coercivity, and a relatively low saturation field for the out-of-plane magnetization. For higher temperature growths, the interlayer was required to minimize interfacial reactions and maintain the magnetic properties of the films. When the growth temperature on the Sc0.3Er0.7As interlayers was increased from 0 to 400°C, the subsequent films had improved L21 atomic ordering, decreased out-of-plane lattice parameters, and enhanced strain-induced perpendicular anisotropy. Dramatic variations in the magnetic anisotropy were observed for films grown on different III-V semiconductors due to controlled strain-induced perpendicular anisotropy. For Co2MnGa films grown under tension on InP, the magnetization barely saturated out-of-plane with a field of 1.75 Tesla. These films displayed clear in-plane anisotropy and low coercivity switching. For films grown under compression on GaAs, the magnetization easily saturated out-of-plane with a field of a few thousand Oe. These films displayed no in-plane anisotropy in the hysteresis loops and had large coercivities. For comparison, bulk-like unstrained Co2MnGa films were grown on relaxed ErAs interlayers on InAs. These films displayed properties intermediate between films grown on GaAs and InP. Finally, growth of films on GaP resulted in partial relaxation, thereby reducing the induced perpendicular anisotropy and verifying the need to grow uniformly strained films. A magnetic coherent rotation model was derived that provided a qualitative description for the anisotropy of films grown on InP and relaxed ErAs interlayers. However, it did not capture the behavior of films grown on GaAs due to the magnetic stripe domains. This research has successfully demonstrated the ability to manipulate the thin film magnetic anisotropy of epitaxial Co2MnGa films through uniform epitaxial strain.

  12. Antimony Based III-V Thermophotovoltaic Devices

    SciTech Connect

    CA Wang

    2004-06-09

    Antimony-based III-V thermophotovoltaic (TPV) cells are attractive converters for systems with low radiator temperature around 1100 to 1700 K, since these cells potentially can be spectrally matched to the thermal source. Cells under development include GaSb and the lattice-matched GaInAsSb/GaSb and InPAsSb/InAs quaternary systems. GaSb cell technology is the most mature, owing in part to the relative ease in preparation of the binary alloy compared to quaternary GaInAsSb and InPAsSb alloys. Device performance of 0.7-eV GaSb cells exceeds 90% of the practical limit. GaInAsSb TPV cells have been the primary focus of recent research, and cells with energy gap E{sub g} ranging from {approx}0.6 to 0.49 eV have been demonstrated. Quantum efficiency and fill factor approach theoretical limits. Open-circuit voltage factor is as high as 87% of the practical limit for the higher-E{sub g} cells, but degrades to below 80% with decreasing E{sub g} of the alloy, which might be due to Auger recombination. InPAsSb cells are the least studied, and a cell with E{sub g} = 0.45-eV has extended spectral response out to 4.3 {micro}m. This paper briefly reviews the main contributions that have been made for antimonide-based TPV cells, and suggests additional studies for further performance enhancements.

  13. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, Theodore D.; Misra, Mira

    1997-01-01

    A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

  14. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, T.D.; Misra, M.

    1997-10-14

    A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector. 24 figs.

  15. III-V arsenide-nitride semiconductor

    NASA Technical Reports Server (NTRS)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

    2000-01-01

    III-V arsenide-nitride semiconductor are disclosed. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V materials varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V material can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  16. Hybrid III-V/silicon lasers

    NASA Astrophysics Data System (ADS)

    Kaspar, P.; Jany, C.; Le Liepvre, A.; Accard, A.; Lamponi, M.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Shen, A.; Charbonnier, P.; Mallecot, F.; Duan, G.-H.; Gentner, J.-.; Fedeli, J.-M.; Olivier, S.; Descos, A.; Ben Bakir, B.; Messaoudene, S.; Bordel, D.; Malhouitre, S.; Kopp, C.; Menezo, S.

    2014-05-01

    The lack of potent integrated light emitters is one of the bottlenecks that have so far hindered the silicon photonics platform from revolutionizing the communication market. Photonic circuits with integrated light sources have the potential to address a wide range of applications from short-distance data communication to long-haul optical transmission. Notably, the integration of lasers would allow saving large assembly costs and reduce the footprint of optoelectronic products by combining photonic and microelectronic functionalities on a single chip. Since silicon and germanium-based sources are still in their infancy, hybrid approaches using III-V semiconductor materials are currently pursued by several research laboratories in academia as well as in industry. In this paper we review recent developments of hybrid III-V/silicon lasers and discuss the advantages and drawbacks of several integration schemes. The integration approach followed in our laboratory makes use of wafer-bonded III-V material on structured silicon-on-insulator substrates and is based on adiabatic mode transfers between silicon and III-V waveguides. We will highlight some of the most interesting results from devices such as wavelength-tunable lasers and AWG lasers. The good performance demonstrates that an efficient mode transfer can be achieved between III-V and silicon waveguides and encourages further research efforts in this direction.

  17. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, Theodore D.

    1998-01-01

    A bandpass photodetector using a III-V nitride and having predetermined electrical properties. The bandpass photodetector detects electromagnetic radiation between a lower transition wavelength and an upper transition wavelength. That detector comprises two low pass photodetectors. The response of the two low pass photodetectors is subtracted to yield a response signal.

  18. Photodetectors using III-V nitrides

    DOEpatents

    Moustakas, T.D.

    1998-12-08

    A bandpass photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The bandpass photodetector detects electromagnetic radiation between a lower transition wavelength and an upper transition wavelength. That detector comprises two low pass photodetectors. The response of the two low pass photodetectors is subtracted to yield a response signal. 24 figs.

  19. Preparation of III-V semiconductor nanocrystals

    DOEpatents

    Alivisatos, A. Paul; Olshavsky, Michael A.

    1996-01-01

    Nanometer-scale crystals of III-V semiconductors are disclosed, They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline.

  20. Preparation of III-V semiconductor nanocrystals

    DOEpatents

    Alivisatos, A.P.; Olshavsky, M.A.

    1996-04-09

    Nanometer-scale crystals of III-V semiconductors are disclosed. They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline. 4 figs.

  1. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    DOEpatents

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

    2015-01-13

    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  2. Structural and thermochemical Aspects of (III-V)IV3 Material Assembly from First Principles

    NASA Astrophysics Data System (ADS)

    Chizmeshya, Andrew; Kouvetakis, John

    2014-03-01

    Alloys with (III-V)-(IV) compositions, including Si3(AlP), Si5-2y(AlP)y, Si3Al(As1-xNx), Si5-2yAl(P1-xNx)y and Ge5-2y(InP)y and have recently been synthesized as mono-crystalline films on Si substrates, using a synthesis route specifically designed to avoid phase separation between the III-V and IV constituents. Molecular ``building blocks'' containing group-V-centered III-V-IV3 cores, formed via interactions of group-III atoms and reactive silyly/germyl hydride precursors of desired composition (e.g, P(SiH3)3 , P(GeH3)3 , etc), assemble to form stable, covalent, diamond-like materials with the inherent tetrahedral symmetry and composition of the III-V-IV3 units. The resulting systems may provide access to a broad range of new semiconductor systems with extended optoelectronic properties, provided that the required molecular sources are available, the thermodynamic processes are viable, and the resulting alloy composition can be tuned to lattice-match the growth substrate. Molecular/solid-state simulations are used to identify promising synthetic pathways and guide the epitaxial creation of new (III-V)-(IV) materials. The thermodynamics of gas phase synthesis reactions, energetic stability of the alloys, and their epitaxial/chemical compatibility with the substrate are combined to form a global figure of merit. The latter corroborates the synthesis of known systems and predicts that formation of GaPSi3/Si(100), GaAsSi3/SiGe(100), AlPGe3/Ge(100) and InAsSi3/Ge(100) may also be favorable. Supported by NSF-DMR under SusChEM award #1309090.

  3. Antimony-Based III-V Thermophotovoltaic Materials and Devices

    NASA Astrophysics Data System (ADS)

    Wang, C. A.

    2004-11-01

    Antimony-based III-V thermophotovoltaic (TPV) cells are attractive converters for systems with low radiator temperature of around 1100 to 1700 K, since these cells can be spectrally matched to the thermal source. Cells under development include GaSb and lattice-matched GaInAsSb/GaSb and InPAsSb/InAs. GaSb cell technology is the most mature, owing in part to the relative ease in preparation of the binary alloy compared to the quaternary alloys. Cell performance of 0.7-eV GaSb devices is at ˜90% of the practical limit. GaInAsSb cells with energy gap Eg ranging from ˜0.6 to 0.49 eV have been demonstrated with quantum efficiency and fill factor approaching practical limits. InPAsSb cells are the least studied, and a 0.45-eV cell has spectral response out to 4.3 μm. This paper briefly reviews the main efforts in Sb-based TPV cells.

  4. III-V nanowires and nanowire optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Zhang, Yunyan; Wu, Jiang; Aagesen, Martin; Liu, Huiyun

    2015-11-01

    III-V nanowires (NWs) have been envisioned as nanoscale materials for next-generation technology with good functionality, superior performance, high integration ability and low cost, because of their special growth modes and unique 1D structure. In this review, we summarize the main challenges and important progress of the fabrication and applications of III-V NWs. We start with the III-V NW growth, that significantly influences the NW morphology and crystal quality. Attention is then given to the fabrication of some advanced III-V structures composed of axial and radial junctions. After that, we review the advantages, challenges, and major breakthroughs of using III-V NWs as solar energy harvesters and light emitters. Finally, we attempt to give a perspective look on the future development trends and the remaining challenges in the research field of III-V NWs.

  5. III-V nanowires for optoelectronics

    NASA Astrophysics Data System (ADS)

    Kim, Yong; Gao, Q.; Joyce, H. J.; Tan, H. H.; Jagadish, C.; Paladugu, M.; Zou, J.

    2006-09-01

    The optical and structural properties of binary and ternary III-V nanowires including GaAs, InP, In(Ga)As, Al(Ga)As, and GaAs(Sb) nanowires by metal-organic chemical vapour deposition are investigated. Au colloidal nanoparticles are employed to catalyze nanowire growth. Zinc blende or wurtzite crystal structures with some stacking faults are observed for these nanowires by high resolution transmission electron microscope. In addition, the properties of heterostructure nanowires including GaAs-AlGaAs core-shell nanowires, GaAs-InAs nanowires, and GaAs-GaSb nanowires are reported. Single nanowire luminescence properties from optically bright InP nanowires are reported. Interesting phenomena such as two-temperature procedure, nanowire height enhancement of isolated ternary InGaAs nanowires, kinking effect of InAs-GaAs heterostructure nanowires, and unusual growth property of GaAs-GaSb heterostructure nanowires are investigated. These nanowires will play an essential role in future optoelectronic devices.

  6. Progress in III-V materials technology

    NASA Astrophysics Data System (ADS)

    Grant, Ian R.

    2004-12-01

    Compound semiconductors, in the form of GaAs and InP have achieved major commercial significance in areas of application such as mobile communications, displays and telecoms and offer a versatility of function beyond the capabilities of Si. III-V compounds, and in particular GaAs, have since their early development been the subject of defence related interest. Support from this sector established the basic materials technologies and nurtured development up until their commercial breakthrough into consumer products. GaAs, for example, now provides essential components for mobile phones and CD / DVD players. An overview is presented of the crystal growth and processing methods used in the manufacture of these materials. Current state of the art characteristics on crystal form and quality are discussed, together with the evolution of single crystal growth techniques. Consideration is given to how these principal compounds together with the minor materials, InSb, GaSb and InAs are employed in diverse applications over a broad spectral range, together with information on markets and future perspectives.

  7. III-V High-Efficiency Multijunction Photovoltaics (Fact Sheet)

    SciTech Connect

    Not Available

    2011-06-01

    Capabilities fact sheet that includes scope, core competencies and capabilities, and contact/web information for III-V High-Efficiency Multijunction Photovoltaics at the National Center for Photovoltaics.

  8. Recent trends in III--V strained layer research

    SciTech Connect

    Osbourn, G.C.

    1986-11-01

    Current directions in III--V strained layer superlattice research are briefly reviewed. Areas of recent emphasis include the study of the tailorable light hole mass values, the development of new III--V strained layer materials for infrared detector applications, and work on modulation-doped field effect transistors employing strained quantum wells. Recent theoretical and experimental results as well as unresolved issues in these areas are discussed.

  9. Progress Towards III-V Photovoltaics on Flexible Substrates

    NASA Technical Reports Server (NTRS)

    McNatt, Jeremiah S.; Pal, AnnaMaria T.; Clark, Eric B.; Sayir, Ali; Raffaelle, Ryne P.; Bailey, Christopher G.; Hubbard, Seth M.; Maurer, William F.; Fritzemeier, Les

    2008-01-01

    Presented here is the recent progress of the NASA Glenn Research Center OMVPE group's efforts in the development of high efficiency thin-film polycrystalline III-V photovoltaics on optimum substrates. By using bulk polycrystalline germanium (Ge) films, devices of high efficiency and low mass will be developed and incorporated onto low-cost flexible substrates. Our progress towards the integration of high efficiency polycrystalline III-V devices and recrystallized Ge films on thin metal foils is discussed.

  10. III-V semiconductor solid solution single crystal growth

    NASA Technical Reports Server (NTRS)

    Gertner, E. R.

    1982-01-01

    The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

  11. III-V aresenide-nitride semiconductor materials and devices

    NASA Technical Reports Server (NTRS)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

    1997-01-01

    III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  12. FOREWORD: The physics of III-V nitrides The physics of III-V nitrides

    NASA Astrophysics Data System (ADS)

    Ridley, B. K.

    2009-04-01

    The evolution of semiconductor physics is driven by the increasing sophistication of the art of crystal growing and fabrication techniques. From Ge at the birth of the transistor, possibly the purest material ever grown, through Si, the work-horse of the crystal revolution, to the III-Vs, whose optical properties opened up a second front, namely, optoelectronics. Crystal growth with monolayer control gave us quantum wells, superlattices, quantum wires and quantum dots, along with the quantum Hall effect and quantized resistance. The potential for high-power devices triggered interest in the III-V nitrides with their large bandgaps. The nitrides mostly crystallize in the hexagonal form, and this has introduced the phenomenon of spontaneous polarization into mainstream semiconductor physics. Its effect manifests itself in huge electric fields in heterostructures like AlGaN/GaN which, in turn, causes the induction of substantial electron populations in the channel of a HFET without the need for doping. High-power microwave transistors have been successfully fabricated, even though there are features associated with spontaneous polarization that still needs clarifying. Another strange effect is the large electron population on the surface of InN. The lack of a suitable substrate for growing GaN has meant that the dislocation density is higher than we would wish, but that situation is expected to steadily improve. Given the current interest in the physics of nitrides, it is natural to come across a special issue devoted to this topic. The difficulty presented by the surface layer in InN in the attempt to measure transport properties is discussed in the paper by King et al. A property that can affect transport is the lifetime of optical phonons and its dependence on electron density. Measurements of phonon lifetime in InN are reported by Tsen and Ferry, and in GaN channels, via the measure of hot-electron fluctuations, by Matulionis. The dependence on electron density is thought to be associated with the coupling of plasma and phonon modes, and this is discussed by Dyson. The intrinsic cause of phonon decay is the anharmonic interaction involving three phonons, and this process is described for zinc blende BN and hexagonal AlN, GaN and InN by Srivastava. The principal electron scattering mechanism at room temperature is associated with the interaction with polar optical modes. At high fields, transfer to the upper conduction-band valleys can take place and this involves the deformation-potential interaction. Deformation potentials have been derived by Yamakawa et al for GaN, and they have been incorporated into a cellular Monte Carlo simulation to describe high-field transport. In high-power devices, thermal as well as electronic transport is important. The thermal conductivity of the substrate of devices is a vital factor, and the possible use of AlN ceramics is discussed by AlShaikhi and Srivastarva. A striking device based on a zinc blende superlattice is the quantum cascade laser. Exploiting intersubband transitions in the AlN/GaN superlattice for the high-speed detection of infrared light is described by Hofstetter et al, clearly a first step towards a nitride based quantum cascade laser. In bulk material the displacement of As by N that transforms GaAs to GaN produces a huge change in properties. Adding a small amount of N to GaAs might be expected to produce a gradual more-or-less linear shift towards the properties of GaN, but this turns out to be far from the case. The strange properties of dilute nitrides have intrigued many workers in recent years. Its curious bandstructure suggested that hot-electron transport could exhibit a negative differential resistance, and a report on this topic can be found in the article by Patane et al A comprehensive study of transport of electrons and holes in dilute nitride/GaAs quantum wells is reported by Sun et al. An unusual new device—a spin filter—is presaged by the work of Zhao et al on spin-dependent recombination, controllable by adjusting the N content. Answers to a number of problems presented by the physics of III-V nitrides are to be found in the articles composing this edition, but there are still many that need clarifying. That clarification will have to await the future work that will form the contents of a future special edition.

  13. Influence of Bi-related impurity states on the bandgap and spin-orbit splitting energy of dilute III-V-Bi alloys: InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix

    NASA Astrophysics Data System (ADS)

    Samajdar, D. P.; Dhar, S.

    2016-01-01

    Valence Band Anticrossing (VBAC) Model is used to calculate the changes in band structure of Bi containing alloys such as InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix due to the incorporation of dilute concentrations of bismuth. The coupling parameter CBi which gives the magnitude of interaction of Bi impurity states with the LH, HH and SO sub bands in VBAC depends on the increase in the HH/LH related energy level EHH/LH+, location of the Bi related impurity level EBi and valence band offset ΔEVBM between the endpoint compounds in the corresponding III-V-Bi. The reduction in band gap as well as the enhancement of the spin-orbit splitting energy is well explained using this model and the calculated results are compared with the results of Virtual Crystal Approximation (VCA) and Density Functional Theory (DFT) calculations, as well as with the available experimental data and are found to have good agreement. The incorporation of Bi mainly perturbs the valence band due to the interaction of the Bi impurity states with the HH, LH and SO bands. The lowering of the conduction band minimum (CBM) due to VCA is added with the upward movement of the HH/LH bands to get the total reduction in band gap for the bismides. The valence band shifts of 31.9, 32.5, 20.8 and 12.4 meV/at%Bi for InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix respectively constitute 65, 76, 59 and 31% of the total band gap reduction and the rest is the contribution of the conduction band shift. The spin-orbit splitting energy also shows significant increase with the maximum change in InPBi and the minimum in InSbBi. The same is true for Ga containing bismides if we make a comparison with the available values for GaAsBi and GaPBi with that of GaSbBi. It has also been observed that the increase in splitting energy is greater in case of the bismides such as InAsBi, InPBi and GaAsBi than the bismides such as InSbBi and GaSbBi with the parent substrates having higher values of splitting energy. This may be due to the proximity of the Bi related impurity level EBi with the SO bands of InAs, InP and GaAs.

  14. Cross-sectional scanning tunneling microscopy studies of novel III V semiconductor structures

    NASA Astrophysics Data System (ADS)

    Mikkelsen, A.; Lundgren, E.

    In recent years, nanostructure technology involving III-V semiconductors have made significant progress in areas such as optoelectronics and spintronics. A number of new materials and nanostructures have been invented, most of them being of a very dilute character or extremely small. Because of these properties, their structural characterization on an atomic scale is of profound importance. One important technique for the structural characterization of these structures is so-called cross-sectional Scanning Tunneling Microscopy (XSTM). The III-V semiconductor is cleaved perpendicular to the (1 0 0) growth direction exposing the (1 1 0) surface. This procedure enables a sharp STM tip to probe the atomic scale details of a wide variety of buried structures. Here, results from three different III-V structures with significant technological interest are presented. The first is the atomic scale structure of dilute ferromagnetic semiconductor superlattices consisting of alternate layers of GaAs and GaMnAs with different compositions. By unraveling the appearance of the Mn atoms in XSTM, we are able to investigate the diffusion of Mn atoms into the GaAs spacer layers between the GaMnAs layers. The second example concerns stacked quantum dots of InAs in InP. XSTM from stacks of 2, 5 and 10 quantum dots are presented. A significant number of defects will be shown as well as information on the amount of alloying between the InAs quantum dots and the surrounding InP layers. The last example concerns free standing objects such as nanowires. A new method is presented which enables us to cleave nanowires and consequently observe the individual atoms inside the wire. Our XSTM images provide detailed information on the growth of the wires as well as on the formation of twins inside the wires.

  15. Novel integration technique for silicon/III-V hybrid laser.

    PubMed

    Dong, Po; Hu, Ting-Chen; Liow, Tsung-Yang; Chen, Young-Kai; Xie, Chongjin; Luo, Xianshu; Lo, Guo-Qiang; Kopf, Rose; Tate, Alaric

    2014-11-01

    Integrated semiconductor lasers on silicon are one of the most crucial devices to enable low-cost silicon photonic integrated circuits for high-bandwidth optic communications and interconnects. While optical amplifiers and lasers are typically realized in III-V waveguide structures, it is beneficial to have an integration approach which allows flexible and efficient coupling of light between III-V gain media and silicon waveguides. In this paper, we propose and demonstrate a novel fabrication technique and associated transition structure to realize integrated lasers without the constraints of other critical processing parameters such as the starting silicon layer thicknesses. This technique employs epitaxial growth of silicon in a pre-defined trench with taper structures. We fabricate and demonstrate a long-cavity hybrid laser with a narrow linewidth of 130 kHz and an output power of 1.5 mW using the proposed technique. PMID:25401832

  16. Investigation of new semiinsulating behavior of III-V compounds

    NASA Technical Reports Server (NTRS)

    Lagowski, Jacek

    1990-01-01

    The investigation of defect interactions and properties related to semiinsulating behavior of III-V semiconductors resulted in about twenty original publications, six doctoral thesis, one masters thesis and numerous conference presentations. The studies of new compensation mechanisms involving transition metal impurities have defined direct effects associated with deep donor/acceptor levels acting as compensating centers. Electrical and optical properties of vanadium and titanium levels were determined in GaAs, InP and also in ternary compounds InGaAs. The experimental data provided basis for the verification of chemical trends and the VRBE method. They also defined compositional range for III-V mixed crystals whereby semiinsulating behavior can be achieved using transition elements deep levels and a suitable codoping with shallow donor/acceptor impurities.

  17. Method of fabricating vertically aligned group III-V nanowires

    DOEpatents

    Wang, George T; Li, Qiming

    2014-11-25

    A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

  18. Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

    SciTech Connect

    Tanaka, Masaaki; Ohya, Shinobu Nam Hai, Pham

    2014-03-15

    Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

  19. Laser induced chemical vapor phase epitaxial growth of III-V semiconductor films

    NASA Astrophysics Data System (ADS)

    Chu, Shirley S.; Chu, Ting L.

    1991-05-01

    The objective of this project is to investigate the homo- and hetero-epitaxial growth of device quality III-V semiconductor films by the free electron laser (FEL) induced growth at lower temperatures. An ArF excimer laser was used in this investigation. Metalorganic vapor phase epitaxy (MOVPE) is the commonly used technique in the growth of III-V compounds and alloys. The major concern to the use of MOVPE is the hazard involved in using highly toxic arsine and phosphine gases as the group V source materials. Efforts during this period have been focused to the homoepitaxial growth of GaAs and heteroepitaxial growth of InP on GaAs using alternate sources to eliminate the use of arsine and phosphine. Good quality epitaxial GaAs films have been prepared from elemental arsenic for the first time by either conventional substrate heating or laser enhanced processes. The epitaxial GaAs films grown from elemental arsenic are suitable for many GaAs based devices, particularly for large area devices such as solar cells. Significant cost reduction and less stringent safety requirements are major advantages.

  20. Superlattice and disorder effects on vibrations in III-V compounds

    NASA Astrophysics Data System (ADS)

    Jusserand, Bernard

    We analyse the perturbation induced either by a random atomic distribution (mixed crystal) or a one-dimensional periodic one (superlattice) onto the vibrations in III-V compounds and in particular onto the Raman backscattering active modes. As a consequence of the induced relaxation of the wavevector selection rule; some new modes become Raman active. We analyse their frequency and activity as a function of respectively the alloy concentration and the thicknesses of layers constituting the superlattice. We illustrate these results on structures based on the GaAs and AlAs compounds. Nous analysons la perturbation induite par une distribution atomique aléatoire (alliage) ou modulée périodiquement suivant une direction cristalline (superréseau) sur la dynamique de réseau des semiconducteurs III-V et sur les spectres de rétrodiffusion Raman correspondants. La relaxation de la loi de conservation du vecteur d'onde qui résulte de telles distributions permet l'observation de nouveaux modes en diffusion Raman. Nous analysons leurs fréquence et activité en fonction respectivement de la composition de l'alliage ou des paramètres structuraux du superréseau. Nous illustrons ces résultats dans le cas de structures à base des composés GaAs et AlAs.

  1. Defect Analysis in III-V Semiconductor Thin Films Grown by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Schulte, Kevin Louis

    Hydride vapor phase epitaxy (HVPE) is an epitaxial growth technique renowned for its ability to grow III-V semiconductors at high growth rates using lower cost reagents compared to metal-organic vapor phase epitaxy (MOVPE), the current industry standard. Recent interest in III-V photovoltaics has led to increased attention on HVPE. While the technique came to maturity in the 70s, much is unknown about how defects incorporate in HVPE-grown materials. Further understanding of how defects incorporate in III-V materials grown by HVPE is necessary to facilitate wider adoption of the technique. This information would inform strategies for minimizing and eliminating defects in HVPE materials, allowing for the formation of high performance devices. This investigation presents a study of multiple defects in III-V semiconductors grown by HVPE in the context of specific device applications, spanning point defects comprised of individual atoms to extended defects which propagate throughout the crystal. The incorporation of the arsenic anti-site defect, AsGa, intrinsic point defect was studied in high growth rate GaAs layers with potential photovoltaic applications. Relationships between growth conditions and incorporation of AsGa in GaAs epilayers were determined. The incorporation of AsGa depended strongly on the growth conditions employed, and a model was developed to predict the concentration of anti-site defects as a function of those growth conditions. Dislocations and anti-phase domain boundaries (APDBs), two types of extended defects, were investigated in the heteroepitaxial GaAs/Ge system. It was found that the use of 6° miscut substrates and specific growth temperatures led to elimination of APDBs. Dislocation densities were reduced through the use of high growth temperatures. The third and final application investigated was the growth of InxGa1-xAs metamorphic buffer layers (MBLs) by HVPE. The relationships between the growth conditions and the alloy composition were determined, and a model was developed to explain the observed behavior. Compositional grading strategies were explored and insight into the minimization of dislocations in these layers was developed. The dislocation microstructure was analyzed by TEM and related to the layer design, leading to the development of an atomic scale model for dislocation nucleation and propagation throughout the MBL layers.

  2. Low-Cost Growth of III-V Layers on Si Using Close-Spaced Vapor Transport

    SciTech Connect

    Boucher, Jason W.; Greenaway, Ann L.; Ritenour, Andrew J.; Davis, Allison L.; Bachman, Benjamin F.; Aloni, Shaul; Boettcher, Shannon W.

    2015-06-14

    Close-spaced vapor transport (CSVT) uses solid precursors to deposit material at high rates and with high precursor utilization. The use of solid precursors could significantly reduce the costs associated with III-V photovoltaics, particularly if growth on Si substrates can be demonstrated. We present preliminary results of the growth of GaAs1-xPx with x ≈ 0.3 and 0.6, showing that CSVT can be used to produce III-V-V’ alloys with band gaps suitable for tandem devices. Additionally, we have grown GaAs on Si by first thermally depositing films of Ge and subsequently depositing GaAs by CSVT. Patterning the Ge into islands prevents cracking due to thermal mismatch and is useful for potential tandem structures.

  3. Hybrid III-V/silicon SOA for photonic integrated circuits

    NASA Astrophysics Data System (ADS)

    Kaspar, P.; Brenot, R.; Le Liepvre, A.; Accard, A.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Duan, G.-H.; Olivier, S.; Jany, Christophe; Kopp, C.; Menezo, S.

    2014-11-01

    Silicon photonics has reached a considerable level of maturity, and the complexity of photonic integrated circuits (PIC) is steadily increasing. As the number of components in a PIC grows, loss management becomes more and more important. Integrated semiconductor optical amplifiers (SOA) will be crucial components in future photonic systems for loss compensation. In addition, there are specific applications, where SOAs can play a key role beyond mere loss compensation, such as modulated reflective SOAs in carrier distributed passive optical networks or optical gates in packet switching. It is, therefore, highly desirable to find a generic integration platform that includes the possibility of integrating SOAs on silicon. Various methods are currently being developed to integrate light emitters on silicon-on-insulator (SOI) waveguide circuits. Many of them use III-V materials for the hybrid integration on SOI. Various types of lasers have been demonstrated by several groups around the globe. In some of the integration approaches, SOAs can be implemented using essentially the same technology as for lasers. In this paper we will focus on SOA devices based on a hybrid integration approach where III-V material is bonded on SOI and a vertical optical mode transfer is used to couple light between SOI waveguides and guides formed in bonded III-V semiconductor layers. In contrast to evanescent coupling schemes, this mode transfer allows for a higher confinement factor in the gain material and thus for efficient light amplification over short propagation distances. We will outline the fabrication process of our hybrid components and present some of the most interesting results from a fabricated and packaged hybrid SOA.

  4. Recent Soviet microelectronics research on III-V compounds semiconductors

    SciTech Connect

    Sello, H.; Kirkpatrick, C.G.

    1988-08-01

    The activity in the Soviet Union on III-V compound semiconductor devices during the past five years is examined in the areas of materials, processes, radiation effects, and devices by a search of the translated technical journals. The majority of the work in III-V materials is concerned with gallium arsenide (GaAs), and the materials are certainly of the quality needed to make integrated circuits (ICs). However, the focus of Soviet growth and characterization studies appears to be basic materials properties, rather than development of capabilities and understanding for making integrated circuits. In processing, the Soviets appear to have very little effort on metaloorganic chemical vapor deposition on III-V compounds, while this is the process of choice in the West. There is, however, a substantial effort on X-ray lithography for silicon that could be extended to GaAs. High-quality work is also reported for ion beam, electron beam, optical projection, and laser processing silicon. Research on metallization (interconnection) and dielectric deposition processes for GaAs is absent. Soviet research on ion implantation and laser annealing in compound semiconductors is largely directed toward basic phenomena, such as defect information, rather than on electrical characteristics considered important for integrated circuit fabrication. Outstanding basic work is also being conducted on the radiation effects of electrons, protons, alpha, gamma, and X-rays on materials. These Soviet studies of radiation effects do not appear to be directed toward the fabrication of actual devices. Soviet GaAs device work appears to be generally of a theoretical nature, relying in part on device data obtained from Western articles. The most advanced involves the junction field effect transistor and heterojunction bipolar transistor, with little work reported on the fabrication of GaAs integrated circuits.

  5. III-V Growth on Silicon Toward a Multijunction Cell

    SciTech Connect

    Geisz, J.; Olson, J.; McMahon, W.; Friedman, D.; Kibbler, A.; Kramer, C.; Young, M.; Duda, A.; Ward, S.; Ptak, A.; Kurtz, S.; Wanlass, M.; Ahrenkiel, P.; Jiang, C. S.; Moutinho, H.; Norman, A.; Jones, K.; Romero, M.; Reedy, B.

    2005-11-01

    A III-V on Si multijunction solar cell promises high efficiency at relatively low cost. The challenges to epitaxial growth of high-quality III-Vs on Si, though, are extensive. Lattice-matched (LM) dilute-nitride GaNPAs solar cells have been grown on Si, but their performance is limited by defects related to the nitrogen. Advances in the growth of lattice-mismatched (LMM) materials make more traditional III-Vs, such as GaInP and GaAsP, very attractive for use in multijunction solar cells on silicon.

  6. Ultrabright and Ultrafast III-V Semiconductor Photocathodes

    NASA Astrophysics Data System (ADS)

    Karkare, Siddharth; Boulet, Laurent; Cultrera, Luca; Dunham, Bruce; Liu, Xianghong; Schaff, William; Bazarov, Ivan

    2014-03-01

    Crucial photoemission properties of layered III-V semiconductor cathodes are predicted using Monte Carlo simulations. Using this modeling, a layered GaAs structure is designed to reduce simultaneously the transverse energy and response time of the emitted electrons. This structure, grown by molecular beam epitaxy and activated to negative electron affinity, is characterized. The measured values of quantum efficiency and transverse energy are found to agree well with the simulations. Such advanced layered structures will allow generation of short electron bunches from photoinjectors with superior beam brightness.

  7. Ultrabright and ultrafast III-V semiconductor photocathodes.

    PubMed

    Karkare, Siddharth; Boulet, Laurent; Cultrera, Luca; Dunham, Bruce; Liu, Xianghong; Schaff, William; Bazarov, Ivan

    2014-03-01

    Crucial photoemission properties of layered III-V semiconductor cathodes are predicted using Monte Carlo simulations. Using this modeling, a layered GaAs structure is designed to reduce simultaneously the transverse energy and response time of the emitted electrons. This structure, grown by molecular beam epitaxy and activated to negative electron affinity, is characterized. The measured values of quantum efficiency and transverse energy are found to agree well with the simulations. Such advanced layered structures will allow generation of short electron bunches from photoinjectors with superior beam brightness. PMID:24655275

  8. III-V Infrared Research at the Jet Propulsion Laboratory

    NASA Technical Reports Server (NTRS)

    Gunapala, S. D.; Ting, D. Z.; Hill, C. J.; Soibel, A.; Liu, John; Liu, J. K.; Mumolo, J. M.; Keo, S. A.; Nguyen, J.; Bandara, S. V.; Tidrow, M. Z.

    2009-01-01

    Jet Propulsion Laboratory is actively developing the III-V based infrared detector and focal plane arrays (FPAs) for NASA, DoD, and commercial applications. Currently, we are working on multi-band Quantum Well Infrared Photodetectors (QWIPs), Superlattice detectors, and Quantum Dot Infrared Photodetector (QDIPs) technologies suitable for high pixel-pixel uniformity and high pixel operability large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). In addition, we will present the latest advances in QDIPs and Superlattice infrared detectors at the Jet Propulsion Laboratory.

  9. Recombination imaging of III-V solar cells

    NASA Technical Reports Server (NTRS)

    Virshup, G. F.

    1987-01-01

    An imaging technique based on the radiative recombination of minority carriers in forward-biased solar cells has been developed for characterization of III-V solar cells. When used in mapping whole wafers, it has helped identify three independent loss mechanisms (broken grid lines, shorting defects, and direct-to-indirect bandgap transitions), all of which resulted in lower efficiencies. The imaging has also led to improvements in processing techniques to reduce the occurrence of broken gridlines as well as surface defects. The ability to visualize current mechanisms in solar cells is an intuitive tool which is powerful in its simplicity.

  10. Supermode Silicon/III--V Lasers and Circular Bragg Lasers

    NASA Astrophysics Data System (ADS)

    Sun, Xiankai

    Semiconductor lasers are arguably the most important component in optical communications. This thesis investigates two types of semiconductor lasers that are useful in integrated optics. Part I focuses on supermode Si/III-V lasers and Part II discusses circular Bragg lasers for the application as surface-emitting lasers. Just as optical fibers have largely replaced the traditional copper wires in long-distance applications, people started to consider incorporating optical communication onto chips, primarily because the increased ohmic heating and RC delay associated with the metal interconnection prevent further increase in the data-processing rate. Si is well known to be the integration platform for electronics, and III-V materials (GaAs, InP, etc.) are efficient light emitters. It is natural to bring them together to realize the on-chip optical communication. Among various Si/III-V integration schemes the most promising is the hybrid Si evanescent platform in which a wafer-bonding technique that is compatible with current CMOS processing is used to bring Si and III-V materials together. Part I of this thesis focuses on the application of a novel mode-control method to such hybrid waveguide system to enhance the modal gain, which makes for more efficient and, most importantly, shorter devices that may hold the key to the photonics/electronics integration. The supermode theory is derived, the shortest adiabatic mode transformer is theoretically and numerically studied, and the device design and fabrication are presented, followed by the experimental demonstration of the performance enhancement in the mode-controlled Si/InGaAsP laser devices. Vertical cavity surface emitting lasers are a commercial light source for optical communications, but their single-modedness and good emission pattern are guaranteed only over a very small mode area (diameter of several microns) thus they have limitations in high-power applications. As an alternative, circular Bragg lasers can be designed as a superior surface emitting laser that produces high output power with good beam quality. Part II of this thesis presents a comprehensive and systematic theoretical study on the surface-emitting Hankel-phased circular Bragg lasers in various geometries. The analytical and numerical mode-solving methods will be described, followed by near- and above-threshold modal analyses.

  11. Carbon doping of III-V compound semiconductors

    SciTech Connect

    Moll, A.J.

    1994-09-01

    Focus of the study is C acceptor doping of GaAs, since C diffusion coefficient is at least one order of magnitude lower than that of other common p-type dopants in GaAs. C ion implantation results in a concentration of free holes in the valence band < 10% of that of the implanted C atoms for doses > 10{sup 14}/cm{sup 2}. Rutherford backscattering, electrical measurements, Raman spectroscopy, and Fourier transform infrared spectroscopy were amonth the techniques used. Ga co-implantation increased the C activation in two steps: first, the additional radiation damage creates vacant As sites that the implanted C can occupy, and second, it maintains the stoichiometry of the implanted layer, reducing the number of compensating native defects. In InP, the behavior of C was different from that in GaAs. C acts as n-type dopant in the In site; however, its incorporation by implantation was difficult to control; experiments using P co-implants were inconsistent. The lattice position of inactive C in GaAs in implanted and epitaxial layers is discussed; evidence for formation of C precipitates in GaAs and InP was found. Correlation of the results with literature on C doping in III-V semiconductors led to a phenomenological description of C in III-V compounds (particularly GaAs): The behavior of C is controlled by the chemical nature of C and the instrinsic Fermi level stabilization energy of the material.

  12. Applications of ion implantation in III-V device technology

    NASA Astrophysics Data System (ADS)

    Pearton, S. J.; Ren, F.; Chu, S. N. G.; Hobson, W. S.; Abernathy, C. R.; Fullowan, T. R.; Lothian, J. R.; Elliman, R. G.; Jacobson, D. C.; Poate, J. M.

    1993-06-01

    The use of implantation for doping and isolation of a variety of electronic and photonic III-V compound semiconductor devices will be reviewed. Complex multilayer heterostructure devices like heterojunction bipolar transistors and strained InGaAs-GaAs quantum well lasers rely on keV or MeV isolation implants, requiring thick, easily removed masks and post-implant annealing treatments to achieve high isolation resistances ( ? 10 8 ? cm). The effectiveness of the implant isolation technique varies as a function of the bandgap and elemental composition of the semiconductor. Devices based on GaAs, Al xGa 1-xAs and InGaP are particularly suited to the implant isolation method. The prime dopant species for III-V materials are Si for n-type layers and Be for p-type layers, although there is increasing interest in the use of C as an acceptor because of its low diffusivity. In the latter case, a group III species must be co-implanted with the C + ion to enhance the occupation of the group V lattice site.

  13. DX centers in III-V semiconductors under hydrostatic pressure

    SciTech Connect

    Wolk, J.A.

    1992-11-01

    DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si{sub Ga} shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity.

  14. Prospects of III-V Tunnel FETs for Logic Applications

    NASA Astrophysics Data System (ADS)

    Datta, Suman

    2015-03-01

    In order to continue and maintain the pace of energy efficient transistor scaling, it is imperative to scale the supply voltage of operation concurrently. In this invited paper, we discuss a promising III-V device architecture such as III-V Heterojunction Tunnel FETs that may break the seemingly inflexible energy vs. performance limit of silicon CMOS transistors and provide high performance, low leakage and low operating voltage for future logic transistor technology. Unlike conventional MOSFETs, the Tunnel FET (TFET) architecture employs a gate modulated Zener tunnel junction at the source which controls the transistor ON and OFF states. This scheme fundamentally eliminates the high-energy tail present in the Fermi-Dirac distribution of the valence band electrons in the p + source region and allows sub-kT/q steep slope device operation near the OFF state. This allows Tunnel FETs to achieve a much higher ION -IOFF ratio over a small gate voltage swing. A major challenge in the demonstration of high performance Tunnel FET is the limited rate of tunneling across the Zener junction which results in low drive current. Our results show, for the first time, that the on-current bottleneck in Tunnel FETs can be overcome by careful bandgap engineering. This work is supported by Intel, NRI/SRC and NSF through ASSIST NERC.

  15. Electronic bands and excited states of III-V semiconductor polytypes with screened-exchange density functional calculations

    SciTech Connect

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori; Freeman, Arthur J.

    2014-03-31

    The electronic band structures and excited states of III-V semiconductors such as GaP, AlP, AlAs, and AlSb for various polytypes are determined employing the screened-exchange density functional calculations implemented in the full-potential linearized augmented plane-wave methods. We demonstrate that GaP and AlSb in the wurtzite (WZ) structure have direct gap while III-V semiconductors in the zinc blende, 4H, and 6H structures considered in this study exhibit an indirect gap. Furthermore, we find that inclusion of Al atoms less than 17% and 83% in the hexagonal Al{sub x}Ga{sub 1?x}P and Al{sub x}Ga{sub 1?x}As alloys, respectively, leads to a direct transition with a gap energy of ?2.3 eV. The feasibility of III-V semiconductors with a direct gap in WZ structure offers a possible crystal structure engineering to tune the optical properties of semiconductor materials.

  16. Tetrahedral structures and phase transitions in III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Crain, J.; Piltz, R. O.; Ackland, G. J.; Clark, S. J.; Payne, M. C.; Milman, V.; Lin, J. S.; Hatton, P. D.; Nam, Y. H.

    1994-09-01

    The BC8 structure (body-centered cubic with eight atoms per cell) is a known pressure-induced modification of both silicon and germanium. However, its diatomic analogue [the SC16 structure (a simple cubic lattice with a basis of 16 atoms)] has never been found in compound semiconductors. We find from total-energy pseudopotential calculations that the SC16 structure is a stable high-pressure polymorph of the III-V semiconductors GaAs, InAs, and AlSb. We report ab initio calculations of the structural, electronic, and vibrational properties of SC16-GaAs. The wurtzite structure is found to be unstable at all pressures for each compound considered. We consider possible transition routes consistent with our high-pressure x-ray diffraction results and propose that the formation of the SC16 structure in compounds is kinetically inhibited by the formation of wrong bonds at the structural transition.

  17. Model of selective growth of III-V nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2015-12-01

    A kinetic model of growth of nanowires of III-V semiconductor compounds (including nitride ones) in the absence of metal catalyst is proposed; these conditions correspond to the methods of selective epitaxy or self-induced growth. A stationary solution for the nanowire growth rate is obtained, which indicates that the growth can be limited by not only the kinetics of III-group element with allowance for the surface diffusion (as was suggested earlier), but also the flow of the V-group element. Different modes are characterized by radically different dependences of the growth rate on the nanowire radius. Under arsenicenriched conditions, a typical dependence with a maximum and decay at large radii (limited by the gallium adatom diffusion) is observed. Under gallium-enriched conditions, there is a transition to the growth rate that is practically independent of the radius and linearly increases with an increase in the arsenic flow.

  18. Characteristics of III-V Semiconductor Devices at High Temperature

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Young, Paul G.; Taub, Susan R.; Alterovitz, Samuel A.

    1994-01-01

    This paper presents the development of III-V based pseudomorphic high electron mobility transistors (PHEMT's) designed to operate over the temperature range 77 to 473 K (-196 to 200 C). These devices have a pseudomorphic undoped InGaAs channel that is sandwiched between an AlGaAs spacer and a buffer layer; gate widths of 200, 400, 1600, and 3200 micrometers; and a gate length of 2 micrometers. Measurements were performed at both room temperature and 473 K (200 C) and show that the drain current decreases by 30 percent and the gate current increases to about 9 microns A (at a reverse bias of -1.5 V) at the higher temperature. These devices have a maximum DC power dissipation of about 4.5 W and a breakdown voltage of about 16 V.

  19. Annealing furnace for III-V semiconductor devices

    NASA Astrophysics Data System (ADS)

    O'Connor, J. M.; Hier, H. S.; Ketchum, R. M.

    1986-02-01

    A furnace for annealing ion implantation damage in III-V semiconductors has been built and tested. Designed for research applications, the furnace can accommodate odd shapes of material up to 2 in. in diameter. Samples are loaded onto a novel cantilevered support and are not moved during the annealing operation, facilitating proximity annealing techniques. Both chambers of this dual chambered system are O-ring sealed for added safety during annealing in an arsine gas ambient. Electron mobilities between 4400 and 4600 cm2/V s at 300 K are routinely measured for 21017 cm-3 gallium arsenide material annealed in this sytem. The system has been used to anneal indium phosphide as well as gallium arsenide wafers.

  20. High rate ECR etching of III-V nitride materials

    SciTech Connect

    Shul, R.J.; Howard, A.J.; Kilcoyne, S.P.; Pearton, S.J.; Abernathy, C.R.; Vartuli, C.B.; Barnes, P.A.; Bozack, M.J.

    1994-12-31

    The III-V nitride compound semiconductors are attracting considerable attention for blue and ultraviolet light emitting diodes (LEDs) and lasers as well as high temperature electronics due to their wide band gaps and high dielectric constants. The recent progress observed in the growth of these materials has not been matched by progress in processing techniques to fabricate more highly sophisticated devices. Patterning these materials has been especially difficult due to the relatively inert chemical nature of the group-III nitrides. The authors review dry etch techniques which have been used to pattern these materials including electron cyclotron resonance (ECR), reactive ion etch (RIE), and chemically assisted ion beam etching (CAIBE). ECR etch rates greater than 3,800 {angstrom}/min for InN, 3,500 {angstrom}/min for GaN, and 1,170 A/min for AlN are reported. Etch anisotropy, surface morphology, and near-surface stoichiometry will be discussed.

  1. III-V Compound Detectors for CO2 DIAL Measurements

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Abedin, M. Nurul; Sulima, Oleg V.; Ismail, Syed; Singh, Upendra N.

    2005-01-01

    Profiling of atmospheric carbon dioxide (CO2) is important for understanding the natural carbon cycle on Earth and its influence on global warming and climate change. Differential absorption lidar is a powerful remote sensing technique used for profiling and monitoring atmospheric constituents. Recently there has been an interest to apply this technique, at the 2 m wavelength, for investigating atmospheric CO2. This drives the need for high quality detectors at this wavelength. Although 2 m detectors are commercially available, the quest for a better detector is still on. The detector performance, regarding quantum efficiency, gain and associated noise, affects the DIAL signal-to-noise ratio and background signal, thereby influencing the instrument sensitivity and dynamic range. Detectors based on the III-V based compound materials shows a strong potential for such application. In this paper the detector requirements for a long range CO2 DIAL profiles will be discussed. These requirements were compared to newly developed III-V compound infrared detectors. The performance of ternary InGaSb pn junction devices will be presented using different substrates, as well as quaternary InGaAsSb npn structure. The performance study was based on experimental characterization of the devices dark current, spectral response, gain and noise. The final results are compared to the current state-of-the-art InGaAs technology. Npn phototransistor structure showed the best performance, regarding the internal gain and therefore the device signal-to-noise ratio. 2-micrometers detectivity as high as 3.9 x 10(exp 11) cmHz(sup 1/2)/W was obtained at a temperature of -20 C and 4 V bias voltage. This corresponds to a responsivity of 2650 A/W with about 60% quantum efficiency.

  2. Effect of III-V on insulator structure on quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Takashima, Seiya; Ikku, Yuki; Takenaka, Mitsuru; Takagi, Shinichi

    2016-04-01

    To achieve the monolithic active/passive integration on the III-V CMOS photonics platform, quantum well intermixing (QWI) on III-V on insulator (III-V-OI) is studied for fabricating multi-bandgap III-V-OI wafers. By optimizing the QWI condition for a 250-nm-thick III-V layer, which contains a five-layer InGaAsP-based multi-quantum well (MQW) with 80-nm-thick indium phosphide (InP) cladding layers, we have successfully achieved a photoluminescence (PL) peak shift of over 100 nm on the III-V-OI wafer. We have also found that the progress of QWI on the III-V-OI wafer is slower than that on the InP bulk wafer regardless of the buried oxide (BOX) thickness, bonding interface materials, and handle wafers. We have also found that the progress of QWI on the III-V-OI wafer is slower than that on the InP bulk wafer regardless of the buried oxide (BOX) thickness, bonding interface materials, and bulk support wafers on which the III-V-OI structure is formed (handle wafers). By comparing between the measured PL shift and simulated diffusions of phosphorus vacancies and interstitials during QWI, we have found that the slow QWI progress in the III-V-OI wafer is probably attributed to the enhanced recombination of vacancies and interstitials by the diffusion blocking of vacancies and interstitials at the BOX interface.

  3. Methods for fabricating thin film III-V compound solar cell

    DOEpatents

    Pan, Noren; Hillier, Glen; Vu, Duy Phach; Tatavarti, Rao; Youtsey, Christopher; McCallum, David; Martin, Genevieve

    2011-08-09

    The present invention utilizes epitaxial lift-off in which a sacrificial layer is included in the epitaxial growth between the substrate and a thin film III-V compound solar cell. To provide support for the thin film III-V compound solar cell in absence of the substrate, a backing layer is applied to a surface of the thin film III-V compound solar cell before it is separated from the substrate. To separate the thin film III-V compound solar cell from the substrate, the sacrificial layer is removed as part of the epitaxial lift-off. Once the substrate is separated from the thin film III-V compound solar cell, the substrate may then be reused in the formation of another thin film III-V compound solar cell.

  4. Dopant Profiling of III-V Nanostructures for Electronic Applications

    NASA Astrophysics Data System (ADS)

    Ford, Alexandra Caroline

    2011-12-01

    High electron mobility III-V compound semiconductors such as indium arsenide (InAs) are promising candidates for future active channel materials of electron devices to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. However, one of the primary challenges of III-V device fabrication is controllable, post-growth dopant profiling. Here InAs nanowires and ultrathin layers (nanoribbons) on SiO2/Si are investigated as the channel material for high performance field-effect transistors (FETs) and post-growth, patterned doping techniques are demonstrated. First, the synthesis of crystalline InAs nanowires with high yield and tunable diameters by using Ni nanoparticles as the catalyst material on SiO 2/Si substrates is demonstrated. The back-gated InAs nanowire FETs have electron field-effect mobilities of ˜4,000 cm2/Vs and ION/IOFF ˜104. The uniformity of the InAs nanowires is demonstrated by large-scale assembly of parallel arrays of nanowires (˜400 nanowires) on SiO2/Si substrates by a contact printing process. This enables high performance, "printable" transistors with 5--10 mA ON currents. Second, an epitaxial transfer method for the integration of ultrathin layers of single-crystalline InAs on SiO2/Si substrates is demonstrated. As a parallel to silicon-on-insulator (SOI) technology, the abbreviation "XOI" is used to represent this compound semiconductor-on-insulator platform. A high quality InAs/dielectric interface is obtained by the use of a thermally grown interfacial InAsOx layer (˜1 nm thick). Top-gated FETs exhibit a peak transconductance of ˜1.6 mS/microm at V DS=0.5V with ION/I OFF >104 and subthreshold swings of 107--150 mV/decade for a channel length of ˜0.5 microm. Next, temperature-dependent I-V and C-V studies of single InAs nanowire FETs are utilized to investigate the intrinsic electron transport properties as a function of nanowire radius. From C-V characterization, the densities of thermally-activated fixed charges and trap states on the surface of as-grown (unpassivated) nanowires are investigated to allow the accurate measurement of the gate oxide capacitance. This allows the direct assessment of the electron field-effect mobility. The field-effect mobility is found to monotonically decrease as the radius is reduced to sub-10 nm, with the low temperature transport data highlighting the impact of surface roughness scattering on the mobility degradation for smaller radius nanowires. Next, the electrical properties of the InAs XOI transistors are studied, showing the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Following the investigation of the electrical properties of undoped InAs nanostructures, post-growth, surface doping processes for InAs nanostructures are addressed. Nanoscale, sulfur doping of InAs planar substrates with high dopant areal dose and uniformity by using a self-limiting monolayer doping approach is demonstrated as a means to create ultrashallow junctions. From transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), a dopant profile abruptness of ˜3.5 nm/decade is observed without significant lattice damage. The n+/ p+ junctions fabricated using this doping method exhibit negative differential resistance (NDR) behavior, demonstrating the utility of this approach for device fabrication with high electrically active sulfur concentrations of ˜8x1018 cm-3. Next, a gas phase doping approach for InAs nanowires and ultrathin XOI layers using zinc is demonstrated as an effective means for enabling post-growth dopant profiling of nanostructures. The versatility of the approach is demonstrated by the fabrication of gated diodes and p-MOSFETs. Electrically active zinc concentrations of ˜1x1019 cm-3 are achieved which is necessary for compensating the high electron concentration at the surface of InAs to enable heavily p-doped structures. This work could have important applications for the fabrication of planar and non-planar devices based on InAs and other III-V nanostructures which are not compatible with conventional ion implantation processes that often cause severe lattice damage and local stoichiometry imbalance. Lastly, an ultrathin body InAs XOI tunneling field-effect transistor (TFET) on Si substrate is demonstrated. The post-growth, zinc surface doping approach is used for the formation of a p+ source contact which minimizes lattice damage to the ultrathin body InAs XOI compared to ion implantation. The transistor exhibits gated NDR behavior under forward bias, confirming the tunneling operation of the device. In this device architecture, the ON current is dominated by vertical band-to-band tunneling and is thereby less sensitive to the junction abruptness. This work presents a device and materials platform for studying III-V tunnel transistors.

  5. Surface Sum Frequency Generation of III-V Semiconductors

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Kim, Jisun; Khoury, Rami; Plummer, E. W.; Haber, Louis

    2015-03-01

    Optical sum frequency generation (SFG) is a well-established technique for surface and interface studies but its use has been limited mainly to centrosymmetric materials so far. Here, we demonstrate that femtosecond broadband SFG spectroscopy has the ability to identify surface molecular vibrations on the archetypical non-centrosymmetric semiconductor GaAs (001), in which the bulk SFG signal typically dominates over surface SFG contributions. Azimuthal angle dependence of the second order SFG nonlinear response from GaAs (001) surface in the reflection geometry in vacuum for all eight polarization combinations are detected and analyzed. The results agree with and extend upon previous second harmonic generation (SHG) studies and phenomenological analysis. In addition, carbon monoxide and methanol are employed as molecular-markers on the GaAs (001) surfaces. The C-O stretching mode of carbon monoxide and the methyl group stretching modes of methanol are clearly observed even though the bulk contribution dominates the SFG signal. Coherent heterodyne interference is proposed as the mechanism for the surface signal enhancement. Two other zinc blende type III-V semiconductors, GaP and GaSb, are also studied and compared. Funded by EFRC.

  6. III-V semiconductor processing: Contacts, etching, and devices

    NASA Astrophysics Data System (ADS)

    Laroche, Jeffrey Ryan

    Semiconductor processing of III-V materials is a vast topic, but this dissertation focuses on contacts, etching, and devices in very specific ways. The first chapter investigates the use of e-beam deposited SiO and SiO 2 to prevent galvanic effect etching of AuGe contacts for GaAs intergrated circuits. In the second chapter, the material characteristics of e-beam deposited SiO and SiO2 as hydrogen free dielectrics are studied. The third chapter shows how the overhang visible on the (011) GaAs cross-section can be eliminated during wet-etching, making metallization possible in any direction. Chapter four discusses the fabrication of PNP InGaAsN heterojunction and double heterojunction bipolar transistors for low power applications. Chapter five shows the first efforts of our group in the field of spintronics. Fabrication methods for processing a spin field effect transistor on an InGaAs/InAlAs system are explored. Finally, chapter six outlines testing of spin field effect devices and the group's ongoing efforts in this area.

  7. Hydrogen-impurity complexes in III V semiconductors

    NASA Astrophysics Data System (ADS)

    Ulrici, W.

    2004-12-01

    This review summarizes the presently available knowledge concerning hydrogen-impurity complexes in III-V compounds. The impurities form shallow acceptors on group III sites (Be, Zn, Cd) and on group V sites (C, Si, Ge) as well as shallow donors on group V sites (S, Se, Te) and on group III sites (Si, Sn). These complexes are mainly revealed by their hydrogen stretching modes. Therefore, nearly all information about their structure and dynamic properties is derived from vibrational spectroscopy. The complexes of shallow impurities with hydrogen have been most extensively investigated in GaAs, GaP and InP. This holds also for Mg-H in GaN. The complexes exhibit a different microscopic structure, which is discussed in detail. The isoelectronic impurity nitrogen, complexed with one hydrogen atom, is investigated in detail in GaAs and GaP. Those complexes can exist in different charge states. The experimental results such as vibrational frequencies, the microscopic structure and the activation energy for reorientation for many of these complexes are in very good agreement with results of ab initio calculations. Different types of oxygen-hydrogen complexes in GaAs and GaP are described, with one hydrogen atom or two hydrogen atoms bonded to oxygen. Three of these complexes in GaAs were found to be electrically active.

  8. Thermal conductivity of III-V semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Mei, S.; Knezevic, I.

    2015-11-01

    This paper presents a semiclassical model for the anisotropic thermal transport in III-V semiconductor superlattices (SLs). An effective interface rms roughness is the only adjustable parameter. Thermal transport inside a layer is described by the Boltzmann transport equation in the relaxation time approximation and is affected by the relevant scattering mechanisms (three-phonon, mass-difference, and dopant and electron scattering of phonons), as well as by diffuse scattering from the interfaces captured via an effective interface scattering rate. The in-plane thermal conductivity is obtained from the layer conductivities connected in parallel. The cross-plane thermal conductivity is calculated from the layer thermal conductivities in series with one another and with thermal boundary resistances (TBRs) associated with each interface; the TBRs dominate cross-plane transport. The TBR of each interface is calculated from the transmission coefficient obtained by interpolating between the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM), where the weight of the AMM transmission coefficient is the same wavelength-dependent specularity parameter related to the effective interface rms roughness that is commonly used to describe diffuse interface scattering. The model is applied to multiple III-arsenide superlattices, and the results are in very good agreement with experimental findings. The method is both simple and accurate, easy to implement, and applicable to complicated SL systems, such as the active regions of quantum cascade lasers. It is also valid for other SL material systems with high-quality interfaces and predominantly incoherent phonon transport.

  9. Short-wavelength III-V LEDs and their applications

    NASA Astrophysics Data System (ADS)

    Uemura, Toshiya; Shibata, Naoki; Yamaguchi, Hisao; Yasukawa, Takemasa

    2003-07-01

    III-V nitride semiconductors are suitable for LEDs having color range from blue to green. Luminous intensity and color purity of these LEDs are so high that they have been used for many applications for full color display and LCD backlight and so on. In addition to natural colored LEDs, we have developed short wavelength LED, named TG Purple, which wavelength is typically around 380nm. TG Purple has been realized by controlling Indium composition in GaInN well layers. It can activate photo-catalysts such as TiOx, and therefore, the air purifier for automotive has been developed by combining TG Purple and TiOx photo-catalyst. The short wavelength LED is now the best light source for automotive air purifier using photo-catalyst, because LEDs fulfill the mercury-less requirement for an environmental issue and don't need special circuit like conventional UV lamps such as black light lamps and cold cathode lamps. Furthermore this short wavelength LED is used for phosphor excitation that generates many colors like blue, green, red, etc. It is likely that, with this technology, LEDs will take some part in illumination market as one of primary light sources like incandescent lamps and fluorescent lamps.

  10. Electrical characterization of surface passivation in III-V nanowires

    NASA Astrophysics Data System (ADS)

    Holloway, Gregory; Lapierre, Ray; Baugh, Jonathan

    III-V nanowires are promising for implementing many useful technologies including optical sensing and quantum information processing. However, most native nanowires have a significant density of surface states, which cause electron accumulation at the surface and make the optoelectronic characteristics very sensitive to surface conditions and variable from device to device. To achieve optimum device performance it is imperative to decrease the density of these defects, since they are responsible for charge noise (e.g. random telegraph noise) and decreased carrier mobility. Here we report on experimental results from low temperature transport studies of a series of InAs nanowire field effect transistors, each fabricated with a different surface passivation technique. The different surface treatments include combinations of chemical passivation, growth of a thermal oxide, and deposition of a high-k dielectric to determine the optimum process for passivating the surface states. To better quantify the density of surface states, we also study the axial field magnetoconductance of short-channel nanowire transistors, and show how the results can be used to estimate the degree of surface band-bending.

  11. Antisites in III-V semiconductors: Density functional theory calculations

    SciTech Connect

    Chroneos, A.; Tahini, H. A.; Schwingenschlögl, U.; Grimes, R. W.

    2014-07-14

    Density functional based simulation, corrected for finite size effects, is used to investigate systematically the formation of antisite defects in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb). Different charge states are modelled as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites (III{sub V}{sup q}) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites (V{sub III}{sup q}) show a consistent decrease in formation energies with increase in group III and group V covalent radii. In general, III{sub V}{sup q} defects dominate under III-rich conditions and V{sub III}{sup q} under V-rich conditions. Comparison with equivalent vacancy formation energy simulations shows that while antisite concentrations are always dominant under stoichiometric conditions, modest variation in growth or doping conditions can lead to a significantly higher concentration of vacancies.

  12. Heterogeneously integrated III-V laser on thin SOI with compact optical vertical interconnect access.

    PubMed

    Pu, Jing; Lim, Kim Peng; Ng, Doris Keh Ting; Krishnamurthy, Vivek; Lee, Chee Wei; Tang, Kun; Seng Kay, Anthony Yew; Loh, Ter Hoe; Wang, Qian

    2015-04-01

    A new heterogeneously integrated III-V/Si laser structure is reported in this report that consists of a III-V ridge waveguide gain section on silicon, III-V/Si optical vertical interconnect accesses (VIAs), and silicon-on-insulator (SOI) nanophotonic waveguide sections. The III-V semiconductor layers are introduced on top of the 300-nm-thick SOI layer through low temperature, plasma-assisted direct wafer-bonding and etched to form a III-V ridge waveguide on silicon as the gain section. The optical VIA is formed by tapering the III-V and the beneath SOI in the same direction with a length of 50 μm for efficient coupling of light down to the 600 nm wide silicon nanophotonic waveguide or vice versa. Fabrication details and specification characterizations of this heterogeneous III-V/Si Fabry-Perot (FP) laser are given. The fabricated FP laser shows a continuous-wave lasing with a threshold current of 65 mA at room temperature, and the slope efficiency from single facet is 144  mW/A. The maximal single facet emitting power is about 4.5 mW at a current of 100 mA, and the side-mode suppression ratio is ∼30  dB. This new heterogeneously integrated III-V/Si laser structure demonstrated enables more complex laser configuration with a sub-system on-chip for various applications. PMID:25831337

  13. Thermal oxidation of III-V compound semiconductors

    SciTech Connect

    Neto, O.R.M.

    1988-11-01

    Thermal oxidation of III-V compound semiconductors has been studied in the temperature range of 300/degree/C to 600/degree/C. Two members of this class of materials, namely InP and GaAs, were the object of the experimental work carried out here. The main analytical tools used were transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS). TEM was employed to access microstructural changes and SIMS to access the composition redistribution that takes place as a consequence of the oxidation reaction. Below 400/degree/C oxidation of both materials led to the formation of amorphous scales, which consisted of a mixture of gallium and arsenic oxides in the case of GaAs, and indium phosphate and oxide in the case of InP. The oxidation kinetics of InP was found to be slower than that of GaAs. In the high temperature regime, i.e., above 400/degree/C, the oxidation of both materials resulted in crystalline products. Precipitation of the group V element at the scale/semiconductor interface took place during oxidation. At the GaAs/Ga/sub 2/O/sub 3/interface, As precipitates were formed with a truncated square pyramid shape bound by /l brace/111/r brace//sub GaAs/ planes. The precipitates found at the InPO/sub 4//InP interface were either a phosphorus rich phase or red phosphorus. Strong vaporization under the electron beam prohibited a more accurate determination. The morphology of those precipitates were very similar to the As ones in GaAs. 83 refs., 48 figs., 6 tabs.

  14. Gas-source molecular beam epitaxy of III V nitrides

    NASA Astrophysics Data System (ADS)

    Davis, R. F.; Paisley, M. J.; Sitar, Z.; Kester, D. J.; Ailey, K. S.; Linthicum, K.; Rowland, L. B.; Tanaka, S.; Kern, R. S.

    1997-06-01

    Amorphous, hexagonal and cubic phases of BN were grown via ion beam assisted deposition on Si(1 0 0) substrates. Gas-source molecular beam epitaxy of the III-V nitrides is reviewed. Sapphire(0 0 0 1) is the most commonly employed substrate with 6H-SiC(0 0 0 1), ZnO(1 1 1) and Si(1 1 1) also being used primarily for the growth of wurtzite GaN(0 0 0 1) in tandem with previously deposited GaN(0 0 0 1) or AlN(0 0 0 1) buffer layers. Silicon(0 0 1), GaAs(0 0 1), GaP(0 0 1) and 3C-SiC(0 0 1) have been employed for growth of cubic (zincblende) β-GaN(0 0 1). The precursor materials are evaporated metals and reactive N species produced either via ECR or RF plasma decomposition of N 2 or from ammonia. However, point defect damage from the plasma-derived species has resulted in a steady increase in the number of investigators now using ammonia. The growth temperatures for wurtzite GaN have increased from 650 ± 50°C to 800 ± 50°C to enhance the surface mobility of the reactants and, in turn, the efficiency of decomposition of ammonia and the microstructure and the growth rate of the films. Doping has been achieved primarily with Si (donor) and Mg (acceptor); the latter has been activated without post-growth annealing. Simple heterostructures, a p-n junction LED and a modulation-doped field-effect transistor have been achieved using GSMBE-grown material.

  15. Radiation effects on III-V heterostructure devices

    NASA Astrophysics Data System (ADS)

    Jun, Bongim

    The neutron and electron radiation effects in III-V compound semiconductor heterostructure devices are studied in this thesis. Three types of devices investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs), AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors (HIGFETs), and InP/InGaAs/InGaAs single heterojunction bipolar transistors (SHBTs). HEMTs and HIGFETs are primarily investigated for neutron irradiation effects. Detailed optimized processing of HEMT devices is introduced. Numerical as well as analytical models that incorporate radiation-induced degradation effects in HEMTs and HIGFETs are developed. The most prominent radiation effects appearing on both HEMT and HIGFET devices are increase of threshold voltage (VT) and decrease of transconductance (gm) as radiation dose increases. These effects are responsible for drain current degradation under given bias conditions after irradiation. From our experimental neutron irradiation study and our theoretical models, we concluded that threshold voltage increase is due to the radiation-induced acceptor-like (negatively charged) traps in the GaAs channel region removing carriers. The mobility degradation in the channel is responsible for gm decrease. Series resistance increase is also related to carrier removal and mobility degradation. Traps introduced in the GaAs region affect the device performance more than the traps in the AlGaAs doped region. V T and gm of HIGFET devices are less affected by neutron radiation than they are in HEMTs. This difference is attributed to different shapes of the quantum well in the two devices. The main effects of electron and neutron irradiation of SHBTs are decrease of collector current (IC), decrease of common-emitter DC gain, increase of the collector output conductance (DeltaI C/DeltaVCE), and increase of collector-collector offset voltage. The decrease of breakdown voltage of reverse biased base-emitter junction diode is responsible for increasing the output conductance after irradiation. Base-collector junction degradation also induces collector-emitter offset voltage increase.

  16. Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications

    PubMed Central

    Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, SangHyeon; Choi, Won Jun

    2016-01-01

    Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called “Si photonics”). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates. PMID:26864968

  17. Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications

    NASA Astrophysics Data System (ADS)

    Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, Sanghyeon; Choi, Won Jun

    2016-02-01

    Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called “Si photonics”). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates.

  18. Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications.

    PubMed

    Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, SangHyeon; Choi, Won Jun

    2016-01-01

    Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called "Si photonics"). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates. PMID:26864968

  19. Characterization of III-V materials by optical interferometry

    NASA Astrophysics Data System (ADS)

    Montgomery, P. C.; Vabre, P.; Montaner, D.; Fillard, J. P.

    1993-09-01

    Digital interference microscopy is a new measuring technique with submicron horizontal resolution and nanometric vertical resolution, that can be used for the three-dimensional analysis of surface defects and device features in many microelectronics applications on bulk materials and epitaxial layers. In this paper we show how certain defects can be analysed on III-V materials and devices using two different interferometric techniques. The choice of the technique depends on the height and the slope of the surface features to be measured. We show that small defects less than λ/2 in height, or surfaces with shallow continuous slopes upto one or two microns high are best profiled with the phase stepping technique (PSM) because of the high vertical resolution of 1 nm and the higher speed and precision. This is illustrated by studies of the surface polish of InP wafers, defects after chemical etching of tin doped InP, defects on an epitaxial layer of GaAs on InP and quantum dot structures on GaAs. For measuring devices which contain mesas and grooves with step heights greater than λ/2, the peak fringe scanning (PFSM) method is the better choice. The vertical resolution is slightly less (4 nm), but the vertical range is higher (upto 15 μm) as demonstrated with the measurement of an etched groove in a laser/detector device on a quaternary layer on InP, and a MESFET device on GaAs. Compared with electron microscopy and the new near field scanning techniques, digital interference microscopy has the advantages of ease of use and speed of analysis and being able to resolve certain problems that are difficult or not possible by other means, such as profiling deep narrow etched grooves, or measuring the relief of a surface hidden under a transparent layer. The main disadvantages are that the horizontal resolution is limited to the resolving power of the objective and that errors due to variations in the optical properties of the sample need to be taken into account. La microscopie interférentielle numérique est une nouvelle méthode de mesure qui a une résolution latérale micronique et une résolution verticale nanométrique. Ceci est utile pour l'analyse tri-dimensionnelle des défauts de surface et de la forme des composants dans beaucoup d'applications sur les matériaux massifs et épitaxiés. Dans cet article nous démontrons comment certains défauts peuvent être analysés sur les matériaux et les composants III-V avec deux méthodes interférométriques différentes. La microscopie à saut de phase est mieux adaptée, avec sa résolution de 1 nm et sa meilleure précision, à la mesure des petits défauts de moins de λ/2 en hauteur, ou des surfaces avec des pentes douces et continues, jusqu'à une altitude de 1 ou 2 μm. Ceci est illustré par les études du polissage de plaquettes d'InP, des défauts sur une couche épitaxiée de GaAs sur InP et des boîtes quantiques sur GaAs. Pour mesurer les motifs, les mésas et les sillons qui ont des marches de plus que λ/2, la microscopie à glissement de franges est le meilleur choix. La résolution verticale est un peu moins bonne que celle de la PSM (4 nm) mais la dynamique verticale est plus grande (15 μm). Ceci est démontré par les mesures d'un sillon gravé dans une structure laser/détecteur sur une couche quaternaire sur InP et d'un MESFET sur GaAs. En comparaison avec la microscopie électronique et les méthodes de champ proche, la microscopie interférentielle numérique a les avantages de la facilité d'utilisation et de la rapidité. Elle est également capable de résoudre certains problèmes difficiles ou insolubles avec les autres techniques, comme par exemple le profil des sillons étroits, ou la mesure des reliefs enterrés sous une couche transparente. Les inconvénients sont la résolution latérale qui est limitée au pouvoir résolutif de l'objectif et l'introduction d'erreurs liées aux variations des propriétés optiques de l'échantillon qui doivent être prises en compte.

  20. III-V-on-silicon anti-colliding pulse-type mode-locked laser.

    PubMed

    Keyvaninia, S; Uvin, S; Tassaert, M; Wang, Z; Fu, X; Latkowski, S; Marien, J; Thomassen, L; Lelarge, F; Duan, G; Lepage, G; Verheyen, P; Van Campenhout, J; Bente, E; Roelkens, G

    2015-07-01

    An anti-colliding pulse-type III-V-on-silicon passively mode-locked laser is presented for the first time based on a III-V-on-silicon distributed Bragg reflector as outcoupling mirror implemented partially underneath the III-V saturable absorber. Passive mode-locking at 4.83 GHz repetition rate generating 3 ps pulses is demonstrated. The generated fundamental RF tone shows a 1.7 kHz 3 dB linewidth. Over 9 mW waveguide coupled output power is demonstrated. PMID:26125366

  1. Effects of Humidity on Non-Hermetically Packaged III-V Structures and Devices

    NASA Technical Reports Server (NTRS)

    Leon, R.; Martin, S.; Lee, T.; Okuno, J.; Ruiz, R.; Gauldin, R.; Gaidis, M.; Smith, R.

    1999-01-01

    High humidity and temperature test (known as 85/85 tests) were performed on various III-V devices and structures to determine environmental effects in non-hermetically packaged GaAs membrane mixer diodes.

  2. The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report

    SciTech Connect

    Anderson, T.J.

    1998-07-21

    The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

  3. Investigation of III-V semiconductor heterostructures for post-Si-CMOS applications

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Kunal

    Silicon complementary metal-oxide-semiconductor (CMOS) technology in the past few decades has been driven by aggressive device scaling to increase performance, reduce cost and lower power consumption. However, as devices are scaled below the 100 nm region, performance gain has become increasingly difficult to obtain by traditional scaling. As we move towards advanced technology nodes, materials innovation and physical architecture are becoming the primary enabler for performance enhancement in CMOS technology rather than scaling. One class of materials that can potentially result in improved electrical performance are III-V semiconductors, which are ideal candidates for replacing the channel in Si CMOS owing to their high electron mobilities and capabilities for band-engineering. This work is aimed towards the growth and characterization of III-V semiconductor heterostructures and their application in post-Si-CMOS devices. The two main components of this study include the integration of III-V compound semiconductors on silicon for tunnel-junction Esaki diodes, and the investigation of carrier transport properties in low-power III-V n-channel FETs under uniaxial strain for advanced III-V CMOS solutions. The integration of III-V compound semiconductors with Si can combine the cost advantage and maturity of the Si technology with the superior performance of III-V materials. We have demonstrated high quality epitaxial growth of GaAs and GaSb on Si (001) wafers through the use of various buffer layers including AlSb and crystalline SrTiO3. These GaSb/Si virtual substrates were used for the fabrication and characterization of InAs/GaSb broken-gap Esaki-tunnel diodes as a possible solution for heterojunction Tunnel-FETs. In addition, the carrier transport properties of InAs channels were evaluated under uniaxial strain for the potential use of strain solutions in III-V CMOS.

  4. Self-organization of polarization-dependent periodic nanostructures embedded in III-V semiconductor materials

    NASA Astrophysics Data System (ADS)

    Shimotsuma, Y.; Sei, T.; Mori, M.; Sakakura, M.; Miura, K.

    2016-03-01

    Space-selective nanostructuring inside various III-V semiconductor materials containing gallium element has been accomplished by focused irradiation of IR femtosecond laser pulses. To elucidate the formation mechanisms of periodic nanostructures, we systematically classified III-V semiconductor materials in which polarization-dependent periodic nanostructure can be formed. Self-organization of the periodic nanostructures could be induced empirically only if it is indirect bandgap semiconductor, namely GaP.

  5. Structural and optical properties of II-VI and III-V compound semiconductors

    NASA Astrophysics Data System (ADS)

    Huang, Jingyi

    This dissertation is on the study of structural and optical properties of some III-V and II-VI compound semiconductors. The first part of this dissertation is a study of the deformation mechanisms associated with nanoindentation and nanoscratching of InP, GaN, and ZnO crystals. The second part is an investigation of some fundamental issues regarding compositional fluctuations and microstructure in GaInNAs and InAlN alloys. In the first part, the microstructure of (001) InP scratched in an atomic force microscope with a small diamond tip has been studied as a function of applied normal force and crystalline direction in order to understand at the nanometer scale the deformation mechanisms in the zinc-blende structure. TEM images show deeper dislocation propagation for scratches along <110> compared to <100>. High strain fields were observed in <100> scratches, indicating hardening due to locking of dislocations gliding on different slip planes. Reverse plastic flow have been observed in <110> scratches in the form of pop-up events that result from recovery of stored elastic strain. In a separate study, nanoindentation-induced plastic deformation has been studied in c-, a-, and m-plane ZnO single crystals and c-plane GaN respectively, to study the deformation mechanism in wurtzite hexagonal structures. TEM results reveal that the prime deformation mechanism is slip on basal planes and in some cases, on pyramidal planes, and strain built up along particular directions. No evidence of phase transformation or cracking was observed in both materials. CL imaging reveals quenching of near band-edge emission by dislocations. In the second part, compositional inhomogeneity in quaternary GaInNAs and ternary InAlN alloys has been studied using TEM. It is shown that exposure to antimony during growth of GaInNAs results in uniform chemical composition in the epilayer, as antimony suppresses the surface mobility of adatoms that otherwise leads to two-dimensional growth and elemental segregation. In a separate study, compositional instability is observed in lattice-matched InAlN films grown on GaN, for growth beyond a certain thickness. Beyond 200 nm of thickness, two sub-layers with different indium content are observed, the top one with lower indium content.

  6. Direct growth of single-crystalline III-V semiconductors on amorphous substrates.

    PubMed

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager Iii, Joel W; Chrzan, Daryl C; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth. PMID:26813257

  7. Direct growth of single-crystalline III-V semiconductors on amorphous substrates

    NASA Astrophysics Data System (ADS)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager, Joel W., III; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth.

  8. Dislocation effects in FinFETs for different III-V compound semiconductors

    NASA Astrophysics Data System (ADS)

    Hur, Ji-Hyun; Jeon, Sanghun

    2016-04-01

    While Si-based devices are facing the limits of scaling, III-V materials, having high mobility, have attracted more and more attention. However, their advantages are obtained by ignoring the drawbacks of inevitably present dislocations. In this paper, we present a theoretical model that describes the degradation in carrier mobility caused by these inevitable charged dislocations in nanometer-sized, quantum-confined III-V compound semiconductor fin-shaped field effect transistors. We conclude that the Fermi-level pinning effect needs to be resolved to give carriers high enough energy (Fermi energy in the channel) to effectively ignore Coulomb scattering of charges at dislocations in a channel made by III-V compound semiconductors.

  9. III-V/Si on silicon-on-insulator platform for hybrid nanoelectronics

    SciTech Connect

    Prucnal, Slawomir Zhou, Shengqiang; Ou, Xin; Facsko, Stefan; Oskar Liedke, Maciej; Bregolin, Felipe; Liedke, Bartosz; Grebing, Jochen; Fritzsche, Monika; Hübner, Rene; Mücklich, Arndt; Rebohle, Lars; Skorupa, Wolfgang; Helm, Manfred; Turek, Marcin; Drozdziel, Andrzej

    2014-02-21

    The unique properties of SOI wafers enable the integration of heterogeneous materials with distinct functionalities in different layers. In particular, III-V compound semiconductors are very attractive for low-noise and high-speed electronic and photonic components integrated on a single chip. We have developed a CMOS compatible and fully integrated solution for the integration of III-V compound semiconductors with silicon technology for optoelectronic applications. InAs compound semiconductor nanostructures are synthesized in SOI wafers using the combined ion beam implantation and millisecond liquid-phase epitaxial growth. Optoelectronic and microstructural investigations carried out on implanted, annealed, and selectively etched samples confirm the formation of high-quality III-V compound semiconductor nanostructures.

  10. III-V/Si wafer bonding using transparent, conductive oxide interlayers

    SciTech Connect

    Tamboli, Adele C. Hest, Maikel F. A. M. van; Steiner, Myles A.; Essig, Stephanie; Norman, Andrew G.; Bosco, Nick; Stradins, Paul; Perl, Emmett E.

    2015-06-29

    We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100 °C to 350 °C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 Ω cm{sup 2} for samples bonded at 200 °C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga{sub 0.5}In{sub 0.5}P/Si tandem solar cells operating at 1 sun or low concentration conditions.

  11. Indium Zinc Oxide Mediated Wafer Bonding for III-V/Si Tandem Solar Cells

    SciTech Connect

    Tamboli, Adele C.; Essig, Stephanie; Horowitz, Kelsey A. W.; Woodhouse, Michael; van Hest, Maikel F. A. M.; Norman, Andrew G.; Steiner, Myles A.; Stradins, Paul

    2015-06-14

    Silicon-based tandem solar cells are desirable as a high efficiency, economically viable approach to one sun or low concentration photovoltaics. We present an approach to wafer bonded III-V/Si solar cells using amorphous indium zinc oxide (IZO) as an interlayer. We investigate the impact of a heavily doped III-V contact layer on the electrical and optical properties of bonded test samples, including the predicted impact on tandem cell performance. We present economic modeling which indicates that the path to commercial viability for bonded cells includes developing low-cost III-V growth and reducing constraints on material smoothness. If these challenges can be surmounted, bonded tandems on Si can be cost-competitive with incumbent PV technologies, especially in low concentration, single axis tracking systems.

  12. Methods for forming group III-V arsenide-nitride semiconductor materials

    NASA Technical Reports Server (NTRS)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

    2000-01-01

    Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  13. III-V/Si on silicon-on-insulator platform for hybrid nanoelectronics

    NASA Astrophysics Data System (ADS)

    Prucnal, Slawomir; Zhou, Shengqiang; Ou, Xin; Facsko, Stefan; Oskar Liedke, Maciej; Bregolin, Felipe; Liedke, Bartosz; Grebing, Jochen; Fritzsche, Monika; Hübner, Rene; Mücklich, Arndt; Rebohle, Lars; Helm, Manfred; Turek, Marcin; Drozdziel, Andrzej; Skorupa, Wolfgang

    2014-02-01

    The unique properties of SOI wafers enable the integration of heterogeneous materials with distinct functionalities in different layers. In particular, III-V compound semiconductors are very attractive for low-noise and high-speed electronic and photonic components integrated on a single chip. We have developed a CMOS compatible and fully integrated solution for the integration of III-V compound semiconductors with silicon technology for optoelectronic applications. InAs compound semiconductor nanostructures are synthesized in SOI wafers using the combined ion beam implantation and millisecond liquid-phase epitaxial growth. Optoelectronic and microstructural investigations carried out on implanted, annealed, and selectively etched samples confirm the formation of high-quality III-V compound semiconductor nanostructures.

  14. Relaxation Models of the (110) Zinc-Blende III-V Semiconductor Surfaces: Density Functional Study

    SciTech Connect

    Ye, H.; Chen, G.; Wu, Y.; Zhu, Y.; Wei, S. H.

    2008-11-01

    Clean III-V zinc-blende (110) surfaces are the most extensively studied semiconductor surface. For conventional III-V compounds such as GaAs and InP, the surface relaxation follows a bond rotation relaxation model. However, for III-nitrides recent study indicates that they follow a bond-constricting relaxation model. First-principles atom relaxation calculations are performed to explore the origin of the difference between the two groups of materials. By analyzing the individual shift trends and ionic properties of the top layer anions and cations, we attribute the difference between the conventional and nitride III-V compounds to the strong electronegativity of N, which leads to the s{sup 2}p{sup 3} pyramid bond angle to be larger than the ideal one in bulk (109.5{sup o}). The general trends of the atomic relaxation at the III-nitrides (110) surfaces are explained.

  15. Electronic structure of III-V zinc-blende semiconductors from first principles

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Yin, Haitao; Cao, Ronggen; Zahid, Ferdows; Zhu, Yu; Liu, Lei; Wang, Jian; Guo, Hong

    2013-06-01

    For analyzing quantum transport in semiconductor devices, accurate electronic structures are critical for quantitative predictions. Here we report theoretical analysis of electronic structures of all III-V zinc-blende semiconductor compounds. Our calculations are from density functional theory with the semilocal exchange proposed recently [Tran and Blaha, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.226401 102, 226401 (2009)], within the linear muffin tin orbital scheme. The calculated band gaps and effective masses are compared to experimental data and good quantitative agreement is obtained. Using the theoretical scheme presented here, quantum transport in nanostructures of III-V compounds can be confidently predicted.

  16. Demonstration of a heterogeneously integrated III-V/SOI single wavelength tunable laser.

    PubMed

    Keyvaninia, Shahram; Roelkens, Gunther; Van Thourhout, Dries; Jany, Christophe; Lamponi, Marco; Le Liepvre, Alban; Lelarge, Francois; Make, Dalila; Duan, Guang-Hua; Bordel, Damien; Fedeli, Jean-Marc

    2013-02-11

    A heterogeneously integrated III-V-on-silicon laser is reported, integrating a III-V gain section, a silicon ring resonator for wavelength selection and two silicon Bragg grating reflectors as back and front mirrors. Single wavelength operation with a side mode suppression ratio higher than 45 dB is obtained. An output power up to 10 mW at 20 °C and a thermo-optic wavelength tuning range of 8 nm are achieved. The laser linewidth is found to be 1.7 MHz. PMID:23481834

  17. Precise measurement of charged defects in III-V compounds (2)

    NASA Technical Reports Server (NTRS)

    Soest, J. F.

    1972-01-01

    The main objective of this research is to obtain a calibration of a low concentration of charged defects in some III-V semiconducting compounds. The experimental technique being used is nuclear magnetic resonance (NMR), and the objective is to be attained through a thorough examination of the properties of the NMR lines of the nuclei in the III-V compounds. The properties of the NMR lines, and how they are influenced by the presence of charged defects are studied theoretically and experimentally.

  18. Hybrid III-V on silicon lasers for photonic integrated circuits on silicon

    NASA Astrophysics Data System (ADS)

    Duan, Guang-Hua; Jany, Christophe; Le Liepvre, Alban; Accard, Alain; Lamponi, Marco; Make, Dalila; Kaspar, Peter; Levaufre, Guillaume; Girard, Nils; Lelarge, François; Fedeli, Jean-Marc; Messaoudene, Sonia; Bordel, Damien; Olivier, Segolene

    2014-02-01

    Silicon photonics is attracting large attention due to the promise of fabricating low-cost, compact circuits that integrate photonic and microelectronic elements. It can address a wide range of applications from short distance data communication to long haul optical transmission. Today, practical Si-based light sources are still missing, despite the recent demonstration of an optically pumped germanium laser. This situation has driven research to the heterogeneous integration of III-V semiconductors on silicon through wafer bonding techniques. This paper reports on recent advances on integrated hybrid InP/SOI lasers and transmitters using a wafer bonding technique made in particular at III-V Lab, France.

  19. Materials Integration and Metamorphic Substrate Engineering from Silicon to Gallium Arsenide to Indium Phosphide for Advanced III-V/Silicon Photovoltaics

    NASA Astrophysics Data System (ADS)

    Carlin, Andrew M.

    Lattice-mismatched epitaxy in the III-V compound semiconductor system based on III-AsP and related alloys are of enormous importance, and considerable research interest, for many years. The reason is straightforward if one considers the limitations placed on available materials properties for devices dictated by lattice matching to the dominant substrate technologies - Si, GaAs (and/or Ge) and InP. For III-V epitaxy, the lattice constants of these substrates have defined a generation or more of device advances since growth of heterostructures possessing the same equilibrium lattice constants as the substrate yields essentially defect-free (specifically extended defect-free) materials and devices. Removing the restriction of lattice matching to current substrate technology opens a rich spectrum of bandgaps, bandgap combinations, conduction and valence band offsets, etc., that are desirable and exploitable for advancing device technologies for new functionality and greater performance. However successful exploitation of these properties requires mitigation of a variety of extended defects that result from the lattice mismatch between substrate and epitaxial heterostructures. A well known method to achieve this solution is through the use of compositionally (lattice constant-graded) buffer interlayers, in which the equilibrium lattice constants of interlayers are slowly altered by controlled changes in layer composition so that the mismatch strain between the initial substrate and the final device layers is spread across a thickness of buffer. The research accomplished has yielded success for both lattice constant ranges Si - GaAs and GaAs - InP. For the Si - GaAs system, a three step GaP nucleation process on Si has been developed and demonstrated, which maintains total avoidance of creating coalescence-related defects such as antiphase domains and stacking faults resulting from the initial III-V/IV interfaces while reducing overall threading dislocation density by ~10x, to a range of 1×107 cm-2, compared to current state of the art. This reduction can now enable future III-V/Si solar cells based on GaAsP metamorphic buffers in which the underlying Si substrate can participate as an active sub-cell, and such buffers have been demonstrated in this research. Second, in this same lattice constant range, novel GaP/SiGe interfaces on Si were grown and demonstrated to eliminate the small, but not negligible lattice misfit between GaP and Si, and provides a second pathway for future III-V/Si solar cell integration through subsequent metamorphic buffer growth. For the GaAs-InP range of lattice constants, multiple metamorphic buffer strategies, including those based on anion-specific quaternary GaInAsP, combinations of step and linearly-graded buffers, and buffers with multiple ternary alloys were all investigated. Micro-scale phase separation within quaternary anion-graded GaInAsP was identified as a mechanism to significantly inhibit proper lattice misfit strain relaxation, which was explained by thermodynamic arguments consistent with theoretical phase separation. This led to the creation of hybrid step and linearly graded InGaAs/InGaP metamorphic buffers through which phase separation was totally eliminated by avoiding specific compositions that were identified as sources for phase separation. These findings have enabled a realistic path for accessing the full range of bandgaps needed for future high efficiency III-V solar cells through optimized metamorphic III-V grading strategies.

  20. Monolithic III-V on Silicon Plasmonic Nanolaser Structure for Optical Interconnects

    NASA Astrophysics Data System (ADS)

    Li, Ning; Liu, Ke; Sorger, Volker J.; Sadana, Devendra K.

    2015-09-01

    Monolithic integration of III-V semiconductor lasers with Si circuits can reduce cost and enhance performance for optical interconnects dramatically. We propose and investigate plasmonic III-V nanolasers as monolithically integrated light source on Si chips due to many advantages. First, these III-V plasmonic light sources can be directly grown on Si substrates free of crystallographic defects due to the submicron cavity footprint (250 nm × 250 nm) being smaller than the average defect free region size of the heteroepitaxial III-V material on Si. Secondly, the small lateral and vertical dimensions facilitate process co-integration with Si complementary metal-oxide-semiconductor (CMOS) in the front end of the line. Thirdly, combining with monolithically integrated CMOS circuits with low device capacitance and parasitic capacitance, the nano-cavity optoelectronic devices consume orders of magnitude less power than the conventional lasers and reduce the energy consumption. Fourthly, the modulation bandwidth of the plasmonic light-sources is enhanced to significantly higher than conventional lasers due to enhanced photon state density and transition rate. In addition, we show that these device performance are very robust after taking into account the surface recombination and variations in device fabrication processes.

  1. Heterointegration of III-V on silicon using a crystalline oxide buffer layer

    NASA Astrophysics Data System (ADS)

    Bhatnagar, K.; Rojas-Ramirez, J. S.; Contreras-Guerrero, R.; Caro, M.; Droopad, R.

    2015-09-01

    The integration of III-V compound semiconductors with Si can combine the cost advantage and maturity of Si technology with the superior performance of III-V materials. We have achieved the heteroepitaxial growth of III-V compound semiconductors on a crystalline SrTiO3 buffer layer grown on Si(0 0 1) substrates. A two-step growth process utilizing a high temperature nucleation layer of GaAs, followed by a low-temperature GaAs layer at a higher growth rate was employed to achieve highly crystalline thick GaAs layers on the SrTiO3/Si substrates with low surface roughness as seen by AFM. The effect of the GaAs nucleation layer on different surface terminations for the SrTiO3 layer was studied for both on axis and miscut wafers, which led to the conclusion that the Sr terminated surface on miscut substrates provides the best GaAs films. Using GaAs/STO/Si as virtual substrates, we have optimized the growth of high quality GaSb using the interfacial misfit (IMF) dislocation array technique. This work can lead to the possibility of realizing infrared detectors and next-generation high mobility III-V CMOS within the existing Si substrate infrastructure.

  2. Monolithic III-V on Silicon Plasmonic Nanolaser Structure for Optical Interconnects.

    PubMed

    Li, Ning; Liu, Ke; Sorger, Volker J; Sadana, Devendra K

    2015-01-01

    Monolithic integration of III-V semiconductor lasers with Si circuits can reduce cost and enhance performance for optical interconnects dramatically. We propose and investigate plasmonic III-V nanolasers as monolithically integrated light source on Si chips due to many advantages. First, these III-V plasmonic light sources can be directly grown on Si substrates free of crystallographic defects due to the submicron cavity footprint (250 nm × 250 nm) being smaller than the average defect free region size of the heteroepitaxial III-V material on Si. Secondly, the small lateral and vertical dimensions facilitate process co-integration with Si complementary metal-oxide-semiconductor (CMOS) in the front end of the line. Thirdly, combining with monolithically integrated CMOS circuits with low device capacitance and parasitic capacitance, the nano-cavity optoelectronic devices consume orders of magnitude less power than the conventional lasers and reduce the energy consumption. Fourthly, the modulation bandwidth of the plasmonic light-sources is enhanced to significantly higher than conventional lasers due to enhanced photon state density and transition rate. In addition, we show that these device performance are very robust after taking into account the surface recombination and variations in device fabrication processes. PMID:26369698

  3. Design, fabrication and demonstration of heterogeneously III-V/Si laser with a compact optical vertical interconnect access

    NASA Astrophysics Data System (ADS)

    Pu, Jing; Ng, Doris Keh Ting; Lim, Kim Peng; Krishnamurthy, Vivek; Lee, Chee Wei; Tang, Kun; Kay, Anthony, Yew Seng; Loh, Ter Hoe; Wang, Qian

    2015-02-01

    A new heterogeneously integrated III-V/Si laser structure is reported in this letter, which consists of a III-V ridge waveguide gain section on silicon, III-V/Si optical vertical interconnect accesses (VIAs) and silicon-oninsulator (SOI) nanophotonic waveguide sections. The III-V semiconductor layers are introduced on top of the 300 nm thick SOI layer through low temperature, plasma assisted direct wafer-bonding and etched to form III-V ridge waveguide on silicon as the gain section. The optical VIA is formed by tapering the III-V and the beneath SOI in the same direction with a length of 50 μm for efficient coupling of light down to the 600 nm wide silicon nanophotonic waveguide or vice versa. Fabrication details and specification characterizations of this heterogeneous III-V/Si Fabry-Pérot (FP) laser are given. The fabricated FP laser shows a continuous-wave lasing with a threshold current of 65 mA at room temperature and the slope efficiency from single facet is 144 mW/A. The maximal single facet emitting power is about 4.5 mW at a current of 100 mA and the side-mode suppression ratio is ~30 dB. This new heterogeneously integrated III-V/Si laser structure demonstrated enables more complex laser configuration with a sub-system on-chip for various applications.

  4. Thin multi-junction solar cells of III-V materials to advance solar energy harvesting

    NASA Astrophysics Data System (ADS)

    Castelletto, S.; Parker, A.

    2013-09-01

    Significant advancements in photovoltaic solar cells are required to support large-scale energy demands with solar power. The first generation of solar cells (SC) available today uses Si. While Si is highly abundant and these types of SC can be easily manufactured, the best power conversion efficiency is only 24%. Developing photovoltaic SC using III-V materials may increase the efficiency while decreasing the manufacturing costs associated with cell fabrication. This paper studies the opportunity to improve two-junctions solar cells made of III-V materials by making the layers very thin and including the antireflective layer in the first junction. In terms of light harvesting, the anti-reflective layer made of a semiconductor is shown to absorb the most part of the incident light.

  5. Efficient n-type doping of zinc-blende III-V semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Besteiro, Lucas V.; Tortajada, Luis; Souto, J.; Gallego, L. J.; Chelikowsky, James R.; Alemany, M. M. G.

    2014-03-01

    We demonstrate that it is preferable to dope III-V semiconductor nanowires by n-type anion substitution as opposed to cation substitution. Specifically, we show the dopability of zinc-blende nanowires is more efficient when the dopants are placed at the anion site as quantified by formation energies and the stabilization of DX-like defect centers. The comparison with previous work on n - type III-V semiconductor nanocrystals also allows to determine the role of dimensionality and quantum confinement on doping characteristics of materials. Our results are based on first-principles calculations of InP nanowires by using the PARSEC code. Work supported by the Spanish MICINN (FIS2012-33126) and Xunta de Galicia (GPC2013-043) in conjunction with FEDER. JRC acknowledges support from DoE (DE-FG02-06ER46286 and DESC0008877). Computational support was provided in part by CESGA.

  6. MBE growth technology for high quality strained III-V layers

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)

    1992-01-01

    III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).

  7. MBE growth technology for high quality strained III-V layers

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)

    1990-01-01

    The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3).

  8. The Physics of III-V Heterojunction Devices in Wireless Communications

    NASA Astrophysics Data System (ADS)

    Johnson, Karl

    2003-03-01

    III-V heterojunction devices have become pervasive in wireless communication appliances. In particular, the low voltage, high efficiency power amplifier transmitters in cellular phones are dominated by heterojunction bipolar transistors (HBT), psuedomorphic high electron mobility transistors (pHEMT) and heterojunction field effect transistors (HFET). Further, these III-V heterojunction devices are also appearing in infrastructure applications such as cellular base stations, wireless local area network (WLAN) and cable television (CATV) line amplifiers. The design of these devices requires unique band gap engineering in order to meet the cost, performance and ruggedness in the linear and saturated power modes required by today's cellular modulation protocols. This presentation will address the physics behind the design, development and operation of these technologies leading to their optimization for the wireless market place.

  9. To the understanding of the formation of the droplet-epitaxial III-V based nanostructures

    SciTech Connect

    Nemcsics, Ákos

    2014-05-15

    In this work, we discuss the evolution of the self-assembling III-V based nanostructures. These nano-structures were prepared by droplet epitaxial technique. The different nanostructures such as quantum dot, quantum ring, double quantum ring, or nanohole form similarly from an initial Ga droplet but under different substrate temperature and various arsenic pressures. Started from few atomic courses, we give here a qualitative description of the key processes for all of the aforementioned nanostructures.

  10. Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

  11. Electrically driven hybrid Si/III-V Fabry-Prot lasers based on adiabatic mode transformers.

    PubMed

    Ben Bakir, B; Descos, A; Olivier, N; Bordel, D; Grosse, P; Augendre, E; Fulbert, L; Fedeli, J M

    2011-05-23

    We report the first demonstration of an electrically driven hybrid silicon/III-V laser based on adiabatic mode transformers. The hybrid structure is formed by two vertically superimposed waveguides separated by a 100-nm-thick SiO2 layer. The top waveguide, fabricated in an InP/InGaAsP-based heterostructure, serves to provide optical gain. The bottom Si-waveguides system, which supports all optical functions, is constituted by two tapered rib-waveguides (mode transformers), two distributed Bragg reflectors (DBRs) and a surface-grating coupler. The supermodes of this hybrid structure are controlled by an appropriate design of the tapers located at the edges of the gain region. In the middle part of the device almost all the field resides in the III-V waveguide so that the optical mode experiences maximal gain, while in regions near the III-V facets, mode transformers ensure an efficient transfer of the power flow towards Si-waveguides. The investigated device operates under quasi-continuous wave regime. The room temperature threshold current is 100 mA, the side-mode suppression ratio is as high as 20 dB, and the fiber-coupled output power is ~7 mW. PMID:21643289

  12. High mobility CMOS technologies using III-V/Ge channels on Si platform

    NASA Astrophysics Data System (ADS)

    Takagi, S.; Kim, S.-H.; Yokoyama, M.; Zhang, R.; Taoka, N.; Urabe, Y.; Yasuda, T.; Yamada, H.; Ichikawa, O.; Fukuhara, N.; Hata, M.; Takenaka, M.

    2013-10-01

    MOSFETs using channel materials with high mobility and low effective mass have been regarded as strongly important for obtaining high current drive and low supply voltage CMOS under sub 10 nm regime. From this viewpoint, attentions have recently been paid to Ge and III-V channels. In this paper, possible solutions for realizing III-V/Ge MOSFETs on the Si platform are presented. The high quality III-V channel formation on Si substrates can be realized through direct wafer bonding. The gate stack formation is constructed on a basis of atomic layer deposition (ALD) Al2O3 gate insulators for both InGaAs and Ge MOSFETs. As the source/drain (S/D) formation, Ni-based metal S/D is implemented for both InGaAs and Ge MOSFETs. By combining these technologies, we demonstrate successful integration of InGaAs-OI nMOSFETs and Ge p-MOSFETs on a same wafer and their superior device performance.

  13. Present Status in the Development of III-V Multi-Junction Solar Cells

    NASA Astrophysics Data System (ADS)

    Philipps, Simon P.; Guter, Wolfgang; Welser, Elke; Schöne, Jan; Steiner, Marc; Dimroth, Frank; Bett, Andreas W.

    During the last yearshigh-concentration photovoltaics (HCPV) technology has gained growing attention. Excellent operatingAC-system efficiencies of up to 25% have been reported. One of the driving forces for this high system efficiency has been the continuous improvement of III-V multi-junction solar cell efficiencies. In consequence, the demand for these solar cells has risen, and strong efforts are undertaken to further increase the solar cell efficiency as well as the volume of cell output. The production capacity for multi-junction solar cells does not constitute a limitation. Already now several tens of MWp per year can be produced and the capacities can easily be increased. The state-of-the art approach for highly efficient photovoltaic energy conversion is marked by the Ga0.50In0.50P/Ga0.99In0.01As/Ge structure. This photovoltaic device is today well established in space applications and recently has entered the terrestrial market. The following chapter presents an overview about the present research status in III-V multi-junction solar cells at Fraunhofer ISE regarding cell design, expected performance, numerical simulation tools, adaptation of devices to different incident spectra and the fabrication of these devices. Finally, an outlook on future developments of III-V multi-junction solar cells is given.

  14. Natural interface states in coherent and isovalent III-V heterostructures

    NASA Astrophysics Data System (ADS)

    Popescu, Voicu; Zunger, Alex

    2011-03-01

    Interface states occur in semiconductor heterojunctions whenever a significant perturbation is present, caused by interface defects, lattice mismatch, discontinuities in the effective mass or sharp variations in the potential across the interface. We discuss the natural interface states appearing in perfectly coherent and isovalent III-V heterojunctions when a ? -well and an X -anti-well coexist in the conduction band. We use empirical pseudopotential calculation to illustrate this type of states for a few III-V heterostructures. For InP/GaP the interface localised states lie energetically in the band-gap and possess, because of their mixed ? - X character, a strong optical signature. This allows us to provide a different interpretation of the photoemission data existent in the literature for InP/GaP quantum wells and dots. We further discuss the presence of the interface localised states in other III-V heterojunctions, investigating the conditions under which they might be experimentally observed. Funded by DOE, EFRC for Inverse Design, NREL Subcontract XGC-0-40445-01.

  15. Structural characterization of II-VI and III-V compound semiconductor heterostructures and superlattices

    NASA Astrophysics Data System (ADS)

    Ouyang, Lu

    The research described in this dissertation has involved the use of transmission electron microcopy (TEM) to characterize the structural properties of II-VI and III-V compound semiconductor heterostructures and superlattices. The microstructure of thick ZnTe epilayers (˜2.4 microm) grown by molecular beam epitaxy (MBE) under virtually identical conditions on GaSb, InAs, InP and GaAs (100) substrates were compared using TEM. High-resolution electron micrographs revealed a highly coherent interface for the ZnTe/GaSb sample, and showed extensive areas with well-separated interfacial misfit dislocations for the ZnTe/InAs sample. Lomer edge dislocations and 60° dislocations were commonly observed at the interfaces of the ZnTe/InP and ZnTe/GaAs samples. The amount of residual strain at the interfaces was estimated to be 0.01% for the ZnTe/InP sample and -0.09% for the ZnTe/GaAs sample. Strong PL spectra for all ZnTe samples were observed from 80 to 300 K. High quality GaSb grown by MBE on ZnTe/GaSb (001) virtual substrates with a temperature ramp at the beginning of the GaSb growth has been demonstrated. High-resolution X-ray diffraction (XRD) showed clear Pendellosung thickness fringes from both GaSb and ZnTe epilayers. Cross-section TEM images showed excellent crystallinity and smooth morphology for both ZnTe/GaSb and GaSb/ZnTe interfaces. Plan-view TEM image revealed the presence of Lomer dislocations at the interfaces and threading dislocations in the top GaSb layer. The defect density was estimated to be ˜1 x107/cm2. The PL spectra showed improved optical properties when using the GaSb transition layer grown on ZnTe with a temperature ramp. The structural properties of strain-balanced InAs/InAs1-xSb x SLs grown on GaSb (001) substrates by metalorganic chemical vapor deposition (MOCVD) and MBE, have been studied using XRD and TEM. Excellent structural quality of the InAs/InAs1-xSbx SLs grown by MOCVD has been demonstrated. Well-defined ordered-alloy structures within individual InAs1-xSbx layers were observed for samples grown by modulated MBE. However, the ordering disappeared when defects propagating through the SL layers appeared during growth. For samples grown by conventional MBE, high-resolution images revealed that interfaces for InAs 1-xSbx grown on InAs layers were sharper than for InAs grown on InAs1-xSbx layers, most likely due to a Sb surfactant segregation effect.

  16. Fatigue failure of concentrator III-V solar cells - Does forward bias current injection really kill III-V CPV cells?

    NASA Astrophysics Data System (ADS)

    Araki, Kenji; Nagai, Hirokazu; Tamura, Kazuyuki

    2012-10-01

    CPV cells are successively exposed by cycles of concentrated sunlight and huge cycling current flows out of contacts. The purpose of this research is to identify if the fatigue will be one of the life-end and wearing modes of CPV cells and how long the life-time will be. One of the best ways of giving cycling stress on cells and contacts is cycling forward bias injection. First, it is important to investigate if forward bias itself damages concentrator III-V cells. To confirm the forward bias current itself does not damage the CPV solar cells but cycling does, we applied 4 times of Isc continuously in 500 hours, equivalently total injection of 90,000 cycles, but no damage or degradation was observed. What's more, we applied the cycling test after the stress of 500 hour continuous forward bias injection. We did not identify any changes between groups of with stress of continuous forward bias and without them. On-Off tests giving forward bias current as high as 4 times of Isc are conducted. The failure was analyzed by the Weible function. About 2,000 cells in total were examined. A small number of initial failure, that of failure number of cycles lied along exponential distribution and distinct portion of wear mode failure that of failure number of cycles lied along Gaussian distribution were identified. The EL measurement indicated that all the damaged cells in wear mode were local shunt under the top contacts suggesting stress under the top contacts would be possibly responsible to the fatigue failure. Advanced contact design that leads to reduce the stress on the top contact is expected to prolong the lifetime of the III-V concentrator cells.

  17. Monte Carlo analysis of the dynamic behavior of III-V MOSFETs for low-noise RF applications

    NASA Astrophysics Data System (ADS)

    Shi, Ming; Saint-Martin, Jérôme; Bournel, Arnaud; Querlioz, Damien; Wichmann, Nicolas; Bollaert, Sylvain; Danneville, François; Dollfus, Philippe

    2013-09-01

    III-V Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) with a high-κ dielectric gate stack are investigated as a possible route to enhance the performance of either microwave or logic circuits with low supply voltage (VDD). The intrinsic performance of III-V MOSFETs in both static and dynamic regimes under low VDD is estimated using device Monte Carlo simulation. The characteristics of a Bulk-like and XOI-like III-V MOSFETs are quantitatively assessed and compared in terms of DC transconductance, high frequency performance and noise behavior. Finally, the comparison with Si-based devices shows the potential of III-V nano-MOSFET architectures for high-frequency and low noise application under low operating power.

  18. III-V compound semiconductors for mass-produced nano-electronics: theoretical studies on mobility degradation by dislocation.

    PubMed

    Hur, Ji-Hyun; Jeon, Sanghun

    2016-01-01

    As silicon-based electronics approach the limit of scaling for increasing the performance and chip density, III-V compound semiconductors have started to attract significant attention owing to their high carrier mobility. However, the mobility benefits of III-V compounds are too easily accepted, ignoring a harmful effect of unavoidable threading dislocations that could fundamentally limit the applicability of these materials in nanometer-scale electronics. In this paper, we present a theoretical model that describes the degradation of carrier mobility by charged dislocations in quantum-confined III-V semiconductor metal oxide field effect transistors (MOSFETs). Based on the results, we conclude that in order for III-V compound MOSFETs to outperform silicon MOSFETs, Fermi level pinning in the channel should be eliminated for yielding carriers with high injection velocity. PMID:26911249

  19. Performance and Reliability of Multijunction III-V Modules for Concentrator Dish and Central Receiver Applications

    SciTech Connect

    Verlinden, P. J.; Lewandowski, A.; Bingham, C.; Kinsey, G. S.; Sherif, R. A.; Laisch, J. B.

    2006-01-01

    Over the last 15 years, Solar Systems have developed a dense array receiver PV technology for 500X concentrator reflective dish applications. This concentrator PV technology has been successfully deployed at six different locations in Australia, counting for more than 1 MWp of installed peak power. A new Multijunction III-V receiver to replace the current silicon Point-Contact solar cells has recently been developed. The new receiver technology is based on high-efficiency (>32%) Concentrator Ultra Triple Junction (CUTJ) solar cells from Spectrolab, resulting in system power and energy performance improvement of more than 50% compared to the silicon cells. The 0.235 m{sup 2} concentrator PV receiver, designed for continuous 500X operation, is composed of 64 dense array modules, and made of series and parallel-connected solar cells, totaling approximately 1,500 cells. The individual dense array modules have been tested under high intensity pulsed light, as well as with concentrated sunlight at the Solar Systems research facility and at the National Renewable Energy Laboratory's High Flux Solar Furnace. The efficiency of the dense array modules ranges from 30% to 36% at 500X (50 W/cm{sup 2}, AM1.5D low AOD, 21C). The temperature coefficients for power, voltage and current, as well as the influence of Air Mass on the cell responsivity, were measured. The reliability of the dense array multijunction III-V modules has been studied with accelerated aging tests, such as thermal cycling, damp heat and high-temperature soak, and with real-life high-intensity exposure. The first 33 kWp multijunction III-V receiver was recently installed in a Solar Systems dish and tested in real-life 500X concentrated sunlight conditions. Receiver efficiencies of 30.3% and 29.0% were measured at Standard Operating Conditions and Normal Operating Conditions respectively.

  20. Quantitative high resolution electron microscopy of III-V compounds: A fuzzy logic approach

    NASA Astrophysics Data System (ADS)

    Hillebrand, R.; Hofmeister, H.; Werner, P.; Gösele, U.

    1995-09-01

    In the study of interdiffusion phenomena in layered structures of III-V compounds by high resolution electron microscopy, contrast features in the micrographs can be correlated with the variation of the chemical composition of the crystals. For quantitative interpretation of the micrographs a fuzzy logic approach is adapted to extract chemical information. The linguistic variable ``similarity of images'' is derived from the standard deviation (SD) of their difference patterns, which proved to be an appropriate measure. The approach developed is used to analyze simulated contrast tableaus of GaAs/P (As/P variation) and experimental micrographs of Al/GaAs (Al/Ga variation).

  1. Lattice-Mismatched Approaches for High-Performance, III-V Photovoltaic Energy Converters

    SciTech Connect

    Wanlass, M. W.; Ahrenkiel, S. P.; Ahrenkiel, R. K.; Albin, D. S.; Carapella, J. J.; Duda, A.; Geisz, J. F.; Kurtz, S.; Moriarty, T.; Wehrer, R. J.; Wernsman, B.

    2005-02-01

    We discuss lattice-mismatched (LMM) approaches using compositionally step-graded layers and buffer layers that yield III-V photovoltaic devices with performance parameters equaling those of similar lattice-matched (LM) devices. Our progress in developing high-performance, LMM, InP-based GaInAs/InAsP materials and devices for thermophotovoltaic (TPV) energy conversion is highlighted. A novel, monolithic, multi-bandgap, tandem device for solar PV (SPV) conversion involving LMM materials is also presented, along with promising preliminary performance results.

  2. Solid-state lighting : the III-V Epi Killer App.

    SciTech Connect

    Tsao, Jeffrey Yeenien

    2010-06-01

    Throughout its history, lighting technology has made tremendous progress: the efficiency with which power is converted into usable light has increased 2.8 orders of magnitude over three centuries. This progress has, in turn, fueled large increases in the consumption of light and productivity of human society. In this talk, we review an emerging new technology, solid-state lighting: its frontier performance potential; the underlying advances in physics and materials that might enable this performance potential; the resulting energy consumption and human productivity benefits; and the impact on worldwide III-V epi manufacture.

  3. Electronic Structure and Valence of Mn impurities in III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Schulthess, Thomas C.

    2003-11-01

    Mn doped III-V semiconductors have recently become very popular materials since they are ferromagnetic at reasonably high temperatures and in some cases show carrier induced magnetism, where the Curie temperature can be altered by changes in the carrier concentration. It is expected that these materials will play an important role in Spintronics devices. Substitutional Mn impurities in III-V semiconductors can acquire either a divalent or a trivalent configuration. For example, it is generally accepted that Mn in GaAs is in a (d^5+h) configuration with five occupied Mn d-orbitals and a delocalized hole in the valence band. In contrast, Mn in GaN is believed to be in a d^4 configuration with a deep impurity state that has d-character. But there have recently been some discussions about the possibility of having some Mn ion in GaN assuming a divalent (d^5+h) type configuration. In order to achieve carrier induced ferromagnetism, the desired state of the Mn ions in III-V semiconductors is the (d^5+h) configuration. We have therefore performed ab-initio calculations of the Mn valence when it substitutes Ga in various III-V semiconductor hosts. We use the self-interaction corrected local spin density (SIC-LSD) method which is able to treat localized impurity orbitals properly. In particular we find that the method is capable of predicting the (d^5+h) state of Mn in GaAs. For Mn in GaP and GaN the calculations predict a trivalent d^4 state in the idealized system. The energy differences between d^4 and (d^5+h) configurations in GaP are, however, very small. Introduction of defects or donors does change the valence of Mn in GaP, favoring the divalent state under certain circumstances. Work done in collaboration with W. Temmerman and S. Szotek, Daresbury Laboratory, G. M. Stocks, ORNL, and W. H. Butler, MINT Center University of Alabama. This work supported by the Defense Advanced Research Agency and by DOE Office of Science trough ASCR/MICS and BES/DMSE under Contract No. DE-AC05-00OR22725 with UT-Battelle LLC.

  4. Extraction of interface state density in oxide/III-V gate stacks

    NASA Astrophysics Data System (ADS)

    Veksler, D.; Bersuker, G.; Madan, H.; Morassi, L.; Verzellesi, G.

    2015-06-01

    Extracted interface trap densities (Dit) in the oxide/III-V gate stacks vary strongly with the utilized measurement procedures and values of device parameters used in the extraction analysis. Such Dit dependency on both selected procedures and parameters compromises unambiguous extraction of energy distributions of defects affecting device characteristics. To overcome this uncertainty, we propose an extraction approach, which combines the essential features of the high-low method and Terman method, allowing us to self-consistently determine Dit distribution along with values of the critical device parameters, effective oxide thickness (EOT) and substrate doping density (Nd).

  5. III-V site-controlled quantum dots on Si patterned by nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Pozzato, A.; Tormen, M.; Zannier, V.; Biasiol, G.

    2016-03-01

    We have successfully grown regular arrays of InAs/GaAs quantum dots on patterned Si substrates. Thanks to the capability of nanoimprint lithography, we were able to obtain uniform patterns extended over some cm2 areas, with periods of 300 nm. Ex-situ and in-situ treatments of the surface allowed us to completely remove any residual oxides prior to growth without the use of hydrogen beams, at temperatures compatible with standard III-V molecular beam epitaxy. The growth protocol was optimized in order to obtain a perfect selectivity of InAs/GaAs nanostructures in the holes, without any deposition on the planar areas.

  6. Fabrication of III-V compound nanowires via hot embossing nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Tang, An-Chieh; He, Shi-Yuan; Lee, Ming-Kwei

    2016-03-01

    In this study, the nanoimprint lithography (NIL) technique used to fabricate III-V compound nanowires was investigated. A silicon mold and thermoplastic polymer mr-I 7010R were used for hot embossing nanoimprint lithography. The mold was patterned by e-beam lithography with two masks exposed with different dosages to reduce the proximity effect. The filling capability and residual layer thickness of the thermoplastic polymer were optimized at the embossing temperature of 125 °C. A 73 nm GaAs nanowire was obtained by the mold coated with an antisticking layer.

  7. Empirical modeling of the cross section of damage formation in ion implanted III-V semiconductors

    SciTech Connect

    Wendler, E.; Wendler, L.

    2012-05-07

    In this letter, the cross section of damage formation per individual ion is measured for III-V compound semiconductors ion implanted at 15 K, applying Rutherford backscattering spectrometry. An empirical model is proposed that explains the measured cross sections in terms of quantities representing the primary energies deposited in the displacement of lattice atoms and in electronic interactions. The resulting formula allows the prediction of damage formation for low temperatures and low ion fluences in these materials and can be taken as a starting point for further quantitative modeling of damage formation including secondary effects such as temperature and ion flux.

  8. Microscopic study of the hydrogen diffusion in III-V semiconductors

    SciTech Connect

    Burchard, A.; Deicher, M.; Knopf, M.; Stoetzler, A.; Forkel-Wirth, D.; Fedoseyev, V.N.; Mishin, V.I.

    1998-12-31

    The authors report on experiments which observe on a microscopic scale the migration of isolated hydrogen in InP, GaAs, and InAs. Using the radioactive acceptor {sup 117}Cd, Cd-H pairs have been formed in these III-V semiconductors. After the decay of {sup 117}Cd to {sup 117}In, H is no longer bound to an acceptor and can diffuse freely. This diffusion has been observed by perturbed {gamma}{gamma} angular correlation (PAC) spectroscopy. At 10 K, the occupation of two different lattice sites by hydrogen has been observed. First results on the diffusion of hydrogen will be discussed.

  9. Progress in the Development of Metamorphic Multi-Junction III-V Space-Solar Cells at Essential Research Incorporated

    NASA Technical Reports Server (NTRS)

    Sinharoy, Samar; Patton, Martin O.; Valko, Thomas M., Sr.; Weizer, Victor G.

    2002-01-01

    Theoretical calculations have shown that highest efficiency III-V multi-junction solar cells require alloy structures that cannot be grown on a lattice-matched substrate. Ever since the first demonstration of high efficiency metamorphic single junction 1.1 eV and 1.2 eV InGaAs solar cells by Essential Research Incorporated (ERI), interest has grown in the development of multi-junction cells of this type using graded buffer layer technology. ERI is currently developing a dual-junction 1.6 eV InGaP/1.1 eV InGaAs tandem cell (projected practical air-mass zero (AM0), one-sun efficiency of 28%, and 100-sun efficiency of 37.5%) under a Ballistic Missile Defense Command (BMDO) SBIR Phase II program. A second ongoing research effort at ERI involves the development of a 2.1 eV AlGaInP/1.6 eV InGaAsP/1.2 eV InGaAs triple-junction concentrator tandem cell (projected practical AM0 efficiency of 36.5% under 100 suns) under a SBIR Phase II program funded by the Air Force. We are in the process of optimizing the dual-junction cell performance. In case of the triple-junction cell, we have developed the bottom and the middle cell, and are in the process of developing the layer structures needed for the top cell. A progress report is presented in this paper.

  10. III-V/Si hybrid photonic devices by direct fusion bonding

    PubMed Central

    Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

    2012-01-01

    Monolithic integration of III-V compound semiconductors on silicon is highly sought after for high-speed, low-power-consumption silicon photonics and low-cost, light-weight photovoltaics. Here we present a GaAs/Si direct fusion bonding technique to provide highly conductive and transparent heterojunctions by heterointerfacial band engineering in relation to doping concentrations. Metal- and oxide-free GaAs/Si ohmic heterojunctions have been formed at 300°C; sufficiently low to inhibit active material degradation. We have demonstrated 1.3 μm InAs/GaAs quantum dot lasers on Si substrates with the lowest threshold current density of any laser on Si to date, and AlGaAs/Si dual-junction solar cells, by p-GaAs/p-Si and p-GaAs/n-Si bonding, respectively. Our direct semiconductor bonding technique opens up a new pathway for realizing ultrahigh efficiency multijunction solar cells with ideal bandgap combinations that are free from lattice-match restrictions required in conventional heteroepitaxy, as well as enabling the creation of novel high performance and practical optoelectronic devices by III-V/Si hybrid integration. PMID:22470842

  11. III-V/Si hybrid photonic devices by direct fusion bonding.

    PubMed

    Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

    2012-01-01

    Monolithic integration of III-V compound semiconductors on silicon is highly sought after for high-speed, low-power-consumption silicon photonics and low-cost, light-weight photovoltaics. Here we present a GaAs/Si direct fusion bonding technique to provide highly conductive and transparent heterojunctions by heterointerfacial band engineering in relation to doping concentrations. Metal- and oxide-free GaAs/Si ohmic heterojunctions have been formed at 300°C; sufficiently low to inhibit active material degradation. We have demonstrated 1.3 μm InAs/GaAs quantum dot lasers on Si substrates with the lowest threshold current density of any laser on Si to date, and AlGaAs/Si dual-junction solar cells, by p-GaAs/p-Si and p-GaAs/n-Si bonding, respectively. Our direct semiconductor bonding technique opens up a new pathway for realizing ultrahigh efficiency multijunction solar cells with ideal bandgap combinations that are free from lattice-match restrictions required in conventional heteroepitaxy, as well as enabling the creation of novel high performance and practical optoelectronic devices by III-V/Si hybrid integration. PMID:22470842

  12. Analysis and Control of III-V-MOVPE by Real Time Reflectance Anisotropy and Spectroscopic Ellipsometry

    NASA Astrophysics Data System (ADS)

    Richter, Wolfgang

    1998-03-01

    Among the optical in-situ techniques for epitaxial growth analysis Reflectance Anisotropy Spectroscopy (RAS) and Spectroscopic Ellispsometry (SE) offer large advantages as far as sensitivity, reproducibility and speed of measurement are concerned. While RAS due to its high surface sensitivity directly gives information on structural symmetry and chemical bonding within the surface, SE turns out to be outstanding for analysis of layer thickness and bulk composition. They both together give a rather complete picture of the growth process and can be moreover utilized to compare the different growth techniques (MBE, CBE, MOVPE). Examples presented from III-V-semiconductor epitaxy include fingerprint spectra of stabilized surfaces, monolayer oscillations of growing surfaces, signatures during interface formation and feed-back controlled growth of lattice matched ternary III-V's (InGaAs/InP, InGaP/GaAs). The optical response to surface morphology is discussed within the Stranski-Krastanov growth mode of quantum dots. Finally, specific challenges occuring in commercial growth environments such as rotating and wobbling samples will be discussed. with respect to system design.

  13. Improved adhesion of photoresist to III-V substrates using PECVD carbon films

    NASA Astrophysics Data System (ADS)

    Mancini, David P.; Smith, Steven M.; Hooper, Andrew F.; Talin, A.; Chang, Daniel; Resnick, Douglas J.; Voight, Steven A.

    2002-07-01

    Amorphous PECVD carbon films have been investigated as a means to prepare III-V compound semiconductor substrates for improved photoresist adhesion. Results show that significant improvements in adhesive durability of patterned photoresist occurred for carbon primed GaAs and InGaAs wafers used in conjunction with both i-line and DUV lithography processes. These carbon layers, were 50-100 Angstrom in thickness, and varied in composition and morphology from a nitrogen-doped, diamond-like material (DLC), to a more hydrogen rich, polymer-like material (PLC). Adhesion durability tests performed in baths of ammonium hydroxide (NH4OH) and hydrochloric acid (HCl) in general showed superior performance compared to non-primed substrates. The sole exception was a failure of PLC priming on GaAs wafers used with a DUV anti-reflective coating. This same system, however, was shown to work extremely well when a DLC coating was substituted. Characterization of PLC and DLC films included use of AES, XPS, FTIR, AFM, and contact angle analysis. Results indicate that carbon films passivate III-V oxides, creating a stable, hydrophobic surface. This factor is proposed as a key reason for the improved resistance to aggressive aqueous environments. AFM results show that carbon films are extremely smooth and actually decrease surface roughness, indicating that mechanical adhesion is unlikely.

  14. Theoretical discovery of stable structures of group III-V monolayers: The materials for semiconductor devices

    SciTech Connect

    Suzuki, Tatsuo

    2015-11-23

    Group III-V compounds are very important as the materials of semiconductor devices. Stable structures of the monolayers of group III-V binary compounds have been discovered by using first-principles calculations. The primitive unit cell of the discovered structures is a rectangle, which includes four group-III atoms and four group-V atoms. A group-III atom and its three nearest-neighbor group-V atoms are placed on the same plane; however, these connections are not the sp{sup 2} hybridization. The bond angles around the group-V atoms are less than the bond angle of sp{sup 3} hybridization. The discovered structure of GaP is an indirect transition semiconductor, while the discovered structures of GaAs, InP, and InAs are direct transition semiconductors. Therefore, the discovered structures of these compounds have the potential of the materials for semiconductor devices, for example, water splitting photocatalysts. The discovered structures may become the most stable structures of monolayers which consist of other materials.

  15. III-V nitrides and performance of graphene on copper plasmonic biosensor

    NASA Astrophysics Data System (ADS)

    Mohanty, Goutam; Sahoo, Bijaya Kumar

    2016-05-01

    In the present study, the influence of iii-v nitrides as well as Ge and Si on the sensitivity and performance of a graphene protected copper plasmonic biosensor has been investigated. These semiconductors have been used between copper (Cu) and graphene layers on a SF 10 glass prism. The sensitivity and performance of the biosensor has been computed for with and without semiconductors. III-V nitrides demonstrated high sensitivity and high figure of merit (FOM) in comparison to Si and Ge due to their superior electronic and optical properties. The enhancement of evanescent electric field due to Si, Ge, AlN, GaN and InN have been computed and found highest enhancement for InN. This happens due to high refractive index of InN than other semiconductors. Analysis shows that for a high sensitive imaging biosensor the required optimal thickness of copper, InN and graphene are respectively 32 nm, 13 nm and 0.34 nm for light of wavelength λ = 633 nm (red Hesbnd Ne laser). This study suggests that InN would be a better choice for fabrication of new imaging plasmonic biosensors for chemical and biological sensing.

  16. III-V/Si hybrid photonic devices by direct fusion bonding

    NASA Astrophysics Data System (ADS)

    Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

    2012-04-01

    Monolithic integration of III-V compound semiconductors on silicon is highly sought after for high-speed, low-power-consumption silicon photonics and low-cost, light-weight photovoltaics. Here we present a GaAs/Si direct fusion bonding technique to provide highly conductive and transparent heterojunctions by heterointerfacial band engineering in relation to doping concentrations. Metal- and oxide-free GaAs/Si ohmic heterojunctions have been formed at 300°C sufficiently low to inhibit active material degradation. We have demonstrated 1.3 μm InAs/GaAs quantum dot lasers on Si substrates with the lowest threshold current density of any laser on Si to date, and AlGaAs/Si dual-junction solar cells, by p-GaAs/p-Si and p-GaAs/n-Si bonding, respectively. Our direct semiconductor bonding technique opens up a new pathway for realizing ultrahigh efficiency multijunction solar cells with ideal bandgap combinations that are free from lattice-match restrictions required in conventional heteroepitaxy, as well as enabling the creation of novel high performance and practical optoelectronic devices by III-V/Si hybrid integration.

  17. Theoretical discovery of stable structures of group III-V monolayers: The materials for semiconductor devices

    NASA Astrophysics Data System (ADS)

    Suzuki, Tatsuo

    2015-11-01

    Group III-V compounds are very important as the materials of semiconductor devices. Stable structures of the monolayers of group III-V binary compounds have been discovered by using first-principles calculations. The primitive unit cell of the discovered structures is a rectangle, which includes four group-III atoms and four group-V atoms. A group-III atom and its three nearest-neighbor group-V atoms are placed on the same plane; however, these connections are not the sp2 hybridization. The bond angles around the group-V atoms are less than the bond angle of sp3 hybridization. The discovered structure of GaP is an indirect transition semiconductor, while the discovered structures of GaAs, InP, and InAs are direct transition semiconductors. Therefore, the discovered structures of these compounds have the potential of the materials for semiconductor devices, for example, water splitting photocatalysts. The discovered structures may become the most stable structures of monolayers which consist of other materials.

  18. Properties of Group-IV, III-V and II-VI Semiconductors

    NASA Astrophysics Data System (ADS)

    Adachi, Sadao

    2005-03-01

    Almost all the semiconductors of practical interest are the group-IV, III-V and II-VI semiconductors and the range of technical applications of such semiconductors is extremely wide. The purpose of this book is twofold: * to discuss the key properties of the group-IV, III-V and II-VI semiconductors * to systemize these properties from a solid-state physics aspect The majority of the text is devoted to the description of the lattice structural, thermal, elastic, lattice dynamic, electronic energy-band structural, optical and carrier transport properties of these semiconductors. Some corrective effects and related properties, such as piezoelectric, elastooptic and electrooptic properties, are also discussed. The book contains convenient tables summarizing the various material parameters and the definitions of important semiconductor properties. In addition, graphs are included in order to make the information more quantitative and intuitive. The book is intended not only for semiconductor device engineers, but also physicists and physical chemists, and particularly students specializing in the fields of semiconductor synthesis, crystal growth, semiconductor device physics and technology.

  19. Integrating III-V compound semiconductors with silicon using wafer bonding

    NASA Astrophysics Data System (ADS)

    Zhou, Yucai

    2000-12-01

    From Main Street to Wall Street, everyone has felt the effects caused by the Internet revolution. The Internet has created a new economy in the New Information Age and has brought significant changes in both business and personal life. This revolution has placed strong demands for higher bandwidth and higher computing speed due to high data traffic on today's information highway. In order to alleviate this problem, growing interconnection bottlenecks in digital designs have to be solved. The most feasible and practical way is to replace the conventional electrical interconnect with an optical interconnect. Since silicon does not have the optical properties necessary to accommodate these optical interconnect requirements, III-V based devices, most of which are GaAs-based or InP-based, must be intimately interconnected with the Si circuit at chip level. This monolithic integration technology enables the development of both intrachip and interchip optical connectors to take advantage of the enormous bandwidth provided by both high-performance very-large-scale integrated (VLSI) circuits and allied fiber and free-space optical technologies. However, lattice mismatch and thermal expansion mismatches between III-V materials and Si create enormous challenges for developing a feasible technology to tackle this problem. Among all the available approaches today, wafer bonding distinguishes itself as the most promising technology for integration due to its ability to overcome the constraints of both lattice constant mismatch and thermal expansion coefficient differences and even strain due to the crystal orientation. We present our development of wafer bonding technology for integrating III-V with Si in my dissertation. First, the pick-and-place multiple-wafer bonding technology was introduced. Then we systematically studied the wafer bonding of GaAs and InP with Si. Both high temperature wafer fusion and low/room temperature (LT/RT) wafer bonding have been investigated for different applications. We also systematically studied the electrical properties of bonding interfaces for high temperature wafer fusion of GaAs/Si and InP/Si. Room temperature and low temperature wafer bonding technology has been invented primarily for bonding GaAs with Si due to larger thermal expansion coefficient mismatches. Finally, we showed the feasibility and practicality of our wafer bonding technologies by fabricating high performance devices. A high performance InP-based avalanche photodetector on Si was fabricated utilizing the high temperature wafer fusion of InP and Si. And a 0.85 μm GaAs-based vertical cavity surface emitting lasers (VCSELs) were fabricated by utilizing the low temperature wafer bonding of GaAs and Si.

  20. Dilute group III-V nitride intermediate band solar cells with contact blocking layers

    DOEpatents

    Walukiewicz, Wladyslaw; Yu, Kin Man

    2015-02-24

    An intermediate band solar cell (IBSC) is provided including a p-n junction based on dilute III-V nitride materials and a pair of contact blocking layers positioned on opposite surfaces of the p-n junction for electrically isolating the intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thereby increasing open circuit voltage (V.sub.OC) of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC. Hence, the overall power conversion efficiency of a IBSC will be much higher than an conventional single junction solar cell. The p-n junction absorber layers of the IBSC may further have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection.

  1. Dilute Group III-V nitride intermediate band solar cells with contact blocking layers

    DOEpatents

    Walukiewicz, Wladyslaw; Yu, Kin Man

    2012-07-31

    An intermediate band solar cell (IBSC) is provided including a p-n junction based on dilute III-V nitride materials and a pair of contact blocking layers positioned on opposite surfaces of the p-n junction for electrically isolating the intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thereby increasing open circuit voltage (V.sub.OC) of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC. Hence, the overall power conversion efficiency of a IBSC will be much higher than an conventional single junction solar cell. The p-n junction absorber layers of the IBSC may further have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection.

  2. Lattice-Mismatched III-V Epilayers for High-Efficiency Photovoltaics

    SciTech Connect

    Ahrenkiel, Scott Phillip

    2013-06-30

    The project focused on development of new approaches and materials combinations to expand and improve the quality and versatility of lattice-mismatched (LMM) III-V semiconductor epilayers for use in high-efficiency multijunction photovoltaic (PV) devices. To address these goals, new capabilities for materials synthesis and characterization were established at SDSM&T that have applications in modern opto- and nano-electronics, including epitaxial crystal growth and transmission electron microscopy. Advances were made in analyzing and controlling the strain profiles and quality of compositional grades used for these technologies. In particular, quaternary compositional grades were demonstrated, and a quantitative method for characteristic X-ray analysis was developed. The project allowed enhanced collaboration between scientists at NREL and SDSM&T to address closely related research goals, including materials exchange and characterization.

  3. The reliability study of III-V solar cell with copper based contacts

    NASA Astrophysics Data System (ADS)

    Hsu, Ching-Hsiang; Chang, Edward Yi; Chang, Hsun-Jui; Maa, Jer-Shen; Pande, Krishna

    2015-12-01

    The reliability of III-V solar cell with copper based contacts as low-cost metallurgy option for solar cells including Cu-based Cu/Ge/Pd contact on n-type GaAs and Cu/Pt/Ti/Pt contact on p-type Ge is studied in this paper. The Cu-based contacts have low specific contact resistances of the order of 10-6 Ω cm2. The solar cells with the proposed Cu-based structures were subjected to high-temperature annealing (250 °C) and a high DC current (6.5 × 10-4 mA/μm2) stress test. Overall, the solar cell adopting these Cu based contacts remained quite stable and demonstrated excellent performances after these reliability tests.

  4. Design High-Efficiency III-V Nanowire/Si Two-Junction Solar Cell.

    PubMed

    Wang, Y; Zhang, Y; Zhang, D; He, S; Li, X

    2015-12-01

    In this paper, we report the electrical simulation results of a proposed GaInP nanowire (NW)/Si two-junction solar cell. The NW physical dimensions are determined for optimized solar energy absorption and current matching between each subcell. Two key factors (minority carrier lifetime, surface recombination velocity) affecting power conversion efficiency (PCE) of the solar cell are highlighted, and a practical guideline to design high-efficiency two-junction solar cell is thus provided. Considering the practical surface and bulk defects in GaInP semiconductor, a promising PCE of 27.5 % can be obtained. The results depict the usefulness of integrating NWs to construct high-efficiency multi-junction III-V solar cells. PMID:26123270

  5. Optical devices for ultra-compact photonic integrated circuits based on III-V/polymer nanowires

    NASA Astrophysics Data System (ADS)

    Lauvernier, D.; Garidel, S.; Zegaoui, M.; Vilcot, J. P.; Harari, J.; Magnin, V.; Decoster, D.

    2007-04-01

    We demonstrated the potential application of III-V/polymer nanowires for photonic integrated circuits in a previous paper. Hereby, we report the use of a spot size converter based on 2D reverse nanotaper structure in order to improve the coupling efficiency between the nanowire and optical fiber. A total coupling enhancement of up to a factor 60 has been measured from an 80 nm × 300 nm cross-section tip which feeds an 300 nm-side square nanowire at its both ends. Simultaneously, micro-radius bends have been fabricated to increase the circuit density; for a radius of 5 µm, the 90º bend losses were measured as low as 0.60 dB and 0.80 dB for TE and TM polarizations respectively.

  6. Analytic drain current model for III-V cylindrical nanowire transistors

    NASA Astrophysics Data System (ADS)

    Marin, E. G.; Ruiz, F. G.; Schmidt, V.; Godoy, A.; Riel, H.; Gámiz, F.

    2015-07-01

    An analytical model is proposed to determine the drain current of III-V cylindrical nanowires (NWs). The model uses the gradual channel approximation and takes into account the complete analytical solution of the Poisson and Schrödinger equations for the Γ-valley and for an arbitrary number of subbands. Fermi-Dirac statistics are considered to describe the 1D electron gas in the NWs, being the resulting recursive Fermi-Dirac integral of order -1/2 successfully integrated under reasonable assumptions. The model has been validated against numerical simulations showing excellent agreement for different semiconductor materials, diameters up to 40 nm, gate overdrive biases up to 0.7 V, and densities of interface states up to 1013eV-1cm-2 .

  7. Semiempirical Tight Binding Modeling of Electronic Band Structure of III-V Nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Gürel, H. Hakan; Akinci, Özden; Ünlü, Hilmi

    2007-04-01

    In this work, we discuss the composition and strain effects on the electronic band structure modeling of III-V nitrides heterostructures using the second nearest neighbor sp3s* semi-empirical tight binding theory. The model Hamiltonian includes the second nearest neighbor (2nn) interactions, the spin-orbit splitting and the nonlinear variations of the atomic energy levels and the bond length with ternary mole fraction. There is an excellent agreement between the model predictions and experiment for the principal band gaps at Γ, L and X symmetry points of Brillouin zone for AlN, GaN, InN and GaAs binaries and AlGaN, InGaN and GaAsN ternaries. The model predicts that the composition effects on the valence band offsets is small and linear but the conduction band offsets is nonlinear function of composition and large for large strain due to large deformation potential.

  8. Nucleation and growth of dielectric films on III-V semiconductors during atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Granados Alpizar, Bernal

    In order to continue with metal-oxide-semiconductors (CMOS) transistor scaling and to reduce the power density, the channel should be replaced with a material having a higher electron mobility, such as a III-V semiconductor. However, the integration of III-V's is a challenge because these materials oxidize rapidly when exposed to air and the native oxide produced is characterized by a high density of defects. Deposition of high-k materials on III-V semiconductors using Atomic Layer Deposition (ALD) reduces the thickness of these oxides, improving the semiconductor/oxide interface quality and the transistor electrical characteristics. In this work, ALD is used to deposit two dielectrics, Al 2O3 and TiO2, on two III-V materials, GaAs and InGaAs, and in-situ X-ray photoelectron spectroscopy (XPS) and in-situ thermal programmed desorption (TPD) are used for interface characterization. Hydrofluoric acid (HF) etching of GaAs(100) and brief reoxidation in air produces a 9.0 ±1.6 Å-thick oxide overlayer containing 86% As oxides. The oxides are removed by 1 s pulses of trimethylaluminum (TMA) or TiCl4. TMA removes the oxide overlayer while depositing a 7.5 ± 1.6 Å thick aluminum oxide. The reaction follows a ligand exchange mechanism producing nonvolatile Al-O species that remain on the surface. TiCl4 exposure removes the oxide overlayer in the temperature range 89°C to 300°C, depositing approximately 0.04 monolayer of titanium oxide for deposition temperatures from 89°C to 135°C, but no titanium oxide is present from 170 °C to 230 °C. TiCl4 forms a volatile oxychloride product and removes O from the surface while leaving Cl atoms adsorbed to an elemental As layer, chemically passivating the surface. The native oxide of In0.53Ga0.47As(100) is removed using liquid HF and gas phase HF before deposition of Al2O3 using TMA and H2O at 170 °C. An aluminium oxide film with a thickness of 7.2 ± 1.2 Å and 7.3 ± 1.2 Å is deposited during the first pulse of TMA on liquid and gas phase HF treated samples, respectively. After three complete ALD cycles the thickness of the aluminum oxide film is 10.0 ± 1.2 Å on liquid HF treated and 6.6 ± 1.2 Å on gas phase HF treated surfaces. Samples treated with gas phase HF inhibit growth. Inhibition is caused by residual F atoms that passivate the surface and by surface poisoning due to the thicker carbon film deposited during the first pulse of TMA. On InGaAs covered by native oxide, the first TMA pulse deposits 9 Å of aluminum oxide, and reaches saturation at 13 Å after 15 pulses of TMA. The film grows by scavenging oxygen from the substrate oxides. Substrate oxides are reduced by the first pulse of TMA even at 0°C. At 0°C, on a 9 Å thick Ga-rich oxide surface, 1 pulse of TMA mainly physisorbs and a limited amount of aluminum oxide is deposited. At 0°C, 110°C, and 170°C, more aluminum oxide is deposited on surfaces initially containing As oxide, and larger binding energy (BE) shifts of the O 1s peak are observed compared to surfaces that contain Ga oxides only, showing that As oxides improve the nucleation of Al2O 3.

  9. Optical transmission between III-V chips on Si using photonic wire bonding.

    PubMed

    Gu, Zhichen; Amemiya, Tomohiro; Ishikawa, Atsushi; Hiratani, Takuo; Suzuki, Junichi; Nishiyama, Nobuhiko; Tanaka, Takuo; Arai, Shigehisa

    2015-08-24

    Photonic wire bonding (PWB) was used to achieve flexible chip-scale optical interconnection as a kind of 3D-freeform polymer waveguide based on the two-photon polymerization of SU-8. First, the fabrication conditions of PWB were determined for the two-photon absorption process, and the coupling structure between PWB and III-V optical components was numerically simulated in order to obtain high coupling efficiency. Then, using PWB, chip-to-chip optical transmission was realized between laser and detector chips located on a common Si substrate. We fabricated a 2.5-μm-wide PWB with 1:3 aspect ratio between two optical chips of 140-μm gap and achieved a connection loss of approximately 10 dB. PMID:26368209

  10. Ab initio synthesis of single-layer III-V materials

    NASA Astrophysics Data System (ADS)

    Singh, Arunima K.; Zhuang, Houlong L.; Hennig, Richard G.

    2014-06-01

    The discovery of a novel material requires the identification of the material's composition as well as of suitable synthesis conditions. We present a data-mining approach to identify suitable substrates for the growth of two-dimensional materials and apply the method to the recently predicted two-dimensional III-V compounds. We identify several lattice-matched substrates for their epitaxial growth, stabilization, and functionalization. Density-functional calculations show that these substrates sufficiently reduce the formation energies of the metastable two-dimensional materials to make them thermodynamically stable. We show that chemical interactions of the two-dimensional materials with the substrates shift the Fermi level of these materials, resulting in doping. The large adsorption energies and strong doping indicate that these metals should provide good electrical contact to enable transport measurements and electronic applications.

  11. Modeling of axial heterostructure formation in ternary III-V nanowires

    NASA Astrophysics Data System (ADS)

    Koryakin, A. A.; Sibirev, N. V.; Zeze, D. A.

    2015-11-01

    A model is proposed to depict the formation of axial heterostructure in ternary III-V nanowires (NW) grown by the catalytic vapor-liquid-solid (VLS) method. Our approach is based on the determination of chemical potential of a four-component liquid using the regular solution model and Stringfellow's scheme for the computation of the interaction coefficients of species present in the droplet. The model allows the estimation of the heterojunction width dependence on the growth temperature. This dependence has not been reported before by any previous theoretical studies. The AlGaAs/GaAs heterojunction formation in the Au-catalyzed AlGaAs NWs was considered as an example of ternary system. The heterojunction width was found to increase with the growth temperature with a second-order polynomial dependence.

  12. Parallel nanogap fabrication with nanometer size control using III-V semiconductor epitaxial technology.

    PubMed

    Fernández-Martínez, Iván; González, Yolanda; Briones, Fernando

    2008-07-01

    A nanogap fabrication process using strained epitaxial III-V beams is reported. The process is highly reproducible, allowing parallel fabrication and nanogap size control. The beams are fabricated from MBE-grown (GaAs/GaP)/AlGaAs strained heterostructures, standard e-beam lithography and wet etching. During the wet etching process, the relaxation of the accumulated stress at the epitaxial heterostructure produces a controlled beam breakage at the previously defined beam notch. After the breakage, the relaxed strain is proportional to the beam length, allowing nanogap size control. The starting structure is similar to a mechanically adjustable break junction but the stress causing the breakage is, in this case, built into the beam. This novel technique should be useful for molecular-scale electronic devices. PMID:21828698

  13. Scanning tunneling microscopy of III-V compound semiconductor (001) surfaces

    NASA Astrophysics Data System (ADS)

    Xue, Qi-Kun; Hashizume, T.; Sakurai, T.

    1997-10-01

    While the (001) oriented substrate of compound semiconductors are most commonly used in fabrication of wireless and opto-electronic devices by molecular beam epitaxy, metallorganic chemical vapor deposition and related techniques, their surface structures have been puzzling from the beginning of the development of the techniques with which these materials are artificially prepared. This paper reviews the advances in comprehensive understanding of the geometric and electronic structures and chemical properties of the principal reconstructions found on the (001) surface of III-V compound semiconductors including arsenides, such as GaAs, InAs and AlAs, phosphides, such as.GaP and InP, antimonides, such as GaSb, AlSb and InSb, and also nitrides (GaN), with the emphasis on the GaAs(001), during the first decade following the invention of scanning tunneling microscopy.

  14. New III-V cell design approaches for very high efficiency

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P. )

    1993-04-01

    This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell's efficiency less dependent on materialquality.

  15. Bismuth-induced surface structure and morphology in III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Duzik, Adam J.

    2015-04-01

    Bi is the largest group V element and has a number of advantages in III-V semiconductor properties, such as bandgap reduction, spin-orbit coupling, a preserved electron mobility over III-V-N materials, and nearly ideal surfactant properties resulting in a surface smoothing effect on GaAs. However, the mechanism for this behavior is not well understood. Insight on the mechanism is obtained through study of the Bi-terminated GaAs surface morphology and atomic reconstructions produced via molecular beam epitaxy (MBE). Experimental scanning tunneling microscopy (STM) characterization of the Bi/GaAs surface reveal disordered (1x3), (2x3), and (4x3) reconstructions, often sharing the same reflective high-energy electron diffraction (RHEED) patterns. Roughness on the micron length scale decreases as the step widen, attributed to the concurrent increase of opposite direction step edges on the nanometer length scale. Corresponding cluster expansion, density functional theory (DFT), and Monte Carlo simulations all point to the stability of the disordered (4x3) reconstruction at finite temperature as observed in experimental STM. The effects of incorporated Bi are determined through epitaxial GaSbBi growth on GaSb with various Ga:Sb:Bi flux ratios. Biphasic surface droplets are observed with sub-droplets, facets, and substrate etching. Despite the rough growth front, X-ray diffraction (XRD) and Rutherford backscatter (RBS) measurements show significant Bi incorporation of up to 12% into GaSb, along with a concurrent increase of background As concentration. This is attributed to a strain auto-compensation effect. Bi incorporation of up to 10% is observed for the highest Bi fluxes while maintaining low surface droplet density.

  16. Method for laser-assisted etching of III-V and II-VI semiconductor compounds using chlorofluorocarbon ambients

    NASA Astrophysics Data System (ADS)

    Russell, Stephen D.; Sexton, Douglas A.; Orazi, Richard J.

    1994-05-01

    An etching process allows a selective single-step patterning of III-V or II-VI semiconductor compound devices such as GaAs and InP or CdS and ZnSe in a noncorrosive environment. The etching relies on a maskless laser-assisted technique in a gaseous chlorofluorocarbon ambient, such as gaseous dichlorodifluoromethane and chloropentafluoroethane. Laser-assisted photothermal chemical etching reactions on the III-V or II-VI semiconductor compounds occur in these ambients when the incident fluence from an excimer laser at 248 nm exceeds the melt threshold. This provides a means for thin membrane formation in III-V or II-VI semiconductor compounds, rapid etches and processing of packaged devices or partially fabricated dies. The reduction in processing steps as compared to conventional wet chemical etches provides improvements in yield, reliability and cost.

  17. Fabrication and Characterization of Optoelectronics Devices Based on III-V Materials for Infrared Applications by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Torfi, Amin

    Optoelectronic devices based on III-V materials operating in infrared wavelength range have been attracting intensive research effort due to their applications in optical communication, remote sensing, spectroscopy, and environmental monitoring. The novel semiconductor lasers and photodetectors structures and materials investigated in this thesis cover the spectral range from 1.3µm to 12µm. This spectral region includes near-infrared (NIR), mid-infrared (MIR) and long wavelength infrared. This thesis demonstrated infrared optoelectronic devices, based on III-V compound semiconductors grown by Molecular Beam Epitaxy (MBE), utilizing various combinations of novel III-V materials, device structures and substrate orientations. This thesis will be presented in two parts; the first part focuses on two types of photodetectors; type-II InAs/GaSb superlattice IR detector and AlGaAsSb/InGaAsSb mid-infrared heterojunction p-i-n photodetector. The second part of this thesis focuses on the three types of quantum well (QW) lasers; phosphor-free1.3µm InAlGaAs strain-compensated multiple-quantum-well (SCMQW) lasers on InP (100), InGaAsNSb/GaAs quantum wells (QWs) grown on GaAs (411)A substrates and mid-infrared InGaAsSb lasers with digitally grown tensile-strained AlGaAsSb barriers. Type-II InAs/GaSb superlattice IR detectors with various spectral ranges were grown by MBE. Two superlattice structures with 15 monolayers (ML) of InAs/12ML GaSb and 17ML InAs/7ML GaSb are discussed. Based on X-ray diffraction (XRD) measurements both InAs/GaSb superlattices exhibit excellent material qualities with the full width at half maximum (FWHM) of the 0th-order peak about 20arcsec, which is among the narrowest ever reported. The 50% cutoff wavelengths at 80K of the two photodiodes with 15ML InAs/12ML GaSb and 17ML InAs/7ML GaSb superlattices are measured to be 10.2µm and 6.6µm, respectively. Mid-infrared heterojunction p-i-n photodetector, AlGaAsSb/InGaAsSb lattice-matched to GaSb grown by solid source molecular beam epitaxy using As and Sb valved crackers greatly facilitated the lattice-matching of the quaternary InGaAsSb absorbing layer to the GaSb substrates, as characterized by X-ray diffraction. The resulting device exhibited low dark current and a breakdown voltage of 32V at room temperature. A record Johnson-noise-limited detectivity of 9.0 × 1010 cm Hz½/W was achieved at 290K. The 50% cutoff wavelength of the device was 2.57 µm. Thus, our result has clearly demonstrated the potential of very high-performance lattice-matched InGaAsSb p-i-n photodetectors for mid-infrared wavelengths. For phosphor-free1.3 µm InAlGaAs multiple-quantum-well (MQW) lasers, the substrate temperature has been found to be a critical growth parameter for lattice-matched InAl(Ga)As layers in the laser structures. As shown by X-ray diffraction measurements, in the temperature range of 485-520° C, spontaneously ordered superlattices (SLs) with periods around 7-10 nm were formed in the bulk InAl(Ga)As layers. Based on photoluminescence (PL) measurements, a large band gap reduction of 300 meV and a broadened PL peak were observed for the In0.52 Al0.48As layers with SL, as compared to those without SL. The undesirable, spontaneously-ordered SL can be avoided by using MBE growth temperatures higher than 530 °C. This results in a high laser performance. Threshold-current density as low as 690 A/cm2 and T0 as high as 80 K were achieved for InAlGaAs laser bars emitting at 1310 nm. InGaAsNSb/GaAs QWs on GaAs (411)A exhibited remarkably enhanced photoluminescence efficiency compared with the same structures on conventional GaAs (100) substrates. It was further observed that the optimum growth temperature for (411)A was 30 °C higher than that for (100). To explain this phenomenon, a model based on the self-assembling of local rough surface domains into a unique global smooth surface at the lowest energy state of the system is proposed. Lastly, the digital-growth approach for tensile-strained AlGaAsSb barriers improved the reliability and controllability of MBE growth for the MQW active region in the mid-infrared InGaAsSb quantum well lasers. The optical and structural qualities of InGaAsSb MQW were improved significantly, as compared to those with random-alloy barriers due to the removal of growth interruption at the barrier/well interfaces in digital growth. As a result, high-performance devices were achieved in the InGaAsSb lasers with digital AlGaAsSb barriers. A low threshold current density of 163 A/cm2 at room temperature was achieved for 1000-µm-long lasers emitting at 2.38 µm. An external differential quantum efficiency as high as 61% was achieved for the 880-µm-long lasers, the highest ever reported for any lasers in this wavelength range.

  18. High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrator Application

    SciTech Connect

    Hubbard, Seth

    2012-09-12

    The High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrators project seeks to provide new photovoltaic cells for Concentrator Photovoltaics (CPV) Systems with higher cell efficiency, more favorable temperature coefficients and less sensitivity to changes in spectral distribution. The main objective of this project is to provide high efficiency III-V solar cells that will reduce the overall cost per Watt for power generation using CPV systems.This work is focused both on a potential near term application, namely the use of indium arsenide (InAs) QDs to spectrally "tune" the middle (GaAs) cell of a SOA triple junction device to a more favorable effective bandgap, as well as the long term goal of demonstrating intermediate band solar cell effects. The QDs are confined within a high electric field i-region of a standard GaAs solar cell. The extended absorption spectrum (and thus enhanced short circuit current) of the QD solar cell results from the increase in the sub GaAs bandgap spectral response that is achievable as quantum dot layers are introduced into the i-region. We have grown InAs quantum dots by OMVPE technique and optimized the QD growth conditions. Arrays of up to 40 layers of strain balanced quantum dots have been experimentally demonstrated with good material quality, low residual stain and high PL intensity. Quantum dot enhanced solar cells were grown and tested under simulated one sun AM1.5 conditions. Concentrator solar cells have been grown and fabricated with 5-40 layers of QDs. Testing of these devices show the QD cells have improved efficiency compared to baseline devices without QDs. Device modeling and measurement of thermal properties were performed using Crosslight APSYS. Improvements in a triple junction solar cell with the insertion of QDs into the middle current limiting junction was shown to be as high as 29% under one sun illumination for a 10 layer stack QD enhanced triple junction solar cell. QD devices have strong potential for net gains in efficiency at high concentration.

  19. Alloy

    NASA Astrophysics Data System (ADS)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  20. The Painlevé III, V and VI transcendents as solutions of the Einstein-Weyl equations

    NASA Astrophysics Data System (ADS)

    Schief, W. K.

    2000-03-01

    We demonstrate that the integrable Ernst-Weyl equation governing neutrino and gravitational fields in axially symmetric space-times of general relativity admits symmetry reductions to the Painlevé III, V and VI equations with arbitrary constants. In particular, the matrix form of PVI is shown to be a canonical symmetry reduction of the integrable Loewner-Konopelchenko-Rogers (LKR) system.

  1. Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

    NASA Astrophysics Data System (ADS)

    Campbell, Philip M.; Tarasov, Alexey; Joiner, Corey A.; Ready, W. Jud; Vogel, Eric M.

    2016-01-01

    Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

  2. Group V sensitive vapor-liquid-solid growth of Au-catalyzed and self-catalyzed III-V nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, Vladimir G.

    2016-04-01

    We present a new theoretical model that treats the group V sensitive growth rates and structures of Au-catalyzed and self-catalyzed III-V nanowires within a single kinetic picture. It is shown that Au-catalyzed III-V nanowires can grow with a time-independent radius within a wide range of parameters. At high V/III flux ratios, the vapor-liquid-solid growth of Au catalyzed III-V nanowires is controlled by surface diffusion of the group III adatoms, while at low V/III flux ratios it becomes nucleation-limited. Conversely, self-catalyzed III-V nanowires cannot grow with a time-independent droplet size and instead such nanowires may either swell or shrink or converge to a certain stationary radius depending on the V/III flux ratio. Quite importantly, the results are presented in a concise analytical form which is convenient for comparison with experimental data or prior theoretical works. We demonstrate how the model fits the data obtained previously for Au- and Ga-catalyzed GaAs nanowires.

  3. Interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates

    NASA Astrophysics Data System (ADS)

    He, Gang; Chen, Xiaoshuang; Sun, Zhaoqi

    2013-03-01

    Recently, III-V materials have been extensively studied as potential candidates for post-Si complementary metal-oxide-semiconductor (CMOS) channel materials. The main obstacle to implement III-V compound semiconductors for CMOS applications is the lack of high quality and thermodynamically stable insulators with low interface trap densities. Due to their excellent thermal stability and relatively high dielectric constants, Hf-based high-k gate dielectrics have been recently highlighted as the most promising high-k dielectrics for III-V-based devices. This paper provides an overview of interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. To address the impact of these hafnium based materials, their interfaces with GaAs as well as a variety of semiconductors are discussed. After that, the integration issues are highlighted, including the development of high-k deposition without Fermi level pinning, surface passivation and interface state, and integration of novel device structure with Si technology. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This review explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.

  4. Impact of photon recycling and luminescence coupling in III-V photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Walker, A. W.; Höhn, O.; Micha, D. N.; Wagner, L.; Helmers, H.; Bett, A. W.; Dimroth, F.

    2015-03-01

    Single junction photovoltaic devices composed of direct bandgap III-V semiconductors such as GaAs can exploit the effects of photon recycling to achieve record-high open circuit voltages. Modeling such devices yields insight into the design and material criteria required to achieve high efficiencies. For a GaAs cell to reach 28 % efficiency without a substrate, the Shockley-Read-Hall (SRH) lifetimes of the electrons and holes must be longer than 3 μs and 100 ns respectively in a 2 μm thin active region coupled to a very high reflective (>99%) rear-side mirror. The model is generalized to account for luminescence coupling in tandem devices, which yields direct insight into the top cell's non-radiative lifetimes. A heavily current mismatched GaAs/GaAs tandem device is simulated and measured experimentally as a function of concentration between 3 and 100 suns. The luminescence coupling increases from 14 % to 33 % experimentally, whereas the model requires an increasing SRH lifetime for both electrons and holes to explain these experimental results. However, intermediate absorbing GaAs layers between the two sub-cells may also increasingly contribute to the luminescence coupling as a function of concentration.

  5. III-V GaAs based plasmonic lasers (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Lafone, Lucas; Nguyen, Ngoc; Clarke, Ed; Fry, Paul; Oulton, Rupert F.

    2015-09-01

    Plasmonics is a potential route to new and improved optical devices. Many predict that sub wavelength optical systems will be essential in the development of future integrated circuits, offering the only viable way of simultaneously increasing speed and reducing power consumption. Realising this potential will be contingent on the ability to exploit plasmonic effects within the framework of the established semiconductor industry and to this end we present III-V (GaAs) based surface plasmon laser platform capable of effective laser light generation in highly focussed regions of space. Our design utilises a suspended slab of GaAs with a metallic slot printed on top. Here, hybridisation between the plasmonic mode of the slot and the photonic mode of the slab leads to the formation of a mode with confinement and loss that can be adjusted through variation of the slot width alone. As in previous designs the use of a hybrid mode provides strong confinement with relatively low losses, however the ability to print the metal slot removes the randomness associated with device fabrication and the requirement for etching that can deteriorate the semiconductor's properties. The deterministic fabrication process and the use of bulk GaAs for gain make the device prime for practical implementation.

  6. Proton irradiation effects on advanced digital and microwave III-V components

    SciTech Connect

    Hash, G.L.; Schwank, J.R.; Shaneyfelt, M.R.; Sandoval, C.E.; Connors, M.P.; Sheridan, T.J.; Sexton, F.W.; Slayton, E.M.; Heise, J.A.; Foster, C.

    1994-09-01

    A wide range of advanced III-V components suitable for use in high-speed satellite communication systems were evaluated for displacement damage and single-event effects in high-energy, high-fluence proton environments. Transistors and integrated circuits (both digital and MMIC) were irradiated with protons at energies from 41 to 197 MeV and at fluences from 10{sup 10} to 2 {times} 10{sup 14} protons/cm{sup 2}. Large soft-error rates were measured for digital GaAs MESFET (3 {times} 10{sup {minus}5} errors/bit-day) and heterojunction bipolar circuits (10{sup {minus}5} errors/bit-day). No transient signals were detected from MMIC circuits. The largest degradation in transistor response caused by displacement damage was observed for 1.0-{mu}m depletion- and enhancement-mode MESFET transistors. Shorter gate length MESFET transistors and HEMT transistors exhibited less displacement-induced damage. These results show that memory-intensive GaAs digital circuits may result in significant system degradation due to single-event upset in natural and man-made space environments. However, displacement damage effects should not be a limiting factor for fluence levels up to 10{sup 14} protons/cm{sup 2} [equivalent to total doses in excess of 10 Mrad(GaAs)].

  7. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Sardela, Mauro; Zuo, Jianmin; Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting; Braun, Paul V.

    2015-12-01

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured GaxIn1-xP (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  8. Simulation of III-V strained quantum well lasers with coupled concentric racetrack resonators

    NASA Astrophysics Data System (ADS)

    Viegas, Jaime; Xing, Peng; Serunjogi, Solomon M.

    2014-03-01

    The simulation of the lasing behavior of semiconductor quantum well structures with accurate description of transport phenomena and optical propagation poses great challenges when complex epitaxial layers are coupled with optical cavities in the transverse direction that are more complex than the well know Fabry-Pérot and distributed feedbackreflector based resonators. In this work, we present an approximate approach for the simulation of an electricallypumped III-V strained quantum well laser with coupled concentric racetrack resonators. The electrical, thermal and optical behavior of an epitaxial stack with at least one quantum well is obtained from a physics based simulator for a reduced dimensionality problem, and this solution is coupled with the cold cavity analysis of the resonator using either finite difference time domain simulation or coupled-mode analysis. The effects of gain and charge transport on the active resonator are then taken into account as a perturbation and the approximate solution derived. Comparison with actual devices based on InGaAlAs/InGaAs/InP and InGaSb/AlGaAsSb/GaSb shows reasonable agreement. The concentric racetrack resonator exhibits complex dispersive behavior, with possible applications in sensing, nonlinear phenomena and optical signal processing.

  9. Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers

    SciTech Connect

    Umlor, M.T.; Keeble, D.J.; Asoka-Kumar, P.; Lynn, K.G.; Cooke, P.W.

    1994-08-01

    A summary of recent positron annihilation experiments on molecular beam epitaxy (MBE) grown III-V layers is Presented. Variable energy positron beam measurements on Al{sub 0.32}Ga{sub 0.68}As undoped and Si doped have been completed. Positron trapping at a open volume defect in Al{sub 0.32}Ga{sub 0.68}:Si for temperatures from 300 to 25 K in the dark was observed. The positron trap was lost after 1.3 eV illumination at 25K. These results indicate an open volume defect is associated with the local structure of the deep donor state of the DX center. Stability of MBE GaAs to thermal annealing war, investigated over the temperature range of 230 to 700{degrees}C, Proximity wafer furnace anneals in flowing argon were used, Samples grown above 450{degrees}C were shown to be stable but for sample below this temperature an anneal induced vacancy related defect was produced for anneals between 400 and 500{degrees}C. The nature of the defect was shown to be different for material grown at 350 and 230{degrees}C. Activation energies of 2.5 eV to 2.3 eV were obtained from isochronal anneal experiments for samples grown at 350 and 230{degrees}C, respectively.

  10. Gate control of Berry phase in III-V semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis L.

    2014-06-01

    We analyze the Berry phase in III-V semiconductor quantum dots (QDs). We show that the Berry phase is highly sensitive to electric fields arising from the interplay between the Rashba and Dresselhaus spin-orbit (SO) couplings. We report that the accumulated Berry phase can be induced from other available quantum states that differ only by one quantum number of the corresponding spin state. The sign change in the g-factor due to the penetration of Bloch wave functions into the barrier materials can be reflected in the Berry phase. We provide characteristics of the Berry phase for three different length scales (spin-orbit length, hybrid orbital length, and orbital radius). We solve the time-dependent Schrödinger equation by utilizing the Feynman disentangling technique, and we investigate the evolution of spin dynamics during the adiabatic transport of QDs in the two-dimensional plane. Our results can pave the way to building a topological quantum computer in which the Berry phase can be engineered and be manipulated with the application of the spin-orbit couplings through gate-controlled electric fields.

  11. Proton irradiation effects on advanced digital and microwave III-V components

    NASA Astrophysics Data System (ADS)

    Hash, G. L.; Schwank, J. R.; Shaneyfelt, M. R.; Sandoval, C. E.; Connors, M. P.; Sheridan, T. J.; Sexton, F. W.; Slayton, E. M.; Heise, J. A.; Foster, C.

    1994-01-01

    A wide range of advanced III-V components suitable for use in high-speed satellite communication systems were evaluated for displacement damage and single-event effects in high-energy, high-fluence proton environments. Transistors and integrated circuits (both digital and MMIC) were irradiated with protons at energies from 41 to 197 MeV and at fluences from 10(exp 10) to 2 x 10(exp 14) protons/sq cm. Large soft-error rates were measured for digital GaAs MESFET (3 x 10(exp -5) errors/bit-day) and heterojunction bipolar circuits (10(exp -5) errors/bit-day). No transient signals were detected from MMIC circuits. The largest degradation in transistor response caused by displacement damage was observed for 1.0-(mu)m depletion- and enhancement-mode MESFET transistors. Shorter gate length MESFET transistors and HEMT transistors exhibited less displacement-induced damage. These results show that memory-intensive GaAs digital circuits may result in significant system degradation due to single-event upset in natural and man-made space environments. However, displacement damage effects should not be a limiting factor for fluence levels up to 10(exp 14) protons/sq cm (equivalent to total doses in excess of 10 Mrad(GaAs)).

  12. New Materials for Future Generations of III-V Solar Cells

    SciTech Connect

    Geisz, J. F.; Friedman, D. J.; Olson, J. M.; Kramer, C.; Kibbler, A.; Kurtz, S. R.

    1998-10-06

    Three- and four-junction III-V devices are proposed for ultrahigh-efficiency solar cells using a new 1-eV material lattice-matched to GaAs, namely, GaInNAs. We demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. Under the AM1.5 direct spectrum with all the light higher in energy than the GaAs band gap filtered out, the prototypes grown with base doping of about 10{sup 17} cm-3 have open-circuit voltages ranging from 0.35 to 0.44 V, short-circuit current densities of 1.8 mA/cm2, and fill factors from 61% to 66%. To improve on the current record-efficiency tandem GaInP/GaAs solar cell by adding a GaInNAs junction, the short-circuit current density of this 1-eV cell must be significantly increased. Because these low short-circuit current densities are due to short diffusion lengths, we have demonstrated a depletion-width-enhanced variation of one of the prototype devices that trades off decreased voltage for increased photocurrent, with a short-circuit current density of 7.4 mA/cm2 and an open-circuit voltage of 0.28 V.

  13. Compositional and Structural Characterization by TEM of Lattice-Mismatched III-V Epilayers

    SciTech Connect

    Ahrenkiel, S. P.; Rathi, M.; Nesheim, R.; Zheng, N.; Vunnam, S.; Carapella, J. J.; Wanlass, M. W.

    2011-01-01

    We discuss compositional and structural transmission electron microscopy (TEM) characterization of lattice-mismatched (LMM) III-V epilayers grown on GaAs by metalorganic chemical vapor deposition (MOCVD), with possible applications in high-efficiency multijunction solar cells. In addition to the use of TEM imaging to survey layer thicknesses and defect morphology, our analysis emphasizes the particular methods of energy-dispersive X-ray spectrometry (EDX) and convergent-beam electron diffraction (CBED). Outlined here is a standards-based method for extracting compositions by EDX, which uses principal-component analysis (PCA) [1], combined with the zeta-factor approach of Watanabe and Williams [2]. A procedure is described that uses the coordinates of high-order Laue zone (HOLZ) lines, which are found in the bright-field disks of CBED patterns, to extract composition and strain parameters from embedded epilayers. The majority of the crystal growth for this work was performed at NREL, which has accommodated the development at SDSM&T of the characterization techniques described. However, epilayer deposition capability at SDSM&T has recently been achieved, using a home-built system, which is presently being used to examine new lattice-mismatched structures relevant to photovoltaic technology.

  14. Raising the Efficiency Ceiling with Multijunction III-V Concentrator Photovoltaics

    SciTech Connect

    King, R. R.; Boca, A.; Edmondson, K. M.; Romero, M. J.; Yoon, H.; Law, D. C.; Fetzer, C. M.; Haddad, M.; Zakaria, A.; Hong, W.; Mesropian, S.; Krut, D. D.; Kinsey, G. S.; Pien, R.; Sherif, R. A.; Karam, N. H.

    2008-01-01

    In this paper, we look at the question 'how high can solar cell efficiency go?' from both theoretical and experimental perspectives. First-principle efficiency limits are analyzed for some of the main candidates for high-efficiency multijunction terrestrial concentrator cells. Many of these cell designs use lattice-mismatched, or metamorphic semiconductor materials in order to tune subcell band gaps to the solar spectrum. Minority-carrier recombination at dislocations is characterized in GaInAs inverted metamorphic solar cells, with band gap ranging from 1.4 to 0.84 eV, by light I-V, electron-beam-induced current (EBIC), and cathodoluminescence (CL). Metamorphic solar cells with a 3-junction GaInP/ GaInAs/ Ge structure were the first cells to reach over 40% efficiency, with an independently confirmed efficiency of 40.7% (AM1.5D, low-AOD, 240 suns, 25 C). The high efficiency of present III-V multijunction cells now in high-volume production, and still higher efficiencies of next-generation cells, is strongly leveraging for low-cost terrestrial concentrator PV systems.

  15. Spin Relaxation in III-V Semiconductors in various systems: Contribution of Electron-Electron Interaction

    NASA Astrophysics Data System (ADS)

    Dogan, Fatih; Kesserwan, Hasan; Manchon, Aurelien

    2015-03-01

    In spintronics, most of the phenomena that we are interested happen at very fast time scales and are rich in structure in time domain. Our understanding, on the other hand, is mostly based on energy domain calculations. Many of the theoretical tools use approximations and simplifications that can be perceived as oversimplifications. We compare the structure, material, carrier density and temperature dependence of spin relaxation time in n-doped III-V semiconductors using Elliot-Yafet (EY) and D'yakanov-Perel'(DP) with real time analysis using kinetic spin Bloch equations (KSBE). The EY and DP theories fail to capture details as the system investigated is varied. KSBE, on the other hand, incorporates all relaxation sources as well as electron-electron interaction which modifies the spin relaxation time in a non-linear way. Since el-el interaction is very fast (~ fs) and spin-conserving, it is usually ignored in the analysis of spin relaxation. Our results indicate that electron-electron interaction cannot be neglected and its interplay with the other (spin and momentum) relaxation mechanisms (electron-impurity and electron-phonon scattering) dramatically alters the resulting spin dynamics. We use each interaction explicitly to investigate how, in the presence of others, each relaxation source behaves. We use GaAs and GaN for zinc-blend structure, and GaN and AlN for the wurtzite structure.

  16. Bottom-up photonic crystal cavities formed by patterned III-V nanopillars.

    PubMed

    Scofield, Adam C; Shapiro, Joshua N; Lin, Andrew; Williams, Alex D; Wong, Ping-Show; Liang, Baolai L; Huffaker, Diana L

    2011-06-01

    We report on the formation and optical properties of bottom-up photonic crystal (PC) cavities formed by III-V nanopillars (NPs) via catalyst-free selective-area metal-organic chemical vapor deposition on masked GaAs substrates. This method of NP synthesis allows for precise lithographic control of NP position and diameter enabling simultaneous formation of both the photonic band gap (PBG) region and active gain region. The PBG and cavity resonance are determined by independently tuning the NP radius r, pitch a, and height h in the respective masked areas. Near-infrared emission at 970 nm is achieved from axial GaAs/InGaAs heterostructures with in situ passivation by laterally grown InGaP shells. To achieve out-of-plane optical confinement, the PC cavities are embedded in polydimethylsiloxane (PDMS) and removed from the growth substrate. Spatially and spectrally resolved 77 K photoluminescence demonstrates a strong influence of the PBG resonance on device emission. Resonant peaks are observed in the emission spectra of PC cavities embedded in PDMS. PMID:21591759

  17. Passively mode-locked III-V/silicon laser with continuous-wave optical injection.

    PubMed

    Cheng, Yuanbing; Luo, Xianshu; Song, Junfeng; Liow, Tsung-Yang; Lo, Guo-Qiang; Cao, Yulian; Hu, Xiaonan; Li, Xiaohui; Lim, Peng Huei; Wang, Qi Jie

    2015-03-01

    We demonstrate electrically pumped two-section mode locked quantum well lasers emitting at the L-band of telecommunication wavelength on silicon utilizing die to wafer bonding techniques. The mode locked lasers generate pulses at a repetition frequency of 30 GHz with signal to noise ratio above 30 dB and 1 mW average output power per facet. Optical injection-locking scheme was used to improve the noise properties of the pulse trains of passively mode-locked laser. The phases of the mode-locked frequency comb are shown to be coherent with that of the master continuous-wave (CW) laser. The radio-frequency (RF)-line-width is reduced from 7.6 MHz to 150 kHz under CW optical injection. The corresponding pulse-to-pulse jitter and integrated RMS jitter are 29.7 fs/cycle and 1.0 ps, respectively. The experimental results demonstrate that optical injection can reduce the noise properties of the passively mode locked III-V/Si laser in terms of frequency linewidth and timing jitter, which makes the devices attractive for photonic analog-to-digital converters and clock generation and recovery. PMID:25836859

  18. Comparison of methods to quantify interface trap densities at dielectric/III-V semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Engel-Herbert, Roman; Hwang, Yoontae; Stemmer, Susanne

    2010-12-01

    Methods to extract trap densities at high-permittivity (k) dielectric/III-V semiconductor interfaces and their distribution in the semiconductor band gap are compared. The conductance method, the Berglund intergral, the Castagné-Vapaille (high-low frequency), and Terman methods are applied to admittance measurements from metal oxide semiconductor capacitors (MOSCAPs) with high-k /In0.53Ga0.47As interfaces with different interface trap densities. The results are discussed in the context of the specifics of the In0.53Ga0.47As band structure. The influence of different conduction band approximations for determining the ideal capacitance-voltage (CV) characteristics and those of the MOSCAP parameters on the extracted interface trap density are investigated. The origins of discrepancies in the interface trap densities determined from the different methods are discussed. Commonly observed features in the CV characteristics of high-k /In0.53Ga0.47As interfaces are interpreted and guidelines are developed to obtain reliable estimates for interface trap densities and the degree of Fermi level (un)pinning for high-k /In0.53Ga0.47As interfaces.

  19. Monolithic integration of III-V nanowire with photonic crystal microcavity for vertical light emission.

    PubMed

    Larrue, Alexandre; Wilhelm, Christophe; Vest, Gwenaelle; Combrié, Sylvain; de Rossi, Alfredo; Soci, Cesare

    2012-03-26

    A novel photonic structure formed by the monolithic integration of a vertical III-V nanowire on top of a L3 two-dimensional photonic crystal microcavity is proposed to enhance light emission from the nanowire. The impact on the nanowire spontaneous emission rate is evaluated by calculating the spontaneous emission factor β, and the material gain at threshold is used as a figure of merit of this vertical emitting nanolaser. An optimal design is identified for a GaAs nanowire geometry with r = 155 nm and L~1.1 μm, where minimum gain at threshold (gth~13×10³ cm⁻¹) and large spontaneous emission factor (β~0.3) are simultaneously achieved. Modification of the directivity of the L3 photonic crystal cavity via the band-folding principle is employed to further optimize the far-field radiation pattern and to increase the directivity of the device. These results lay the foundation for a new approach toward large-scale integration of vertical emitting nanolasers and may enable applications such as intra-chip optical interconnects. PMID:22453454

  20. III-V Multi-junction solar cells and concentrating photovoltaic (CPV) systems

    NASA Astrophysics Data System (ADS)

    Philipps, Simon P.; Bett, Andreas W.

    2014-12-01

    It has been proven that the only realistic path to practical ultra-high efficiency solar cells is the monolithic multi-junction approach, i.e., to stack pn-junctions made of different semiconductor materials on top of each other. Each sub pn-junction, i.e., sub solar cell, converts a specific part of the sun's spectrum. In this way, the energy of the sunlight photons is converted with low thermalization losses. However, large-area multi-junction solar cells are still far too expensive if applied in standard PV modules. A viable solution to solve the cost issue is to use tiny solar cells in combination with optical concentrating technology, in particular, high concentrating photovoltaics (HCPV), in which the light is concentrated over the solar cells more than 500 times. The combination of ultra-high efficient solar cells and optical concentration lead to low cost on system level and eventually to low levelized cost of electricity, today, well below 8 €cent/kWh and, in the near future, below 5 €cent/kWh. A wide variety of approaches exists for III-V multi-junction solar cells and HCPV systems. This article is intended to provide an overview about the different routes being followed.

  1. Ion implantation for high performance III-V JFETS and HFETS

    SciTech Connect

    Zolper, J.C.; Baca, A.G.; Sherwin, M.E.; Klem, J.F.

    1996-06-01

    Ion implantation has been an enabling technology for realizing many high performance electronic devices in III-V semiconductor materials. We report on advances in ion implantation processing for GaAs JFETs (joint field effect transistors), AlGaAs/GaAs HFETs (heterostructure field effect transistors), and InGaP or InAlP-barrier HFETs. The GaAs JFET has required the development of shallow p-type implants using Zn or Cd with junction depths down to 35 nm after the activation anneal. Implant activation and ionization issues for AlGaAs are reported along with those for InGaP and InAlP. A comprehensive treatment of Si-implant doping of AlGaAs is given based on donor ionization energies and conduction band density-of-states dependence on Al-composition. Si and Si+P implants in InGaP are shown to achieve higher electron concentrations than for similar implants in AlGaAs due to absence of the deep donor level. An optimized P co- implantation scheme in InGaP is shown to increase the implanted donor saturation level by 65%.

  2. Reliability of III-V electronic devices -- the defects that cause the trouble

    NASA Astrophysics Data System (ADS)

    Pantelides, Sokrates T.

    2012-02-01

    Degradation of electronic devices by hot electrons is universally attributed to the generation of defects, but the mechanisms for defect generation and the specific nature of the pertinent defects are not known for most systems. Here we describe three recent case studies [1] in III-V high-electron-mobility transistors that illustrate the power of combining density functional calculations and experimental data to identify the pertinent defects and associated degradation mechanisms. In all cases, benign pre-existing defects are either depassivated (irreversible degradation) or transformed to a metastable state (reversible degradation). This work was done in collaboration with R.D. Schrimpf, D.M. Fleetwood, Y. Puzyrev, X. Shen, T. Roy, S. DasGupta, and B.R. Tuttle. Devices were provided by D.F. Brown, J. Speck and U. Mishra, and by J. Bergman and B. Brar. [4pt] [1] Y. S. Puzyrev et al., Appl. Phys. Lett. 96, 053505 (2010); T. Roy et al., Appl. Phys. Lett. 96, 133503 (2010); X. Shen et al., J. Appl. Phys. 108, 114505 (2010).

  3. Proton irradiation effects on advanced digital and microwave III-V components

    SciTech Connect

    Hash, G.L.; Schwank, J.R.; Shaneyfelt, M.R. )

    1994-12-01

    A wide range of advanced III-V components suitable for use in high-speed satellite communication systems were evaluated for displacement damage and single-event effects in high-energy, high-fluence proton environments. Transistors and integrated circuits (both digital and MMIC) were irradiated with protons at energies from 41 to 197 MeV and at fluences from 10[sup 10] to 2 [times] 10[sup 14] protons/cm[sup 2]. Large soft-error rates were measured for digital GaAs MESFET (3 [times] 10[sup [minus]5] errors/bit-day) and heterojunction bipolar circuits (10[sup [minus]5] errors/bit-day). No transient signals were detected from MMIC circuits. The largest degradation in transistor response caused by displacement damage was observed for 1.0-[mu]m depletion- and enhancement-mode MESFET transistors. Shorter gate length MESFET transistors and HEMT transistors exhibited less displacement-induced damage. These results show that memory-intensive GaAs digital circuits may result in significant system degradation due to single-event upset in natural and man-made space environments. However, displacement damage effects should not be a limiting factor for fluence levels up to 10[sup 14] protons/cm[sup 2] [equivalent to total doses in excess of 10 Mrad (GaAs)].

  4. The Development of III-V Semiconductor MOSFETs for Future CMOS Applications

    NASA Astrophysics Data System (ADS)

    Greene, Andrew M.

    Alternative channel materials with superior transport properties over conventional strained silicon are required for supply voltage scaling in low power complementary metal-oxide-semiconductor (CMOS) integrated circuits. Group III-V compound semiconductor systems offer a potential solution due to their high carrier mobility, low carrier effective mass and large injection velocity. The enhancement in transistor drive current at a lower overdrive voltage allows for the scaling of supply voltage while maintaining high switching performance. This thesis focuses on overcoming several material and processing challenges associated with III-V semiconductor development including a low thermal processing budget, high interface trap state density (Dit), low resistance source/drain contacts and growth on lattice mismatched substrates. Non-planar In0.53Ga0.47As FinFETs were developed using both "gate-first" and "gate-last" fabrication methods for n-channel MOSFETs. Electron beam lithography and anisotropic plasma etching processes were optimized to create highly scaled fins with near vertical sidewalls. Plasma damage was removed using a wet etch process and improvements in gate efficiency were characterized on MOS capacitor structures. A two-step, selective removal of the pre-grown n+ contact layer was developed for "gate-last" recess etching. The final In0.53Ga 0.47As FinFET devices demonstrated an ION = 70 mA/mm, I ON/IOFF ratio = 15,700 and sub-threshold swing = 210 mV/dec. Bulk GaSb and strained In0.36Ga0.64Sb quantum well (QW) heterostructures were developed for p-channel MOSFETs. Dit was reduced to 2 - 3 x 1012 cm-2eV-1 using an InAs surface layer, (NH4)2S passivation and atomic layer deposition (ALD) of Al2O3. A self-aligned "gate-first" In0.36Ga0.64Sb MOSFET fabrication process was invented using a "T-shaped" electron beam resist patterning stack and intermetallic source/drain contacts. Ni contacts annealed at 300°C demonstrated an ION = 166 mA/mm, ION/IOFF ratio = 1,500 and sub-threshold swing = 340 mV/dec. Split C-V measurements were used to extract an effective channel mobility of muh* = 300 cm2/Vs at Ns = 2 x 1012 cm -2. "Gate-last" MOSFETs grown with an epitaxial p + contact layer were fabricated using selective gate-recess etching techniques. A parasitic "n-channel" limited ION/I OFF ratio and sub-threshold swing, most likely due to effects from the InAs surface layer.

  5. New materials for future generations of III-V solar cells

    SciTech Connect

    Geisz, J.F.; Friedman, D.J.; Olson, J.M.; Kramer, C.; Kibbler, A.; Kurtz, S.R.

    1999-03-01

    Three- and four-junction III-V devices are proposed for ultrahigh-efficiency solar cells using a new 1-eV material lattice-matched to GaAs, namely, GaInNAs. We demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. Under the AM1.5 direct spectrum with all the light higher in energy than the GaAs band gap filtered out, the prototypes grown with base doping of about 10{sup 17}&hthinsp;cm{sup {minus}3} have open-circuit voltages ranging from 0.35 to 0.44 V, short-circuit current densities of 1.8 mA/cm{sup 2}, and fill factors from 61{percent} to 66{percent}. To improve on the current record-efficiency tandem GaInP/GaAs solar cell by adding a GaInNAs junction, the short-circuit current density of this 1-eV cell must be significantly increased. Because these low short-circuit current densities are due to short diffusion lengths, we have demonstrated a depletion-width-enhanced variation of one of the prototype devices that trades off decreased voltage for increased photocurrent, with a short-circuit current density of 7.4 mA/cm{sup 2} and an open-circuit voltage of 0.28 V. {copyright} {ital 1999 American Institute of Physics.}

  6. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Dhaka, Veer; Perros, Alexander; Naureen, Shagufta; Shahid, Naeem; Jiang, Hua; Kakko, Joona-Pekko; Haggren, Tuomas; Kauppinen, Esko; Srinivasan, Anand; Lipsanen, Harri

    2016-01-01

    Low temperature (˜200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (˜2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  7. A novel surface preparation methodology for epi-ready antimonide based III-V substrates

    NASA Astrophysics Data System (ADS)

    Dutta, P. S.; Rajagopalan, G.; Kim, H. J.; Kumar, A.

    2005-05-01

    Surfaces of GaSb substrates currently available from various commercial vendors are nowhere close to device grade GaAs, Si or InP wafer surfaces. Hence epitaxial growth and device fabrication on as-received commercial substrates poses significant difficulties amongst antimonide based researchers. Antimonide based materials are known to have poor surface oxide quality and not so well understood chemical reactions with various chemicals used to remove the oxides prior to growth. There are no existing reports on the detailed recipe for the preparation of "atomically flat and clean" surfaces that works on wafers obtained from various commercial vendors. This paper presents a detailed recipe for obtaining atomically flat and clean GaSb surfaces, irrespective of the initial polishing source. The same recipe (with slight modification) has been found to be successful with other III-V and II-VI compounds. The novel surface preparation process developed in our laboratory includes, chemical-mechanical polishing using an agglomerate-free sub-micron alumina slurry on a soft pad such as velvet, surface cleaning using dilute ammonium or potassium hydroxide-H2O solution and surfactant or glycerol, surface degreasing using organic solvents, oxide desorption using HCl-H2O and HF-H2O mixtures, mild chemical etching using ammonium sulfide and a final rinse in high purity deionized (DI) water and methanol. Using this recipe, we have been able to achieve surfaces with atomic flatness (RMS surface roughness close to 0.5 nm over a 10 x 10 mm2) and extremely clean surfaces, irrespective of the initial contamination or the sources of the wafers. Results of wafer surfaces before and after polishing using our recipe will be presented.

  8. Surface and gap intrinsic localized modes in one-dimensional III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Franchini, A.; Bortolani, V.; Wallis, R. F.

    2000-01-01

    A theoretical investigation has been made of intrinsic localized vibrational modes in an anharmonic one-dimensional diatomic lattice with alternating force constants coupling successive neighbours. This system simulates a row of atoms in the icons/Journals/Common/langle" ALT="langle" ALIGN="TOP"/> 111icons/Journals/Common/rangle" ALT="rangle" ALIGN="TOP"/> direction of a III-V semiconductor. Specific calculations have been carried out for GaN, because it has a large gap between acoustic and optical branches. We study small-amplitude atom vibrations (up to 0.4 Å), accessible to experimental detection, in order to legitimize the expansion of the full potential to include cubic and quartic terms. We consider then nearest-neighbour interactions through harmonic as well as cubic and quartic anharmonic interactions to study the interplay between cubic and quartic terms in the frequencies of the localized modes. The force constants were determined empirically by fitting the longitudinal branches in the icons/Journals/Common/Gamma" ALT="Gamma" ALIGN="TOP"/> -L direction of GaN. We have studied both gap and surface intrinsic localized modes. Zinc-blende-structure chains are of particular interest, because the lack of inversion symmetry prevents the classification of the modes as even or odd parity. Nevertheless, modes were found that closely resemble the even- or odd-parity modes of an NaCl-structure chain. Their frequencies lie inside the gap for GaN. The absence of inversion symmetry permits a variety of surface modes to exist, depending on whether the bond at the surface is strong or weak and the atom at the surface is light or heavy. All surface mode frequencies for GaN lie inside the gap as found with the use of the full potential.

  9. Radiation effects in III-V semiconductors and heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Shatalov, Alexei

    The electron, gamma and neutron radiation degradation of III-V semiconductors and heterojunction bipolar transistors (HBTs) is investigated in this thesis. Particular attention is paid to InP and InGaAs materials and InP/InGaAs abrupt single HBTs (SHBTs). Complete process sequences for fabrication of InP/ InGaAs HBTs are developed and subsequently employed to produce the devices, which are then electrically characterized and irradiated with the different types of radiation. A comprehensive analytical HBT model is developed and radiation damage calculations are performed to model the observed radiation-induced degradation of SHBTs. The most pronounced radiation effects found in SHBTs include reduction of the common-emitter DC current gain, shift of the collector-emitter (CE) offset voltage and increase of the emitter, base and collector parasitic resistances. Quantitative analysis performed using the developed model demonstrates that increase of the neutral bulk and base-emitter (BE) space charge region (SCR) components of the base current are responsible for the observed current gain degradation. The rise of the neutral bulk recombination is attributed to decrease in a Shockley-Read-Hall (SRH) carrier lifetime, while the SCR current increase is caused by rising SCR SRH recombination and activation of a tunneling-recombination mechanism. On the material level these effects are explained by displacement defects produced in a semiconductor by the incident radiation. The second primary change of the SHBT characteristics, CE offset voltage shift, is induced by degradation of the base- collector (BC) junction. The observed rise of the BC current is brought on by diffusion and recombination currents which increase as more defects are introduced in a semiconductor. Finally, the resistance degradation is attributed to deterioration of low-doped layers of a transistor, and to degradation of the device metal contacts.

  10. The Genetic Analysis of a Reciprocal Translocation, eT1(III; V), in CAENORHABDITIS ELEGANS

    PubMed Central

    Rosenbluth, Raja E.; Baillie, David L.

    1981-01-01

    The Caenorhabditis elegans mutation e873, which results in a recessive uncoordinated phenotype (formerly named Unc-72) and which had been isolated after 32P treatment (Brenner 1974), has now been found to act as a crossover suppressor and to be associated with a translocation between linkage groups (LG's) III and V. The translocation has been named, eT1(III; V); eT1 acts as a dominant crossover suppressor for both the right half of LGIII and the left half of LGV, providing a balancer for a total of 39 map units. The uncoordinated e873 phenotype has been shown to be a consequence of an inactive unc-36III gene. It was possible to demonstrate that, in translocation heterozygotes, eT1 chromosomes marked with either sma-3 or dpy-11 segregate from normal LGIII, while those marked with bli-5, sma-2 or unc-42 segregate from normal LGV. Since bli-5 and sma-2 are normally on LGIII, and dpy-11 is normally on LGV, it is concluded that: (a) eT1 is a reciprocal translocation; (b) there is a breakpoint between sma-3 and sma-2 in LGIII (the region containing unc-36) and one between dpy-11 and unc-42 in LGV; (c) there is no dominant centromere between sma-2 and bli-5 on LGIII, since in eT1 these genes are not linked to a LGIII centromere. Similarly, it is highly unlikely that there is a centromere to the left of dpy-11 on LGV. The new gene order in eT1 was determined by measuring recombination rates between markers in eT1 homozygotes. It is concluded that the new order is: dpy-1 sma-3 (break) dpy-11 unc-60, and bli-5 sma-2 (break) unc-42 unc-51.—This is the first analysis of a C. elegans translocation with respect to reciprocity, breakpoints and new gene order. PMID:6953041

  11. Ga-rich GaxIn1-xP solar cells on Si with 1.95 eV bandgap for ideal III-V/Si photovoltaics

    NASA Astrophysics Data System (ADS)

    Ratcliff, Christopher; Grassman, T. J.; Carlin, J. A.; Chmielewski, D. J.; Ringel, S. A.

    2014-03-01

    Theoretical models for III-V compound multijunction solar cells show that solar cells with bandgaps of 1.95-2.3 eV are needed to create ideal optical partitioning of the solar spectrum for device architectures containing three, four and more junctions. For III-V solar cells integrated with an active Si sub-cell, GaInP alloys in the Ga-rich regime are ideal since direct bandgaps of up to ~ 2.25 eV are achieved at lattice constants that can be integrated with appropriate GaAsP, SiGe and Si materials, with efficiencies of almost 50% being predicted using practical solar cell models under concentrated sunlight. Here we report on Ga-rich, lattice-mismatched Ga0.57In0.43P sub-cell prototypes with a bandgap of 1.95 eV grown on tensile step-graded metamorphic GaAsyP1-y buffers on GaAs substrates. The goal is to create a high bandgap top cell for integration with Si-based III-V/Si triple-junction devices. Excellent carrier collection efficiency was measured via internal quantum efficiency measurements and with their design being targeted for multijunction implementation (i.e. they are too thin for single junction cells), initial cell results are encouraging. The first generation of identical 1.95 eV cells on Si were fabricated as well, with efficiencies for these large bandgap, thin single junction cells ranging from 7% on Si to 11% on GaAs without antireflection coatings, systematically tracking the change in defect density as a function of growth substrate.

  12. Mono- and polynucleation, atomistic growth, and crystal phase of III-V nanowires under varying group V flow

    SciTech Connect

    Dubrovskii, V. G.

    2015-05-28

    We present a refined model for the vapor-liquid-solid growth and crystal structure of Au-catalyzed III-V nanowires, which revisits several assumptions used so far and is capable of describing the transition from mononuclear to polynuclear regime and ultimately to regular atomistic growth. We construct the crystal phase diagrams and calculate the wurtzite percentages, elongation rates, critical sizes, and polynucleation thresholds of Au-catalyzed GaAs nanowires depending on the As flow. We find a non-monotonic dependence of the crystal phase on the group V flow, with the zincblende structure being preferred at low and high group V flows and the wurtzite structure forming at intermediate group V flows. This correlates with most of the available experimental data. Finally, we discuss the atomistic growth picture which yields zincblende crystal structure and should be very advantageous for fabrication of ternary III-V nanowires with well-controlled composition and heterointerfaces.

  13. Vertical-coupled high-efficiency tunable III-V- CMOS SOI hybrid external-cavity laser.

    PubMed

    Lin, Shiyun; Djordjevic, Stevan S; Cunningham, John E; Shubin, Ivan; Luo, Ying; Yao, Jin; Li, Guoliang; Thacker, Hiren; Lee, Jin-Hyoung; Raj, Kannan; Zheng, Xuezhe; Krishnamoorthy, Ashok V

    2013-12-30

    We demonstrate a hybrid III-V/SOI laser by vertically coupling a III-V RSOA chip with a SOI-CMOS chip containing a tunable wavelength selective reflector. We report a waveguide-coupled wall-plug-efficiency of 5.5% and output power of 10 mW. A silicon resistor-based microheater was integrated to thermally tune a ring resonator for precise lasing wavelength control. A high tuning efficiency of 2.2 nm/mW over a range of 18 nm was achieved by locally removing the SOI handler substrate. C-band single mode lasing was confirmed with a side mode suppression ratio of 35 dB. This grating coupler based vertical integration approach can be scaled up in two dimensions for efficient multi-wavelength sources in silicon photonics. PMID:24514836

  14. Mono- and polynucleation, atomistic growth, and crystal phase of III-V nanowires under varying group V flow

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2015-05-01

    We present a refined model for the vapor-liquid-solid growth and crystal structure of Au-catalyzed III-V nanowires, which revisits several assumptions used so far and is capable of describing the transition from mononuclear to polynuclear regime and ultimately to regular atomistic growth. We construct the crystal phase diagrams and calculate the wurtzite percentages, elongation rates, critical sizes, and polynucleation thresholds of Au-catalyzed GaAs nanowires depending on the As flow. We find a non-monotonic dependence of the crystal phase on the group V flow, with the zincblende structure being preferred at low and high group V flows and the wurtzite structure forming at intermediate group V flows. This correlates with most of the available experimental data. Finally, we discuss the atomistic growth picture which yields zincblende crystal structure and should be very advantageous for fabrication of ternary III-V nanowires with well-controlled composition and heterointerfaces.

  15. Accumulation capacitance frequency dispersion of III-V metal-insulator-semiconductor devices due to disorder induced gap states

    SciTech Connect

    Galatage, R. V.; Zhernokletov, D. M.; Dong, H.; Brennan, B.; Hinkle, C. L.; Wallace, R. M.; Vogel, E. M.

    2014-07-07

    The origin of the anomalous frequency dispersion in accumulation capacitance of metal-insulator-semiconductor devices on InGaAs and InP substrates is investigated using modeling, electrical characterization, and chemical characterization. A comparison of the border trap model and the disorder induced gap state model for frequency dispersion is performed. The fitting of both models to experimental data indicate that the defects responsible for the measured dispersion are within approximately 0.8 nm of the surface of the crystalline semiconductor. The correlation between the spectroscopically detected bonding states at the dielectric/III-V interface, the interfacial defect density determined using capacitance-voltage, and modeled capacitance-voltage response strongly suggests that these defects are associated with the disruption of the III-V atomic bonding and not border traps associated with bonding defects within the high-k dielectric.

  16. Modeling Quantum and Coulomb Effects in Nanoscale Enhancement-Mode Tri-Gate III-V MOSFETs

    NASA Astrophysics Data System (ADS)

    Al-Sibiani, Sameer; Khair, Khadija; Ahmed, Shaikh

    2014-03-01

    Because of limited benefits of strain engineering in extremely scaled silicon devices and lack of demonstration of a performance gain at the product level with nanowires, nanotubes, graphene, and other exotic channel materials, there is a strong motivation to continue device scaling using high-transport III-V (such as InGaAs and InAsSb) channel materials beyond the year 2020. However, there are several challenges with III-V MOSFETs prohibiting their use in high-performance and low-power logic applications. In this work, we investigate the performance of the tri-gate III-V FETs as compared to the planar counterpart, and show how quantum size quantization and random dopant fluctuations (RDF) affect the tri-gate FET characteristics and how to curb these issues. A 3-D fully atomistic quantum-corrected Monte Carlo device simulator has been used in this work. Space-quantization effects have been accounted for via a parameter-free effective potential scheme (and benchmarked against the NEGF approach in the ballistic limit). To treat full Coulomb (electron-ion and electron-electron) interactions, the simulator implements a real-space corrected Coulomb electron dynamics (ED) scheme. Also, the essential bandstructure parameters (bandgap, effective masses, and the density-of-states) have been computed using a 20-band nearest-neighbour sp3d5s* tight-binding scheme.

  17. Nanometer-Scale Compositional Structure in III-V Semiconductor Heterostructures Characterized by Scanning Tunneling Microscopy

    SciTech Connect

    Allerman, A.A.; Bi, W.G.; Biefeld, R.M.; Tu, C.W.; Yu, E.T.; Zuo, S.L.

    1998-11-10

    Nanometer-scale compositional structure in InAsxP1.InNYAsxPl.x-Y/InP, grown by gas-source molecular-beam epitaxy and in InAsl-xPJkAsl$b#InAs heterostructures heterostructures grown by metal-organic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within (T 11) and (111) crystal planes. Similar compositional structure is observed within InNYAsxP1-x-Y alloy layers. Imaging of InAsl-xp@Asl#bY superlattices reveals nanometer-scale clustering within both the hAsI-.p and InAsl$bY alloy layers, with preferential alignment of compositional features in the direction. Instances are observed of compositional structure correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice, constant relative to the surrounding alloy material appearing to propagate across the interface.

  18. Developing high-performance III-V superlattice IRFPAs for defense: challenges and solutions

    NASA Astrophysics Data System (ADS)

    Zheng, Lucy; Tidrow, Meimei; Aitcheson, Leslie; O'Connor, Jerry; Brown, Steven

    2010-04-01

    The antimonide superlattice infrared detector technology program was established to explore new infrared detector materials and technology. The ultimate goal is to enhance the infrared sensor system capability and meet challenging requirements for many applications. Certain applications require large-format focal plane arrays (FPAs) for a wide field of view. These FPAs must be able to detect infrared signatures at long wavelengths, at low infrared background radiation, and with minimal spatial cross talk. Other applications require medium-format pixel, co-registered, dual-band capability with minimal spectral cross talk. Under the technology program, three leading research groups have focused on device architecture design, high-quality material growth and characterization, detector and detector array processing, hybridization, testing, and modeling. Tremendous progress has been made in the past few years. This is reflected in orders-of-magnitude reduction in detector dark-current density and substantial increase in quantum efficiency, as well as the demonstration of good-quality long-wavelength infrared FPAs. Many technical challenges must be overcome to realize the theoretical promise of superlattice infrared materials. These include further reduction in dark current density, growth of optically thick materials for high quantum efficiency, and elimination of FPA processing-related performance degradation. In addition, challenges in long-term research and development cost, superlattice material availability, FPA chip assembly availability, and industry sustainability are also to be met. A new program was established in 2009 with a scope that is different from the existing technology program. Called Fabrication of Superlattice Infrared FPA (FastFPA), this 4-year program sets its goal to establish U.S. industry capability of producing high-quality superlattice wafers and fabricating advanced FPAs. It uses horizontal integration strategy by leveraging existing III-V industry resources and taking advantage of years of valuable experiences amassed by the HgCdTe FPA industry. By end of the program span, three sets of FPAs will be demonstrated-a small-format long-wave FPA, a large-format long-wave FPA, and a medium-format dual-band FPA at long-wave and mid-wave infrared.

  19. Silicon, germanium, and III-V-based tunneling devices for low-power applications

    NASA Astrophysics Data System (ADS)

    Smith, Joshua T.

    While the scaling of transistor dimensions has kept pace with Moore's Law, the voltages applied to these devices have not scaled in tandem, giving rise to ever-increasing power/heating challenges in state-of-the-art integrated circuits. A primary reason for this scaling mismatch is due to the thermal limit---the 60 mV minimum required at room temperature to change the current through the device by one order of magnitude. This voltage scaling limitation is inherent in devices that rely on the mechanism of thermal emission of charge carriers over a gate-controlled barrier to transition between the ON- and OFF-states, such as in the case of conventional CMOS-based technologies. To overcome this voltage scaling barrier, several steep-slope device concepts have been pursued that have experimentally demonstrated sub-60-mV/decade operation since 2004, including the tunneling-field effect transistor (TFET), impact ionization metal-oxide-semiconductor (IMOS), suspended-gate FET (SG-FET), and ferroelectric FET (Fe-FET). These reports have excited strong efforts within the semiconductor research community toward the realization of a low-power device that will support continued scaling efforts, while alleviating the heating issues prevalent in modern computer chips. Literature is replete with claims of sub-60-mV/decade operation, but often with neglect to other voltage scaling factors that offset this result. Ideally, a low-power device should be able to attain sub-60-mV/decade inverse subthreshold slopes (S) employing low supply and gate voltages with a foreseeable path toward integration. This dissertation describes the experimental development and realization of CMOS-compatible processes to enhance tunneling efficiency in Si and Si/Ge nanowire (NW) TFETs for improved average S (S avg) and ON-currents (ION), and a novel, III-V-based tunneling device alternative is also proposed. After reviewing reported efforts on the TFET, IMOS, and SG-FET, the TFET is highlighted as the most promising low-power device candidate, owing to its potential to operate within small supply and gate voltage windows. In a critical analysis of the TFET, the advantages of 1-D systems, such as NWs, that can potentially access the so-called quantum capacitance limit (QCL) are discussed, and the remaining challenges for TFETs, such as source/channel doping abruptness, and material tradeoffs are considered. To this end, substantial performance improvements, as measured by Savg and ION, are experimentally realized in top-down fabricated Si NW-TFET arrays by systematically varying the annealing process used to enhance doping abruptness at the source/channel junction---a critical feature for maximizing tunneling efficiency. A combination of excimer laser annealing (ELA) and a low-temperature rapid thermal anneal (LT-RTA) are identified as an optimum choice, resulting in a 36% decrease in Savg as well as ˜500% improvement in ION over the conventional RTA approach. Extrapolation of these results with simulation shows that sub-60-mV/decade operation is possible on a Si-based platform for aggressively scaled, yet realistic, NW-TFET devices. Back-gated NW-FET measurements are also presented to assess the material quality of Ge/Si core/shell NW heterostructures with an n+-doped shell, and these NWs are found to be suitable building blocks for the fabrication of more efficient TFET systems, owing to the very abrupt doping profile at the shell/core (source/channel) interface and smaller bandgap/effective mass of the Ge channel. Finally, low current levels in conventional TFETs have recently led researchers to re-examine III-V heterostructures, particularly those with a broken-gap band alignment to allow a tunneling probability near unity. Along these lines, a novel tunnel-based alternative is presented---the broken-gap tunnel MOS---that enables a constant S < 60 mV/decade. The proposed device permits the use of 2-D device architectures without degradation of S given the source-controlled operation mechanism, while simultaneously avoiding undesirable nonlinearities in the output characteristics.

  20. Metabolomic and proteomic biomarkers for III-V semiconductors: Chemical-specific porphyrinurias and proteinurias

    SciTech Connect

    Fowler, Bruce A. . E-mail: bxf9@cdc.gov; Conner, Elizabeth A.; Yamauchi, Hiroshi

    2005-08-07

    A pressing need exists to develop and validate molecular biomarkers to assess the early effects of chemical agents, both individually and in mixtures. This is particularly true for new and chemically intensive industries such as the semiconductor industry. Previous studies from this laboratory and others have demonstrated element-specific alterations of the heme biosynthetic pathway for the III-V semiconductors gallium arsenide (GaAs) and indium arsenide (InAs) with attendant increased urinary excretion of specific heme precursors. These data represent an example of a metabolomic biomarker to assess chemical effects early, before clinical disease develops. Previous studies have demonstrated that the intratracheal or subcutaneous administration of GaAs and InAs particles to hamsters produces the induction of the major stress protein gene families in renal proximal tubule cells. This was monitored by 35-S methionine labeling of gene products followed by two-dimensional gel electrophoresis after exposure to InAs particles. The present studies examined whether these effects were associated with the development of compound-specific proteinuria after 10 or 30 days following subcutaneous injection of GaAs or InAs particles in hamsters. The results of these studies demonstrated the development of GaAs- and InAs-specific alterations in renal tubule cell protein expression patterns that varied at 10 and 30 days. At the 30-day point, cells in hamsters that received InAs particles showed marked attenuation of protein expression, suggesting inhibition of the stress protein response. These changes were associated with GaAs and InAs proteinuria patterns as monitored by two-dimensional gel electrophoresis and silver staining. The intensity of the protein excretion patterns increased between the 10- and 30-day points and was most pronounced for animals in the 30-day InAs treatment group. No overt morphologic signs of cell death were seen in renal tubule cells of these animals. Western blot analyses of the urines with antibodies to the 32-, 70-, and 90-kDa stress protein families did not show the presence of these molecules, indicating that these proteins were not excreted in the urine samples. These data suggest that the observed proteinuria patterns were not a result of cell death and that the observed chemical-specific proteinurias were produced before marked cellular toxicity. These findings suggest a hypothesis involving GaAs and InAs interference with stress protein chaperoning of reabsorbed proteins for proteosomic degradation and the probable chaperoning of damaged intracellular proteins from renal proximal tubule cells into the urinary filtrate. Overall, the results of these studies provide further information on the nephrotoxicity of these semiconductor compounds. They also suggest the use of two-dimensional gel electrophoresis with silver staining of urinary protein patterns as a potentially useful proteomic approach to renal damage early in relation to intracellular proteotoxicity in kidney tubule cells.

  1. Ellipsometric study of metal-organic chemically vapor deposited III-V semiconductor structures

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Sekula-Moise, Patricia A.; Sieg, Robert M.; Drotos, Mark N.; Bogner, Nancy A.

    1992-01-01

    An ellipsometric study of MOCVD-grown layers of AlGaAs and InGaAs in thick films and strained layer complex structures is presented. It is concluded that the ternary composition of thick nonstrained layers can be accurately determined to within experimental errors using numerical algorithms. In the case of complex structures, thickness of all layers and the alloy composition of nonstrained layers can be determined simultaneously, provided that the correlations between parameters is no higher than 0.9.

  2. Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006

    SciTech Connect

    Ringel, S. A.

    2008-11-01

    Goal is to demo realistic path to III-V multijunction concentrator efficiencies > 40% by substrate-engineering combining compositional grading with patterned epitaxy for small-area cells for high concentration.

  3. Thin Body III-V-Semiconductor-on-Insulator Metal-Oxide-Semiconductor Field-Effect Transistors on Si Fabricated Using Direct Wafer Bonding

    NASA Astrophysics Data System (ADS)

    Yokoyama, Masafumi; Yasuda, Tetsuji; Takagi, Hideki; Yamada, Hisashi; Fukuhara, Noboru; Hata, Masahiko; Sugiyama, Masakazu; Nakano, Yoshiaki; Takenaka, Mitsuru; Takagi, Shinichi

    2009-12-01

    We have demonstrated thin body III-V-semiconductor-on-insulator (III-V-OI) n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs) on a Si wafer fabricated using a novel direct wafer bonding (DWB) process. A 100-nm-thick InGaAs channel was successfully transferred by the low damage and low temperature DWB process using low energy electron cyclotron resonance (ECR) plasma. The transferred InGaAs-OI nMOSFET on the Si wafer exhibited a high electron channel mobility of 1200 cm2.V-1.s-1, indicating that the present DWB process allows us to form thin III-V-OI channels without serious plasma and bonding damage. This technology is expected to open up the possibility of integrating the ultrathin body III-V-OI MOSFETs on Si platform.

  4. InAsSbBi, a direct band-gap, III-V, LWIR material

    NASA Technical Reports Server (NTRS)

    Stringfellow, G. B.; Jones, Colin E.; Frodsham, John

    1990-01-01

    In the last several years Dr. Stringfellow's group at the University of Utah has reported success in incorporating over 3 percent Bi in InAs and 1.5 percent in InAsSb using Organometallic Vapor Phase Epitaxy (OMVPE) growth techniques. For InAs the lattice constant increase is linear with a=6.058+0.966x (InAs(1-x)Bi(x)), and a decrease in band gap energy of dEg / dx = -55meV / at a percentage Bi. Extrapolating this to the ternary minimum band gap at InAs(0.35)Sb(0.65), an addition of 1 to 2 percent Bi should drop the band gap to the 0.1 to 0.05eV range (10 to 20 microns). These alloys are direct band gap semiconductors making them candidates for far IR detectors. The current status of the InAsSbBi alloys is that good crystal morphology and x ray diffraction data has been obtained for up to 3.4 percent Bi. The Bi is metastable at these concentrations but the OMVPE grown material has been able to withstand the 400 C growth temperature for several hours without phase separation.

  5. III-V Ultra-Thin-Body InGaAs/InAs MOSFETs for Low Standby Power Logic Applications

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Ying

    As device scaling continues to sub-10-nm regime, III-V InGaAs/InAs metal- oxide-semiconductor ?eld-e?ect transistors (MOSFETs) are promising candidates for replacing Si-based MOSFETs for future very-large-scale integration (VLSI) logic applications. III-V InGaAs materials have low electron effective mass and high electron velocity, allowing higher on-state current at lower VDD and reducing the switching power consumption. However, III-V InGaAs materials have a narrower band gap and higher permittivity, leading to large band-to-band tunneling (BTBT) leakage or gate-induced drain leakage (GIDL) at the drain end of the channel, and large subthreshold leakage due to worse electrostatic integrity. To utilize III-V MOSFETs in future logic circuits, III-V MOSFETs must have high on-state performance over Si MOSFETs as well as very low leakage current and low standby power consumption. In this dissertation, we will report InGaAs/InAs ultra-thin-body MOSFETs. Three techniques for reducing the leakage currents in InGaAs/InAs MOSFETs are reported as described below. 1) Wide band-gap barriers: We developed AlAs0.44Sb0.56 barriers lattice-match to InP by molecular beam epitaxy (MBE), and studied the electron transport in In0.53Ga0.47As/AlAs 0.44Sb0.56 heterostructures. The InGaAs channel MOSFETs using AlAs0.44Sb0.56 bottom barriers or p-doped In0.52 Al0.48As barriers were demonstrated, showing significant suppression on the back barrier leakage. 2) Ultra-thin channels: We investigated the electron transport in InGaAs and InAs ultra-thin quantum wells and ultra-thin body MOSFETs (t ch ~ 2-4 nm). For high performance logic, InAs channels enable higher on-state current, while for low power logic, InGaAs channels allow lower BTBT leakage current. 3) Source/Drain engineering: We developed raised InGaAs and recessed InP source/drain spacers. The raised InGaAs source/drain spacers improve electrostatics, reducing subthreshold leakage, and smooth the electric field near drain, reducing BTBT leakage. With further replacement of raised InGaAs spacers by recessed, doping-graded InP spacers at high field regions, BTBT leakage can be reduced ~100:1. Using the above-mentioned techniques, record high performance InAs MOSFETs with a 2.7 nm InAs channel and a ZrO2 gate dielectric were demonstrated with Ion = 500 microA/microm at Ioff = 100 nA/microm and VDS =0.5 V, showing the highest on-state performance among all the III-V MOSFETs and comparable performance to 22 nm Si FinFETs. Record low leakage InGaAs MOSFETs with recessed InP source/drain spacers were also demonstrated with minimum I off = 60 pA/microm at 30 nm-Lg , and Ion = 150 microA/microm at I off = 1 nA/microm and VDS =0.5 V. This recessed InP source/drain spacer technique improves device scalability and enables III-V MOSFETs for low standby power logic applications. Furthermore, ultra-thin InAs channel MOSFETs were fabricated on Si substrates, exhibiting high yield and high transconductance gm ~2.0 mS/microm at 20 nm- Lg and VDS =0.5 V. With further scaling of gate lengths, a 12 nm-Lg III-V MOSFET has shown maximum Ion/Ioff ratio ~8.3x105 , confirming that III-V MOSFETs are scalable to sub-10-nm technology nodes.

  6. Raman Scattering Detection Of Elemental Group V Deposits In Native Oxides On III-V Compound Semiconductors

    NASA Astrophysics Data System (ADS)

    Schwartz, G. P.

    1981-04-01

    The application of surface reflection Raman scattering as an optical probe for monitor-ing the presence and growth of elemental deposits of group V (P,As,Sb) metalloids in native oxide films on III-V compound semiconductors is discussed. Selective data from the litera-ture concerning arsenic inclusions in native oxides on GaAs and AlxGal_xAs and red phosphor-us deposits in thermally oxidized films on InP are used to illustrate the technique.

  7. III-V-N materials for super high-efficiency multijunction solar cells

    SciTech Connect

    Yamaguchi, Masafumi; Bouzazi, Boussairi; Suzuki, Hidetoshi; Ikeda, Kazuma; Kojima, Nobuaki; Ohshita, Yoshio

    2012-10-06

    We have been studying concentrator multi-junction solar cells under Japanese Innovative Photovoltaic R and D program since FY2008. InGaAsN is one of appropriate materials for 4-or 5-junction solar cell configuration because this material can be lattice-matched to GaAs and Ge substrates. However, present InGaAsN single-junction solar cells have been inefficient because of low minority-carrier lifetime due to N-related recombination centers and low carrier mobility due to alloy scattering and non-homogeneity of N. This paper presents our major results in the understanding of majority and minority carrier traps in GaAsN grown by chemical beam epitaxy and their relationships with the poor electrical properties of the materials.

  8. Band-gap narrowing and III-V heterostructure FETs (Field-Effect Transistors)

    SciTech Connect

    Myers, D.R.; Lott, J.A.; Klem, J.F.; Tigges, C.P. ); Lowney, J.R. , Gaithersburg, MD )

    1990-01-01

    We calculate the magnitude of band-gap narrowing for GaAs-based alloys, and have included these results into one-dimensional heterojunction device models for strained In{sub 0.15}Ga{sub 0.85}As quantum-well MODulation-doped Field-Effect Transistors (MODFETs). Equivalent rigid shifts of as much as 1.2 meV are obtained for the valence band of depleted p-type Al{sub 0.15}Ga{sub 0.85}As doped at 5 {times} 10{sup 18}/cm{sup 3}. Our simulations suggest that band-gap narrowing is most significant for p-channel MODFETs. The predicted effect of band-gap narrowing in p-channel MODFETs is the formation of parasitic conduction in the low-mobility parent dopant region. The parasitic conduction would reduce the intrinsic gain. 13 refs., 4 figs.

  9. Electronic Band Structures of the Highly Desirable III-V Semiconductors: TB-mBJ DFT Studies

    NASA Astrophysics Data System (ADS)

    Rehman, Gul; Shafiq, M.; Saifullah; Ahmad, Rashid; Jalali-Asadabadi, S.; Maqbool, M.; Khan, Imad; Rahnamaye-Aliabad, H.; Ahmad, Iftikhar

    2016-05-01

    The correct band gaps of semiconductors are highly desirable for their effective use in optoelectronic and other photonic devices. However, the experimental and theoretical results of the exact band gaps are quite challenging and sometimes tricky. In this article, we explore the electronic band structures of the highly desirable optical materials, III-V semiconductors. The main reason of the ineffectiveness of the theoretical band gaps of these compounds is their mixed bonding character, where large proportions of electrons reside outside atomic spheres in the intestinal regions, which are challenging for proper theoretical treatment. In this article, the band gaps of the compounds are revisited and successfully reproduced by properly treating the density of electrons using the recently developed non-regular Tran and Blaha's modified Becke-Johnson (nTB-mBJ) approach. This study additionally suggests that this theoretical scheme could also be useful for the band gap engineering of the III-V semiconductors. Furthermore, the optical properties of these compounds are also calculated and compared with the experimental results.

  10. DX centers in III-V semiconductors under hydrostatic pressure. [GaAs:Si; InP:S

    SciTech Connect

    Wolk, J.A.

    1992-11-01

    DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si[sub Ga] shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity.

  11. A direct thin-film path towards low-cost large-area III-V photovoltaics

    PubMed Central

    Kapadia, Rehan; Yu, Zhibin; Wang, Hsin-Hua H.; Zheng, Maxwell; Battaglia, Corsin; Hettick, Mark; Kiriya, Daisuke; Takei, Kuniharu; Lobaccaro, Peter; Beeman, Jeffrey W.; Ager, Joel W.; Maboudian, Roya; Chrzan, Daryl C.; Javey, Ali

    2013-01-01

    III-V photovoltaics (PVs) have demonstrated the highest power conversion efficiencies for both single- and multi-junction cells. However, expensive epitaxial growth substrates, low precursor utilization rates, long growth times, and large equipment investments restrict applications to concentrated and space photovoltaics (PVs). Here, we demonstrate the first vapor-liquid-solid (VLS) growth of high-quality III-V thin-films on metal foils as a promising platform for large-area terrestrial PVs overcoming the above obstacles. We demonstrate 1–3 μm thick InP thin-films on Mo foils with ultra-large grain size up to 100 μm, which is ~100 times larger than those obtained by conventional growth processes. The films exhibit electron mobilities as high as 500 cm2/V-s and minority carrier lifetimes as long as 2.5 ns. Furthermore, under 1-sun equivalent illumination, photoluminescence efficiency measurements indicate that an open circuit voltage of up to 930 mV can be achieved, only 40 mV lower than measured on a single crystal reference wafer. PMID:23881474

  12. Novel hybrid III-V/II-VI mid-infrared laser structures with high asymmetric band offset confinements

    NASA Astrophysics Data System (ADS)

    Yakovlev, Yury P.; Ivanov, Sergey V.; Moiseev, Konstantin D.; Monakhov, Andrei M.; Solov'ev, Victor A.; Sedova, Irina V.; Terent'ev, Yakov V.; Toropov, Alexei A.; Mikhailova, Maya P.; Meltzer, Boris Y.; Kop'ev, Petr S.

    2002-05-01

    We present a novel hybrid laser structure based on III-V and II-VI compounds combining some advantages of type I and type II heterojunctions in one heterostructure. Such design allows the achievement of large energy offsets at the interface in the conduction and the valence band exceeding of 1.0 eV in order to provide good electron and hole confinement. P-AlAsSb/n-InAs/N-Cd(Mg)Se laser heterostructures were grown on p-InAs substrates by original technology of MBE method in two separate growth chambers consequently. Photoluminescence spectra included tow emission bands at hv=0.41 eV and hv=2.08 eV associated with InAs and CdMgSe bulk recombination transitions, respectively. Intense electroluminescence was observed at (lambda) =2.73micrometers (77K) and (lambda) =3.12micrometers (300K). Weak temperature dependence of spontaneous emission indicated the effective carrier confinement in the InAs layer due to large potential barriers ((Delta) sEc=1.28eV and (Delta) EV=1.68eV). Proposed hybrid III-V/II-VI heterostructure is very promising for creation the mid-infrared lasers with improved performances operating in the spectral range of 3- 5micrometers .

  13. A direct thin-film path towards low-cost large-area III-V photovoltaics

    NASA Astrophysics Data System (ADS)

    Kapadia, Rehan; Yu, Zhibin; Wang, Hsin-Hua H.; Zheng, Maxwell; Battaglia, Corsin; Hettick, Mark; Kiriya, Daisuke; Takei, Kuniharu; Lobaccaro, Peter; Beeman, Jeffrey W.; Ager, Joel W.; Maboudian, Roya; Chrzan, Daryl C.; Javey, Ali

    2013-07-01

    III-V photovoltaics (PVs) have demonstrated the highest power conversion efficiencies for both single- and multi-junction cells. However, expensive epitaxial growth substrates, low precursor utilization rates, long growth times, and large equipment investments restrict applications to concentrated and space photovoltaics (PVs). Here, we demonstrate the first vapor-liquid-solid (VLS) growth of high-quality III-V thin-films on metal foils as a promising platform for large-area terrestrial PVs overcoming the above obstacles. We demonstrate 1-3 μm thick InP thin-films on Mo foils with ultra-large grain size up to 100 μm, which is ~100 times larger than those obtained by conventional growth processes. The films exhibit electron mobilities as high as 500 cm2/V-s and minority carrier lifetimes as long as 2.5 ns. Furthermore, under 1-sun equivalent illumination, photoluminescence efficiency measurements indicate that an open circuit voltage of up to 930 mV can be achieved, only 40 mV lower than measured on a single crystal reference wafer.

  14. Material growth and characterization directed toward improving III-V heterojunction solar cells

    NASA Technical Reports Server (NTRS)

    Stefanakos, E. K.; Alexander, W. E.; Collis, W.; Abul-Fadl, A.

    1979-01-01

    In addition to the existing materials growth laboratory, the photolithographic facility and the device testing facility were completed. The majority of equipment for data acquisition, solar cell testing, materials growth and device characterization were received and are being put into operation. In the research part of the program, GaAs and GaA1As layers were grown reproducibly on GaAs substrates. These grown layers were characterized as to surface morphology, thickness and thickness uniformity. The liquid phase epitaxial growth process was used to fabricate p-n junctions in Ga(1-x)A1(x)As. Sequential deposition of two alloy layers was accomplished and detailed analysis of the effect of substrate quality and dopant on the GaA1As layer quality is presented. Finally, solar cell structures were formed by growing a thin p-GaA1As layer upon an epitaxial n-GaA1As layer. The energy gap corresponding to the long wavelength cutoff of the spectral response characteristic was 1.51-1.63 eV. Theoretical calculations of the spectral response were matched to the measured response.

  15. Toward the Development of Group III-V Photodetectors and Imaging Arrays

    NASA Technical Reports Server (NTRS)

    Wickenden, Dennis K.

    2003-01-01

    A collaboration between researchers at NASA Goddard Space Flight Center (GSFC) (Code 718.1) and the Johns Hopkins University Applied Physics Laboratory (APL) on the development of gallium nitride (GaN) based photodetectors has been in existence since July 1994. This collaboration, based on APL undertaking the material growth and GSFC undertaking the device processing, has led to discrete GaN photoconductive detectors with superior characteristics to those of similar devices reported in the literature and, more recently, to the development of state-of-the art 256x256 imaging arrays with the pixels indium bump-bonded to a silicon readout circuit (RIOC). The object of this proposal is to continue the collaboration for the period 1998-2002 by outlining a program of work at the APL on the metalorganic chemical vapor deposition (MOCVD) growth of GaN and related materials for UV detector applications. In particular, emphasis will be placed on the optimization of growth on 2 in diameter substrates, on the growth of In(sub x)Ga(1-x)N and Al(sub x)Ga(1-x)N alloy structures to produce devices with a wider range of tailored cut-off wavelengths, and on the growth of pn-junction structures for photovoltaic devices.

  16. Nucleation, Growth, and Strain Relaxation of Lattice-Mismatched III-V Semiconductor Epitaxial Layers

    NASA Technical Reports Server (NTRS)

    Welser, R. E.; Guido, L. J.

    1994-01-01

    We have investigated the early stages of evolution of highly strained 2-D InAs layers and 3-D InAs islands grown by metal-organic chemical vapor deposition (MOCVD) on (100) and (111) B GaAs substrates. The InAs epilayer / GaAs substrate combination has been chosen because the lattice-mismatch is severe (approx. 7.20%), yet these materials are otherwise very similar. By examining InAs-on-GaAs composites Instead of the more common In(x)Ga(1-x)As alloy, we remove an additional degree of freedom (x) and thereby simplify data interpretation. A matrix of experiments is described in which the MOCVD growth parameters -- susceptor temperature, TMIn flux, and AsH3 flux -- have been varied over a wide range. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and electron microprobe analysis have been employed to observe the thin film surface morphology. In the case of 3-D growth, we have extracted activation energies and power-dependent exponents that characterize the nucleation process. As a consequence, optimized growth conditions have been identified for depositing approx. 250 A thick (100) and (111)B oriented InAs layers with relatively smooth surfaces. Together with preliminary data on the strain relaxation of these layers, the above results on the evolution of thin InAs films indicate that the (111)B orientation is particularly promising for yielding lattice-mismatched films that are fully relaxed with only misfit dislocations at the epilayer / substrate interface.

  17. Iii-V Compound Multiple Quantum Well Based Modulator and Switching Devices.

    NASA Astrophysics Data System (ADS)

    Hong, Songcheol

    A general formalism to study the absorption and photocurrent in multiple quantum well is provided with detailed consideration of quantum confined Stark shift, exciton binding energy, line broadening, tunneling, polarization, and strain effects. Results on variation of exciton size, binding energies and transition energies as a function electric field and well size have been presented. Inhomogeneous line broadening of exciton lines due to interface roughness, alloy disorder and well to well size fluctuation is calculated. The potential of material tailoring by introducing strain for specific optical response is discussed. Theoretical and experimental results on excitonic and band-to-band absorption spectra in strained multi-quantum well structures are shown. I also report on polarization dependent optical absorption for excitonic and interband transitions in lattice matched and strained multiquantum well structures in presence of transverse electric field. Photocurrent in a p-i(MQW)-n diode with monochromatic light is examined with respect to different temperatures and intensities. The negative resistance of I-V characteristic of the p-i-n diode is based on the quantum confined Stark effect of the heavy hole excitonic transition in a multiquantum well. This exciton based photocurrent characteristic allows efficient switching. A general purpose low power optical logic device using the controller-modulator concept bas been proposed and realized. The controller is a heterojunction phototransistor with multiquantum wells in the base-collector depletion region. This allows an amplified photocurrent controlled voltage feedback with low light intensity levels. Detailed analysis of the sensitivity of this device in various modes of operation is studied. Studies are also presented on the cascadability of the device as well as its integrating -thresholding properties. A multiquantum well heterojunction bipolar transistor (MHBT), which has N^+ -p^+-i(MQW)-N structure has been fabricated to test the concept. Gain (>30) is obtained in the MBE grown devices and efficient switching occurs due to the amplification of the exciton based photocurrent. The level shift operation of the base contacted MHBT are demonstrated.

  18. Performance Evaluation of III-V Hetero/Homojunction Esaki Tunnel Diodes on Si and Lattice Matched Substrates

    NASA Astrophysics Data System (ADS)

    Thomas, Paul M.

    Understanding of quantum tunneling phenomenon in semiconductor systems is increasingly important as CMOS replacement technologies are investigated. This work studies a variety of heterojunction materials and types to increase tunnel currents to CMOS competitive levels and to understand how integration onto Si substrates affects performance. Esaki tunnel diodes were grown by Molecular Beam Epitaxy (MBE) on Si substrates via a graded buffer and control Esaki tunnel diodes grown on lattice matched substrates for this work. Peak current density for each diode is extracted and benchmarked to build an empirical data set for predicting diode performance. Additionally, statistics are used as tool to show peak to valley ratio for the III-V on Si sample and the control perform similarly below a threshold area. This work has applications beyond logic, as multijunction solar cell, heterojunction bipolar transistor, and light emitting diode designs all benefit from better tunnel contact design.

  19. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1994-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  20. Effects of proton irradiation on luminescence and carrier dynamics of self-assembled III-V quatum dots

    NASA Technical Reports Server (NTRS)

    Leon, R.; Marcinkevicius, S.; Siegert, J.; Magness, B.; Taylor, W.; Lobo, C.

    2002-01-01

    The effects of proton irradiation (1.5 MeV) on photoluminescence intensities and carrier dynamics were compared between III-V quantum dots and similar quantum well structures. A significant enhancement in radiation tolerance is seen with three-dimensional quantum confinement. Measurements were carried out in different quantum dot (QD) structures, varying in material (InGaAs/GaAs and InAlAs/AlGaAs), QD surface density (4x10^8 to 3x10'^10 cm^-2), and substrate orientation [(100) and (311) B]. Similar trends were observed for all QD samples. A slight increase in PL emission after low to intermediate proton doses, are also observed in InGaAs/GaAs (100) QD structures. The latter is explained in terms of more efficient carrier transfer from the wetting layer via radiation-induced defects.

  1. Influence of plasma composition on reflectance anisotropy spectra for in situ III-V semiconductor dry-etch monitoring

    NASA Astrophysics Data System (ADS)

    Barzen, Lars; Kleinschmidt, Ann-Kathrin; Strassner, Johannes; Doering, Christoph; Fouckhardt, Henning; Bock, Wolfgang; Wahl, Michael; Kopnarski, Michael

    2015-12-01

    Reflectance anisotropy spectroscopy (RAS) can be used to monitor (reactive) ion etching (RIE) of semiconductor samples. We present results on the influence of the Cl2 content of the plasma gas on the RAS spectra during reactive ion etching. In a first step GaAs samples have been used and the RAS spectra are compared to results of secondary ion mass spectrometry (SIMS) on sample surfaces and depth profiles. In a second step a III-V semiconductor multilayer system has been investigated using the time-evolution of the average reflected intensity as an indication for the etch rate. In both cases usually even a high amount of Cl2 does not disturb the surface-sensitivity of the RAS signal.

  2. Electron-hole contribution to the apparent s-d exchange interaction in III-V dilute magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Śliwa, Cezary; Dietl, Tomasz

    2008-10-01

    Spin splitting of photoelectrons in p -type and electrons in n -type III-V Mn-based diluted magnetic semiconductors is studied theoretically. It is demonstrated that the unusual sign and magnitude of the apparent s-d exchange integral reported for GaAs:Mn arises from exchange interactions between electrons and holes bound to Mn acceptors. This interaction dominates over the coupling between electrons and Mn spins, so far regarded as the main source of spin-dependent phenomena. A reduced magnitude of the apparent s-d exchange integral found in n -type materials is explained by the presence of repulsive Coulomb potentials at ionized Mn acceptors and a bottleneck effect.

  3. Molecular beam epitaxy engineered III-V semiconductor structures for low-power optically addressed spatial light modulators

    NASA Technical Reports Server (NTRS)

    Larsson, Anders G.; Maserjian, Joseph

    1992-01-01

    Device approaches are investigated for optically addressed SLMs based on molecular-beam epitaxy (MBE) engineered III-V materials and structures. Strong photooptic effects can be achieved in periodically delta-doped multiple-quantum-well structures, but are still insufficient for high-contrast modulation with only single- or double-pass absorption through active layers of practical thickness. The asymmetric Fabry-Perot cavity approach is employed to permit extinction of light due to interference of light reflected from the front and back surfaces of the cavity. This approach is realized with an all-MBE-grown structure consisting of GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror and the GaAs surface as the low reflectance mirror. High-contrast modulation is achieved using a low-power InGaAs/GaAs quantum well laser for the control signal.

  4. Multi-Band and Broad-Band Infrared Detectors Based on III-V Materials for Spectral Imaging Instruments

    NASA Technical Reports Server (NTRS)

    Bandara, S. V.; Gunapala, S. D.; Liu, J. K.; Rafol, S. B.; Hill, C. J.; Ting, D. Z.; Mumolo, J. M.; Trinh, T. Q.

    2005-01-01

    Quantum well infrared photodetector technology has shown remarkable success by realizing large-format focal plane arrays in both broad-bands and in multi-bands. The spectral response of these detectors based on the III-V material system are tailorable within the mid and long wavelength IR bands (similar to 3-25 mu m) and possibly beyond. Multi-band and broad-band detector arrays have been developed by vertically integrating stacks of multi quantum wells tailored for response in different wavelengths bands. Each detector stack absorbs photons within the specified wavelength band while allowing the transmission other photons, thus efficiently permitting multiband detection. Flexibility in many design parameters of these detectors allows for tuning and tailoring the spectral shape according to application requirements, specifically for spectral imaging instruments.

  5. Comprehensive comparison and experimental validation of band-structure calculation methods in III-V semiconductor quantum wells

    NASA Astrophysics Data System (ADS)

    Zerveas, George; Caruso, Enrico; Baccarani, Giorgio; Czornomaz, Lukas; Daix, Nicolas; Esseni, David; Gnani, Elena; Gnudi, Antonio; Grassi, Roberto; Luisier, Mathieu; Markussen, Troels; Osgnach, Patrik; Palestri, Pierpaolo; Schenk, Andreas; Selmi, Luca; Sousa, Marilyne; Stokbro, Kurt; Visciarelli, Michele

    2016-01-01

    We present and thoroughly compare band-structures computed with density functional theory, tight-binding, k · p and non-parabolic effective mass models. Parameter sets for the non-parabolic Γ, the L and X valleys and intervalley bandgaps are extracted for bulk InAs, GaAs and InGaAs. We then consider quantum-wells with thickness ranging from 3 nm to 10 nm and the bandgap dependence on film thickness is compared with experiments for In0.53Ga0.47 As quantum-wells. The impact of the band-structure on the drain current of nanoscale MOSFETs is simulated with ballistic transport models, the results provide a rigorous assessment of III-V semiconductor band structure calculation methods and calibrated band parameters for device simulations.

  6. Iii-v semiconductor quantum-well lasers and related opto-electronic devices on silicon. Technical report

    SciTech Connect

    Holonyak, N.; Hsieh, K.C.; Stillman, G.E.

    1989-12-01

    The research goal is to further develop quantum well heterostructure (QWH) lasers and to realize reliable Al(x)Ga(1-x)As-GaAs QWH lasers on Si. In spite of the significant lattice and thermal expansion mismatch between GaAs and Si, the idea of splicing III-V semiconductor technology, i.e., optoelectronics and photonics, onto Si has obvious appeal. Adding to this is the fact, as shown earlier in this work, that cw 300 K Al(x)Ga(1-x)As-GaAs QWH lasers can be grown on Si, and that the Si substrate serves as a better heat sink than GaAs. This makes possible the right-side-up heat sinking needed for electronic-photonic integrated circuits. This report contains research results on quantum well heterostructures on Si, impurity-induced layer disordering, phonon-assisted laser operations and other laser studies.

  7. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1995-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  8. Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose

    PubMed Central

    2014-01-01

    In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed ~ 36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 μg/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7 ± 0.1. The maximum removal efficiency of both arsenic species was obtained at pH = 5 ± 0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

  9. High-Throughput Multiple Dies-to-Wafer Bonding Technology and III/V-on-Si Hybrid Lasers for Heterogeneous Integration of Optoelectronic Integrated Circuits

    NASA Astrophysics Data System (ADS)

    Luo, Xianshu; Cao, Yulian; Song, Junfeng; Hu, Xiaonan; Cheng, Yungbing; Li, Chengming; Liu, Chongyang; Liow, Tsung-Yang; Yu, Mingbin; Wang, Hong; Wang, Qijie; Lo, Patrick Guo-Qiang

    2015-04-01

    Integrated optical light source on silicon is one of the key building blocks for optical interconnect technology. Great research efforts have been devoting worldwide to explore various approaches to integrate optical light source onto the silicon substrate. The achievements so far include the successful demonstration of III/V-on-Si hybrid lasers through III/V-gain material to silicon wafer bonding technology. However, for potential large-scale integration, leveraging on mature silicon complementary metal oxide semiconductor (CMOS) fabrication technology and infrastructure, more effective bonding scheme with high bonding yield is in great demand considering manufacturing needs. In this paper, we propose and demonstrate a high-throughput multiple dies-to-wafer (D2W) bonding technology which is then applied for the demonstration of hybrid silicon lasers. By temporarily bonding III/V dies to a handle silicon wafer for simultaneous batch processing, it is expected to bond unlimited III/V dies to silicon device wafer with high yield. As proof-of-concept, more than 100 III/V dies bonding to 200 mm silicon wafer is demonstrated. The high performance of the bonding interface is examined with various characterization techniques. Repeatable demonstrations of 16-III/V-die bonding to pre-patterned 200 mm silicon wafers have been performed for various hybrid silicon lasers, in which device library including Fabry-Perot (FP) laser, lateral-coupled distributed feedback (LC-DFB) laser with side wall grating, and mode-locked laser (MLL). From these results, the presented multiple D2W bonding technology can be a key enabler towards the large-scale heterogeneous integration of optoelectronic integrated circuits (H-OEIC).

  10. Impact of photon recycling and luminescence coupling on III-V single and dual junction photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Walker, Alexandre W.; Höhn, Oliver; Micha, Daniel N.; Wagner, Lukas; Helmers, Henning; Bett, Andreas W.; Dimroth, Frank

    2015-01-01

    Modeling single junction solar cells composed of III-V semiconductors such as GaAs with the effects of photon recycling yields insight into design and material criteria required for high efficiencies. For a thin-film single junction GaAs cell to reach 28.5% efficiency, simulation results using a recently developed model which accounts for photon recycling indicate that Shockley-Read-Hall (SRH) lifetimes of electrons and holes must be longer than 3 and 1 μs, respectively, in a 2-μm thin active region, and that the native substrate must be removed such that the cell is coupled to a highly reflective rear-side mirror. The model is generalized to account for luminescence coupling in tandem devices, which yields direct insight into the top cell's nonradiative lifetimes. A heavily current mismatched GaAs/GaAs tandem device is simulated and measured experimentally as a function of concentration between 3 and 100 suns. The luminescence coupling increases from 14% to 33% experimentally, whereas the model requires increasing electron and hole SRH lifetimes to explain these results. This could be an indication of the saturating defects which mediate the SRH process. However, intermediate GaAs layers between the two subcells may also contribute to the luminescence coupling as a function of concentration.

  11. Proteomic and metabolomic biomarkers for III-V semiconductors: And prospects for application to nano-materials

    SciTech Connect

    Fowler, Bruce A. Conner, Elizabeth A.; Yamauchi, Hiroshi

    2008-11-15

    There has been an increased appreciation over the last 20 years that chemical agents at very low dose levels can produce biological responses in protein expression patterns (proteomic responses) or alterations in sensitive metabolic pathways (metabolomic responses). Marked improvements in analytical methodologies, such as 2-D gel electrophoresis, matrix-assisted laser desorption-time of flight (MALDI-TOF) and surface enhanced laser desorption-time of flight (SELDI-TOF) technologies are capable of identifying specific protein patterns related to exposure to chemicals either alone or as mixtures. The detection and interpretation of early cellular responses to chemical agents have also made great advances through correlative ultrastructural morphometric and biochemical studies. Similarly, advances in analytical technologies such as HPLC, proton NMR, MALDI-TOF, and SELDI-TOF have permitted early detection of changes in a number of essential metabolic pathways following chemical exposures by measurement of alterations in metabolic products from those pathways. Data from these approaches are increasingly regarded as potentially useful biomarkers of chemical exposure and early cellular responses. Validation and establishment of linkages to biological outcomes are needed in order for biomarkers of effect to be established. This short review will cover a number of the above techniques and report data from chemical exposures to two binary III-V semiconductor compounds to illustrate gender differences in proteomic responses. In addition, the use of these methodologies in relation to rapid safety evaluations of nanotechnology products will be discussed. (Supported in part by NIH R01-ES4879)

  12. Covalent Attachment to GaP(110) - Engineering the Chemical Functionalization of a III-V Semiconductor

    NASA Astrophysics Data System (ADS)

    Bradley, A. J.; Ugeda, M. M.; Liu, Wenjun; Yu, Min; Tilley, T. Don; Pérez, Rubén; Neaton, Jeffrey B.; Crommie, M. F.

    2014-03-01

    With its 2.3 eV bulk bandgap, relatively high conduction band edge, and low chemical reactivity, the (110) surface of GaP is an excellent candidate for many UV and visible light applications, such as photo-catalysis and light-induced chemical reduction. However, the reconstruction and resulting charge transfer of the surface makes it difficult to covalently attach the required molecules. Indeed, very little work has been done to understand either covalent functionalization or passivation of this surface. Here we report on a Staudinger-type, thermally-driven covalent attachment of perfluorophenyl azide (pfpa) to GaP(110). We have studied the adsorption of pfpa molecules by means of high-resolution scanning tunneling microscopy and spectroscopy in combination with first principles calculations. We show a progression from a physisorbed state at room temperature to a covalently attached state after exposure to slightly higher temperatures (~ 50°C). The developed approach is expected to be valid for various other functional groups attached to the azide, as well as other III-V semiconductors.

  13. Ab initio calculation of natural band offsets of all group IV, II-VI and III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Wei, Su-Huai; Walsh, Aron; Li, Yong-Hua; Gong, Xingao

    2010-03-01

    The natural band offset between semiconductors is one of the most fundamental properties in materials physics. It is a necessary quantity to assess charge transport and quantum confinement, and is of particular relevance to the design of optoelectronic devices which feature an interface between two or more materials. However, in the past, the natural band offset calculations were based on the assumption that certain reference levels (core levels, average Coulomb potentials, etc.) have zero absolute deformation potential, and thus align between the bulk and heterostructures. In this study [1], using an all-electron band structure approach, we have systematically calculated the natural band offsets between all group IV, III-V and II-VI semiconductor compounds, taking into account the deformation potential of the core states. This revised approach removes assumptions regarding the deformation potential of the reference levels, and offers a more reliable prediction of the `natural' unstrained offsets. Comparison is made to experimental work, where a noticeable improvement is found compared to previous methodologies. [1] Y.-H. Li et al., Appl. Phys. Lett. 94, 212109 (2009).

  14. Predicted Growth of Two-Dimensional Topological Insulator Thin Films of III-V Compounds on Si(111) Substrate

    DOE PAGESBeta

    Yao, Liang-Zi; Crisostomo, Christian P.; Yeh, Chun-Chen; Lai, Shu-Ming; Huang, Zhi-Quan; Hsu, Chia-Hsiu; Chuang, Feng-Chuan; Lin, Hsin; Bansil, Arun

    2015-11-05

    We have carried out systematic first-principles electronic structure computations of growth of ultrathin films of compounds of group III (B, Al, In, Ga, and Tl) with group V (N, P, As, Sb, and Bi) elements on Si(111) substrate, including effects of hydrogenation. Two bilayers (BLs) of AlBi, InBi, GaBi, TlAs, and TlSb are found to support a topological phase over a wide range of strains, in addition to BBi, TlN, and TlBi which can be driven into the nontrivial phase via strain. A large band gap of 134 meV is identified in hydrogenated 2 BL film of InBi. One andmore » two BL films of GaBi and 2 BL films of InBi and TlAs on Si(111) surface possess nontrivial phases with a band gap as large as 121 meV in the case of 2 BL film of GaBi. Persistence of the nontrivial phase upon hydrogenations in the III-V thin films suggests that these films are suitable for growing on various substrates.« less

  15. Predicted Growth of Two-Dimensional Topological Insulator Thin Films of III-V Compounds on Si(111) Substrate

    SciTech Connect

    Yao, Liang-Zi; Crisostomo, Christian P.; Yeh, Chun-Chen; Lai, Shu-Ming; Huang, Zhi-Quan; Hsu, Chia-Hsiu; Chuang, Feng-Chuan; Lin, Hsin; Bansil, Arun

    2015-11-05

    We have carried out systematic first-principles electronic structure computations of growth of ultrathin films of compounds of group III (B, Al, In, Ga, and Tl) with group V (N, P, As, Sb, and Bi) elements on Si(111) substrate, including effects of hydrogenation. Two bilayers (BLs) of AlBi, InBi, GaBi, TlAs, and TlSb are found to support a topological phase over a wide range of strains, in addition to BBi, TlN, and TlBi which can be driven into the nontrivial phase via strain. A large band gap of 134 meV is identified in hydrogenated 2 BL film of InBi. One and two BL films of GaBi and 2 BL films of InBi and TlAs on Si(111) surface possess nontrivial phases with a band gap as large as 121 meV in the case of 2 BL film of GaBi. Persistence of the nontrivial phase upon hydrogenations in the III-V thin films suggests that these films are suitable for growing on various substrates.

  16. Ion beam nanopatterning of III-V semiconductors: consistency of experimental and simulation trends within a chemistry-driven theory

    NASA Astrophysics Data System (ADS)

    El-Atwani, O.; Norris, S. A.; Ludwig, K.; Gonderman, S.; Allain, J. P.

    2015-12-01

    Several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends on several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.

  17. Transforming common III-V/II-VI insulating building blocks into topological heterostructure via the intrinsic electric polarization

    NASA Astrophysics Data System (ADS)

    Zunger, Alex; Zhang, Xiuwen; Abdalla, Leonardo; Liu, Qihang

    Currently known topological insulators (TIs) are limited to narrow gap compounds incorporating heavy elements, thus severely limiting the material pool available for such applications. We show how a heterovalent superlattice made of common semiconductor building blocks can transform its non-TI components into a topological heterostructure. The heterovalent nature of such interfaces sets up, in the absence of interfacial atomic exchange, a natural internal electric field that along with the quantum confinement leads to band inversion, transforming these semiconductors into a topological phase while also forming a giant Rashba spin splitting. We demonstrate this paradigm of designing TIs from ordinary semiconductors via first-principle calculations on III-V/II-VI superlattice InSb/CdTe. We illustrate the relationship between the interfacial stability and the topological transition, finding a ``window of opportunity'' where both conditions can be optimized. This work illustrates the general principles of co-evaluation of TI functionality with thermodynamic stability as a route of identifying realistic combination of common insulators that could produce topological heterostructures. This work was supported by Basic Energy Science, MSE division (Grant DE-FG02-13ER46959).

  18. New three-layer antireflection/surface passivating coating for high efficiency III-V compound solar cells

    SciTech Connect

    Moulot, J.; Faur, M.; Goradia, C.; Goradia, M.; Faur, M.; Alterovitz, S.; Bailey, S.

    1996-12-31

    By using a chemically grown In(PO{sub 3}){sub 3}-rich oxide layer as the first layer of a 3-layer AR coating, with Al{sub 2}O{sub 3} and MgF{sub 2} as the second and third layers, the authors have addressed the problem of surface passivation and AR coating on InP solar cells. They have designed a 3-layer optimized AR coating for p{sup +}n InP solar cell, which reduces the average reflectance on the surface of cell from about 40% (bare) to less than 2%. At the same time the AR coating significantly improves the J{sub SC} and V{sub OC} by passivating the top surface of the emitter. The authors believe that the significant front surface passivation is to a large extent responsible for their achieving the record high AM0, 25 C, open-circuit voltage of 890.3 mV on a thermally diffused p{sup +}n InP(Cd,S) solar cell. This concept of using a passivating chemically grown oxide as the first layer of a multilayer AR coating can be beneficial to other III-V compound solar cells as well.

  19. Ion beam nanopatterning of III-V semiconductors: Consistency of experimental and simulation trends within a chemistry-driven theory

    SciTech Connect

    El-Atwani, O.; Norris, S. A.; Ludwig, K.; Gonderman, S.; Allain, J. P.

    2015-12-16

    In this study, several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends on several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.

  20. Nonradiative lifetime extraction using power-dependent relative photoluminescence of III-V semiconductor double-heterostructures

    NASA Astrophysics Data System (ADS)

    Walker, A. W.; Heckelmann, S.; Karcher, C.; Höhn, O.; Went, C.; Niemeyer, M.; Bett, A. W.; Lackner, D.

    2016-04-01

    A power-dependent relative photoluminescence measurement method is developed for double-heterostructures composed of III-V semiconductors. Analyzing the data yields insight into the radiative efficiency of the absorbing layer as a function of laser intensity. Four GaAs samples of different thicknesses are characterized, and the measured data are corrected for dependencies of carrier concentration and photon recycling. This correction procedure is described and discussed in detail in order to determine the material's Shockley-Read-Hall lifetime as a function of excitation intensity. The procedure assumes 100% internal radiative efficiency under the highest injection conditions, and we show this leads to less than 0.5% uncertainty. The resulting GaAs material demonstrates a 5.7 ± 0.5 ns nonradiative lifetime across all samples of similar doping (2-3 × 1017 cm-3) for an injected excess carrier concentration below 4 × 1012 cm-3. This increases considerably up to longer than 1 μs under high injection levels due to a trap saturation effect. The method is also shown to give insight into bulk and interface recombination.

  1. Novel Asymmetric III-V/II-VI Hybrid Heterostructures for High-Power Mid-Infrared Laser

    NASA Astrophysics Data System (ADS)

    Yakovlev, Yury

    2002-06-01

    This report results from a contract tasking Ioffe Institute as follows: The main objectives of the proposal include technological, structural, theoretical and electro-optical studies of the novel asymmetric III-VIII-VI hybrid heterostructures and fabrication of these structures as mid-infrared lasers. We are proposing a new physical approach consisting of combining III-V and II-VI compounds in the one hybrid asymmetric laser structure based on Al(Ga)SbAs/InAs/ Cd(Mg)Se which will lead to large conduction and valence band offsets (in excess of 1 eV for both cases) providing strong carrier and good optical confinement. It will provide suppression of carrier losses from the active region of the laser and leads to better quantum efficiency and weaker temperature dependence of the threshold current of the new laser structure. Additionally, as an alternative approach, GaInAsSb/InAsSbP asymmetric laser structures with high P content (more than 40%) will be grown by MOCVD and studied. Theoretical calculations of this new laser design will be performed. The main parameters of the novel hybrid III-VIII-VI mid-IR laser structure (temperature dependence of threshold current, spontaneous and coherent emission spectra, optical power in pulsed and cw mode) will be investigated. Such lasers should have applications to optical communication through the atmosphere, and materials processing.

  2. Ion beam nanopatterning of III-V semiconductors: consistency of experimental and simulation trends within a chemistry-driven theory

    PubMed Central

    El-Atwani, O.; Norris, S. A.; Ludwig, K.; Gonderman, S.; Allain, J. P.

    2015-01-01

    Several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends on several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades. PMID:26670948

  3. III-V tri-gate quantum well MOSFET: Quantum ballistic simulation study for 10 nm technology and beyond

    NASA Astrophysics Data System (ADS)

    Datta, Kanak; Khosru, Quazi D. M.

    2016-04-01

    In this work, quantum ballistic simulation study of a III-V tri-gate MOSFET has been presented. At the same time, effects of device parameter variation on ballistic, subthreshold and short channel performance is observed and presented. The ballistic simulation result has also been used to observe the electrostatic performance and Capacitance-Voltage characteristics of the device. With constant urge to keep in pace with Moore's law as well as aggressive scaling and device operation reaching near ballistic limit, a full quantum transport study at 10 nm gate length is necessary. Our simulation reveals an increase in device drain current with increasing channel cross-section. However short channel performance and subthreshold performance get degraded with channel cross-section increment. Increasing device cross-section lowers threshold voltage of the device. The effect of gate oxide thickness on ballistic device performance is also observed. Increase in top gate oxide thickness affects device performance only upto a certain value. The thickness of the top gate oxide however shows no apparent effect on device threshold voltage. The ballistic simulation study has been further used to extract ballistic injection velocity of the carrier and ballistic carrier mobility in the channel. The effect of device dimension and gate oxide thickness on ballistic velocity and effective carrier mobility is also presented.

  4. Ion beam nanopatterning of III-V semiconductors: Consistency of experimental and simulation trends within a chemistry-driven theory

    DOE PAGESBeta

    El-Atwani, O.; Norris, S. A.; Ludwig, K.; Gonderman, S.; Allain, J. P.

    2015-12-16

    In this study, several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends onmore » several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.« less

  5. Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors

    SciTech Connect

    Dey, Anup; Maiti, Biswajit; Chanda, Debasree

    2014-04-14

    A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k{sup →}) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg{sub 1−x}Cd{sub x}Te, and In{sub 1−x}Ga{sub x}As{sub y}P{sub 1−y} lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

  6. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell D. Dupuis

    2004-09-30

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the first year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The first year activities were focused on the installation, set-up, and use of advanced equipment for the metalorganic chemical vapor deposition growth of III-nitride films and the characterization of these materials (Task 1) and the design, fabrication, testing of nitride LEDs (Task 4). As a progress highlight, we obtained improved quality of {approx} 2 {micro}m-thick GaN layers (as measured by the full width at half maximum of the asymmetric (102) X-ray diffraction peak of less than 350 arc-s) and higher p-GaN:Mg doping level (free hole carrier higher than 1E18 cm{sup -3}). Also in this year, we have developed the growth of InGaN/GaN active layers for long-wavelength green light emitting diodes, specifically, for emission at {lambda} {approx} 540nm. The effect of the Column III precursor (for Ga) and the post-growth thermal annealing effect were also studied. Our LED device fabrication process was developed and initially optimized, especially for low-resistance ohmic contacts for p-GaN:Mg layers, and blue-green light emitting diode structures were processed and characterized.

  7. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell Dupuis

    2007-06-30

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers whole years of the three-year program 'Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications'. The research activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda}{approx}540nm green LEDs. We have also studied (1) the thermal annealing effect on blue and green LED active region during the p-type layer growth; (2) the effect of growth parameters and structural factors for LED active region on electroluminescence properties; (3) the effect of substrates and orientation on electrical and electro-optical properties of green LEDs. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {omega}-cm) and improved optical quality green LED active region emitting at {approx}540nm by electroluminescence. The LEDs with p-InGaN layer can act as a quantum-confined Stark effect mitigation layer by reducing strain in the QW. We also have achieved (projected) peak IQE of {approx}25% at {lambda}{approx}530 nm and of {approx}13% at {lambda}{approx}545 nm. Visible LEDs on a non-polar substrate using (11-20) {alpha}-plane bulk substrates. The absence of quantum-confined Stark effect was confirmed but further improvement in electrical and optical properties is required.

  8. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell D. Dupuis

    2006-01-01

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the second year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The second year activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on green LED active region as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda} {approx}540nm green LEDs. We have also studied the thermal annealing effect on blue and green LED active region during the p-type layer growth. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {Omega}-cm) and improved optical quality green LED active region emitting at {lambda} {approx}540nm by electroluminescence. The active region of the green LEDs was found to be much more sensitive to the thermal annealing effect during the p-type layer growth than that of the blue LEDs. We have designed grown, fabricated green LED structures for both 520 nm and 540 nm for the evaluation of second year green LED development.

  9. Growth and Characterization of Antimony-Based Narrow-Bandgap III-V Semiconductor Crystals for Infrared Detector Applications

    NASA Astrophysics Data System (ADS)

    Dixit, Vijay K.; Bhat, Handady L.

    Materials for the generation and detection of 7-12 μm wavelength radiation continue to be of considerable interest for many applications such as night vision, medical imaging, sensitive pollution gas monitoring, etc. For such applications HgCdTe has been the main material of choice in the past. However, HgCdTe lacks stability and uniformity over a large area, and only works under cryogenic conditions. Because of these problems, antimony-based III-V materials have been considered as alternatives. Consequently, there has been a tremendous growth in research activity on InSb-based systems. In fact, InSb-based compounds have proved to be interesting materials for both basic and applied research. This chapter presents a comprehensive account of research carried out so far. It explores the materials aspects of indium antimonide (InSb), indium bismuth antimonide (InBi x Sb1-x ), indium arsenic antimonide (InAs x Sb1-x ), and indium bismuth arsenic antimonide (InBi x As y Sb1-x-y ) in terms of crystal growth in bulk and epitaxial forms and interesting device feasibility. The limiting single-phase composition of InAs x Sb1-x and InBi x Sb1-x using near-equilibrium technique has been also addressed. An overview of the structural, transport, optical, and device-related properties is presented. Some of the current areas of research and development have been critically reviewed and their significance for both understanding the basic physics as well as device applications are discussed. These include the role of defects and impurity on structural, optical, and electrical properties of the materials.

  10. Soil attenuation of As(III, V) and Se(IV, VI) seepage potential at ash disposal facilities.

    PubMed

    Hyun, Seunghun; Lee, Linda S

    2013-11-01

    Leachate from ash landfills is frequently enriched with As and Se but their off-site movement is not well understood. The attenuation potential of As and Se by soils surrounding selected landfills during leachate seepage was investigated in laboratory column studies using simulated ash leachate. As(III, V) and Se(IV, VI) concentrations as well as pH, flow rate, and a tracer were monitored in influent and effluent for up to 800 pore volumes followed by sequential desorption, extraction, and digestion of column segments. Column breakthrough curves (BTCs) were compared to predictions based on previously measured sorption isotherms. Early As(V) breakthrough and retarded As(III) breakthrough relative to predicted BTCs are indicative of oxidative transformation during seepage. For Se(VI), which exhibits linear sorption and the lowest sorption propensity, measured BTCs were predicted fairly well by equilibrium sorption isotherms, except for the early arrival of Se(IV) in one site soil, which in part, may be due to higher column pH values compared to batch isotherms. Most of the As and Se retained by soils during leaching was found to be strongly sorbed (60-90%) or irreversibly bound (10-40%) with <5% readily desorbable. Redox potential favoring transformation to the more sorptive valence states of As(V) and Se(IV) will invoke additional attenuation beyond equilibrium sorption-based predictions. With the exception of Se(IV) on one site soil, results indicate that attenuation by down-gradient soils of As and Se in ash landfill seepage will often be no less than what is predicted by equilibrium sorption capacity with further attenuation expected due to favorable redox transformation processes, thus mitigating contaminant plumes and associated risks. PMID:24054132

  11. Theory and observation on non-linear effects limiting the coherence properties of high-Q hybrid Si/III-V lasers

    NASA Astrophysics Data System (ADS)

    Vilenchik, Yaakov; Santis, Christos T.; Steger, Scott T.; Satyan, Naresh; Yariv, Amnon

    2015-03-01

    Hybrid Si/III-V is a promising platform for semiconductor narrow-linewidth lasers, since light can be efficiently stored in low loss silicon and amplified in III-V materials. The introduction of a high-Q cavity in silicon as an integral part of the laser's resonator leads to major reduction of the laser linewidth. However, the large intra-cavity field intensity resulting from the high-Q operation gives rise to non-linear effects. We present a theoretical model based on non-linear rate equations to study the effect of two-photon absorption and induced free-carrier absorption in silicon on the laser's performance. The predictions from this model are compared to the experimental results obtained from narrow-linewidth lasers fabricated by us. It is shown to have an effect on the linearity of the L-I curve, and to reduce the achievable Schawlow- Townes linewidth.

  12. Influence of the group V element on the chemical potential and crystal structure of Au-catalyzed III-V nanowires

    SciTech Connect

    Dubrovskii, V. G.

    2014-02-03

    We present a kinetic growth model having a particular emphasis on the influence of the group V element on the preferred crystal structure of Au-catalyzed III-V nanowires. The model circumvents the uncertainty in the group V contribution into the overall liquid chemical potential. We show why the nanowire elongation rate is limited by the group III transport, while the crystal structure depends on the effective group V to III imbalance. Within the model, we are able to explain some important structural trends in Au-catalyzed III-V nanowires. In particular, we show that high group V flux always favors wurtzite structure in molecular-beam epitaxy. This tendency could be inverted in vapor deposition techniques due to suppression of the group III diffusion at high group V flux.

  13. Narrow-linewidth short-pulse III-V-on-silicon mode-locked lasers based on a linear and ring cavity geometry.

    PubMed

    Keyvaninia, S; Uvin, S; Tassaert, M; Fu, X; Latkowski, S; Mariën, J; Thomassen, L; Lelarge, F; Duan, G; Verheyen, P; Lepage, G; Van Campenhout, J; Bente, E; Roelkens, G

    2015-02-01

    Picosecond-pulse III-V-on-silicon mode-locked lasers based on linear and ring extended cavity geometries are presented. In passive mode-locked operation a 12 kHz -3dB linewidth of the fundamental RF tone at 4.7 GHz is obtained for the linear cavity geometry and 16 kHz for the ring cavity geometry. Stabilization of the repetition rate of these devices using hybrid mode-locking is also demonstrated. PMID:25836180

  14. 30 CFR 57.22222 - Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ....22222 Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). Brattice cloth and ventilation tubing shall be approved by MSHA in accordance with 30 CFR part 7, or shall bear a BC or VT... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Ventilation materials (I-A, I-B, I-C, II-A,...

  15. 30 CFR 57.22222 - Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ....22222 Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). Brattice cloth and ventilation tubing shall be approved by MSHA in accordance with 30 CFR part 7, or shall bear a BC or VT... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Ventilation materials (I-A, I-B, I-C, II-A,...

  16. 30 CFR 57.22222 - Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ....22222 Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). Brattice cloth and ventilation tubing shall be approved by MSHA in accordance with 30 CFR part 7, or shall bear a BC or VT... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Ventilation materials (I-A, I-B, I-C, II-A,...

  17. 30 CFR 57.22222 - Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). 57.22222 Section 57.22222 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety...

  18. 30 CFR 57.22222 - Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Ventilation materials (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). 57.22222 Section 57.22222 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety...

  19. Liquid phase epitaxy of binary III-V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing

    NASA Astrophysics Data System (ADS)

    Wutzler, Rene; Rebohle, Lars; Prucnal, Slawomir; Bregolin, Felipe L.; Hübner, Rene; Voelskow, Matthias; Helm, Manfred; Skorupa, Wolfgang

    2015-05-01

    The integration of III-V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III-V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO2/Si/SiO2 layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III-V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.

  20. Increased bismuth concentration in MBE GaAs{sub 1−x}Bi{sub x} films by oscillating III/V flux ratio during growth

    SciTech Connect

    Wood, Adam W. Babcock, Susan E.; Li, Jincheng; Brown, April S.

    2015-05-15

    The authors have examined bismuth concentration profiles in GaAs{sub 1−x}Bi{sub x} films grown by molecular beam epitaxy using high angle annular dark field imaging (Z-contrast imaging) in an aberration-corrected scanning transmission electron microscope in conjunction with x-ray diffraction. Samples were grown with a gradient in each of the component fluxes, and therefore, the III/V ratio across the substrate. Rotating the sample during growth exposed the growth surface to an oscillating III/V flux ratio. Sinusoidal [Bi] profiles resulted in the growth direction, the wavelength and number of which were consistent with the growth rate and the rate of substrate rotation. However, the magnitude of [Bi] in the observed fluctuations was greater than the maximum [Bi] achieved using the same Bi flux and Ga/As flux ratios in steady-state conditions on a stationary substrate, suggesting that varying the III/V flux ratio during growth promotes the incorporation of Bi in GaAs{sub 1−x}Bi{sub x} films. A proposed qualitative model for how this enhancement might occur hypothesizes a critical role for alternating growth and shrinkage of Ga-Bi predroplet clusters on the surface as the growing material is rotated through Ga-rich and As-rich flux compositions.

  1. Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration

    PubMed Central

    Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca i Cabarrocas, Pere

    2016-01-01

    The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs. PMID:27166163

  2. GaN as an interfacial passivation layer: tuning band offset and removing fermi level pinning for III-V MOS devices.

    PubMed

    Zhang, Zhaofu; Cao, Ruyue; Wang, Changhong; Li, Hao-Bo; Dong, Hong; Wang, Wei-Hua; Lu, Feng; Cheng, Yahui; Xie, Xinjian; Liu, Hui; Cho, Kyeongjae; Wallace, Robert; Wang, Weichao

    2015-03-11

    The use of an interfacial passivation layer is one important strategy for achieving a high quality interface between high-k and III-V materials integrated into high-mobility metal-oxide-semiconductor field-effect transistor (MOSFET) devices. Here, we propose gallium nitride (GaN) as the interfacial layer between III-V materials and hafnium oxide (HfO2). Utilizing first-principles calculations, we explore the structural and electronic properties of the GaN/HfO2 interface with respect to the interfacial oxygen contents. In the O-rich condition, an O8 interface (eight oxygen atoms at the interface, corresponding to 100% oxygen concentration) displays the most stability. By reducing the interfacial O concentration from 100 to 25%, we find that the interface formation energy increases; when sublayer oxygen vacancies exist, the interface becomes even less stable compared with O8. The band offset is also observed to be highly dependent on the interfacial oxygen concentration. Further analysis of the electronic structure shows that no interface states are present at the O8 interface. These findings indicate that the O8 interface serves as a promising candidate for high quality III-V MOS devices. Moreover, interfacial states are present when such interfacial oxygen is partially removed. The interface states, leading to Fermi level pinning, originate from unsaturated interfacial Ga atoms. PMID:25639492

  3. Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration.

    PubMed

    Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca I Cabarrocas, Pere

    2016-01-01

    The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs. PMID:27166163

  4. Modeling and design of an advanced high pressure system for III-V compound synthesis and crystal growth

    NASA Astrophysics Data System (ADS)

    Jafri, Ijaz Hussain

    Indium Phosphide (InP) is an important substrate material for opto-electronics and light-wave communications. In many applications InP-based devices are found to be superior in performance than GaAs, Ge or Si based devices. However, its broad use has been limited because of the quality and cost of commercially available substrates. The primary objective of this research is to design and develop an advanced high pressure system to implement the novel technique of "one-step" in-situ synthesis and growth of InP crystals. Detailed numerical modeling and engineering analysis/design is performed to examine the critical issues associated with the growth of large diameter (up to 150 mm) III-V compound crystals. After design and fabrication, experimental work on conducted for InP synthesis. The research indicates that multiple hotzones are needed to reduce the thermal stresses in as-grown crystals. The hotzone insulation package should be strategically designed to allow more heat loss in the axial direction; a water-cooled shaft can help to accomplish this. To reduce gas convection, empty spaces should be minimized. To obtain uniform temperature and dopant distributions, a moderate rotation rate may be appropriate in the proposed configurations; higher rotation rates may cause the flow to become unsteady and turbulent. It may be desirable to use slightly higher rotation rates in the beginning and lower towards the end of growth. The modeling study also supports the use of a magnetic field to suppress flow oscillations and to control interface shape. Several innovations are proposed in the new design. The most significant are the independently-controlled injection system with its unique ball valve and multi-component arrangement that allows flexibility not seen in other high pressure systems, and a multi-span high-resolution weight monitoring system for crucible and crystal/injector. Experiments are conducted to study the effect of pressure, the thermal profiling, and the synthesis of InP. For the first time quantitative analysis is available on the effect of pressure on power consumption in the system. The thermal profiling indicates the presence of low temperature gradients in the system. The experimental program led to several successful runs for polycrystalline InP synthesis.

  5. The Dependence of Electrical Properties on Miscut Orientation in Direct Bonded III-V Solar Cell Layers

    NASA Astrophysics Data System (ADS)

    Seal, Mark

    Direct bonding is a materials integration process in which wafer substrates are directly bonded without any intermediate layers. This technique has been used to fabricate direct bonded n-GaAs//n-GaAs, n-GaAs//n-InP, and n-InP//n-InP structures comprised of combinations of on-axis substrates and substrates with (001) faces misoriented 4° toward in order to study the effect of relative surface misorientation on the electrical properties of the bonded interface. Simulation and measurement of interface electrical conductivity were used to identify properties including height and shape of the potential barrier. Across all substrate combinations, as the relative surface misorientation was increased, the interface resistance and height of the interfacial potential barrier also increased. Current density -- voltage measurements of GaAs//InP bonded structures revealed no band structure asymmetry at low ( +/- 50 mV) bias. Transmission electron microscopy was used to observe the morphology of the interface between InP//InP and GaAs//InP structures. Consistent with previous reports, results of electrical measurements indicate that the potential barrier height at interfaces containing at least one side InP are less sensitive to increased interface resistance with increasing misorientation. Low temperature (≤ 600 °C) and kPa applied pressure to initiate bonding between (NH4S)2 pretreated GaAs and InP wafers was used to fabricate direct bonded structures. Wafers were bonded face-to-face on-axis, with relative misorientation of 4° or 8°, or a by bonding a combination of 4° miscut substrates bonded such that relative misorientation was zero. The samples were annealed at 400 °C for 2 hours to strengthen the bond, and then subjected to rapid thermal processing at 600 °C for 2 minutes to improve the electrical conductivity. When compared to on-axis structures, the interface resistance at room temperature for 4° misoriented bonded pairs increased from 0.011 O˙cm2 to 2.8 O˙cm 2 for GaAs//GaAs structures, from 0.00824 O˙cm2 to 0.0161 O˙cm2 for GaAs//InP structures and only from 0.0063 O˙cm2 to 0.0089 O˙cm 2 for InP//InP structures. The electronic behavior at the interface was modeled using the Seager-Pike theoretical model for electron tunneling between adjacent semiconductor bicrystals. In accordance with this model the zero-bias conductance was used to estimate the conduction barrier height at the bonded interface. The zero-bias conductance taken at temperatures from 90 to 340 K reveals an increase in potential barrier height across all wafer combinations as the degree of surface misorientation is increased, from 0.26 eV to 0.305 eV for InP//InP structures, from 0.32 eV to 0.39 eV for GaAs//InP structures, and from 0.54 eV to 1.0 eV for GaAs//GaAs structures. For all material combinations studied, structures with zero relative misorientation displayed equivalent electrical performance to nominal on-axis substrates, demonstrating that relative surface misorientation rather than substrate miscut is responsible for changes in electrical resistivity. The large increase in potential barrier height for GaAs//GaAs structures indicates that the degree of relative misorientation between GaAs//GaAs wafer bonded pairs has a significant impact on interface electrical properties, and is consistent with previous GaAs//GaAs studies. However for GaAs//InP wafer bonded pairs, the relative misorientation across the bonded interface plays a less significant role, and the impact of relative misorientation is least significant for InP/.InP bonded structures. This is illustrated by the increase in potential barrier of 0.04 eV for InP//InP structures, 0.06 eV for GaAs//InP structures, and 0.47 eV for GaAs//GaAs structures as relative misorientation is increased from 0° to 8°. High resolution transmission electron microscopy and high-angle annular dark field are used to confirm the misorientation of GaAs//InP and InP//InP bonded samples and determine the interface morphology. No interfacial layer is present in InP//InP structures before or after rapid thermal processing. It is observed that regions adjacent to the interface undergo a process of atomic redistribution and recrystallize into the same lattice arrangement as the bulk semiconductor. GaAs//InP interfaces are observed to contain regions direct substrate contact with oxide inclusions in between after rapid thermal processing, consistent with previous work on GaAs//GaAs interfaces. It is concluded that for III-V direct wafer bonded heterostructures, interface conductivity is a function of both the relative misorientation between the (001) surfaces and the material pair. The significance of this study is that the additional variable of lattice mismatch does not degrade electrical conductivity through GaAs//InP interfaces. This is significant for applications where heterostructure interface conduction must be controlled, such as the direct bonding of III-V wafers for photovoltaic applications.

  6. Optimization and Characterization of Indium Arsenide Quantum Dots for Application in III-V Material Solar Cells

    NASA Astrophysics Data System (ADS)

    Podell, Adam P.

    In this work, InAs quantum dots grown by organometallic vapor-phase epitaxy (OMVPE) are investigated for application in III - V material solar cells. The first focus is on the opti- mization of growth parameters to produce high densities of uniform defect-free quantum dots via growth on 2" vicinal GaAs substrates. Parameters studied are InAs coverage, V/III ratio and growth rate. QDs are grown by the Stranski-Krastanov (SK) growth mode on (100) GaAs substrates misoriented toward (110) or (111) planes with various degrees of misorientation from 0° to 6°. Atomic force microscopy results indicated that as misorientation angle increased toward(110),critical thickness for quantum dot formation increased with theta c =1.8ML,1.9ML and 2.0 ML corresponding to 0°, 2° and 6°, respectively. Results for quantum dots grown on (111) misoriented substrates indicated, on average, that higher densities of quantum dots were achieved, compared with similar growths on substrates misoriented toward (110). Most notably, a stable average number density of 8 x 1010cm -2 was observed over a range of growth rates of 0.1ML/s - 0.4ML/s on (111) misoriented substrates compared with a decreasing number density as low as 2.85 x 1010cm -2 corresponding to a growth rate of 0.4ML/s grown on (110) misoriented substrates. p-i-n solar cell devices with a 10-layer quantum dot super- lattice imbedded in the i-region were also grown on (100) GaAs substrates misoriented 0°, 2° and 6° toward (110) as well as a set of devices grown on substrates misoriented toward (111). Device results showed a 1.0mA/cm2 enhancement to the short-circuit current for a v 2° misoriented device with 2.2 ML InAs coverage per quantum dot layer. Spectral response measurements were performed and integrated spectral response showed sub-GaAs bandgap short-circuit contribution which increased with increasing InAs coverage in the quantum dot layers from 0.04mA/cm2/ML, 0.28mA/cm2/ ML and 0.19mA/cm2/ML corresponding to 0°, 2° and 6° misorientation, respectively. The second focus of this study was on the OMVPE growth of InAs quantum dots in a large-area commercial reactor. Quantum dot growth parameters require careful balancing in the large-scale reactor due to different thermodynamic and flow profiles compared with smaller- area reactors. The goal of the work was to control the growth process in order to produce high densities of uniform quantum dots for inclusion in double and triple junction III - V material solar cells. Initial growth proved unsuccessful due to lack of familiarity with the process but through balancing of injector flows of alkyl gasses, coherent and optically active quantum dots were able to first be formed at low densities (0.5 - 0.7 x 1010 cm-2). Further optimization included increased quantum dot growth times leading to number densities in the (2.1-2.7x10 10cm-2 with improved optical performance as measured by photoluminescence (PL) spectroscopy. Finally, an investigation of GaAs spacer layer thickness for improved optical coupling was performed, indicating that a combined low temperature and high temperature GaAs thickness of 9.3nm led to strong PL intensity indicating good optical coupling of QD layers. Ge/(In)GaAs double junction solar cells were grown and fabricated with and without quantum dots in the (In)GaAs cell to investigate the effect of quantum dot inclusion on device performance. AM 0 measurements showed an average increase of 1.0mA/cm 2 in short-circuit current for these devices. Integrated spectral response measurements revealed a contribution to short-circuit current of 0.02mA/cm2/QDlayer which is consistent with reports seen in literature. The current improvement for the double junction solar cells motivated the investigation of quantum dot inclusion in the (In)GaAs junction of a Ge/(In)GaAs/InGaP triple junction solar cell. AM0 measurements on these cells did not reveal any increase in current for quantum dot enhanced devices over a baseline device. Integrated spectral response for each junction revealed an increase of 0.3mA/cm 2 in current for the middle junction and the top junction, respectively, compared with baseline results for these junctions, but also that the InGaP top junction was current limiting. This potentially is due to poor material quality in the InGaP junction as a result of quantum dot inclusion in the junction beneath it or to strain effects re- sulting from quantum dot inclusion. This current limiting nature of the top junction may have led to a reduced efficiency for quantum dot devices compared with a baseline and further opti- mization is required in order increase the efficiency of the quantum dot device compared with a baseline device.

  7. Beyond CMOS: heterogeneous integration of III-V devices, RF MEMS and other dissimilar materials/devices with Si CMOS to create intelligent microsystems.

    PubMed

    Kazior, Thomas E

    2014-03-28

    Advances in silicon technology continue to revolutionize micro-/nano-electronics. However, Si cannot do everything, and devices/components based on other materials systems are required. What is the best way to integrate these dissimilar materials and to enhance the capabilities of Si, thereby continuing the micro-/nano-electronics revolution? In this paper, I review different approaches to heterogeneously integrate dissimilar materials with Si complementary metal oxide semiconductor (CMOS) technology. In particular, I summarize results on the successful integration of III-V electronic devices (InP heterojunction bipolar transistors (HBTs) and GaN high-electron-mobility transistors (HEMTs)) with Si CMOS on a common silicon-based wafer using an integration/fabrication process similar to a SiGe BiCMOS process (BiCMOS integrates bipolar junction and CMOS transistors). Our III-V BiCMOS process has been scaled to 200 mm diameter wafers for integration with scaled CMOS and used to fabricate radio-frequency (RF) and mixed signals circuits with on-chip digital control/calibration. I also show that RF microelectromechanical systems (MEMS) can be integrated onto this platform to create tunable or reconfigurable circuits. Thus, heterogeneous integration of III-V devices, MEMS and other dissimilar materials with Si CMOS enables a new class of high-performance integrated circuits that enhance the capabilities of existing systems, enable new circuit architectures and facilitate the continued proliferation of low-cost micro-/nano-electronics for a wide range of applications. PMID:24567473

  8. Arsenic (III, V), indium (III), and gallium (III) toxicity to zebrafish embryos using a high-throughput multi-endpoint in vivo developmental and behavioral assay.

    PubMed

    Olivares, Christopher I; Field, Jim A; Simonich, Michael; Tanguay, Robert L; Sierra-Alvarez, Reyes

    2016-04-01

    Gallium arsenide (GaAs), indium gallium arsenide (InGaAs) and other III/V materials are finding increasing application in microelectronic components. The rising demand for III/V-based products is leading to increasing generation of effluents containing ionic species of gallium, indium, and arsenic. The ecotoxicological hazard potential of these streams is unknown. While the toxicology of arsenic is comprehensive, much less is known about the effects of In(III) and Ga(III). The embryonic zebrafish was evaluated for mortality, developmental abnormalities, and photomotor response (PMR) behavior changes associated with exposure to As(III), As(V), Ga(III), and In(III). The As(III) lowest observable effect level (LOEL) for mortality was 500 μM at 24 and 120 h post fertilization (hpf). As(V) exposure was associated with significant mortality at 63 μM. The Ga(III)-citrate LOEL was 113 μM at 24 and 120 hpf. There was no association of significant mortality over the tested range of In(III)-citrate (56-900 μM) or sodium citrate (213-3400 μM) exposures. Only As(V) resulted in significant developmental abnormalities with LOEL of 500 μM. Removal of the chorion prior to As(III) and As(V) exposure was associated with increased incidence of mortality and developmental abnormality suggesting that the chorion may normally attenuate mass uptake of these metals by the embryo. Finally, As(III), As(V), and In(III) caused PMR hypoactivity (49-69% of control PMR) at 900-1000 μM. Overall, our results represent the first characterization of multidimensional toxicity effects of III/V ions in zebrafish embryos helping to fill a significant knowledge gap, particularly in Ga(III) and In(III) toxicology. PMID:26824274

  9. Growth rate for the selective epitaxial growth of III-V compounds inside submicron shallow-trench-isolation trenches on Si (001) substrates by MOVPE: Modeling and experiments

    NASA Astrophysics Data System (ADS)

    Jiang, S.; Merckling, C.; Guo, W.; Waldron, N.; Caymax, M.; Vandervorst, W.; Seefeldt, M.; Heyns, M.

    2014-04-01

    A mathematical model was developed to examine the growth rate of III-V compounds inside sub-micron trenches by MOVPE. Based on this model, we theoretically analyzed the possible dependence of the growth rate on the trench width primarily from two aspects, i.e. Knudson diffusion and enhanced equilibrium vapor pressure due to the shrinking trench size. Then, associated with the experimental data from the growth of both InAlAs and InAs, we found that the average growth rate inside submicron trenches is primarily influenced by trench diffusion type under typical growth conditions.

  10. Detection of soft X-rays with NEA III-V photocathodes. [Negative Electron Affinity X-ray detector for astronomy

    NASA Technical Reports Server (NTRS)

    Bardas, D.; Kellogg, E.; Murray, S.; Enck, R., Jr.

    1978-01-01

    A description is presented of the results of tests on an X-ray photomultiplier containing a negative electron affinity (NEA) photocathode. This device makes it possible to investigate the response of the NEA photocathode to X-rays of various energies. The obtained data provide a basis for the determination of the photoelectron yield and energy resolution of the considered photocathode as a function of energy in the range from 0.8 to 3 keV. The investigation demonstrates the feasibility of using an NEA III-V photocathode for the detection of soft X-rays.

  11. Nanostructures produced by phase-separation during growth of (III-V).sub.1-x(IV.sub.2).sub.x alloys

    SciTech Connect

    Norman, Andrew G.; Olson, Jerry M.

    2007-06-12

    Nanostructures (18) and methods for production thereof by phase separation during metal organic vapor-phase epitaxy (MOVPE). An embodiment of one of the methods may comprise providing a growth surface in a reaction chamber and introducing a first mixture of precursor materials into the reaction chamber to form a buffer layer (12) thereon. A second mixture of precursor materials may be provided into the reaction chamber to form an active region (14) on the buffer layer (12), wherein the nanostructure (18) is embedded in a matrix (16) in the active region (14). Additional steps are also disclosed for preparing the nanostructure (18) product for various applications.

  12. Demonstration of 12.2% wall plug efficiency in uncooled single mode external-cavity tunable Si/III-V hybrid laser.

    PubMed

    Lee, Jin-Hyoung; Bovington, Jock; Shubin, Ivan; Luo, Ying; Yao, Jin; Lin, Shiyun; Cunningham, John E; Raj, Kannan; Krishnamoorthy, Ashok V; Zheng, Xuezhe

    2015-05-01

    A Si/III-V hybrid laser has been a highly sought after device for energy-efficient and cost-effective high-speed silicon photonics communication. We present a high wall-plug efficiency external-cavity hybrid laser created by integrating an independently optimized SOI ring reflector and a III-V gain chip. In our demonstration, the uncooled integrated laser achieved a waveguide-coupled wall-plug efficiency of 12.2% at room temperature with an optical output power of ~10 mW. The laser operated single-mode near 1550 nm with a linewidth of 0.22 pm. This is a tunable light source with 8 nm wavelength tuning range. A proof-of-concept laser wavelength stabilization technique has also been demonstrated. Using a simple feedback loop, we achieved mode-hop-free operation in a packaged external-cavity hybrid laser as bias current was varied by 60mA. PMID:25969296

  13. Temperature dependence of frequency dispersion in III-V metal-oxide-semiconductor C-V and the capture/emission process of border traps

    NASA Astrophysics Data System (ADS)

    Vais, Abhitosh; Lin, Han-Chung; Dou, Chunmeng; Martens, Koen; Ivanov, Tsvetan; Xie, Qi; Tang, Fu; Givens, Michael; Maes, Jan; Collaert, Nadine; Raskin, Jean-Pierre; DeMeyer, Kristin; Thean, Aaron

    2015-08-01

    This paper presents a detailed investigation of the temperature dependence of frequency dispersion observed in capacitance-voltage (C-V) measurements of III-V metal-oxide-semiconductor (MOS) devices. The dispersion in the accumulation region of the capacitance data is found to change from 4%-9% (per decade frequency) to ˜0% when the temperature is reduced from 300 K to 4 K in a wide range of MOS capacitors with different gate dielectrics and III-V substrates. We show that such significant temperature dependence of C-V frequency dispersion cannot be due to the temperature dependence of channel electrostatics, i.e., carrier density and surface potential. We also show that the temperature dependence of frequency dispersion, and hence, the capture/emission process of border traps can be modeled by a combination of tunneling and a "temperature-activated" process described by a non-radiative multi-phonon model, instead of a widely believed single-step elastic tunneling process.

  14. A study on room-temperature photoluminescence and crystallinity of RF-sputtered GaN for a cost-effective III-V-on-Si platform

    NASA Astrophysics Data System (ADS)

    Lee, Jeongmin; Kim, Hong-Seok; Han, Jae-Hee; Cho, Seongjae

    2015-11-01

    Recently, Si technology has been searching for ways to develop Si-driven future electronics by overcoming the limitations in its electrical and optical properties through more Moore (MM), morethan- Moore (MtM), and beyond complementary metal-oxide-semiconductor (CMOS) approaches. Among the suggested strategies, III-V-on-Si heterogeneous integration can be a solution that allows the merger of III-V-based devices and Si CMOS logic blocks on Si monolithically and costeffectively. GaN has wide applicability owing to its high electron mobility and large energy bandgap for high-speed low-power transistors and visible light sources. In this work, the room-temperature photoluminescence (PL) characteristics and the crystallinity of GaN-on-Si were empirically studied. GaN was deposited by using RF sputtering on p-type Si substrates. The results show that the peak location near 520 nm does not vary with the wavelength of the excitation laser, which is strongly supported by the fact that the signals are not from higher-order harmonics but are genuinely from the prepared GaN. Further, a sharp peak is observed in the X-ray diffraction (XRD) analysis cooperatively performed with PL experiments. Consequently, partially-crystallized GaN has been obtained on Si by using conventional CMOS processing with a low thermal budget and high cost-effectiveness.

  15. Optical and electrical properties of III-V nitride wide bandgap semiconductors. Annual report, April 1, 1997--May 31, 1998

    SciTech Connect

    1998-06-01

    The objectives of this project were to investigate the optical and electrical properties of III-nitride wide bandgap semiconductors (GaN, InGaN, AlGaN) and quantum wells, to understand the fundamental optical transitions and impurity properties of these materials, to study the physics components of GaN-based devices, and to provide input for new approaches toward the improvement of materials quality and the optimization of device design. We were the first group to employ transport measurement techniques on the persistent photoconductivity (PPC) state to study the impurity properties of III-nitrides. We were also one of the few research groups m in the world to employ picosecond time-resolved photoluminescence (PL) measurement technique to study mechanisms of optical transitions, LED emission, and lasing m in GaN materials. During this funding period, we have investigated a variety of GaN samples and structures grown by MBE as well as by MOCVD. We have also made a significant progress in MOCVD GaN materials growth. This report briefly discusses the following accomplishments: effects of deep level impurities in the AlGaN/GaN heterostructures; materials characterization of III-nitrides alloys; optical studies of III-nitride epilayers and quantum wells; fabrication and optical studies of III-nitride microdisk arrays; and materials growth by MOCVD.

  16. Midwave (3-5 um) III-V infrared LEDs and diode lasers as a source for gas sensors

    NASA Astrophysics Data System (ADS)

    Matveev, Boris A.; Aidaraliev, M.; Zotova, Nonna V.; Karandashev, Sergey A.; Stus', Nikolai M.; Talalakin, Georgii N.

    1995-09-01

    Recently developed mid-IR LEDs and diode lasers can be used to fabricate spectroscopic analyzers of a new generation. The LED-based design is advantageous, especially in process and portable instruments and fiber optic applications. The benefits are smaller instrument size, rugged operation without any moving parts, and high output pulse power. The availability of new ambient temperature operating LEDs based on A3B5 alloys in the spectral range of 2.8-4.7 micrometers and cooled diode lasers has made it possible to monitor several gases having strong absorption bands in this region. This paper briefly describes the properties and fabrication of infrared light emitting diodes and diode lasers by liquid phase epitaxy for emission wavelengths from 3.8 micrometers to 4.85 micrometers and 3-3.6 micrometers respectively. Some of the first applications of these LEDs and diode lasers in spectroscopic instrumentation (nondispersive CO2 and fiber optic CnHm analyzers) are described.

  17. New bonding technique for III-V thin film and macroscopic devices to Si or CuW

    NASA Astrophysics Data System (ADS)

    Dohle, G. Rainer; Callahan, John J.; Drabik, Timothy J.; Martin, Kevin P.

    1996-01-01

    The increasing demand for more advanced photonic integrated circuits has created the need to combine semiconductor materials with different lattice constants, i.e., GaAs on Si. During the past few years, much has been reported concerning the epitaxial lift-off technique. The most widely reported bonding method of epitaxial lift-off films is van der Waals bonding. However, there are problems with van der Waals-bonded devices. For instance, it has a long bonding time, which hinders an industrial use. Recently, we have investigated refinements of the epitaxial lift-off and grafting technique through using a single, transparent polymer membrane to support the material during the etch of a sacrificial layer, then depositing Au and Sn multilayers onto the lifted off devices and new host substrate. The devices are bonded by applying heat and pressure in a reducing atmosphere. The multilayer structures investigated in this work produce a resulting AuSn alloy with approximately 84 wt.% gold, but can be bonded with a peak temperature of 235 degree(s)C. In this paper we report our results in the optimization of the bonding parameters, with different diffusion barriers, new multilayer structures, as well as new applications of our bonding technique. We achieved important improvements in reliability and yield. The main advantages of our technology are thin bonding layers achieved with a minimum use of gold and an outstanding bonding quality reached in the large temperature range between 235 degree(s)C and 286 degree(s)C without flux. A thin, void free bonding layer means low thermal resistivity, which is especially important for laser diodes and high power devices. Further advantages of our new technique are the attainable precise control of the bonding layer thickness and the possible alignment of the devices through the transparent support and bonding membrane. We applied our new bonding technique to different optoelectronic devices such as MQWs and commercial laser bars and have simultaneously bonded a large number of devices. The bonded samples were investigated with several standard surface analysis techniques like optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis as well as mechanical tests.

  18. The recombination velocity at III-V compound heterojunctions with applications to Al (x) Ga(1-x)As-GaAs(1-y)Sb(y)

    NASA Technical Reports Server (NTRS)

    Kim, J. S.

    1978-01-01

    Interface recombination velocity in AlxGa1-xAs-GaAs and A10.85 Ga0.15As-GaAs1-ySby heterojunction systems was studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAsSb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates.

  19. New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1991--31 July 1992

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P.

    1993-04-01

    This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell`s efficiency less dependent on materialquality.

  20. New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1990--31 July 1991

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O`Bradovich, G.J.; Young, M.P.

    1993-01-01

    This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

  1. Origin of nonlinear piezoelectricity in III-V semiconductors: Internal strain and bond ionicity from hybrid-functional density functional theory

    NASA Astrophysics Data System (ADS)

    Caro, Miguel A.; Schulz, Stefan; O'Reilly, Eoin P.

    2015-02-01

    We derive first- and second-order piezoelectric coefficients for the zinc-blende III-V semiconductors {Al ,Ga ,In }-{N ,P ,As ,Sb } . The results are obtained within the Heyd-Scuseria-Ernzerhof hybrid-functional approach in the framework of density functional theory and the Berry-phase theory of electric polarization. To achieve a meaningful interpretation of the results, we build an intuitive phenomenological model based on the description of internal strain and the dynamics of the electronic charge centers. We discuss in detail first- and second-order internal strain effects, together with strain-induced changes in ionicity. This analysis reveals that the relatively large importance in the III-Vs of nonlinear piezoelectric effects compared to the linear ones arises because of a delicate balance between the ionic polarization contribution due to internal strain relaxation effects, and the contribution due to the electronic charge redistribution induced by macroscopic and internal strain.

  2. Al L2,3 edge x-ray absorption spectra in III-V semiconductors: Many-body perturbation theory in comparison with experiment

    NASA Astrophysics Data System (ADS)

    Olovsson, W.; Tanaka, I.; Mizoguchi, T.; Radtke, G.; Puschnig, P.; Ambrosch-Draxl, C.

    2011-05-01

    We investigate core excitations of the Al 2p edge in the III-V semiconductors AlP, AlAs, AlSb, and AlN. For the latter, we consider the wurtzite, zinc-blende, and rock-salt polymorphs. First-principles calculations are performed utilizing two different approaches, which are the solution of the Bethe-Salpeter equation (BSE) as well as the supercell technique employing the core-hole approximation. In addition, measurements of the electron energy-loss near-edge structure of the metastable AlN phase are presented. We find that the relative intensities of the spectral features are better described by the BSE than by the supercell method. We analyze the character of the near-edge peaks and trace back their origin to strongly bound core excitons in the case of AlSb and rock-salt AlN.

  3. Syntheses and X-ray structures of potassium derivatives and a paramagnetic nickel(II) complex of a cyclodiphosph(III/V)azane monoselenide.

    PubMed

    Chivers, Tristram; Krahn, Mark; Schatte, Gabriele

    2002-08-26

    The cyclodiphosph(III/V)azane monoselenide [(t)Bu(H)N(Se)P(micro-N(t)Bu)(2)PN(H)(t)Bu] (6, H(2)cdppSe where cdpp = cyclodiphosphazane) is obtained in quantitative yield from the comproportionation reaction of equimolar amounts of H(2)cdpp (7) and H(2)cdppSe(2) (3) in toluene at 85 degrees C. The X-ray structures of 3 and 6 reveal that both the monoselenide and the diselenide adopt a cis,endo,exo arrangement of the (t)BuNH groups. Metalation of 6 with 1 equiv of KO(t)Bu or 2 equiv of KCH(2)Ph in THF produces [(THF)K[HcdppSe

  4. The role of the split-off band in electron-hole energy exchange dynamics in selected III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Sadra, K.; Maziar, C. M.; Streetman, B. G.

    1989-09-01

    We report a Monte-Carlo investigation of Coulomb electron-hole scattering processes involving the split-off band in selected III-V semiconductors in the context of steady-state high-field minority-electron transport. Due to the small value of the relevant hole overlap factors, as well as the relative values of the Γ-L energy separation and the split-off energy, such processes do not make a significant contribution to the minority electron energy loss rate in In0.53Ga0.47As. In InP, however, the ΓhΓs process accounts for a significant fraction of the total Γ-electron energy loss to holes.

  5. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.; Miller, W. E.

    1988-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys InPBi, InAsBi, and InSbBi were studied theoretically. Bond energies, bond lengths, and strain coefficients were calculated for pure AlBi, GaBi, and InBi compounds and their alloys, and predictions were made for the mixing enthalpies, miscibility gaps, and critical metastable-to-stable material transition temperatures. Miscibility calculations indicate that InSbBi will be the most miscible, and the InPBi will be the the most difficult to mix. However, calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys and substantially harder than the currently favored narrow-gap semiconductor HgCdTe.

  6. Is kidney function affecting the management of myocardial infarction? A retrospective cohort study in patients with normal kidney function, chronic kidney disease stage III-V, and ESRD.

    PubMed

    Saad, Marc; Karam, Boutros; Faddoul, Geovani; Douaihy, Youssef El; Yacoub, Harout; Baydoun, Hassan; Boumitri, Christine; Barakat, Iskandar; Saifan, Chadi; El-Charabaty, Elie; Sayegh, Suzanne El

    2016-01-01

    Patients with chronic kidney disease (CKD) are three times more likely to have myocardial infarction (MI) and suffer from increased morbidity and higher mortality. Traditional and unique risk factors are prevalent and constitute challenges for the standard of care. However, CKD patients have been largely excluded from clinical trials and little evidence is available to guide evidence-based treatment of coronary artery disease in patients with CKD. Our objective was to assess whether a difference exists in the management of MI (ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction) among patients with normal kidney function, CKD stage III-V, and end-stage renal disease (ESRD) patients. We conducted a retrospective cohort study on patients admitted to Staten Island University Hospital for the diagnosis of MI between January 2005 and December 2012. Patients were assigned to one of three groups according to their kidney function: Data collected on the medical management and the use of statins, platelet inhibitors, beta-blockers, and angiotensin converting enzyme inhibitors/angiotensin receptor blockers were compared among the three cohorts, as well as medical interventions including: catheterization and coronary artery bypass graft (CABG) when indicated. Chi-square test was used to compare the proportions between nominal variables. Binary logistic analysis was used in order to determine associations between treatment modalities and comorbidities, and to account for possible confounding factors. Three hundred and thirty-four patients (mean age 67.213.9 years) were included. In terms of management, medical treatment was not different among the three groups. However, cardiac catheterization was performed less in ESRD when compared with no CKD and CKD stage III-V (45.6% vs 74% and 93.9%) (P<0.001). CABG was performed in comparable proportions in the three groups and CABG was not associated with the degree of CKD (P=0.078) in binary logistics regression. Cardiac catheterization on the other hand carried the strongest association among all studied variables (P<0.001). This association was maintained after adjusting for other comorbidities. The length of stay for the three cohorts (non-CKD, CKD stage III-V, and ESRD on hemodialysis) was 16, 17, and 15 days, respectively and was not statistically different. Many observations have reported discrimination of care for patients with CKD considered suboptimal candidates for aggressive management of their cardiac disease. In our study, medical therapy was achieved at high percentage and was comparable among groups of different kidney function. However, kidney disease seems to affect the management of patients with acute MI; percutaneous coronary angiography is not uniformly performed in patients with CKD and ESRD when compared with patients with normal kidney function. PMID:26858529

  7. Optical phonon modes of III-V nanoparticles and indium phosphide/II-VI core-shell nanoparticles: A Raman and infrared study

    NASA Astrophysics Data System (ADS)

    Manciu, Felicia Speranta

    The prospects for realizing efficient nanoparticle light emitters in the visible/near IR for communications and bio-medical applications have benefited from progress in chemical fabrication of nanoparticles. III-V semiconductor nanopaticles such as GaP and InP are promising materials for the development of "blue" and "green" emitters, respectively, due to their large effective bandgaps. Enhanced emission efficiency has been achieved for core-shell nanoparticles, since inorganic shell materials increase electronic tunability and may decrease surface defects that often occur for nanoparticles capped with organic molecules. Also, the emission wavelength of InP nanoparticle cores can be tuned from green to red by changing the shell material in InP/II-VI core-shell nanoparticles. Investigations of phonon modes in nanocrystals are of both fundamental and applied interest. In the former case the optical phonon modes, such as surface/interface modes, are dependent on the nanoparticle dimensions, and also can provide information about dynamical properties of the nanoparticles and test the validity of various theoretical approaches. In the latter case the vibronic properties of nanoparticle emitters are controlled by confined phonons and modifications of the electron-phonon interaction by the confinement. Thus, the objective of the present thesis is the detailed study of the phonon modes of III-V nanoparticles (GaP and InP) and InP/II-VI core-shell nanoparticles by IR absorption and Raman scattering spectroscopies, and an elucidation of their complex vibrational properties. With the exception of three samples (two GaP and one InP), all samples were synthesized by a novel colloidal chemistry method, which does not requires added surfactant, but rather treatment of the corresponding precursors in octadecene noncoordinative solvent. Sample quality was characterized by ED, TEM and X-ray diffraction. Based on a comparison with a dielectric continuum model, the observed features in the IR and Raman results are assigned to the surface optical (SO) modes of the corresponding nanoparticles (InP and GaP), and to SO/interface modes for InP/II-VI core-shell nanoparticles. For the latter systems, an evaluation of the ratio of the shell material thickness to the core radius is achieved. Reasonable agreement is obtained between the Raman and FIR results, as well as with the calculations. (Abstract shortened by UMI.)

  8. A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP

    SciTech Connect

    Khalid, M.; Hübner, R.; Baehtz, C.; Skorupa, W.; Zhou, Shengqiang; Gao, Kun; Helm, M.; Weschke, E.; Gordan, O.; Salvan, G.; Zahn, D. R. T.

    2015-01-28

    The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.

  9. A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP

    NASA Astrophysics Data System (ADS)

    Khalid, M.; Gao, Kun; Weschke, E.; Hübner, R.; Baehtz, C.; Gordan, O.; Salvan, G.; Zahn, D. R. T.; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2015-01-01

    The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.

  10. Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

    PubMed

    Leem, Jung Woo; Lee, Hee Kwan; Jun, Dong-Hwan; Heo, Jonggon; Park, Won-Kyu; Park, Jin-Hong; Yu, Jae Su

    2014-03-10

    We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%). PMID:24922242

  11. Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.

    PubMed

    Leem, Jung Woo; Lee, Hee Kwan; Jun, Dong-Hwan; Heo, Jonggon; Park, Won-Kyu; Park, Jin-Hong; Yu, Jae Su

    2014-03-10

    We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (η) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., η~13%). PMID:24800289

  12. The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-09-01

    Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al2O3 or HfO2 dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO2 based capacitors compared to Al2O3 based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

  13. X-Ray Emission Spectra and Electronic Structures of Red Phosphorus, 3d Transition-Metal Phosphides and III V Compounds

    NASA Astrophysics Data System (ADS)

    Sugiura, Chikara

    1995-07-01

    The P Kβ emission spectra in fluorescence from red amorphous phosphorus, 3d transition-metal phosphides TiP, CrP, FeP, Fe2P, Fe3P, CoP, Co2P, Ni5P4, Ni2P, Ni3P, Cu3P, ZnP2 (black) and Zn3P2, and the semiconducting phosphides of the III-V type, BP, AlP, GaP and InP are measured with a high-resolution two-crystal vacuum spectrometer equipped with Ge(111) crystals. The influence of the metal atoms appears distinctly on the P Kβ fluorescence emission spectra. The measured spectra are compared with available X-ray emission and XPS valence-band spectra and theoretical energy-band calculations on a common energy scale. It is shown that considerable p-d, s mixing occurs in the valence bands of the 3d transition-metal phosphides and the P 3p states mix fairly with the P 3s states in the valence bands of red phosphorus, Gap and InP

  14. Systematic defect donor levels in III-V and II-VI semiconductors revealed by hybrid functional density-functional theory

    NASA Astrophysics Data System (ADS)

    Petretto, Guido; Bruneval, Fabien

    2015-12-01

    The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.

  15. The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

    SciTech Connect

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-09-07

    Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al{sub 2}O{sub 3} or HfO{sub 2} dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO{sub 2} based capacitors compared to Al{sub 2}O{sub 3} based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

  16. Halogen-containing compounds in solid source III-V molecular beam epitaxy, and their use for fabrication of high performance heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Micovic, Miroslav

    The theme of this dissertation is the improvement of III-V compound semiconductor heterojunction bipolar transistors (HBT's) through the use of iodine or bromine in molecular beam epitaxy (MBE). The motivation for this work is to increase the speed of AlGaAs/GaAs HBT's by reduction of base resistance and parasitic base-collector capacitance. The base resistance of an HBT can be minimized, without severely affecting the base transit time, by doping the base to the highest attainable level. It is demonstrated in this work that epitaxial layers suitable for fabrication of AlGaAs/GaAs HBT's with a carbon base doping level of up to 10sp{20} cmsp{-3} can be grown by solid source MBE using CBrsb4 as a doping precursor. The DC gain of HBT's with extremely heavily doped base layers was studied to determine the base thickness which will provide the lowest possible base resistance and a current gain still acceptable for fabrication of microwave HBT's. Use of iodine for in situ etching and surface cleaning of GaAs, AlGaAs and InGaAs and InGaAs in the MBE growth chamber is demonstrated for the first time. In-situ etching and growth capabilities integrated in the same chamber were used for fabrication of AlGaAs/GaAs HBT's with selectively buried sub-collectors for reduction of base-collector capacitance. Fabrication of these device structures was successfully demonstrated by MBE regrowth on pre-patterned sub-collector mesa structures. Growth of GaAs and AlGaAs layers under an intentional flux of Isb2 molecules was explored in molecular beam epitaxy. An improvement of material quality which coincides with the history of iodine use in the MBE chamber was observed.

  17. Absorption enhancement of GaInP nanowires by tailoring transparent shell thicknesses and its application in III-V nanowire/Si film two-junction solar cells.

    PubMed

    Li, Xinhua; Shi, Tongfei; Liu, Guangqiang; Wen, Long; Zhou, BuKang; Wang, Yuqi

    2015-09-21

    A non-absorbing transparent shell is proposed to be coated on the outer surface of the core photoactive GaInP nanowire array (NWA) of the III-V nanowire (NW)/Si film two-junction solar cell. Interestingly, the diluted (at the filling ratio of 0.25) GaInP NWA with core / transparent shell structure can absorb more light than that in bare denser (at the filling ratio of 0.5) NWA. This allows for less source material consumption during the fabrication of III-V NWA/Si film two-junction cell. Meanwhile, the condition of current matching between the top III-V NWA and Si film sub cell can be easily fulfilled by tailoring the coating thickness of the transparent coating. Beyond the advantages on light absorption, the surface passivation effects introduced by the addition of some transparent dielectric coatings can reduce the surface recombination rate at the top NWA sub cell surface. This facilitates the effective extraction of photo-generated carriers and enhances output stability of the top NWA sub cell. From electrical simulation, a power conversion efficiency of 29.9% can be obtained at the optimized coating geometry. PMID:26406728

  18. 30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... reverse airstream shall be approved by MSHA under the appliable requirements of 30 CFR part 18; (2) Drive belts and nonmetallic fan blades shall be constructed of static-conducting material; and (3) Aluminum alloy fan blades shall not contain more than 0.5 percent magnesium. . (d) When an internal...

  19. 30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... reverse airstream shall be approved by MSHA under the appliable requirements of 30 CFR part 18; (2) Drive belts and nonmetallic fan blades shall be constructed of static-conducting material; and (3) Aluminum alloy fan blades shall not contain more than 0.5 percent magnesium. . (d) When an internal...

  20. 30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... reverse airstream shall be approved by MSHA under the appliable requirements of 30 CFR part 18; (2) Drive belts and nonmetallic fan blades shall be constructed of static-conducting material; and (3) Aluminum alloy fan blades shall not contain more than 0.5 percent magnesium. . (d) When an internal...

  1. 30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... reverse airstream shall be approved by MSHA under the appliable requirements of 30 CFR part 18; (2) Drive belts and nonmetallic fan blades shall be constructed of static-conducting material; and (3) Aluminum alloy fan blades shall not contain more than 0.5 percent magnesium. . (d) When an internal...

  2. GaAsPN-based PIN solar cells MBE-grown on GaP substrates: toward the III-V/Si tandem solar cell

    NASA Astrophysics Data System (ADS)

    Da Silva, M.; Almosni, S.; Cornet, C.; Létoublon, A.; Levallois, C.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Durand, O.

    2015-03-01

    GaAsPN semiconductors are promising material for the elaboration of high efficiencies tandem solar cells on silicon substrates. GaAsPN diluted nitride alloy is studied as the top junction material due to its perfect lattice matching with the Si substrate and its ideal bandgap energy allowing a perfect current matching with the Si bottom cell. We review our recent progress in materials development of the GaAsPN alloy and our recent studies of some of the different building blocks toward the elaboration of a PIN solar cell. A lattice matched (with a GaP(001) substrate, as a first step toward the elaboration on a Si substrate) 1μm-thick GaAsPN alloy has been grown by MBE. After a post-growth annealing step, this alloy displays a strong absorption around 1.8-1.9 eV, and efficient photoluminescence at room temperature suitable for the elaboration of the targeted solar cell top junction. Early stage GaAsPN PIN solar cells prototypes have been grown on GaP (001) substrates, with 2 different absorber thicknesses (1μm and 0.3μm). The external quantum efficiencies and the I-V curves show that carriers have been extracted from the GaAsPN alloy absorbers, with an open-circuit voltage of 1.18 V, while displaying low short circuit currents meaning that the GaAsPN structural properties needs a further optimization. A better carrier extraction has been observed with the absorber displaying the smallest thickness, which is coherent with a low carriers diffusion length in our GaAsPN compound. Considering all the pathways for improvement, the efficiency obtained under AM1.5G is however promising.

  3. Investigating the growth, structural and electrical properties of III-V semiconductor nanopillars for the next-generation electronic and optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Lin, Andrew

    Extensive research efforts have been devoted to the study and development of III-V compound semiconductor nanowires (NWs) and nanopillars (NPs) because of their unique physical properties and ability to form high quality, highly lattice-mismatched axial and radial heterostructures. These advantages lead to precise nano-bandgap engineering to achieve new device functionalities. One unique and powerful approach to realize these NPs is by catalyst-free, selective-area epitaxy (SAE) via metal-organic chemical vapor deposition, in which the NP location and diameter can be precisely controlled lithographically. Early demonstrations of electronic and optoelectronic devices based on these NPs, however, are often inferior compared to their planar counterparts due to a few factors: (1) interface/surface states, (2) inaccurate doping calibration, and (3) increased carrier scattering and trapping from stacking fault formation in the NPs. In this study, the detailed growth mechanisms of different III-As, III-Sb and III-P NPs and their heterostructures are investigated. These NPs are then fabricated into single-NP field-effect transistors (FETs) to probe their electrical properties. It is shown that these devices are highly diameter-dependent, mainly because of the effects of surface states. By growing a high band-gap shell around the NP cores to passivate the surface, the device performance can be significantly improved. Further fabrication and characterization of vertical surround-gate FETs using a high-mobility InAs/InP NP channel is also discussed. Aside from the radial NP heterostructures, different approaches to achieve purely axial heterostructures in InAs/In(As)P materials are also presented with excellent interface quality. Both single barrier and double barrier structures are realized and fabricated into devices that show carrier transport characteristics over a barrier and even resonant tunneling behavior. Antimonide-based NPs are also studied for their immense application in high-speed electronics and mid-IR optoelectronics. Different growth regimes are probed to achieve InSb NPs and InAsSb NPs.

  4. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  5. Arsenic(III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: Modeling competitive adsorption consistent with spectroscopic and molecular evidence

    NASA Astrophysics Data System (ADS)

    Kanematsu, Masakazu; Young, Thomas M.; Fukushi, Keisuke; Green, Peter G.; Darby, Jeannie L.

    2013-04-01

    Adsorption of the two oxyanions, arsenate (As(V)) and arsenite (As(III)), on a common goethite-based granular porous adsorbent is studied in the presence of major co-existing ions in groundwater (i.e., phosphate, silicic acid, sulfate, carbonate, magnesium, and calcium) and predicted using the extended triple layer model (ETLM), a dipole modified single-site triple layer surface complexation model consistent with spectroscopic and molecular evidence. Surface species of all ions were selected according to the previous ETLM studies and published experimental spectroscopic/theoretical molecular information. The adsorption equilibrium constants for all ions were determined using adsorption data obtained in single-solute systems. The adsorption equilibrium constants referenced to the site-occupancy standard state (indicated by Kθ) were compared with those for goethite in the literature if available. The values of these constants for the goethite-based adsorbent are found to be close to the values for goethite previously studied. These "constrained" adsorption equilibrium constants determined in single-solute systems were used in the ETLM to predict the competitive interactions of As(III, V) with the co-existing ions in binary-solute systems. The ETLM is capable of predicting As(III, V) adsorption in the presence of oxyanions (phosphate, silicic acid, sulfate, and carbonate). This study presents the first successful and systematic prediction of the competitive interactions of As(III, V) with these oxyanions using the ETLM. The ETLM prediction of surface (and aqueous) speciation also provides insights into the distinct adsorption behavior of As(III, V) in the presence of the oxyanions. Magnesium and calcium significantly enhanced As(V) adsorption at higher pH values, while they had little effect on As(III) adsorption. The enhanced adsorption of As(V), however, could not be predicted by the ETLM using the surface species proposed in previous ETLM studies. Further studies are necessary to identify ternary complexes, especially at high pH. Adsorption isotherms of As(V), a dominant form of arsenic in adsorptive water treatment systems, in the presence of the co-existing ions under relevant conditions of water treatment systems are also obtained and predicted by the ETLM to study and compare the effect of the co-existing ions on As(V) removal.

  6. VANADIUM ALLOYS

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  7. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  8. Quantitative evaluation of microtwins and antiphase defects in GaP/Si nanolayers for a IIIV photonics platform on silicon using a laboratory X-ray diffraction setup1

    PubMed Central

    Ping Wang, Yan; Letoublon, Antoine; Nguyen Thanh, Tra; Bahri, Mounib; Largeau, Ludovic; Patriarche, Gilles; Cornet, Charles; Bertru, Nicolas; Le Corre, Alain; Durand, Olivier

    2015-01-01

    This study is carried out in the context of IIIV semiconductor monolithic integration on silicon for optoelectronic device applications. X-ray diffraction is combined with atomic force microscopy and scanning transmission electron microscopy for structural characterization of GaP nanolayers grown on Si. GaP has been chosen as the interfacial layer, owing to its low lattice mismatch with Si. But, microtwins and antiphase boundaries are still difficult to avoid in this system. Absolute quantification of the microtwin volume fraction is used for optimization of the growth procedure in order to eliminate these defects. Lateral correlation lengths associated with mean antiphase boundary distances are then evaluated. Finally, optimized growth conditions lead to the annihilation of antiphase domains within the first 10?nm. PMID:26089763

  9. ZIRCONIUM ALLOY

    DOEpatents

    Wilhelm, H.A.; Ames, D.P.

    1959-02-01

    A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

  10. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

    Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

  11. Nonswelling alloy

    DOEpatents

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  12. A standards-based method for compositional analysis by energy dispersive X-ray spectrometry using multivariate statistical analysis: application to multicomponent alloys.

    PubMed

    Rathi, Monika; Ahrenkiel, S P; Carapella, J J; Wanlass, M W

    2013-02-01

    Given an unknown multicomponent alloy, and a set of standard compounds or alloys of known composition, can one improve upon popular standards-based methods for energy dispersive X-ray (EDX) spectrometry to quantify the elemental composition of the unknown specimen? A method is presented here for determining elemental composition of alloys using transmission electron microscopy-based EDX with appropriate standards. The method begins with a discrete set of related reference standards of known composition, applies multivariate statistical analysis to those spectra, and evaluates the compositions with a linear matrix algebra method to relate the spectra to elemental composition. By using associated standards, only limited assumptions about the physical origins of the EDX spectra are needed. Spectral absorption corrections can be performed by providing an estimate of the foil thickness of one or more reference standards. The technique was applied to III-V multicomponent alloy thin films: composition and foil thickness were determined for various III-V alloys. The results were then validated by comparing with X-ray diffraction and photoluminescence analysis, demonstrating accuracy of approximately 1% in atomic fraction. PMID:23298470

  13. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A. B.

    1986-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys are addressed. Because the Bi compounds are not known to form zincblende structures, only the anion-substituted alloys InPBi, InAsBi, and InSbBi are considered candidates as narrow-gap semiconductors. Miscibility calculations indicate that InSbBi will be the most miscible, and InPBi, with the large lattice mismatch of the constituents, will be the most difficult to mix. Calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys, and substantially harder than the currently favored narrow-gap semiconductor HgCdTe. Thus, although InSbBi may be an easier material to prepare, InPBi promises to be a harder material. Growth of the Bi compounds will require high effective growth temperatures, probably attainable only through the use of nonequilibrium energy-assisted epitaxial growth techniques.

  14. Compound semiconductor alloys: From atomic-scale structure to bandgap bowing

    SciTech Connect

    Schnohr, C. S.

    2015-09-15

    Compound semiconductor alloys such as In{sub x}Ga{sub 1−x}As, GaAs{sub x}P{sub 1−x}, or CuIn{sub x}Ga{sub 1−x}Se{sub 2} are increasingly employed in numerous electronic, optoelectronic, and photonic devices due to the possibility of tuning their properties over a wide parameter range simply by adjusting the alloy composition. Interestingly, the material properties are also determined by the atomic-scale structure of the alloys on the subnanometer scale. These local atomic arrangements exhibit a striking deviation from the average crystallographic structure featuring different element-specific bond lengths, pronounced bond angle relaxation and severe atomic displacements. The latter, in particular, have a strong influence on the bandgap energy and give rise to a significant contribution to the experimentally observed bandgap bowing. This article therefore reviews experimental and theoretical studies of the atomic-scale structure of III-V and II-VI zincblende alloys and I-III-VI{sub 2} chalcopyrite alloys and explains the characteristic findings in terms of bond length and bond angle relaxation. Different approaches to describe and predict the bandgap bowing are presented and the correlation with local structural parameters is discussed in detail. The article further highlights both similarities and differences between the cubic zincblende alloys and the more complex chalcopyrite alloys and demonstrates that similar effects can also be expected for other tetrahedrally coordinated semiconductors of the adamantine structural family.

  15. Aluminum alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B. (Inventor); Starke, Edgar A., Jr. (Inventor)

    1989-01-01

    This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

  16. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

    The preparation of low-melting-point plutonium alloys is described. In a MgO crucible Pu is placed on top of the lighter alloying metal (Fe, Co, or Ni) and the temperature raised to 1000 or 1200 deg C. Upon cooling, the alloy slug is broke out of the crucible. With 14 at. % Ni the m.p. is 465 deg C; with 9.5 at. % Fe the m.p. is 410 deg C; and with 12.0 at. % Co the m.p. is 405 deg C. (T.R.H.) l6262 l6263 ((((((((Abstract unscannable))))))))

  17. Multiple doping of silicon-germanium alloys for thermoelectric applications

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

    1989-01-01

    It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

  18. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  19. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  20. Systematic approach for simultaneously correcting the band-gap andp-dseparation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

    DOE PAGESBeta

    Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

    2015-07-31

    We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X = N,P,As,Sb, and II-VI compounds, (Zn or Cd)X, with X = O,S,Se,Te. By correcting (1) the binary band gaps at high-symmetry points , L, X, (2) the separation of p-and d-orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles methodmore » can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.« less

  1. Systematic approach for simultaneously correcting the band-gap and p -d separation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

    2015-07-01

    We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X =N ,P ,As ,Sb , and II-VI compounds, (Zn or Cd)X , with X =O ,S ,Se ,Te . By correcting (1) the binary band gaps at high-symmetry points Γ , L , X , (2) the separation of p -and d -orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles method can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.

  2. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  3. Hybrid III-V Silicon Lasers

    NASA Astrophysics Data System (ADS)

    Bowers, John

    2014-03-01

    Abstract: A number of important breakthroughs in the past decade have focused attention on Si as a photonic platform. We review here recent progress in this field, focusing on efforts to make lasers, amplifiers, modulators and photodetectors on or in silicon. We also describe optimum quantum well design and distributed feedback cavity design to reduce the threshold and increase the efficiency and power output. The impact active silicon photonic integrated circuits could have on interconnects, telecommunications and on silicon electronics is reviewed. Biography: John Bowers holds the Fred Kavli Chair in Nanotechnology, and is the Director of the Institute for Energy Efficiency and a Professor in the Departments of Electrical and Computer Engineering and Materials at UCSB. He is a cofounder of Aurrion, Aerius Photonics and Calient Networks. Dr. Bowers received his M.S. and Ph.D. degrees from Stanford University and worked for AT&T Bell Laboratories and Honeywell before joining UC Santa Barbara. Dr. Bowers is a member of the National Academy of Engineering and a fellow of the IEEE, OSA and the American Physical Society. He is a recipient of the OSA/IEEE Tyndall Award, the OSA Holonyak Prize, the IEEE LEOS William Streifer Award and the South Coast Business and Technology Entrepreneur of the Year Award. He and coworkers received the EE Times Annual Creativity in Electronics (ACE) Award for Most Promising Technology for the hybrid silicon laser in 2007. Bowers' research is primarily in optoelectronics and photonic integrated circuits. He has published ten book chapters, 600 journal papers, 900 conference papers and has received 54 patents. He has published 180 invited papers and conference papers, and given 16 plenary talks at conferences. As well as Chong Zhang.

  4. GaSb based ternary and quaternary diffused junction devices for TPV applications

    SciTech Connect

    Sundaram, V.S.; Saban, S.B.; Morgan, M.D.; Horne, W.E.; Evans, B.D.; Ketterl, J.R.; Morosini, M.B.; Patel, N.B.; Field, H.

    1997-03-01

    In this work we report the characteristics of ternary, GaInSb (Eg=0.70eV) and quarternary, GaInAsSb (Eg=0.5eV) diffused junction photovoltaic devices. The unique feature of the quarternary device is the extended long-wavelength response to 2.1 microns enabling the efficient use of the blackbody-like thermal sources operating at 1373 K in thermophotovoltaic energy conversion systems. The ternary device was fabricated by diffusing zinc into a n-type (100) oriented GaInSb substrate. For the quarternary, a four micron thick Te doped GaInAsSb layer grown by LPE on a n-type GaSb(100) wafer was used as the starting substrate for zinc diffusion. The ternary device exhibits an open circuit voltage of 0.38 V, Fill Factor of 0.63 and a short circuit current of 0.8A/cm{sup 2}, while the corresponding values for the quarternary device are 0.25 V, 0.58 and 0.8A/cm{sup 2}, respectively. The peak internal quantum efficiency for the ternary is over 90{percent} and that of the quarternary is above 75{percent}. Process optimization should improve the performance charcateristics of the quarternary. {copyright} {ital 1997 American Institute of Physics.}

  5. Distributed feedback GaSb based laser diodes with buried grating

    SciTech Connect

    Gaimard, Q.; Cerutti, L.; Teissier, R.; Vicet, A.

    2014-04-21

    We report on the growth, fabrication, and experimental study of distributed feed-back antimonide diode lasers with buried grating. A second order index-coupled grating was defined by interferometric lithography on the top of the laser waveguide and dry etched by reactive ion etching. The grating was then buried thanks to an overgrowth of the top cladding layer using molecular beam epitaxy. The wafer was then processed using standard photolithography and wet etching into 15 μm-wide laser ridges. Single frequency laser emission at a wavelength of 2.2 μm was measured with a side mode suppression ratio of 34 dB, a maximum output power of 30 mW, and a total continuous tuning range of 6.5 nm.

  6. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

  7. Electroluminescence and phototrigger effect in single crystals of GaS{sub x}Se{sub 1-x} alloys

    SciTech Connect

    Kyazym-Zade, A. G. Salmanov, V. M.; Mokhtari, A. G.; Dadashova, V. V.; Agaeva, A. A.

    2008-05-15

    The effects of switching and electroluminescence as well as the interrelation between these effects in single crystals of GaS{sub x}Se{sub 1-x} alloys are detected and studied. It is established that the threshold voltage for switching depends on temperature, resistivity, and composition of alloys, and also on the intensity and spectrum of photoactive light. As a result, a phototrigger effect is observed; this effect arises under irradiation with light from the fundamental-absorption region. Electroluminescence is observed in the subthreshold region of the current-voltage characteristic; the electroluminescence intensity decreases drastically to zero as the sample is switched from a high-resistivity state to a low-resistivity state. Experimental data indicating that the electroluminescence and the switching effect are based on the injection mechanism (as it takes place in other layered crystals of the III-V type) are reported.

  8. First-principles calculation on dilute magnetic alloys in zinc blend crystal structure

    NASA Astrophysics Data System (ADS)

    Ullah, Hamid; Inayat, Kalsoom; Khan, S. A.; Mohammad, S.; Ali, A.; Alahmed, Z. A.; Reshak, A. H.

    2015-07-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic alloys in zinc blende structure. The first-principles study is carried out on Mn doped III-V semiconductors. The calculated band structures, electronic properties and magnetic properties of Ga1-xMnxX (X=P, As) compounds reveal that Ga0.75Mn0.25P is half metallic turned to be metallic with increasing x to 0.5 and 0.75, whereas substitute P by As cause to maintain the half-metallicity nature in both of Ga0.75Mn0.25As and Ga0.5Mn0.5As and tune Ga0.25Mn0.75As to be metallic. Calculated total magnetic moments and the robustness of half-metallicity of Ga0.75Mn0.25P, Ga0.75Mn0.25As and Ga0.5Mn0.5As with respect to the variation in lattice parameters are also discussed. The predicted theoretical evidence shows that some Mn-doped III-V semiconductors can be effectively used in spintronic devices.

  9. Towards III-V solar cells on Si: Improvement in the crystalline quality of Ge-on-Si virtual substrates through low porosity porous silicon buffer layer and annealing

    NASA Astrophysics Data System (ADS)

    Calabrese, Gabriele; Baricordi, Stefano; Bernardoni, Paolo; Fin, Samuele; Guidi, Vincenzo; Vincenzi, Donato

    2014-09-01

    A comparison between the crystalline quality of Ge grown on bulk Si and on a low porosity porous Si (pSi) buffer layer using low energy plasma enhanced chemical vapor deposition is reported. Omega/2Theta coupled scans around the Ge and Si (004) diffraction peaks show a reduction of the Ge full-width at half maximum (FWHM) of 22.4% in presence of the pSi buffer layer, indicating it is effective in improving the epilayer crystalline quality. At the same time atomic force microscopy analysis shows an increase in root means square roughness for Ge grown on pSi from 38.5 nm to 48.0 nm, as a consequence of the larger surface roughness of pSi compared to bulk Si. The effect of 20 minutes vacuum annealing at 580°C is also investigated. The annealing leads to a FWHM reduction of 23% for Ge grown on Si and of 36.5% for Ge on pSi, resulting in a FWHM of 101 arcsec in the latter case. At the same time, the RMS roughness is reduced of 8.8% and of 46.5% for Ge grown on bulk Si and on pSi, respectively. The biggest improvement in the crystalline quality of Ge grown on pSi with respect to Ge grown on bulk Si observed after annealing is a consequence of the simultaneous reorganization of the Ge epilayer and the buffer layer driven by energy minimization. A low porosity buffer layer can thus be used for the growth of low defect density Ge on Si virtual substrates for the successive integration of III-V multijunction solar cells on Si. The suggested approach is simple and fast -thus allowing for high throughput-, moreover is cost effective and fully compatible with subsequent wafer processing. Finally it does not introduce new chemicals in the solar cell fabrication process and can be scaled to large area silicon wafers.

  10. Towards III-V solar cells on Si: Improvement in the crystalline quality of Ge-on-Si virtual substrates through low porosity porous silicon buffer layer and annealing

    SciTech Connect

    Calabrese, Gabriele; Baricordi, Stefano; Bernardoni, Paolo; Fin, Samuele; Guidi, Vincenzo; Vincenzi, Donato

    2014-09-26

    A comparison between the crystalline quality of Ge grown on bulk Si and on a low porosity porous Si (pSi) buffer layer using low energy plasma enhanced chemical vapor deposition is reported. Omega/2Theta coupled scans around the Ge and Si (004) diffraction peaks show a reduction of the Ge full-width at half maximum (FWHM) of 22.4% in presence of the pSi buffer layer, indicating it is effective in improving the epilayer crystalline quality. At the same time atomic force microscopy analysis shows an increase in root means square roughness for Ge grown on pSi from 38.5 nm to 48.0 nm, as a consequence of the larger surface roughness of pSi compared to bulk Si. The effect of 20 minutes vacuum annealing at 580°C is also investigated. The annealing leads to a FWHM reduction of 23% for Ge grown on Si and of 36.5% for Ge on pSi, resulting in a FWHM of 101 arcsec in the latter case. At the same time, the RMS roughness is reduced of 8.8% and of 46.5% for Ge grown on bulk Si and on pSi, respectively. The biggest improvement in the crystalline quality of Ge grown on pSi with respect to Ge grown on bulk Si observed after annealing is a consequence of the simultaneous reorganization of the Ge epilayer and the buffer layer driven by energy minimization. A low porosity buffer layer can thus be used for the growth of low defect density Ge on Si virtual substrates for the successive integration of III-V multijunction solar cells on Si. The suggested approach is simple and fast –thus allowing for high throughput-, moreover is cost effective and fully compatible with subsequent wafer processing. Finally it does not introduce new chemicals in the solar cell fabrication process and can be scaled to large area silicon wafers.

  11. Interacting quasi-band model for electronic states in compound semiconductor alloys: Zincblende structure

    NASA Astrophysics Data System (ADS)

    Shinozuka, Yuzo; Oda, Masato

    2015-09-01

    The interacting quasi-band model proposed for electronic states in simple alloys is extended for compound semiconductor alloys with general lattice structures containing several atoms per unit cell. Using a tight-binding model, a variational electronic wave function for quasi-Bloch states yields a non-Hermitian Hamiltonian matrix characterized by matrix elements of constituent crystals and concentration of constituents. Solving secular equations for each k-state yields the alloy’s energy spectrum for any type of randomness and arbitrary concentration. The theory is used to address III-V (II-VI) alloys with a zincblende lattice with crystal band structures well represented by the sp3s* model. Using the resulting 15 × 15 matrix, the concentration dependence of valence and conduction bands is calculated in a unified scheme for typical alloys: Al1-xGaxAs, GaAs1-xPx, and GaSb1-xPx. Results agree well with experiments and are discussed with respect to the concentration dependence, direct-indirect gap transition, and band-gap-bowing origin.

  12. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, O.B.; Lear, K.L.

    1998-03-10

    The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

  13. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, Olga B.; Lear, Kevin L.

    1998-01-01

    A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

  14. Metal alloy identifier

    DOEpatents

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  15. Turbine Blade Alloy

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca

    2001-01-01

    The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.

  16. Cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Sandrock, G. D.; Freche, J. C. (Inventor)

    1973-01-01

    A microstructurally stable, high strength cobalt based alloy for use at elevated temperatures to 2125 F was developed. The alloys are particularly directed for use in stators and other low stress components in advanced gas turbines.

  17. Theory of the electronic properties of mercury-cadmium-telluride alloys

    NASA Astrophysics Data System (ADS)

    Chen, A. B.; Sher, A.

    1984-02-01

    An accurate band-structure theory for semiconductor alloys was achieved. It has been successfully applied to Mercury-Cadmium-Telluride alloys (MCT), and is being extended to III-V and other II-VI semiconductor alloys. As a result of this research, ten papers have been published. Several other papers and one book are in progress. The most important finding was the origin of the major disorder and its effects on different parts of the band structure. The large s-energy fluctuation between the Hg and Cd sites was found to cause a large smearing in the density of states about 5 eV below the top of the valence band, but it produced very little bowing and scattering for the states near the band gap. A detailed study of these facts accounts for the lattice instability of MCT and its very high electron mobility. Another significant result is that, while Cd weakens a neighboring Hg-Te bond, Zn strengthens it. Such structural studies may help resolve the adverse structural difficulties affecting MCT as an infrared material.

  18. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  19. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  20. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  1. High strength alloys

    DOEpatents

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  2. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  3. Nanocrystalline films of soft magnetic iron-based alloys

    NASA Astrophysics Data System (ADS)

    Sheftel', E. N.; Bannykh, O. A.

    2006-10-01

    The physicochemical and structural aspects of designing soft magnetic alloys Fe- MX (where M is a Group III V metal of the periodic table and X = C, N, O) in the form of nanocrystalline films precipitation-hardened by refractory interstitial phases are discussed and developed. The results of studying the structure and magnetic properties of Fe78Zr10N12 films are reported. The films in the amorphous state are produced by reactive magnetron sputtering. Upon annealing at 300 600°C, the amorphous films crystallize to form mainly a bcc α-Fe-based phase and the fcc ZrN phase. The grain size of the bcc phase is shown to increase from ˜3 nm to ˜30 nm as the annealing temperature increases; the grain size of the fcc phase does not exceed 2 3 nm. Films annealed at 400°C exhibit a record level of magnetic properties: H c = 5 6 A/m and B s = 1.7 1.8 T. The experimental results obtained confirm the validity of our scientific approach.

  4. Spark alloying of an AL9 alloy by hard alloys

    NASA Astrophysics Data System (ADS)

    Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.

    2015-08-01

    The phase compositions of spark coatings of Kh12M steel with a VT1-0 (titanium) alloy and T15K6 and T30K4 hard alloys are studied. It is shown that the TiC titanium carbide forms in all cases and tungsten carbide decomposes with the formation of tungsten in a coating. These processes are intensified by increasing time, capacitance, and frequency. The surface hardness, the sample weight, and the white layer thickness increase monotonically.

  5. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  6. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  7. PLUTONIUM-ZIRCONIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.; Waber, J.T.

    1960-08-30

    A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

  8. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  9. Low activation ferritic alloys

    DOEpatents

    Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

    1985-02-07

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  10. Low activation ferritic alloys

    DOEpatents

    Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  11. NICKEL-BASE ALLOY

    DOEpatents

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  12. Scanning tunneling microscopy of compound semiconductor heterostructures: From alloy ordering to composition determination

    NASA Astrophysics Data System (ADS)

    Liu, Ning

    Cross-sectional scanning tunneling microscopy (XSTM) has been employed to explore various material properties of III-V compound semiconductor heterostructures. Regarding GaInP alloys, the (111)-type alloy ordering is observed in organometallic vapor phase epitaxy (OMVPE) grown alloy region, while the molecular beam epitaxy (MBE) grown region shows a very small degree of ordering. Two types of ordering, namely (InP)1(GaP)1 and (InP)2(GaP) 1, have been found in OMVPE grown GaInP alloys. Then, the focus is shifted to the structural properties of self-assembled InGaAs quantum dots (QDs) grown by migration enhanced epitaxy (MEE) and heterogeneous droplet epitaxy (HDE) respectively. Size, shape, orientation, spatial distribution, strain, and composition have been examined. Regarding MEE grown InGaAs QDs, the composition appears highly non-uniform, with an Indium-rich core having an inverted-triangle shape. With atomic resolution, compositional analysis has been done for both the QDs and wetting layers quantitatively. Depletion of the wetting layer, due to the formation of the QDs, is also demonstrated. For HDE grown InGaAs QDs, the size, shape, composition, and strain, etc., are quite different from that of MEE or MBE grown InGaAs QDs. Indium distribution inside the QDs is rather uniform compared with MEE grown InGaAs QDs. More importantly, it is found that the self-compensation between the size and indium concentration of the QDs appears to be the key factor that controls the sharpness of the photoluminescence (PL) linewidths in the investigated samples.

  13. Contact mechanisms and design principles for alloyed ohmic contacts to n-GaN

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2004-06-01

    Contact mechanisms and design principles of alloyed ohmic contacts to n-GaN are investigated. For the investigation, both tunnel contacts and thermionic contacts are considered. While the tunnel contacts include the Ti/Al/Ti/Au, Ti/Al/Ni/Au, Ti/Al/Pd/Au, (Ta,Ti)/Ni/Au, Ti/Al/Mo/Au, and Ti/Au/Pd/Au contacts, the thermionic contacts include the Ni/Au contacts. The proposed design principles correctly dictate the characteristics of all these contacts. At present, tunneling is believed to be the primary mechanism for low resistivity of the tunnel contacts. The present study demonstrates that both tunneling and thermionic emission are equally important for the low resistivity of these contacts. Band-gap narrowing and/or image force lowering due to heavy doping also contribute to the resistivity reduction of these contacts. An exciting feature of the present study is the observation of a very low work function intermetallic alloy formed during annealing of an appropriate combination of large work function metals. If the annealing conditions are optimized, the contacts become very robust, thermally stable, and lowly resistive with thermionic emission as the primary mechanism for electron transport. The observation is very promising and has potential to open up avenues for different types of thermionic contacts. The fundamental physics underlying the design principles are discussed. These principles are general enough to be applicable to other III-V nitrides, at the least.

  14. In situ measurement of CuPt alloy ordering using strain anisotropy

    SciTech Connect

    France, Ryan M.; McMahon, William E.; Kang, Joongoo; Steiner, Myles A.; Geisz, John F.

    2014-02-07

    The optical and electrical properties of many III-V alloys change with the degree of CuPt atomic ordering, which is very sensitive to growth conditions. The bulk ordered alloy is elongated along the normal to the ordered planes, and is asymmetrically strained when coherent to a cubic substrate. Here, we demonstrate in situ measurement of the anisotropic strain due to ordering using two-dimensional wafer curvature. The measurement is sensitive to bulk anisotropies, and so is complementary to other in situ measurements that are sensitive to surface anisotropies. Using ab initio calculations, we determine a maximum strain anisotropy of 0.27% between [110] and [1{sup ¯}10] when perfectly ordered single-variant GaInP{sub 2} is coherent to a (001) cubic substrate. We relate the in situ measurement of strain anisotropy on various GaInP{sub 2} samples to ex situ measurements of the order parameter to validate the measurement and confirm the capability to predict material properties. The measurement monitors change in ordering during growth, useful for quickly determining the growth condition dependence of ordering or monitoring order-disorder transitions. More generally, this measurement technique could, in principle, be used to monitor phase changes in any epitaxial system for which the strain anisotropy of the two phases differs.

  15. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  16. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  17. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  18. Copper-tantalum alloy

    DOEpatents

    Schmidt, Frederick A.; Verhoeven, John D.; Gibson, Edwin D.

    1986-07-15

    A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.

  19. Surface composition of alloys

    NASA Astrophysics Data System (ADS)

    Sachtler, W. M. H.

    1984-11-01

    In equilibrium, the composition of the surface of an alloy will, in general, differ from that of the bulk. The broken-bond model is applicable to alloys with atoms of virtually equal size. If the heat of alloy formation is zero, the component of lower heat of atomization is found enriched in the surface. If both partners have equal heats of sublimination, the surface of a diluted alloy is enriched with the minority component. Size effects can enhance or weaken the electronic effects. In general, lattice strain can be relaxed by precipitating atoms of deviating size on the surface. Two-phase alloys are described by the "cherry model", i.e. one alloy phase, the "kernel" is surrounded by another alloy, the "flesh", and the surface of the outer phase, the "skin" displays a deviating surface composition as in monophasic alloys. In the presence of molecules capable of forming chemical bonds with individual metal atoms, "chemisorption induced surface segregation" can be observed at low temperatures, i.e. the surface becomes enriched with the metal forming the stronger chemisorption bonds.

  20. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  1. Cesium iodide alloys

    DOEpatents

    Kim, H.E.; Moorhead, A.J.

    1992-12-15

    A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.

  2. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  3. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  4. Nickel base coating alloy

    NASA Technical Reports Server (NTRS)

    Barrett, C. A. (Inventor); Lowell, C. E. (Inventor)

    1986-01-01

    Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C.

  5. Alloys in energy development

    SciTech Connect

    Frost, B.R.T.

    1984-02-01

    The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

  6. Synthesizing Aluminum alloys by double mechanical alloying

    NASA Astrophysics Data System (ADS)

    Froyen, L.; Delaey, L.; Niu, X. P.; Le Brun, P.; Peytour, C.

    1995-03-01

    A new synthesis technique, namely double mechanical alloying (dMA), has been developed to fabricate aluminum alloys containing the finely distributed intermetallic compounds and inert dispersoids Al4C3 and Al2O3 The technique consists mainly of three steps: a primary milling stage of elemental powders (MAI) followed by a heat treatment to promote the formation of intermetallic phases, a secondary milling stage (MA2) to refine the microstructure, and consolidation of the produced powders. The results of mechanical and tribological properties of the resulting materials indicate that the dMA is a promising technique for the fabrication of aluminum alloys for applications requiring wear resistance and high-temperature performance.

  7. Low resistivity lateral P-I-N junction formed by Ni-InGaAsP alloy for carrier injection InGaAsP photonic devices

    NASA Astrophysics Data System (ADS)

    Park, Jin-Kwon; Takenaka, Mitsuru; Takagi, Shinichi

    2016-04-01

    In this study, we investigate low-resistivity InGaAsP lateral P-I-N junctions using Ni-InGaAsP alloy in conjunction with Zn diffusion. It is found that Ni-InGaAsP alloy is formed via a direct reaction between Ni and InGaAsP after annealing at more than 300 °C. The Ni-InGaAsP preserves the initial Schottky junction properties between Ni and InGaAsP, and thus exhibits an ohmic contact for n-InGaAsP and a Schottky contact for p-InGaAsP. Hence, the Ni-InGaAsP alloy can be used instead of the Si ion implantation process to form the P-I-N junction. The Ni-InGaAsP alloy exhibits significantly lower contact resistance and sheet resistance than Si implanted n+-InGaAsP. The InGaAsP lateral P-I-N junction formed with the Ni-InGaAsP alloy and Zn diffusion shows approximately 10 times lower access resistance than the n+-InGaAsP junction. Thus, we successfully achieve large on-current in the lateral P-I-N junction with the Ni-InGaAsP alloy. The fabrication procedure of the lateral P-I-N junction using the Ni-InGaAsP alloy is promising for carrier-injection photonic devices on the III-V CMOS photonics platform.

  8. First-principles calculations of bismuth induced changes in the band structure of dilute Ga-V-Bi and In-V-Bi alloys: chemical trends versus experimental data

    NASA Astrophysics Data System (ADS)

    Polak, M. P.; Scharoch, P.; Kudrawiec, R.

    2015-09-01

    Bi-induced changes in the band structure of Ga-V-Bi and In-V-Bi alloys are calculated within the density functional theory (DFT) for alloys with Bi ≤3.7% and the observed chemical trends are discussed in the context of the virtual crystal approximation (VCA) and the valence band anticrossing (VBAC) model. It is clearly shown that the incorporation of Bi atoms into III-V host modifies both the conduction band (CB) and the valence band (VB). The obtained shifts of bands in GaP1-xBix, GaAs1-xBix, GaSb1-xBix, InP1-xBix, InAs1-xBix, and InSb1-xBix are respectively, 15, -29, -16, -27, -15, and -10 meV/%Bi for CB, 82, 62, 16, 79, 45, and 16 meV/%Bi for VB, and -17, -3, -2, -8, -6, and 14 meV/%Bi for spin-orbit split off band. The Bi-induced reduction of the band gap is very consistent with the available experimental data. The chemical trends observed in our calculations as well as in experimental data are very clear: in a sequence of alloys from III-P-Bi to III-Sb-Bi the Bi-induced changes in the band structure weaken. For dilute GaSb1-xBix and InSb1-xBix alloys the band structure modification, in the first approximation, can be described within the VCA, while for Ga-V-Bi and In-V-Bi alloys with V = As or P another phenomenological approach is needed to predict the Bi-induced changes in their band structure. We have found that a combination of the VCA with the VBAC model, which is widely applied for highly mismatched alloys, is suitable for this purpose. The chemical trends for III-V-Bi alloys observed in our DFT calculations are also exhibited by the coupling parameter {C}BiM, which describes the magnitude of interaction between Bi-induced levels and VB states in the VBAC model. This coupling parameter monotonously decreases along the sequence of alloys from III-P-Bi to III-Sb-Bi.

  9. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  10. THORIUM-SILICON-BERYLLIUM ALLOYS

    DOEpatents

    Foote, F.G.

    1959-02-10

    Th, Si, anol Bt alloys where Be and Si are each present in anmounts between 0.1 and 3.5% by weight and the total weight per cent of the minor alloying elements is between 1.5 and 4.5% are discussed. These ternary alloys show increased hardness and greater resistant to aqueous corrosion than is found in pure Th, Th-Si alloys, or Th-Be alloys.

  11. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  12. (Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units

    SciTech Connect

    Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J.; Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J.

    2012-01-09

    An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

  13. Lattice constant grading in the Al.sub.y Ca.sub.1-y As.sub.1-x Sb.sub.x alloy system

    DOEpatents

    Moon, Ronald L.

    1981-01-01

    Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5.mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photovoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of the growing layer.

  14. Lattice constant grading in the Al.sub.y Ga.sub.1-y As.sub.1-x Sb.sub.x alloy system

    DOEpatents

    Moon, Ronald L.

    1980-01-01

    Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5 .mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photolvoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of growing layer.

  15. Brazing dissimilar aluminum alloys

    NASA Technical Reports Server (NTRS)

    Dalalian, H.

    1979-01-01

    Dip-brazing process joins aluminum castings to aluminum sheet made from different aluminum alloy. Process includes careful cleaning, surface preparation, and temperature control. It causes minimum distortion of parts.

  16. Electroplating on titanium alloy

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1971-01-01

    Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

  17. PLUTONIUM-URANIUM ALLOY

    DOEpatents

    Coffinberry, A.S.; Schonfeld, F.W.

    1959-09-01

    Pu-U-Fe and Pu-U-Co alloys suitable for use as fuel elements tn fast breeder reactors are described. The advantages of these alloys are ease of fabrication without microcracks, good corrosion restatance, and good resistance to radiation damage. These advantages are secured by limitation of the zeta phase of plutonium in favor of a tetragonal crystal structure of the U/sub 6/Mn type.

  18. (NH{sub 4})[V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}]: A new mixed valence vanadium(III,IV) fluoro-arsenate with ferromagnetic interactions and electronic conductivity

    SciTech Connect

    Berrocal, Teresa

    2009-01-15

    A new mixed valence vanadium(III,IV) fluoro-arsenate compound, with formula (NH{sub 4})[V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}] and KTP structure-type, has been synthesized by mild hydrothermal techniques. The crystal structure has been solved from single crystal X-ray diffraction data in the Pna2{sub 1} orthorhombic space group. The unit-cell parameters are a=13.196(2) A, b=6.628(1) A and c=10.7379(7) A with Z=8. The final R factors were R1=0.0438 and wR2=0.0943 [all data]. The crystal structure consists of a three-dimensional framework formed by (V{sup III,IV}O{sub 4}F{sub 2}) octahedra and (AsO{sub 4}){sup 3-} tetrahedra arsenate oxoanions. The vanadium(III,IV) cations, from the (V{sup III,IV}O{sub 4}F{sub 2}) octahedra, are linked through the fluorine atoms giving rise to zigzag chains. The ammonium cations are located in the cavities of the structure compensating the anionic charge of the [V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}]{sup -} inorganic skeleton. The thermal stability limit of the phase is 345 deg. C, around to this temperature the ammonium cation and fluoride anion are lost. The IR spectrum shows the characteristic bands of the (NH{sub 4}){sup +} and (AsO{sub 4}){sup 3-} ions. Magnetic measurements indicate the existence of weak ferromagnetic interactions. Electronic conductivity, via a hopping mechanism, occurs with an activation energy of 0.66 eV. - Graphical abstract: Polyhedral view of the crystal structure of (NH{sub 4})[V{sup III}{sub 1-x}V{sup IV}{sub x}(AsO{sub 4})F{sub 1-x}O{sub x}].

  19. Systematic approach for simultaneously correcting the band-gap andp-dseparation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

    SciTech Connect

    Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

    2015-07-31

    We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X = N,P,As,Sb, and II-VI compounds, (Zn or Cd)X, with X = O,S,Se,Te. By correcting (1) the binary band gaps at high-symmetry points , L, X, (2) the separation of p-and d-orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles method can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.

  20. Hot Microfissuring in Nickel Alloy

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.; Nunes, A.

    1984-01-01

    Experiments in intergranular cracking of nickel alloy near solidus temperature discussed in contractor report. Purpose of investigation development of schedule for welding, casting, forging, or other processing of alloy without causing microfissuring.

  1. Finding the Alloy Genome

    NASA Astrophysics Data System (ADS)

    Hart, Gus L. W.; Nelson, Lance J.; Zhou, Fei; Ozolins, Vidvuds

    2012-10-01

    First-principles codes can nowadays provide hundreds of high-fidelity enthalpies on thousands of alloy systems with a modest investment of a few tens of millions of CPU hours. But a mere database of enthalpies provides only the starting point for uncovering the ``alloy genome.'' What one needs to fundamentally change alloy discovery and design are complete searches over candidate structures (not just hundreds of known experimental phases) and models that can be used to simulate both kinetics and thermodynamics. Despite more than a decade of effort by many groups, developing robust models for these simulations is still a human-time-intensive endeavor. Compressive sensing solves this problem in dramatic fashion by automatically extracting the ``sparse model'' of an alloy in only minutes. This new paradigm to model building has enabled a new framework that will uncover, automatically and in a general way across the periodic table, the important components of such models and reveal the underlying ``genome'' of alloy physics.

  2. Si-Ge-Sn alloys with 1.0 eV gap for CPV multijunction solar cells

    SciTech Connect

    Roucka, Radek Clark, Andrew; Landini, Barbara

    2015-09-28

    Si-Ge-Sn ternary group IV alloys offer an alternative to currently used 1.0 eV gap materials utilized in multijunction solar cells. The advantage of Si-Ge-Sn is the ability to vary both the bandgap and lattice parameter independently. We present current development in fabrication of Si-Ge-Sn alloys with gaps in the 1.0 eV range. Produced material exhibits excellent structural properties, which allow for integration with existing III-V photovoltaic cell concepts. Time dependent room temperature photoluminescence data demonstrate that these materials have long carrier lifetimes. Absorption tunable by compositional changes is observed. As a prototype device set utilizing the 1 eV Si-Ge-Sn junction, single junction Si-Ge-Sn device and triple junction device with Si-Ge-Sn subcell have been fabricated. The resulting I-V and external quantum efficiency data show that the Si-Ge-Sn junction is fully functional and the performance is comparable to other 1.0 eV gap materials currently used.

  3. Si-Ge-Sn alloys with 1.0 eV gap for CPV multijunction solar cells

    NASA Astrophysics Data System (ADS)

    Roucka, Radek; Clark, Andrew; Landini, Barbara

    2015-09-01

    Si-Ge-Sn ternary group IV alloys offer an alternative to currently used 1.0 eV gap materials utilized in multijunction solar cells. The advantage of Si-Ge-Sn is the ability to vary both the bandgap and lattice parameter independently. We present current development in fabrication of Si-Ge-Sn alloys with gaps in the 1.0 eV range. Produced material exhibits excellent structural properties, which allow for integration with existing III-V photovoltaic cell concepts. Time dependent room temperature photoluminescence data demonstrate that these materials have long carrier lifetimes. Absorption tunable by compositional changes is observed. As a prototype device set utilizing the 1 eV Si-Ge-Sn junction, single junction Si-Ge-Sn device and triple junction device with Si-Ge-Sn subcell have been fabricated. The resulting I-V and external quantum efficiency data show that the Si-Ge-Sn junction is fully functional and the performance is comparable to other 1.0 eV gap materials currently used.

  4. Chemical beam epitaxy growth of IIIV semiconductor nanowires

    SciTech Connect

    Mohummed Noori, Farah T.

    2013-12-16

    Indium- Arsenide (InAs) nanowires were grown in a high vacuum chemical beam epitaxy (CBE) unit on InAs(111) wafers substrates at 425454C. Two types of nanogold were used as orientation catalyst, 40nm and 80nm. The measurements were performed using scanning electron microscopy showed that uniform nanowires. The nanowires orient vertically in the InAs nanowire scanning electron microscopy of an array 80nm diameter InAs nanowire with length is in the range 0.51 ?m and of an array 40nm diameter with length is in the range 0.30.7?m. The nanowire length with growth time shows that the linear increase of nanowires start to grow as soon as TMIn is available. The growth rate with temperature was studied.

  5. Monolithic III-V/Silicon Spatial Light Modulator

    NASA Technical Reports Server (NTRS)

    Maserjian, Joseph; Eng, Sverre T.

    1989-01-01

    Current techniques for growth of device-quality GaAs on silicon substrates enables fabrication of silicon-based version of photodiode-coupled spatial light modulator. Monolithic photodiode-coupled light-modulator array constructed on silicon substrate by growing InAs/GaAs multiple-quantum-wells over silicon PIN diode layer. Intermediate GaAs buffer layer confines attice-misfit dislocations to vicinity of silicon. Use of silicon makes available wider range of auxiliary on-chip signal-processing circuitry for coding and decoding of data, addition or subtraction of brightness levels, spatial reformatting, and rescaling.

  6. Long-Lived Hot Carriers in III-V Nanowires.

    PubMed

    Tedeschi, D; De Luca, M; Fonseka, H A; Gao, Q; Mura, F; Tan, H H; Rubini, S; Martelli, F; Jagadish, C; Capizzi, M; Polimeni, A

    2016-05-11

    Heat management mechanisms play a pivotal role in driving the design of nanowire (NW)-based devices. In particular, the rate at which charge carriers cool down after an external excitation is crucial for the efficiency of solar cells, lasers, and high-speed transistors. Here, we investigate the thermalization properties of photogenerated carriers by continuous-wave (cw) photoluminescence (PL) in InP and GaAs NWs. A quantitative analysis of the PL spectra recorded up to 310 K shows that carriers can thermalize at a temperature much higher than that of the lattice. We find that the mismatch between carrier and lattice temperature, ΔT, increases exponentially with lattice temperature and depends inversely on the NW diameter. ΔT is instead independent of other NW characteristics, such as crystal structure (wurtzite vs zincblende), chemical composition (InP vs GaAs), shape (tapered vs columnar NWs), and growth method (vapor-liquid-solid vs selective-area growth). Remarkably, carrier temperatures as high as 500 K are reached at the lattice temperature of 310 K in NWs with ∼70 nm diameter. While a population of nonequilibrium carriers, usually referred to as "hot carriers", is routinely generated by high-power laser pulses and detected by ultrafast spectroscopy, it is quite remarkable that it can be observed in cw PL measurements, when a steady-state population of carriers is established. Time-resolved PL measurements show that even in the thinnest NWs carriers have enough time (∼1 ns) after photoexcitation to interact with phonons and thus to release their excess energy. Nevertheless, the inability of carriers to reach a full thermal equilibrium with the lattice points to inhibited phonon emission primarily caused by the large surface-to-volume ratio of small diameter NWs. PMID:27104870

  7. The Performance of Advanced III-V Solar Cells

    NASA Technical Reports Server (NTRS)

    Mueller, Robert L.; Gaddy, Edward; Day, John H. (Technical Monitor)

    2002-01-01

    Test results show triple junction solar cells with efficiencies as high as 27% at 28C and 136.7 mw/sq cm. Triple junction cells also achieve up to 27.5% at -120 C and 5 mw/sq cm, conditions applicable to missions to Jupiter. Some triple junction cells show practically no degradation as a result of Low Intensity Low Temperature (LILT) effects, while others show some; this degradation can be overcome with minor changes to the cell design.

  8. Unidirectional III-V microdisk lasers heterogeneously integrated on SOI.

    PubMed

    Mechet, P; Verstuyft, S; de Vries, T; Spuesens, T; Regreny, P; Van Thourhout, D; Roelkens, G; Morthier, G

    2013-08-12

    We demonstrate unidirectional bistability in microdisk lasers electrically pumped and heterogeneously integrated on SOI. The lasers operate in continuous wave regime at room temperature and are single mode. Integrating a passive distributed Bragg reflector (DBR) on the waveguide to which the microdisk is coupled feeds laser emission back into the laser cavity. This introduces an extra unidirectional gain and results in unidirectional emission of the laser, as demonstrated in simulations as well as in experiment. PMID:23938850

  9. Characterization of Hydrogen Complex Formation in III-V Semiconductors

    SciTech Connect

    Williams, Michael D

    2006-09-28

    Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

  10. Carbon films grown from plasma on III-V semiconductors

    NASA Technical Reports Server (NTRS)

    Pouch, J. J.; Warner, J. D.; Liu, D. C.

    1985-01-01

    Dielectric carbon films were grown on n- and p-type GaAs and InP substrates using plasmas generated at 30 KHz from gaseous hydrocarbons. The effect of gas source, flow rate, and power on film growth were investigated. Methane and n-butane gases were utilized. The flow rate and power ranged from 30 to 50 sccm and 25 to 300 W, respectively. AES measurements show only carbon to be present in the films. The relative Ar ion sputtering rate (3 KeV) of carbon depends on the ratio power/pressure. In addition, the degree of asymmetry associated with the carbon-semiconductor interface is approximately power-independent. SIMS spectra indicate different H-C bonding configurations to be present in the films. Band gaps as high as 3.05 eV are obtained from optical absorption studies.

  11. [Update of breast cancer in Primary Care (III/V)].

    PubMed

    Álvarez Hernández, C; Vich Pérez, P; Brusint, B; Cuadrado Rouco, C; Díaz García, N; Robles Díaz, L

    2014-01-01

    Breast cancer is a prevalent disease with implications in all aspects of patientś life, therefore, family doctors must know this pathology in depth, in order to optimize the health care provided to these patients with the best available resources. This series of five articles on breast cancer is based on a review of the scientific literature of the last ten years. This third article will review the clinical context and the staging and prognostic factors of the disease. This summary report aims to provide a global, current and practical review about this problem, providing answers to family doctors and helping them to be by the patients for their benefit throughout their illness. PMID:24953699

  12. Asiago eclipsing binaries program. III. V570 Persei

    NASA Astrophysics Data System (ADS)

    Tomasella, L.; Munari, U.; Cassisi, S.; Siviero, A.; Dallaporta, S.; Sordo, R.; Zwitter, T.

    2008-05-01

    The orbit and physical parameters of the previously unsolved double-lined eclipsing binary V570 Per, discovered by the Hipparcos satellite, were derived using high-resolution Echelle spectroscopy and B, V photoelectric photometry. The metallicity from χ2 analysis of the spectra is [ M/H]=+0.02±0.03, and reddening from interstellar NaI and KI absorption lines is EB-V=0.023±0.007. V570 Per is a well-detached system, with shallow eclipses (due to low orbital inclination) and no sign of chromospheric activity. The two components have masses of 1.449±0.006 and 1.350±0.006~M_⊙ and spectral types F3 and F5, respectively. They are both still within the main sequence band (T_1=6842±25 K, T_2=6562± 25 K from χ2 analysis, R_1=1.523±0.030, R_2=1.388± 0.019 R_⊙ derived by forcing the orbital solution to conform to the spectroscopic light ratio) and are dynamically relaxed to co-rotation with the orbital motion (V_rot,1,2 sin i=40 and 36 (±1) km s-1). The distance to V570 Per obtained from the orbital solution is 123 ±2 pc, in excellent agreement with the revised Hipparcos distance of 123±11 pc. The observed properties of V570 Per components were compared to available families of stellar evolutionary tracks and, in particular, to BaSTI models computed on purpose for exactly the observed masses and varied chemical compositions. This system is interesting since both components have their masses in the range where the efficiency of convective core overshooting has to decrease with the total mass as a consequence of the decreasing size of the convective core during the central H-burning stage. Our numerical simulations show that, in order to match all empirical constraints, a small but not null overshooting is required, with efficiencies of λ_OV=0.14 and 0.11 for the 1.449 and 1.350 M_⊙ components, respectively. This confirms the finding of Paper II on the similar system V505 Per. At the ≈0.8 Gyr age of the system, the element diffusion has reduced the surface metallicity of the models from the initial [ M/H]=+0.17 to [ M/H]=+0.02, in perfect agreement with the spectroscopically derived [ M/H]=+0.02± 0.03 value. Based mainly on data obtained with Asiago 1.82 m telescope. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/483/263

  13. Vertical III-V nanowire device integration on Si(100).

    PubMed

    Borg, Mattias; Schmid, Heinz; Moselund, Kirsten E; Signorello, Giorgio; Gignac, Lynne; Bruley, John; Breslin, Chris; Das Kanungo, Pratyush; Werner, Peter; Riel, Heike

    2014-01-01

    We report complementary metal-oxide-semiconductor (CMOS)-compatible integration of compound semiconductors on Si substrates. InAs and GaAs nanowires are selectively grown in vertical SiO2 nanotube templates fabricated on Si substrates of varying crystallographic orientations, including nanocrystalline Si. The nanowires investigated are epitaxially grown, single-crystalline, free from threading dislocations, and with an orientation and dimension directly given by the shape of the template. GaAs nanowires exhibit stable photoluminescence at room temperature, with a higher measured intensity when still surrounded by the template. Si-InAs heterojunction nanowire tunnel diodes were fabricated on Si(100) and are electrically characterized. The results indicate a high uniformity and scalability in the fabrication process. PMID:24628529

  14. Surface Localization of Buried III-V Semiconductor Nanostructures.

    PubMed

    Alonso-González, P; González, L; Fuster, D; Martín-Sánchez, J; González, Yolanda

    2009-01-01

    In this work, we study the top surface localization of InAs quantum dots once capped by a GaAs layer grown by molecular beam epitaxy. At the used growth conditions, the underneath nanostructures are revealed at the top surface as mounding features that match their density with independence of the cap layer thickness explored (from 25 to 100 nm). The correspondence between these mounds and the buried nanostructures is confirmed by posterior selective strain-driven formation of new nanostructures on top of them, when the distance between the buried and the superficial nanostructures is short enough (d = 25 nm). PMID:20596455

  15. Phonon Limited Performance of III-V Nanowire Transistors

    NASA Astrophysics Data System (ADS)

    Gilbert, M. J.; Ferry, D. K.

    2006-05-01

    We use a fully self-consistent three-dimensional quantum mechanical transport formalism to examine the performance of InAs based quantum wire transistors both in the ballistic limit and with phonon scattering included. We present a method for the inclusion of polar optical phonon scattering as a real-space self-energy term. We find that the ballistic performance of the devices can be recovered if the dopants in the system are kept away from the channel entrance and exit. When dopants are present at these key points, we find that the altered carrier energy, particularly in the source, has a significant impact on the device. This ballistic recovery is aided by the fact that at higher energies, polar optical phonon scattering loses its non-locality which leads to a reduced scattering rate in these confined systems.

  16. Large diameter III-V substrates current issues and perspective

    SciTech Connect

    Sawada, S.; Oida, K.; Miyajima, H.

    1995-12-31

    This paper presents prospects for the future market, availability and cost of 6-in.-diam. GaAs substrates from a substrate supplier`s point of view. Outlining the challenges to the substrate supplier, the authors discuss the current issues and the future potential of production technologies (crystal growth, annealing, and wafer processing) for 6-in.-diam. GaAs substrates, and mention current issues for 3-in.-diam. InP substrates. In addition, they introduce 6-in.-diam. GaAs and 3-in.-diam. InP crystals grown by the VCZ method, which is a promising technology for the production of large substrates for multimedia devices.

  17. III-V Solar Cells and Concentrator Arrays

    NASA Astrophysics Data System (ADS)

    Alferov, Z. I.; Andreev, V. M.; Rumyantsev, V. D.

    Semiconductor heterostructures allow us to solve the problems of controlling the fundamental parameters of the semiconductor devices. These heterostructures provide the ability to change the electronic band structure, band gaps and refractive indices of the material itself during epitaxial growth, as well as to control the effective masses and mobilities of the charge carriers in it. The development of the physics and technology of semiconductor heterostructures has resulted in remarkable changes in our everyday life. Heterostructure electronics is widely used in many areas. It is hardly possible to imagine our life without double heterostructure (DHS) laser-based telecommunication systems, heterostructure solar cells (HSSCs) and light-emitting diodes (LEDs), heterostructure bipolar transistors and low-noise, high-electron mobility transistors for high-frequency applications including, for example, satellite television. Now DHS lasers exist in practically every home in CD players. Heterostructure solar cells are widely used for space and terrestrial applications.

  18. ICP dry etching of III-V nitrides

    SciTech Connect

    Vartuli, C.B.; Lee, J.W.; MacKenzie, J.D.

    1997-10-01

    Inductively coupled plasma etching of GaN, AlN, InN, InGaN and InAlN was investigated in CH{sub 4}/H{sub 2}/Ar plasmas as a function of dc bias, and ICP power. The etch rates were generally quite low, as is common for III-nitrides in CH{sub 4} based chemistries. The etch rates increased with increasing dc bias. At low rf power (150 W), the etch rates increased with increasing ICP power, while at 350 W rf power, a peak was found between 500 and 750 W ICP power. The etched surfaces were found to be smooth, while selectivities of etch were {le} 6 for InN over GaN, AlN, InGaN and InAlN under all conditions.

  19. Comparison of plasma etch techniques for III V nitrides

    NASA Astrophysics Data System (ADS)

    Shul, R. J.; Vawter, G. A.; Willison, C. G.; Bridges, M. M.; Lee, J. W.; Pearton, S. J.; Abernathy, C. R.

    1998-12-01

    Fabrication of group-III nitride devices relies on the ability to pattern features to depths ranging from ˜1000 Å to >5 μm with anisotropic profiles, smooth morphologies, selective etching of one material over another and a low degree of plasma-induced damage. In this study, GaN etch rates and etch profiles are compared using reactive ion etch (RIE), reactive ion beam etching (RIBE), electron cyclotron resonance (ECR) and inductively coupled plasma (ICP) etch systems. RIE yielded the slowest etch rates and sloped etch profiles despite dc-biases >-900 V. ECR and ICP etching yielded the highest rates with anisotropic profiles due to their high plasma flux and the ability to control ion energies independently of plasma density. RIBE etch results also showed anisotropic profiles but with slower etch rates than either ECR or ICP possibly due to lower ion flux. InN and AlN etch characteristics are also compared using ICP and RIBE.

  20. Novel compound semiconductor devices based on III-V nitrides

    SciTech Connect

    Pearton, S.J.; Abernathy, C.R.; Ren, F.

    1995-10-01

    New developments in dry and wet etching, ohmic contacts and epitaxial growth of Ill-V nitrides are reported. These make possible devices such as microdisk laser structures and GaAs/AlGaAs heterojunction bipolar transistors with improved InN ohmic contacts.

  1. PLUTONIUM-URANIUM-TITANIUM ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-07-28

    A plutonium-uranium alloy suitable for use as the fuel element in a fast breeder reactor is described. The alloy contains from 15 to 60 at.% titanium with the remainder uranium and plutonium in a specific ratio, thereby limiting the undesirable zeta phase and rendering the alloy relatively resistant to corrosion and giving it the essential characteristic of good mechanical workability.

  2. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  3. De-alloyed platinum nanoparticles

    DOEpatents

    Strasser, Peter; Koh, Shirlaine; Mani, Prasanna; Ratndeep, Srivastava

    2011-08-09

    A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

  4. Hydrogen in titanium alloys

    SciTech Connect

    Wille, G W; Davis, J W

    1981-04-01

    The titanium alloys that offer properties worthy of consideration for fusion reactors are Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-Si (Ti-6242S) and Ti-5Al-6Sn-2Zr-1Mo-Si (Ti-5621S). The Ti-6242S and Ti-5621S are being considered because of their high creep resistance at elevated temperatures of 500/sup 0/C. Also, irradiation tests on these alloys have shown irradiation creep properties comparable to 20% cold worked 316 stainless steel. These alloys would be susceptible to slow strain rate embrittlement if sufficient hydrogen concentrations are obtained. Concentrations greater than 250 to 500 wppm hydrogen and temperatures lower than 100 to 150/sup 0/C are approximate threshold conditions for detrimental effects on tensile properties. Indications are that at the elevated temperature - low hydrogen pressure conditions of the reactors, there would be negligible hydrogen embrittlement.

  5. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  6. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  7. Alloyed coatings for dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Wermuth, F. R.; Stetson, A. R.

    1971-01-01

    Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

  8. Lasing in direct-bandgap GeSn alloy grown on Si

    NASA Astrophysics Data System (ADS)

    Wirths, S.; Geiger, R.; von den Driesch, N.; Mussler, G.; Stoica, T.; Mantl, S.; Ikonic, Z.; Luysberg, M.; Chiussi, S.; Hartmann, J. M.; Sigg, H.; Faist, J.; Buca, D.; Grützmacher, D.

    2015-02-01

    Large-scale optoelectronics integration is limited by the inability of Si to emit light efficiently, because Si and the chemically well-matched Ge are indirect-bandgap semiconductors. To overcome this drawback, several routes have been pursued, such as the all-optical Si Raman laser and the heterogeneous integration of direct-bandgap III-V lasers on Si. Here, we report lasing in a direct-bandgap group IV system created by alloying Ge with Sn without mechanically introducing strain. Strong enhancement of photoluminescence emerging from the direct transition with decreasing temperature is the signature of a fundamental direct-bandgap semiconductor. For T ≤ 90 K, the observation of a threshold in emitted intensity with increasing incident optical power, together with strong linewidth narrowing and a consistent longitudinal cavity mode pattern, highlight unambiguous laser action. Direct-bandgap group IV materials may thus represent a pathway towards the monolithic integration of Si-photonic circuitry and complementary metal-oxide-semiconductor (CMOS) technology.

  9. Quinary metallic glass alloys

    DOEpatents

    Lin, Xianghong; Johnson, William L.

    1998-01-01

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  10. Quinary metallic glass alloys

    DOEpatents

    Lin, X.; Johnson, W.L.

    1998-04-07

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  11. Annealing strained alloy 718

    NASA Technical Reports Server (NTRS)

    Morrison, T. J.

    1976-01-01

    Report shows that grain coarsening in Alloy 718 can result in greatly reduced resistance to weld-heat-produced zone fissuring, especially when final grain size is ASTM 2. Tensile tests and metallographic examination of bend test specimens provide necessary data.

  12. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2002-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  13. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2000-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  14. Superplasticity in aluminum alloys

    SciTech Connect

    Nieh, T. G.

    1997-12-01

    We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. As a result, the alloy retains its fine grain size (about 7 micron), even after extensive superplastic deformation (>1000%). During deformation, dislocations Mg with a high Schmidt factor slip across subgrains but are trapped by subgrain boundaries, as a result of the strong pining of Al3Sc. This process leads to the conversion of low-angled subgrain boundaries to high-angled grain boundaries and the subsequent grain boundary sliding, which produces superelasticity. A model is proposed to describe grain boundary sliding accommodated by dislocation glide across grains with a uniform distribution of coherent precipitates. The model predictions is consistent with experimental observations.

  15. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, M.L.; Sikka, V.K.

    1998-03-10

    A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

  16. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1998-01-01

    A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

  17. TERNARY ALLOY-CONTAINING PLUTONIUM

    DOEpatents

    Waber, J.T.

    1960-02-23

    Ternary alloys of uranium and plutonium containing as the third element either molybdenum or zirconium are reported. Such alloys are particularly useful as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% of molybdenum or zirconium, the balance being a combination of uranium and plutonium in the ratio of from 1 to 9 atoms of uranlum for each atom of plutonium. These alloys are prepared by melting the constituent elements, treating them at an elevated temperature for homogenization, and cooling them to room temperature, the rate of cooling varying with the oomposition and the desired phase structure. The preferred embodiment contains 12 to 25 at.% of molybdenum and is treated by quenching to obtain a body centered cubic crystal structure. The most important advantage of these alloys over prior binary alloys of both plutonium and uranium is the lack of cracking during casting and their ready machinability.

  18. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  19. Alloys for crown and bridgework.

    PubMed

    Brockhurst, P J; Cannon, R W

    1981-10-01

    The requirements of alloys for metal-ceramic crowns and bridgework are examined. The functional requirements and manipulative behaviour and cost of cheaper alternatives to high gold alloys are discussed. All types use--high gold, reduced gold, silver palladium and base metal--appear to function satisfactorily in the mouth. Nickel and beryllium do not appear to be health hazards. Dental laboratory procedures and materials must be chosen to suit the type of alloy employed, although all alloy types appear suitable for crown and bridgework. The cost of alloy must be carefully examined in the context of total cost to the patient, and the use of alternatives to gold alloys in many cases may not warrant the required changes to laboratory procedures, but the saving is real, and can make permanent restorations available to greater proportion of the community. PMID:7036968

  20. Magnesium-lithium casting alloys

    NASA Technical Reports Server (NTRS)

    Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.

    1974-01-01

    The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.

  1. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  2. Duct and cladding alloy

    SciTech Connect

    Korenko, M.K.

    1983-03-22

    An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700/sup 0/ C consists essentially of 35-45% nick 5-14% chromi 8-3.2% molybden 3-1.0% silic 2-1.0% mangane 0-0.1% zirconiu 0-3.5% titani 0-2.0% alumin 02-0.1% car 0-0.01% boro and the balance iron.

  3. Shape memory alloy actuator

    DOEpatents

    Varma, Venugopal K.

    2001-01-01

    An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

  4. Duct and cladding alloy

    DOEpatents

    Korenko, Michael K.

    1983-01-01

    An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700.degree. C. consists essentially of 35-45% nickel 7.5-14% chromium 0.8-3.2% molybdenum 0.3-1.0% silicon 0.2-1.0% manganese 0-0.1% zirconium 2.0-3.5% titanium 1.0-2.0% aluminum 0.02-0.1% carbon 0-0.01% boron and the balance iron.

  5. Materials data handbook, Inconel alloy 718

    NASA Technical Reports Server (NTRS)

    Sessler, J.; Weiss, V.

    1967-01-01

    Materials data handbook on Inconel alloy 718 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

  6. Materials data handbook, aluminum alloy 7075

    NASA Technical Reports Server (NTRS)

    Sessler, J.; Weiss, V.

    1967-01-01

    Materials data handbook on aluminum alloy 7075 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures, and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

  7. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong; Merz, Martin D.

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  8. Amorphous metal alloy and composite

    SciTech Connect

    Wang, R.; Merz, M.D.

    1985-01-29

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  9. Surface Segregation in Ternary Alloys

    NASA Technical Reports Server (NTRS)

    Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.

  10. Titanium-tantalum alloy development

    SciTech Connect

    Cotton, J.D.; Bingert, J.F.; Dunn, P.S.; Butt, D.P.; Margevicius, R.W.

    1996-04-01

    Research has been underway at Los Alamos National Laboratory for several years to develop an alloy capable of containing toxic materials in the event of a fire involving a nuclear weapon. Due to their high melting point, good oxidation resistance, and low solubility in molten plutonium, alloys based on the Ti-Ta binary system have been developed for this purpose. The course of the alloy development to-date, along with processing and property data, are presented in this overview.

  11. Lead alloys past present future

    SciTech Connect

    Bagshaw, N.E.

    1995-03-01

    The most critical non-active component in the lead acid battery is the grid of substrate. A review of the work on and grid alloys in the period 1960-1993 has been carried out by by the Advanced Lead-Acid Consortium, (ALABC), and, in this paper, the results are analyzed in relation to the effort expended in different alloy systems. Lead-antimony alloys and the effects on them of additions of arsenic, tin, and grain-refining elements (selenium, sulfur, copper), together with lead-calcium alloys and the effect on them of tin additions have received the greatest attention in the past.

  12. Better Alloys with Quantum Design

    NASA Astrophysics Data System (ADS)

    Jones, Travis E.; Eberhart, Mark E.; Imlay, Scott; Mackey, Craig; Olson, Greg B.

    2012-09-01

    Alloy discovery and development is slowed by trial and error methods used to identify beneficial alloying elements. This fact has led to suggestions that integrating quantum theory and modeling with traditional experimental approaches might accelerate the pace of alloy discovery. We report here on one such effort, using advances in first principles computation along with an evolving theory that allows for the partitioning of charge density into chemically meaningful structures, alloying elements that improve the adhesive properties of interfaces common to high strength steels have been identified.

  13. Fluoride technology of obtaining REM magnetic alloys and master alloys

    NASA Astrophysics Data System (ADS)

    Sophronov, V. L.; Zhiganov, A. N.; Makaseev, Yu N.; Rusakov, I. Yu; Verkhoturova, V. V.

    2016-02-01

    Rare earth permanent magnets (REPM) based on neodymium-Fe-boron system are the most promising, since they have the highest magnetic and satisfactory mechanical characteristics. The paper covers physical-chemical principles and shows the results of experimental studies of the process of obtaining REM alloys and master alloys using fundamentally new fluoride technology based on ladle calciothermal REM fluorides and Fe reduction.

  14. Cladding of Mg alloy with Zr based BMG Alloy

    NASA Astrophysics Data System (ADS)

    Prasada Rao, A. K.; Oh, Y. S.; Faisal, M. K.; Kim, N. J.

    2016-02-01

    In the present work, an attempt has been made to clad AZ31 magnesium alloy with Zr-based bulk metallic glassy alloy (Vit-1), by casting method. The interface studies conducted using SEM-EDS line scan indicate that a good bond is formed at the clad interface of Zr and Mg. And the mechanism involved is discussed herein.

  15. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, Mohsen; Martinez, David R.

    1998-01-01

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.

  16. PLUTONIUM-CERIUM-COPPER ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-05-12

    A low melting point plutonium alloy useful as fuel is a homogeneous liquid metal fueled nuclear reactor is described. Vessels of tungsten or tantalum are useful to contain the alloy which consists essentially of from 10 to 30 atomic per cent copper and the balance plutonium and cerium. with the plutontum not in excess of 50 atomic per cent.

  17. Palladium alloys for biomedical devices.

    PubMed

    Wataha, John C; Shor, Kavita

    2010-07-01

    In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine. PMID:20583886

  18. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.; Gueceri, S. I.; Farkas, D.; Labdon, M. B.; Nagaswami, N.; Pregger, B.

    1981-01-01

    The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.

  19. Equivalent crystal theory of alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1991-01-01

    Equivalent Crystal Theory (ECT) is a new, semi-empirical approach to calculating the energetics of a solid with defects. The theory has successfully reproduced surface energies in metals and semiconductors. The theory of binary alloys to date, both with first-principles and semi-empirical models, has not been very successful in predicting the energetics of alloys. This procedure is used to predict the heats of formation, cohesive energy, and lattice parameter of binary alloys of Cu, Ni, Al, Ag, Au, Pd, and Pt as functions of composition. The procedure accurately reproduces the heats of formation versus composition curves for a variety of binary alloys. The results are then compared with other approaches such as the embedded atom and lattice parameters of alloys from pure metal properties more accurately than Vegard's law is presented.

  20. Wedlable nickel aluminide alloy

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    2002-11-19

    A Ni.sub.3 Al alloy with improved weldability is described. It contains about 6-12 wt % Al, about 6-12 wt % Cr, about 0-3 wt % Mo, about 1.5-6 wt % Zr, about 0-0.02 wt % B and at least one of about 0-0.15 wt % C, about 0-0.20 wt % Si, about 0-0.01 wt % S and about 0-0.30 wt % Fe with the balance being Ni.

  1. Thermomechanical treatment of alloys

    DOEpatents

    Bates, John F.; Brager, Howard R.; Paxton, Michael M.

    1983-01-01

    An article of an alloy of AISI 316 stainless steel is reduced in size to predetermined dimensions by cold working in repeated steps. Before the last reduction step the article is annealed by heating within a temperature range, specifically between 1010.degree. C. and 1038.degree. C. for a time interval between 90 and 60 seconds depending on the actual temperature. By this treatment the swelling under neutron bombardment by epithermal neutrons is reduced while substantial recrystallization does not occur in actual use for a time interval of at least of the order of 5000 hours.

  2. New magnetic alloys

    SciTech Connect

    Chin, G.Y.

    1980-05-23

    Three notable new developments in magnetic alloys are highlighted. These include rare earth-cobalt permanent magnets with maximum energy products up to 240 kilojoules per cubic meter; chromium-cobalt-iron permanent magnets that have magnetic properties similar to those of the Alnicos, but contain only about half as much cobalt and are sufficiently ductile to be cold-formable; and high-induction grain-oriented silicon steels that exhibit 20 percent less core loss as transformer core materials than conventional oriented grades.

  3. Stress Corrosion Cracking of Certain Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Hasse, K. R.; Dorward, R. C.

    1983-01-01

    SC resistance of new high-strength alloys tested. Research report describes progress in continuing investigation of stress corrosion (SC) cracking of some aluminum alloys. Objective of program is comparing SC behavior of newer high-strength alloys with established SC-resistant alloy.

  4. Stable palladium alloys for diffusion of hydrogen

    NASA Technical Reports Server (NTRS)

    Patapoff, M.

    1973-01-01

    Literature search on hydrogen absorption effect on palladium alloys revealed existence of alloy compositions in which alpha--beta transition does not take place. Survey conclusions: 40 percent gold alloy of palladium should be used in place of palladium; alloy must be free of interstitial impurities; and metallic surfaces of tube must be clean.

  5. Interaction Of Hydrogen With Metal Alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Montano, J. W.

    1993-01-01

    Report describes experiments on interaction of hydrogen with number of metal alloys. Discusses relationship between metallurgical and crystallographic aspects of structures of alloys and observed distributions of hydrogen on charging. Also discusses effect of formation of hydrides on resistances of alloys to hydrogen. Describes attempt to correlate structures and compositions of alloys with their abilities to resist embrittlement by hydrogen.

  6. The entropy of alloys.

    SciTech Connect

    Stan, M.

    2004-01-01

    A major problem in simulating thermodynamic properties of alloys is modeling the entropy. While configurational entropy is incorporated in most stability calculations, the other components, such as the vibrational and electronic entropy are often neglected or roughly estimated. In this work we propose a method of accounting for both configurational and vibrational entropy and discuss the electronic contribution for several actinide based alloys. The meaning of entropy in non-equilibrium thermodynamic processes is also discussed and illustrated for the case of phase transformations and diffusion. The influence of temperature on the enthalpy and free energy of delta-Pu-Ga phase, as resulted from Modified Embedded Atom Method (MEAM), and the influence of Ga content on the enthalpy and free energy of delta-Pu-Ga phase are discussed. The analysis of the thermodynamic properties of the fcc Pu-Ga phase, as calculated with MEAM shows that the vibrational entropy contribution to the free energy is ve ry important and non-linear with temperature. The free energy also changes with the Ga content.

  7. High performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Winkelman, D. M.

    1989-01-01

    Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

  8. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800 C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800 C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700 C. at a low cost

  9. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800.degree. C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800.degree. C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700.degree. C. at a low cost

  10. Fatigue of die cast zinc alloys

    SciTech Connect

    Schrems, K.K.; Dogan, O.N.; Goodwin, F.E.

    2006-04-01

    The rotating bending fatigue limit of die cast zinc alloy 2, alloy 3, alloy 5, AcuZinc 5, and ZA-8 were determined as a part of an on-going program by ILZRO into the mechanical properties of die cast zinc. The stress-life (S-N) curves of alloys 3, 5, AcuZinc 5, and ZA-8 were determined previously. This presentation reports the results of the S-N curve for Alloy 2 and the calculated fatigue limits for all five alloys. During the previous stress-life testing, the samples were stopped at 10 million cycles and the fatigue limit for alloy 3, alloy 5, and AcuZinc 5 appeared to be higher and the fatigue limit for ZA-8 appeared to be lower than the values reported in the literature. This was further investigated in alloy 5 and ZA-8 by testing continuous cast bulk alloy 5 and ZA-8.

  11. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.

    1980-01-01

    The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.

  12. Modeling dissolution in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Durbin, Tracie Lee

    2005-07-01

    Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy. Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment. A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the "sharp-interface" method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum alloys when compared with published experimental results. The influence of inter-particle spacing is examined and shown to have a significant effect on dissolution kinetics. Finally, the impact of multiple particles of various sizes interacting in an aluminum matrix is investigated. It is shown that smaller particles dissolve faster, as expected, but influence the dissolution of larger particles through soft-impingement, even after the smaller particles have disappeared.

  13. Dissimilar friction welding of titanium alloys to alloy 718

    SciTech Connect

    Kuo, M.; Albright, C.E.; Baeslack, W.A. III

    1994-12-31

    The design of advanced, high-performance gas-turbine engines will require the utilization of elevated-temperature titanium-based materials, including conventional alloys, titanium aluminides, and titanium metal-matrix composites. The most efficient utilization of these materials in the engine compressor section would be achieved by directly joining these materials to existing nickel-base superalloys, such as Alloy 718. To date, the dissimilar welding of titanium alloys to nickel-based alloys has not been common practice because intermetallic compounds form in the weld and cause embrittlement. Special welding techniques must be developed to inhibit this compound formation and to provide high strength welds. In this investigation, a friction welding process was developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to nickel-based superalloy Alloy 718. An interlayer system comprised of copper and niobium sheet layers was employed as a diffusion barrier and weld deformation enhancer. A postweld heat treatment (PWHT, 700{degrees}C for 20 min in vacuum) under axial pressure (Ksi) was used to improve the joint strength consistency. The following conclusions can be drawn from this investigation: (1) A friction welding technique has been developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to Alloy 718 using an interlayer system of niobium and copper. Joint strengths averaging approximately 50 Ksi were achieved. (2) Deformation was concentrated in the interlayers, especially the copper interlayer, during friction welding. Increased reduction in length (RIL) during friction welding resulted in a decrease in the interlayer thicknesses. (3) The EDS results showed that the niobium and copper interlayers prevent interdiffusion between the two parent metals, producing formation of detrimental phases.

  14. Metallic alloy stability studies

    NASA Technical Reports Server (NTRS)

    Firth, G. C.

    1983-01-01

    The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

  15. Nonergodicity in binary alloys

    NASA Astrophysics Data System (ADS)

    Son, Leonid; Sidorov, Valery; Popel, Pjotr; Shulgin, Dmitry

    2015-09-01

    For binary liquids with limited miscibility of the components, we provide the corrections to the equation of state which arise from the nonergogic diffusivity. It is shown that these corrections result in lowering of critical miscibility point. In some cases, it may result in a bifurcation of miscibility curve: the mixtures near 50% concentration which are homogeneous at the microscopic level, occur to be too stable to provide a quasi - eutectic triple point. These features provide a new look on the phase diagrams of some binary systems. In present work, we discuss Ga-Pb, Fe-Cu, and Cu-Zr alloys. Our investigation corresponds their complex behavior in liquid state to the shapes of their phase diagrams.

  16. High strength ferritic alloy

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.

  17. Manufacturing of High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Licavoli, Joseph J.; Gao, Michael C.; Hawk, Jeffrey A.

    2015-07-01

    High entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion they have high configurational entropy, and thus they hold the promise of interesting and useful properties such as enhanced strength and phase stability. The present study investigates the microstructure of two single-phase face-centered cubic (FCC) HEAs, CoCrFeNi and CoCrFeNiMn, with special attention given to melting, homogenization and thermo-mechanical processing. Large-scale ingots were made by vacuum induction melting to avoid the extrinsic factors inherent in small-scale laboratory button samples. A computationally based homogenization heat treatment was applied to both alloys in order to eliminate segregation due to normal ingot solidification. The alloys fabricated well, with typical thermo-mechanical processing parameters being employed.

  18. Tritium Production from Palladium Alloys

    SciTech Connect

    Claytor, T.N.; Schwab, M.J.; Thoma, D.J.; Teter, D.F.; Tuggle, D.G.

    1998-04-19

    A number of palladium alloys have been loaded with deuterium or hydrogen under low energy bombardment in a system that allows the continuous measurement of tritium. Long run times (up to 200 h) result in an integration of the tritium and this, coupled with the high intrinsic sensitivity of the system ({approximately}0.1 nCi/l), enables the significance of the tritium measurement to be many sigma (>10). We will show the difference in tritium generation rates between batches of palladium alloys (Rh, Co, Cu, Cr, Ni, Be, B, Li, Hf, Hg and Fe) of various concentrations to illustrate that tritium generation rate is dependent on alloy type as well as within a specific alloy, dependent on concentration.

  19. Microfissuring in Alloys During Welding

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Evaluating cause of intergranular cracking (microfissuring) in high-temperature alloys during welding done by measuring number of microcracks as function of temperature and plastic strain. Two mechanisms of microfissuring in heat-affected zones suggested.

  20. Superplastic forming of alloy 718

    SciTech Connect

    Smith, G.D.; Flower, H.L. )

    1994-04-01

    Inconel Alloy 718 (UNS N07718) is now available in a fine-grained, controlled composition modification that can be super-plastically formed. The new superplastic forming (SPF) capability allows the manufacture of large, complex, and detailed parts, which improves integrity by reducing the need for joining. Furthermore, it allows designers to fabricate components having higher strength, fatigue resistance, and temperature capability than parts made of aluminum or titanium alloys.

  1. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, M.; Martinez, D.R.

    1998-04-07

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states. 16 figs.

  2. Castable hot corrosion resistant alloy

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A. (Inventor); Holt, William H. (Inventor)

    1988-01-01

    Some 10 wt percent nickel is added to an Fe-base alloy which has a ferrite microstructure to improve the high temperature castability and crack resistance while about 0.2 wt percent zirconium is added for improved high temperatur cyclic oxidation and corrosion resistance. The basic material is a high temperature FeCrAl heater alloy, and the addition provides a material suitable for burner rig nozzles.

  3. Casting Characteristics of Aluminum Die Casting Alloys

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

    The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.

  4. Overview of ODS Alloy Development

    SciTech Connect

    Wright, Ian G; Pint, Bruce A

    2005-01-01

    The overall goal of this effort is to address the materials-related barriers to expediting the use of oxide dispersion-strengthened (ODS) alloys in components required in the U.S. Department of Energy's (DOE's) Office of Fossil Energy's advanced coal combustion, gasification, and utilization processes to operate at temperatures higher than are possible with conventionally-strengthened alloys. The project is focused on the needs of the broad range of ferritic ODS-alloys, especially the FeCrAl-based alloys, with the purpose of developing a detailed understanding of the behavior of ODS alloys in all phases of their use, including fabrication, service performance, life prediction, mode of failure, repair, and refurbishment. The intended output of this project is a compilation of information that facilitates the assessment of the applicability of ODS alloys to the needs of high-temperature equipment required in DOE's advanced power plants. Particular emphasis has been placed on processing modifications to increase the hoop strength of ODS tubes, on joining, and on oxidation-limited life prediction. Approaches for modifying the alloy grain structure to increase the creep strength in the transverse/hoop direction (for tubes) have involved the examination of processes that modify the secondary recrystallization behavior of the alloy, with the intention of producing larger, more equiaxed grains, or a spiral grain structure that reduces the number of transverse grain boundaries. Processing using a commercial-scale pilgering/flow-forming/cross-rolling facility indicated the potential of this route, but also revealed some practical difficulties, especially since such processing of ODS alloys must be done at temperatures above approximately 600 C. Research to provide guidance for such processing has involved measurements using well-controlled, hot torsion testing, as well as trials with a small-scale cross-rolling mill. Progress has been made with joining approaches that involve inertia welding, and diffusion bonding, and the creep strength of butt joints made by some of the process variations approaches the transverse creep strength of the parent alloy. A particular feature of the ferritic ODS-FeCrAl alloys is that they exhibit relatively low oxidation rates up to 1200 C (2192 F), due to the formation of a protective Al2O3 film. In service, the mechanical load applied to these ODS alloys will be below the stress level at which significant creep occurs, so that it is likely that the effective service lifetime will be determined by the rate of environmental degradation. Operation at the very high temperatures possible with these alloys means that, should the ability to form a protective oxide scale be lost, the ensuing oxidation damage could be very rapid. However, since during protective oxidation there is very little loss in alloy section due to the thin alumina scales formed, it is doubtful that mechanical means for monitoring the rate consumption of the alloy would provide sufficient accuracy for assessment of remaining lifetime. Hence, there is a need for some form of lifetime model to provide reliable prediction of remaining lifetime in typical service environments. Efforts to develop a lifetime model are in progress for the condition where the life-limiting process is oxidation in air (or oxygen); some data also have been generated in reducing environments (where there is potential for sulfidation attack); and in steam. Comparison of predictions from the model with results from lifetime testing in air indicate that good progress is being made.

  5. Choosing An Alloy For Automotive Stirling Engines

    NASA Technical Reports Server (NTRS)

    Stephens, Joseph R.

    1988-01-01

    Report describes study of chemical compositions and microstructures of alloys for automotive Stirling engines. Engines offer advantages of high efficiency, low pollution, low noise, and ability to use variety of fuels. Twenty alloys evaluated for resistance to corrosion permeation by hydrogen, and high temperature. Iron-based alloys considered primary candidates because of low cost. Nickel-based alloys second choice in case suitable iron-based alloy could not be found. Cobalt-based alloy included for comparison but not candidate, because it is expensive strategic material.

  6. Ab-initio DFT FP-LAPW GGA and LDA TB-mBJ and SO theoretical study of structural and elastic properties of Zinc-Blende crystal phase GaAs1-xBix alloys

    NASA Astrophysics Data System (ADS)

    Menezla, S.; Kadri, A.; Zitouni, K.; Djelal, A.; Djermouni, M.; Hallouche, A.; Zaoui, A.

    2015-12-01

    We present an ab-initio theoretical study of structural and elastic properties of GaAs1-xBix alloys in the Zinc-Blende (ZB) phase. We use a recent version of Wien2k package code based on Density Functional Theory (DFT) Full Potential and Linearized Augmented Plane Waves (FP-LAPW) method including recent Tran-Blaha modified Becke-Johnson correction of the exchange potential (TB-mBJ) and the spin-orbit interaction (SO). The calculations are performed within the Local Density Approximation (LDA) as well as the Generalized Gradient Approximation (GGA). We study first the structural properties of GaAs1-xBix alloys by solving Murnaghan equation of state. Our results show that the ZB phase is the lowest equilibrium crystal structure of GaAs1-xBix in the whole alloy composition range, in agreement with previous theoretical predictions. The variations versus Bi contents of the ZB GaAs1-xBix lattice constant a0, bulk modulus B0 and its pressure derivative B0‧ are also found very close to other theoretical and experimental data, but with much smaller bowing effects indicating a better resolution thanks to TB-mBJ correction. The variations of B0 versus the reverse equilibrium volume of the unit cell (1/V0) are found to be described by the simple linear empirical expression B0 = -0.21068 + 0.16695/V0 which is close to the theoretical prediction for III-V semiconductors with, however, somewhat lower linear coefficients values, suggesting a more metallic behavior. In a second part of this work, we use Birch-Murnaghan approach to study the elastic properties of GaAs1-xBix alloys. The elastic stiffness coefficients, C11, C12 and C44, and their variations versus alloy composition were determined for ZB GaAs1-xBix alloy. Their values in GaAs and GaBi binary compounds are found in very good agreement with available experimental and/or theoretical data. Their variations in GaAs1-xBix alloy show a monotonic decrease with increasing Bi contents, indicating a softening behavior as is typically the case for metallic alloys. The values of the bulk modulus derived with the help of C11, C12 and C44 elastic stiffness coefficients are found very close to B0 values derived directly from Murnaghan equation of state, indicating the good accuracy of Cij coefficients deduced from Birch-Murnaghan procedure.

  7. Alloy 602 CA -- A new alloy for the furnace industry

    SciTech Connect

    Brill, U.; Agarwal, D.C.

    1995-12-31

    Improving the economics of heat treatment facilities is often a question of raising the service temperature, which itself rests on the temperature capability of the alloys used. With the newly-developed alloy 602CA introduced to the market in 1992, there is now a nickel-base alloy available which provides sufficient high temperature strength and corrosion resistance up to 1,200 C, without any, special requirements on manufacturing and processing. Because of the excellent mechanical properties and corrosion resistance of this alloy it was possible to substitute uncooled all-metal furnace rolls for water-cooled asbestos rolls, in a continuous annealing furnace operating at up to 1,200 C. These rolls have now been in service for up to two years without any technical problems, and have proved themselves as a more economic and less environmentally dangerous, solution, This paper describes the mechanical properties and corrosion behavior of the new alloy, and gives some calculations on economic efficiency.

  8. Kinetics of aluminum lithium alloys

    NASA Astrophysics Data System (ADS)

    Pletcher, Ben A.

    2009-12-01

    Aluminum lithium alloys are increasingly used in aerospace for their high strength-to-weight ratio. Additions of lithium, up to 4.2 wt% decrease the alloy density while increasing the modulus and yield strength. The metastable, second phase Al3Li or delta' is intriguing, as it remains spherical and coherent with the matrix phase, alpha, well into the overaged condition. Small interfacial strain energy allows these precipitates to remain spherical for volume fractions (VV ) of delta' less than 0.3, making this alloy system ideal for investigation of late-stage coarsening phenomena. Experimental characterization of three binary Al-Li alloys are presented as a critical test of diffusion screening theory and multi-particle diffusion simulations. Quantitative transmission electron microscopy is used to image the precipitates directly using the centered dark-field technique. Images are analyzed autonomously within a novel Matlab function that determines the center and size of each precipitate. Particle size distribution, particle growth kinetics, and maximum particle size are used to track the precipitate growth and correlate with the predictions of screening theory and multi-particle diffusion simulations. This project is the first extensive study of Al-Li alloys, in over 25 years, applying modern transmission electron microscopy and image analysis techniques. Previous studies sampled but a single alloy composition, and measured far fewer precipitates. This study investigates 3 alloys with volume fractions of the delta precipitates, VV =0.1-0.27, aged at 225C for 1 to 10 days. More than 1000 precipitates were sampled per aging time, creating more statistically significant data. Experimental results are used to test the predictions based on diffusion screening theory and multi-particle aging simulations. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

  9. Shape memory alloys. Ultralow-fatigue shape memory alloy films.

    PubMed

    Chluba, Christoph; Ge, Wenwei; Lima de Miranda, Rodrigo; Strobel, Julian; Kienle, Lorenz; Quandt, Eckhard; Wuttig, Manfred

    2015-05-29

    Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle. PMID:26023135

  10. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

    Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

  11. Lightweight magnesium-lithium alloys show promise

    NASA Technical Reports Server (NTRS)

    Adams, W. T.; Cataldo, C. E.

    1964-01-01

    Evaluation tests show that magnesium-lithium alloys are lighter and more ductile than other magnesium alloys. They are being used for packaging, housings, containers, where light weight is more important than strength.

  12. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  13. Imprinting bulk amorphous alloy at room temperature.

    PubMed

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T; Lograsso, Thomas A; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  14. Quasicrystal-reinforced Mg alloys

    NASA Astrophysics Data System (ADS)

    Kim, Young Kyun; Kim, Won Tae; Hyang Kim, Do

    2014-04-01

    The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg-Zn-Y and Mg-Zn-Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α-Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg-Zn-Y alloys, the co-presence of I and Ca2Mg6Zn3 phases by addition of Ca can significantly enhance formability, while in Mg-Zn-Al alloys, the co-presence of the I-phase and Mg2Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg-Zn-Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg-Zn-Al-Sn alloys is attributed to the presence of finely distributed Mg2Sn and I-phase particles embedded in the α-Mg matrix.

  15. Oxidation of low cobalt alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1982-01-01

    Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

  16. Superconducting compounds and alloys research

    NASA Technical Reports Server (NTRS)

    Otto, G.

    1975-01-01

    Resistivity measurements as a function of temperature were performed on alloys of the binary material system In sub(1-x) Bi sub x for x varying between 0 and 1. It was found that for all single-phase alloys (the pure elements, alpha-In, and the three intermetallic compounds) at temperatures sufficiently above the Debye-temperature, the resistivity p can be expressed as p = a sub o T(n), where a sub o and n are composition-dependent constants. The same exponential relationship can also be applied for the sub-system In-In2Bi, when the two phases are in compositional equilibrium. Superconductivity measurements on single and two-phase alloys can be explained with respect to the phase diagram. There occur three superconducting phases (alpha-In, In2Bi, and In5Bi3) with different transition temperatures in the alloying system. The magnitude of the transition temperatures for the various intermetallic phases of In-Bi is such that the disappearance or occurrence of a phase in two component alloys can be demonstrated easily by means of superconductivity measurements.

  17. Fatigue behavior of titanium alloys

    SciTech Connect

    Boyer, R.R.; Eylon, D.; Luetjering, G.

    1999-07-01

    This symposium was international in nature, with leaders in the fields of fatigue technology and the metallurgy of titanium from the US, Europe and Asia. It covered basic research, development, applications and modeling--life predictions and design of both fatigue crack initiation and propagation of titanium alloys. There were presentations on the full range of titanium alloy systems, from commercially pure and {alpha}-alloys, {alpha}/{beta}- and {beta}-alloys to the gamma titanium aluminides. The effects of processing/heat treatment/microstructure on the fatigue properties were discussed, and models proposed to correlate the microstructures to the observed fatigue performance. Test environments reported on included hard vacuum (and the effect of vacuum level), vacuums with partial pressures of miscellaneous gases, lab air and aqueous media. A session was devoted to the effects of environment and fatigue enhancement via surface treatments using techniques such as shot peening and roller burnishing. The effects of dwell on both S-N and crack growth rate behavior were covered. It was a very comprehensive symposium with presentations from academia, government laboratories and industry, with industrial participants ranging from the petroleum industry to medical and aerospace interests. This book has been separated into four sections, representing the technology areas covered in various sessions, namely Mechanisms of Fatigue crack Initiation and Propagation of Conventional Alloys, Fatigue in Intermetallics, Environmental and Surface Aspects of Fatigue, and Application, Life Prediction and Design. Separate abstracts were prepared for most papers in this volume.

  18. Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

  19. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, Michael L.; Goodwin, Gene M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.

  20. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, M.L.; Goodwin, G.M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys. 5 figs.

  1. HEAT TREATED U-Nb ALLOYS

    DOEpatents

    McGeary, R.K.; Justusson, W.M.

    1959-11-24

    A fuel element for a nuclear reactor is described comprising an alloy containing uranium and from 7 to 20 wt.% niobium, the alloy being substantially in the gamma phase and having been produced by working an ingot of the alloy into the desired shape, homogenizing it by annealing it at a temperature in the gamma phase field, and quenching it to retain the gamma phase structure of the alloy.

  2. Welding high-strength aluminum alloys

    NASA Technical Reports Server (NTRS)

    Parks, P. G.; Hoppes, R. V.; Hasemeyer, E. A.; Masubuchi, K.

    1974-01-01

    Handbook has been published which integrates results of 19 research programs involving welding of high-strength aluminum alloys. Book introduces metallurgy and properties of aluminum alloys by discussing commercial alloys and heat treatments. Several current welding processes are reviewed such as gas tungsten-arc welding and gas metal-arc welding.

  3. Improved thermal treatment of aluminum alloy 7075

    NASA Technical Reports Server (NTRS)

    Cocks, F. H.

    1968-01-01

    Newly developed tempering treatment considerably increases the corrosion resistance of 7075-T6 alloy and concomitantly preserves its yield strength. The results of tests on samples of the alloy subjected to the above treatments show that when the overaging period is 12 hours /at 325 degrees F/, the alloy exhibits a yield strength of 73,000 psi.

  4. PREPARATION OF URANIUM-ALUMINUM ALLOYS

    DOEpatents

    Moore, R.H.

    1962-09-01

    A process is given for preparing uranium--aluminum alloys from a solution of uranium halide in an about equimolar molten alkali metal halide-- aluminum halide mixture and excess aluminum. The uranium halide is reduced and the uranium is alloyed with the excess aluminum. The alloy and salt are separated from each other. (AEC)

  5. Characterizing Semiconductor Alloys for Infrared Sensors

    NASA Technical Reports Server (NTRS)

    Lehoczky, B. S. L.; Szofran, F. R.; Martin, B. G.

    1986-01-01

    Report presents results of continuing program aimed at characterizing mercury/cadmium/tellurium alloys and eventually developing improved methods of preparing alloys for use as infrared sensors. Work covered by report includes series of differential thermal analysis (DTA) measurements of alloy compositions with x varied from 9 to 1 in 0.1 increments.

  6. ALLOY FOR USE IN NUCLEAR FISSION

    DOEpatents

    Spedding, F.A.; Wilhelm, H.A.

    1958-03-11

    This patent relates to an alloy composition capable of functioning as a solid homogeneous reactor fuel. The alloy consists of a beryllium moderator, together with at least 0.7% of U/sup 235/, and up to 50% thorium to give increased workability to the alloy.

  7. High strength uranium-tungsten alloy process

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1990-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  8. High strength uranium-tungsten alloys

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1991-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  9. Alloy Selection for High Temperature Heat Exchangers

    SciTech Connect

    Pint, Bruce A; Keiser, James R

    2006-01-01

    The long-term oxidation resistance of various commercial alloys is being evaluated for industrial heat exchangers intended to operate at 900-1100 C. At higher temperatures, many chromia-forming alloys have limited lifetime due to high rates of metal consumption and alumina-forming alloys are being considered.

  10. METHOD OF DISSOLVING REFRACTORY ALLOYS

    DOEpatents

    Helton, D.M.; Savolainen, J.K.

    1963-04-23

    This patent relates to the dissolution of alloys of uranium with zirconium, thorium, molybdenum, or niobium. The alloy is contacted with an anhydrous solution of mercuric chloride in a low-molecular-weight monohydric alcohol to produce a mercury-containing alcohol slurry. The slurry is then converted to an aqueous system by adding water and driving off the alcohol. The resulting aqueous slurry is electrolyzed in the presence of a mercury cathode to remove the mercury and produce a uranium-bearing aqueous solution. This process is useful for dissolving irradiated nuclear reactor fuels for radiochemical reprocessing by solvent extraction. In addition, zirconium-alloy cladding is selectively removed from uranium dioxide fuel compacts by this means. (AEC)

  11. Spin dynamics of complex oxides, bismuth-antimony alloys, and bismuth chalcogenides

    NASA Astrophysics Data System (ADS)

    Sahin, Cuneyt

    The emerging field of spintronics relies on the manipulation of electron spin in order to use it in spin-based electronics. Such a paradigm change has to tackle several challenges including finding materials with sufficiently long spin lifetimes and materials which are efficient in generating pure spin currents. This thesis predicts that two types of material families could be a solution to the aforementioned challenges: complex oxides and bismuth based materials. We derived a general approach for constructing an effective spin-orbit Hamiltonian which is applicable to all nonmagnetic materials. This formalism is useful for calculating spin-dependent properties near an arbitrary point in momentum space. We also verified this formalism through comparisons with other approaches for III-V semiconductors, and its general applicability is illustrated by deriving the spin-orbit interaction and predicting spin lifetimes for strained strontium titanate (STO) and a two-dimensional electron gas in STO (such as at the LAO/STO interface). Our results suggest robust spin coherence and spin transport properties in STO related materials even at room temperature. In the second part of the study we calculated intrinsic spin Hall conductivities for bismuth-antimony (BISb) semimetals with strong spin-orbit couplings, from the Kubo formula and using Berry curvatures evaluated throughout the Brillouin zone from a tight-binding Hamiltonian. Nearly crossing bands with strong spin-orbit interaction generate giant spin Hall conductivities in these materials, ranging from 474 ((h/e)O--1cm--1) for bismuth to 96((h/e)O--1cm --1) for antimony; the value for bismuth is more than twice that of platinum. The large spin Hall conductivities persist for alloy compositions corresponding to a three-dimensional topological insulator state, such as Bi0.83Sb0.17. The spin Hall conductivity could be changed by a factor of 5 for doped Bi, or for Bi0.83Sb0.17, by changing the chemical potential by 0.5 eV, suggesting the potential for doping or voltage tuned spin Hall current. We have also calculated intrinsic spin Hall conductivities of bismuth selenide and bismuth telluride topological insulators from an effective tight-binding Hamiltonian including two nearest-neighbor interactions. We showed that both materials exhibit giant spin Hall conductivities calculated from the Kubo formula in linear response theory and the clean static limit. We conclude that bismuth-antimony alloys and bismuth chalcogenides are primary candidates for efficiently generating spin currents through the spin Hall effect.

  12. Diffusion phase transitions in alloys

    NASA Astrophysics Data System (ADS)

    Ustinovshchikov, Yu I.

    2014-07-01

    We present a critical analysis of research on the thermodynamics, kinetics, and morphology of diffusion phase transitions in alloys. We show that diffusion phase transitions are mainly driven by the chemical potential difference due to a change in the sign of the chemical interaction among the component atoms. We explain how the sign of the chemical interaction energy can be obtained from experimental measurements. Examples are given to illustrate the kinetics and morphology of the ordering-separation phase transition in Ni- and Co-based alloys. We show how introducing the concept of the ordering-separation phase transition may affect our thinking in this area.

  13. Alloy 718 for Oilfield Applications

    NASA Astrophysics Data System (ADS)

    deBarbadillo, John J.; Mannan, Sarwan K.

    2012-02-01

    Alloy 718 (UNS N07718) was developed for use in aircraft gas turbine engines, but its unique combination of room-temperature strength and aqueous corrosion resistance made it a candidate for oilfield fasteners, valves, drill tools, and completion equipment. As well environments became more severe, stress corrosion and hydrogen embrittlement failures in production equipment drove the evolution of the composition and microstructure that distinguish today's oilfield-grade 718 from aerospace grades. This paper reviews the development of the grade and its applications and describes some of its unique characteristics, testing, and manufacturing methods as well as newer alloys designed for high-pressure high-temperature (HPHT) conditions.

  14. Method for calculating alloy energetics

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Smith, John R.

    1992-01-01

    A semiempirical method for the computation of alloy energies is introduced. It is based on the equivalent-crystal theory of defect-formation energies in elemental solids. The method is both simple and accurate. Heats of formation as a function of composition are computed for some binary alloys of Cu, Ni, Al, Ag, Pd, Pt, and Au using the heats of solution in the dilute limit as experimental input. The separation of heats into strain and chemical components helps in understanding the energetics. In addition, lattice-parameter contractions seen in solid solutions of Ag and Au are accurately predicted. Good agreement with experiment is obtained in all cases.

  15. PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

    DOEpatents

    Shor, R.S.; Vogler, S.

    1958-01-21

    A process is described for dissolving binary zirconium-uranium alloys where the uranium content is about 2%. In prior dissolution procedures for these alloys, an oxidizing agent was added to prevent the precipitation of uranium tetrafluoride. In the present method complete dissolution is accomplished without the use of the oxidizing agent by using only the stoichiometric amount or slight excess of HF required by the zirconium. The concentration of the acid may range from 2M to 10M and the dissolution is advatageously carried out at a temperature of 80 deg C.

  16. High strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  17. Imparting passivity to vapor deposited magnesium alloys

    NASA Astrophysics Data System (ADS)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning electron microscope. The corrosion rate of the nonequilibrium sputtered alloys, as determined by polarization resistance, is significantly reduced compared to the most corrosion resistant commercial magnesium alloys. The open circuit potentials of the sputter deposited alloys are significantly more noble compared to commercial, equilibrium phase magnesium alloys. Galvanic corrosion susceptibility has also been considerably reduced. Nonequilibrium magnesium-yttrium-titanium alloys have been shown to achieve passivity autonomously by alteration of the composition chemistry of the surface oxide/hydroxide layer. Self-healing properties are also evident, as corrosion propagation can be arrested after initial pitting of the material. A clear relationship exists between the corrosion resistance of sputter vapor deposited magnesium alloys and the amount of ion bombardment incurred by the alloy during deposition. Argon pressure, the distance between the source and the substrate, and alloy morphology play important roles in determining the ability of the alloy to develop a passive film. Thermal effects, both during and after alloy deposition, alter the stress state of the alloys, precipitation of second phases, and the mechanical stability of the passive film. An optimal thermal treatment has been developed in order to maximize the corrosion resistance of the magnesium-yttrium-titanium alloys. The significance of the results includes the acquisition of electrochemical data for these novel materials, as well as expanding the utilization of magnesium alloys by the improvement in their corrosion resistance. The magnesium alloys developed in this work are more corrosion resistant than any commercial magnesium alloy. Structural components comprised of these alloys would therefore exhibit unprecedented corrosion performance. Coatings of these alloys on magnesium components would provide a corrosion resistant yet galvanically-compatible coating. The broad impact of these contributions is that these new low-density, corrosion resistant magnesium alloys can be used to produce engineering components for vehicles that have greater acceleration, longer range, heavier payloads, lower life cycle costs, and longer inspection intervals.

  18. Stress corrosion of high strength aluminum alloys.

    NASA Technical Reports Server (NTRS)

    Cocks, F. H.; Brummer, S. B.

    1972-01-01

    An investigation has been carried out to examine the relationship of the observed chemical and mechanical properties of Al-Cu and Al-Zn-Mg alloys to the stress corrosion mechanisms which dominate in each case. Two high purity alloys and analogous commercial alloys were selected. Fundamental differences between the behavior of Al-Cu and of Al-Zn-Mg alloys were observed. These differences in the corrosion behavior of the two types of alloys are augmented by substantial differences in their mechanical behavior. The relative cleavage energy of the grain boundaries is of particular importance.

  19. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.

  20. Semiempirical Analysis of Surface Alloy Formation

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Ibanez-Meier, Rodrigo

    1995-01-01

    The BFS method for alloys is applied to the study of surface alloy formation. This method was previously used to examine the experimental STM observation of surface alloying of Au on Ni(110) for low Au coverages by means of a numerical simulation. In this work, we extend the study to include other cases of surface alloying for immiscible as well as miscible metals. All binary combinations of Ni, Au, Cu, and Al are considered and the simulation results are compared to experiment when data is available. The driving mechanisms of surface alloy formation are then discussed in terms of the BFS method and the available results.