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1

Spinodal decomposition and clustering in III\\/V alloys  

Microsoft Academic Search

The criteria for clustering and spinodal decomposition in III\\/V pseudobinary and quaternary solid alloys are examined. A chemical\\u000a driving force for clustering and phase separation exists in some ternary and most quaternary alloys. However, single crystalline\\u000a alloys are shown to be stabilized by the coherency strain energy inherent in any clustering or spinodal decomposition in alloys\\u000a where lattice parameter is

G. B. Stringfellow

1982-01-01

2

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

National Technical Information Service (NTIS)

A method for producing homogenous 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 floa...

T. F. Ciszek

1990-01-01

3

Band Gap Energy and Band Lineup of III-V Alloy Semiconductors Incorporating Nitrogen and Boron  

Microsoft Academic Search

The band gap energy and band lineup of 15 binary, 42 ternary and 39 quaternary III-V alloy semiconductors composed of (B, Al, Ga, In)(N, P, As, Sb) are calculated by mean of the dielectric method of Van Vechten and the Harrison model, respectively. The alloys including N are predicted to have negative band gap energy in most of the compositional

Shiro Sakai; Yoshihiro Ueta; Yoji Terauchi

1993-01-01

4

Elastic and Vibrational Properties of III-V Semiconductor Alloys  

NASA Astrophysics Data System (ADS)

Elastic and vibrational properties of the In_xGa_(1-x)As ternary alloy system are explored by ab initio electronic structure calculations on ordered model structures (e.g. Zincblende, Luzonite, Cu-Au). Elastic constants are evaluated from stress tensors ^1; phonon dispersion curves and phonon density of states are derived from the direct method ^2 based on the forces as calculated by the Vienna Ab-initio Simulation Package (VASP) ^3 employing the Projector Augmented Wave technique. The importance of local ordering on the cationic sublattice is assessed by comparison to interpolated results of binary compounds and experimental data. 1. Y. Le Page, P. Saxe, Phys. Rev. B 63, 174103 (2001) 2. K. Parlinski, Z. Q. Li, Y. Kawazoe, Phys. Rev. Lett. 48, 406 (1997) 3. G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996)

Geller, Clint B.; Wolf, Walter; Wimmer, Erich

2002-03-01

5

Calculation of energy band gaps in quaternary iii\\/v alloys  

Microsoft Academic Search

The dielectric theory of electronegativity is applied to the calculation of the compositional dependence of the energy band gap for quaternary III\\/V alloys of type Al-xBxC1-yDy and A1-x-yBxCyD. The departure from linearity of EG versus x and y is taken to be the sum of two terms, the intrinsic or virtual crystal term and the extrinsic term due to effects

G. B. Stringfellow

1981-01-01

6

Calculation of energy band gaps in quaternary iii\\/v alloys  

Microsoft Academic Search

The dielectric theory of electronegativity is applied to the calculation of the compositional dependence of the energy band\\u000a gap for quaternary III\\/V alloys of type Al-xBxC1-yDy and A1-x-yBxCyD. The departure from linearity of EG versus x and y is taken to be the sum of two terms, the intrinsic or virtual crystal term and the extrinsic term due to effects

G. B. Stringfellow

1981-01-01

7

Method for preparing homogeneous single crystal ternary III-V alloys  

DOEpatents

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.

Ciszek, Theodore F. (Evergreen, CO)

1991-01-01

8

New III-V Semiconductor InGaAsBi Alloy Grown by Molecular Beam Epitaxy  

NASA Astrophysics Data System (ADS)

A new Bi-containing III-V semiconductor InGaAsBi alloy was firstly grown by molecular beam epitaxy (MBE). The high crystalline quality of the InGaAsBi epilayer with smooth interfaces was confirmed by X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.

Feng, Gan; Yoshimoto, Masahiro; Oe, Kunishige; Chayahara, Akiyoshi; Horino, Yuji

2005-09-01

9

Atomistic modeling of bond lengths in random and ordered III-V alloys  

NASA Astrophysics Data System (ADS)

This work provides comprehensive modeling for the bond length and angle distributions in random and spontaneously ordered ternary III-V alloys using empirical interaction potentials. The compounds InxGa1-xAs, GaAs1-xSbx, and InxGa1-xP were used as model systems due to their technological importance and the fact that ordered structures were observed experimentally in these materials. For random alloys, we reproduce the bimodal bond length distribution, which allows linear fits with slopes between 0.087 A? and 0.1059 A? for all bond types. The calculated values for dilute compositions slightly deviate from these functions, causing stronger deformations. In the case of CuPt-ordered structures, the bond length distribution is shown to collapse to four sharp peaks with an area ratio of 1:3:3:1, which originate from a different atom to atom distance within the different (111) planes and perpendicular to these. An essential consequence of this atomic arrangement is the different spacings for the different stacked binaries along the (111) direction, which also leads to strain values up to -0.819% for In0.5Ga0.5P and -1.827% for GaAs0.5Sb0.5. Furthermore, the broad bond angle distributions of random alloys collapse into two peaks for CuPt-like structures. On the other hand, CuAu-type ordering is shown to lead to a sharp bimodal bond length distribution but with five different groups of bond angles, which can be identified with the different atomic configurations in ternary zincblende crystals.

Detz, H.; Strasser, G.

2013-09-01

10

Solid Phase Reactions of Ni-GaAs Alloys for High Mobility III—V MOSFET Applications  

NASA Astrophysics Data System (ADS)

The solid phase reactions of Ni with GaAs substrates are investigated. The experimental results reveal that the Ni-GaAs solid phase reaction forms a ternary phase of Ni2GaAs when annealing temperatures are in the range 250-300°C. As the annealing temperature increases to 400°C, the Ni2GaAs phase starts to decompose due to NiAs phase precipitation. Ni-GaAs alloys processed at 400°C with a 3 min annealing time demonstrate a sheet resistance of 30?/square after unreacted Ni removal in hot diluted-HCl solutions. Therefore, Ni-GaAs alloys formed by solid phase reaction could be promising metallic source/drain structures with significant low series resistance for high mobility III—V metal-oxide-semiconductor field effect transistor (MOSFET) applications.

Lu, Li; Chang, Hu-Dong; Sun, Bing; Wang, Hong; Xue, Bai-Qing; Zhao, Wei; Liu, Hong-Gang

2012-04-01

11

First principles and valence force field study of III-V quaternary alloys  

NASA Astrophysics Data System (ADS)

We report on the elastic properties and formation energies of GaxIn1-xPyN1-y quaternary alloys using first principles and valence force field (VFF) calculations. The elastic constants of the binary compounds (GaP, InP, GaN, and InN) were calculated using the local density approximation (LDA). The resulting VFF parameters, ? (bond stretching) and ? (bond angle bending) were used within the Keating model to calculate the formation energies of GaInP, GaInN, InPN, and GaPN ordered structures. We found that the VFF formation energies of phosphide-nitride alloys (e.g. GaPN) were not in very good agreement with the LDA formation energies. Conventionally, the bond bending parameter ? for a ternary alloy is chosen as the arithmetic mean of the binary constituents. To improve the accuracy of the VFF model, we lifted such restriction on the ?-parameter and we also introduced the parameter ? (bond length-bond angle interaction). The VFF parameters ?, ?, and ? were fitted to the LDA-calculated formation energies of a large number of ternary ordered structures and were used to calculate the formation energy of the GaxIn1-xPyN1-y quaternary alloy.

Biswas, Koushik; Franceschetti, Alberto; Lany, Stephan

2008-03-01

12

Synthesis and Optical Properties of Multiband III-V Semiconductor Alloys  

NASA Astrophysics Data System (ADS)

Quaternary GaNxAs1-yPy alloys have been synthesized using N ion implantation into GaAs1-yPy (y=0-0.4) epilayers followed by pulsed laser melting (II-PLM). We observed strong optical transitions from the valence band to both the lower (E-) and upper (E+) conduction subbands that arise from the N induced splitting of the conduction band (EM) of the GaAs1-yPy host. As predicted by the band anticrossing model, GaNxAs1-x-yPy with y>0.3 is a three band semiconductor alloy with potential applications for high-efficiency intermediate band solar cells.

Yu, K. M.; Walukiewicz, W.; Farshchi, R.; Dubon, O. D.; Ager, J. W.; Sharp, I. D.; Haller, E. E.

2007-04-01

13

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

SciTech Connect

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.

CA Wang

2004-05-06

14

Effects of gallium alloy content and the geometrical confinement on effective exciton g-factor in a III-V semiconductor quantum dot  

NASA Astrophysics Data System (ADS)

Effective exciton-g factor as functions of dot radius and Ga alloy content in a GaxIn1-xAs/GaAs quantum dot is computed. The computations are included with the effect of mass anisotropy and the non-parabolicity of the conduction band. The dependence of excitonic binding energy with respect to the dot radius is investigated for various composition of Ga alloy content.

Senthilkumar, N. R.; Peter, A. John

2013-02-01

15

Miscibility gaps and spinodal decomposition in III/V quaternary alloys of the type A/sub x/B/sub y/C/sub 1-x/-yD  

SciTech Connect

Thermodynamic concepts have been developed for the calculation of solid-phase miscibility gaps and spinodal decomposition in quaternary alloys of the type A/sub x/B/sub y/C/sub 1-x/-yD. These concepts have been applied to the analysis of III/V quaternary alloys using the delta-lattice-parameter (DLP) solution model. In addition, the effects of coherency strain energy have been included in the calculation. Results are presented for the systems Al/sub x/Ga/sub y/In/sub 1-x/-yP, Al/sub x/Ga/sub y/In/sub 1-x/-yAs, InP/sub x/As/sub y/Sb/sub 1-x/-y, and GaP/sub x/As/sub y/Sb/sub 1-x/-y. Even though these systems all have miscibility gaps, they are shown to be stable against spinodal decomposition at all temperatures due to the elastic strain energy inherent in coherent decomposition of single crystalline alloys.

Stringfellow, G.B.

1983-01-01

16

Thermal Conductivity of Ternary and Quaternary III-V Compounds.  

National Technical Information Service (NTIS)

This research project was directed at investigating methods of measuring the thermal conductivity of semiconducting alloys of III-V compounds (GaAlAs, GaInAs.GaInAsP) in a thin layer format. Generally, techniques for measuring the thermal properties of bu...

W. J. Collis E. K. Stefanakos

1983-01-01

17

Fingerprints of CuPt ordering in III-V semiconductor alloys: Valence-band splittings, band-gap reduction, and x-ray structure factors  

Microsoft Academic Search

Spontaneous CuPt ordering induces a band-gap reduction DeltaEg relative to the random alloy, a crystal field splitting DeltaCF at valence-band maximum, as well as an increase of spin-orbit splitting DeltaSO. We calculate these quantities for AlxIn1-xP, AlxIn1-xAs, GaxIn1-xP, and GaxIn1-xAs using the local density approximation (LDA), as well as the more reliable LDA-corrected formalism. We further provide these values and

Su-Huai Wei; Alex Zunger

1998-01-01

18

III-V Nitride Materials and Electron Devices  

Microsoft Academic Search

The electronic properties of III-V nitride materials make them applicable to high power microwave transistors. They are grown by molecular beam epitaxy or metal organic vapor phase epitaxy, and are direct band gap materials, with alloy gaps ranging from 6.2V. With no native substrates, SiC and sapphire are used. The dislocation properties are acceptor-like for larger band gaps, and donor-like

Lester F. Eastman

2005-01-01

19

Antimony Based III-V Thermophotovoltaic Devices  

SciTech Connect

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.

CA Wang

2004-06-09

20

Preparation of III-V semiconductor nanocrystals  

DOEpatents

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.

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

1996-04-09

21

Photodetectors using III-V nitrides  

DOEpatents

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.

Moustakas, Theodore D. (Dover, MA)

1998-01-01

22

Phonons in III–V nitrides: Confined phonons and interface phonons  

Microsoft Academic Search

Phonons in III–V nitrides are examined experimentally for dimensionally confined systems and for alloys of InGaN with a view towards understanding the phonon modes of these systems. Results are compared with the predictions of Loudon's model for uniaxial semiconductors. The modes of the InGaN system are compared with those of the AlGaN ternary alloy. The first Raman measurements of interface

M. Dutta; D. Alexson; L. Bergman; R. J Nemanich; R. Dupuis; K. W Kim; S. Komirenko; M. Stroscio

2001-01-01

23

III-V Semiconductor Materials on Silicon  

Microsoft Academic Search

GaAs- and InP-based lasers on Si substrates are highly desirable for the realization of OEICs and applications in long-range\\u000a optical data transmission, in optical interconnects, and in optical computing. GaAs, InP, and related compound materials on\\u000a Si are also interesting for the realization of very fast photoreceiver circuits. In particular, effective light emitters and\\u000a very fast photoreceivers consisting of III–V

Horst Zimmermann

24

FAST TRACK COMMUNICATION: Evaluation of the In concentration of an InxGa1-xSb alloy layer in cross-sectional HRTEM images of III-V semiconductor superlattices  

NASA Astrophysics Data System (ADS)

Atomic-scale positional resolved lattice spacing measurement is used to study the In concentration of the alloy layer in InAs/InxGa1-xSb superlattices by the molecular beam epitaxy techniques. The unstrained lattice distance d along three directions, [0 0 1], [1 1 0] and [1 1 1], was measured and the average lattice constant was calculated. The experimental lattice constants of InAs layers are almost equal to the theoretical ones. We have found that the average lattice constant of In0.25Ga0.75Sb alloy layers is in good agreement with previously reported Vegard's values, being slightly larger. The results indicate that the In concentration of x = 0.18 has a larger deviation compared with the designed values.

Quan, Maohua; Guo, Fengyun; Li, Meicheng; Zhao, Liancheng

2010-08-01

25

Historical perspective on radiation effects in III-V devices  

Microsoft Academic Search

A historical review of radiation effects on III-V semiconductor devices is presented. The discussion ranges from examining early material and device studies to present-day understanding of III-V radiation effects. The purpose of this paper is to provide present researchers with a summary of discoveries and lessons learned from previous failures and successes.

Todd R. Weatherford

2003-01-01

26

III–V semiconductor devices integrated with silicon III–V semiconductor devices integrated with silicon  

NASA Astrophysics Data System (ADS)

The integration of III–V semiconductor devices with silicon is one of the most topical challenges in current electronic materials research. The combination has the potential to exploit the unique optical and electronic functionality of III–V technology with the signal processing capabilities and advanced low-cost volume production techniques associated with silicon. Key industrial drivers include the use of high mobility III–V channel materials (InGaAs, InAs, InSb) to extend the performance of Si CMOS, the unification of electronics and photonics by combining photonic components (GaAs, InP) with a silicon platform for next-generation optical interconnects and the exploitation of large-area silicon substrates and high-volume Si processing capabilities to meet the challenges of low-cost production, a challenge which is particularly important for GaN-based devices in both power management and lighting applications. The diverse nature of the III–V and Si device approaches, materials technologies and the distinct differences between industrial Si and III–V processing have provided a major barrier to integration in the past. However, advances over the last decade in areas such as die transfer, wafer fusion and epitaxial growth have promoted widespread renewed interest. It is now timely to bring some of these topics together in a special issue covering a range of approaches and materials providing a snapshot of recent progress across the field. The issue opens a paper describing a strategy for the epitaxial integration of photonic devices where Kataria et al describe progress in the lateral overgrowth of InP/Si. As an alternative, Benjoucef and Reithmaier report on the potential of InAs quantum dots grown direct onto Si surfaces whilst Sandall et al describe the properties of similar InAs quantum dots as an optical modulator device. As an alternative to epitaxial integration approaches, Yokoyama et al describe a wafer bonding approach using a buried oxide concept, Corbett et al describe the transfer printing and bonding of III–V die on to CMOS wafers and Dastjerdi et al describe the optical performance of free-standing InGaAsP tube optical cavities which may be transferred to silicon substrates. Finally, describing important recent progress on GaN-based devices Jiang et al describe their work on InGaN light-emitting diodes on Si (1?1?1) substrates, Wallis et al describe similar structures with the emphasis on x-ray methods for the control of AlGaN buffer layer strain, Kumar et al describe low leakage current, large-area Schottky barrier photodetectors on Si, whilst Soltani et al describe their recent progress on AlGaN/GaN high electron mobility transistors grown on (1?0?0) and (1?1?0) silicon substrates. Overall, we think that this special issue of Semiconductor Science and Technology provides a timely overview of progress and the opportunities in this exciting and important field. Finally, we would like to thank the IOP editorial staff, in particular Alice Malhador, for their support, and we would also like to thank all contributors for their efforts in making this special issue possible.

Hopkinson, Mark; Martin, Trevor; Smowton, Peter

2013-09-01

27

Resonant Raman Scattering Studies of Iii-V Semiconductor Microstructures  

NASA Astrophysics Data System (ADS)

Raman spectroscopy, an inelastic light scattering technique, explores III-V semiconductors by conveying crystal lattice structural information and by probing carrier dynamics both directly and via the electron-phonon interaction. We have examined three physical systems accentuating three aspects of Raman utility. Al_{rm x}Ga_{rm 1-x} As alloy work emphasizes electronic behavior, migration enhanced epitaxy (MEE) studies highlight structural results, and a phonon-assisted lasing project underscores electron -phonon interaction. The disorder-induced frequency difference between the dipole-forbidden and dipole-allowed longitudinal optic (LO) modes in Al_{rm x} Ga_{rm 1-x}As alloys has been investigated as a function of laser photon energy, aluminum mole fraction x, and the indirect versus direct nature of the electronic band gap. For the indirect gap alloy, the intermediate resonant state is an X-valley electron effectively localized because of its short inelastic lifetime. Raman scattering via this state is described by a calculation of the Raman susceptibility that considers the random alloy potential generated by local concentration fluctuations. MEE is a new growth technology that can order these materials in two spatial directions. In a GaSb/AlSb system we show Raman evidence of this ordering via observation of zone folded acoustic modes and compare to AlAs/GaAs results. In other work resonant Raman documents the effects on the dipole-forbidden interface mode of a periodic corrugation introduced in AlAs barrier GaAs single quantum wells. Finally, we investigate "phonon-assisted" lasing in photopumped quantum well heterostructure lasers. Resonant Raman is the natural choice to probe this system purported to have an enhanced electron-phonon interaction. For both the AlGaAs/GaAs and AlGaAs/GaAs/InGaAs structures examined, we provide evidence that indicates first order "phonon -assisted" lasing is actually renormalized band gap luminescence filtered by absorption from the unpumped sample volume. Although unable to examine second order "phonon-assisted" lasing, we suggest that it is a stimulated Raman process.

Delaney, Malcolm Emil

1991-02-01

28

Surface Segregation in Epitaxy of III-V Compounds.  

National Technical Information Service (NTIS)

Surface segregation in III-V compound heterostrucures grown by Molecular Beam Epitaxy (MBE) and Metal-Organic Vapor Phase Epitaxy (MOVPE) is studied theorencally. The suggested model treats segregation as a transient process resulting in a delayed highly-...

S. Y. Karpov Y. N. Marakov

2001-01-01

29

Surface Passivation for III-V Compound Semiconductors.  

National Technical Information Service (NTIS)

A structure and method of fabrication are disclosed for improving surface passivation of III-V compound semiconductors. The invention exploits certain anion-rich compound semiconductors to form a high quality interface with a dielectric when anion mobilit...

A. Chen A. Yulius D. B. Salzman E. Harmon J. M. Woodall

2005-01-01

30

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

SciTech Connect

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.

Not Available

2011-06-01

31

Challenges of III–V materials in advanced CMOS logic  

Microsoft Academic Search

The superior transport properties of III–V materials are promising candidates to achieve improved performance at low power. This paper examines the module challenges of III–V materials in advanced CMOS at or beyond the 10 nm technology node, and reports VLSI compatible epi, junction, contact and gate stack process modules with Xj<10nm, ND=5×1019 cm?3, ?c= 6?.µm2 and Dit = 4×1012 eV?1

P. D. Kirsch; R. J. W. Hill; J. Huang; W. Y. Loh; T.-W. Kim; M. H. Wong; B. G. Min; C. Huffman; D. Veksler; C. D. Young; K. W. Ang; I. Ali; R. T. P. Lee; T. Ngai; A. Wang; W.-E. Wang; T. H. Cunningham; Y. T. Chen; P. Y. Hung; E. Bersch; B. Sassman; M. Cruz; S. Trammell; R. Droopad; S. Oktybrysky; J. C. Lee; G. Bersuker; C. Hobbs; R. Jammy

2012-01-01

32

New Approaches to Direct Bandgap III-V Materials for LWIR Detector Applications  

NASA Astrophysics Data System (ADS)

Infrared (IR) detector materials based on III-V semiconductors are an affordable alternative to HgCdTe, which is the current material of choice for most high performance IR focal plane array systems fielded in the Army. Based on the assumption that III-V compounds do not have an inherently small bandgap enabling operation out to 10 ?m, the long wave infrared (LWIR) range, there has been substantial research investment in superlattice (SL) approaches. For this reason, quantum structures such as quantum well IR photodetectors (QWIPs) and type-II strained-layer superlattices (SLS) are grown to take advantage of confinement effects and to induce an effective bandgap in the desired range. The drawbacks of these approaches include inherently low quantum efficiencies and operating temperature for QWIPs, and very short minority carrier lifetimes for SLS detectors. In this presentation, we will discuss approaches for developing III-V, direct bandgap, dilute N and Bi alloys grown by molecular beam epitaxy (MBE) for LWIR applications.

Sarney, W. L.; Svensson, S. P.; Hier, H.; Donetsky, D.; Wang, D.; Shterengas, L.; Suchalkin, S.; Belenky, G.

2011-12-01

33

Electronic band structure calculations for biaxially strained Si, Ge, and III-V semiconductors  

NASA Astrophysics Data System (ADS)

Electronic band structure and effective masses for relaxed and biaxially strained Si, Ge, III-V compound semiconductors (GaAs, GaSb, InAs, InSb, InP) and their alloys (InxGa1-xAs, InxGa1-xSb) on different interface orientations, (001), (110), and (111), are calculated using nonlocal empirical pseudopotential with spin-orbit interaction. Local and nonlocal pseudopotential parameters are obtained by fitting transport-relevant quantities, such as band gap and deformation potentials, to available experimental data. A cubic-spline interpolation is used to extend local form factors to arbitrary q and to obtain correct workfunctions. The nonlocal and spin-orbit terms are linearly interpolated between anions and cations for III-V semiconductors. The virtual crystal approximation is employed for the InxGa1-xAs and InxGa1-xSb alloys and deformation potentials are determined using linear deformation-potential theory. Band gap bowing parameters are extracted using least-square fitting for relaxed alloys and for strained InxGa1-xAs on (001), (110), and (111) InP. The dependence on biaxial strain of the electron and hole effective masses at the symmetry points ?, X, and L exhibits a continuous variation at ? and L but sudden changes appear at ? minima caused by the flatness of the dispersion along the ? line near the minimum.

Kim, Jiseok; Fischetti, Massimo V.

2010-07-01

34

Isoelectronic dopant and surfactant effects in III/V semiconductors  

NASA Astrophysics Data System (ADS)

Organometallic vapor-phase epitaxy (OMVPE) is a versatile growth technique used for production of many III/V semiconductors. Surface processes are an important aspect of any epitaxial growth technique. Understanding these surface processes and the ability to control them is of paramount importance to developing materials with specific properties for devices. This study focuses on the effects of using isoelectronic elements on materials properties of III/V semiconductors grown via OMVPE. The addition of diborane during the growth of GaAs is investigated. The solubility of B in GaAs is calculated to be only 5 x 1015cm -3. The bowing parameter is calculated to be 11.8 +/- 0.6 eV. Experimental data show that B incorporation is highly dependent on growth conditions and changed by a factor of 103 for conditions studied. The maximum amount of B incorporated was 4 x 1019cm -3. Photoluminescence (PL) experiments show that the band gap of GaAs was reduced with B incorporation, and was used to extrapolate a bowing parameter of 12.4 +/- 4.5 eV in close agreement with the theoretical value. This study also presents the results of using dimethylhydrazine during the growth of GaP and GaInP. The N content in GaP is studied up to approximately 1%. PL experiments show an increase in PL intensity for low concentrations of N. The PL progresses from N-N pairs to a N triplet state at 2070 meV to a broad peak at lower energy with no sharp features. However, at the highest N concentration of 2.3 x 1020cm-3, the PL intensity is significantly reduced. Annealing the sample increased the integrated intensity by 30%. The use of the surfactant N during the growth of GaInP produces changes in microstructure, morphology, and composition, while only 2 x 10 18cm-3 N is incorporated. Experiments show that ordering is reduced and suggests that N disorders GaInP via two mechanisms, (1) by replacing P dimers reducing the thermodynamic driving force, and (2) by roughening the surface creating pyramid features with angles >8°. The addition of the surfactants Sb and Bi enhances the Zn and H concentration in the solid during the growth of Zn-doped GaInP. It is found that adding a small amount of either triethylantimony or trimethylbismuth (surfactant/V v ? 5.5 x 10-4) can increase the Zn concentration by a factor of 2.1. Secondary ion mass spectroscopy found that Bi and Sb were not significantly incorporated into the solid. Thus, these effects are not from alloying, but suggest that neutral Zn-H complexes are incorporated during growth leading to increased Zn in the solid.

Chapman, David Cook

35

Effect of mismatch strain on band gap in III-V semiconductors  

Microsoft Academic Search

Interfacial elastic strain induced by the lattice parameter mismatch between epilayer and substrate results in significant energy–band-gap shifts for III-V alloys. The epilayers used in this study are GaxIn1?xAs on (100) InP and GaxIn1?xP on (100) GaAs prepared by organometallic vapor phase epitaxy. For layer thicknesses between 1 and 1.5 ?m, and ?as.f.\\/a0?3.5×10?3 the misfit strain is assumed to be

C. P. Kuo; S. K. Vong; R. M. Cohen; G. B. Stringfellow

1985-01-01

36

Ion Implantation in Iii-V Semiconductor Technology  

NASA Astrophysics Data System (ADS)

A review is given of the applications of ion implantation in III-V compound semiconductor device technology, beginning with the fundamentals of ion stopping in these materials and describing the use of implantation for both doping and isolation. There is increasing interest in the use of MeV implantation to create unique doping profiles or for the isolation of thick device structures such as heterojunction bipolar transistors or multi quantum well lasers, and we give details of these areas and the metal masking layers necessary for selective area processing. Finally, examples are given of the use of implantation in a variety of III-V devices.

Pearton, S. J.

37

III-V Multijunctions in Amonix Solar Power Plants  

NASA Astrophysics Data System (ADS)

Amonix has installed over 300 kW of CPV systems based on III-V multijunctions. A performance model has been developed that effectively predicts system peak power and aggregate energy generation. System AC efficiencies reach 25% and power is expected to increase by over 10% in the next year.

Kinsey, Geoffrey S.; Gordon, Robert; Stone, Kenneth; Garboushian, Vahan

2010-10-01

38

III-V MOSFETs: Scaling laws, scaling limits, fabrication processes  

Microsoft Academic Search

III-V FETs are in development for both THz and VLSI applications. In VLSI, high drive currents are sought at low gate drive voltages, while in THz circuits, high cutoff frequencies are required. In both cases, source and drain access resistivities must be decreased, and transconductance and drain current per unit gate width must be increased by reducing the gate dielectric

M. J. W. Rodwell; U. Singisetti; M. Wistey; G. J. Burek; A. Carter; A. Baraskar; J. Law; B. J. Thibeault; Eun Ji Kim; B. Shin; Yong-ju Lee; S. Steiger; S. Lee; H. Ryu; Y. Tan; G. Hegde; L. Wang; E. Chagarov; A. C. Gossard; W. Frensley; A. Kummel; C. Palmstrom; P. C. McIntyre; T. Boykin; G. Klimek; P. Asbeck

2010-01-01

39

Beam Assisted Fabrication of III-V/Si Monolithic Devices.  

National Technical Information Service (NTIS)

The results of a two-year project to explore new methods for deposition of III-V semiconducting film on silicon substrates are summarized. Gas-source molecular beam epitaxy was used for the first time to achieve heteroepitaxy of InP on Si. The InP films c...

G. J. Collins G. Y. Robinson R. Solanki

1989-01-01

40

Bulk crystal growth of antimonide based III-V compounds for thermophotovoltaics applications  

SciTech Connect

In this paper, the bulk growth of crack-free GaInSb and single phase GaInAsSb alloys are presented. A new class of III-V quasi-binary [A{sub III}B{sub V}]{sub 12{minus}x}[C{sub III}D{sub V}]{sub x} semiconductor alloys has been synthesized and bulk crystals grown from the melt for the first time. The present investigation is focused on the quasi-binary alloy (GaSb){sub 1{minus}x}(InAs){sub x} (0 < x < 0.05) due to its importance for thermophotovoltaic applications. The structural properties of this melt-grown quasi-binary alloy are found to be significantly different from the conventional quaternary compound Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} with composition x = y. Synthesis and growth procedures are discussed. For the growth of ternary alloys, it was demonstrated that forced convection or mixing in the melt during directional solidification of In{sub x}Ga{sub 1{minus}x}Sb (0 < x < 0.1) significantly reduces cracks in the crystals.

Dutta, P.S.; Ostrogorsky, A.G.; Gutmann, R.J. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1998-10-01

41

III-V/Silicon Lattice-Matched Tandem Solar Cells  

SciTech Connect

A two-junction device consisting of a 1.7-eV GaNPAs junction on a 1.1-eV silicon junction has the theoretical potential to achieve nearly optimal efficiency for a two-junction tandem cell. We have demonstrated a monolithic III-V-on-silicon tandem solar cell in which most of the III-V layers are nearly lattice-matched to the silicon substrate. The cell includes a GaNPAs top cell, a GaP-based tunnel junction (TJ), and a diffused silicon junction formed during the epitaxial growth of GaNP on the silicon substrate. To accomplish this, we have developed techniques for the growth of high crystalline quality lattice-matched GaNPAs on silicon by metal-organic vapor-phase epitaxy.

Geisz, J.; Olson, J.; Friedman, D.; Kurtz, S.; McMahon, W.; Romero, M.; Reedy, R.; Jones, K.; Norman, A.; Duda, A.; Kibbler, A.; Kramer, C.; Young, M.

2005-01-01

42

Investigation of new semiinsulating behavior of III-V compounds  

NASA Astrophysics Data System (ADS)

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.

Lagowski, Jacek

1990-02-01

43

Bulk III-V compound semiconductor crystal growth  

Microsoft Academic Search

This paper discusses the production of III-V compound semiconductor substrates characterized by structural perfection and chemical homogeneity. Special attention is given to the use of vertical-gradient-freeze (VGF) technique for producing large high-quality GaP, InP, and GaAs crystals. The characteristics of VGF-grown GaAs crystals are described, including the dislocation-count distribution, etch-pit density, and electrical properties. The VGF-grown crystals have very low

Jim E. Clemans; Theophilus I. Ejim; William A. Gault; Eric M. Monberg

1989-01-01

44

III-V nitrides for electronic and optoelectronic applications  

Microsoft Academic Search

Recent developments in III-V nitride thin-film materials for electronic and optoelectronic applications are reviewed. The problems that are limiting the development of these materials and devices made from them are discussed. The properties of cubic boron nitride, aluminum nitride, gallium nitride, AlN\\/GaN solid solutions and heterostructures, and indium nitride are discussed. It is pointed out that the lack of a

ROBERT F. DAVIS

1991-01-01

45

Direct determination of III-V semiconductor surface band gaps  

Microsoft Academic Search

Applying in situ combination of angle-resolved photoemission and inverse photoemission to cleaved III-V compound semiconductor (110) surfaces, we have determined the surface band gaps between the filled anion-derived dangling-bound state A5 and the empty cation-derived state C3 at the Gamma¯, X¯ ', X¯, and M¯ points of the surface Brillouin zone. The values of the surface band gaps of the

H. Carstensen; R. Claessen; R. Manzke; M. Skibowski

1990-01-01

46

Raman and Photoluminescence Studies of III-V Nitrides  

Microsoft Academic Search

Raman scattering and photoluminescence (PL) studies of III-V nitrides are addressed focusing on recombination mechanisms in superlattics (SL), phonon lifetimes in crystals, and phonon dynamics. A detailed study of PL of GaN\\/AlGaN based SL is presented [1]. The dependence of the PL emission energy, linewidth, and intensity on temperature in the low temperature regime is consistent with recombination mechanisms involving

Leah Bergman

2000-01-01

47

Ballistic to Diffusive Crossover in III–V Nanowire Transistors  

Microsoft Academic Search

In this paper, the authors examine the crossover between ballistic and diffusive transport in III-V nanowire transistors. The authors find that at lower drain voltages the ballistic-to-diffusive crossover occurs at channel lengths of approximately 2.3 nm at room temperature. However, when increasing the drain voltage, the ballistic-to-diffusive crossover can be more than nine times as long at room temperature. As

M. J. Gilbert; Sanjay K. Banerjee

2007-01-01

48

Ballistic transport and luminescence in III-V semiconductor nanostructures  

Microsoft Academic Search

This thesis describes research to develop novel scanning probe methods employing ballistic electron emission to characterize nanoscale carrier transport and luminescence of quantum-confined III-V semiconductor nanostructures. First, spectroscopic and microscopic ballistic electron emission luminescence (BEEL) of an InAs quantum dot heterostructure based on three-terminal hot electron injection using a scanning tunneling microscope and a planar tunnel-junction transistor is described in

Wei Yi

2005-01-01

49

New phenomena in Schottky barrier formation on III V compounds  

Microsoft Academic Search

The possibility of a defect mechanism is proposed to explain the Fermi-level pinning in Schottky barriers on III--V semiconductor surfaces. This suggestion comes from the results of photoemission spectroscopy applied to the study of formation of metal--semiconductor barrier heights. Changes in the electronic structure and composition of the interface are studied. For Au metal overlayers on the (110) surfaces of

I. Lindau; P. W. Chye; C. M. Garner; P. Pianetta; C. Y. Su; W. E. Spicer

1978-01-01

50

Optical dielectric functions of wurtzite III-V semiconductors  

NASA Astrophysics Data System (ADS)

Optical properties of semiconductors can exhibit strong polarization dependence due to crystalline anisotropy. A number of recent experiments has shown that the photoluminescence intensity in free standing nanowires is polarization dependent. One contribution to this effect is the anisotropy of the dielectric function due to the fact that most nanowires crystalize in the wurtzite form. While little is known experimentally about the band structures of wurtzite phase III-V semiconductors, we have previously predicted the bulk band structure of nine III-V semiconductors in the wurtzite phase. Here, we predict the frequency dependent dielectric functions for nine non-nitride wurtzite phase III-V semiconductors (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb).Their complex dielectric functions are calculated in the dipole approximation for light polarized parallel and perpendicular to the caxis of the crystal. Momentum matrix elements are evaluated on a dense grid of special k points using empirical pseudopotential wave functions. Corrections to the momentum matrix elements, to account for the missing core states, are made using a scaling factor which is determined from the zinc-blende polytypes. Simple analytic expressions are provided for the dispersion relations in the vicinity of the respective fundamental absorption edges.

de, Amrit; Pryor, Craig E.

2012-03-01

51

Integration of Carbon Nanotubes with III-V(110) Surfaces  

NASA Astrophysics Data System (ADS)

We have used scanning tunneling microscopy (STM) to investigate the unique electronic and physical properties of individual isolated carbon nanotubes dispersed onto semiconducting III-V substrates in an ultrahigh vacuum (UHV) environment. Pristine III-V(110) surfaces were obtained through in situ cleavage, with single-walled carbon nanotubes (SWNTs) subsequently deposited via an UHV-compatible Dry Contact Transfer process[1]. Room temperature STM imagery confirms the intact transfer of individual tubes to the surface, while STM-enabled nanomanipulation suggests a substrate-induced stabilization of isolated SWNTs aligned along the (1bar 1 0) crystallographic direction, in registration with the substrate sublattice rows. Additionally, current image tunneling spectroscopy (CITS) maps of these SWNT/III-V(110) systems yield correlated topographic and electronic information with subnanometer resolution that provide evidence of the sensitivity of local nanotube electronic character to both inherent features of the nanotube as well as to proximal features of the underlying support substrate. [1]P.M. Albrecht and J.W. Lyding, APL 83, 5029 (2003).

Ruppalt, Laura; Lyding, Joseph

2006-03-01

52

Computational discovery of single-layer III-V materials  

NASA Astrophysics Data System (ADS)

Single-layer materials open up tremendous opportunities for nanoelectronic devices. Using a first-principles design approach we identify a previously unrecognized family of single-layer III-V materials. We determine their energetic and dynamical stability, identify a surprising reconstruction, and calculate their electronic properties using a hybrid density functional and the G0W0 method. Finally, we find that metal substrates stabilize these as-yet hypothetical materials. Our results provide guidance for experimental synthesis efforts and future searches of single-layer materials suitable for device applications.

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

2013-04-01

53

High-Speed III-V Semiconductor Devices  

Microsoft Academic Search

In this chapter the basic device physics, operational principles, and general characteristics of high-speed III-V compound\\u000a semiconductor devices such as MESFETs and HEMTs are presented. The devices described here include GaAs- and InPbased metal–semiconductor\\u000a field-effect transistors (MESFETs) and high electron mobility transistors (HEMTs). The GaAs-based high-speed devices are fabricated\\u000a using the lattice-matched GaAs\\/AlGaAs material system grown on a semiinsulating GaAs

Sheng S. Li

54

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

NASA Astrophysics Data System (ADS)

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.

Sun, Xiankai

55

III-V Nitride based piezoresistive microcantilever for sensing applications  

NASA Astrophysics Data System (ADS)

III-V Nitride based microcantilevers, with AlGaN/GaN heterostructure field effect transistor as the piezoresistive deflection transducer, have been investigated under steady state, transient, ac, and UV illuminated conditions and compared to theoretical calculations. The steady state transverse gauge factor (GFt) was found to be much larger than theoretical estimates and increased regularly with more negative gate bias. Transient GFt demonstrated opposite sign but similar gate bias dependence and was measured as high as ~860. Measurements under ac biasing conditions and UV illumination resulted in a lower GFt of ~13, which agrees with theoretical calculations owing to elimination of charge trapping effects.

Qazi, Muhammad; Deroller, Nicholas; Talukdar, Abdul; Koley, Goutam

2011-11-01

56

Feasibility of III V on-silicon strain relaxed substrates  

NASA Astrophysics Data System (ADS)

In this work we have investigated the feasibility of using ultrathin III V films stuck on silicon as seed layers for subsequent epitaxial growths. The sticking is done by a thick viscous layer, which is assumed to act as an accommodating layer allowing the elastic relaxation of the initially strained III V film. Two kinds of viscous layers have been employed: the Apiezon wax for an academic study and the borophosphorosilicate glass (BPSG) for an actual technological study. From the academic investigation, viz, with the Apiezon wax, we have learned how undulation and in-plane expansion compete as elastic relaxation processes. In fact, a final uniform and flat seed-layer morphology is hard to achieve and, when so, only for very small samples. In the actual investigation, viz, with the BPSG, wafer bonding techniques have been successfully used to transfer a 20 nm thick InAs0.25P0.75 film onto a Si host substrate. Then, a post-process Rapid Thermal Annealing (RTA) has been performed to lower the BPSG viscosity and allow the 0.8%-strained film to relax. These two preliminary studies have clearly shown the feasibility of the approach even if the sticking-interface stability has to be greatly improved from a chemical point of view before considering any practical application in optoelectronics.

Kostrzewa, M.; Grenet, G.; Regreny, P.; Leclercq, J. L.; Perreau, P.; Jalaguier, E.; di Cioccio, L.; Hollinger, G.

2005-02-01

57

Optical Properties of III-V Semiconductors in Wurtzite Phase  

NASA Astrophysics Data System (ADS)

A number of recent experiments have shown that the photoluminescence intensity in free standing nanowires is polarization dependent. One contribution to this effect is the optical anisotropy arising from the tendency of the nanowires to crystallize in wurtzite form. We calculate the frequency dependent dielectric functions for nine non-Nitride wurtzite phase III-V semiconductors (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs and InSb), based on our maximally constrained empirical pseudopotential bulk band structure calculations. Their complex dielectric functions are calculated in the dipole approximation for polarization perpendicular and parallel to the c-axis of the crystal. We also predict their reflectivity spectra and the static dielectric constants. Optical selection rules are used to explain key features of the dielectric functions. In general it is seen that the III-V wurtzite phase semiconductors exhibit strong optical anisotropy which suggests that they could be potentially useful as nonlinear optical crystals.

de, Amrit; Pryor, Craig

2012-02-01

58

Hydrogen chemisorption on cleavage faces of III-V compounds  

NASA Astrophysics Data System (ADS)

In this paper a number of experimental results dealing with the study of the electronic properties of H-exposed III-V semiconductor cleavage surfaces will be reviewed. The principal aim of the paper is to show how surface sensitive spectroscopies like electron energy loss spectroscopy (EELS) and ultraviolet photoemission spectroscopy (UPS) can be used to investigate these systems. The paper is focused on GaAs(1 1 0):H. GaAs(1 1 0) is one of the most widely investigated and better known semiconductor surfaces: this system can be taken as a case study for the interaction of H with III-V semiconductor cleavage surfaces. The paper is divided into two parts. In the first part EELS and UPS are used and combined to get information about the surface valence states. In the second part core level (CL) photoemission results are presented and discussed. Combining theory with the above results, a unified picture of the H interaction with the (1 1 0) surface of GaAs comes out. H atoms chemisorb at the early stages along the dangling bond directions of the ideal not relaxed surface, removing the surface relaxation and introducing at the same time defects at the surface. At the same time the interaction with H produces a Ga enrichment at the surface ascribed to As desorption. On leave from: Istituto di Acustica ``O.M. Corbino'' del C.N.R., Via Cassia 1216, 00189 Roma, Italy.

Nannarone, S.; Sorba, L.

1991-04-01

59

DX centers in III-V semiconductors under hydrostatic pressure  

SciTech Connect

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.

Wolk, J.A.

1992-11-01

60

Sulfur passivation techniques for III-V wafer bonding  

NASA Astrophysics Data System (ADS)

The use of direct wafer bonding in a multijunction III-V solar cell structure requires the formation of a low resistance bonded interface with minimal thermal treatment. A wafer bonded interface behaves as two independent surfaces in close proximity, hence a major source of resistance is Fermi level pinning common in III-V surfaces. This study demonstrates the use of sulfur passivation in III-V wafer bonding to reduce the energy barrier at the interface. Two different sulfur passivation processes are addressed. A dry sulfur passivation method that utilizes elemental sulfur vapor activated by ultraviolet light in vacuum is compared with aqueous sulfide and native oxide etch treatments. Through the addition of a sulfur desorption step in vacuum, the UV-S treatment achieves bondable surfaces free of particles contamination or surface roughening. X-ray photoelectron spectroscopy measurements of the sulfur treated GaAs surfaces find lower levels of oxide and the appearance of sulfide species. After 4 hrs of air exposure, the UV-S treated GaAs actually showed an increase in the amount of sulfide bonded to the semiconductor, resulting in less oxidation compared to the aqueous sulfide treatment. Large area bonding is achieved for sulfur treated GaAs / GaAs and InP / InP with bulk fracture strength achieved after annealing at 400 °C and 300 °C respectively, without large compressive forces. The electrical conductivity across a sulfur treated 400 °C bonded n-GaAs/n-GaAs interface significantly increased with a short anneal (1-2 minutes) at elevated temperatures (50--600 °C). Interfaces treated with the NH4OH oxide etch, on the other hand, exhibited only mild improvement in accordance with previously published studies in this area. TEM and STEM images revealed similar interfacial microstructure changes with annealing for both sulfur treated and NH4OH interfaces, whereby some areas have direct semiconductor-semiconductor contact without any interfacial layer. Fitting the observed temperature dependence of zero bias conductance using a model for tunneling through a grain boundary reveals that the addition of sulfur at the interface lowered the interfacial energy barrier by 0.2 eV. The interface resistance for these sulfur-treated structures is less than 0.03 O·cm 2 at room temperature. These results emphasize that sulfur passivation techniques reduce interface states that otherwise limit the implementation of wafer bonding for high efficiency solar cells and other devices.

Jackson, Michael James

61

Bulk III-V compound semiconductor crystal growth  

NASA Astrophysics Data System (ADS)

This paper discusses the production of III-V compound semiconductor substrates characterized by structural perfection and chemical homogeneity. Special attention is given to the use of vertical-gradient-freeze (VGF) technique for producing large high-quality GaP, InP, and GaAs crystals. The characteristics of VGF-grown GaAs crystals are described, including the dislocation-count distribution, etch-pit density, and electrical properties. The VGF-grown crystals have very low levels of crystalline defects distributed uniformly throughout the crystal; growth striations are planar and are greatly reduced in comparison with those observed in materials produced by the liquid-encapsulated Czochralski method. Yields obtained with the VGF method compare favorably with those of other commercial crystal-growth processes.

Clemans, Jim E.; Ejim, Theophilus I.; Gault, William A.; Monberg, Eric M.

1989-02-01

62

III-V nitride semiconductors for solar hydrogen production  

NASA Astrophysics Data System (ADS)

Photoelectrochemical cells are devices that can convert solar radiation to hydrogen gas through a water decomposition process. In this process, energy is converted from incident photons to the bonds of the generated H2 molecules. The solar radiation absorption, electron-hole pair splitting, and photoelectrolysis half reactions all occur in the vicinity of the electrode-electrolyte interface. As a result, engineering the electrode material and its interaction with the electrolyte is important in investigating and improving the energy conversion process in these devices. III-V nitride materials are promising candidates for photoelectrochemical energy applications. We demonstrate solar-to-hydrogen conversion in these cells using p-type GaN and n-type InGaN as a photocathode and photoanode material, respectively. Additionally, we demonstrate heteroepitaxial MOCVD growth of GaP on Si, enabling future work in developing GaPN as a photocathode material.

Parameshwaran, Vijay; Gallinat, Chad; Enck, Ryan W.; Sampath, Anand V.; Shen, Paul H.; Kuykendall, Tevye; Aloni, Shaul; Wraback, Michael; Clemens, Bruce M.

2012-05-01

63

Spin-Seebeck Effect in III-V Based Semiconductors  

NASA Astrophysics Data System (ADS)

The spin-Seebeck effect has now been observed in metals^1 (NiFe), semiconductors^2 (GaMnAs), and insulators^3 (YIG). It consists of a thermally generated spin distribution that is phonon driven. Here we extend our measurements of the spin-Seebeck effect to other group III-V based magnetic semiconductors and present measurements of conventional thermomagnetic and galvanomagnetic properties as well as the spin-Seebeck effect. Work supported by the National Science Foundation, NSF-CBET-1133589 1. K. Uchida, et al., Nature 455 778 (2008) 2. C.M. Jaworski et al., Nature Materials 8 898 (2010), Phys. Rev. Lett. 106 186601 (2011) 3. K. Uchida, et al., Nature Materials 8 893 (2010)

Jaworski, Christopher M.; Myers, Roberto C.; Heremans, Joseph P.

2012-02-01

64

III-V Nanowire Array Growth by Selective Area Epitaxy  

NASA Astrophysics Data System (ADS)

III-V semiconductor nanowires are unique material phase due to their high aspect ratio, large surface area, and strong quantum confinement. This affords the opportunity to control charge transport and optical properties for electrical and photonic applications. Nanoscale selective area metalorganic chemical vapor deposition growth (NS-SAG) is a promising technique to maximize control of nanowire diameter and position, which are essential for device application. In this work, InP and GaAs nanowire arrays are grown by NS-SAG. We observe enhanced sidewall growth and array uniformity disorder in high growth rate condition. Disorder in surface morphology and array uniformity of InP nanowire array is explained by enhanced growth on the sidewall and stacking faults. We also find that AsH3 decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

Chu, Hyung-Joon; Yeh, Tingwei; Stewart, Lawrence; Dapkus, P. Daniel

2011-12-01

65

Nanostencil lithography for fabrication of III-V nanostructures  

NASA Astrophysics Data System (ADS)

Nanostencil Lithography (NStL), while comparatively still in infant stages, is proving to be a viable option for low-cost and high resolution fabrication. An ideal stencil for NStL consists of a low-stressed silicon nitride membrane supported on a silicon chip with required patterned features in nanometer range that become apertures. The stencil is used as a shadow mask and placed in close contact on top of a substrate/wafer. This pair is then ready for either depositing metal through the apertures in the stencil using variety of deposition techniques or etching the substrate using dry etching techniques with stencil acting as a mask. The nanostencils were fabricated using focused ion beam writing on a silicon nitride window/membrane. We made well-ordered array of 700 nm diameter and 15 nm thick gold and chromium nanodots on III-V substrate. Metal layers were deposited using e-beam evaporator. The formed gold nanodots can be used for vapor-liquid-solid nanowire growth (bottom-up), while the chromium nanodots were used as a mask for reactive ion etching of GaAs structures, for instance, fabricating nanowires (top-down approach). We used the nanostencil directly as a mask for dry etching of InP substrate for making nanoholes array. Making these types of nanoholes in silicon oxide layer deposited on the top of III-V substrate opens the possibility to use in selective area growth of nanowires. Additionally, we fabricated optical nanoantenna structures to demonstrate other possible usage of NStL.

Vora, Kaushal; Karouta, Fouad; Jagadish, Chennupati

2013-09-01

66

Status of ion implantation doping and isolation of III-V nitrides  

SciTech Connect

Ion implantation doping and isolation has played a critical role in the realization of high performance photonic and electronic devices in all mature semiconductor material systems. This is also expected to be the case for the binary III-V nitrides (InN, GaN, and AlN) and their alloys as the epitaxial material quality improves and more advanced device structures are fabricated. With this in mind, we review the status of implant doping and isolation of GaN and the ternary alloys AlGaN, InGaN, and InAlN. In particular, we reported on the successful n- and p-type doping of GaN by ion implantation of Mg+P and Si, respectively, and subsequent high temperature rapid thermal anneals in excess of 1000{degrees}C. In the area of implant isolation, N-implantation has been shown to compensate both n- and p-type GaN, N and O-implantation effectively compensates InAlN, and InGaN shows limited compensation with either N or F implantation.

Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Pearton, S.J.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States)] [and others

1995-09-01

67

Design and growth of III–V nanowire solar cell arrays on low cost substrates  

Microsoft Academic Search

State-of-the-art III-V multijunction cells have achieved a record efficiency of 42.8%, which has fueled great interest in the utility sector for large-scale deployment. However, III-V solar cells have thus far proven too expensive for widespread terrestrial applications due to the combined cost of substrates, growth processes, and materials. Here, we propose a novel III-V solar cell based on the epitaxial

Anjia Gu; Yijie Huo; Shu Hu; T. Sarmiento; Evan Pickett; Dong Liang; Shuang Li; Angie Lin; Shruti Thombare; Zongfu Yu; Shanhui Fan; P. McIntyre; Yi Cui; James Harris

2010-01-01

68

III–V Nanowires on Si Substrate: Selective-Area Growth and Device Applications  

Microsoft Academic Search

III-V nanowires (NWs) on Si are promising building blocks for future nanoscale electrical and optical devices on Si plat- forms. We present position-controlled and orientation-controlled growth of InAs, GaAs, and InGaAs NWs on Si by selective-area growth, and discuss how to control growth directions of III-V NW on Si. Basic studies on III-V\\/Si interface showing heteroepitaxial growth with misfit dislocations

Katsuhiro Tomioka; Tomotaka Tanaka; Shinjiro Hara; Kenji Hiruma; Takashi Fukui

2011-01-01

69

Spectroscopic characterization of III-V semiconductor nanomaterials  

NASA Astrophysics Data System (ADS)

III-V semiconductor materials form a broad basis for optoelectronic applications, including the broad basis of the telecom industry as well as smaller markets for high-mobility transistors. In a somewhat analogous manner as the traditional silicon logic industry has so heavily depended upon process manufacturing development, optoelectronics often relies instead on materials innovations. This thesis focuses particularly on III-V semiconductor nanomaterials, detailed characterization of which is invaluable for translating the exhibited behavior into useful applications. Specifically, the original research described in these thesis chapters is an investigation of semiconductors at a fundamental materials level, because the nanostructures in which they appear crystallize in quite atypical forms for the given semiconductors. Rather than restricting the experimental approaches to any one particular technique, many different types of optical spectroscopies are developed and applied where relevant to elucidate the connection between the crystalline structure and exhibited properties. In the first chapters, for example, a wurtzite crystalline form of the prototypical zincblende III-V binary semiconductor, GaAs, is explored through polarization-dependent Raman spectroscopy and temperature-dependent photoluminescence, as well as second-harmonic generation (SHG). The altered symmetry properties of the wurtzite crystalline structure are particularly evident in the Raman and SHG polarization dependences, all within a bulk material realm. A rather different but deeply elegant aspect of crystalline symmetry in GaAs is explored in a separate study on zincblende GaAs samples quantum-confined in one direction, i.e. quantum well structures, whose quantization direction corresponds to the (110) direction. The (110) orientation modifies the low-temperature electron spin relaxation mechanisms available compared to the usual (001) samples, leading to altered spin coherence times explored through a novel spectroscopic technique first formulated for the rather different purpose of dispersion engineering for slow-light schemes. The frequency-resolved technique combined with the unusual (110) quantum wells in a furthermore atypical waveguide experimental geometry has revealed fascinating behavior of electron spin splitting which points to the possibility of optically orienting electron spins with linearly polarized light---an experimental result supporting a theoretical description of the phenomenon itself only a few years old. Lastly, to explore a space of further-restricted dimensionality, the final chapters describe InP semiconductor nanowires with dimensions small enough to be considered truly one-dimensional. Like the bulk GaAs of the first few chapters, the InP nanowires here crystallize in a wurtzite structure. In the InP nanowire case, though, the experimental techniques explored for characterization are temperature-dependent time-integrated photoluminescence at the single-wire level (including samples with InAsP insertions) and time-resolved photoluminescence at the ensemble level. The carrier dynamics revealed through these time-resolved studies are the first of their kind for wurtzite InP nanowires. The chapters are thus ordered as a progression from three (bulk), to two (quantum well), to one (nanowire), to zero dimensions (axially-structured nanowire), with the uniting theme the emphasis on connecting the semiconductor nanomaterials' crystallinity to its exhibited properties by relevant experimental spectroscopic techniques, whether these are standard methods or effectively invented for the case at hand.

Crankshaw, Shanna Marie

70

Experimental and theoretical investigation into the difficulties of thallium incorporation into III-V semiconductors  

NASA Astrophysics Data System (ADS)

The aim of this paper is to show—from both an experimental and a theoretical point of view—why it is so difficult to incorporate thallium into III-V semiconductors. The experimental part describes how Ga1-xTlxAs epilayers on GaAs(001) and In1-xTlxAs epilayers on InAs(001) can be obtained using molecular beam epitaxy (MBE). Tl is found to be much easier to incorporate into GaAs (7% over 50 nm) than into InAs (2.5% over 50 nm) despite the higher elastic stress in the former than in the latter. Once pseudomorphic Ga1-xTlxAs epilayers of sufficient thickness have been successfully obtained, the lattice and elastic parameters for the Tl-As bonding in Ga1-xTlxAs alloys are deduced by combining results from double-crystal x-ray diffraction and Rutherford backscattering (RBS) spectrometry . The theoretical part proposes a tentative explanation—within Keating’s valence force field framework—for the difficulties met when incorporating Tl into III-V compounds. When incorporated into either a GaAs or an InAs bulk matrix, the Tl atoms keep away from each other by avoiding being first neighbors in the III-element sublattice, but the magnitude of the phenomenon is clearly much smaller in the InAs case than in the GaAs case. However, this effect alone cannot explain the difference between GaAs and InAs versus Tl incorporation. Turning next to surface effects, the paper demonstrates that the dimers on the InAs surface are better stabilized by the presence of Tl than are those on the GaAs surface. Last, a stronger tendency to form diluted ordered alloy clusters for GaAs than for InAs is demonstrated, which could be a reason for the greater difficulties encountered when incorporating Tl into InAs matrix than into GaAs.

Beneyton, R.; Grenet, G.; Regreny, Ph.; Gendry, M.; Hollinger, G.; Canut, B.; Priester, C.

2005-09-01

71

III-V heterostructures for electronic/photonic devices  

SciTech Connect

The symposium presented in this book covered a wide range of epitaxial techniques important for III-V compound semiconductors. The topics range from fundamental growth kinetics and models to the production issues of safety and multiple wafers per run. In particular, the symposium held a special session on alternative sources, mainly the less-toxic non-hydride group-V sources. These are important for MOCVD and MOMBE. In terms of materials systems, the symposium covers both lattice-matched heterostructures, such as AlGaAs/GaAs and InGaAs/InP, pseudomorphic heterostructures, such as InGaAs/GaAs, and lattice-mismatched heterostructures, such as GaAs/Si, GaAs/InP, InP/GaAs, II-VI/GaAs, etc. In the characterization area, the techniques include RBS, TEM, X-ray, C-V, photoconductivity, Hall measurements, etc. In terms of device applications, the topics include MODFET, MESFET, laser, photodetector, solar cells, and integrated FET and laser, etc.

Tu, C.W. (California Univ., San Diego, La Jolla, CA (USA)); Mattera, W.D. (AT and T Bell Lab., Solid State Technology Center, Breinigsville, PA (US)); Gossard, A.C. (California Univ., Santa Barbara, CA (USA))

1989-01-01

72

Fabrication and characterization of nanostructured III-V thermoelectric materials  

NASA Astrophysics Data System (ADS)

Approximately two thirds of all fossil fuel used is lost as heat. Thermoelectric materials, which convert heat into electrical energy, may provide a solution to partially recover some of this lost energy. To date, most commercial thermoelectric materials are too inefficient to be a viable option for most waste heat applications. This research proposes to investigate the fabrication and characterization of nanostructured III-V semiconductor thermoelectric materials with the goal of increasing the performance of existing technology. In order to improve thermoelectric material efficiency, either the lattice thermal conductivity must be lowered or the thermoelectric power factor must be increased. This research will focus on the latter by modifying the density of states of the semiconductor material and studying the effect of quantum confinement on the material's thermoelectric properties. Using focused ion beam milling, nanostructured cantilevers are fabricated from single crystal wafers. An all around gate dielectric and electrode are deposited to create a depletion region along the outer core of the cantilever, thus creating an inner conductive core. The Seebeck coefficient can then be measured as a function of confinement by varying the gate voltage. This technique can be applied to various material systems to investigate the effects of confinement on their thermoelectric properties.

Novotny, Clint; Sharifi, Fred

2013-09-01

73

Trapping of free electrons in III-V superlattices  

NASA Astrophysics Data System (ADS)

Non-radiative trapping of electrons to deep traps in III-V superlattices is studied. An advancement in the technique of the calculation made it possible to avoid some approximation used in earlier calculation and to obtain a simpler, more precise, and clear results that extend applicability of the theory to narrow band gap materials and superlattices. It is shown that the non-radiative trapping rate in regular Huang-Rhys model has an activation temperature dependence with the activation energy equal to a portion of the phonon energy. The trapping to deep states can be accompanied with emission of phonons of different modes with different frequencies that can significantly reduce the activation energy. I argue that the role of superlattice phonons is relatively small except very low temperature where processes with their participation can have zero activation energy. A specific attention is paid in the paper to a qualitative explanation of every step of the calculation and details of the result. The theoretical results are used for understanding of recently measured temperature dependence of the minority carrier lifetime in InAs/GaSb superlattices.

Laikhtman, B.

2012-11-01

74

Feasibility of III–V on-silicon strain relaxed substrates  

Microsoft Academic Search

In this work we have investigated the feasibility of using ultrathin III–V films stuck on silicon as seed layers for subsequent epitaxial growths. The sticking is done by a thick viscous layer, which is assumed to act as an accommodating layer allowing the elastic relaxation of the initially strained III–V film. Two kinds of viscous layers have been employed: the

M. Kostrzewa; G. Grenet; P. Regreny; J. L. Leclercq; P. Perreau; E. Jalaguier; L. Di Cioccio; G. Hollinger

2005-01-01

75

Raman and Photoluminescence Studies of III-V Nitrides  

NASA Astrophysics Data System (ADS)

Raman scattering and photoluminescence (PL) studies of III-V nitrides are addressed focusing on recombination mechanisms in superlattics (SL), phonon lifetimes in crystals, and phonon dynamics. A detailed study of PL of GaN/AlGaN based SL is presented [1]. The dependence of the PL emission energy, linewidth, and intensity on temperature in the low temperature regime is consistent with recombination mechanisms involving bandtail states attributed to a small degree of interfacial disorder. The non-radiative activation energy of the PL agrees well with the value derived for the width of the tail-state distribution, indicating the role of some of the deep tail-states as trapping centers for the PL. Additionally, the effect of the polarization field on the PL characteristics is discussed. Raman studies of the lifetimes of phonon modes in GaN and AlN crystallites are also presented [2]. The analysis indicates that the phonon lifetimes in the III-V nitrides as well as in other semiconductors of the wurtzite structure fall into two main regimes: a relatively long time for the low-E2 mode and much shorter times (by approximately an order of magnitude) for the high-E2, E1(TO), A1(TO), and A1(LO) modes. The two time regimes are discussed in terms of the anharmonic decay mechanisms of the phonons in materials of wurtzite structure. The impact of impurities and dopants on the phonon decay time is analyzed as well. A Raman study of LO and TO quasi-mode frequencies as a function of the phonon- propagation angle in AlN is lastly presented [3]. The mode frequencies are analyzed in terms of the interaction of the polar phonons with the long-range electrostatic field. It is shown that the frequency of the LO quasi-mode exhibits a weaker angular dispersion than that of the TO quasi-mode. These frequency shifts, which are geometry dependent, have to be considered when analyzing other effects via Raman frequency such as stress and phonon-plasmon interaction. [1] L. Bergman, M. Dutta, M.A. Stroscio, S.M. Komirenko, R.J. Nemanich, C.J. Eiting, D.J.H. Lambert, H.K. Kwon, and R.D. Dupuis. Submitted to Appl. Phys. Lett. (1999). [2] L. Bergman, D. Alexson, P.L. Murphy, R.J. Nemanich, M. Dutta, M.A. Stroscio, C. Balkas, H. Shin, and R.F. Davis, Phys. Rev.B, 59, 12977 (1999). [3] L. Bergman M. Dutta, C. Balkas, R.F. Davis, J.A. Christman, D. Alexson, R.J. Nemanich, J. Appl. Phys. 85, 3535 (1999).

Bergman, Leah

2000-03-01

76

Type-I GaSb based single lateral mode diode ridge lasers operating at room temperature in 3.1-3.2 ?m spectral region  

NASA Astrophysics Data System (ADS)

Broad area type-I GaSb based diode lasers have recently exceeded 100 mW continuous wave room temperature powers in 3.1-3.2 ?m spectral region. Certain applications such as single frequency sources for spectroscopy and efficient coupling to single mode fiber require single lateral mode laser operation. We characterize and compare two types of lasers with similar structures and various ridge widths emitting at 3.1 and 3.2 ?m. We obtain 35 and 25 mW of continuous wave single lateral mode power from 8 and 13 ?m wide ridge lasers emitting at 3.1 and 3.2 ?m respectively. This constitutes a threefold improvement compared to the previous result. Both devices had ridges etched to the depth leaving approximately 300 nm of the top p-cladding in the areas outside the ridges. For 3.2 ?m emitting lasers the dielectric thickness was 220 nm while it was 510 nm for 3.1 ?m emitting lasers. Gain spectra were measured by Hakki- Paoli technique for various ridge widths. From gain spectra we extract differential gain and internal loss. We find that the internal loss in thin dielectric, 3.2 ?m emitting laser is about 14 cm-1 while it is 7 cm-1 in thick dielectric, 3.1 ?m emitting laser for the ridge widths of 13 and 8 ?m exhibiting single lateral mode operation respectively. Internal losses measured on broad area, 100 ?m wide lasers processed from the same materials are similar and around 6-7 cm-1. We discuss reasons for the internal loss increase with the aid of simulation of optical mode field and loss in our waveguide structures.

Tsvid, G.; Hosoda, T.; Chen, J.; Kipshidze, G.; Shterengas, L.; Frez, C.; Soibel, A.; Forouhar, S.; Belenky, G.

2011-02-01

77

Hydrogen incorporation into III-V nitrides during processing  

SciTech Connect

Hydrogen is readily incorporated into GaN and related alloys during wet and dry etching, chemical vapor deposition of dielectric overlayers, boiling in water and other process steps, in addition to its effects during MOCVD or MOMBE growth. The hydrogen is bound at defects or impurities and passivates their electrical activity. Reactivation occurs at 450-550{degrees}C, but evolution from the crystal requires much higher temperatures ({ge} 800{degrees}C).

Pearton, S.J.; Abernathy, C.R.; Vartuli, C.B. [Univ. of Florida, Gainesville, FL (United States)] [and others

1995-10-01

78

Precise Measurement of Charged Defects in III-V Compounds (Supplement 2).  

National Technical Information Service (NTIS)

Experimental methods and related theory which will permit the measurement of low concentrations of vacancies and other defects in III-V compound semiconductors are discussed. Once the nature of these defects has been determined, this information can be in...

J. F. Soest

1973-01-01

79

Optical Properties of III-V Semiconductor Nanostructures and Quantum Wells.  

National Technical Information Service (NTIS)

We have investigated the optoelectronic applications of interband and intersubband transitions in III-V semiconductors quantum wells and quantum dots. The research efforts included the investigation of intersubband transitions in GaN/AlGaN multiple quantu...

O. Manasreh

2006-01-01

80

Self-aligning planarization and passivation for integration applications in III-V semiconductor devices  

Microsoft Academic Search

This work reports an easy planarization and passivation approach for the integration of III-V semiconductor devices. Vertically etched III-V semiconductor devices typically require sidewall passivation to suppress leakage currents and planarization of the passivation material for metal interconnection and device integration. It is, however, challenging to planarize all devices at once. This technique offers wafer-scale passivation and planarization that is

Hilmi Volkan Demir; Jun-Fei Zheng; Vijit A. Sabnis; Onur Fidaner; Jesper Hanberg; James S. Harris; David A. B. Miller

2005-01-01

81

Phonons, electron-phonon interactions, and phonon-phonon interactions in III-V nitrides  

Microsoft Academic Search

Fundamental properties of phonons in III-V nitrides are examined with a view toward understanding processes important in the operation of III-V nitride devices. Firstly, confined, interface and propagating modes in wurtzite quantum wells are described in terms of Loudon's model for uniaxial semiconductors and the dielectric continuum model. Basic properties of the phonon modes and carrier-phonon interactions are considered in

Leah Bergman; Mitra Dutta; Ki Wook Kim; Paul G. Klemens; Serguei M. Komirenko; Michael A. Stroscio

2000-01-01

82

Optoelectronic III-V heterostructures on Si substrates  

NASA Astrophysics Data System (ADS)

The results of a three-year program to investigate the epitaxial growth of the 3-5 semiconductors, particularly the InGaAsP/InP materials system, on Si substrates is presented. The heterostructures were grown by gas-source molecular beam epitaxy (GSMBE) and were designed for applications in optoelectronics. With regard to growth of InP and InGaAsP alloys on Si, the research program was successful in reducing misfit dislocations and stacking faults resulting from the 8 percent lattice mismatch between InP and Si. A strained layer superlattice of In(x)Ga(1-x)P/In(y)Ga(1-y)P (X not equal Y) was used as a buffer layer. The use of InGaP as buffer layers led to extensive development, in parallel with the InP-on-Si work, of InGaP layers by GSMBE. The Schottky barrier energies for both n-type and p-type materials were measured for the first time for the wide bandgap alloys InGaP and InGaAlP when lattice matched to GaAs.

Robinson, Gary Y.

1992-09-01

83

Materials and Device Aspects of III-V 3D Transistors  

NASA Astrophysics Data System (ADS)

Recently, III-V MOSFETs with high drain currents (Ids>1mA/?m) and high transconductances (gm>1mS/?m) have been achieved at sub-micron channel lengths (Lch), thanks to the better understanding and significant improvement in high-k/III-V interfaces. However, to realize a III-V FET at beyond 14nm technology node, one major challenge is how to effectively control the short channel effects (SCE). Due to the higher permittivity and lower bandgap of the channel materials, III-V MOSFETs are more susceptible to SCE than its Si counterpart. The scaling of planar devices stops at around 150nm Lch. The dramatic increase in DIBL beyond 150nm indicates severe impact from 2D electrostatics. Therefore, the introduction of 3-dimensonal (3D) structures to the fabrication of sub-100nm III-V FETs is necessary. In this talk, we will review the materials and device aspects of III-V 3D transistors developed very recently [1-3]. [4pt] [1] Y. Q. Wu et al. IEDM Tech. Dig. 331 (2009).[0pt] [2] M. Radosavljevic et al., IEDM Tech. Dig. 126 (2010).[0pt] [3] J. J. Gu et al. IEDM Tech Dig. 2011 (in press).

Ye, Peide

2012-02-01

84

Magnetic and magnetotransport investigations of manganese doped ferromagnetic II-VI and III-V diluted magnetic semiconductors (DMS)  

NASA Astrophysics Data System (ADS)

This dissertation describes efforts to study and understand magnetic and electrical transport properties of diluted magnetic semiconductors (DMS), particularly the role of manganese (Mn) in II-VI and III-V DMS. It is divided into two chapters; both focused on ferromagnetism, collective alignment of spins, and in the III-V system how this affects transport properties; understanding is vital for semiconductor spintronics applications. All samples discussed were grown by Molecular Beam Epitaxy (MBE). First, magnetization and relevant optical measurements of type-II self-assembled columnar quantum dots, namely (ZnMn)Te dots embedded in a ZnSe matrix are presented. Results for dots containing Mn ions are compared with results for ZnTe dots. The observation of apparent long-range magnetic ordering that is persistent up to high temperatures is discussed, and future research directions are suggested based on these results. Second, epitaxial layers of GaSb doped with Mn, namely Ga1-xMn xSb random alloys, are investigated by detailed magnetization and magneto-transport studies. The Curie temperature in this material system is quite low (< 25 K), but it exhibits very interesting behavior. A unique temperature dependence of the anomalous Hall effect (AHE) is observed and the underlying physics is explained by a simple theoretical model based on the role of impurity bands. Metal-insulator-semiconductor structures have also been studied and gating of the carrier density by this method has shown a change in the sign of the AHE. This result is not fully understood.

Eginligil, Mustafa

85

Predicted band structures of III-V semiconductors in the wurtzite phase  

SciTech Connect

While non-nitride III-V semiconductors typically have a zinc-blende structure, they may also form wurtzite crystals under pressure or when grown as nanowhiskers. This makes electronic structure calculation difficult since the band structures of wurtzite III-V semiconductors are poorly characterized. We have calculated the electronic band structure for nine III-V semiconductors in the wurtzite phase using transferable empirical pseudopotentials including spin-orbit coupling. We find that all the materials have direct gaps. Our results differ significantly from earlier ab initio calculations, and where experimental results are available (InP, InAs, and GaAs) our calculated band gaps are in good agreement. We tabulate energies, effective masses, and linear and cubic Dresselhaus zero-field spin-splitting coefficients for the zone-center states. The large zero-field spin-splitting coefficients we find may facilitate the development of spin-based devices.

De, A.; Pryor, Craig E. [Department of Physics and Astronomy and Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242 (United States)

2010-04-15

86

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

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

87

Silicon MCM substrates for integration of III-V photonic devices and CMOS IC`s  

SciTech Connect

The progress made in advanced packaging development at Sandia National Laboratories for integration of III-V photonic devices and CMOS IC`s on Silicon MCM substrates for planar aid stacked applications will be reported. Studies to characterize precision alignment techniques using solder attach materials compatible with both silicon IC`s and III-V devices will be discussed. Examples of the use of back-side alignment and IR through-wafer inspection will be shown along with the extra processing steps that are used. Under bump metallurgy considerations are also addressed.

Seigal, P.; Carson, R.; Flores, R.; Rose, B.

1993-07-01

88

Performance of CPV system using three types of III-V multi-junction solar cells  

NASA Astrophysics Data System (ADS)

Performance of III-V multi-junction solar cells depends on spectral conditions according to which junction limits the photocurrent. Specifically, the response of concentrating multi-junction solar cells depends on the illumination at the cell surface. Because the illumination condition depends on alignment, it is important to characterize the CPV performance not only for a mono-module but also for a system or an array. In this paper the spectral effect on the CPV system and the mono-module consisting of III-V multi-junction solar cells from three different manufactures will be discussed.

Hashimoto, Jun; Kurtz, Sarah; Sakurai, Keiichiro; Muller, Matthew; Otani, Kenji

2012-10-01

89

Silicon-photonics light source realized by III-V/Si-grating-mirror laser  

NASA Astrophysics Data System (ADS)

A III-V/Si vertical-cavity in-plane-emitting laser structure is suggested and numerically investigated. This hybrid laser consists of a distributed Bragg reflector, a III-V active region, and a high-index-contrast grating (HCG) connected to an in-plane output waveguide. The HCG and the output waveguide are made in the Si layer of a silicon-on-insulator wafer by using Si-electronics-compatible processing. The HCG works as a highly-reflective mirror for vertical resonance and at the same time routes light to the in-plane output waveguide. Numerical simulations show superior performance compared to existing silicon light sources.

Chung, Il-Sug; Mørk, Jesper

2010-10-01

90

Universal mechanism for ion-induced nanostructure formation on III-V compound semiconductor surfaces  

SciTech Connect

We have examined the formation of nanostructures on ion-irradiated compound semiconductor surfaces. We computed the ion doses needed to fully deplete group V elements from the surfaces. These group V depletion doses are in good agreement with the measured threshold ion doses for nucleation of group III-rich nanostructures on a wide variety of III-V compound semiconductor surfaces. Since the group V depletion doses decrease with increasing sputtering yield, these results suggest a universal nanostructure formation mechanism which depends upon the total sputtering yield of each III-V compound.

Kang, M.; Wu, J. H.; Huang, S.; Warren, M. V.; Jiang, Y.; Robb, E. A.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

2012-08-20

91

Impact of weak Fermi-level pinning on the correct interpretation of III-V MOS CV and GV characteristics  

Microsoft Academic Search

The commonly encountered frequency dispersion and distorted behavior of GaAs and III-V MOS C-V and G-V is clarified by using MOS interface state theory. The relation of the C-V behavior with Fermi-level pinning of III-V MOS is explained. It is shown why it is difficult to quantify the interface state density using the conductance method for III-V MOS. A qualitative

K. Martens; W. Wang; K. De Keersmaecker; G. Borghs; G. Groeseneken; H. Maes

2007-01-01

92

Study of the Electronic Surface States of III-V Compounds.  

National Technical Information Service (NTIS)

At the time of the last semiannual report, we had stated the development of the unified defect model for Schottky-barrier formation. Since then, work has proceeded to further explain the nature and the source of states at the oxide:III-V interface and met...

W. E. Spicer I. Lindau

1980-01-01

93

Optical fingerprints of Y2 ordering in III–V ternary semiconductor alloys  

NASA Astrophysics Data System (ADS)

In this paper, we report the Y2 ordering induced changes in the crystal field splitting, spin–orbit splitting and band gap for AlxGa1?xAs, GaxIn1?xAs, GaxIn1?xP, GaAsxSb1?x and InPxSb1?x using first-principles calculations. These values and the valence band splittings E12, E13 for these materials are provided as a function of the ordering parameter ?. The trends of these properties among materials are explained. The optical fingerprints of Y2 ordering are then compared with those of other available structures and the experimental data.

Chen, Dongguo; Ravindra, N. M.

2013-06-01

94

Bismuth containing III-V quaternary alloy InGaAsBi grown by MBE  

NASA Astrophysics Data System (ADS)

InGaAsBi epilayers were created on InP substrates by molecular beam epitaxy for the first time. The high crystalline quality of the InGaAsBi epilayer with smooth interface was confirmed by high resolution X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.

Feng, G.; Oe, K.; Yoshimoto, M.

2006-09-01

95

Growth Mechanism of Self-Catalyzed Group III-V Nanowires  

PubMed Central

Group III?V nanowires offer the exciting possibility of epitaxial growth on a wide variety of substrates, most importantly silicon. To ensure compatibility with Si technology, catalyst-free growth schemes are of particular relevance, to avoid impurities from the catalysts. While this type of growth is well-documented and some aspects are described, no detailed understanding of the nucleation and the growth mechanism has been developed. By combining a series of growth experiments using metal?organic vapor phase epitaxy, as well as detailed in situ surface imaging and spectroscopy, we gain deeper insight into nucleation and growth of self-seeded III?V nanowires. By this mechanism most work available in literature concerning this field can be described.

2010-01-01

96

The metal grating design of plasmonic hybrid III-V/Si evanescent lasers.  

PubMed

A hybrid III-V/silicon laser design with a metal grating layer inserted in between is proposed and numerically studied. The metal grating layer is buried in a silicon ridge waveguide surrounded by silicon dioxide, and its structural parameters such as periodicity, width and depth can be varied for optimization purpose. The plasmonic effect originated from the grating layer can manage optical fields between III-V and silicon layers in hopes of dimension reduction. The substrate is planarized to minimize the bonding failure. A numerical algorithm with various combinations of metal grating and waveguide structural parameters was created and the optimal design with 730 nm grating period and 600 nm of buried waveguide ridge height was obtained by minimizing the corresponding laser threshold. With top AlInGaAs quantum wells and optimized design of hybrid metal/silicon waveguide, a 0.6 ?m-1 threshold gain can be achieved. PMID:24105566

Hsu, Min-Hsiang; Lin, Chien-Chung; Kuo, Hao-Chung

2013-08-26

97

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

NASA Astrophysics Data System (ADS)

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.

Castelletto, S.; Parker, A.

2013-09-01

98

Electrochemical pore formation mechanism in III-V crystals (Part II)  

SciTech Connect

Chemical and electrical processes developing at the semiconductor-electrolyte interface under conditions of anodic polarization were analyzed. It was shown that dense chemisorption coatings are formed on the surface of III-V crystals at voltages of pore formation onset, and a degenerate inversion layer is formed on the semiconductor side. In this case, a drop of the largest part of the applied voltage in the adsorption layer creates the prerequisites for nucleophilic substitution reactions involving chemisorbed anions and coordination-saturated atoms under the crystal surface. The mechanisms of these reactions were considered as applied to sphalerite-structured crystals. The results of experimental studies of the structures and compositions of porous layers in III-V crystals formed in various electrolytes at various polarization voltages are explained on the basis of the obtained concepts.

Ulin, V. P.; Konnikov, S. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)], E-mail: konnikov@mail.ioffe.ru

2007-07-15

99

Thin-Film III V Photodetectors Integrated on Silicon-on-Insulator Photonic ICs  

NASA Astrophysics Data System (ADS)

We critically assess recent progress in the integration of near-infrared photodetectors onto nanophotonic silicon-on-insulator (SOI) waveguide circuits. Integration of thin-film InGaAs photodetectors is studied in detail. This method consists of bonding unprocessed III V dies onto the SOI substrate using an intermediate adhesive layer. Both benzocyclobutene and spin-on glass are studied and compared as bonding agents. After the removal of the III V substrate, the thin-film detectors are fabricated using wafer-scale-compatible processes and lithographically aligned to the underlying SOI waveguides. The process is compatible with the fabrication of InP/InGaAsP laser diodes on SOI. A new design of an evanescently coupled metal semiconductor metal detector is proposed, proving the ability to obtain compact and highly efficient integrated InGaAs photodetectors.

Brouckaert, Joost; Roelkens, Gunther; van Thourhout, Dries; Baets, Roel

2007-04-01

100

III-V silicon heterogeneous integration for integrated transmitters and receivers  

NASA Astrophysics Data System (ADS)

Silicon is excellent material for realizing compact nanophotonic ICs operating at wavelengths in the telecom range. Moreover, the desired circuits can be realized with the most advanced equipment available, used also for the fabrication of high-end electronic circuits. Efficient light emission and amplification directly from silicon remains a bottleneck however. Therefore, we developed an alternative approach, based on the heterogeneous integration of III-V epitaxial material and silicon nanophotonic circuits. Following fabrication and planarization of the latter, small unprocessed dies of InP-based epitaxial material are bonded on top. Next, the substrate of these dies is removed down to an etch stop layer. Finally the desired active optoelectronic devices are processed in the remaining III-V layers using waferscale processes. The critical alignment between the sources and the underlying nanophotonic circuits is ensured through accurate lithography. In this paper we review some recent devices fabricated through this integration process.

Van Thourhout, D.; Van Campenhout, J.; Roelkens, G.; Brouckaert, J.; Baets, R.

2008-03-01

101

Noise performance of bound-to-miniband transition III-V quantum-well infrared photodetectors  

Microsoft Academic Search

Dark current noise measurements between 10 and 10(exp 5) Hz were carried out at T = 77 on three different types of III-V quantum-well infrared photodetectors designed for 8-12 micrometer IR detection. These devices have superlattice barriers leading to miniband transport in the extended conduction band. For frequencies between 10(exp 2) and 10(exp 4) Hz, noise plateau levels stemming from

Daniel C. Wang; Gijs Bosman; Yeng H. Wang; Sheng S. Li

1995-01-01

102

Noise performance of bound-to-miniband transition III-V quantum-well infrared photodetectors  

Microsoft Academic Search

Dark current noise measurements between 10 and 105 Hz were carried out at T=77 K on three different types of III-V quantum-well infrared photodetectors designed for 8–12 ?m IR detection. These devices have superlattice barriers leading to miniband transport in the extended conduction band. For frequencies between 102 and 104 Hz, noise plateau levels stemming from the trapping and detrapping

Daniel C. Wang; Gijs Bosman; Yeng H. Wang; Sheng S. Li

1995-01-01

103

Density-functional calculations of carbon doping in III-V compound semiconductors  

Microsoft Academic Search

This article reports the results of investigations based on local-density-functional theory into the relative formation energies for single substitutional carbon atoms in nine III-V compound semiconductors. The calculations are performed using a supercell formalism derived from the AIMPRO real-space cluster method. Only a very slight trend is discernible down the periodic table. When a metal atom is replaced with carbon,

C. D. Latham; R. Jones; S. Öberg; P. R. Briddon

2001-01-01

104

Room temperature ferromagnetism in III–V and II–IV–V 2 dilute magnetic semiconductors  

Microsoft Academic Search

A new class of ferromagnets—dilute magnetic semiconductors (DMS) based on III–V materials (e.g. In1-xMnxAs or Ga1-xMnxAs)—which are both semiconducting and ferromagnetic (FM) at low temperature, have attracted a great deal of attention (as working media for spintronics) following the discovery of ferromagnetism in Ga1-xMnxAs. However, practical spintronics applications of these DMS are severely limited by the fact that they are

V. G. Storchak; D. G. Eshchenko; H. Luetkens; E. Morenzoni; R. L. Lichti; S. F. Marenkin; O. N. Pashkova; J. H. Brewer

2006-01-01

105

Room temperature ferromagnetism in III V and II IV V2 dilute magnetic semiconductors  

Microsoft Academic Search

A new class of ferromagnets---dilute magnetic semiconductors (DMS) based on III V materials (e.g. In1-xMnAs or Ga1-xMnAs)---which are both semiconducting and ferromagnetic (FM) at low temperature, have attracted a great deal of attention (as working media for spintronics) following the discovery of ferromagnetism in Ga1-xMnAs. However, practical spintronics applications of these DMS are severely limited by the fact that they

V. G. Storchak; D. G. Eshchenko; H. Luetkens; E. Morenzoni; R. L. Lichti; S. F. Marenkin; O. N. Pashkova; J. H. Brewer

2006-01-01

106

Studies of the III-V compounds in the megabar regime. Technical progress report  

SciTech Connect

In this project we develop techniques for making high pressure measurements (x-ray diffraction and optical measurements) on samples in the multimegabar regime and we make systematic studies of the crystal structure of III-V compounds and other materials as a function of pressure with the broad objective of providing experimental data over a broad range of coordination number and interatomic spacing which can play a leading role in the testing and development of theoretical models of binding.

Ruoff, A.L.

1992-09-01

107

Studies of the III-V compounds in the megabar regime  

SciTech Connect

In this project we develop techniques for making high pressure measurements (x-ray diffraction and optical measurements) on samples in the multimegabar regime and we make systematic studies of the crystal structure of III-V compounds and other materials as a function of pressure with the broad objective of providing experimental data over a broad range of coordination number and interatomic spacing which can play a leading role in the testing and development of theoretical models of binding.

Ruoff, A.L.

1992-01-01

108

Update on III-V antimonide-based superlattice FPA development and material characterization  

Microsoft Academic Search

Much progress has been made in the past 2 years in developing III-V antimonide-based superlattice infrared detectors and focal plane arrays (FPAs). In the area of detector material growth by molecular beam epitaxy, the wafer foundry group, helped by government-trusted entities and other partnering institutions, has leapfrogged many years of R&D effort to become the premier detector wafer supplier. The

Lucy Zheng; Meimei Tidrow; Sumith Bandara; Leslie Aitcheson; Tiffany Shih

2011-01-01

109

Environmental health and safety (EHS) issues in III-V solar cell manufacturing  

Microsoft Academic Search

Large-scale manufacturing of III-V high-performance photovoltaics will require close attention to environmental, health and safety (EHS) issues. This paper reviews such issues and highlights challenges resulting from using large quantities of arsine, phosphine, and hydrogen in current MOCVD. These gases can be used safely when multi-layers of protection are implemented; these are discussed herein. The cost related to risk management

Vasilis M. Fthenakis; B. Bowerman

2003-01-01

110

Effect of dopant atoms on the roughness of III-V semiconductor cleavage surfaces  

NASA Astrophysics Data System (ADS)

We demonstrate that the presence of dopant atoms influences the roughness, morphology, and optical mirror properties of III-V semiconductor (110) cleavage surfaces. High concentrations of Te dopant atoms in GaAs lead to macroscopically curvatured (110) cleavage surfaces with high step concentrations. This ``glass-like'' fracture behavior is explained by the ``lattice superdilation phenomenon'' induced by high concentrations of Te dopant atoms in GaAs.

Quadbeck, P.; Ebert, Ph.; Urban, K.; Gebauer, J.; Krause-Rehberg, R.

2000-01-01

111

III-V membrane structures for tunable Fabry-Perot filters and sensor applications  

Microsoft Academic Search

The introduction of III-V semiconductor technology in the field of micromechanics allowed the development of novel electronic and optoelectronic devices, in particular comprising actuator and sensor applications. In this work we report on InP-based micromachined Fabry-Perot microcavity structures for use as tunable optical filter application in telecommunication systems operating in the 1.55 ?m wavelength regime. Various approaches for the filter

H. L. Hartnagel; J. Pfeiffer; K. Mutamba; J. Peerlings; R. Riemenschneider; P. Meissner

1998-01-01

112

Recent progress in ?-doping of III–V semiconductors grown by metal organic vapour phase epitaxy  

Microsoft Academic Search

In this article, ?-doping of III–V semiconductors (III–Vs) grown by metal organic vapour phase epitaxy (MOVPE) is reviewed in respect to the parametric dependencies of ?-doping concentrations, the spatial confinement of carriers and dopants in ?-doped layers, and applications of MOVPE-grown ?-doped structures to electronic and opto-electronic devices.The use of molecular doping precursors determines that ?-doping in MOVPE is more

G. Li; C. Jagadish

1997-01-01

113

Novel planarization and passivation in the integration of III-V semiconductor devices  

Microsoft Academic Search

III-V semiconductor devices typically use structures grown layer-by-layer and require passivation of sidewalls by vertical etching to reduce leakage current. The passivation is conventionally achieved by sealing the sidewalls using polymer and the polymer needs to be planarized by polymer etch-back method to device top for metal interconnection. It is very challenging to achieve perfect planarization needed for sidewalls of

Jun-Fei Zheng; Peter J. Hanberg; Hilmi Volkan Demir; Vijit A. Sabnis; Onur Fidaner; James S. Harris Jr.; David A. B. Miller

2004-01-01

114

III-V\\/Silicon-on-Insulator Nanophotonic Cavities for Optical Network-on-Chip  

Microsoft Academic Search

We review some opto-electronic devices based on the III-V\\/SOI heterogeneous integration platform, including lasers, modulators, wavelength converters, and photo-detectors. All of them are critical components for future on-chip interconnect and optical network-on-chip. The footprints of such devices are kept small by employing micro-cavity based structures. We give an overview of the device performances. The advantages over the all-silicon based devices

Liu Liu; Günther Roelkens; Joris Van Campenhout; Joost Brouckaert; Dries Van Thourhout; Roel Baets

115

Confined phonons and phonon-mode properties of III–V nitrides with wurtzite crystal structure  

Microsoft Academic Search

Stimulated by the recent interest in the use of nitride-based III–V wurtzite structures for optoelectronic and electronic devices, this paper reports on the application of the Loudon model for uniaxial crystals to derive the Fröhlich interaction Hamiltonian as well as the electron–optical-phonon scattering rate in wurtzite crystals. This paper also presents experimental analyses of the mode behavior of phonons in

D. Alexson; Leah Bergman; Mitra Dutta; K. W Kim; S. Komirenko; Robert J Nemanich; B. C Lee; Michael A Stroscio; Segi Yu

1999-01-01

116

New and unified model for Schottky barrier and III--V insulator interface states formation  

Microsoft Academic Search

For n- and p-doped III--V compounds, Fermi-level pinning and accompanying phenomena of the (110) cleavage surface have been studied using photoemission at h..nu..< or approx. =300 eV (so that core as well as valence band levels could be studied). Both the clean surfaces and the changes produced, as metals or oxygen are added to those surfaces in submonolayer quantities, have

W. E. Spicer; P. W. Chye; P. R. Skeath; C. Y. Su; I. Lindau

1979-01-01

117

III-V quantum light source and cavity-QED on Silicon  

PubMed Central

Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers of quantum information and can be exploited for linear optics quantum information processing. Scale-up requires miniaturisation of the waveguide circuit and multiple single photon sources. Silicon photonics, driven by the incentive of optical interconnects is a highly promising platform for the passive optical components, but integrated light sources are limited by silicon's indirect band-gap. III–V semiconductor quantum-dots, on the other hand, are proven quantum emitters. Here we demonstrate single-photon emission from quantum-dots coupled to photonic crystal nanocavities fabricated from III–V material grown directly on silicon substrates. The high quality of the III–V material and photonic structures is emphasized by observation of the strong-coupling regime. This work opens-up the advantages of silicon photonics to the integration and scale-up of solid-state quantum optical systems.

Luxmoore, I. J.; Toro, R.; Pozo-Zamudio, O. Del; Wasley, N. A.; Chekhovich, E. A.; Sanchez, A. M.; Beanland, R.; Fox, A. M.; Skolnick, M. S.; Liu, H. Y.; Tartakovskii, A. I.

2013-01-01

118

Growth and in vivo STM of III-V Compound Semiconductors  

NASA Astrophysics Data System (ADS)

A combinational machine (MBSTM) capable of III-V molecular beam epitaxial deposition whilst performing scanning tunnelling microscopy (STM) is described. Epitaxial deposition `under the STM tip' heralds a new world of discovery in the field of III-V epitaxial growth. What is fashionably referred to as in vivo STM offers the potential to observe a medley of speculated transitions that until now have been glimpsed frozen in time. It is potentially possible to observe in real time and on the atomic scale GaAs surface processes such as reconstruction transformations, monolayer steps sweeping across the growth surface and, for eg (001) orientation, the structure evolution during heteroepitaxial InAs deposition through Stranski-Krastanow (S-K) wetting layer formation and quantum dot (QD) growth. To this end, an overview of the machine is given, detailing the crucial composition of the MBSTM chamber. Key aspects related to tip preparation, temperature regulation and deposition inception are detailed providing a picture of the future of III-V epitaxial research.

Bastiman, F.; Cullis, A. G.; Hopkinson, M.; Green, M.

119

Growth and optical properties of axial hybrid III-V/silicon nanowires  

NASA Astrophysics Data System (ADS)

Hybrid silicon nanowires with an integrated light-emitting segment can significantly advance nanoelectronics and nanophotonics. They would combine transport and optical characteristics in a nanoscale device, which can operate in the fundamental single-electron and single-photon regime. III-V materials, such as direct bandgap gallium arsenide, are excellent candidates for such optical segments. However, interfacing them with silicon during crystal growth is a major challenge, because of the lattice mismatch, different expansion coefficients and the formation of antiphase boundaries. Here we demonstrate a silicon nanowire with an integrated gallium-arsenide segment. We precisely control the catalyst composition and surface chemistry to obtain dislocation-free interfaces. The integration of gallium arsenide of high optical quality with silicon is enabled by short gallium phosphide buffers. We anticipate that such hybrid silicon/III-V nanowires open practical routes for quantum information devices, where for instance electronic and photonic quantum bits are manipulated in a III-V segment and stored in a silicon section.

Hocevar, Moïra; Immink, George; Verheijen, Marcel; Akopian, Nika; Zwiller, Val; Kouwenhoven, Leo; Bakkers, Erik

2012-12-01

120

Growth and optical properties of axial hybrid III-V/silicon nanowires.  

PubMed

Hybrid silicon nanowires with an integrated light-emitting segment can significantly advance nanoelectronics and nanophotonics. They would combine transport and optical characteristics in a nanoscale device, which can operate in the fundamental single-electron and single-photon regime. III-V materials, such as direct bandgap gallium arsenide, are excellent candidates for such optical segments. However, interfacing them with silicon during crystal growth is a major challenge, because of the lattice mismatch, different expansion coefficients and the formation of antiphase boundaries. Here we demonstrate a silicon nanowire with an integrated gallium-arsenide segment. We precisely control the catalyst composition and surface chemistry to obtain dislocation-free interfaces. The integration of gallium arsenide of high optical quality with silicon is enabled by short gallium phosphide buffers. We anticipate that such hybrid silicon/III-V nanowires open practical routes for quantum information devices, where for instance electronic and photonic quantum bits are manipulated in a III-V segment and stored in a silicon section. PMID:23232396

Hocevar, Moïra; Immink, George; Verheijen, Marcel; Akopian, Nika; Zwiller, Val; Kouwenhoven, Leo; Bakkers, Erik

2012-01-01

121

Analytical and Computer-Aided Models for Iii-V Compound Semiconductor Devices.  

NASA Astrophysics Data System (ADS)

The objective of this research is to develop analytical and computer-aided models for III-V compound semiconductor devices. In this work, we have developed analytical models for uniformly-doped HEMTs as well as delta-doped HEMTs and numerical models for homojunction as well as heterojunction III-V compound semiconductor devices, including the MESFET, HEMT, and HBT. For analytical modeling, we started by deriving an analytical nonlinear charge control model, in which the nonlinear dependence of the effective offset distance of the 2-DEG from heterojunction on externally applied bias is accurately described. For numerical modeling, we developed a general purpose two-dimensional semiconductor device analysis program based on a novel finite-element discretization method. These models, which could be used as design and characterization tools, provide a better understanding of device physics and a basis for further development of sophisticated analytical and computer-aided models required for accurate performance evaluation of high-frequency and high-speed VLSI devices and circuits based on state-of-the-art III-V compound semiconductor technologies for full realization of their potentials.

Shey, An-Jui

122

Theoretical consideration of III-V nanowire/Si triple-junction solar cells  

NASA Astrophysics Data System (ADS)

In this paper, we report theoretical consideration and simulation of a proposed III-V nanowire (NW)/Si triple-junction solar cell. The cell consists of two axially connected III-V NW subcells that are grown and electrically integrated on an active Si substrate. The optical properties of the cell are thoroughly analyzed by using the finite-difference time-domain method. It is found that NW subcells with optimized geometry have high absorption throughout their absorption region. Meanwhile, beyond the absorption edge of the top and middle NW subcells, the NWs act as an efficient antireflection coating for the bottom Si subcell due to the formation of an optical cavity within the NW layer. The physics responsible for the enhanced light harvesting process is qualitatively explained through modal analysis. In addition, we have shown that the condition of current matching in a III-V NW/Si multi-junction can be fulfilled by adjusting the diameter of the NWs. In order to study the current-voltage characteristics of the proposed cell, the optical generation profiles under AM1.5G illumination are incorporated into an electrical modeling. Our optoelectrical simulations indicate that, with an excellent current matching between subcells, the performance of the proposed structure is comparable with state-of-the-art multi-junction cells. The results presented here indicate that semiconductor NWs may provide a promising route toward high efficiency multi-junction solar cells.

Wen, Long; Li, Xinhua; Zhao, Zhifei; Bu, Shaojiang; Zeng, XueSong; Huang, Jin-hua; Wang, Yuqi

2012-12-01

123

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

NASA Astrophysics Data System (ADS)

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.

Ouyang, Lu

124

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

NASA Astrophysics Data System (ADS)

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.

Araki, Kenji; Nagai, Hirokazu; Tamura, Kazuyuki

2012-10-01

125

Empirical modeling of low-frequency dispersive effects due to traps and thermal phenomena in III-V FET's  

Microsoft Academic Search

The modeling of low-frequency dispersive effects due to surface state densities, deep level traps and thermal phenomena plays an important role in the large-signal performance prediction of III-V FET's. This paper describes an empirical modeling approach to accurately predict deviations between static and dynamic drain current characteristics caused by dispersive effects in III-V devices operating at microwave frequencies. It is

Fabio Filicori; Giorgio Vannini; A. Santarelli; A. M. Sanchez; A. Tazon; Y. Newport

1995-01-01

126

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

SciTech Connect

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.

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

2006-01-01

127

Formation of III-V-on-insulator structures on Si by direct wafer bonding  

NASA Astrophysics Data System (ADS)

We have studied the formation of III-V-compound-semiconductors-on-insulator (III-V-OI) structures with thin buried oxide (BOX) layers on Si wafers by using developed direct wafer bonding (DWB). In order to realize III-V-OI MOSFETs with ultrathin body and extremely thin body (ETB) InGaAs-OI channel layers and ultrathin BOX layers, we have developed an electron-cyclotron resonance (ECR) O2 plasma-assisted DWB process with ECR sputtered SiO2 BOX layers and a DWB process based on atomic-layer-deposition Al2O3 (ALD-Al2O3) BOX layers. It is essential to suppress micro-void generation during wafer bonding process to achieve excellent wafer bonding. We have found that major causes of micro-void generation in DWB processes with ECR-SiO2 and ALD-Al2O3 BOX layers are desorption of Ar and H2O gas, respectively. In order to suppress micro-void generation in the ECR-SiO2 BOX layers, it is effective to introduce the outgas process before bonding wafers. On the other hand, it is a possible solution for suppressing micro-void generation in the ALD-Al2O3 BOX layers to increase the deposition temperature of the ALD-Al2O3 BOX layers. It is also another possible solution to deposit ALD-Al2O3 BOX layers on thermally oxidized SiO2 layers, which can absorb the desorption gas from ALD-Al2O3 BOX layers.

Yokoyama, Masafumi; Iida, Ryo; Ikku, Yuki; Kim, Sanghyeon; Takagi, Hideki; Yasuda, Tetsuji; Yamada, Hisashi; Ichikawa, Osamu; Fukuhara, Noboru; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

2013-09-01

128

Average energy gap in III-V semiconductors and ternary compounds  

Microsoft Academic Search

The average energy gap Eg of IV and III-V type semiconductors is calculated from the E0 and E2 transition energies in relation to the 'one gap Penn model' (1962) and from epsilon 2(E).Eg is given by: Eg=M0\\/( epsilon (0)-1) where M0=(2\\/ pi ) integral 0infinity epsilon 2(E)dE. Taking into account Eg given by Phillips (1970) as Eg2=Eh2+C2, the variation of

C. Ance

1979-01-01

129

Zinc diffusion in III-V semiconductors using a cubic-zirconia protection layer  

Microsoft Academic Search

Zinc was diffused into GaAs, Al0.38Ga0.62As, and GaAs0.6P0.4 using a 2000–3000-A?-thick yttria-stabilized cubic-zirconia (YSZ) protection layer to produce planar p-n junctions. The YSZ layer greatly reduced thermal decomposition of the semiconductor while allowing zinc to diffuse into the III-V semiconductors. The diffusion depth showed a square-root-of-time dependence for all samples protected with YSZ. Characterization of the GaAs diffused with the

J. E. Bisberg; A. K. Chin; F. P. Dabkowski

1990-01-01

130

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

SciTech Connect

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.

Wendler, E. [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Wendler, L. [Anna-Siemsen-Strasse 66, D-07745 Jena (Germany)

2012-05-07

131

Quantum-structured III-V energy harvesting devices: pathways to ultra-high conversion efficiencies  

NASA Astrophysics Data System (ADS)

Quantum-structured photovoltaic devices incorporating III-V quantum wells or quantum dots have the potential to dramatically increase the performance of energy harvesting devices. In this work, the dark current of high-voltage InGaAs quantum well structures is characterized, and the underlying saturation current density analyzed as a function of effective energy gap. Analysis of the current-voltage characteristics suggests that these advanced quantum well device structures are operating in a regime of suppressed radiative recombination. High-voltage output from quantum-structured energy harvesting devices, coupled with advances in the field of light trapping, provides a pathway for achieving ultra-high conversion efficiencies.

Welser, Roger E.; Sood, Ashok K.; Dhar, Nibir K.; Wijewarnasuriya, Priyalal S.

2012-05-01

132

Heralded single-photon source in a III-V photonic crystal.  

PubMed

In this Letter we demonstrate heralded single-photon generation in a III-V semiconductor photonic crystal platform through spontaneous four-wave mixing. We achieve a high brightness of 3.4×10(7) pairs·s(-1) nm(-1) W(-1) facilitated through dispersion engineering and the suppression of two-photon absorption in the gallium indium phosphide material. Photon pairs are generated with a coincidence-to-accidental ratio over 60 and a low g(2) (0) of 0.06 proving nonclassical operation in the single photon regime. PMID:23455253

Clark, Alex S; Husko, Chad; Collins, Matthew J; Lehoucq, Gaelle; Xavier, Stéphane; De Rossi, Alfredo; Combrié, Sylvain; Xiong, Chunle; Eggleton, Benjamin J

2013-03-01

133

Ultraviolet photosulfidation of III-V compound semiconductors: A new approach to surface passivation  

SciTech Connect

A new passivation technique for III-V compound semiconductors based on ultraviolet photolysis of elemental sulfur vapor has been developed. Photosulfidation produces a greater increase in the photoluminescence intensity from GaAs samples than that produced by conventional (NH[sub 4])[sub 2]S dip treatments and is more photostable than the conventional wet process. X-ray photoelectron spectroscopy of the photosulfided GaAs surfaces indicate formation of a surface sulfide rather than the disulfide characteristic of the (NH[sub 4])[sub 2]S process.

Ashby, C.I.H.; Zavadil, K.R.; Howard, A.J.; Hammons, B.E.G. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1994-05-02

134

III-V compound semiconductor dopant profiling using scanning spreading resistance microscopy  

NASA Astrophysics Data System (ADS)

With the rapid growth of the optoelectronics industry, a new generation of analytical tools is required to satisfy the need for a fast and quantitative method for two-dimensional carrier concentration profiling with nanometer resolution on III-V compound semiconductors. A modified atomic force microscopy technique known as Scanning Spreading Resistance Microscopy (SSRM) has the potential to satisfy these requirements. This work examines the usefulness of the SSRM techniques for application towards III-V optoelectronic devices. Measurements have been carried out on MBE-grown GaAs and InP dopant calibration samples. The current transport mechanisms between the diamond-coated SSRM tip and the III-V semiconductor cleaved surface (110) was investigated as a function of semiconductor dopant concentration via current-voltage (I-V) measurement. A positive or negative tip bias was applied while scanning over a wide range of dopant concentrations spanning 1016--1019 cm-3. The results were compared to simulated I-V curves based on thermionic emission theory. The best fits to the data obtained under forward bias indicated that the contact barrier heights, ?B, were much lower than expected from conventional large area planar contacts to GaAs or InP. Barrier height lowering mechanisms due to image forces, thermionic field emission, and minority carrier injection are hypothesized to be responsible for the low barrier height values and their dependence on doping concentration. Under reverse bias, the theory better fits the results obtained for n-type InP and p-type GaAs compared to the larger barrier systems p-type InP and n-type GaAs, where the recombination-generation of carriers play an important role in the overall current. It will be shown that only with the aid of staircase calibration structures based on a secondary calibration standard such as SIMS is it possible to use SSRM as a semi-reliable tool for two-dimensional dopant profiling of III-V compound semiconductors.

Lu, Ryan Paul

135

Development of hybrid photodetectors using single-crystal III-V photocathodes  

NASA Astrophysics Data System (ADS)

Improved performance photodetectors are required for a variety of applications in Biomedical, Astronomy and High-Energy Physics research. The combination of high Quantum efficiencies, III-V photocathodes and Avalanche PhotoDiodes (APDs) can provide enhancements applicable to these research areas. This is particularly true in the photon counting regime. Preliminary development of a Winston-cone-based Hybrid device (ReFerence) and an APD-based imaging Hybrid Photomultiplier Tube are presented. These devices take advantage of the high-performance cathodes and mechanically robust structures used in state of the art night vision imagining systems. Theoretical and observed performance are described.

Smith, Bill; Passmore, Keith; Smith, Arlynn; Lundberg, Randy; Thomas, Nils; Bell, Nick; Lively, Chris; Sillmon, Roger; Benz, Rudy; Karplus, Eric; Abraham, Jim; Farrell, Richard; Ferenc, Daniel

2003-05-01

136

Ultracompact electro-optic phase modulator based on III-V-on-silicon microdisk resonator.  

PubMed

A novel ultracompact electro-optic phase modulator based on a single 9 ?m-diameter III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic waveguide is presented. Modulation is enabled by effective index modification through carrier injection. Proof-of-concept implementation involving binary phase shift keying modulation format is assembled. A power imbalance of ?0.6??dB between both symbols and a modulation rate up to 1.8 Gbps are demonstrated without using any special driving technique. PMID:22739914

Lloret, J; Kumar, R; Sales, S; Ramos, F; Morthier, G; Mechet, P; Spuesens, T; Van Thourhout, D; Olivier, N; Fédéli, J-M; Capmany, J

2012-06-15

137

High-Temperature Thermoelectric Characterization of III–V Semiconductor Thin Films by Oxide Bonding  

Microsoft Academic Search

A device fabrication and measurement method utilizing a SiO2–SiO2 covalent bonding technique is presented for high-temperature thermoelectric characterization of thin-film III–V semiconductor\\u000a materials that suffer from the side-effect of substrate conduction at high temperatures. The proposed method includes complete\\u000a substrate removal, high-temperature surface passivation, and metallization with a Ti-W-N diffusion barrier. A thermoelectric\\u000a material, thin-film ErAs:InGaAlAs metal\\/semiconductor nanocomposite grown on

Je-Hyeong Bahk; Gehong Zeng; Joshua M. O. Zide; Hong Lu; Rajeev Singh; Di Liang; Ashok T. Ramu; Peter Burke; Zhixi Bian; Arthur C. Gossard; Ali Shakouri; John E. Bowers

2010-01-01

138

Dry etching of III-V semiconductors in IBr\\/Ar electron cyclotron resonance plasmas  

Microsoft Academic Search

IBr\\/Ar plasmas were found to be promising candidates for room temperature dry etch processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (˜3,000Å\\/min) at high microwave power (1000W) and good surface morphology (typical root mean square roughness ˜2 nm), while retaining the near-surface stoichiometry. There was little variation of surface smoothness over

J. W. Lee; J. Hong; E. S. Lambers; C. R. Abernathy; S. J. Pearton; W. S. Hobson; F. Ren

1997-01-01

139

Dry etching of III-V semiconductors in IBr\\/Ar electron cyclotron resonance plasmas  

Microsoft Academic Search

IBr\\/Ar plasmas were found to be promising candidates for room temperature dry etch processing of the III-V semiconductors\\u000a GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (?3,000?\\/min) at high microwave power (1000W) and\\u000a good surface morphology (typical root mean square roughness ?2 nm), while retaining the near-surface stoichiometry. There\\u000a was little variation of surface smoothness over

J. W. Lee; J. Hong; E. S. Lambers; C. R. Abernathy; S. J. Pearton; W. S. Hobson; F. Ren

1997-01-01

140

Rotation of principal axes and birefringence in III-V lasers owing to bonding strain.  

PubMed

Measurements of the degree of polarization (DOP) of photoluminescence from the facets of bonded III-V semiconductor diode laser chips show shear strain. The effect of shear strain on the refractive index is investigated. Finite element method (FEM) simulations are matched to the facet map of the DOP for a bonded GaAs chip and are used to extract estimates of the strain induced by die attach. Given estimates of the strains from the FEM simulations, changes in the refractive indices and rotations of the principal axes are calculated for the chip. This work has value in understanding operational changes owing to bonding-induced strain. PMID:24085085

Cassidy, Daniel T

2013-09-01

141

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

NASA Astrophysics Data System (ADS)

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.

Schulthess, Thomas C.

2003-11-01

142

Vertical bridgman and gradient freeze growth of III-V compound semiconductors  

SciTech Connect

Major improvements in the structural and electrical perfection of single crystals of III-V compound semiconductors have been achieved by using new vertical Bridgman-type and vertical gradient freeze techniques. A general review of experimental set-ups used for growth of large diameter crystals of GaP, InP and GaAs is presented. Crystal properties and characteristic features are discussed to illustrate advantages and disadvantages of the vertical Bridgman-type growth techniques. 22 refs., 5 figs.

Bourret, E.D.

1990-07-01

143

Surface diffusion during shadow-mask-assisted molecular-beam epitaxy of III-V compounds  

SciTech Connect

We present a comprehensive discussion of molecular-beam epitaxy of III-V compound semiconductors through shadow masks. Based on model calculations and growth experiments, we examine how the surface diffusion and the incorporation of group-III adatoms depend on the growth configuration, group-III and group-V fluxes, and the crystal orientation. According to a macroscopic diffusion model, gradients of the group-V flux drive the unidirectional migration of group-III adatoms. Although this effect is generally observed in the experiments, the different growth profiles obtained for [110]- and [110]-oriented samples reflect the different roles of A-type and B-type steps in the incorporation of group-III adatoms. We also demonstrate that during the heteroepitaxial growth of InAs, the dissociation of the GaAs substrate is locally enhanced by the incidence of the In beam. This effect can be exploited for shadow-mask-assisted etching on selected areas. In addition, we show how the positions and sizes of III-V nanostructures can be controlled with high precision on a planar substrate by the usage of shadow masks with multiple nanoscale apertures.

Schallenberg, T.; Brunner, K.; Borzenko, T.; Molenkamp, L.W.; Karczewski, G. [Physikalisches Institut, Experimentelle Physik III, Universitaet Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

2005-07-01

144

Charge Traps at and near High-K Oxide/III-V Interfaces  

NASA Astrophysics Data System (ADS)

The effort to achieve higher performance metal-oxide-semiconductor (MOS) devices prompts interest in new semiconductor channel materials such as indium gallium arsenide that can achieve larger drive currents than state-of-the-art Si field effect transistors, at low operating voltages. In order for InGaAs-channel transistors to approach their performance limits, however, high permittivity (high-k) metal oxide gate dielectrics must be prepared on the III-V surface in a manner that produces a minimal areal density of charge-trapping defects. This presentation will review different experimental approaches to prepare relatively passive interfaces between deposited oxides and GaAs or InGaAs. Both pre-oxide deposition and post-deposition methods will be summarized. It will also describe the influence of near-interface defects in the oxides (border traps) and why these particular defects are so significant for arsenide MOS devices. An attempt will be made to associate electrically-active traps detected at different energies in the III-V semiconductor bandgap with specific surface and point defects, based on prior reported experimental and computational observations. The difficulty of quantifying trap densities using typical capacitance-voltage and conductance-voltage methods developed for silicon MOS will be discussed.

McIntyre, Paul

2012-02-01

145

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

PubMed Central

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 ?m 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.

Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

2012-01-01

146

Non-linear piezoelectric polarization in III-V and nitride semiconductors  

NASA Astrophysics Data System (ADS)

Piezoelectricity can have a large impact on the electronic and optical properties of quantum well and quantum dots based devices such as lasers, light emitting diodes, infrared photodetectors. In particular it has been shown to be important in III-V and nitride semiconductors. The piezoelectric effect in quantum Well or in Quantum Dots is usually taken into account by neglecting the non linear term in the piezoelectric tensor. We have calculated the second order piezoelectric tensor for all the III-V (including the nitrides) semiconductors in the Wurtzite and Zincblende structure. And we have derived a relation between the proper and the improper second order piezoelectric coefficients. This relation is used to calculate the proper coefficients which are the experimentally measurable ones. We have calculated the piezoelectric field in several Quantum wells and compare our values to experiment. We show that the second order can be so large for Zinc-Blende materials that it cancels the first order term, we demonstrate also that for Nitrides this effect is much lower. However we show that for severely strained structure such as quantum dots or thin films, the second order piezoelectric effect can even exceed the spontaneous polarization in the nitrides.

Prodhomme, Pierre-Yves; Beya-Wakata, Annie; Bester, Gabriel

2012-02-01

147

New III-V cell design approaches for very high efficiency  

SciTech Connect

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.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O'Bradovich, G.J.; Young, M.P. (Purdue Univ., Lafayette, IN (United States))

1993-01-01

148

Density-functional calculations of carbon doping in III-V compound semiconductors  

NASA Astrophysics Data System (ADS)

This article reports the results of investigations based on local-density-functional theory into the relative formation energies for single substitutional carbon atoms in nine III-V compound semiconductors. The calculations are performed using a supercell formalism derived from the AIMPRO real-space cluster method. Only a very slight trend is discernible down the periodic table. When a metal atom is replaced with carbon, it is energetically least favorable in the phosphides, very marginally lower energy in the arsenides, and ~0.5-0.7 eV lower in the antimonides. The situation is approximately reversed when a P, As, or Sb atom is substituted by a C atom: for the In compounds the energy is ~0.4-0.8 eV higher than for the Al and Ga compounds.

Latham, C. D.; Jones, R.; Öberg, S.; Briddon, P. R.

2001-04-01

149

Modeling of High-Frequency Noise in III-V Double-Gate HFETs  

NASA Astrophysics Data System (ADS)

In this paper, we present a review of recent results on Monte Carlo modeling of high-frequency noise in III-V four-terminal devices. In particular, a study of the noise behavior of InAlAs/InGaAs Double-Gate High Electron Mobility Transistors (DG-HEMTs), operating in common mode, and Velocity Modulation Transistors (VMT), operating in differential mode, has been performed taking as a reference a similar standard HEMT. In the DG-HEMT, the intrinsic P, R and C parameters show a modest improvement, but the extrinsic minimum noise figure NFmin reveals a significantly better extrinsic noise performance due to the lower resistances of the gate contact and the source and drain accesses. In the VMT, very high values of P are obtained since the transconductance is very small, while the differential-mode operation leads to extremely low values of R.

Vasallo, B. G.

2009-04-01

150

Structural properties of III-V zinc-blende semiconductors under pressure  

SciTech Connect

The pseudopotential method within the local-density approximation is used to investigate the static and structural properties of some III-V compound semiconductors. Comparisons of calculated total energies as a function of volume and structure yield information about solid-solid phase transformations. At high pressures the results indicate that several metallic structures are lower in energy than the zinc-blende structure. From our results the compounds (AlP, AlAs, GaP, and GaAs) can be divided into two classes. In the Ga compounds, we find a pressure-induced phase transformation to either rocksalt, ..beta..-Sn, or NiAs, whereas in the Al compounds rocksalt and NiAs are stabilized with respect to ..beta..-Sn. All structures except zinc blende are metallic. We discuss the electronic structure of each phase and show how it relates to structural stability.

Froyen, S.; Cohen, M.L.

1983-09-15

151

ZnSe-based light emitters grown on wide-gap III-V buffer layers  

NASA Astrophysics Data System (ADS)

ZnSe-based laser diodes have recently encountered strong competition from those grown from GaN related materials. These two material systems behave in a very different way as far as defect generation and propagation are concerned. For ZnSe-based materials the lifetime of a laser-diode is very sensitive to the density of pre-existing extended defects in the epitaxial material. Therefore, fabrication of a long- lived ZnSe-based laser diode requires an elimination of extended defects as well as making low-resistivity components in order to minimize device heating. We discuss the molecular beam epitaxy growth and characterization of ZnSe-based epitaxial structures on various III-V buffer layers lattice matched to GaAs. The status of our ZnSe-based laser diodes and microcavity LEDs will also be discussed.

Uusimaa, Petteri; Salokatve, Arto; Savolainen, Pekka; Rinta-Moykky, A.; Pessa, Markus; Souifi, A.; Adhiri, R.; Kiriakidis, George; Moschovis, K.; Stoimenos, J.

1998-07-01

152

In situ access to the dielectric anisotropy of buried III-V/Si(100) heterointerfaces  

NASA Astrophysics Data System (ADS)

We derive an analytical expression to extract the III-V/Si(100) surface and interface dielectric anisotropy from multisample optical in situ data. Based on the established preparation of P-rich GaP/Si(100) and GaP(100) surfaces in vapor-phase ambient, thin GaP films on Si(100) serve as a model system, where we demonstrate the decomposition of reflection anisotropy spectra to obtain surface and interface signals. The resulting surface dielectric anisotropy of P-rich GaP/Si(100) agrees well with that of a homoepitaxial P-rich GaP(100) reference due to consideration of antiphase disorder in our analytical approach. Hence, we are able to calculate interface dielectric anisotropy spectra of individual GaP/Si(100) samples. Their characteristic line shape provides in situ access to nucleation mechanisms in polar-on-nonpolar heteroepitaxy.

Supplie, Oliver; Hannappel, Thomas; Pristovsek, Markus; Döscher, Henning

2012-07-01

153

New III-V cell design approaches for very high efficiency  

SciTech Connect

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.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P. (Purdue Univ., Lafayette, IN (United States))

1993-04-01

154

Confinement effects on the vibrational properties of III-V and II-VI nanoclusters  

NASA Astrophysics Data System (ADS)

We present a first-principles study of the confinement effects on the vibrational properties of thousand atoms (radii up to 16.2 Å) colloidal III-V and II-VI nanoclusters. We describe how the molecular-type vibrations, such as surface-optical, surface-acoustic, and coherent acoustic modes, coexist and interact with bulk-type vibrations, such as longitudinal and transverse acoustic and optical modes. We link vibrational properties to structural changes induced by the surface and highlight the qualitative difference between III-Vs and II-VIs. We describe the size dependence of the vibrations and find good agreement for Raman shifts and for the frequency of coherent acoustic modes with experiments.

Han, Peng; Bester, Gabriel

2012-01-01

155

Scanning tunneling microscopy of doping and compositional III-V homo- and heterostructures  

SciTech Connect

Scanning tunneling microscopy (STM) was used to study the (110) cross-sectional surfaces of molecular-beam epitaxially grown III-V homo- and heterostructures, which include GaAs multiple p-n junctions, (InGa)As/GaAs strained-layer multiple quantum wells, and (AlGa)As/GaAs heterojunctions. Both doping and compositional effects can be resolved by the topographic contrasts of constant-current STM images. The samples were prepared by either cleaving in ultrahigh vacuum or cleaving ex situ followed by sulfide [(NH{sub 4}){sub 2}S] passivation. Sulfide passivated samples have been found to be advantageous for the measurements of scanning tunneling spectroscopy. 20 refs., 5 figs.

Gwo, S.; Chao, K.J.; Smith, A.R. [Univ. of Texas, Austin, TX (United States)] [and others

1993-07-01

156

Ultraviolet photosulfidation of III--V compound semiconductors for electronic passivation  

SciTech Connect

A new vacuum-compatible passivation technique for III--V compound semiconductors has been developed. Sulfur passivation of GaAs(100) is produced by ultraviolet photolytic deposition of a sulfide species from vapor phase elemental sulfur. Photoluminescence studies of the photosulfided GaAs reveal a degree of passivation greater than or equal to that produced by conventional (NH[sub 4])[sub 2]S solution treatments. X-ray photoelectron spectroscopy has shown that the sulfur resides on the surface as a single reduced sulfur species, either as sulfide or disulfide, indicating complete fragmentation of the S[sub 8] ring by UV light in proximity to the surface. The degree of photosulfidation depends strongly on surface preparation as demonstrated by the described surface oxide removal studies.

Zavadil, K.R.; Ashby, C.I.H.; Howard, A.J.; Hammons, B.E. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1994-07-01

157

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

PubMed

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

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

2008-05-27

158

Quantum wells and superlattices for III-V photovoltaics and photodetectors  

NASA Astrophysics Data System (ADS)

Semiconductor quantum wells and superlattices have found numerous applications in optoelectronic devices, such as lasers, LEDs and SOAs, and are an increasingly common feature of high efficiency solar cells and photodetectors. In this paper we will highlight some of the recent developments in the use of low-dimensional III-V semiconductors to improve the performance of photovoltaics by tailoring the bandgap of the junction. We also discuss novel structures designed to maximize photo-generated carrier escape and the application of quantum confinement to other components of the solar cell, such as tunnel junctions. Recent developments in type-II superlattices for photodetectors will also be discussed, including the graded-gap LWIR device based on the W-structured superlattices demonstrated at the Naval Research Laboratory. Modeled results will be presented using the NRL BANDSTM integrated 8-band kp and Poisson solver, which was developed for computing the bandstructures of superlattice and multi-quantum well photodiodes

Lumb, Matthew P.; Vurgaftman, Igor; Affouda, Chaffra A.; Meyer, Jerry R.; Aifer, Edward H.; Walters, Robert J.

2012-10-01

159

Control of growth uniformity of III-V bulk crystals grown by contactless liquid phase electroepitaxy  

NASA Astrophysics Data System (ADS)

Systematic studies of influence of crucible design on uniformity of growth of bulk III-V crystals by contactless liquid phase electroepitaxy (CLPEE) are reported. CLPEE removes the most important drawback of standard liquid phase electroepitaxy, i.e. limited thickness of crystals being due to superheating of the growing crystals by Joule heat generation. However, the CLPEE method in its simplest version suffers from enhanced growth rate at the center of the crystal, which results from majority of electric current flowing to the center of the electrode and dragging solute species. A number of various designs of growth crucible are examined showing that optimized triple-electrode system is capable to provide perfectly uniform growth rate distribution over a large portion of the surface of the growing crystal. In this way the main obstacle in development of the CLPEE technique is removed allowing application of electroepitaxy to obtain large diameter high crystalline quality single crystals with potentially unlimited thickness.

Strak, Pawel; Zytkiewicz, Zbigniew R.; Krukowski, Stanislaw

2012-09-01

160

Selective etching of AlAs for preparation of III-V semiconductor thin foils.  

PubMed

A new method of thin section preparation of III-V semiconductors and multilayers for transmission electron microscopy (TEM) is presented that exhibits considerable advantages over conventional methods such as ion beam milling and jet thinning. GaAs thin films and multilayers of GaAs/In chi Ga1-chi As/GaAs are grown over an etch release layer of AlAs on GaAs substrates by molecular beam epitaxy (MBE). Planar TEM sections prepared by selective etching from these samples show improved ability to image film morphology and dislocation arrangements, and the resulting large thin electron transparent areas facilitate dislocation density measurements and detection of spatial variations. Avoidance of radiation effects and wedge shaping, both common to ion milled samples, allows this method to be used to prepare uniform thickness standards of single layer GaAs films for EDS analysis or lattice imaging. PMID:8358079

Breen, K R; Wilson, R A; McClintock, J A; Ahearn, J S

1993-07-01

161

Generation of low emittance beams using III-V semiconductor photocathodes in an RF gun  

SciTech Connect

Normalized rms emittances well below 10{sup {minus}6}m (with thermal emittance ignored) are now predicted for a 1-nC, 10-ps, flattop beam using an S-band rf gun. The expected thermal emittance of a Cu cathode excited at 263 nm is shown to be {approximately}0.3 x 10{sup {minus}6}m, which is potentially a serious limit on the overall minimum emittance. For GaAs, the photoelectron energy parallel to the emitting surface is now known as a function of the perpendicular energy. By adjusting the vacuum level for the semiconductor, it appears that the thermal emittance can be reduced (compared to Cu) by a factor of 2-even more if the cathode is cooled. The prospects for operating an rf gun with a III-V semiconductor photocathode such as GaAs are summarized.

Clendenin, J.E.

2000-02-22

162

Simulation of mesa structures for III-V semiconductors under ion beam etching  

NASA Astrophysics Data System (ADS)

An argon Ion Beam Etching (IBE) simulation model has been developed to investigate the mesa profile evolution in III-V semiconductors' technology. Particular attention has been focused on the sputtering yield angular dependence effect, on the influence of the material and 2D-morphology of the mask onto the pattern transfer. Experimental sputtering yield versus ion incidence angle is injected into the simulation model. The equations which govern the surface evolution, stem from the current method of characteristics. The simulated profiles show that the trenching phenomenon can appear by only considering the variation of the sputtering yield versus the etched surface canting. This is obtained when neither the ion reflection nor the electric field line deviation are taken into account. On the other hand, the slope transfer from the mask to the GaAs and InP substrates is studied.

Houlet, L.; Rhallabi, A.; Turban, G.

1999-06-01

163

Investigation of the interface recombination velocity of native oxide/III-V semiconductor interfaces  

NASA Astrophysics Data System (ADS)

Although devices and circuits produced from Si have benefited vastly from the presence of native oxides, until recently, compound semiconductor devices formed from III-V materials have not enjoyed the same advantages. Wet thermal oxidation of high Al-bearing III-V semiconductors was recently discovered to create a dense, stable native oxide consisting of Alsb2Osb3. This oxide is an extremely good insulator, has a small index of refraction compared to its native semiconductor, and can be used to define areas of current injection, mask diffusion of impurities, ion implantations, and etches during circuit processing. Native oxides have already had significant impact on the fabrication and properties of multiple semiconductor lasers, but have yet to have an impact upon the world of field effect transistors (FETs). The focus of this thesis has been to extract the interface recombination velocity (IRV) for AlGaAs/GaAs and InAlP/GaAs interfaces for use in device modeling. The technique of time resolved photoluminescence (TRPL) was used to determine the minority carrier lifetime in a double heterostructure both before and after oxidation and the IRV was extracted from this data. Additionally, this thesis presents a summary of the techniques used to characterize native oxides as well as the attributes of native oxides and their application to devices. It also reviews the theory behind minority carrier recombination and the TRPL measurements. AlGaAs-based heterostructures that contained a stop layer (AlGaAs or InAlAs) displayed either a significant decrease or a slight increase in the IRV after oxidation. The opposite effect was observed in structures grown without a stop layer. InAlP-based heterostructures displayed a decrease in the interface recombination velocity in structures containing no stop layer and an increase in the interface recombination velocity in structures containing an AlGaAs or InGaP stop layer after oxidation. Transmission electron microscopy (TEM) micrographs indicate strain visible at all interfaces with In accumulation occurring in the oxide at the interface. The activation energy of the IRV was extracted from variable temperature TRPL measurements performed on selected samples. The activation energies of the interface recombination velocities agreed with previously established results on unoxidized material interfaces.

Curtis, Anthony Paul

164

On the Electronic State of Mn Impurities in III-V Semiconductors  

NASA Astrophysics Data System (ADS)

Most phenomenological models of ferromagnetism in Mn doped GaAs assume that the Mn2+ impurity substitutes primarily the Ga3+ cation with five occupied majority d orbitals that have atomic character and a delocalized Hydrogen like acceptor state. While these assumptions are generally thought to be in agreement with experiment, they are presently not supported by ab initio electronic structure calculations. The latter, which are typically based on the Local Spin Density Approximation (LSDA) to Density Functional Theory, find the Mn d orbitals to be strongly hybridized with the As p states. In this picture the acceptor level is localized with substantial d-character. It is well known that due to spurious self-interactions LSDA calculations tend to overestimate the hybridization of such impurity states. In the present work we have performed first principles electronic structure calculations of Mn impurities in various III-V hosts using the Self Interaction Corrected Local Spin Density Method (SIC-LSD). The method is self interaction free by construction and reproduces the LSDA in the limit of delocalized states. Our calculations show that the electronic state of Mn is strongly affected by the SIC. In GaAs we find that all five Mn d-orbitals SIC correct leaving Mn in a d5 state with a delocalized hole in the As p-band. When Mn substitutes Ga in GaN and GaP, the nature of the electronic state is quite different. Only four d-orbitals SIC correct leaving Mn in a d4 state with a localized hole. These results seem to be in agreement with conclusions drawn from ESR experiments [1,2] and help settle the discussion over the electronic state of Mn in GaP [3]. Moreover the present results imply that the exchange mechanism between Mn moments is different for different III-V host systems. [1] Schneider et. al. Phys. Rev. Lett. 59, 240 (1987); [2] Kreissl et al. Phys. Rev. B 54, 10508 (1996); [3] Dietl et al. cond-mat/0109245. Work supported by the Defense Advanced Research Project Agency and by DOE Office of Science through ASCR/MICS and BES/DMSE under Contract No. DE-AC05-00OR22725 with UT-Battelle LLC.

Schulthess, T. C.

2003-03-01

165

Improved performance III-V quantum well IR photodetectors: review of current and potential focal plane technology  

Microsoft Academic Search

The maturation of the III-V materials technology has provided an opportunity for the development of a producible and affordable class of IR detector arrays. Designs based on the GaAs compounds permit the realization of multiple quantum well IR photodetectors (QWIPs) which are useful for long wavelength focal plane arrays with sizes demonstrated up to 640 X 480. Similar designs using

Lewis T. Claiborne

1997-01-01

166

A test bench for accelerated thermal ageing of III–V concentration solar cells using forward bias injection  

Microsoft Academic Search

Power production from solar photovoltaic systems is constantly increasing. In the last few years concentration photovoltaic (CPV) system using III-V multijunction cells ap- peared on the market, promising doubled efficiencies compared to traditional silicon PV solar panels. For CPV systems to be competitive on the market, they must be reliable to assure long- term operation. This paper presents the design

Fabio Immovilli; Claudio Bianchini; Alberto Bellini; Andrea Sala

2011-01-01

167

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

NASA Astrophysics Data System (ADS)

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.

He, Gang; Chen, Xiaoshuang; Sun, Zhaoqi

2013-03-01

168

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

PubMed

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

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

2011-05-18

169

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

NASA Astrophysics Data System (ADS)

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).

Pantelides, Sokrates T.

2012-02-01

170

First- and second-order piezoelectricity in III-V semiconductors  

NASA Astrophysics Data System (ADS)

We present the results of first-principles plane-wave pseudopotential calculations of piezoelectric coefficients of first and second order for a total of nine III-V binary phases (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb) of zinc-blende semiconductors. These coefficients are used to calculate the piezoelectric fields for [111]-oriented quantum wells (QWs) with different well-barrier combinations and various dimensions. We derive an approximate analytic expression for the strain tensor in the case of pseudomorphic growth along an arbitrary growth direction. Together with the piezoelectric coefficients, this allows a simple calculation of the piezoelectric field up to second order in strain for an arbitrary growth direction and any material combination within the nine III-Vs presented here. Nonlinear contributions to the polarization are shown to be of significant magnitude for all the materials presented. In some cases the field is increased by the second-order terms; in some cases it is decreased. We analyze the chemical trends of the obtained coefficients. We compare our results to available experiments and find good agreement in one-third of the cases, while for the remaining cases the calculated field is larger to significantly larger than in the measurements. We discuss the popular experimental techniques and highlight possible reasons for the discrepancies.

Beya-Wakata, Annie; Prodhomme, Pierre-Yves; Bester, Gabriel

2011-11-01

171

Phase perfection in zinc Blende and Wurtzite III-V nanowires using basic growth parameters.  

PubMed

Controlling the crystallographic phase purity of III-V nanowires is notoriously difficult, yet this is essential for future nanowire devices. Reported methods for controlling nanowire phase require dopant addition, or a restricted choice of nanowire diameter, and only rarely yield a pure phase. Here we demonstrate that phase-perfect nanowires, of arbitrary diameter, can be achieved simply by tailoring basic growth parameters: temperature and V/III ratio. Phase purity is achieved without sacrificing important specifications of diameter and dopant levels. Pure zinc blende nanowires, free of twin defects, were achieved using a low growth temperature coupled with a high V/III ratio. Conversely, a high growth temperature coupled with a low V/III ratio produced pure wurtzite nanowires free of stacking faults. We present a comprehensive nucleation model to explain the formation of these markedly different crystal phases under these growth conditions. Critical to achieving phase purity are changes in surface energy of the nanowire side facets, which in turn are controlled by the basic growth parameters of temperature and V/III ratio. This ability to tune crystal structure between twin-free zinc blende and stacking-fault-free wurtzite not only will enhance the performance of nanowire devices but also opens new possibilities for engineering nanowire devices, without restrictions on nanowire diameters or doping. PMID:20131909

Joyce, Hannah J; Wong-Leung, Jennifer; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati

2010-03-10

172

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

SciTech Connect

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)].

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. [Sandia National Labs., Albuquerque, NM (United States); Foster, C. [Indiana University Cyclotron Facility, Bloomington, IN (United States)

1994-09-01

173

Development and operation of research-scale III-V nanowire growth reactors  

NASA Astrophysics Data System (ADS)

III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy reactors for the growth of InAs nanowires, which both use the same gas handling system. The hot-wall reactor is based on an inexpensive quartz tube furnace and yields InAs nanowires for a narrow range of operating conditions. Improvement of crystal quality and an increase in growth run to growth run reproducibility are obtained using a homebuilt UHV cold-wall reactor with a base pressure of 2×10-9 Torr. A load lock on the UHV reactor prevents the growth chamber from being exposed to atmospheric conditions during sample transfers. Nanowires grown in the cold-wall system have a low defect density, as determined using transmission electron microscopy, and exhibit field effect gating with mobilities approaching 16 000 cm2/(V s).

Schroer, M. D.; Xu, S. Y.; Bergman, A. M.; Petta, J. R.

2010-02-01

174

Development and operation of research-scale III-V nanowire growth reactors.  

PubMed

III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy reactors for the growth of InAs nanowires, which both use the same gas handling system. The hot-wall reactor is based on an inexpensive quartz tube furnace and yields InAs nanowires for a narrow range of operating conditions. Improvement of crystal quality and an increase in growth run to growth run reproducibility are obtained using a homebuilt UHV cold-wall reactor with a base pressure of 2x10(-9) Torr. A load lock on the UHV reactor prevents the growth chamber from being exposed to atmospheric conditions during sample transfers. Nanowires grown in the cold-wall system have a low defect density, as determined using transmission electron microscopy, and exhibit field effect gating with mobilities approaching 16,000 cm(2)/(V s). PMID:20192505

Schroer, M D; Xu, S Y; Bergman, A M; Petta, J R

2010-02-01

175

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

SciTech Connect

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.

Umlor, M.T.; Keeble, D.J. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Physics; Asoka-Kumar, P.; Lynn, K.G. [Brookhaven National Lab., Upton, NY (United States); Cooke, P.W. [Geo-Centers, Inc., Eatontown, NJ (United States). Fort Monmouth Operation

1994-08-01

176

On/off-current Ratio and Ambipolar Behavior of Narrow Bandgap III-V Nanowire FETs  

NASA Astrophysics Data System (ADS)

III-V nanowires (NW) are promising candidates for future device applications due to the high bulk mobility. Yet the small bandgap may result in undesirable high off-current. Here we establish a simple but reliable model that quantitatively explains how channel bandgap and Schottky barriers at metal contacts affect the ambipolar characteristics and the achievable on/off-current ratios of NW-FETs. Thus one can gain insights of the expected transfer characteristics of a given channel material with certain device structure, and the optimal choice of materials for different device applications in ultimately scaled cases. The physics of electron transport in both ideal case (no Schottky barrier) and practical case (with Schottky barrier) is studied. The impact of Schottky barriers is evaluated by numerical calculation of the tunneling current, and is found to play a critical role for the different characteristics observed. A universal plot of on/off ratio vs. bandgap is presented. The excellent agreement between our simulation predictions and experiment results from InAs, InSb, Ge NWs and CNTs highlights the potential of our approach for understanding narrow bandgap NW-FETs, bridging material development and device applications, and guiding future transistor design.

Zhao, Yanjie; Candebat, Drew; Delker, Collin; Zi, Yunlong; Janes, David; Appenzeller, Joerg; Yang, Chen

2013-03-01

177

Novel planarization and passivation in the integration of III-V semiconductor devices  

NASA Astrophysics Data System (ADS)

III-V semiconductor devices typically use structures grown layer-by-layer and require passivation of sidewalls by vertical etching to reduce leakage current. The passivation is conventionally achieved by sealing the sidewalls using polymer and the polymer needs to be planarized by polymer etch-back method to device top for metal interconnection. It is very challenging to achieve perfect planarization needed for sidewalls of all the device layers including the top layer to be completely sealed. We introduce a novel hard-mask-assisted self-aligned planarization process that allows the polymer in 1-3 ?m vicinity of the devices to be planarized perfectly to the top of devices. The hard-mask-assisted process also allows self-aligned via formation for metal interconnection to device top of ?m size. The hard mask is removed to expose a very clean device top surface for depositing metals for low ohmic contact resistance metal interconnection. The process is robust because it is insensitive to device height difference, spin-on polymer thickness variation, and polymer etch non-uniformity. We have demonstrated high yield fabrication of monolithically integrated optical switch arrays with mesa diodes and waveguide electroabsorption modulators on InP substrate with yield > 90%, high breakdown voltage of > 15 Volts, and low ohmic contact resistance of 10-20 ?.

Zheng, Jun-Fei; Hanberg, Peter J.; Demir, Hilmi V.; Sabnis, Vijit A.; Fidaner, Onur; Harris, James S., Jr.; Miller, David A. B.

2004-06-01

178

High-Temperature Thermoelectric Characterization of III-V Semiconductor Thin Films by Oxide Bonding  

NASA Astrophysics Data System (ADS)

A device fabrication and measurement method utilizing a SiO2-SiO2 covalent bonding technique is presented for high-temperature thermoelectric characterization of thin-film III-V semiconductor materials that suffer from the side-effect of substrate conduction at high temperatures. The proposed method includes complete substrate removal, high-temperature surface passivation, and metallization with a Ti-W-N diffusion barrier. A thermoelectric material, thin-film ErAs:InGaAlAs metal/semiconductor nanocomposite grown on a lattice-matched InP substrate by molecular beam epitaxy, was transferred onto a sapphire substrate using the oxide bonding technique at 300°C, and its original InP substrate, which is conductive at high temperatures, was removed. Electrical conductivities and Seebeck coefficients were measured from room temperature to 840 K for this material on both the InP and sapphire substrates, and the measurement results clearly show that the InP substrate effect was eliminated for the sample on the sapphire substrate. A strain experiment has been conducted to investigate the effect of strain on electrical conductivity.

Bahk, Je-Hyeong; Zeng, Gehong; Zide, Joshua M. O.; Lu, Hong; Singh, Rajeev; Liang, Di; Ramu, Ashok T.; Burke, Peter; Bian, Zhixi; Gossard, Arthur C.; Shakouri, Ali; Bowers, John E.

2010-08-01

179

Difference in formation of ferromagnetic MnAs nanoclusters on III-V semiconducting nanowire templates  

NASA Astrophysics Data System (ADS)

The authors report on the differences in ferromagnetic MnAs nanocluster formation on GaAs, GaAs/AlGaAs, GaAs/GaAsP, and InAs nanowire templates by combing selective-area metal-organic vapor phase epitaxy of semiconducting nanowires and endotaxial nanoclustering of MnAs. To characterize the dependences of MnAs nanocluster formation on semiconducting materials of the nanowire templates, GaAs, GaAs/AlGaAs core-shell, and GaAs/GaAsP core-shell nanowires have been grown at 750 °C, whereas InAs nanowires have been grown at 580 °C. MnAs nanoclusters are commonly and most frequently formed at six ridges between two {0-11} crystal facets on hexagonal prisms of III-V semiconducting nanowires. That is presumably because many atomic steps exist between the crystal facets. Here, MnAs nanoclusters are grown "into" the nanowires, as a result of the phenomenon of "endotaxy". Manganese atoms on the nanowires surface form chemical bonds mainly with arsenic atoms of the nanowires, because only manganese organometallic source and hydrogen are supplied, i.e. no supply of arsenic hydride source during the endotaxy of MnAs. In the case of GaAs/GaAsP core-shell and InAs nanowires, however, MnAs nanoclusters are formed on the top {111}B surfaces of the nanowires, as well as at six ridges of the hexagonal prisms. The results obtained in the current work possibly show that the endotaxy of MnAs depends on the thermal stability of the nanowires and/or the strength of atomic bonds in the host materials of nanowires.

Hara, Shinjiro; Fujimagari, Hiromu; Sakita, Shinya; Yatago, Masatoshi

2013-09-01

180

Semiconductor quantum well lasers and related optoelectronic devices on silicon, III-V  

NASA Astrophysics Data System (ADS)

Although an ultimate goal of this work is to achieve long term reliable laser operation of Al(x)Ga(1-x)As-GaAs quantum well heterostructures (QWH's), or similar III-V QWH's, grown on Si, this has proven to be a formidable enough problem that to the best of our knowledge no one has exceeded the results we reported in 1987 and 1988. This problem is of such dimensions that it may not be solved for as much as 10 years, or even more. All we know so far is that continuous (CW) 300 K Al(x)Ga(1-x)As-GaAs QWH lasers can be grown on Si, and that, indeed, the heat sinking of an Al(x)Ga(1-x)As-GaAs QWH laser on Si is better than a similar laser on a GaAs substrate. Nevertheless, the problem of growing better versions of these devices (i.e., long-lived high performance CW 300 K lasers on Si) has run into the fundamental issue of the large GaAs-Si lattice and thermal expansion mismatch, and hence the built-in difficulty in reducing the defects guaranteed by mismatch. Accordingly, and as much as we have worked further on the problem of Al(x)Ga(1-x)As-GaAs QWH lasers on Si, we have worked as hard on other QWH laser problems, as well as a impurity-induced layer disordering (or layer intermixing, IILD) and its application in laser devices. We briefly describe this work below and append the titles and abstracts of the papers we have published on laser studies and IILD.

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

1989-06-01

181

Radiation effects in III-V semiconductors and heterojunction bipolar transistors  

NASA Astrophysics Data System (ADS)

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.

Shatalov, Alexei

182

Scanning Tunneling Spectroscopy on III-V Materials: Effects of Dimensionality, Magnetic Field, and Magnetic Impurities  

NASA Astrophysics Data System (ADS)

We review low-temperature scanning tunneling spectroscopy (STS) investigations of the local electron density of states (LDOS) of different electron and hole systems in III-V semiconductors. By cleavage of InAs or InSb, a clean (110) surface can be prepared, with no intrinsic surface states in a range of ± 1 eV around the band edges, which is the relevant energy window for STS. This allows the study of the electronic properties of the simple parabolic, s-like conduction band, thus giving access to effects induced by interaction. Systems in different dimensions and in an applied magnetic field have been studied in real space on the atomic scale in order to disentangle the interesting but complex interaction of electrons with disorder. We focus on a comparison between the three-dimensional (3D) electron system and the two-dimensional (2D) electron system with and without magnetic fields. While without a magnetic field, the electronic wave functions are much more complex in 2D than in 3D, an appealing similarity has been found in high magnetic fields. In 2D, the imaged states can be clearly identified with the states responsible for integer quantum Hall transitions. The origin of the 3D states appearing in the extreme quantum limit is still not clear. Furthermore, by doping the semiconductor with magnetic acceptors like Mn, the properties of the bound hole and its interaction with the tip-induced potential can be studied on the local scale. The LDOS of the hole has a strongly anisotropic shape, which is further disturbed by interaction with the (110) surface.

Morgenstern, Markus; Wiebe, Jens; Marczinowski, Felix; Wiesendanger, Roland

183

Bandgap mapping for III-V quantum well by electron spectroscopy imaging.  

PubMed

The concept of 'bandgap mapping' was proposed originally to map the inhomogeneity of band energy in III-V semiconductors with a spatial resolution of a few nanometres in a scanning transmission electron microscope with the focus beam mode. In this paper, several techniques were developed to demonstrate the possibility to map the distribution of bandgap energies for GaN/AlN quantum-well structures using electron spectroscopy imaging (ESI). The phase correlation function was used to register different energy-loss images among ESI series with an accuracy of 1 pixel. The energy dispersion of ESI series was improved by a fast Fourier transform interpolation method. An iterative multivariable least square algorithm was derived to refine the fitting of the single scattering distribution to an analytic form of the density of states function a(E - E(g))(0.5). The inhomogeneity of the band energy of the quantum well can be revealed from the band-energy map. A threshold filter method is applied to estimate the average value and SD of the bandgap energy from barrier and well regions in the energy map. The average bandgap energy of AlN and GaN is determined to be 5.62 +/- 0.35 and 3.87 +/- 0.36 eV, respectively. The effect of delocalization on the accuracy of band-energy determination is discussed. The 2sigma(E(g)) accuracy of this analysis is comparable to half of the energy resolution of the ESI experiment. PMID:15582935

Tsai, Jin-Sheng; Kai, Ji-Jung; Chang, Li; Chen, Fu-Rong

2004-01-01

184

A III-V nanowire channel on silicon for high-performance vertical transistors.  

PubMed

Silicon transistors are expected to have new gate architectures, channel materials and switching mechanisms in ten years' time. The trend in transistor scaling has already led to a change in gate structure from two dimensions to three, used in fin field-effect transistors, to avoid problems inherent in miniaturization such as high off-state leakage current and the short-channel effect. At present, planar and fin architectures using III-V materials, specifically InGaAs, are being explored as alternative fast channels on silicon because of their high electron mobility and high-quality interface with gate dielectrics. The idea of surrounding-gate transistors, in which the gate is wrapped around a nanowire channel to provide the best possible electrostatic gate control, using InGaAs channels on silicon, however, has been less well investigated because of difficulties in integrating free-standing InGaAs nanostructures on silicon. Here we report the position-controlled growth of vertical InGaAs nanowires on silicon without any buffering technique and demonstrate surrounding-gate transistors using InGaAs nanowires and InGaAs/InP/InAlAs/InGaAs core-multishell nanowires as channels. Surrounding-gate transistors using core-multishell nanowire channels with a six-sided, high-electron-mobility transistor structure greatly enhance the on-state current and transconductance while keeping good gate controllability. These devices provide a route to making vertically oriented transistors for the next generation of field-effect transistors and may be useful as building blocks for wireless networks on silicon platforms. PMID:22854778

Tomioka, Katsuhiro; Yoshimura, Masatoshi; Fukui, Takashi

2012-08-01

185

Optimization of the silicon subcell for III-V on silicon multijunction solar cells: Key differences with conventional silicon technology  

NASA Astrophysics Data System (ADS)

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon (Si) bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on Si for photovoltaic (PV) applications. Such integration would offer a cost breakthrough for PV technology, unifying the low cost of Si and the efficiency potential of III-V multijunction solar cells. The optimization of the Si solar cells properties in flat-plate PV technology is well-known; nevertheless, it has been proven that the behavior of Si substrates is different when processed in an MOVPE reactor In this study, we analyze several factors influencing the bottom subcell performance, namely, 1) the emitter formation as a result of phosphorus diffusion; 2) the passivation quality provided by the GaP nucleation layer; and 3) the process impact on the bottom subcell PV properties.

García-Tabarés, Elisa; Martín, Diego; García, Iván; Lelièvre, Jean François; Rey-Stolle, Ignacio

2012-10-01

186

Wafer-scale integration of group III-V lasers on silicon using transfer printing of epitaxial layers  

NASA Astrophysics Data System (ADS)

The hard-drive and electronic industries can benefit by using the properties of light for power transfer and signalling. However, the integration of silicon electronics with lasers remains a challenge, because practical monolithic silicon lasers are not currently available. Here, we demonstrate a strategy for this integration, using an elastomeric stamp to selectively release and transfer epitaxial coupons of GaAs to realize III-V lasers on a silicon substrate by means of a wafer-scale printing process. Low-threshold continuous-wave lasing at a wavelength of 824 nm is achieved from Fabry-Pérot ridge waveguide lasers operating at temperatures up to 100 °C. Single and multi-transverse mode devices emit total optical powers of >60 mW and support modulation bandwidths of >3 GHz. This fabrication strategy opens a route to the low-cost integration of III-V photonic devices and circuits on silicon and other substrates.

Justice, John; Bower, Chris; Meitl, Matthew; Mooney, Marcus B.; Gubbins, Mark A.; Corbett, Brian

2012-09-01

187

A novel application of the vertical gradient freeze method to the growth of high quality III-V crystals  

Microsoft Academic Search

A new process for growing high-quality single crystals of the III-V compounds, based on the vertical gradient freeze methods, is described. The method features crystal growth in a boron nitride seeded crucible, with axial and radial thermal gradients that are much lower than in the conventional liquid encapsulated Czochralski technique. This method has been applied to grow large (50-mm diameter)

W. A. Gault; E. M. Monberg; J. E. Clemans

1986-01-01

188

Schrödinger-Poisson and Monte Carlo analysis of III–V MOSFETs for high frequency and low consumption applications  

Microsoft Academic Search

III-V MOSFET (Metal Oxide Semiconductor Field Effect Transistor) with high-? gate dielectric stack appears as a viable alternative to enhance not only microwave performance but also logic circuits with low supply voltage. This allows fulfilling high-speed and low-power specifications for intelligent applications. Indeed, combining weak gate leakage of standard MOSFETs and good RF performance of HEMTs (High Electron Mobility Transistors),

Ming Shi; Jérôme Saint-Martin; Arnaud Bournel; Philippe Dollfus

2010-01-01

189

Revised ab initio Natural Band Offsets of All Group IV, II-VI and III-V Semiconductors  

SciTech Connect

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 reference level volume deformation 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.

Li, Y. H.; Walsh, A.; Chen, S.; Yin, W. J.; Yang, J. H.; Li, J.; Da Silva, J. L. F.; Gong, X. G.; Wei, S. H.

2009-01-01

190

Realization of one-chip-multiple-wavelength laser diodes with II-VI\\/III-V compound semiconductors  

Microsoft Academic Search

A laser diode which includes II-VI device structure directly grown on III-V device structure is proposed. This idea makes possible one-chip-multiple-wavelength operation in the visible wavelength region by the vertical integration of individual light emitters, which is demonstrated by a ZnCdSe\\/ZnSe\\/ZnMgBeSe quantum-well structure for a blue-green light emitter grown by molecular beam epitaxy directly on a metalorganic chemical vapor deposition

J. S. Song; M. W. Cho; D. C. Oh; H. Makino; T. Hanada; T. Yao; B. P. Zhang; Y. Segawa; J. H. Chang; H. S. Song; I. S. Cho; H. W. Kim; J. J. Jung

2003-01-01

191

New surface atomic structures for column V overlayers on the (110) surfaces of III-V compound semiconductors  

Microsoft Academic Search

Two new minimum-energy surface structures have been identified for p(1 Ã 1) overlayers of Sb on the (110) surface of III-V compound semiconductors using a tight-binding total-energy formalism previously developed for these systems. The first is the commensurate chain'' structure in which Sb zig-zag chains are commensurate with, and on top of, the Ga--As unreconstructed surface zig-zag chains. This structure

John P. LaFemina; C. B. Duke; C. Mailhiot

1990-01-01

192

III-V compound semiconductor MOSFETs using Ga2O3 (Gd2O3) as gate dielectric  

Microsoft Academic Search

We report a III-V based metal oxide semiconductor field effect transistor (MOSFET) technology using Ga2O3(Gd2O3) as the gate insulator. Enhancement-mode p- and n-channel, depletion-mode n-channel GaAs MOSFETs, and enhancement-mode n-channel In0.53Ga0.47As MOSFETs were demonstrated

F. Ren; M. Hong; J. M. Kuo; W. S. Hobson; J. R. Lothian; H. S. Tsai; J. Lin; J. P. Mannaerts; J. Kwo; S. N. G. Chu; Y. K. Chen; A. Y. Cho

1997-01-01

193

High-Density ECR-Plasma Deposited Silicon Nitride Films for Applications in III\\/V-based Compound Semiconductor Devices  

Microsoft Academic Search

We report on the ECR-plasma deposition and characterization of silicon nitride film exhibiting high breakdown field strength (>8 MV\\/cm) for applications in III\\/V-based compound semiconductor devices. The film deposited at 240°C contains around 13 at.% hydrogen. The hysteresis in mechanical stress, obtained from thermal cycling of the stress in film is negligible. The application of the film is being demonstrated

R. E. Saha; M. Mikulla; H. Baumann; F. Benkhelifa; R. Quay; G. Weimann

194

Realization of one-chip-multiple-wavelength laser diodes with II-VI/III-V compound semiconductors  

NASA Astrophysics Data System (ADS)

A laser diode which includes II-VI device structure directly grown on III-V device structure is proposed. This idea makes possible one-chip-multiple-wavelength operation in the visible wavelength region by the vertical integration of individual light emitters, which is demonstrated by a ZnCdSe/ZnSe/ZnMgBeSe quantum-well structure for a blue-green light emitter grown by molecular beam epitaxy directly on a metalorganic chemical vapor deposition grown InGaP/InGaAlP device wafer for a red light emitting device. The feasibility of the II-VI/III-V complex light emitter is demonstrated by optical-pumping experiments. Optically pumped lasing at 504 and 664 nm is achieved from II-VI and III-VI laser structures on one chip simultaneously at room temperature with a threshold power of 115 and 84 kW/cm2, respectively. The present results clearly show the feasibility of epitaxial integration of II-VI and III-V laser structures, which will stimulate the investigation of multifunctional optical devices.

Song, J. S.; Cho, M. W.; Oh, D. C.; Makino, H.; Hanada, T.; Yao, T.; Zhang, B. P.; Segawa, Y.; Chang, J. H.; Song, H. S.; Cho, I. S.; Kim, H. W.; Jung, J. J.

2003-06-01

195

Static and dynamical properties of II-VI and III-V group binary solids  

NASA Astrophysics Data System (ADS)

In this paper, we extend to II-VI and III-V group binary solids of zinc blende (ZB) structure with conduction d-electrons the calculation of static and dynamical properties such as bulk modulus (B) and cohesive energy or total energy (Ecoh) using the plasma oscillation theory of solids formalism already employed for ternary chalcopyrite semiconductors. The present method is not limited to tetrahedrally coordinated semiconductors and ternary chalcopyrites, but can be used for all semiconducting compounds. We have applied an extended formula on ZB structured binary semiconductors and found better agreement with the experimental data as compared to the values evaluated by previous researchers. The bulk modulus and cohesive energy of ZB-type structure compounds exhibit a linear relationship when plotted on a log-log scale against the plasmon energy planck?p (in eV), but fall on a straight line. The results for bulk modulus differ from experimental values by the following amounts: ZnS 0.36%, ZnSe 10%, ZnTe 0.62%, CdS 1.8%, CdSe 7.4% and CdTe 1.6%, AlP 2.6%, AlAs 5.3%, AlSb 4.0%, GaP 0%, AlAs 0%, AlS 4.4%, InP 0%, InAs 0% and InSb 2.1%; and the results for cohesive energy differ from experimental values by the following amounts: ZnS 0.16%, ZnSe 0.73%, ZnTe 0.6%, CdS 7.6%, CdSe 3.5%, CdTe 2.5%, AlP 2.0%, AlAs 3.0%, AlSb 11.1%, GaP 14.6%, AlAs 17.0%, AlSb 8.7%, InP 4.3%, InAs 5.5% and InSb 0.6%.

Yadav, D. S.; Singh, D. V.

2012-01-01

196

Update on III-V antimonide-based superlattice FPA development and material characterization  

NASA Astrophysics Data System (ADS)

Much progress has been made in the past 2 years in developing III-V antimonide-based superlattice infrared detectors and focal plane arrays (FPAs). In the area of detector material growth by molecular beam epitaxy, the wafer foundry group, helped by government-trusted entities and other partnering institutions, has leapfrogged many years of R&D effort to become the premier detector wafer supplier. The wafers produced are of high quality as measured by surface morphology, defect density, photoluminescence property, high-resolution X-ray diffraction, and diode current-voltage characteristics. In the area of detector design and FPA processing, the team-consisting of members from government laboratories, academia, and the FPA industry-has made rapid progress in device structure design, detector array etching, passivation, hybridization, and packaging. The progress is reflected in the steady reduction in FPA median darkcurrent density and improvement in median quantum efficiency, as well as reasonably low median noise-equivalent different temperature under 300 K scene background, when compared with the performance from some of the commercially available HgCdTe FPAs. In parallel with the FPA research and development effort, a small amount of funding has been devoted to measuring minority carrier lifetimes and to understanding life-killing defects and mechanisms of superlattice devices. Results of direct time-resolved photoluminescence measurement on superlattice absorbers indicate relatively short lifetimes (on the order of 30 ns) due to Shockley-Read-Hall mechanism. Modeling and curve fitting with diode current-voltage data indicate longer minority carrier lifetimes, although the best fit lifetime values differ greatly, possibly due to the difference in material quality and device structure. Several models or hypotheses have been proposed to explain experimental data. More data are required to validate these models and hypotheses. Further work is also necessary to reconcile the substantially different results from different groups and to truly understand the physics of minority carrier lifetimes, which is necessary to improve the lifetime and realize the theoretical promise of superlattice materials.

Zheng, Lucy; Tidrow, Meimei; Bandara, Sumith; Aitcheson, Leslie; Shih, Tiffany

2011-05-01

197

Lasing characteristics and optical properties of II-VI and III-V semiconductor microdisks  

NASA Astrophysics Data System (ADS)

This dissertation focuses on exploring the interaction between confined photons and confined electronic states in new classes of semiconductor microcavities. We apply epitaxial and microfabrication technologies to make semiconductor microstructures that contain embedded nanostructures such as quantum wells and quantum dots. We use optical techniques, such as cryogenic static and dynamic microphotoluminescence, to study the physics of confined photons and confined electronic states in these systems. The first set of experiments focus on ZnSe microdisks containing Zn 0.7Cd0.3Se quantum wells. Unlike the more extensively investigated microcavities based upon the III-V semiconductors, these wide band gap systems are expected to be characterized by stronger excitonic effects. We have developed new protocols for the consistent fabrication of ZnSe microdisks of high structural quality, supported on (Al,Ga)As pedestals. The photoluminescence emission spectrum is dominated by excitonic recombination in the quantum well region. We observe a set of sharp emission lines on the low energy shoulder of the quantum well photoluminescence. We attribute these features to the coupling between exciton emission and the whispering-gallery modes of the microdisk. This inference is consistent with our temperature-dependent measurements. However, power-dependent measurements of these microdisks did not produce any evidence for stimulated emission, even when excited at high optical intensities using pulsed excitation. We conclude that harmful surface recombination may be responsible for these observations. The next set of experiments focus on the steady state and dynamic optical properties of GaAs/(Ga,Al)As microdisk containing interface fluctuation quantum dots. These constitute a departure from previously studied GaAs/(Ga,Al)As microdisk systems that contain self assembled quantum dots. We have developed a new processing protocol for fabricating these microdisks, including a surface passivation technique that greatly enhances the optical properties of these systems. Stimulated emission is achieved in the microdisk cavity using optical excitation. Steady-state measurements of the stimulated emission via whispering gallery modes yield a quality factor Q ˜ 5800 and a coupling constant beta ˜ 0.09. The broad gain spectrum produces mode hopping between spectrally adjacent whispering gallery modes as a function of temperature and excitation power. (Abstract shortened by UMI.)

Wang, Wei-Hua

198

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

NASA Astrophysics Data System (ADS)

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

Smith, Joshua T.

199

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

SciTech Connect

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.

Fowler, Bruce A. [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States)]. E-mail: bxf9@cdc.gov; Conner, Elizabeth A. [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States); Yamauchi, Hiroshi [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States)

2005-08-07

200

Low-frequency noise sources in III-V semiconductor heterostructures  

NASA Astrophysics Data System (ADS)

III-V semiconductor heterostructures have widespread interest in both electrical and optical applications. Their figure-of-merit low-frequency noise level directly sets the limits of the performance of devices and indirectly serves as the indicator of material properties and device reliability. In particular, generation-recombination noise signals in the low-frequency noise range directly indicate the dominant traps that impact device operation. In this dissertation, low-frequency noise source investigations of GaAs/buffer and AlxGa1-xN/GaN heterostructures in the applications of microwave power amplifiers will be presented. For GaAs/buffer heterostructures, low-frequency noise characteristics of GaAs-On-Insulator metal-semiconductor field effect transistors, for which the insulating buffer layer was produced by lateral wet-oxidation of AlAs, are studied. Devices with different gate widths were fabricated resulting in different over-oxidation times for the AlAs layer. Three characteristic generation-recombination noise signatures are observed depending on the measurement temperature and the gate bias. A generation-recombination noise signature with energy level at Ec-0.69 eV is found to increase with the amount of over-oxidation time. This near mid-gap trap shows an increase in concentration towards the oxide interface, and it is tentatively assigned to an arsenic-antisite related defect known from previous studies as EB4. A possible mechanism for the formation and the microscopic origin of this defect are discussed. 1/f interface noise model is applied to analyze the GaAs/buffer interfacial quality. The effective interface state density was found to be as high as 1015 cm-2 and increase with additional over-oxidation. A correlation between the amount of over-oxidation and the number of calculated interface states is observed. For AlxGa1-xN/GaN heterostructures, low-frequency noise characteristics of AlxGa1-xN/GaN HEMTs with Al composition of 28--35% in the barrier layer are studied. A generation-recombination noise signature is attributed to a trap in AlxGa1-x N barrier layer which increases in concentration towards the Al xGa1-xN/GaN interface. The origin and the location of low-frequency noise were differentiated by the drain current dependent measurement. When the long-channel device is operated with an open channel (e.g. VG = 0), the main noise source resides in the gated channel instead of in the ungated region. Hooge's parameter of the gated channel (alpha ˜ 10-4) is found to be independent of the Al composition but dependent on the AlxGa1-x N barrier thickness. This is proposed to correspond to the onset of barrier relaxation. Even though the AlxGa1-xN/GaN HEMT exhibits a low level of gate leakage current (<1% of drain current), the low-frequency noise is still heavily influenced by the gate leakage current at certain bias conditions. The effect of gate leakage current on the low-frequency noise properties is discussed. The surface leakage path appeared to dominate the low-frequency noise properties for devices operated at a high IG/ID ratio.

Tzeng, Susie

201

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

SciTech Connect

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.

Ringel, S. A.

2008-11-01

202

Reactivity and control of III–V surfaces for passivation and Schottky barrier formation  

Microsoft Academic Search

The N-for-As, P-for-As and Sb-for-As anion exchange reactions at GaAs surfaces, and the N-for-P anion exchange reaction at the GaP surface have been investigated with the aim at the formation of a thin high-gap surface layer for passivation of GaAs and GaP. Among the investigated anion exchange reactions, the P-for-As results in the formation of a ternary alloys GaPyAs1?y not

Giovanni Bruno

2004-01-01

203

Enhancement of the evanescent coupling between III-V/Si hybrid microring laser and bus waveguide by using a bending coupler  

NASA Astrophysics Data System (ADS)

A bending directional coupler is presented to enhance the evanescent coupling between a compact deeply-etched III-V/Si hybrid microring laser and its small Si bus waveguide. With the present design, one could realize a sufficient evanescent coupling between the III-V/Si hybrid microring even when the gap between the microring and the bus waveguide is relatively large gap (~ 400nm). This makes the fabrication easier.

Dai, Daoxin; Liang, Di; Bowers, John E.

2009-11-01

204

Development of laser diode layers based upon III-V compound semiconductors in the wavelength range from 0.7 ?m to 0.9 ?m  

Microsoft Academic Search

This paper is based on the work done to grow the semiconductor layers of III-V compound, based on AIGaAs\\/GaAs for the laser diode. The Laser diode is an optoelectronic device that consists of many layers stacked one upon the other. Laser diodes based on the III-V compound is preferred because of high mobility of electrons, low mass and direct band

Dimple Garg; Neena Gupta; Nathai Ram Yadav

2005-01-01

205

III\\/V ratio based selectivity between strained Stranski-Krastanov and strain-free GaSb quantum dots on GaAs  

Microsoft Academic Search

The authors demonstrate and characterize type-II GaSb quantum dot (QD) formation on GaAs by either Stranski-Krastanov (SK) or interfacial misfit (IMF) growth mode. The growth mode selection is controlled by the gallium to antimony (III\\/V) ratio where a high III\\/V ratio produces IMF and a low ratio establishes the SK growth mode. The IMF growth mode produces strain-relaxed QDs, where

G. Balakrishnan; J. Tatebayashi; A. Khoshakhlagh; S. H. Huang; A. Jallipalli; L. R. Dawson; D. L. Huffaker

2006-01-01

206

Numerical and experimental assessment of charge control in III-V nano-metal-oxide-semiconductor field-effect transistor.  

PubMed

III-V Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) with a gate stack based on high-kappa dielectric appears as an appealing solution to increase the performance of either microwave or logic circuits with low supply voltage (V(DD)). The main objective of this work is to provide a theoretical model of the gate charge control in III-V MOS capacitors (MOSCAPs) using the accurate self-consistent solution of 1D and 2D Poisson-Schrödinger equations. This study allows us to identify the major mechanisms which must be included to get theoretical calculations in good agreement with experiments. Actually, our results obtained for an Al2O3/In0.53Ga0.47As MOSCAP structure are successfully compared to experimental measurements. We evaluate how III-V MOS technology is affected by the density of interface states which favors the Fermi level pinning at the Al2O3/In0.53Ga0.47As interface in both depletion and inversion regimes, which is a consequence of the poor gate control of the mobile inversion carrier density. The high energy valleys (satellite valleys) contribution observed in many theoretical calculations appears to be fully negligible in the presence of interface states. The enhancement of doping density in the channel is shown to improve the short-channel effect (SCE) immunity but to the price of higher sensitivity to the interface trap effect which manifests through a low Fermi level movement efficiency at interface in OFF-state and a low inversion carrier density in ON-state, even in the long channel case. PMID:23646513

Shi, Ming; Saint-Martin, Jérôme; Bournel, Arnaud; Querlioz, Damien; Dollfus, Philippe; Mo, Jiongjong; Wichmann, Nicolas; Desplanque, Ludovic; Wallart, Xavier; Danneville, Francois; Bollaert, Sylvain

2013-02-01

207

Calculations of the spin-lattice coupling coefficients for 3d5 ions in III-V compounds  

NASA Astrophysics Data System (ADS)

The spin-lattice coupling coefficients G11 and G44 for InP:Fe3+ and GaP:Mn2+ crystals have been calculated from the expressions based on the spin-orbit coupling mechanism. The results, as well as those for GaP:Fe3+ in my previous paper, show good agreement with the experimental findings. It appears that this mechanism is applicable to the explanations of the spin-lattice coupling coefficients for 3d5 ions in III-V compounds. The disparity between theory and experiment for the coefficients G11 and G44 of GaAs:Fe3+ crystals is discussed.

Wen-Chen, Zheng

1992-07-01

208

A physics-based fitting and extrapolation method for measured impact ionization coefficients in III-V semiconductors  

Microsoft Academic Search

A general approach based on a physical model of impact ionization to fit and extrapolate measured ionization coefficients of electrons ? and holes ? in III-V semiconductors is described. Materials being considered include GaAs, AlxGa1?xAs (x=0.1–0.4), InP, In0.53Ga0.47As, and In0.52Al0.48As. Expressions giving the correct dependencies are obtained at very large or small electric fields outside the range of most measurements

Hin-Fai Chau; Dimitris Pavlidis

1992-01-01

209

Comparing The Energy Yield of (III-V) Multi-Junction Cells With Different Numbers Of Sub-Cells  

NASA Astrophysics Data System (ADS)

We examine the performance of III-V multi-junction solar cells with different numbers of cells under diverse spectral conditions. Using both a detailed balance model and a more realistic analytical charge-transport model, we simulate the energy harvesting properties of a range of cell designs with calculated spectra over 1 year. The spectra are generated using the SMARTS2 model with real atmospheric data for three locations with diverse spectral characteristics. The work underlines the importance of matching multi-junction solar cells to their target spectrum in order to maximize their energy harvest potential.

Lumb, M. P.; Dobbin, A. L.; Bushnell, D. B.; Lee, K. H.; Tibbits, T. N. D.

2010-10-01

210

Doping profile control and two-dimensional electron gas formation by Si diffusion into III-V compounds  

Microsoft Academic Search

The doping characteristics of Si-diffused III-V compounds have been investigated using fully dielectric diffusion sources consisting of undoped SiO(x)\\/SiN double-layered films prepared by plasma-enhanced chemical-vapor deposition. It is demonstrated that the rectangular-shaped carrier concentration profiles resulting from the Si diffusion in GaAs can be controlled by varying the deposition parameters of the SiO(x)\\/SiN films, i.e., the N2O flow rate in

Shigeharu Matsushita; Satoshi Terada; Emi Fujii; Daijiro Inoue; Kohji Matsumura; Yasoo Harada

1994-01-01

211

Fabrication and characterization of III–V compound semiconductor Bragg-Fresnel lenses for hard x-ray microfocusing  

Microsoft Academic Search

Hard x-ray phase Bragg-Fresnel lenses (BFLs) have been made in III–V semiconductors of (111) GaAs and InP, and in Si for comparison purposes. Diffractive linear and circular patterns were defined with conventional electron beam lithography. Pattern transfer was accomplished with reactive ion etching (RIE) using gases of BCl3\\/Cl2\\/SiCl4, CH4\\/H2\\/Ar, and BCl3Cl2, respectively. In addition, selective etching of heteroepitaxial GaAs devices

E. J. Caine; S. Shi; E. L. Hu; Y. Li; S. H. J. Idziak; G. Subramanian; C. R. Safinya

1997-01-01

212

Investigation of MOS Interfaces with Atomic-Layer-Deposited High-k Gate Dielectrics on III-V Semiconductors  

Microsoft Academic Search

The purpose of this research work was to investigate the surface passivation methods and metal gate\\/high-k dielectric gate stacks for metal-oxide-semiconductor devices (MOS) on III-V compound semiconductor materials -- (i) GaAs for future high-speed low-power logic devices and (ii) AlGaN\\/GaN heterostructure for future high-speed high-power devices. GaAs is a candidate material for high-mobility channel in a NMOS transistor to extend

Rahul Suri

2010-01-01

213

The coupling of thermochemistry and phase diagrams for Group III-V semiconductor systems  

NASA Astrophysics Data System (ADS)

Assessment studies revealed inconsistencies in reported Tl activities. Ga and In activities were measured as a function of temperature and composition in liquid Ga-Tl and In-Tl alloys. Large positive deviations from ideal solution behavior were found in Ga-Tl while the In-Tl system showed nearly ideal behavior. The extent of solid solution in the compound AlSb was determined by electrochemical titration with a measured range 8 x 10 to the -4 to 2 x 10 to the -3 mole fraction at 846 C. The enthalpy of mixing GaP and InP to form the pseudobinary solid solution Ga(sub x)In(sub 1-x)P was determined by solution calorimetry. A positive enthalpy of mixing was reported. Knudsen effusion studies were performed on Ga(sub x)In(sub 1-x)P alloys. Results indicate the existence of a solid miscibility gap in this system. CALPHAD procedures were applied to the Al-Ga-In-Sb pseudoternary and Ga-In-Sn ternary systems.

Anderson, T. J.

1987-05-01

214

Predicted energy band gaps of (AIIIBV)1-xXIV2x metastable, substitutional, crystalline alloys  

Microsoft Academic Search

Predictions of the energy band gaps as functions of alloy composition are given for the Greene alloys, which are metastable, crystalline, substitutional alloys of III-V compounds and group-IV elemental materials. All possible combinations of these alloys involving Al, Ga, In, P, As, Sb, Si, Ge, and Sn are considered. The Gamma and L conduction-band minima, relative to the valence-band maxima,

David W. Jenkins; Kathie E. Newman; John D. Dow

1985-01-01

215

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

SciTech Connect

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.

Yamaguchi, Masafumi; Bouzazi, Boussairi; Suzuki, Hidetoshi; Ikeda, Kazuma; Kojima, Nobuaki; Ohshita, Yoshio [Toyota Technological Institute, Nagoya 468-8511 (Japan)

2012-10-06

216

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

NASA Astrophysics Data System (ADS)

We have been studying concentrator multi-junction solar cells under Japanese Innovative Photovoltaic R&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.

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

2012-10-01

217

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

PubMed

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??m thick InP thin-films on Mo foils with ultra-large grain size up to 100??m, 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

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

218

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

NASA Astrophysics Data System (ADS)

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 ?m thick InP thin-films on Mo foils with ultra-large grain size up to 100 ?m, 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.

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

219

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

SciTech Connect

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.

Wolk, J.A.

1992-11-01

220

Generation of substrate-free III–V nanodisks from user-defined multilayer nanopillar arrays for integration on Si  

NASA Astrophysics Data System (ADS)

High material quality InP-based multilayer nanopillar (NP) arrays are fabricated using a combination of self-assembly of silica particles for mask generation and dry etching. In particular, the NP arrays are made from user-defined epitaxial multilayer stacks with specific materials and layer thicknesses. An additional degree of flexibility in the structures is obtained by changing the lateral diameters of the NP multilayer stacks. Pre-defined NP arrays made from InGaAsP/InP and InGaAs/InP NPs are then used to generate substrate-free nanodisks of a chosen material from the stack by selective etching. A soft-stamping method is demonstrated to transfer the generated nanodisks with arbitrary densities onto Si. The transferred nanodisks retain their smooth surface morphologies and their designed geometrical dimensions. Both InP and InGaAsP nanodisks display excellent photoluminescence properties, with line-widths comparable to unprocessed reference epitaxial layers of similar composition. The multilayer NP arrays are potentially attractive for broad-band absorption in third-generation solar cells. The high optical quality, substrate-free InP and InGaAsP nanodisks on Si offer a new path to explore alternative ways to integrate III–V on Si by bonding nanodisks to Si. The method also has the advantage of re-usable III–V substrates for subsequent layer growth.

Naureen, S.; Shahid, N.; Dev, A.; Anand, S.

2013-06-01

221

A novel type of ultra-compact lateral-current-injection III/V photonic device integrated on SOI for electronic-photonic chip application  

NASA Astrophysics Data System (ADS)

An on-chip light source plays a determinant role in the realization of integrated photonic chips for optical interconnects technology. Several integration schemes of III/V laser on SOI platform for on-chip laser application have been proposed and demonstrated. However, most of those integration approaches do not provide effective solutions for the following two problems: effective light confinement/amplification in the III/V active region; and efficient light transfer/coupling between silicon and III/V waveguide. In this paper, a novel approach to integrate an ultra-compact Lateral-Current-Injection (LCI) laser on silicon-on-insulator (SOI) platform by direct wafer bonding technique is proposed and designed. The proposed LCI device has an ultra-thin thickness of 270 nm which is ~10 times thinner than the vertical current injection laser bonded on silicon. It has a confinement factor in the active region larger than 40% for 1 ?m wide III/V active waveguide, which is the highest among all the other integration schemes proposed so far. An optical vertical interconnect access to transfer light efficiently between III/V and silicon layer is designed. The design of the shortest "Optical Via" of 4 ?m which gives ~100% coupling efficiency is presented.

Pu, Jing; Wang, Qian; Ho, Seng-Tiong

2013-02-01

222

Multi-band and broad-band infrared detectors based on III V materials for spectral imaging instruments  

NASA Astrophysics Data System (ADS)

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 (˜3 25 ?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.

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

2005-10-01

223

A novel application of the vertical gradient freeze method to the growth of high quality III-V crystals  

NASA Astrophysics Data System (ADS)

A new process for growing high-quality single crystals of the III-V compounds, based on the vertical gradient freeze methods, is described. The method features crystal growth in a boron nitride seeded crucible, with axial and radial thermal gradients that are much lower than in the conventional liquid encapsulated Czochralski technique. This method has been applied to grow large (50-mm diameter) low-dislocation-density crystals of CaAs, GaP, and InP for uses in optoelectronic and FET devices. In the 750-gg 111-line low-doped ultralow-defect-density seeded InP crystals, the radial uniformity was exceptional, and in silicon-doped 100-line GaAs, a dislocation density of less than 300/sq cm was achieved at low dopant levels. Equipment diagrams and characterization data are included.

Gault, W. A.; Monberg, E. M.; Clemans, J. E.

1986-04-01

224

Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors  

NASA Astrophysics Data System (ADS)

The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

Morelli, D. T.; Heremans, J. P.; Slack, G. A.

2002-11-01

225

Atomic-scale studies of nanometer-sized graphene on III-V semiconductors using scanning tunneling microscopy.  

NASA Astrophysics Data System (ADS)

We utilize the Dry Contact Transfer (DCT) method [1] to deposit nanometer-sized, monolayer graphene flakes, in situ, onto cleaved GaAs (110) and InAs (110) surfaces. The flakes were characterized using a homebuilt, room temperature, ultrahigh-vacuum scanning tunneling microscope. We report on the apparent electronic semi-transparency of the monolayer graphene flakes, such that the underlying III-V semiconductor lattice is revealed in our topographic images. This transparency is strongly dependent on the applied sample bias, similar to results seen on SiC (1000) for large sheets of graphene grown via thermal desorption [2]. [3pt] [1] P.M. Albrecht and J.W. Lyding, APL 83, 5029 (2003). [0pt] [2] G.M. Rutter et al, Phys. Rev. B 76, 235416 (2007).

He, Kevin; Koepke, Justin; Lyding, Joseph

2009-03-01

226

On-chip optical interconnection by using integrated III-V laser diode and photodetector with silicon waveguide.  

PubMed

On-chip integration of III-V laser diodes and photodetectors with silicon nanowire waveguides is demonstrated. Through flip-chip bonding of GaInNAs/GaAs laser diodes directly onto the silicon substrate, efficient heat dissipation was realized and characteristic temperatures as high as 132K were achieved. Spot-size converters for the laser-to-waveguide coupling were used, with efficiencies greater than 60%. The photodetectors were fabricated by bonding of InGaAs/InP wafers directly to silicon waveguides and formation of metal-semiconductor-metal structures, giving responsivities as high as 0.74 A/W. Both laser diode and the photodetector were integrated with a single silicon waveguide to demonstrate a complete on-chip optical transmission link. PMID:20720923

Ohira, Kazuya; Kobayashi, Kentaro; Iizuka, Norio; Yoshida, Haruhiko; Ezaki, Mizunori; Uemura, Hiroshi; Kojima, Akihiro; Nakamura, Kenro; Furuyama, Hideto; Shibata, Hideki

2010-07-19

227

Broadband microwave photonic fully tunable filter using a single heterogeneously integrated III-V/SOI-microdisk-based phase shifter.  

PubMed

A broadband microwave photonic phase shifter based on a single III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic silicon-on-insulator waveguide is reported. The phase shift tunability is accomplished by modifying the effective index through carrier injection. A comprehensive semi-analytical model aiming at predicting its behavior is formulated and confirmed by measurements. Quasi-linear and continuously tunable 2? phase shifts at radiofrequencies greater than 18 GHz are experimentally demonstrated. The phase shifter performance is also evaluated when used as a key element in tunable filtering schemes. Distortion-free and wideband filtering responses with a tuning range of ~100% over the free spectral range are obtained. PMID:22565703

Lloret, Juan; Morthier, Geert; Ramos, Francisco; Sales, Salvador; Van Thourhout, Dries; Spuesens, Thijs; Olivier, Nicolas; Fédéli, Jean-Marc; Capmany, José

2012-05-01

228

Nanostructuring of ultra-thin HfO2 layers for high-k/III-V device application.  

PubMed

We report on the nanopatterning by electron beam lithography (EBL) and reactive ion etching (RIE) in a SF6/Ar+ plasma of ultra-thin HfO2 films deposited on GaAs (001) substrates for gate oxide application in next generation III-V metal-oxide-semiconductor field effect transistors (MOSFETs). Characterization of the HfO2/GaAs nanostructured samples by atomic force microscopy (AFM), high-resolution scanning electron microscopy (HRSEM), energy-dispersive X-ray spectroscopy microanalysis (EDX) and transmission electron microscopy (TEM) has shown the formation of well defined HfO2 patterns with nanometre-scale linewidth control and anisotropic profiles. In addition, atomically smooth, stoichiometric and residue-free bottom GaAs etched lines with a lateral dimension of approximately 50 nm have been demonstrated. PMID:22400270

Benedicto, M; Anguita, J; Alvaro, R; Galiana, B; Molina-Aldereguia, J M; Tejedor, P

2011-10-01

229

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

NASA Astrophysics Data System (ADS)

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.

Hong, Songcheol

230

Solid-State Precursor Routes to Iii-V Type Electronic (13-15) and Magnetic (3-15) Materials  

NASA Astrophysics Data System (ADS)

An interest in electronic materials has led me to investigate new synthetic approaches to "III-V" type semiconducting (13-15, current IUPAC designation for B and N groups in the Periodic Table) and magnetic (3-15) compounds. It is now possible to prepare binary (GaAs and GdP) and ternary mixed-metal (Al_ {x}Ga_{1-x}As) and mixed -pnictide (rm GaP_{x}As_ {1-x}) compounds in seconds from rapid, low-temperature-initiated metathesis reactions between a metal (III) trihalide and a trisodium pnictide, exemplified by MX_3 + Na_3Pn to MPn + 3 NaX, where M is Al, Ga, In, (Al,Ga), or a lanthanide; X is F, Cl, or I; and Pn is P, As, Sb, or (P,As). The precursors are mixed together in a dry box and ignited by light grinding with a mortar and pestle, or by brief, local heating from a hot filament. These reactions are very exothermic (calculated Delta H_{rxn} (GaAs) = -138 kcal/mol) and typically reach temperatures in excess of 700^circ C within seconds of initiation, and cool to room temperature in less than 15 seconds. The byproduct sodium halide is simply removed by washing with water or methanol, leaving the polycrystalline "III-V" products. In spite of the brief and explosive nature of these reactions, there are some clues as to the initiation and reaction processes. The initial steps in the reactions appear to be the decomposition of the precursors and the formation of the sodium halides. Since initiation occurs when one of the precursors goes through a phase change, such as melting or decomposing, the melting points of the GaX_3 precursors are good indicators of how easily the reactions can be initiated. Physical methods have been employed to characterize the bulk products. The 13-15 materials have been investigated using MAS-NMR spectroscopy. The 3-15 compounds have been extensively studied using magnetometry, and the effectiveness of the metathesis processes was examined by comparing the ignition reaction products to those generated by direct combination of the elements at elevated temperatures. Both the 3-15 and 13-15 materials have been examined by SEM and EDS techniques.

Treece, Randolph Edward

231

Iii-V Compound Semiconductor Integrated Charge Storage Structures for Dynamic and Non-Volatile Memory Elements  

NASA Astrophysics Data System (ADS)

This thesis presents an investigation into a novel group of GaAs charge storage devices. These devices, which are an integration of bipolar and junction field effect transistor structures were conceived, designed, fabricated, and tested within this study. The purpose was to analyse new types of charge storage devices, which are suitable for fabrication and lead to the development of dynamic and nonvolatile memories in III-V compound semiconductors. Currently, III-V semiconductor storage devices consist only of capacitors, where data is destroyed during reading and electrical erasure is difficult. In this work, four devices types were demonstrated that exhibit nondestructive reading, and three of the prototypes can be electrically erased. All types use the junction field effect transistor (JFET) for charge sensing, with each having different bipolar or epitaxial layer structure controlling the junction gate. The bottom epitaxial layer in each case served as the JFET channel. Two of the device types have three alternately doped layers, while the remaining two have four alternately doped layers. In all cases, removal of majority carriers from the middle layers constitutes stored charge. The missing carriers deplete the current carrying a region of the JFET channel. Drain current of the JFET becomes an indicator of stored charge. The basic function of each JFET memory element type is independent of interchanging n- and p- type doping within the structure type. Some performance advantage can be realized, however, by sensing with an n-type channel as compared to p- type due to increased carrier mobility. All device types exhibit storage time characteristics of order ten seconds. Devices are constructed in epitaxial layers grown by molecular beam epitaxy (MBE) reactors. The design of the epitaxial layers is an intrinsic part, together with the electrical design, of the storage device concept. These concepts are implemented first with photolithography masks which are used in device fabrication. The fabrication methods employ wet chemical etching and ohmic metal liftoff techniques. Electrical dc and charge retention time characteristics along with functionality read/write operations for the memory element group are measured using commercial electronic test equipment.

Hetherington, Dale Laird

232

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

SciTech Connect

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.

Russell D. Dupuis

2004-09-30

233

Energy Harvesting Efficiency of III-V Multi-Junction Concentrator Solar Cells under Realistic Spectral Conditions  

NASA Astrophysics Data System (ADS)

A theoretical analysis on the spectral sensitivity of the bandgap design of four practical III-V triple-junction solar cell structures is presented. The underlying solar cell model uses the detailed balance method. Six locations on Earth are investigated for which the monthly average of the measured aerosol optical depth and the precipitable water are used to calculate direct solar spectra with a discretisation of one spectrum per hour. The model is used to analyze the solar cell designs for the highest yearly energy production. Furthermore, the ideal bandgap combination for a maximal energy harvest is calculated for each location. It is shown that the metamorphic solar cell structure of Ga0.35In0.65P/Ga0.83In0.17As/Ge with transparencies optimized for the standard AM1.5d reference spectrum leads to the highest energy harvesting efficiencies and shows the lowest spectral sensitivity. The standard lattice-matched structure of Ga0.50In0.50P/Ga0.99In0.01As/Ge shows the highest spectral sensitivity with up to 10.8%rel difference in the yearly energy harvesting.

Philipps, S. P.; Peharz, G.; Hoheisel, R.; Hornung, T.; Al-Abbadi, N. M.; Dimroth, F.; Bett, A. W.

2010-10-01

234

III-V on silicon: Observation of gallium phosphide anti-phase disorder by low-energy electron microscopy  

NASA Astrophysics Data System (ADS)

The formation of anti-phase disorder is a major obstacle in the heteroepitaxy of III-V semiconductors on silicon. For an investigation of the anti-phase domain (APD) structure of GaP/Si(100) samples on mesoscopic length scales, we applied dark-field imaging in a low-energy electron microscope (LEEM) to thin GaP films grown on Si(100) substrates by metal organic vapor phase epitaxy (MOVPE). A contamination-free transfer of the samples from the MOVPE ambient to the ultra-high vacuum chamber of the microscope ensured that the atomically well-ordered, P-rich (2 × 2)/c(4 × 2) reconstruction of the surface was preserved. Mutually perpendicular oriented domains of the characteristic GaP(100) reconstruction identify the APDs in the GaP film at the surface and enabled us to achieve high contrast LEEM images. Striped patterns of APDs reflect the regular terrasse structure of the two-domain Si(100)(2 × 1) substrate far away from defects. APDs in the proximity of the defects have larger lateral extensions and are arranged in target pattern-like structures around the defects. In contrast to transmission electron microscopy, which was also applied in a specific dark-field mode for comparison, the characterization of anti-phase disorder by LEEM is non-destructive, does not require elaborate sample preparation, and addresses extended length scales.

Döscher, Henning; Borkenhagen, Benjamin; Lilienkamp, Gerhard; Daum, Winfried; Hannappel, Thomas

2011-08-01

235

Soft-x-ray fluorescence spectra of III-V phosphides BP,GaP, and InP  

SciTech Connect

The valence band electronic structures of the III-V phosphides BP, GaP, and InP were investigated using soft x-ray fluorescence spectroscopy and compared with band structure calculations using full-potential linearized augmented plane wave method based on density functional theory. The P L{sub 2,3} spectra of these phosphorus compounds are reported and compared with the calculated (s+d)-local partial densities of states (LPDOS{close_quote}s). For BP, the B K spectrum is also reported. Generally good agreement is obtained between the spectra and calculated LPDOS{close_quote}s. Two other interesting results were found. The normally suppressed P L{sub 1} spectrum was observed in resonance with the B K spectrum of BP. Also, strong resonant inelastic x-ray scattering was observed at the Ga M{sub 2,3} edge associated with energy loss to local electronic excitations from the Ga d states, permitting the Ga d states to be accurately located with respect to other band features.

Lin, L.; Woods, G. T.; Callcott, T. A.

2001-06-15

236

New surface atomic structures for column V overlayers on the (110) surfaces of III-V compound semiconductors  

SciTech Connect

Two new minimum-energy surface structures have been identified for p(1 {times} 1) overlayers of Sb on the (110) surface of III-V compound semiconductors using a tight-binding total-energy formalism previously developed for these systems. The first is the commensurate chain'' structure in which Sb zig-zag chains are commensurate with, and on top of, the Ga--As unreconstructed surface zig-zag chains. This structure differs from the previously found epitaxial-chain structure by virtue of the registry of the Sb chains on top of'' rather than in between'' the substrate Ga--As chains. Like the epitaxial chain structure, it is compatible with both scanning tunneling microscopy (STM) and photoemission data. The second is an overlapping chain'' structure in which the Sb chains are 180{degree} out-of-phase with, and on top of, the Ga--As substrate chains. This structure is, however, incompatible with both low-energy-electron-diffraction and STM data for GaAs(110)-p(1 {times} 1)-Sb although it may be a possible structure for other systems. Computations for GaP(110)-p(1 {times} 1)-Sb and InSb(110)- p(1 {times} 1)-Sb reveal that the energy difference between the commensurate chain and traditional epitaxial structure is approximately constant over this range of overlayer/substrate lattice mismatch. 16 ref., 8 figs., 3 tabs.

LaFemina, J.P. (Pacific Northwest Lab., Richland, WA (USA)); Duke, C.B. (Xerox Corp., Webster, NY (USA). Webster Research Center); Mailhiot, C. (Lawrence Livermore National Lab., CA (USA))

1990-02-01

237

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

SciTech Connect

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)

Fowler, Bruce A. [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); ATSDR, Atlanta, Georgia (United States)], E-mail: bxf9@cdc.gov; Conner, Elizabeth A. [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); NCI, Bethesda, Maryland (United States); Yamauchi, Hiroshi [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); Kitasato University (Japan)

2008-11-15

238

Electrocatalytic oxygen evolution from water on a Mn(III-V) dimer model catalyst--a DFT perspective.  

PubMed

A complete water oxidation and oxygen evolution reaction (OER) cycle is monitored by means of density functional theory (DFT). A biomimetic model catalyst, comprising a ?-OH bridged Mn(III-V) dimer truncated by acetylacetonate ligand analogs and hydroxides is employed. The reaction cycle is divided into four electrochemical hydrogen abstraction steps followed by a series of chemical steps. The former employ the tyrosine/tyrosyl redox couple acting as electron and proton sink, thus determining the reference potential. Stripping hydrogen from water leads to the formation of two highly unstable Mn(V)=O/Mn(IV)-O? moieties, which subsequently combine to form a ?-peroxy O-O bond. O(2) evolution results from subsequent consecutive replacement of the remaining Mn-O bonds by water. A Zener "spintronic" type mechanism for virtually barrierless O(2) evolution is found. The applicability of DFT is discussed and extended to include the rate-limiting steps in the OER. Rather than attempting to compute transition states where KS-DFT is unreliable, an upper bound for the activation barrier of the O-O bond formation step is estimated from the hessians of the relevant intermediates. PMID:21773630

Busch, M; Ahlberg, E; Panas, I

2011-07-20

239

Response properties of III-V dilute magnetic semiconductors including disorder, dynamical electron-electron interactions, and band structure effects  

NASA Astrophysics Data System (ADS)

A theory of the electronic response in spin and charge disordered media is developed with the particular aim to describe III-V dilute magnetic semiconductors like Ga1-xMnxAs. The theory combines a detailed k·p description of the valence-band, in which the itinerant carriers are assumed to reside, with first-principles calculations of disorder contributions using an equation-of-motion approach for the current response function. A fully dynamic treatment of electron-electron interaction is achieved by means of time-dependent density-functional theory. It is found that collective excitations within the valence-band significantly increase the carrier relaxation rate by providing effective channels for momentum relaxation. This modification of the relaxation rate, however, has only a minor impact on the infrared optical conductivity in Ga1-xMnxAs, which is mostly determined by the details of the valence-band structure and found to be in agreement with experiment.

Kyrychenko, F. V.; Ullrich, C. A.

2011-05-01

240

Are Electro-Luminescence Defects in Concentrator Iii-V Cells Responsible to Thermal Runaway and Sudden Death?  

NASA Astrophysics Data System (ADS)

Two types of failure of III-V cells in CPV system by Daido Steel have been observed. One is thermal runaway and another is what we call a electrical shock. This paper will discuss on the frequency of the cell failure seen in a field and on experiments to determine the root cause of thermal runaway. Failures by the electrical shock were not related to thermal runaway, and a packaging solution to the failure by the electrical shock was found which will be published at another time. A detailed investigation of 30 kW field was undertaken to identify failed cells. After the other failure mechanism has been removed, experiments can be conducted on thermal runaway. Thermal runaway can occur due to loss of thermal conduction, such as voids or discontinuities in the thermal interchange material bonding cell to heat sink. It has been hypothesized that thermal runaway can also occur at location of cell defects as identified by electroluminescence. So far it we have not been able to induce thermal runaway at locations of electroluminescence defects.

Araki, Kenji; Al Taher, Omar; Nagai, Hirokazu; Hebert, Peter; Valles, Juan

2011-12-01

241

Superconductivity in low-temperature grown III-V thin films. Final report, 15 June 1992-31 May 1995  

SciTech Connect

In this AASERT project, the authors studied the electronic properties of various low-temperature grown III-V thin films using both optical and electrical characterization techniques. The previously found superconductivity effect could be ascribed to inclusions of group-III elements that were not related to the low-temperature growth conditions. The results found here indicate that the anion antisite, As{sub Ga} dominates the properties of LT-GaAs. This finding will allow future improvements in LT-GaAs by designing optimized concentrations of As{sub Ga} related deep levels for specific applications. In LT-AlGaAs, the very deep arsenic antisite level leads to the formation of layers with very high resistivity. In LT-InP and possibly in LT-InAlAs, the energy location of the anion antisite defects prevents the formation of highly resistive, undoped layers. With MCDA, the authors were able to directly prove that LT InP is highly n-type due to P{sub In} antisite defects, and to suggest which transitions form the magnetic circular dichroism spectrum for this defect.

Weber, E.R.

1996-01-01

242

Faceting, composition and crystal phase evolution in III-V antimonide nanowire heterostructures revealed by combining microscopy techniques.  

PubMed

III-V antimonide nanowires are among the most interesting semiconductors for transport physics, nanoelectronics and long-wavelength optoelectronic devices due to their optimal material properties. In order to investigate their complex crystal structure evolution, faceting and composition, we report a combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning tunneling microscopy (STM) study of gold-nucleated ternary InAs/InAs(1-x)Sb(x) nanowire heterostructures grown by molecular beam epitaxy. SEM showed the general morphology and faceting, TEM revealed the internal crystal structure and ternary compositions, while STM was successfully applied to characterize the oxide-free nanowire sidewalls, in terms of nanofaceting morphology, atomic structure and surface composition. The complementary use of these techniques allows for correlation of the morphological and structural properties of the nanowires with the amount of Sb incorporated during growth. The addition of even a minute amount of Sb to InAs changes the crystal structure from perfect wurtzite to perfect zinc blende, via intermediate stacking fault and pseudo-periodic twinning regimes. Moreover, the addition of Sb during the axial growth of InAs/InAs(1-x)Sb(x) heterostructure nanowires causes a significant conformal lateral overgrowth on both segments, leading to the spontaneous formation of a core-shell structure, with an Sb-rich shell. PMID:22322440

Xu, Tao; Dick, Kimberly A; Plissard, Sébastien; Nguyen, Thanh Hai; Makoudi, Younes; Berthe, Maxime; Nys, Jean-Philippe; Wallart, Xavier; Grandidier, Bruno; Caroff, Philippe

2012-02-10

243

Analytical description of the metal-assisted growth of III-V nanowires: Axial and radial growths  

SciTech Connect

The growth of III-V nanowires from metal seed particles is described in an analytical manner within the framework of a material conservation model. Direct impingement of growth species on the particle, coupled to their diffusion from the sidewall and the substrate surface, are considered in the derivation of expressions for the time evolution of both axial and radial growths. Two regimes are distinguished: the structure originally grows in a purely axial manner until its length exceeds the diffusion length of adatoms incoming from the substrate, at which point sidewall nucleation is triggered, resulting in a shell expanding radially in the lower part of the wire. Factors that take into account the nonunity probability of inclusion of group III adatoms in the axially growing crystal are introduced. Moreover, a step-mediated growth is included to describe the axial evolution of the shell. The numerical values of the various parameters were assessed by fitting the model to experimental data on the morphology evolution of molecular-beam-epitaxy-grown GaAs and InAs nanowires.

Plante, Martin C.; LaPierre, Ray R. [Department of Engineering Physics, Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2009-06-01

244

Generalized Valence-Force-Field Model of (Ga,In)(N,P) Ternary Alloys  

SciTech Connect

We present a generalized valence-force-field (VFF) model for the ternary III-V alloys (III=Ga, In and V=N, P) to predict the formation energies and atomic structures of ordered and disordered alloy configurations. For each alloy (GaInN, GaInP, GaNP, and InNP) the VFF parameters, which include bond-angle/bond-length interactions, are fitted to the first-principles calculated formation energies of 30 ternary structures. Compared to standard approaches where the VFF parameters are transferred from the individual binary III-V compounds, our generalized VFF approach predicts alloy formation energies and atomic structures with considerably improved accuracy. Using this generalized approach and random realizations in large supercells (4096 atoms), we determine the temperature-composition phase diagram, i.e., the binodal and spinodal decomposition curves, of the (Ga, In) (N, P) ternary alloys.

Biswas, K.; Franceschetti, A.; Lany, S.

2008-01-01

245

Suitability of III-V [XH4][YH4] materials for hydrogen storage: A density functional study  

NASA Astrophysics Data System (ADS)

In the search for novel hydrogen storage media, the III-V hydridic material [NH4][BH4] is a natural candidate. It can store a high wt% of hydrogen and has a favorable volumetric density. Unfortunately it was found to decompose slowly at room temperature. It is of interest to consider chemically related materials, such as the series of [XH4][YH4] ionic solids ( X=B ,Al,Ga and Y=N ,P,As). Even if the wt% of hydrogen in the heavier congeners is necessarily lower, they might offer superior material properties, notably higher (but not too high) stability. We have therefore performed a first-principles investigation of the cohesive energies of the XH4YH4 solid-state materials. In addition we have analyzed the bond character and energy within the building blocks of these materials, the XH4- and YH4+ molecular ions, including a comparison to the AH4 molecules (A=C,Si,Ge) . The calculations have been performed within the density functional framework employing plane waves for the bulk materials and Slater-type functions for the molecules. A detailed study of the electronic structure reveals that the hydrides of the light (second period) elements, BH4- , CH4 , and NH4+ , exhibit the strongest and shortest X-H bonds. This is caused by Pauli repulsion effects of the hydrogen substituents with the larger cores of the heavier (third and fourth period) elements. The important consequence is that in the crystals, where the ionic hydrides retain their identity and charge, the distance between the negative and positive ions is larger in the heavier systems, hence less Madelung stabilization and a smaller cohesive energy. Moving from [NH4][BH4] to heavier congeners thus does not seem to be a promising route to obtain more suitable materials for hydrogen storage. Other types of chemical variation (different substituents) on the [NH4][BH4] building blocks may prove more advantageous.

Zuliani, Filippo; Götz, Andreas W.; Guerra, Célia Fonseca; Baerends, Evert Jan

2009-04-01

246

Misfit dislocation formation in lattice-mismatched III - V heterostructures grown by metal - organic vapour phase epitaxy  

NASA Astrophysics Data System (ADS)

Misfit dislocation formation in lattice-mismatched III - V heterostructures both under tensile and under compressive stress has been studied. Layers of GaAs under tensile stress have been grown by metal - organic vapour phase epitaxy on 0022-3727/29/12/004/img1 substrates with indium concentrations between 0.1 and 1.1%. Compressively strained 0022-3727/29/12/004/img1 layers with indium concentrations between 0.5 and 2.5% have been grown on GaAs substrates. For the layers under tensile stress an asymmetrical dislocation pattern has been observed, whereas the compressively strained layers show a symmetrical dislocation pattern. A model describing the relaxation process by the formation of dissociated hexagonally shaped half-loop dislocations is proposed. A difference in the mobilities of the two possible misfit dislocation types is found to be the origin of asymmetrical strain relief at low growth temperatures. In layers under tensile stress the cross slipping of screw dislocations is counteracted by the shear stress, leading to relaxation in only one direction. In layers under compressive stress the nucleated misfit dislocations can undergo cross slipping, resulting in a cross hatched pattern at the surface. At higher growth temperatures the dislocation patterns become more symmetrical due to the higher dislocation mobilities. Growth hillocks are formed on the surfaces of the layers grown under tensile stress, due to local accumulation of dislocations. This hillock growth is prevented at higher growth temperatures by the higher mobility of the dislocations. It is also shown that the (mis)orientation of the substrate is revealed by non-parallel groups of dislocation lines observed at the surface of a relaxed epilayer.

te Nijenhuis, J.; van der Wel, P. J.; van Eck, E. R. H.; Giling, L. J.

1996-12-01

247

Secondary-ion emission from III-V semiconductive materials under MeV-energy heavy-ion bombardment  

NASA Astrophysics Data System (ADS)

Secondary-ion emission from III-V semiconductive chemical compounds (InP, InAs, and InSb) has been experimentally studied at heavy-ion energies from 0.5to5.0MeV , where electronic collision is a dominant process. Various secondary ions such as large cluster ions and atomic ions were observed. Yields of In atomic and cluster ions depend scantly on the incident energy, and those of group-V atomic ions and of cluster ions containing group-V elements can be expressed by an exponential function of Se-1 , where Se is the electronic stopping power. This fact shows that the ionization probabilities of the atoms and the clusters whose ionization potentials are higher than the work functions of target materials are increased by transient electronic excitation induced by ion bombardment. The energy distributions of the atomic ions show that the singly charged atomic ions are emitted through the linear collision cascade process even at MeV incident energies, and the multiply charged ions are produced by a projectile-induced simultaneous process of ionization and recoiling of atoms on the target surface. The yield dependences of the cluster ions on the electronic stopping power and on the cluster size are so much different from those for SiO2 . This fact precludes the multiple-bond-breaking process applied to the insulating material. Structural instabilities caused by high-density electronic excitations, which are known to take place in GaAs irradiated by slow multiply charged ions or lasers, are a possible cause of the cluster-ion emission from the semiconductive compounds at the MeV energy range.

Ninomiya, Satoshi; Imada, Chikage; Nagai, Masafumi; Nakata, Yoshihiko; Imanishi, Nobutsugu

2004-10-01

248

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

PubMed

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

Hyun, Seunghun; Lee, Linda S

2013-09-17

249

Self-aligned, extremely high frequency III-V metal-oxide-semiconductor field-effect transistors on rigid and flexible substrates.  

PubMed

This paper reports the radio frequency (RF) performance of InAs nanomembrane transistors on both mechanically rigid and flexible substrates. We have employed a self-aligned device architecture by using a T-shaped gate structure to fabricate high performance InAs metal-oxide-semiconductor field-effect transistors (MOSFETs) with channel lengths down to 75 nm. RF measurements reveal that the InAs devices made on a silicon substrate exhibit a cutoff frequency (f(t)) of ?165 GHz, which is one of the best results achieved in III-V MOSFETs on silicon. Similarly, the devices fabricated on a bendable polyimide substrate provide a f(t) of ?105 GHz, representing the best performance achieved for transistors fabricated directly on mechanically flexible substrates. The results demonstrate the potential of III-V-on-insulator platform for extremely high-frequency (EHF) electronics on both conventional silicon and flexible substrates. PMID:22746202

Wang, Chuan; Chien, Jun-Chau; Fang, Hui; Takei, Kuniharu; Nah, Junghyo; Plis, E; Krishna, Sanjay; Niknejad, Ali M; Javey, Ali

2012-07-03

250

An Investigation into III-V Compounds to Reach 20% Efficiency with Minimum Cell Thickness in Ultrathin-Film Solar Cells  

NASA Astrophysics Data System (ADS)

III-V single-junction solar cells have already achieved very high efficiency levels. However, their use in terrestrial applications is limited by the high fabrication cost. High-efficiency, ultrathin-film solar cells can effectively solve this problem, as their material requirement is minimum. This work presents a comparison among several III-V compounds that have high optical absorption capability as well as optimum bandgap (around 1.4 eV) for use as solar cell absorbers. The aim is to observe and compare the ability of these materials to reach a target efficiency level of 20% with minimum possible cell thickness. The solar cell considered has an n-type ZnSe window layer, an n-type Al0.1Ga0.9As emitter layer, and a p-type Ga0.5In0.5P back surface field (BSF) layer. Ge is used as the substrate. In the initial design, a p-type InP base was sandwiched between the emitter and the BSF layer, and the design parameters for the device were optimized by analyzing the simulation outcomes with ADEPT/F, a one-dimensional (1D) simulation tool. Then, the minimum cell thickness that achieves 20% efficiency was determined by observing the efficiency variation with cell thickness. Afterwards, the base material was changed to a few other selected III-V compounds, and for each case, the minimum cell thickness was determined in a similar manner. Finally, these cell thickness values were compared and analyzed to identify more effective base layer materials for III-V single-junction solar cells.

Haque, K. A. S. M. Ehteshamul; Galib, Md. Mehedi Hassan

2013-10-01

251

A Physics-Based Compact Model of III–V FETs for Digital Logic Applications: Current–Voltage and Capacitance–Voltage Characteristics  

Microsoft Academic Search

A physics-based analytical compact model of InGaAs field-effect transistors (FETs) for digital logic applications is developed. This model neither heavily depends on parameter extraction nor requires any time-consuming computation while capturing the essential physics, enabling digital circuit design and circuit-level performance estimation for III-V FETs. The model captures short channel effects, trapezoidal-shape quantum-well energies, bias-dependent ballistic ratios, and capacitances including

Saeroonter Oh; H.-S. Philip Wong

2009-01-01

252

Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors  

NASA Astrophysics Data System (ADS)

Scattering amplitudes taking into account the redistribution of charge due to bonds and corresponding correction factors considering the effect of static atomic displacements were computed using density functional theory and the empirical Keating model for ternary III-V and II-VI semiconductors in different strain states. Polynomials were fitted to the scattering amplitudes and the correction factors as a function of the composition of the ternary semiconductors.

Schowalter, M.; Mueller, K.; Rosenauer, A.

2012-01-01

253

Distinct antinociceptive actions mediated by different opioid receptors in the region of lamina I and laminae III-V of the dorsal horn of the rat.  

PubMed Central

1. In view of the presence of mu, delta and kappa opioid receptors in the spinal dorsal horn and their apparent involvement in behavioural analgesia, the present experiments addressed the action of selective agonists ionophoresed in the vicinity of rat dorsal horn neurones which were located either in lamina I or in laminae III-V. 2. In laminae III-V, kappa agonists (U50488H and dynorphin A) caused a selective inhibition of the nociceptive responses of multireceptive cells, whilst mu and delta agonists [( D-Ala2, MePhe4, Gly-ol]enkephalin and [D-Pen2, D-Pen5]enkephalin respectively) failed to alter either the spontaneous activity or the response to noxious and innocuous cutaneous stimuli and to D,L-homocysteic acid or glutamate. Nocispecific neurones were encountered too rarely in laminae III-V to study their properties. 3. In lamina I, agonists had no effects on either nocispecific or multireceptive neurones. In contrast, the mu agonist [D-Ala2, MePhe4, Gly-ol]enkephalin consistently inhibited nociceptive responses of both multireceptive and nocispecific lamina I cells. The delta agonist [D-Pen2, D-Pen5]enkephalin consistently caused selective inhibition of the nociceptive responses of multireceptive cells but had a mixed profile of action on nocispecific cells. 4. These results suggest that mu, delta and kappa opioid receptors mediate different antinociceptive actions in both laminae III-V and lamina I. The study reveals a distinct physiological role for delta receptors in modulating nociceptive inputs to lamina I neurones. In contrast to mu and kappa receptor actions, delta receptors heterogeneously influence subpopulations of neurones.

Hope, P. J.; Fleetwood-Walker, S. M.; Mitchell, R.

1990-01-01

254

Influence of PH3 exposure on silicon substrate morphology in the MOVPE growth of III–V on silicon multijunction solar cells  

NASA Astrophysics Data System (ADS)

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III–V materials on silicon for photovoltaic applications. One of the first issues to be considered in the development of this structure will be the strategy to create the silicon emitter of the bottom subcell. In this study, we explore the possibility of forming the silicon emitter by phosphorus diffusion (i.e. exposing the wafer to PH3 in a MOVPE reactor) and still obtain good surface morphologies to achieve a successful III–V heteroepitaxy as occurs in conventional III–V on germanium solar cell technology. Consequently, we explore the parameter space (PH3 partial pressure, time and temperature) that is needed to create optimized emitter designs and assess the impact of such treatments on surface morphology using atomic force microscopy. Although a strong degradation of surface morphology caused by prolonged exposure of silicon to PH3 is corroborated, it is also shown that subsequent anneals under H2 can recover silicon surface morphology and minimize its RMS roughness and the presence of pits and spikes.

García-Tabarés, E.; García, I.; Martín, D.; Rey-Stolle, I.

2013-11-01

255

TOPICAL REVIEW: The shallow-to-deep instability of hydrogen and muonium in II VI and III V semiconductors  

NASA Astrophysics Data System (ADS)

The structure and electrical activity of monatomic hydrogen defect centres are inferred from the spectroscopy and charge-state transitions of muonium, the light pseudo-isotope of hydrogen. Introductions are given to all these topics. Special attention is paid to the shallow-donor behaviour recently established in a number of II VI compounds and one III nitride. This contrasts with trapped-atom states suggestive of an acceptor function in other members of the II VI family as well as with the deep-level amphoteric behaviour which has long been known in the elemental group-IV semiconductors and certain III V compounds. The systematics of this remarkable shallow-to-deep instability are examined in terms of simple chemical considerations, as well as current theoretical and computational models. The muonium data appear to confirm predictions that the switch from shallow to deep behaviour is governed primarily by the depth of the conduction-band minimum below the vacuum continuum. The threshold electron affinity is around 3.5 eV, which compares favourably with computational estimates of a so-called pinning level for hydrogen (+/-) charge-state transitions of between -3 and -4.5 eV. A purely ionic model gives some intuitive understanding of this behaviour as well as the invariance of the threshold. Another current description applies equally to covalent materials and relates the threshold to the origin of the electrochemical scale. At the present level of approximation, zero-point energy corrections to the transition levels are small, so that muonium data should provide a reliable guide to the behaviour of hydrogen. Muonium spectroscopy proves to be more sensitive to the (0/+) donor level than to the (+/-) pinning level but, as a tool which does not rely on favourable hydrogen solubility, it looks set to test further predictions of these models in a large number of other materials, notably oxides. Certain candidate thin-film insulators and high-permittivity gate dielectrics appear to be uncomfortably close to conditions in which hydrogen impurity may cause electronic conduction.

Cox, S. F. J.

2003-11-01

256

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

NASA Astrophysics Data System (ADS)

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.

Jafri, Ijaz Hussain

257

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors  

SciTech Connect

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III-V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown crystals and epilayers are reproduced by the model. It extends an earlier study [Hurle, J. Appl. Phys. 85, 6957 (1999)] devoted solely to GaAs. Values for the enthalpy and entropy of formation of both native and dopant related point defects are obtained by fitting to experimental data. In undoped material, vacancies, and interstitials on the Group V sublattice dominate in the vicinity of the melting point (MP) in both the phosphides and arsenides, whereas, in the antimonides, vacancies on both sublattices dominate. The calculated concentrations of the native point defects are used to construct the solidus curves of all the compounds. The charged native point defect concentrations at the MP in four of the six materials are significantly higher than their intrinsic carrier concentrations. Thus the usually assumed high temperature 'intrinsic' electroneutrality condition for undoped material (n=p) is not valid for these materials. In GaSb, the Ga{sub Sb} antisite defect appears to be grown-in from the melt. This contrasts with the As{sub Ga} defect in GaAs for which the concentration grown-in at the MP is negligibly small. Compensation of donor-doped material by donor-Group III vacancy complexes is shown to exist in all the compounds except InP where Group VI doped crystals are uncompensated and in InSb where there is a lack of experimental data. The annealing effects in n{sup +} GaAs, including lattice superdilation, which were shown in the earlier paper to be due to Group III vacancy undersaturation during cooling, are found to be present also in GaSb and InAs. Results for native point defects are compared with reported ''first principles'' calculations for GaAs. It is seen that, while there is some accord with experimental findings for low temperature molecular beam epitaxial (MBE) growth, they fail totally to predict the behavior under high temperature growth conditions. The analysis of data on liquid phase epitaxy (LPE) growth of GaAs from Bi solution in the earlier paper has been re-calculated in the light of experimental data that showed that the model used in that paper to represent the Ga-As-Bi phase equilibria was inadequate. An improved model reveals that Ga vacancies exert a greater effect in controlling the extent of the linear range of donor dopant solubility than previously predicted. It has also led to a re-evaluation of the equilibrium EL2 and Ga vacancy concentrations in GaAs during MBE growth under As-rich conditions at low temperatures ({approx}500 K). The amended model predicts that the very high concentrations of EL2 and of Ga vacancies observed experimentally are near equilibrium values. The predicted increase in the equilibrium concentrations of these defects at low temperatures results from coulombic attraction between the two defects. At temperatures somewhat lower than 500 K the rate of increase becomes catastrophic.

Hurle, D. T. J. [Scotscraig House, Storridge, Malvern, Worcestershire WR13 5EY (United Kingdom)

2010-06-15

258

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors  

NASA Astrophysics Data System (ADS)

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III-V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown crystals and epilayers are reproduced by the model. It extends an earlier study [Hurle, J. Appl. Phys. 85, 6957 (1999)] devoted solely to GaAs. Values for the enthalpy and entropy of formation of both native and dopant related point defects are obtained by fitting to experimental data. In undoped material, vacancies, and interstitials on the Group V sublattice dominate in the vicinity of the melting point (MP) in both the phosphides and arsenides, whereas, in the antimonides, vacancies on both sublattices dominate. The calculated concentrations of the native point defects are used to construct the solidus curves of all the compounds. The charged native point defect concentrations at the MP in four of the six materials are significantly higher than their intrinsic carrier concentrations. Thus the usually assumed high temperature ``intrinsic'' electroneutrality condition for undoped material (n=p) is not valid for these materials. In GaSb, the GaSb antisite defect appears to be grown-in from the melt. This contrasts with the AsGa defect in GaAs for which the concentration grown-in at the MP is negligibly small. Compensation of donor-doped material by donor-Group III vacancy complexes is shown to exist in all the compounds except InP where Group VI doped crystals are uncompensated and in InSb where there is a lack of experimental data. The annealing effects in n+ GaAs, including lattice superdilation, which were shown in the earlier paper to be due to Group III vacancy undersaturation during cooling, are found to be present also in GaSb and InAs. Results for native point defects are compared with reported ``first principles'' calculations for GaAs. It is seen that, while there is some accord with experimental findings for low temperature molecular beam epitaxial (MBE) growth, they fail totally to predict the behavior under high temperature growth conditions. The analysis of data on liquid phase epitaxy (LPE) growth of GaAs from Bi solution in the earlier paper has been re-calculated in the light of experimental data that showed that the model used in that paper to represent the Ga-As-Bi phase equilibria was inadequate. An improved model reveals that Ga vacancies exert a greater effect in controlling the extent of the linear range of donor dopant solubility than previously predicted. It has also led to a re-evaluation of the equilibrium EL2 and Ga vacancy concentrations in GaAs during MBE growth under As-rich conditions at low temperatures (~500 K). The amended model predicts that the very high concentrations of EL2 and of Ga vacancies observed experimentally are near equilibrium values. The predicted increase in the equilibrium concentrations of these defects at low temperatures results from coulombic attraction between the two defects. At temperatures somewhat lower than 500 K the rate of increase becomes catastrophic.

Hurle, D. T. J.

2010-06-01

259

Wet chemical functionalization of III-V semiconductor surfaces: alkylation of gallium phosphide using a Grignard reaction sequence.  

PubMed

Single-crystalline gallium phosphide (GaP) surfaces have been functionalized with alkyl groups via a sequential Cl-activation, Grignard reaction process. X-ray photoelectron (XP) spectra of freshly etched GaP(111)A surfaces demonstrated reproducible signals for surficial Cl after treatment with PCl(5) in chlorobenzene. The measured Cl content consistently corresponded to approximately a monolayer of coverage on GaP(111)A. In contrast, GaP(111)B surfaces treated with the same PCl(5) solution under the same conditions exhibited macroscale roughening and yielded XP spectra that showed irreproducible Cl surface content often below the limit of detection of the spectrometer. The Cl-activated GaP(111)A surfaces were reactive toward alkyl Grignard reagents. Sessile contact angle measurements between water and GaP(111)A after various levels of treatment showed that GaP(111)A surfaces became significantly more hydrophobic following reaction with either CH(3)MgCl or C(18)H(37)MgCl. GaP(111)A surfaces reacted with C(18)H(37)MgCl demonstrated wetting properties consistent with surfaces modified with a dense layer of long alkyl chains. High-resolution C 1s XP spectra indicated that the carbonaceous species at GaP(111)A surfaces treated with Grignard reagents could not be ascribed solely to adventitious carbon. A shoulder in the C 1s XP spectra occurred at slightly lower binding energies for these samples, commensurate with the formation of Ga-C bonds. High-resolution P 2p XP spectra taken at various times during prolonged direct exposure to ambient laboratory air indicated that the resistance of GaP(111)A to surface oxidation was greatly enhanced after surface modification with alkyl groups. GaP(111)A samples that had been functionalized with C(18)H(37)- groups exhibited less than 0.1 nm of surface oxide after 7 weeks of continuous exposure to ambient air. GaP(111)A surfaces terminated with C(18)H(37)- groups were also used as platforms in Schottky heterojunctions with Hg. In comparison to freshly etched GaP(111)A, the alkyl-terminated GaP(111)A samples yielded current-voltage responses that were in accord with metal-insulator-semiconductor devices and indicated that this reaction strategy could be used to alter rates of heterogeneous charge transfer controllably. The wet chemical surface functionalization strategy described herein does not involve thiol/sulfide chemistry or gas-phase pretreatments and represents a new synthetic methodology for controlling the interfacial properties of GaP and related Ga-based III-V semiconductors. PMID:20486651

Mukherjee, Jhindan; Peczonczyk, Sabrina; Maldonado, Stephen

2010-07-01

260

Basic moments of phonon density of states spectra and characteristic phonon temperatures of group IV, III–V, and II–VI materials  

Microsoft Academic Search

We have redigitized a large variety of phonon density of states (PDOS) spectra, that have been published by diferent researchers for group IV (diamond, 3C-SiC, Si, and Ge), III–V (BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb), and II–VI materials (ZnO, ZnS, ZnSe, ZnTe, CdS, and CdTe), including calculations of their

2007-01-01

261

Basic moments of phonon density of states spectra and characteristic phonon temperatures of group IV, III-V, and II-VI materials  

Microsoft Academic Search

We have redigitized a large variety of phonon density of states (PDOS) spectra, that have been published by diferent researchers for group IV (diamond, 3C-SiC, Si, and Ge), III-V (BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb), and II-VI materials (ZnO, ZnS, ZnSe, ZnTe, CdS, and CdTe), including calculations of their

Roland Pässler

2007-01-01

262

Hyperfine Interactions and Magnetism of 3d Transition-Metal-Impurities in II–VI and III–V Compound-Based Diluted Magnetic Semiconductors  

Microsoft Academic Search

The electronic structure of II–VI and III–V compound-based diluted magnetic semiconductors is calculated based on the local\\u000a density approximation (LDA) using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation. The\\u000a magnetism of 3d transition-metal-atom-doped ZnO, ZnS, ZnSe, ZnTe, GaN, GaAs is investigated from first-principles. It is suggested\\u000a that the double exchange mechanism stabilizes the ferromagnetism in these DMSs. In

K. Sato; H. Katayama-Yoshida

2001-01-01

263

New surface atomic structures for III-V(110)-p(1 times 1)-Sb(1ML): Chemical bonding and electronic structure  

SciTech Connect

Tight-binding total energy computations are used to examine the chemical bonding and electronic structure for two new minimum-energy surface atomic structures for p(1{times}1) overlayers of Sb on III-V(110) surfaces. The bonding in each of these structures is unique, having no analog in either the bulk or small molecule coordination chemistry of these materials, and is a phenomena uniquely associated with the constrained epitaxical growth of the Sb overlayer. 13 refs., 2 figs., 2 tabs.

LaFemina, J.P. (Pacific Northwest Lab., Richland, WA (USA)); Duke, C.B. (Xerox Corp., Webster, NY (USA). Webster Research Center); Mailhiot, C. (Lawrence Livermore National Lab., CA (USA))

1990-04-01

264

Correlation between energy positions of deep intrinsic point-defect levels and a limiting fermi level in irradiated III V semiconductors  

NASA Astrophysics Data System (ADS)

The energy levels of neutral anion (VA) and cation (VC) vacancies and antisite defects are calculated for the anion CA and cation AC sublattices of III V semiconductors. An averaged energy level position for these defects is estimated to be Eav abs = 4.9 eV. The position coincides with the local charge electroneutrality level. It is shown that the case, where the total energies of formation of VA, VC and antisite CA, AC defects in the sublattices of binary semiconductors are similar, corresponds to the point-defect equilibrium condition and stabilization of the Fermi level in the proximity of the local charge electroneutrality level.

Brudnyi, V. N.; Grinyaev, S. N.; Kolin, N. G.

2007-05-01

265

Ab-initio Calculation of Zero-Field Spin Splitting in Heterostructures of III-V and II-VI Semiconductors.  

NASA Astrophysics Data System (ADS)

We have developed a fully relativistic ab-initio transport method within the Linear Muffin Tin Orbitals (LMTO) Principal Layer Green Function framework. The calculated spin orbit induced band splittings of several III- V and II-IV bulk semiconductors are in excellent agreement with a well tested perturbative approach, as well as with previous fully relativistic results and available experimental data. The orbital magnetic moment of several 3d transition metals are also in excellent agreement with the perturbative approach and previous fully relativistic results. The method is used for a first principles investigation of Rashba and Dresselhaus effects in III-V and II-VI compounds asymmetric quantum wells, double barrier and single barrier heterostructures. The magnitude and ratio of the two effects determine the spin scattering ratio and anisotropy in quantum wells. These quantites are also important for the construction of spin modulators. With the present method periodic boundary conditions are not required; thus electric fields can be applied without the need for Berry phases. It is possible to obtain reliable values from first principles for a wide variety of geometries, and to clearly distinguish the Dresselhaus and Rashba contributions. The progress of the work and several results will be reported.

Chantis, Athanasios; Antropov, Vladimir

2005-03-01

266

Interdiffused Multilayer Processing (IMP) in alloy growth  

NASA Astrophysics Data System (ADS)

The Interdiffused Multilayer Processing (IMP) technique has been developed as a way of growing uniform layers of cadmium mercury telluride (CMT). The principle of the technique is discussed in the context of an interdiffusion coefficient so as to assess the potential applicability of the technique to the growth of other II-VI or III-V alloys. The development of IMP for the growth of CMT layers, together with the properties of the layers and their suitability for use in the fabrication of IR detectors, is reviewed.

Mullin, J. B.; Giess, J.; Irvine, S. J. C.; Gough, J. S.; Royle, A.

267

Hyperfine Interactions and Magnetism of 3d Transition-Metal-Impurities in II-VI and III-V Compound-Based Diluted Magnetic Semiconductors  

NASA Astrophysics Data System (ADS)

The electronic structure of II-VI and III-V compound-based diluted magnetic semiconductors is calculated based on the local density approximation (LDA) using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation. The magnetism of 3d transition-metal-atom-doped ZnO, ZnS, ZnSe, ZnTe, GaN, GaAs is investigated from first-principles. It is suggested that the double exchange mechanism stabilizes the ferromagnetism in these DMSs. In order to obtain microscopic information on the electronic structure of transition-metal-impurities in semiconductors, the hyperfine field of respective impurities in each host material is calculated. It is found that the agreement with the experimental values is not good, probably because the LDA is not sufficient to describe the core states of transition metals. However, it is suggested that the hyperfine fields clearly reflect the local magnetic moments for 3d impurities.

Sato, K.; Katayama-Yoshida, H.

2001-11-01

268

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)

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.

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

2011-05-01

269

Characterization of molecular nitrogen in III-V compound semiconductors by near-edge x-ray absorption fine structure and photoemission spectroscopies  

SciTech Connect

Formation of molecular nitrogen under low-energy nitrogen bombardment of III-V compound semiconductor surfaces has been studied by photoemission spectroscopy around N 1s core-level and near-edge x-ray absorption fine structure (NEXAFS) around N K edge. Interstitial molecular nitrogen N{sub 2} has been formed in all of the samples under consideration. The presence of N{sub 2} produces a sharp resonance in low-resolution NEXAFS spectra, showing the characteristic vibrational fine structure in high-resolution measurements, and at the same time, a new peak, shifted toward higher binding energies for several eV, in all N 1s photoemission spectra.

Bozanic, A.; Majlinger, Z.; Petravic, M.; Gao, Q.; Llewellyn, D.; Crotti, C.; Yang, Y.-W. [Department of Physics, University of Rijeka, 51000 Rijeka (Croatia); Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, The Australian National University, Canberra, Australian Capital Territory 0200 (Australia); C.N.R.-Istituto Struttura della Materia, Unita Staccata di Trieste Basovizza, 34012 Trieste (Italy); National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China)

2008-07-15

270

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

SciTech Connect

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.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P. [Purdue Univ., Lafayette, IN (United States)

1993-04-01

271

Fast and slow transient charging in various III-V field-effect transistors with atomic-layer-deposited-Al2O3 gate dielectric  

NASA Astrophysics Data System (ADS)

We report measurement of fast transient charging effects (FTCE) in enhancement-mode n-channel GaAs, InP, and In0.53Ga0.47As field-effect transistors (FETs) using Al2O3 as the gate dielectric. The FTCE data reveal superior drive current and enhanced threshold voltage stability for In0.53Ga0.47As FETs. We further report charge pumping measurements for In0.53Ga0.47As transistors, revealing that the majority of interface traps are donor traps, as well as an increased trap density within the Al2O3 bulk. Such data, together with FTCE data, reveal that drain current degradation observed during pulsed I-V measurements is predominantly due to slow oxide traps, underscoring their significance within III-V/high-? metal-oxide-semiconductor FETs.

Ramón, Michael E.; Akyol, Tarik; Shahrjerdi, Davood; Young, Chadwin D.; Cheng, Julian; Register, Leonard F.; Banerjee, Sanjay K.

2013-01-01

272

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

SciTech Connect

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.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O`Bradovich, G.J.; Young, M.P. [Purdue Univ., Lafayette, IN (United States)

1993-01-01

273

Molecular-beam epitaxial growth of III-V semiconductors on Ge/Si for metal-oxide-semiconductor device fabrication  

SciTech Connect

We describe the fabrication of III-V metal-oxide-semiconductor (MOS) devices on Ge/Si virtual substrates using molecular-beam epitaxy. Migration-enhanced epitaxy and low temperature normal GaAs growth produced a sufficiently smooth surface to deposit gate oxides. A 300 nm thick GaAs buffer layer was grown, followed by a 10 nm growth of In{sub 0.2}Ga{sub 0.8}As high mobility channel layer. An 8.5 nm thick Al{sub 2}O{sub 3} layer was deposited ex situ by atomic-layer deposition. Capacitance-voltage (C-V) characteristics show the unpinning of Fermi level. This work suggests this materials combination as a promising candidate for the design of advanced, nonclassical complementary MOS and optoelectronic devices on Si substrates.

Choi, Donghun; Harris, James S. [Solid State and Photonics Laboratory, Stanford University, Stanford, California 94305 (United States); Kim, Eunji; McIntyre, Paul C. [Department of Material Science and Engineering, Stanford University, Stanford, California 94305-4045 (United States)

2008-05-19

274

Vertical "III-V" V-shaped nanomembranes epitaxially grown on a patterned Si[001] substrate and their enhanced light scattering.  

PubMed

We report on a new form of III-V compound semiconductor nanostructures growing epitaxially as vertical V-shaped nanomembranes on Si(001) and study their light-scattering properties. Precise position control of the InAs nanostructures in regular arrays is demonstrated by bottom-up synthesis using molecular beam epitaxy in nanoscale apertures on a SiO(2) mask. The InAs V-shaped nanomembranes are found to originate from the two opposite facets of a rectangular pyramidal island nucleus and extend along two opposite <111> B directions, forming flat {110} walls. Dark-field scattering experiments, in combination with light-scattering theory, show the presence of distinctive shape-dependent optical resonances significantly enhancing the local intensity of incident electromagnetic fields over tunable spectral regions. These new nanostructures could have interesting potential in nanosensors, infrared light emitters, and nonlinear optical elements. PMID:23176345

Conesa-Boj, Sònia; Russo-Averchi, Eleonora; Dalmau-Mallorqui, Anna; Trevino, Jacob; Pecora, Emanuele F; Forestiere, Carlo; Handin, Alex; Ek, Martin; Zweifel, Ludovit; Wallenberg, L Reine; Rüffer, Daniel; Heiss, Martin; Troadec, David; Dal Negro, Luca; Caroff, Philippe; Fontcuberta i Morral, Anna

2012-12-05

275

FIBER AND INTEGRATED OPTICS: Photodetector waveguide structures made of epitaxial InGaAs films and intended for integrated circuits manufactured from III-V semiconductor compounds  

NASA Astrophysics Data System (ADS)

Photodetector waveguide structures made of epitaxial InxGa1 - xAs solid-solution films were developed and investigated. These structures were intended for optical integrated circuits manufactured from III-V semiconductor compounds for operation in the wavelength range 1.0-1.5 ?m. Two types of photodetector waveguide p-i-n structures were developed. They consisted of a composite waveguide and tunnel-coupled waveguides, respectively. A study was made of structural parameters, responsivity, spectral and time characteristics, and dark currents in photodetectors made of the waveguide structures. This investigation was carried out in the wavelength range 1.0-1.3 ?m. The maximum spectral responsivity of one of the types of the waveguide photodetector was ~ 0.5 ± 0.1 A/W and the dark current did not exceed 10 - 7-10 - 8 A.

Shmal'ko, A. V.; Lamekin, V. F.; Smirnov, V. L.; Polyantsev, A. S.; Kogan, Yu I.; Babushkina, T. S.; Kuntsevich, T. S.; Peshkovskaya, O. G.

1990-08-01

276

Low-driving-current InGaAsP photonic-wire optical switches using III-V CMOS photonics platform.  

PubMed

Electrically-driven Mach-Zehnder interferometer type InGaAsP photonic-wire optical switches have been demonstrated using a III-V-on-insulator structure bonded on a thermally oxidized Si with an Al(2)O(3)/InP bonding interfacial layer which enables strong wafer bonding and low propagation loss. Lateral p-i-n junctions in the InGaAsP photonic-wire waveguides were formed by using ion implantation for changing refractive index in the InGaAsP waveguide through carrier injection. Optical switching with 10 dB extinction ratio was achieved with driving current of 200 µA which is approximately 10 times smaller than that of Si photonic-wire optical switch owing to larger free-carrier effect in InGaAsP than that in Si. PMID:23262873

Ikku, Yuki; Yokoyama, Masafumi; Ichikawa, Osamu; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

2012-12-10

277

Mid-term results after operative treatment of rockwood grade III-V Acromioclavicular joint dislocations with an AC-hook-plate  

PubMed Central

Acromioclavicular joint dislocations often occur in athletic, young patients after blunt force to the shoulder. Several static and dynamic operative procedures with or without primary ligament replacement have been described. Between February 2003 and March 2009 we treated 313 patients suffering from Rockwood III-V lesions of the AC joint with an AC-hook plate. 225 (72%) of these patients could be followed up. Mean operation time was 42 minutes in the conventional group and 47 minutes in the minimal invasive group. The postoperative pain on a scale from 1 to 10 (VAS-scale) was rated 2.7 in the conventional group and 2.2 in the minimal invasive group. Taft score showed very good and good results in 189 patients (84%). Constant score showed an average of 92.4 of 100 possible points with 89% excellent and good results and 11% satisfying results. All patients had some degree of pain or discomfort with the hookplate in place. These symptoms were relieved after removal of the plate. The overall complication rate was 10.6%. There were 6 superficial soft tissue infections, 1 fracture of the acromion, 7 redislocations after removal of the hook-plate. We observed 4 broken hooks which could be removed at the time of plate removal, 4 seromas and 2 cases of lateral clavicle bone infection, which required early removal of the plate. We can conclude that clavicle hook plate is a convenient device for the surgical treatment of Rockwood Grade III-V dislocations, giving good mid-term results with a low overall complication rate compared to the literature. Early functional therapy is possible and can avoid limitations in postoperative shoulder function.

2011-01-01

278

III-V-semiconductor-on-insulator n-channel metal-insulator-semiconductor field-effect transistors with buried Al2O3 layers and sulfur passivation: Reduction in carrier scattering at the bottom interface  

NASA Astrophysics Data System (ADS)

We have developed III-V-semiconductor-on-insulator (III-V-OI) structures on Si wafers with excellent bottom interfaces between In0.53Ga0.47As-OI channel layers and atomic-layer-deposited Al2O3 (ALD-Al2O3) buried oxides (BOXs). A surface activated bonding process and the sulfur passivation pretreatment have realized the excellent In0.53Ga0.47As-OI/ALD-Al2O3 BOX bottom interface properties. As a result, the III-V-OI n-channel metal-insulator-semiconductor field-effect transistors under the back-gate configuration showed the peak mobility of 1800 cm2/V s and the higher electron mobility than the Si universal one even in the high effective electric field range because of the reduction in the surface roughness and fixed charges.

Yokoyama, Masafumi; Yasuda, Tetsuji; Takagi, Hideki; Miyata, Noriyuki; Urabe, Yuji; Ishii, Hiroyuki; Yamada, Hisashi; Fukuhara, Noboru; Hata, Masahiko; Sugiyama, Masakazu; Nakano, Yoshiaki; Takenaka, Mitsuru; Takagi, Shinichi

2010-04-01

279

Research and development on technologies for the preparation of III-V semiconductor materials and on methods for evaluation of the quality of these materials: Gallium arsenide crystals, gradient freeze crystal growth and measurement techniques  

NASA Astrophysics Data System (ADS)

A gradient freeze technique was developed for the growth of GaAs crystals with low dislocation densities in closed quartz containers, using directional solidification. Such GaAs substrates are required for the manufacture of infrared light emitting diodes and other III-V devices. Crystal size (up to 1kg) and quality (crystal densities from 1000 to 10,000 cm E-2) are in accordance with present market requirements. The electrical parameters of III-V materials were determined by the van der Pauw method, and also by an eddy current method. Crystal perfection was evaluated by selective photoetching and chemical etching in H2SO4-H202-HF solution. Photoluminescense and photoelasticity measurements were also conducted on the III-V-materials.

Kuhn-Kuhnenfeld, F.

1981-02-01

280

LO phonon–plasmon coupling and mechanical disorder-induced effect in the Raman spectra of GaAsN alloys  

Microsoft Academic Search

Mechanical and chemical disorders are investigated in GaAsN alloys with N content close to the solubility limit, ?2–3 %. One attractive characteristic, yet unexplored, of N-based III–V ternary alloys is that they consist in mixed crystals with a sharp contrast in the bulk modulus of the two constituents. Raman scattering is well-suited for its investigation because it addresses the force

T. Tite; O. Pagès; M. Ajjoun; J. P. Laurenti; D. Bormann; E. Tournié; O. Maksimov; M. C. Tamargo

2003-01-01

281

Interplay between the magnetic and transport properties in the III-V diluted magnetic semiconductor Ga1-xMnxAs  

NASA Astrophysics Data System (ADS)

Using a low-temperature molecular-beam epitaxy growth procedure, Ga1-xMnxAs - a III-V diluted magnetic semiconductor - is obtained with Mn concentrations up to x~9%. At a critical temperature Tc (Tc~50 K for x=0.03-0.05), a paramagnetic to ferromagnetic phase transition occurs as the result of the interaction between Mn-h complexes. Hole transport in these compounds is strongly affected by the antiferromagnetic exchange interaction between holes and Mn 3d spins. A model for the transport behavior both above and below Tc is given. Above Tc, all materials exhibit transport behavior which is characteristic for systems near the metal-insulator transition. Below Tc, due to the rising spontaneous magnetization, spin-disorder scattering decreases and the relative position of the Fermi level towards the mobility edge changes. When the magnetization has reached its saturation value (below ~10 K) variable-range hopping is the main conduction mechanism. The negative magnetoresistance is the result of the expansion of the hole wave functions in an applied magnetic field.

van Esch, A.; van Bockstal, L.; de Boeck, J.; Verbanck, G.; van Steenbergen, A. S.; Wellmann, P. J.; Grietens, B.; Bogaerts, R.; Herlach, F.; Borghs, G.

1997-11-01

282

Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application  

NASA Astrophysics Data System (ADS)

Nanostructuring of ultrathin HfO2 films deposited on GaAs (001) substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching. PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea

Benedicto, Marcos; Galiana, Beatriz; Molina-Aldareguia, Jon M.; Monaghan, Scott; Hurley, Paul K.; Cherkaoui, Karim; Vazquez, Luis; Tejedor, Paloma

2011-05-01

283

Atomic chains of group-IV elements and III-V and II-VI binary compounds studied by a first-principles pseudopotential method  

NASA Astrophysics Data System (ADS)

Using the first-principles plane wave pseudopotential method we have studied structural, electronic, and transport properties of atomic chains of group-IV elements and group III-V and group II-VI binary compounds. Several materials which are insulating or semiconducting in bulk are found to be metallic in nanowire structures. Our calculations reveal that monatomic chains of Si, Ge, and Sn elements, and of binary compounds such as InP, GaAs, and AlSb, are stable and metallic. On the other hand, compound wires of BN, SiC, GaN, ZnSe, and several others have semiconducting or insulating properties. Ideal mechanical strength calculations show that some of these atomic chains can sustain strains of up to ?=0.3 . We have presented ab initio electron transport calculations for Si and AlP linear chain segments in between Al electrodes. Conductance of Si monatomic chains displays some nontrivial features as the number of atoms in the chain is varied or as the chain is strained. In addition to single atomic chain structures, junctions and grid structures of Si are investigated.

Senger, R. T.; Tongay, S.; Durgun, E.; Ciraci, S.

2005-08-01

284

Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application.  

PubMed

Nanostructuring of ultrathin HfO2 films deposited on GaAs (001) substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching.PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea. PMID:21711946

Benedicto, Marcos; Galiana, Beatriz; Molina-Aldareguia, Jon M; Monaghan, Scott; Hurley, Paul K; Cherkaoui, Karim; Vazquez, Luis; Tejedor, Paloma

2011-05-31

285

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

...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. [Paragraph...

2013-07-01

286

100 mm integration of III-V and silicon-on-insulator wafers for the realization of distributed feedback silicon evanescent lasers  

NASA Astrophysics Data System (ADS)

100 mm wafer bonding of InP-based structure and silicon-on-insulator wafers is presented with the use of a lowtemperature (300 °C) O2 plasma-assisted wafer bonding process. An efficient vertical outgassing channels (VOCs) design is developed to eliminate the fundamental obstacle of interfacial voids in bonding due to intrinsic chemical reactions. Generated gas species of H2O and H2 can quickly diffuse to VOCs, etched through-holes to buried oxide layer (BOX), and absorbed by the BOX layer owing to the open network structure and large gas permeability. The interfacial void density is reduced from 55,093 cm-2 down to 3 cm-2, more than five orders of magnitude reduction for appropriate design of VOCs. Uniform patterning of VOCs leads to no outgassing "dead zone" across the entire bonding area, and decrease of the thermal mismatch-induced interfacial strain potentially as well, which both result in the wafer scale-independent bonding. In addition, we present distributed feedback silicon lasers realized on the hybrid silicon evanescent platform. The laser operates continuous wave with a single mode output at 1600 nm. A continuous wave (CW) low threshold of 25 mA with a maximum output power of 5.4 mW is demonstrated at 10 °C. The obtained side mode suppression ratio of 50 dB, 3.6 MHz linewidth, and over 100 nm single mode operation band are comparable to those of commercial III-V DFB devices. These highly single mode lasers may find applications in computer interconnect.

Liang, Di; Fang, Alexander W.; Bowers, John E.

2008-11-01

287

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)

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.

Micovic, Miroslav

288

Tunable catalytic alloying eliminates stacking faults in compound semiconductor nanowires.  

PubMed

Planar defects in compound (III-V and II-VI) semiconductor nanowires (NWs), such as twin and stacking faults, are universally formed during the catalytic NW growth, and they detrimentally act as static disorders against coherent electron transport and light emissions. Here we report a simple synthetic route for planar-defect free II-VI NWs by tunable alloying, i.e. Cd(1-x)Zn(x)Te NWs (0 ? x ? 1). It is discovered that the eutectic alloying of Cd and Zn in Au catalysts immediately alleviates interfacial instability during the catalytic growth by the surface energy minimization and forms homogeneous zinc blende crystals as opposed to unwanted zinc blende/wurtzite mixtures. As a direct consequence of the tunable alloying, we demonstrated that intrinsic energy band gap modulation in Cd(1-x)Zn(x)Te NWs can exploit the tunable spectral and temporal responses in light detection and emission in the full visible range. PMID:22268369

Heo, Hoseok; Kang, Kibum; Lee, Donghun; Jin, Li-Hua; Back, Hyeon-Jun; Hwang, Inchan; Kim, Miseong; Lee, Hyun-Seung; Lee, Byeong-Joo; Yi, Gyu-Chul; Cho, Yong-Hoon; Jo, Moon-Ho

2012-01-26

289

Ionic electrodeposition of II-VI and III-V compounds II. Calculated current density and stoichiometry vs. deposition potential curves for parameter values representative of CdTe and with one partial current density diffusion limited  

Microsoft Academic Search

This article presents the results of a computer simulation of the kinetic model, developed in the first part of this paper for the electrodeposition of 13-15 (III-V) and 12-16 (II-VI)(notably CdTe) compounds from solutions containing reducible ions of both deposit constituents. The simulation utilized parameter values approximating those of CdTe. The calculated graphs of current density and constituent mole fractions

R. D. Engelken; T. P. Van Doren

1985-01-01

290

Research and development on technologies for the preparation of III-V semiconductor materials and on methods for evaluation of the quality of these materials: Gallium arsenide crystals, gradient freeze crystal growth and measurement techniques  

Microsoft Academic Search

A gradient freeze technique was developed for the growth of GaAs crystals with low dislocation densities in closed quartz containers, using directional solidification. Such GaAs substrates are required for the manufacture of infrared light emitting diodes and other III-V devices. Crystal size (up to 1kg) and quality (crystal densities from 1000 to 10,000 cm E-2) are in accordance with present

F. Kuhn-Kuhnenfeld

1981-01-01

291

First-principles investigation of the assumptions underlying model-Hamiltonian approaches to ferromagnetism of 3d impurities in III-V semiconductors  

NASA Astrophysics Data System (ADS)

We use first-principles calculations for transition-metal impurities V, Cr, Mn, Fe, Co, and Ni in GaAs, as well as Cr and Mn in GaN, GaP, and GaSb, to identify the basic features of the electronic structures of these systems. The microscopic details of the hole state such as the symmetry and the orbital character, as well as the nature of the coupling between the hole and the transition-metal impurity, are determined. This could help in the construction of model Hamiltonians to obtain a description of various properties beyond what current first-principles methods are capable of. We find that the introduction of a transition-metal impurity in III-V semiconductor introduces a pair of levels with t2 symmetry—one localized primarily on the transition-metal atom, referred to as crystal-field resonance (CFR), and the other localized primarily on the neighboring anions, referred to as the dangling bond hybrid (DBH). In addition, a set of nonbonding states with e symmetry, localized on the transition-metal atom, are also introduced. Each of the levels is also spin split. Considering Mn in the host crystal series GaN?GaP?GaAs?GaSb, we find that while in GaN the hole resides in the tCFR level deep in the band gap, in GaAs and GaSb it resides in the tDBH level located just above the valence-band maximum. Thus, a DBH-CFR level anticrossing exists along this host-crystal series. A similar anticrossing occurs for a fixed host crystal (e.g., GaAs) and changing the 3d impurity along the 3d series: V in GaAs represents a DBH-below-CFR limit, whereas Mn corresponds to the DBH-above-CFR case. Consequently, the identity of the hole-carrying orbital changes. The symmetry (e vs t2) and the character (DBH vs CFR), as well as the occupancy of the gap level, determine the magnetic ground state favored by the transition-metal impurity. LDA+U calculations are used to model the effect of pushing the occupied Mn states deeper into the valence band by varying U. We find that this makes the DBH state more hostlike, and at the same time diminishes ferromagnetism. While the spin-splitting of the host valence band in the presence of the impurity has been used to estimate the exchange coupling between the hole and the transition-metal impurity, we show how using this would result in a gross underestimation of the coupling.

Mahadevan, Priya; Zunger, Alex

2004-03-01

292

Dilute Magnetic Semiconductors Based on Half-Heusler Alloys  

NASA Astrophysics Data System (ADS)

We have investigated the electronic structure and magnetism of Mn-doped half-Heusler alloys by using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method within the local density approximation (LDA). Half-Heusler compounds can be attractive for spintronic applications because the crystal structure and lattice constant of these compounds are similar to those of III-V and II-VI compounds, which are often used in present semiconductor technologies. The Curie temperatures of Mn-doped half-Heusler alloys are calculated by the mean field approximation, random phase approximation, and Monte Carlo simulation. Based on our calculation results, we discuss whether or not the half-Heusler-based dilute magnetic semiconductors are useful for realizing semiconductor spintronics.

Fukushima, Tetsuya; Sato, Kazunori; Katayama-Yoshida, Hiroshi; Dederichs, Peter H.

2007-09-01

293

The Einstein relation in quantum wires of III-V, ternary, and quaternary materials in the presence of light waves: Simplified theory, relative comparison, and suggestion for experimental determination  

Microsoft Academic Search

We study the Einstein relation for the diffusivity to mobility ratio (DMR) in quantum wires (QWs) of III-V, ternary, and quaternary materials in the presence of light waves, whose unperturbed energy band structures are defined by the three band model of Kane. It has been found, taking n-InAs, n-InSb, n-Hg1-xCdxTe, n-In1-xGaxAsyP1-y lattice matched to InP as examples, that the respective

K. P. Ghatak; S. Bhattacharya; S. Bhowmik; R. Benedictus; S. Choudhury

2008-01-01

294

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)

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 K?) 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.

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

2013-04-01

295

BRAZING ALLOYS  

Microsoft Academic Search

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

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

1963-01-01

296

VANADIUM ALLOYS  

Microsoft Academic Search

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

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

1959-01-01

297

Effect of mixing enthalpy on relaxed and strained growth of III-VyIV1-yII compound alloys using molecular-beam epitaxy  

NASA Astrophysics Data System (ADS)

The strict virtual crystal model has been shown to describe accurately the mixing enthalpy of III-V ternary alloys. We allocate the different components of this model to both subreactions, i.e., the reactions forming III-VI and III-VII, present in the molecular-beam epitaxial growth of III-VIVII compound alloys, and derive thereof a model that describes accurately the composition obtained. A good correspondence with experimental growth data is obtained. We apply this model to both relaxed and strained layer growth and the evolution in the composition is given when a relaxed layer is grown on a substrate with a different lattice constant.

Genoe, J.; Németh, Š.; Grietens, B.; Behet, M.; Vounckx, R.; Borghs, G.

2000-01-01

298

The III V nitride semiconductors for blue light emission: Recent progress and a critical evaluation of their potential in comparison to the ZnSe based II VI semiconductors  

NASA Astrophysics Data System (ADS)

The GaN based III-V nitride material system holds great promise for optical device technologies in the blue and ultraviolet spectra. Past researchers were hindered by high background electron concentrations, an inability to dope GaN p-type, and lack of a suitable substrate material. In the last several years, significant progress in overcoming each of these difficulties has created widespread interest in GaN device applications. These breakthroughs are reviewed and the remaining obstacles to the fabrication of a GaN laser are identified. Based on a detailed comparison of the material properties of GaN to ZnSe, it is predicted that GaN based lasers will have significantly better performance and reliability.

Strite, S.

299

Heusler alloys  

Microsoft Academic Search

In 1903 F. Heusler reported that it was possible to make ferromagnetic alloys from non-ferromagnetic constituents copper-manganese bronze and group B elements such as aluminium and tin. Further investigations showed that the magnetic properties of these alloys are related to their chemical, L21, structure, and to the ordering of the manganese atoms on an f.c.c. sublattice.Heusler alloys are properly described

Peter J. Webster

1969-01-01

300

BRAZING ALLOYS  

DOEpatents

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)

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

1963-02-26

301

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

PubMed

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

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

2013-01-08

302

Nonswelling alloy  

DOEpatents

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.

Harkness, S.D.

1975-12-23

303

BRAZING ALLOYS  

Microsoft Academic Search

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

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

1962-01-01

304

URANIUM ALLOYS  

DOEpatents

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.

Seybolt, A.U.

1958-04-15

305

Topics in Semiconductor Physics: Part I. Phonons in Semiconducting Alloys and Alloy Superlattices. Part II. Deep Energy Levels of Defects in Mercury-Cadmium Telluride and Wurtzite Semiconductors.  

NASA Astrophysics Data System (ADS)

This thesis consists of two parts. The first part is devoted to the study of vibrational properties of semiconducting alloys and alloy superlattices. The second part deals with deep energy levels of defects in semiconductors. In Part I, densities of phonon states are evaluated using the recursion method for quasi-binary III-V semiconducting alloys: Al(,x)Ga(,1-x)As, Ga(,1-x)In(,x)As, Ga(,1-x)In(,x)Sb, GaAs(,1-x)Sb(,x), and InAs(,1-x)Sb(,x); metastable (III -V)(,1-x)IV(,2x) alloys: (GaSb)(,1-x)Ge(,2x) and (GaAs)(,1 -x)Ge(,2x); and alloy superlattices: GaAs/Al(,x)Ga(,1-x)As. New features in the densities of states, not present in those of the parent compounds, are associated with vibrations arising from various atomic arrangements in these substitutionally disordered alloys. For the alloy superlattices, the expected zone-folding effects are properly accounted for in the density-of-states spectra. Raman scattering data and infrared reflection data are interpreted based on the calculated densities of states for the above three systems. In spite of the neglect of long-range forces, the present calculations prove to be useful for a qualitative understanding of the observed mode behaviors and the disorder-activated modes. In Part II, deep energy levels of sp('3)-bonded impurities with the central-cell atomic-like defect potential are obtained using the Green's function technique. The host materials considered here are Hg(,1-x)Cd(,x)Te alloys which have a narrow and variable band gap, and wurtzite semiconductors: AlN, CdS, CdSe, ZnS, and ZnO, which have large band gaps. A variety of defects responsible for trapping centers are identified. Our results would be instrumental in improving the quality of these technologically important materials.

Kobayashi, Akiko

306

BRAZING ALLOYS  

DOEpatents

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)

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

1962-02-20

307

COATED ALLOYS  

DOEpatents

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.

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

1958-07-15

308

Thin semiconductor alloy films: Fabrication and physical properties  

NASA Astrophysics Data System (ADS)

The main emphasis of this thesis is on fabrication and physical properties of thin semiconductor alloy films. We investigated the detailed processes which play a role in fabricating these materials, and systematically investigated the links between the fabrication processes and physical properties of the alloys of interest. Wide-gap semiconductor ternary alloys based on combining group-II and group-VI elements were grown by molecular beam epitaxy (MBE) over a wide range of compositions. The indices of refraction of these II-VI ternary alloys were measured at wavelengths below their respective energy gaps. A set of empirical parameters were establish for each alloy family, which can then be used to calculate the index of refraction for an arbitrary alloy composition at arbitrary wavelength. We applied the single effective oscillator (SEO) model to the experimental data in order to examine the effect of the covalency (or ionicity) of these semiconductor alloys, and to establish a method for extrapolating physical properties for different zinc-blende II-VI compounds. Furthermore, to fit the data near the energy gap, an additional term was added to the SEO model, which accounts for the effect of the direct energy gap. In addition to our investigation of II-VI-based alloys, we also fabricated ferromagnetic semiconductor III-Mn-V alloys using a low temperature MBE technique. A thorough investigation of the physical properties (such as growth, magnetic, and transport properties) of III-Mn-V alloys was carried out. Specifically, we have studied two issues involving these materials: low temperature annealing of GaMnAs under different strain conditions; and fabrication of hybrid magnetic structures comprised of GaMnAs and ZnMnSe, the latter system involving antiferromagnetic interactions between the Mn ions. Furthermore, we fabricated semiconductor superlattices of ZnSe1-x Tex and GaAs1-xSbx in which the chemical composition x varies sinusoidally along the direction of growth, and we studied the physical properties of these novel structures. The sinusoidal nature of the compositional profiles of these materials was inferred from the presence of only a single superlattice Fourier component in the x-ray diffraction spectra. Superlattice formation is additionally supported by systematic photoluminescence data. In the end, we have fabricated and studied various digital alloys of III-V/Mn, where Mn-containing monolayers are "inserted" periodically in the III-V host material. Most of these digital structures exhibited ferromagnetism at low temperature, as demonstrated by hysteresis loops in the magnetization, and a metallic p-type conductivity with a strong anomalous Hall effect. The GaSb/Mn digital system exhibited high temperature ferromagnetic behavior, as demonstrated by a strong anomalous Hall effect characterized by hysteresis loops up to 400 K.

Liu, Xinyu

309

Empty cage to three-dimensional structural transition in nanoparticles of III-V compound semiconductors: The finding of magic (AlP)13 and (GaP)32  

NASA Astrophysics Data System (ADS)

Small nanoparticles of III-V compound semiconductors have often been considered to have open-cage structures. However, using first-principles calculations, we report the finding of a structural transition from empty-cage structures for (AlN)n and (GaN)n nanoparticles up to n = 34 that we studied, to a filled-cage structure for (InN)32. Further, phosphides and arsenides of Al and In have an early transition to three-dimensional (3D) filled-cage structures. Our results show that a 3D (AlP)13 is strongly magic with high binding energy and large highest occupied-lowest unoccupied molecular orbital gap. But nanoparticles of GaP show a transition from an empty cage for n = 13 to a strongly magic 3D filled cage for n = 32. The latter has a cage of (GaP)28 and a (GaP)4 squashed cube inside, the atoms on which are well connected with the cage. The bonding characteristics and the reason for structural transition are discussed.

Kaur, Prabhsharan; Sekhon, S. S.; Kumar, Vijay

2012-02-01

310

'Candidatus Phytoplasma sudamericanum', a novel taxon, and strain PassWB-Br4, a new subgroup 16SrIII-V phytoplasma, from diseased passion fruit (Passiflora edulis f. flavicarpa Deg.).  

PubMed

Symptoms of abnormal proliferation of shoots resulting in formation of witches'-broom growths were observed on diseased plants of passion fruit (Passiflora edulis f. flavicarpa Deg.) in Brazil. RFLP analysis of 16S rRNA gene sequences amplified in PCRs containing template DNAs extracted from diseased plants collected in Bonito (Pernambuco) and Viçosa (Minas Gerais) Brazil, indicated that such symptoms were associated with infections by two mutually distinct phytoplasmas. One phytoplasma, PassWB-Br4 from Bonito, represents a new subgroup, 16SrIII-V, in the X-disease phytoplasma group ('Candidatus Phytoplasma pruni'-related strains). The second phytoplasma, PassWB-Br3 from Viçosa, represents a previously undescribed subgroup in group 16SrVI. Phylogenetic analyses of 16S rRNA gene sequences were consistent with the hypothesis that strain PassWB-Br3 is distinct from previously described 'Ca. Phytoplasma' species. Nucleotide sequence alignments revealed that strain PassWB-Br3 shared less than 97.5 % 16S rRNA gene sequence similarity with previously described 'Ca. Phytoplasma' species. The unique properties of its DNA, in addition to natural host and geographical occurrence, support the recognition of strain PassWB-Br3 as a representative of a novel taxon, 'Candidatus Phytoplasma sudamericanum'. PMID:21669919

Davis, Robert E; Zhao, Yan; Dally, Ellen L; Jomantiene, Rasa; Lee, Ing-Ming; Wei, Wei; Kitajima, Elliot W

2011-06-13

311

Epitaxial growth in dislocation-free strained asymmetric alloy films  

SciTech Connect

Epitaxial growth in strained asymmetric, dislocation-free, coherent, alloy films is explored. Linear-stability analysis is used to theoretically analyze the coupled instability arising jointly from the substrate-film lattice mismatch (morphological instability) and the spinodal decomposition mechanism. Both the static and growing films are considered. Role of various parameters in determining stability regions for a coherent growing alloy film is investigated. In addition to the usual parameters: lattice mismatch {epsilon}, solute-expansion coefficient {eta}, growth velocity V, and growth temperature T, we consider the alloy asymmetry arising from its mean composition. The dependence of elastic moduli on composition fluctuations and the coupling between top surface and underlying bulk of the film also play important roles. The theory is applied to group III-V films such as GaAsN, InGaN, and InGaP and to group IV Si-Ge films at temperatures below the bare critical temperature T{sub c} for strain-free spinodal decomposition. The dependences of various material parameters on mean concentration and temperature lead to significant qualitative changes.

Desai, Rashmi C.; Kim, Ho Kwon; Chatterji, Apratim; Ngai, Darryl; Chen Si; Yang Nan [Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 (Canada)

2010-06-15

312

Orthodontic silver brazing alloys.  

PubMed

Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy. PMID:2576971

Brockhurst, P J; Pham, H L

1989-10-01

313

Amorphous metal alloys produced by mechanical alloying  

Microsoft Academic Search

Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization

T. J. Tiainen; R. B. Schwarz

1989-01-01

314

High Performance Titanium Alloys.  

National Technical Information Service (NTIS)

Original titanium alloys appropriate for various uses have been developed. A cost effective corrosion resistant Ti alloy was developed utilizing small effective addition of 0.05% Pd. High strength and high toughness alpha + Beta alloys were developed by t...

M. Okada W. Takahashi T. Maeda Y. Shida T. Fukuda

1990-01-01

315

Electric dipole (hyper)polarizabilities of selected X2Y2 and X3Y3 (X = Al, Ga, In and Y = P, As): III-V semiconductor clusters. An ab initio comparative study.  

PubMed

A systematic ab initio comparative study of the (hyper)polarizabilities of selected III-V stoichiometric semiconductor clusters has been carried out. Our investigation focuses on the ground state structures of the dimers and on two dissimilar trimer configurations of aluminum, gallium, indium phosphide and arsenide. The basis set effect on both the polarizabilities and hyperpolarizabilities of the studied systems has been explicitly taken into account relying on the augmented correlation consistent aug-cc-pVnZ (n = D, T, Q, and 5) basis sets series. In addition, a rough estimation of the effects of the relativistic effects on the investigated properties is provided by extension of the study to include calculations performed with relativistic electron core potentials (or pseudopotentials). Electron correlation effects have been estimated utilizing methods of increasing predictive reliability, e.g., the Møller-Plesset many body perturbation theory and the couple cluster approach. Our results reveal that in the considered semiconductor species the Group III elements (Al, Ga, In) play a vital role on the values of their relative (hyper)polarizability. At all levels of theory employed the most hyperpolarizable clusters are the indium derivatives while the aluminum arsenide clusters also exhibit high, comparable hyperpolarizabilities. The less hyperpolarizable species are those composed of gallium and this is associated with the strong influence of the nuclear charge on the valence electrons of Ga due to the poor shielding that is provided by the semicore d electrons. In addition, the analysis of the electronic structure and the hyperpolarizability magnitudes reveals that clusters, in which their bonding is characterized by strong electron transfer from the electropositive to the electronegative atoms, are less hyperpolarizable than species in which the corresponding electron transfer is weaker. Lastly, from the methodological point of view our results point out that the hyperpolarizabilities of those species converge when an augmented triple-zeta quality basis set is used and, also, that the second order Møller-Plesset approximation (MP2) overestimates considerably their second hyperpolarizabilities with respect to the highest level of coupled cluster theory applied in this study (CCSD(T)). PMID:19093824

Karamanis, Panaghiotis; Pouchan, Claude; Leszczynski, Jerzy

2008-12-25

316

Boron alloy  

SciTech Connect

This paper describes a ferro-boron alloy produced in situ in a basic oxygen furnace, an induction furnace, or an electric furnace, or in combination with a mixing vessel. It comprises: 1.4% to 15% by weight boron; less than 0.002% by weight nitrogen; less than about 0.2% by weight carbon; less than about 0.01% by weight aluminum; and the balance iron with minute amounts of residuals.

Sussman, R.C.; Evans, L.G.

1990-06-26

317

Synthesis of highly mismatched alloys using ion implantation and pulsed laser melting  

NASA Astrophysics Data System (ADS)

Highly mismatched alloys (HMAs) are dilute alloys whose fundamental properties are dramatically modified through the substitution of a relatively small fraction (up to ˜5%) of host atoms with a very different element. Specific examples are dilute III V nitrides (e.g. GaNxAs1-x) and II VI oxides (e.g. ZnOxTe1-x) in which the conduction bands are strongly modified by the anticrossing interaction between localized states of O or N and the extended states of the semiconductor matrix. Using a highly non-equilibrium method: the combination of ion implantation and pulsed laser melting (II-PLM) we have synthesized a wide variety of III-Nx-V1-x and II-Ox-VI1-x alloys with N or O content up to 2%. The structural and optical properties of these HMAs have been systematically investigated. In particular, we demonstrated that the Zn1-yMnyOxTe1-y dilute oxide is a multiband alloy that can be used for the realization of the single junction, high efficiency intermediate band solar cells.

Yu, K. M.; Scarpulla, M. A.; Farshchi, R.; Dubon, O. D.; Walukiewicz, W.

2007-08-01

318

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

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.

Spahn, O.B.; Lear, K.L.

1998-03-10

319

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

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.

Spahn, Olga B. (Albuquerque, NM); Lear, Kevin L. (Albuquerque, NM)

1998-01-01

320

Rhenium Alloying of Tungsten Heavy Alloys.  

National Technical Information Service (NTIS)

Alloying experiments have been performed using rhenium additions to a classic 90 mass % tungsten heavy alloy. The mixed powder system was liquid phase sintered to full density at 1500 C in 60 min The rhenium modified alloys exhibited a smaller grain size,...

R. M. German A. Bose G. Jerman

1989-01-01

321

Films of Soft-Magnetic Fe-Based Nanocrystalline Alloys for High-Density Magnetic Storage Application  

NASA Astrophysics Data System (ADS)

This paper presents a review of works related to the problem of development of soft-magnetic film Fe-based alloys exhibiting the combination of properties, such as the high saturation inductance, high level of soft-magnetic parameters over a wide range of MHz-frequencies, high wear-resistance and thermal stability, and an ability to be prepared by thin-film technologies. Magnetic cores of high-density recording heads are the principal application of these materials. Physical fundamentals of explanation of ferromagnetic behavior of a material with nano-sized structure, which have been developed for FINEMETs (Fe-Nb-Cu-Si-B) with the mixed amorphous + nanocrystalline structure, are considered. A new class of alloys Fe-Me-X (Me=Metal of III-V groups of the Periodic Table and X=C, N, O, and B) whose properties are higher that those of FINEMETs are discussed. The structure of these alloys consists of two nanocrystalline phases, such as the ferromagnetic ?-Fe-based and nonmagnetic MeX phases. This structure provides the dispersion strengthening of the alloys. Metal science approaches to the selection of both chemical compositions and conditions of structure formation for these film alloys have been developed by authors and are discussed in this article.

Shefte?, E. N.; Bannykh, O. A.

322

Alloys for prosthodontic restorations  

Microsoft Academic Search

The numbers and types of alloys for prosthodontic restorations have increased dramatically over the past 25 years, making selection of an alloy for a given clinical situation difficult. Factors such as cost, the need for better strength, and worries about alloy corrosion have pressured the alloy market to change significantly. A number of properties—including yield strength, hardness, elastic modulus, microstructural

John C. Wataha

2002-01-01

323

Epitaxial Si1-xGex alloys studied by spin-polarized photoemission  

NASA Astrophysics Data System (ADS)

Spin-polarized photoemission is used to study Si1-xGex alloys epitaxially grown on a Si substrate. Spin-oriented electrons are generated in the conduction band upon excitation with circularly polarized light. We prove that in these structures it is possible to lower the vacuum level of the system below the conduction band minimum at the ? point of the Brillouin zone and show that electron spin polarization values P=40±3% can be achieved when promoting electrons with direct transitions at ?. Such values can be greatly increased, up to P=72±3%, in compressively strained thin epitaxial films, thus obtaining performances very close to those of III-V semiconductor heterostructures.

Ferrari, A.; Bottegoni, F.; Isella, G.; Cecchi, S.; Ciccacci, F.

2013-09-01

324

Pressure-induced variation of effective dynamic charge in InP1-xAsx alloys due to charge transfer within cation sublattice  

NASA Astrophysics Data System (ADS)

From the measurements of Raman spectra of ternary InP1-xAsx (x=0.4, 0.6, and 0.8) under high pressure, the pressure-dependence of the ionicity was found to be strongly affected by the As mole fraction x. In particular, for x=0.6 and 0.8 ternary alloys, the effective dynamic charge of InP-like mode strictly increases with pressure, in sharp contrast to the corresponding behavior satisfied by the majority of III-V and II-VI binary compounds including InP. This can be understood by the charge transfer from As to P in the cation sublattice when the ternary alloys are under pressure.

Park, Ta-Ryeong; Byun, Jun Seok; Kim, Tae Jung; Kim, Young Dong

2012-12-01

325

Weldability of intermetallic alloys  

SciTech Connect

Ordered intermetallic alloys are a unique class of material that have potential for structural applications at elevated temperatures. The paper describes the welding and weldability of these alloys. The alloys studied were nickel aluminide (Ni[sub 3]Al), titanium aluminide (Ti[sub 3]Al), and iron aluminide.

David, S.A. (Oak Ridge National Lab., TN (United States))

1990-01-01

326

PLUTONIUM-ZIRCONIUM ALLOYS  

Microsoft Academic Search

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

F. W. Schonfeld; J. T. Waber

1960-01-01

327

NICKEL-BASE ALLOY  

Microsoft Academic Search

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

H. Inouye; W. D. Manly; T. K. Roche

1960-01-01

328

SUPERCONDUCTING VANADIUM BASE ALLOY  

DOEpatents

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.

Cleary, H.J.

1958-10-21

329

Creep Resistant Zinc Alloy  

SciTech Connect

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.

Frank E. Goodwin

2002-12-31

330

Weldability of High Alloys  

SciTech Connect

The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

Maroef, I

2003-01-22

331

Alloying of aluminum-beryllium alloys  

NASA Astrophysics Data System (ADS)

The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

Molchanova, L. V.; Ilyushin, V. N.

2013-01-01

332

Investment Casting of Columbium Alloys.  

National Technical Information Service (NTIS)

The state of the art of columbium alloy investment castings has been advanced. In addition to demonstration of castability of four different alloys, the cast material itself has been characterized with respect to microstructure, alloy segregation, weldabi...

J. R. Humphrey A. I. Niravath

1975-01-01

333

Electrical discharge surface alloying  

Microsoft Academic Search

This paper details the electrical discharge surface alloying\\/modification of ?-TiAl (Ti–46.5Al–4(Cr, Nb, Ta, B)) and ?\\/? Ti alloy (Ti–6Al–4V) sheet (1mm thick) during wire cutting using deionised water dielectric with nickel and copper wires. In addition, topography, microstructure and wear test data are given for a 2% Cr steel mill roll material textured\\/alloyed using partially sintered powder metallurgy (PM) hardmetal

H. G Lee; J Simao; D. K Aspinwall; R. C Dewes; W Voice

2004-01-01

334

Amorphous metal alloy  

DOEpatents

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.

Wang, R.; Merz, M.D.

1980-04-09

335

Low activation ferritic alloys  

DOEpatents

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.

Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

1985-02-07

336

NICKEL-BASE ALLOY  

DOEpatents

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.

Inouye, H.; Manly, W.D.; Roche, T.K.

1960-01-19

337

Amorphous alloys and superconductivity  

SciTech Connect

Theoretical aspects and experimental results concerning transition temperatures, coupling constants, critical field, critical current density and pressure dependence of T /sub c/ of amorphous alloys are discussed.

Luscher, E.; Fritsch, G.

1984-09-01

338

Ductile transplutonium metal alloys  

DOEpatents

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.

Conner, W.V.

1981-10-09

339

Cesium iodide alloys  

DOEpatents

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.

Kim, H.E.; Moorhead, A.J.

1992-12-15

340

Spectra of Ternary Alloys  

Microsoft Academic Search

The vibrational frequency-dsitribution spectra of the random one-dimensional ternary alloy AcB1-cC are accurately predicted for the first time by a statistical theory of small clusters embedded in a coherent-potential-approximation effective medium. The theory can be applied practically to real three-dimensional alloys.

Charles W. Myles; John D. Dow

1979-01-01

341

Neutron Absorbing Alloys  

DOEpatents

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.

Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

2004-05-04

342

Fracture toughness investigations of tungsten alloys and SPD tungsten alloys  

Microsoft Academic Search

Three different tungsten alloys (pure W, a lanthanum-oxide dispersion strengthened W-alloy – WL10 and a potassium doped tungsten alloy – WVM) in different fabrication conditions (sintered and rolled rods) were tested to characterize their fracture behaviour at different temperatures (from ?196 to 800°C). Additionally severe plastic deformed tungsten alloys were produced. It is shown that an ultra fine grained microstructure

M. Faleschini; H. Kreuzer; D. Kiener; R. Pippan

2007-01-01

343

Investigation on mechanical alloying process for vanadium alloys  

NASA Astrophysics Data System (ADS)

Mechanical alloying (MA) is an efficient approach for fabricating particle-dispersion alloys, and has recently been introduced to strengthen structural materials including vanadium alloys for fusion application. Dissolution behavior of the alloying elements is a key issue for optimizing MA in fabricating particle-dispersion vanadium alloys. This paper studies the MA process for V-4Cr-4Ti alloys with Y addition. The result shows that, in V matrix, the dissolution rate of Y is higher than that of Cr, and the dissolution rate of Cr is higher than that of Ti. In addition, dissolution of milling ball material and dispersion particles can harden the MA-fabricated alloy.

Zheng, P. F.; Nagasaka, T.; Muroga, T.; Chen, J. M.

2013-11-01

344

The transient oxidation of alloys  

Microsoft Academic Search

The pre-steady-state oxidation of a wide range of binary alloys of practical importance, in 1 atm oxygen at 600° C, is discussed in terms of the main determining parameters, namely the free energies of formation and growth rates of the component and complex oxides, the bulk alloy composition, the alloy interdiffusion coefficient, the oxygen solubility and diffusivity in the alloy,

B. Chattopadhyay; G. C. Wood

1970-01-01

345

(Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units  

SciTech Connect

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.

Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

2012-01-09

346

(Si)5-2y(AlP)y alloys assembled on Si(100) from Al-P-Si3 building units  

NASA Astrophysics Data System (ADS)

An original class of IV/III-V hybrid (Si)5-2y(AlP)y/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH3)3 and atomic Al yielding tetrahedral ``Al-P-Si3'' 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.

Watkins, T.; Jiang, L.; Xu, C.; Chizmeshya, A. V. G.; Smith, D. J.; Menéndez, J.; Kouvetakis, J.

2012-01-01

347

Two phase titanium aluminide alloy  

Microsoft Academic Search

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

Seetharama C. Deevi; C. T. Liu

2001-01-01

348

THORIUM-SILICON-BERYLLIUM ALLOYS  

DOEpatents

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.

Foote, F.G.

1959-02-10

349

Electrospark alloying of the titanium alloy VT6 with tungsten-free hard alloys  

Microsoft Academic Search

The mass transfer kinetics and alloying elements distribution in a coating layer on the titanium alloy VT6 were investigated, as well as the properties of the layer after electrospark alloying with tungsten free electrodes based on the refractory compounds of titanium and zirconium nitride. !t was shown that the microhardness of the alloyed layer is 3-S times, and of the

I. A. Podchernyaeva; V. A. Lavrenko; V. I. Berezanskaya; V. P. Smirnov

1996-01-01

350

Analysis of niobium alloys.  

PubMed

An ion-exchange method was applied to the analysis of synthetic mixtures representing various niobium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titanium, molybdenum, tungsten and tantalum. Mixtures containing zirconium or hafnium, tungsten, tantalum and niobium were separated by means of a single short column. Coupled columns were employed for the resolution of mixtures containing vanadium, zirconium or titanium, molybdenum, tungsten and niobium. The separation procedures and the methods employed for the determination of the alloying elements in their separate fractions are described. PMID:18960385

Ferraro, T A

1968-09-01

351

Reactive brazing of Al alloy to Mg alloy using zinc-based brazing alloy  

Microsoft Academic Search

According to the feature of Mg–Zn eutectic reaction, Al alloy was bonded to Mg alloy by contact reaction brazing using a zinc-based brazing alloy successfully. The experimental observations showed that Mg–Al intermetallic compounds were avoided for the addition of the zinc-based brazing alloy. The Mg substrate and the remanent brazing alloy were bonded with the reaction zone that formed along

Liming Liu; Jinhong Tan; Xujing Liu

2007-01-01

352

Alloys by precision electrodeposition  

NASA Astrophysics Data System (ADS)

We show that a Cu-Ni alloy film of arbitrary composition may be grown by electrodepositing well-defined submonolayer quantities of Cu and Ni in alternation. Active computer control of the deposition process is used to compensate for undesired electrochemical processes, such as partial redissolution of the Ni. Magnetic measurements were used to characterize alloy homogeneity. With this electrodeposition method it is possible to tailor the composition profile of a film with subnanometer precision. As an example, Cu0.19Ni0.81/Cu0.79Ni0.21 alloy/alloy multilayers were fabricated which gave prominent satellite peaks in high angle x-ray diffraction patterns.

Kazeminezhad, I.; Blythe, H. J.; Schwarzacher, W.

2001-02-01

353

Tungsten Alloy Technology.  

National Technical Information Service (NTIS)

The papers collected here represent contributions to the International Conference on Tungsten and its Alloys in which Materials Directorate personnel had primary or secondary authorship responsibility. The conference was held in Arlington, VA, 16-18 Novem...

R. J. Dowding

1993-01-01

354

Superconducting gold alloys  

Microsoft Academic Search

Although the discovery of a gold alloy with a superconducting state at relatively high temperature would be significant and\\u000a exciting, it has been a feature of the past decade that technology has advanced to the stage of producing applications for\\u000a gold and other alloys which achieve superconductivity at low critical temperatures. A significant research effort has gone\\u000a into the search

H. R. Khan

1984-01-01

355

Cobalt base alloy  

SciTech Connect

A cobalt base alloy having a superior high-temperature strength and high-temperature ductility, containing, by weight, 0.15 to 2% carbon, less than 2% silicon, less than 2% manganese, 5 to 15% nickel, 18 to 35% chromium, 3 to 15% tungsten, 0.003 to 0.1% boron, 0.01 to 1% niobium, 0.01 to 1% zirconium, less than 10% iron, less than 1% tantalum, less than 1% hafnium and remainder cobalt. At least one of 0.01 to 1 wt% titanium and 0.01 to 1 wt% (combined amount) rare earth elements is added to the alloy. The alloy is used as a casting and contains eutectic carbides and secondary carbides precipitated substantially uniformly in the grains. If the secondary carbides are formed by an age-treatment conducted at a higher temperature than that at which the alloy is actually used, the high-temperature strength and the high-temperature ductility of the alloy are remarkably improved. The cobalt base alloy is formed into gas turbine nozzles by a precision casting.

Fukui, Y.; Kashimura, T.

1984-03-20

356

High Cycle Fatigue of Nickel Base Alloys.  

National Technical Information Service (NTIS)

High cycle fatigue data for the alloys Nimonic alloy 901, Inconel alloy 718, Nimonic alloy 90, Nimonic alloy 115 and Nimocast alloy 738LC were determined at elevated temperatures. The effect of long term thermal exposure on the high cycle fatigue properti...

G. M. McColvin

1977-01-01

357

Review of Recent Developments. Nickel- and Cobalt-Base Alloys.  

National Technical Information Service (NTIS)

Contents: Alloy development and evaluation; (Cast nickel-base alloys; Turbine-blade alloy for thin sections, Evaluation of alloys for use in hot working); (Dispersion-strengthened alloys, Dispersion-strengthened cobalt alloys for turbine vanes); Oxidation...

V. F. Beuhring W. F. Simmons

1970-01-01

358

III-V semiconductor quantum well and superlattice detectors  

Microsoft Academic Search

The paper reviews the development of IR detectors for the 8 - 12 micrometer wavelength range based on GaAs\\/AlGaAs quantum well structures and InAs\\/(GaIn)Sb short-period superlattices (SPSLs) at the Fraunhofer-Institute IAF. Photoconductive GaAs\\/AlGaAs quantum well infrared photodetectors (QWIPs) are used for the fabrication of starring IR cameras for thermal imaging in the third atmospheric window. The long wavelength infrared (LWIR)

Martin Walther; Frank Fuchs; Harald Schneider; Joachim Fleissner; J. Schmitz; W. Pletschen; Juergen Braunstein; Johann Ziegler; Wolfgang A. Cabanski; Peter Koidl; Guenter Weimann

1998-01-01

359

Application Of III–V Compounds In Solar Cells  

Microsoft Academic Search

\\u000a An obvious disadvantage of sunlight as a power source is its low energy density. To generate appreciable electrical power\\u000a in space and on the earth, it is necessary to collect sunlight from large areas, having covered them with expensive semiconductor\\u000a solar cells. The cost of electricity obtained in such a way exceeds substantially that generated by conventional methods,\\u000a and this

V. M. Andreev

360

Specific features of Raman spectra of III-V nanowhiskers  

NASA Astrophysics Data System (ADS)

Raman spectra of GaAs nanowhiskers that are grown on different substrates and differ from one another by the content of the sphalerite and wurtzite phases have been investigated. Special attention has been focused on the manifestation of structural features in the scattering spectra of nanowhiskers. It has been established that the nanowhiskers are characterized both by random inclusions of wurtzite layers in the sphalerite structure and by the continuous growth in the wurtzite phase. The interpretation of the scattering spectrum agrees with the concept of summation of the dispersion curves of the sphalerite structure upon transition to the wurtzite structure, which leads to a transformation of zone-boundary modes at the L point of the Brillouin zone into zone-center modes of the wurtzite structure and, as a consequence, to the appearance of a number of new fundamental modes of different symmetries. An analysis of the Raman spectra has revealed the formation of the hexagonal 4 H polytype in narrow layers of nanowhiskers due to a random packing of hexagonal layers. The coexistence of the sphalerite and wurtzite phases in GaAs nanowhiskers completely correlates with the photoluminescence spectra measured for the same samples.

Karpov, S. V.; Novikov, B. V.; Smirnov, M. B.; Davydov, V. Yu.; Smirnov, A. N.; Shtrom, I. V.; Cirlin, G. E.; Bouravleuv, A. D.; Samsonenko, Yu. B.

2011-07-01

361

Novel compound semiconductor devices based on III-V nitrides  

SciTech Connect

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.

Pearton, S.J.; Abernathy, C.R. [Florida Univ., Gainesville, FL (United States); Ren, F. [AT & T Bell Laboratories, Murray Hill, NJ (United States)] [and others

1995-10-01

362

High temperature surface degradation of III-V nitrides  

SciTech Connect

The surface stoichiometry, surface morphology and electrical conductivity of AlN, GaN, InN, InGaN and InAlN was examined at rapid thermal annealing temperatures up to 1,150 C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1,000 C. Auger Electronic Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1,150 C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1,000 C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAlN was found to increase by {approximately} 10{sup 2} from the as grown value after annealing at 800 C and then remain constant up to 1,000 C, while that of InGaN increased rapidly above 700 C. The RMS roughness increased above 800 C and 700 C respectively for InAlN and InGaN samples. In droplets began to form on the surface at 900 C for InAlN and at 800 C for InGaN, and then evaporate at 1,000 C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 {angstrom} of the sample for annealing {ge} 800 C in both materials.

Vartuli, C.B.; Pearton, S.J.; Abernathy, C.R.; MacKenzie, J.D.; Lambers, E.S. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States)

1996-05-01

363

Ion implantation and annealing studies in III-V nitrides  

SciTech Connect

Ion implantation doping and isolation is expected to play an enabling role for the realization of advanced III-Nitride based devices. In fact, implantation has already been used to demonstrate n- and p-type doping of GaN with Si and Mg or Ca, respectively, as well as to fabricate the first GaN junction field effect transistor. Although these initial implantation studies demonstrated the feasibility of this technique for the III-Nitride materials, further work is needed to realize its full potential. After reviewing some of the initial studies in this field, the authors present new results for improved annealing sequences and defect studies in GaN. First, sputtered AlN is shown by electrical characterization of Schottky and Ohmic contacts to be an effect encapsulant of GaN during the 1,100 C implant activation anneal. The AlN suppresses N-loss from the GaN surface and the formation of a degenerate n{sup +}-surface region that would prohibit Schottky barrier formation after the implant activation anneal. Second, they examine the nature of the defect generation and annealing sequence following implantation using both Rutherford Backscattering (RBS) and Hall characterization. They show that for a Si-dose of 1 x 10{sup 16} cm{sup {minus}2} 50% electrical donor activation is achieved despite a significant amount of residual implantation-induced damage in the material.

Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Williams, J.S.; Tan, H.H. [Australian National Univ., Canberra (Australia). Dept. of Electronic Materials Engineering; Karlicek, R.J. Jr.; Stall, R.A. [Emcore Corp., Somerset, NJ (United States)

1996-12-31

364

Wetting of III-V melts on crucible materials  

NASA Astrophysics Data System (ADS)

The measurement of the wetting angle of GaSb and InSb melts on C, BN, AIN, Al2O3 and SiO2 substrates by the sessile drop method under static vacuum is described and discussed. The surface tension and the work of adhesion are calculated. Finally, the results are compared with published data and with the predictions of theoretical models.

Harter, I.; Dusserre, P.; Duffar, T.; Nabot, J.-Ph.; Eustathopoulos, N.

1993-07-01

365

Passivation of III-V semiconductor surfaces and related devices  

Microsoft Academic Search

In this research, novel process techniques for passivation of GaAs and InP surfaces have been developed. These techniques involve surface treatments using sulfide solutions, ECR Hsb2 and Hsb2\\/Hsb2S-plasmas. The effectiveness of these treatments in passivating devices based on metal-semiconductor and insulator-semiconductor interfaces have been demonstrated. A variety of other surface-sensitive devices, such as AlGaAs\\/GaAs HBTs, InGaAs\\/GaAs based vertical-cavity-surface-emitting lasers (VCSELs),

Anil Kapila

1997-01-01

366

Passivation of III-V semiconductor surfaces and related devices  

NASA Astrophysics Data System (ADS)

In this research, novel process techniques for passivation of GaAs and InP surfaces have been developed. These techniques involve surface treatments using sulfide solutions, ECR Hsb2 and Hsb2/Hsb2S-plasmas. The effectiveness of these treatments in passivating devices based on metal-semiconductor and insulator-semiconductor interfaces have been demonstrated. A variety of other surface-sensitive devices, such as AlGaAs/GaAs HBTs, InGaAs/GaAs based vertical-cavity-surface-emitting lasers (VCSELs), and GaAs based MESFETs have also been successfully passivated. GaAs samples treated with sulfide solutions of (NHsb4)sb2S,\\ Psb2Ssb5 and/or SeSsb2, exhibit more than 4-fold increase in the photoluminescence intensity as compared to the untreated samples. Using similar solutions, excellent passivation of SiNsbx/GaAs (InP) interfaces have been achieved. SiNsbx overlayers were deposited using a custom designed and built ECR-PECVD system. The best passivated Al/SiNsbx/GaAs capacitors exhibit a minimum defect density of low 10sp{12} cmsp{-2}eVsp{-1} and a band bending of ˜0.8 eV. The dry treatments of the surfaces using Hsb2S- and/or H-plasmas, prior to SiNsbx deposition, also result in improved quasi-static and high frequency capacitance-voltage characteristics. The band bending in Al/SiNsbx/InP samples passivated with gaseous Hsb2S, and Hsb2-plasmas is estimated to be ˜0.49 and 0.95 eV, respectively. The defect densities estimated for the best Hsb2-plasma treated device is 1.3× 10sp{12} cmsp{-2}eVsp{-1}. A novel, in-situ, technique of monitoring electrical properties of devices during gaseous and plasma processing has also been developed and successfully demonstrated. The metal-semiconductor-metal devices treated with 50 W Hsb2-plasma and encapsulated with SiNsbx exhibit reduction in the dark current by a factor of ˜40. Prolonged exposure to 100 and 200 W Hsb2-plasmas, however, result in higher dark current due to plasma-induced defect formation on the surface. The AlGaAs/GaAs HBTs, passivated using sulfide solutions, exhibit an improvement in beta (dc) by a factor of 10. The threshold current of 8-micrometer pillar structure VCSELs is reduced from ˜0.98 mA to 0.67 mA. The SRV of minority carriers is estimated to reduce by 25%, to a value of 1.5× 10sp5 from 2×10sp5 cm/s. The gate current in passivated MESFETs is reduced by a factor greater than 2.5 as a result of Hsb2/Hsb2S-plasma treatment. The passivated devices are typically found to be stable over several months of testing.

Kapila, Anil

367

(Defect studies in III-V thin film semiconductors)  

SciTech Connect

Our primary research objective in 90/91 has been to continue studying misfit dislocation confinement by patterning substrates into mesas before the epitaxial growth of strained layers. This report presents progress for many of the areas of our research. (JL)

Not Available

1991-01-01

368

III-V access waveguides using atomic layer deposition  

NASA Astrophysics Data System (ADS)

Normally, the larger refractive index contrast of silicon-on-insulator (SOI) photonics used for transporting highly confined optical modes is not available in compound semiconductor systems because the optically active layer rests upon an epitaxial support layer having a similar refractive index. Here, a semiconductor-under-insulator (SUI) technology for compound semiconductor membrane photonic circuitry is presented. It will be shown that such a technology can facilitate the transport of highly confined optical modes in compound semiconductor systems and is anticipated to be a critical part of future scalable quantum photonics applications.

Mnaymneh, Khaled; Frédérick, Simon; Dalacu, Dan; Lapointe, Jean; Poole, Philip J.; Williams, Robin L.

2013-03-01

369

Surface Localization of Buried III-V Semiconductor Nanostructures.  

PubMed

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

Alonso-González, P; González, L; Fuster, D; Martín-Sánchez, J; González, Yolanda

2009-05-09

370

Alloying and heat treatment of heat-resistant alloys  

Microsoft Academic Search

A group of domestic alloys based on nickel compares favorably with similar foreign alloys in their lack or limited concentration of nickel but having the same long-term strength. The properties of domestic and foreign alloys have been compared in numerous reviews, and therefore this paper will be confined to the scientific achievements and formulation of modern principles of creating heat

S. B. Maslenkov

1977-01-01

371

Utilization of titanium alloy equipment  

Microsoft Academic Search

Alloys AT-3 and AT-6 have wide application in practice in contrast to many series containing titanium alloyed with cheap obtainable elements such as aluminum, chromium, iron, silicon, and boron. Alloys AT-3 and AT-6 are processable. Extruded electrodes consisting of magnesio-thermic titanium and added alloying elements were fused twice in a vacuum arc furnace in an argon atmosphere. After machining to

N. M. Shmakov; V. S. Mikheev

1974-01-01

372

Electrochemical Behavior of Gold Alloys.  

National Technical Information Service (NTIS)

Reactions resulting from polarization of five dental golds were studied. Test materials included an ADA certified type III alloy (oro B-2) three 'economy' alloys (midas, Neycast and Minigold) and a high-fusing alloy (Olympia). The solvent was dilute lacta...

E. F. Huget S. G. Vermilyea F. A. Modawar L. B. Simon

1979-01-01

373

Heat resistance of titanium alloys  

Microsoft Academic Search

1.We determined the variation of the heat resistance of titanium alloys as a function of the character of interaction between the alloyed components, the type of equilibrium diagram of the system, and the structure of the alloy.2.We obtained experimental data on the relationship between heat resistance and the composition for some titanium systems. These relationships could be used to create

I. I. Kornilov

1963-01-01

374

A sourcebook of titanium alloy superconductivity  

NASA Astrophysics Data System (ADS)

The development, properties, and applications of Ti-based superconducting alloys are presented in a handbook based on an extensive review of published investigations. The literature is compiled and characterized in a table arranged by alloy, and individual chapters are devoted to unalloyed Ti; Ti-V binary alloys; binary Ti-Cr, Ti-Mn, Ti-Fe, Ti-Co, and Ti-Ni alloys; binary alloys of Ti with the 4d and 5d transition elements; ternary alloys of Ti with simple and transition metals; Ti-Nb binary alloys; Ti-Nb alloys with small amounts of B, C, N, or O; ternary alloys of Ti-Nb with simple metals; Soviet technical alloys; Ti-Zr-Nb alloys; other Ti-Nb-transition-metal alloys; Ti-Nb-based quaternary alloys; and amorphous Ti-alloy superconductors. Tables, graphs, diagrams, and micrographs are provided.

Collings, E. W.

1983-09-01

375

Ferromagnetic bulk amorphous alloys  

NASA Astrophysics Data System (ADS)

This article reviews our recent results on the development of ferromagnetic bulk amorphous alloys prepared by casting processes. The multicomponent Fe-(Al,Ga)-(P,C,B,Si) alloys are amorphized in the bulk form with diameters up to 2 mm, and the temperature interval of the supercooled liquid region before crystallization is in the range of 50 to 67 K. These bulk amorphous alloys exhibit good soft magnetic properties, i.e., high B s of 1.1 to 1.2 T, low H o of 2 to 6 A/m, and high ? e of about 7000 at 1 kHz. The Nd-Fe-Al and Pr-Fe-Al bulk amorphous alloys are also produced in the diameter range of up to 12 mm by the copper mold casting process and exhibit rather good hard magnetic properties, i.e., B r of about 0.1 T, high H o of 300 to 400 kA/m, and rather high ( JH)max of 13 to 20 kJ/m3. The crystallization causes the disappearance of the hard magnetic properties. Furthermore, the melt-spun Nd-Fe-Al and Pr-Fe-Al alloy ribbons exhibit soft-type magnetic properties. Consequently, the hard magnetic properties are concluded to be obtained only for the bulk amorphous alloys. The bulk Nd- and Pr-Fe-Al amorphous alloys have an extremely high T x/Tm of about 0.90 and a small ? T m(= T m- T x) of less than 100 K and, hence, their large glass-forming ability is due to the steep increase in viscosity in the supercooled liquid state. The high T x/Tm enables the development of a fully relaxed, clustered amorphous structure including Nd-Nd and Nd-Fe atomic pairs. It is, therefore, presumed that the hard magnetic properties are due to the development of Nd-Nd and Nd-Fe atomic pairs with large random magnetic anisotropy. The Nd- and Pr-based bulk amorphous alloys can be regarded as a new type of clustered amorphous material, and the control of the clustered amorphous structure is expected to enable the appearance of novel functional properties which cannot be obtained for an ordinary amorphous structure.

Inoue, Akihisa; Takeuchi, Akira; Zhang, Tao

1998-07-01

376

Fracture of iron aluminide alloys  

SciTech Connect

Five heats of iron aluminide alloys have been prepared, and their impact fracture properties compared to FA-129 iron aluminide. The first was a simple ternary alloy of iron, aluminum, and chromium to match the FA-129 composition. The second was similar but with additions of zirconium and carbon. The third alloy had zirconium, carbon, niobium and molybdenum. Two heats were produced produced with reduced aluminum contents so that a disordered body-centered cubic structure would be present. The impact properties, microstructures, and fractography of these alloys were compared to FA-129. The ductile-to-brittle transition temperatures of all of the Fe{sub 3}Al alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys had lower transition temperatures. The microstructures were, in general, coarse and anisotropic. The fracture processes were dominated by second-phase particles.

Alexander, D.J.; Sikka, V.K.

1992-01-01

377

Fracture of iron aluminide alloys  

SciTech Connect

Five heats of iron aluminide alloys have been prepared, and their impact fracture properties compared to FA-129 iron aluminide. The first was a simple ternary alloy of iron, aluminum, and chromium to match the FA-129 composition. The second was similar but with additions of zirconium and carbon. The third alloy had zirconium, carbon, niobium and molybdenum. Two heats were produced produced with reduced aluminum contents so that a disordered body-centered cubic structure would be present. The impact properties, microstructures, and fractography of these alloys were compared to FA-129. The ductile-to-brittle transition temperatures of all of the Fe{sub 3}Al alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys had lower transition temperatures. The microstructures were, in general, coarse and anisotropic. The fracture processes were dominated by second-phase particles.

Alexander, D.J.; Sikka, V.K.

1992-08-01

378

Permanent magnet alloy  

SciTech Connect

This patent describes a permanent magnet alloy consisting essentially of, in atomic percent, neodymium 8 to 15, thorium 6 to 10 with the total neodymium and thorium being within the range of 14 to 20, boron 4 to 14 and balance iron.

Narasimhan, K.S.V.L.; Ma, B.M.

1988-12-06

379

Nickel based casting alloy  

Microsoft Academic Search

A nickel base casting alloy containing 10 to 25 percent chromium, 3 to 8 percent manganese, 3 to 10 percent niobium, 0 to 3.5 percent aluminum, 0.5 to 2.0 percent beryllium which exhibits lower melting characteristics allowing enhanced compatibility to gypsum bonded investments.

A. P. Burnett; W. C. Bollinger

1985-01-01

380

Quinary metallic glass alloys  

DOEpatents

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.

Lin, Xianghong (Pasadena, CA); Johnson, William L. (Pasadena, CA)

1998-01-01

381

Quinary metallic glass alloys  

DOEpatents

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.

Lin, X.; Johnson, W.L.

1998-04-07

382

Consumable molding process for super alloys  

Microsoft Academic Search

A method of preparing a charge of super alloy material for use in metal casting is disclosed. Thin wall tubes consisting of one of the metallic elements of the alloy material, or an alloy of such element are provided. If an alloy tube is selected, all elements in the tube alloy must also be materials included in the overall formulation

Morykwas

1983-01-01

383

Casting Characteristics of Aluminum Die Casting Alloys  

Microsoft Academic Search

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

Makhlouf M. Makhlouf; Diran Apelian

2002-01-01

384

Amorphization of transition metal Zr alloys by mechanical alloying  

Microsoft Academic Search

Amorphous alloy powders of the types NiZr, CoZr, FeZr, and CuZr are produced by mechanical alloying from crystalline elemental powders. The alloying and amorphization process is monitored by microstructural investigations, x-ray diffraction, and, where applicable, by magnetization measurements. The crystallization temperatures, determined by differential scanning calorimetry, are comparable to those measured for rapidly quenched and solid state reacted amorphous metals

E. Hellstern; L. Schultz

1986-01-01

385

Laser surface alloying of silicon into aluminum casting alloys  

Microsoft Academic Search

Aluminum alloys that are easily castable tend to have lower silicon content, and hence, lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:yttrium-aluminum-garnet laser with fiber-optic beam delivery was used

Zhiyue Xu; Keng H. Leong; Paul G. Sanders

2000-01-01

386

Alloy design concepts for refined gamma titanium aluminide based alloys  

Microsoft Academic Search

The influence of the Al content and the addition of further alloying elements on the cast microstructure of ?(TiAl)+?2(Ti3Al) alloys has been examined. The results show that particularly fine and homogeneous microstructures without strong segregation can be obtained for certain alloy compositions solidifying through the ? phase. This behavior can be attributed to the avoidance of peritectic solidification and to

R. M. Imayev; V. M. Imayev; M. Oehring; F. Appel

2007-01-01

387

Transpassive dissolution of Ni–Cr alloys in sulphate solutions—comparison between a model alloy and two industrial alloys  

Microsoft Academic Search

The application of a general model for the transpassive dissolution mechanism of binary Ni-based alloys to industrial alloys, Alloy 600 and Alloy C276, containing Ni, Cr, Fe and Mo, in 1 M sulphate solutions at pH 0 and 5 is described. A comparison of the electrochemical behaviour of these two alloys to a binary Ni–15%Cr alloy is also included. The

Martin Bojinov; Gunilla Fabricius; Petri Kinnunen; Timo Laitinen; Kari Mäkelä; Timo Saario; Göran Sundholm; Kirsi Yliniemi

2002-01-01

388

Filler metal alloy for welding cast nickel aluminide alloys  

DOEpatents

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.

Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)

1998-01-01

389

Filler metal alloy for welding cast nickel aluminide alloys  

DOEpatents

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.

Santella, M.L.; Sikka, V.K.

1998-03-10

390

Corrosion of Zirconium and Zirconium Alloys.  

National Technical Information Service (NTIS)

Contents: The influence of alloying elements and heat treatment on the corrosion resistance of zirconium in water and steam; Theories on the mechanism of corrosion of zirconium and its alloys; Factors influencing hydrogen pick-up by zirconium alloys; The ...

B. G. Parfenov V. V. Gerasimov G. I. Venediktova

1969-01-01

391

Two phase titanium aluminide alloy  

DOEpatents

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.

Deevi, Seetharama C. (Midlothian, VA); Liu, C. T. (Oak Ridge, TN)

2001-01-01

392

TERNARY ALLOY-CONTAINING PLUTONIUM  

DOEpatents

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.

Waber, J.T.

1960-02-23

393

Diffusion welding of hard alloys  

Microsoft Academic Search

1.The hot pressing method, which is characterized by induction heating in graphite dies, can be used for the diffusion welding of tungsten-cobalt hard alloys and the “baking-on” of new hard-alloy layers consisting of hard-alloy powder mixtures.2.Mechanical tests have shown that the strength secured by means of diffusion welding at 1400° according to the proposed method approaches the strength of the

K. S. Gerasimenko; S. I. Spirina

1967-01-01

394

Amorphous metal alloy and composite  

DOEpatents

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.

Wang, Rong (Richland, WA); Merz, Martin D. (Richland, WA)

1985-01-01

395

Shape memory alloy actuator  

DOEpatents

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.

Varma, Venugopal K. (Knoxville, TN)

2001-01-01

396

Cobalt base alloy  

Microsoft Academic Search

A cobalt base alloy having a superior high-temperature strength and high-temperature ductility, containing, by weight, 0.15 to 2% carbon, less than 2% silicon, less than 2% manganese, 5 to 15% nickel, 18 to 35% chromium, 3 to 15% tungsten, 0.003 to 0.1% boron, 0.01 to 1% niobium, 0.01 to 1% zirconium, less than 10% iron, less than 1% tantalum, less

Y. Fukui; T. Kashimura

1984-01-01

397

Amorphous magnetic alloy  

SciTech Connect

An amorphous magnetic alloy is described having the formula Co /SUB x/ M /SUB y/ B /SUB z/ wherein M is zirconium, hafnium and/or titanium. When M is hafnium or zirconium 70x80, 8y15 and 10z16. When M is titanium, 70x72, 16y25 and 4z10. When M is hafnium together with titanium and/or zirconium, 70x80, 8y20 and 5z16.

Kanehira, J.

1984-04-03

398

Duct and cladding alloy  

DOEpatents

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.

Korenko, Michael K. (Rockville, MD)

1983-01-01

399

Glass formation in mechanically alloyed transition-metal-Zr alloys  

Microsoft Academic Search

A large number of TM-Zr alloys (where TM is a transition metal) have been produced by mechanical alloying from crystalline powders of the elements. The first milled products showed a layered microstructure of the powder particles, which became finer with increasing milling time. Longer milling led to amorphous powder. The formation of amorphous TM-Zr (TM ? Cu, Ni, Co, Fe,

E. Hellstern; L. Schultz

1987-01-01

400

Alloy Design for Nickel-Base Super Alloy Single Crystals.  

National Technical Information Service (NTIS)

The purpose of this study is to develop high creep strength Nickel-base superalloys suitable for single crystal. A computer-aided alloy design system previously developed in NRIM is applied for this purpose. Ten alloys designed contained 5 - 10 Cr, 8 - 19...

T. Yamagata

1984-01-01

401

Surface Segregation in Ternary Alloys.  

National Technical Information Service (NTIS)

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...

B. Good G. H. Bozzolo P. B. Abel

2000-01-01

402

Precipitation hardening of aluminum alloys  

Microsoft Academic Search

The author's charge was to discuss recent trends in research and development on precipitation hardened aluminum alloys and to indicate where research is needed. This will be done for three areas: fatigue, properties of grain boundaries and interfaces, and stability of precipitates at elevated temperatures. Present strong precipitation hardened aluminum alloys do not have high endurance limits. One problem is

Morris E. Fine

1975-01-01

403

Multiphase solidification in multicomponent alloys  

Microsoft Academic Search

Multiphase solidification in multicomponent alloys is pertinent to many commercial materials and industrial processes, while also raising challenging questions from a fundamental point of view. Within the past few years, research activities dedicated to multiphase solidification of ternary and multicomponent alloys experienced considerable amplification. This paper gives an overview of our present understanding in this field and the experimental techniques

U. Hecht; L. Gránásy; T. Pusztai; B. Böttger; M. Apela; V. Witusiewicz; L. Ratke; J. De Wilde; L. Froyen; D. Camel; B. Drevet; G. Faivre; S. G. Fries; B. Legendre; S. Rex

2004-01-01

404

Chloride removal from plutonium alloy  

Microsoft Academic Search

SRP is evaluating a program to recover plutonium from a metallic alloy that will contain chloride salt impurities. Removal of chloride to sufficiently low levels to prevent damaging corrosion to canyon equipment is feasible as a head-end step following dissolution. Silver nitrate and mercurous nitrate were each successfully used in laboratory tests to remove chloride from simulated alloy dissolver solution

1983-01-01

405

The fractography of casting alloys  

Microsoft Academic Search

Several types of casting alloys were fractured using various loading modes (uniaxial tension, bending, impact, and torsion, and cyclic stressing), and the corresponding mechanical properties were determined. The unetched and etched fracture surfaces and the microstructures were examined using conventional techniques. The types of casting alloys that were the subjects f these investigations include gray iron, ductile iron, cast steel,

G POWELL

1994-01-01

406

Fracture Toughness in Titanium Alloys.  

National Technical Information Service (NTIS)

Over the past decade, a concentrated effort has been made by both producers and aerospace users of titanium alloys to develop alloys for future aircraft applications. This effort has been motivated to a large extent by the advent of new design criteria an...

G. R. Keller J. C. Chesnutt F. H. Froes C. G. Rhodes

1978-01-01

407

Derivative spectrophotometry of cobalt alloys  

Microsoft Academic Search

The method of derivative spectrophotometry is briefly described, and derivative absorption spectra are presented for samarium, cobalt, and commercial Sm-Co alloys. It is shown that the use of derivative spectrophotometry not only improves the accuracy and selectivity of element determinations but also simplifies the analysis of alloys. Results of a statistical evaluation of the metrological characteristics of the analytical procedure

Spitsyn

1985-01-01

408

Titanium-tantalum alloy development  

Microsoft Academic Search

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

J. D. Cotton; J. F. Bingert; P. S. Dunn; D. P. Butt; R. W. Margevicius

1996-01-01

409

GTD111 alloy material study  

Microsoft Academic Search

Very few property data on this common turbine blade alloy have been published. As longer hours of service are accumulated, maintenance considerations such as developing optimum component life strategies and repair processes become important. The lack of specific material data hampers the effort of users and repair facilities to achieve optimum service from this alloy. This study measured some of

J. A. Daleo; J. R. Wilson

1998-01-01

410

Thermomechanical Treatment of Aluminum Alloys.  

National Technical Information Service (NTIS)

The effects of thermomechanical treatment (TMT) on the engineering properties of aluminum alloys are discussed. At present only one type of TMT seems commercially practicable. This is a T3XX type treatment for 2000 series alloy sheet. Of the other kinds o...

R. J. H. Wanhill G. F. J. A. Vangestel

1978-01-01

411

Mössbauer spectroscopy of zirconium alloys  

NASA Astrophysics Data System (ADS)

Mössbauer investigations of zirconium alloys were examined. Data about the chemical state of iron atoms in the zirconium alloys of different composition has been provided. Mössbauer spectroscopy revealed that small quantities of iron in binary zirconium alloy are in the solid solution ?-Zr (up to 0.02 wt.%). Different iron atoms concentration and thermo-mechanical treatments may lead to formation the intermetallic compounds Zr3Fe, Zr2Fe, ZrFe2. Adding tin atoms does not affect the formation and shape of Mössbauer spectra of these compounds. Adding Cr and Nb atoms makes significant changes in the shape of Mössbauer spectra and leads to the formation of complex intermetallic compounds. Adding Cu and W atoms, the shape of the binary alloys spectra (Zr-Fe) remains unchanged, but a change in the temperature dependence behavior of the spectral parameters occurs and also, changes to the properties of the alloys.

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.; Kargin, N. I.

2013-04-01

412

Design of stable nanocrystalline alloys.  

PubMed

Nanostructured metals are generally unstable; their grains grow rapidly even at low temperatures, rendering them difficult to process and often unsuitable for usage. Alloying has been found to improve stability, but only in a few empirically discovered systems. We have developed a theoretical framework with which stable nanostructured alloys can be designed. A nanostructure stability map based on a thermodynamic model is applied to design stable nanostructured tungsten alloys. We identify a candidate alloy, W-Ti, and demonstrate substantially enhanced stability for the high-temperature, long-duration conditions amenable to powder-route production of bulk nanostructured tungsten. This nanostructured alloy adopts a heterogeneous chemical distribution that is anticipated by the present theoretical framework but unexpected on the basis of conventional bulk thermodynamics. PMID:22923577

Chookajorn, Tongjai; Murdoch, Heather A; Schuh, Christopher A

2012-08-24

413

Titanium alloy production technology, market prospects and industry development  

Microsoft Academic Search

Titanium alloy with a low density, high specific strength, corrosion resistance and good process performance, is the ideal structural materials for the aerospace engineering. Based on the microstructure of titanium alloys, it can be divided into ?-type titanium alloys (heat-resistant titanium alloys), ?-type titanium alloys and ?+?-type titanium alloys. The research scopes also include the fabrication technology of titanium alloys,

Chunxiang Cui; BaoMin Hu; Lichen Zhao; Shuangjin Liu

2011-01-01

414

New magnetic alloys.  

PubMed

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. PMID:17772813

Chin, G Y

1980-05-23

415

Thermomechanical treatment of alloys  

SciTech Connect

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/sup 0/ C. and 1038/sup 0/ 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.

Bates, J.F.; Brager, R.; Paxton, M.

1983-12-20

416

New magnetic alloys  

NASA Astrophysics Data System (ADS)

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.

Chin, G. Y.

1980-05-01

417

Environmental fatigue in aluminum-lithium alloys  

Microsoft Academic Search

Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R

Robert S. Piascik

1992-01-01

418

CO2 laser welding of magnesium alloys  

Microsoft Academic Search

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The

Mohammed Dhahri; Jean Eric Masse; J. F. Mathieu; Gerard Barreau; Michel L. Autric

2000-01-01

419

Heat Treatment of New Cast Aluminum Alloys.  

National Technical Information Service (NTIS)

Contents: Brief outline of new thermally hardenable aluminum alloys included in GOST 2685-63; Heat treatment of alloys of the system Al-Mg; Heat treatment of new complex alloys based on the Al-Cu system; Heat treatment of alloys of the Al-Zn-Mg system; Ty...

N. N. Belousov E. N. Mikheeva M. N. Sarafanova

1968-01-01

420

Friction weldability of 7075 aluminium alloy  

Microsoft Academic Search

Friction welding is a solid state joining process and is widely being considered for aluminum alloys. 7075 is an aluminum alloy, with zinc as the primary alloying element. Due to its strength, high density, thermal properties, High strength precipitation hardening, 7075 aluminum alloys are extensively used in aerospace industry. It has good fatigue strength and average mach inability, but has

R. Sathish; D. Ananthapadmanaban; G. S. Nixon; V. Harish

2010-01-01

421

Shear bands in aluminum-lithium alloys  

Microsoft Academic Search

Lithium-alloyed aluminum alloys possess substantial advantages over other aluminum-base alloys and can be a promising material\\u000a for spacecraft engineering in the next century. At the present time the use of these alloys is limited by certain manufacturing\\u000a difficulties. For example, the shear bands that appear in rolling of Al?Li sheets exert a negative effect on the properties\\u000a of the alloys.

T. D. Rostova; V. V. Zakharov

1997-01-01

422

The fractography of casting alloys  

SciTech Connect

Several types of casting alloys were fractured using various loading modes (uniaxial tension, bending, impact, and torsion, and cyclic stressing), and the corresponding mechanical properties were determined. The unetched and etched fracture surfaces and the microstructures were examined using conventional techniques. The types of casting alloys that were the subjects f these investigations include gray iron, ductile iron, cast steel, and aluminum-base alloys (A380, A356, and 319). The fractographic studies have yielded these generalizations regarding the topography of the fracture surfaces. In the case of low-ductility alloys such as gray iron and the aluminum-base alloys, the tensile edge of a fracture surface produced by a stress system with a strong bending-moment component has a highly irregular contour, whereas the compressive edge of the fracture surface is quite straight and parallel to the bend axis. On the other hand, the periphery of a fracture surface produced by uniaxial tension has a completely irregular contour. The fracture surface produced by cyclic loading of a gray iron does not display any macroscopic evidence (such as a thumb nail) of the loading mode. However, the fracture surface of each of the other casting alloys displays clear, macroscopic evidence of failure induced by fatigue. The aluminum-base alloys fracture completely within the interdendritic region of the microstructure when subjected to monotonic loading by uniaxial tension or bending, whereas a fatigue crack propagates predominantly through the primary crystals of the microstructure.

Powell, G.W. (Ohio State Univ., Columbus, OH (United States))

1994-10-01

423

Some thoughts on alloy design  

SciTech Connect

This paper discusses some of the problems associated with attempts to use first principles in alloy design. We briefly summarize the role of microstructure on the properties of high temperature alloys and illustrate some of the microstructural features of conventional superalloys. We also describe how theory and experiment are converging toward some predictive capabilities for relating microstructure and composition using Ni-Al-Mo-X alloys as an example. Finally, this paper suggests that progress is being made in combining the results of condensed matter theory and experimental research.

Martin, P.L.; Williams, J.C.

1984-01-01

424

Hot-Dip Galvanizing Alloys  

NASA Astrophysics Data System (ADS)

Activity in the development of hotdip galvanizing alloys has been quite successful in achieving two major goals. First, the use of a zinc-nickel bath provides a workable solution to the problem of batch galvanizing reactive steels, to achieve both an attractive surface appearance and a thin, durable and protective coating. Second, for continuously galvanized steel products, specific zinc-aluminum alloys have provided a means to greatly increase corrosion resistance, increase the maximum use temperature of zinc coatings, achieve the fabrication of severely formed products without damage to the zinc alloy coating, and allow such products to be formed from prepainted as well as unpointed coated steel.

Lynch, Richard F.

1987-08-01

425

A new approach to refining and modifying cast aluminum alloys with rare earth alloys  

Microsoft Academic Search

The effects of rare earth (RE) alloys on the refining and modifying of cast aluminum alloys were investigated. Compared to\\u000a other substances in common use, rare earth alloys maintain the refining and modifying effects of the aluminum alloys for a\\u000a longer time. RE alloys can also reduce environmental pollution in the melting process. These effects of RE alloys make them

Duo-guang Tang; Xie-min Mao

2000-01-01

426

Synthesis of nanocrystalline copper–tungsten alloys by mechanical alloying  

Microsoft Academic Search

Copper–tungsten exhibits total absence of solubility in both solid and liquid state. Mechanical alloying (MA) as a solid state, non-equilibrium process can be beneficial to the processing of such an immiscible system with the added features of refinement of structure. A study was undertaken to synthesise various Cu–W alloys and develop an ultrafine microcomposite structure of tungsten in copper matrix

T. Raghu; R. Sundaresan; P. Ramakrishnan; T. R. Rama Mohan

2001-01-01

427

Current status of ductile tungsten alloy development by mechanical alloying  

Microsoft Academic Search

There were considerable differences in ductility and recrystallization temperatures among fine-grained, carbide-dispersed tungsten alloys developed so far by mechanical alloying, followed by sintering and hot working. The differences are attributable mainly to three microstructural factors giving detrimental effects on the ductility and recrystallization temperature; (1) precipitation of the brittle W2C phase, (2) heterogeneity in grain size and particle distributions and

Y. Ishijima; H. Kurishita; K. Yubuta; H. Arakawa; M. Hasegawa; Y. Hiraoka; T. Takida; K. Takebe

2004-01-01

428

Exchange interactions and Curie temperatures in Cr-based alloys in the zinc blende structure: Volume- and composition-dependence from first-principles calculations  

NASA Astrophysics Data System (ADS)

We present calculations of the exchange interactions and Curie temperatures in Cr-based pnictides and chalcogenides of the form CrX , with X=As , Sb, S, Se, and Te, and the mixed alloys CrAs50X50 , with X=Sb , S, Se, and Te. The calculations are performed for zinc blende structure for 12 values of the lattice parameter between 5.44 and 6.62Å , appropriate for some typical II-VI and III-V semiconducting substrates. Electronic structure is calculated via the linear muffin-tin-orbitals (LMTOs) method in the atomic sphere approximation (ASA) using empty spheres to optimize ASA-related errors. Whenever necessary, the results have been verified using the full-potential version of the method, FP-LMTO. The disorder effect in the As-sublattice for CrAs50X50 (X=Sb,S,Se,Te) alloys is taken into account via the coherent-potential approximation. Exchange interactions are calculated using the linear-response method for the ferromagnetic (FM) reference states of the alloys as well as the disordered local moments (DLM) states. These results are then used to estimate the Curie temperature from the low- and high-temperature sides of the ferromagnetic-paramagnetic transition. Estimates of the Curie temperature are provided based on the mean field and the more accurate random-phase approximations. Dominant antiferromagnetic exchange interactions for some low values of the lattice parameter for the FM reference states in CrS, CrSe, and CrTe prompted us to look for antiferromagnetic (AFM) configurations for these systems with energies lower than the corresponding FM and DLM values. Results for a limited number of such AFM calculations are discussed, identifying the AFM[111] state as a likely candidate for the ground state for these cases.

Bose, S. K.; Kudrnovský, J.

2010-02-01

429

Shape memory alloy cables  

NASA Astrophysics Data System (ADS)

Conventional structural cables (or wire ropes) are composed of steel wires helically wound into strands, which, in turn, are wound around a core. Cables made from shape memory alloy (SMA) wires are a new structural element with promising properties for a broad range of new applications. Among the many potential advantages of this form are increased bending flexibility for spooling/packaging, better fatigue performance, energy absorption and damping, reduced thermal lag, redundancy, and signicant design flexibility. Currently there are no known studies of SMA cables in the literature, so exploratory thermo-mechanical experiments were performed on two commercially available cable designs as part of an ongoing research program to systematically characterize their thermomechanical behavior and demonstrate their potential utility as adaptive or resilient tension elements.

Reedlunn, Benjamin; Shaw, John A.

2008-05-01

430

High strength ferritic alloy  

DOEpatents

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.

Hagel, William C. (Ann Arbor, MI); Smidt, Frederick A. (Springfield, VA); Korenko, Michael K. (Richland, WA)

1977-01-01

431

Copper alloys for industrial hardware  

SciTech Connect

Copper and its alloys are widely used because of their excellent electrical and thermal conductivities, outstanding resistance to corrosion, and ease of fabrication. Lifecycle costs are another important reason for new and expanding applications for copper and copper alloys. For example, lifecycle cost analyses favor the use of copper-nickel for automotive brake tubes, and copper alloys in molds for plastic parts. However, copper also competes very well on a first-cost basis in the brazed copper-and-brass radiator, and in free-cutting brass machined components. This article highlights four specific applications in which advanced copper alloys and fabrication techniques enhance the performance of industrial hardware, based largely on conductivity, corrosion resistance, and lifecycle costs.

Peters, D.T. [Copper Development Association Inc., New York, NY (United States)

1996-10-01

432

Micromodeling of Aerospace Structural Alloys.  

National Technical Information Service (NTIS)

The project undertaken was designed to supplement and support work at Northwestern University under the direction of Prof. James Conley. The basic premise of the program is to develop methodology so that aluminum and titanium alloy castings can be designe...

B. J. Yang D. M. Stefanescu R. Ruxanda

2000-01-01

433

Military applications for ? titanium alloys  

NASA Astrophysics Data System (ADS)

Beta alloys are potentially useful for several types of nonaerospace military applications. The potential applications to be discussed in this article include armor, body armor, mortar barrels, and missile launch canisters.

Fanning, J. C.

2005-12-01

434

Tritium Production from Palladium Alloys  

SciTech Connect

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.

Claytor, T.N.; Schwab, M.J.; Thoma, D.J.; Teter, D.F.; Tuggle, D.G.

1998-04-19

435

Cyclic Strength of Titanium Alloys.  

National Technical Information Service (NTIS)

Results of fatigue and corrosion fatigue tests of certain titanium alloys, materials that show promise in transport ship building, are presented. Tests for low cyclic fatigue in a corrosive environment revealed marked reduction in longevity of notched spe...

E. D. Shekhovstsev E. N. Kostrov Y. E. Zobachev

1972-01-01

436

Casting Characteristics of Aluminum Die Casting Alloys  

SciTech Connect

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.

Makhlouf M. Makhlouf; Diran Apelian

2002-02-05

437

Building Structures from Aluminum Alloys (Collection of Articles).  

National Technical Information Service (NTIS)

Contents: Basic problems in preparation for broad application of aluminum alloys in construction, Contemporary aluminum alloys, Aluminum alloys in civil construction, Investigation of physico-mechanical properties of aluminum alloys D1-T, D16-T, AMg61, an...

S. V. Taranovskii

1965-01-01

438

Environmentally Assisted Cracking of Nickel Alloys: A Review.  

National Technical Information Service (NTIS)

Nickel can dissolve a large amount of alloying elements while still maintaining its austenitic structure. That is, nickel based alloys can be tailored for specific applications. The family of nickel alloys is large, from high temperature alloys (HTA) to c...

R. B. Rebak

2004-01-01

439

Kinetics of aluminum lithium alloys  

Microsoft Academic Search

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

Ben A. Pletcher

2009-01-01

440

Volatilization from PCA steel alloy  

SciTech Connect

The mobilizations of key components from Primary Candidate Alloy (PCA) steel alloy have been measured with laboratory-scale experiments. The experiments indicate most of the mobilization from PCA steel is due to oxide formation and spalling but that the spalled particles are large enough to settle rapidly. Based on the experiments, models for the volatization of iron, manganese, and cobalt from PCA steel in steam and molybdenum from PCA steel in air have been derived.

Hagrman, D.L.; Smolik, G.R.; McCarthy, K.A.; Petti, D.A.

1996-08-01

441

Precipitation hardening of aluminum alloys  

Microsoft Academic Search

The author’s charge was to discuss recent trends in research and development on precipitation hardened aluminum alloys and\\u000a to indicate where research is needed. This will be done for three areas: fatigue, properties of grain boundaries and interfaces,\\u000a and stability of precipitates at elevated temperatures. Present strong precipitation hardened aluminum alloys do not have\\u000a high endurance limits. One problem is

Morris E. Fine

1975-01-01

442

Alloys for Orthopaedic Implant Use  

Microsoft Academic Search

The paper compares four alloys in orthopaedic implant use on the basis of their performance in laboratory tests. The alloys compared were cast Co–Cr–Mo, powder metallurgy (PM) Co–Cr–Mo, Ti 318 and Ti 550. Tensile, corrosion fatigue, and corrosion tests were carried out and the effect of heat treatment and of surface treatment was investigated. The corrosion fatigue tests ranked the

H S Dobbs; J L M Robertson

1982-01-01

443

Cavitation erosion of aluminium alloys  

Microsoft Academic Search

Cast aluminium-silicon, cast aluminium-zinc and mechanically alloyed aluminium alloys were eroded in distilled water using a 20 kHz ultrasonic vibratory device. The erosion was measured by weight loss, and the damaged surface was examined using metallographic and profilometric techniques. The maximum differences in the incubation period, in the linear erosion rate and in the mass loss after a 10 h

W. J. Tomlinson; S. J. Matthews

1994-01-01

444

Superplastic forming of alloy 718  

SciTech Connect

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.

Smith, G.D.; Flower, H.L. (Inco Alloys International Inc., Huntington, WV (United States))

1994-04-01

445

Lithium alloy anode for thermal cells  

SciTech Connect

This patent describes as an article of manufacture, an anode wafer for a thermal cell, the anode wafer comprising particles of a lithium anode alloy bonded with particles of a metal binder, the lithium anode alloy being of the class consisting of lithium-aluminum alloys; lithium-silicon alloys; and lithium-boron alloys, the metal binder being of the class consisting of unalloyed iron, copper, nickel, manganese; and mixtures thereof, and wherein substantially all the metal binder in the wafer remains present as a discrete phase, unalloyed with the lithium alloy.

Cupp, E.B.; Cottingham, D.R.

1986-12-02

446

Ni{sub 3}Al aluminide alloys  

SciTech Connect

This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

Liu, C.T.

1993-10-01

447

Fabrication and characterization of GaSb based thermophotovoltaic cells using Zn diffusion from a doped spin-on glass source  

SciTech Connect

The GaInSb material system is attractive for application in thermophotovoltaic (TPV) cells since its band gap can be tuned to match the radiation of the emitter. At present, most of the TPV cells are fabricated using epitaxial layers and hence are expensive. To reduce the cost, Zn diffusion using elemental vapors in a semi-closed diffusion system is being pursued by several laboratories. In this paper, the authors present studies carried out on Zn diffusion into n-type (Te-doped) GaSb substrates in an open tube diffusion furnace. The dopant precursor was a 2,000 {angstrom} thick, zinc doped spin-on glass. The diffusion was carried out at temperatures ranging from 550 to 600 C, for times from 1 to 10 h. The diffused layers were characterized by Hall measurements using step-and-repeat etching by anodic oxidation, secondary ion mass spectrometry measurements, and TPV device fabrication. For diffusion carried out at 600 C, the junction depth was 0.3 {micro}m, and the hole concentration near the surface was 5 x 10{sup 19}/cm{sup 3}. The external quantum efficiency, measured without any anti-reflection coating of the TPV cells fabricated using mesa-etching had a maximum value of 38%. Masked diffusion was also carried out by opening windows in a Si{sub 3}N{sub 4} coated, GaSb wafer. TPV cells fabricated on these structures had similar quantum efficiency, but lower dark current.

Dakshinamurthy, S.; Shetty, S.; Bhat, I.; Hitchcock, C.; Gutmann, R.; Charache, G.; Freeman, M.

1999-04-01

448

Fabrication and characterization of GaSb based thermophotovoltaic cells using Zn diffusion from a doped spin-on glass source  

SciTech Connect

The GaInSb material system is attractive for application in thermophotovoltaic (TPV) cells since its band gap can be tuned to match the radiation of the emitter. At present, most of the TPV cells are fabricated using epitaxial layers and hence are expensive. To reduce the cost, Zn diffusion using elemental vapors in a semi-closed diffusion system is being pursued by several laboratories. In this paper, the authors present studies carried out on Zn diffusion into n-type (Te-doped) GaSb substrates in an open tube diffusion furnace. The dopant precursor was a 2,000 {angstrom} thick, zinc doped spin-on glass. The diffusion was carried out at temperatures ranging from 550 to 600 C, for times from 1 to 10 hours. The diffused layers were characterized by Hall measurements using step-and-repeat etching by anodic oxidation, secondary ion mass spectrometry (SIMS) measurements and TPV device fabrication. For diffusion carried out at 600 C, the junction depth was 0.3 {micro}m, and the hole concentration near the surface was 5 {times} 10{sup 19}/cm{sup 3}. The external quantum efficiency, measured without any anti-reflection coating, of the TPV cells fabricated using mesa-etching had a maximum value of 38%. Masked diffusion was also carried out by opening windows in a Si{sub 3}N{sub 4} coated, GaSb wafer. TPV cells fabricated on these structures had similar quantum efficiency, but lower dark current.

Dakshinamurthy, S.; Shetty, S.; Bhat, I.; Hitchcock, C.; Gutmann, R. [Rensselaer Polytechnic Inst., Troy, NY (United States); Charache, G.; Freeman, M. [Lockheed Martin Corp., Schenectady, NY (United States)

1998-06-01

449

Oxidation mechanisms for alloys in single-oxidant gases  

Microsoft Academic Search

Scales formed on alloys invariably contain the alloy constituents in a ratio different from that in the alloy, owing to the differing thermodynamic tendencies of the alloy components to react with the oxidant and to differences in diffusion rates in scale and alloy phases. This complex interrelationship between transport rates and the thermodynamics of the alloy-oxidant system can be analyzed

Whittle

1981-01-01

450

Alloy Design and Properties Optimization of High-Entropy Alloys  

NASA Astrophysics Data System (ADS)

This article reviews the recent work on the high-entropy alloys (HEAs) in our group and others. HEAs usually contain five or more elements, and thus, the phase diagram of HEAs is often not available to be used to design the alloys. We have proposed that the parameters of ? and ? can be used to predict the phase formation of HEAs, namely ? ? 1.1 and ? ? 6.6%, which are required to form solid-solution phases. To test this criterion, alloys of TiZrNbMoV x and CoCrFeNiAlNb x were prepared. Their microstructures mainly consist of simple body-centered cubic solid solutions at low Nb contents. TiZrNbMoV x alloys possess excellent mechanical properties. Bridgman solidification was also used to control the microstructure of the CoCrFeNiAl alloy, and its plasticity was improved to be about 30%. To our surprise, the CoCrFeNiAl HEAs exhibit no apparent ductile-to-brittle transition even when the temperatures are lowered from 298 K to 77 K.

Zhang, Y.; Yang, X.; Liaw, P. K.

2012-07-01

451

Production of intergranular attack of alloy 600, alloy 690, and alloy 800 tubing in tubesheet crevices: Topical report  

SciTech Connect

Three model boilers, manufactured to simulate full-size tube sheet crevices, were tested with various secondary side environments. The first was faulted with organics representative of the decomposition of humic acid. The second was faulted with sodium carbonate and sodium hydroxide, while the third was faulted with sodium sulfate and sodium hydroxide. Each model contained seven tubes, which included Alloy 600 in the mill-annealed (MA) and thermally-treated (TT) conditions and Alloy 690 in the thermally-treated condition. Two models contained Alloy 800 tubes in the mill-annealed condition and one had Alloy 800 in the mill-annealed/cold-worked/glass-bead-peened condition. Two different sizes of tubesheet crevices were used in all model boilers. In the organics-faulted boiler, tubes of Alloy 600MA, Alloy 690TT and Alloy 800MA experienced no significant intergranular attack (IGA); however, the Alloy 600TT had intergranular attack (IGA) three to four grains deep. The carbonate-caustic faulted boiler experienced throughwall stress corrosion cracking (SCC) in all tubes of Alloy 600 MA and Alloy 800 MA. Eddy current indications were present in Alloy 690TT, Alloy 600TT and Alloy 800 in the mill-annealed/cold worked/glass-bead-peened condition. Metallographic examination of tubes from the third model boiler, faulted with sodium sulfate and caustic, revealed IGA in the mill-annealed Alloy 600 tubes. The IGA was more extensive in an Alloy 600 tube annealed at 1700/sup 0/F than an Alloy 600 tube annealed at 1875/sup 0/F.

Scott, D.B.; Glaves, C.L.,

1987-07-01

452

Kinetics of aluminum lithium alloys  

NASA Astrophysics Data System (ADS)

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)

Pletcher, Ben A.

453

Dissolution of particles in binary alloys.  

National Technical Information Service (NTIS)

This work has primarily been concentrated upon modeling of the dissolution process of particles in binary alloys during isothermal annealing. Also, a comprehensive experimental investigation of the dissolution kinetics in two AlSi-alloys under isothermal ...

U. H. Tundal

1992-01-01

454

Aluminum-Lithium Alloys with Scandium  

Microsoft Academic Search

Aluminum-lithium alloys with diminished density and high crack resistance characteristics are widely used in aircraft. Scandium additives to this alloy improve the strength properties and considerably enhance the weldability.

N. I. Kolobnev

2002-01-01

455

Ion Exchange Analysis of Columbium Alloys.  

National Technical Information Service (NTIS)

An ion-exchange method developed at AMRA (see AD-653 767) was applied to the analysis of synthetic mixtures representing various columbium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titaniu...

T. A. Ferraro

1967-01-01

456

Partial Denture Alloy-Denture Cleanser Interaction.  

National Technical Information Service (NTIS)

The electrochemical behavior of three partial denture casting alloys was studied. Under simulated conditions of denture storage, only one test alloy exhibited spontaneous active-passive transition. The findings contraindicate the use of five widely used m...

E. F. Huget S. G. Vermilyea F. A. Modawar

1980-01-01