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1

Ordering-enhanced dislocation glide in III-V alloys  

NASA Astrophysics Data System (ADS)

Ordering-induced effects on dislocations in metallic alloys have been extensively studied due to their importance in technology applications. We demonstrate that dislocation behavior in ordered III-V semiconductor alloys can be drastically different. This is because ordering in bulk metallic alloys is generally stable, whereas the surface-stabilized group-III sublattice ordering of a III-V alloy is only metastable in the bulk. Here, we show that dislocation glide can release some of the energy stored by ordering of III-V alloys, enhancing the glide of any dislocation which cuts through the ordered layers to create an antiphase boundary in the ordering pattern. This leads to an experimentally observed glide-plane switch which is unique to ordered III-V alloys. Implications for other unique strain-relaxation processes in III-V ordered alloys are also discussed.

McMahon, William E.; Kang, Joongoo; France, Ryan M.; Norman, Andrew G.; Friedman, Daniel J.; Wei, Su-Huai

2013-11-01

2

III-V alloy heterostructure high speed avalanche photodiodes  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

3

Close Correlation between Enthalpy of Mixing and Internal Strain Energy in III V Compound Alloys  

NASA Astrophysics Data System (ADS)

The correlation of enthalpy of mixing and internal strain energy calculated by the elastic sphere model has been studied for III V ternary alloy semiconductors of the AB0.5C0.5 type. A plot of the enthalpy of mixing and the internal strain energy on a plane for 18 different alloy systems shows nearly linear correlation. This result strongly supports the conclusion drawn in our previous paper that the immiscibility domains, in which the alloys are not formed completely, for III V alloys can be predicted simply from the isoenergy chart obtained by the elastic sphere model.

Oyama, Katsushi; Uda, Hiroshi; Ikegami, Seiji; Sonomura, Hajimu

1999-11-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

5

Effective band structure of random III-V alloys  

NASA Astrophysics Data System (ADS)

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

Popescu, Voicu; Zunger, Alex

2010-03-01

6

On the importance of the band gap bowing in Boron-based III V ternary alloys  

NASA Astrophysics Data System (ADS)

The optical band gap bowing of eighteen III-V compound alloys containing boron is calculated by means of a recent phenomenological model [M. Ferhat, Phys. Status Solidi b 241 (2004) R38]. The optical band gap bowing is found to be strong for the all studied III-V boron alloys. In particular, we find that BNSb shows an important optical band gap bowing of 19.78 eV. Parallel to this, we also introduce ab initio pseudopotential plane wave calculations with large relaxed supercells to check the validity of our phenomenological model for BNSb. This gives an optical bowing of 21.19 eV, in fairly good agreement with the model used. Results suggest that the III-V boron alloys are characterized by a strong competition between the volume deformation (b), charge transfer (b), and structural relaxation (b) effects. For the common cation alloys b dominates b, and b is relatively weak; whereas for the common anion alloys, the structural effect ( b and b) appears to control the total optical band gap bowing.

Azzi, S.; Zaoui, A.; Ferhat, M.

2007-11-01

7

Surface segregation and ordering in III-V semiconductor alloys  

SciTech Connect

Using the first-principles total-energy pseudopotential method, we have studied the formation energy of the (001) Ga{sub 1{minus}{ital x}}In{sub {ital x}}P alloy surface as a function of composition and reconstruction. The results are presented as {ital T}=0 surface stability diagrams that show the lowest energy reconstruction and cation occupation pattern as functions of the chemical potentials. Slightly different stability diagrams emanate depending on whether or not there is equilibrium between the surface and the bulk. The stability diagrams show a pronounced asymmetry between the Ga- and In-rich regions. The asymmetry is interpreted in terms of the size difference between In and Ga and the effect of this size difference on the bonding geometry. For surfaces in equilibrium with the bulk, we find a strong dependence of surface segregation on the surface reconstruction, and we predict a Ga enrichment of the surface in the moderate cation-rich limit and In enrichment in the anion-rich region. This result suggests a way to achieve abrupt interfaces in semiconductor heterostructures. For surfaces not in equilibrium with the bulk, we identify regions in the stability diagram where surface-induced CuPt ordering (both type {ital A} and type {ital B}) occurs. {copyright} {ital 1996 The American Physical Society.}

Froyen, S.; Zunger, A. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

1996-02-01

8

Theoretical and experimental study of solid phase miscibility gaps in III/V quaternary alloys  

NASA Astrophysics Data System (ADS)

The first 8 years of this DOE supported research was directed toward understanding, for the first time, the thermodynamics of miscibility gaps and ordering in III/V alloys. This research has led to the publication of 32 papers in technical journals as well as 17 invited papers and national and international conferences. In addition, this work led directly to the invitation to organize the Joint U.S./Japan Workshop on Alloy Semiconductor Physics and Electronics. A brief project summary, a listing of papers and talks, and a section devoted to supported and graduated students are contained.

Stringfellow, G. B.

1989-06-01

9

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

10

Thermodynamic analysis of III-V semiconductor alloys grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

A thermodynamic analysis has been applied to systematically study III-V semiconductor alloy deposition, including nitrides grown by metalorganic vapor phase epitaxy. The predicted solid compositions of a number of ternary and quaternary alloys, including AlxGa1-xPyAs1-y, are compared with experimental data. For phosphorus-containing alloys, introduction of a parameter f representing incomplete PH3 pyrolysis yields good agreement with experimental data. It is shown that the input mole fraction of the group III metalorganic sources influences the incorporation of P into the solid for these alloys. Solid composition is also calculated for nitride alloys as a function of inlet gas concentration. To date, thermodynamic models have been applied solely to predict N solubility limits for nitride alloys where mixing occurs on the group V sublattice. The present model is used to predict N solid compositions in ternary and quaternary alloys, and it is demonstrated that these values are below the theoretical solubility limits for In-containing nitrides. The role of H2 in the carrier gas is investigated for III-N-V, III-III-N-V, and III-N-V-V systems.

Asai, Toshihiro; Dandy, David S.

2000-10-01

11

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

12

A modified simplified coherent potential approximation model of band gap energy of III-V ternary alloys  

NASA Astrophysics Data System (ADS)

Based on the modification of the simplified coherent potential approximation (SCPA), a model is developed to calculate the composition dependence of the band gap energy of III-V ternary alloys with the same anion. The derived equation is used to fit the experimental band gap energy of In x Al1- x N, In x Ga1- x N and Al x Ga1- x N with x from 0 to 1. It is found that the fitting results are better than those done by using SCPA. The fitting results are also better than those obtained by using the formula with a small bowing coefficient, especially for In x Al1- x N. In addition, our model can also be used to describe the composition dependence of band gap energy of other III-V ternary alloys.

Zhao, ChuanZhen; Zhang, Rong; Liu, Bin; Fu, DeYi; Li, Ming; Xiu, XiangQian; Xie, ZiLi; Zheng, YouDou

2012-03-01

13

Computer modeling study of monolithic three-junction solar cells composed of III-V ternary alloys  

NASA Astrophysics Data System (ADS)

Monolithic three-junction solar cells composed of III-V ternary alloys have been studied using a computer model. InGaAs was used as the low-bandgap material, either AlGaAs or GaAsP was used as the high-bandgap material, and any of these alloys were used for the middle-bandgap junction. Tunnel junctions were assumed to electrically connect the subcells. The model included the losses resulting from finite quantum efficiencies, current mismatch, finite gridline, contact and emitter sheet resistances, the voltage drop across the electrical interconnects between the subcells, shadowing, reflection, and absorption by the window. Measured values (or estimated values whenever the relevant data are unavailable) of the appropriate material parameters were included. Practical cell conversion efficiencies as high as 32 percent were obtained for one-sun, AM0 conditions. The sensitivity of the device to various radiation conditions was also calculated.

Hamaker, H. C.

14

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

NASA Astrophysics Data System (ADS)

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

Mourad, D.; Czycholl, G.

2012-05-01

15

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

16

Electron scattering by native defects in III-V nitrides and their alloys  

SciTech Connect

We have calculated the electron mobilities in GaN and InN taking into consideration scattering by short range potentials, in addition to all standard scattering mechanisms. These potentials are produced by the native defects which are responsible for the high electron concentrations in nominally undoped nitrides. Comparison of the calculated mobilities with experimental data shows that scattering by short range potentials is the dominant mechanism limiting the electron mobilities in unintentionally doped nitrides with large electron concentrations. In the case of Al{sub x}Ga{sub 1-x}N alloys, the reduction in the electron concentration due to the upward shift of the conduction band relative to the native defect level can account for the experimentally measured mobilities. Resonant scattering is shown to be important when the defect and Fermi levels are close in energy.

Hsu, L. [Univ. of California, Berkeley, CA (United States). Department of Physics; Walukiewicz, W. [Univ. of California, Berkeley, CA (United States). Ernest Orlando Lawrence Berkeley National Laboratory

1996-03-01

17

Realization of wide electron slabs by polarization bulk doping in graded III-V nitride semiconductor alloys  

NASA Astrophysics Data System (ADS)

We present the concept and experimental realization of polarization-induced bulk electron doping in III-V nitride semiconductors. By exploiting the large polarization charges in the III-V nitrides, we are able to create wide slabs of high-density mobile electrons without introducing shallow donors. Transport measurements reveal the superior properties of the polarization-doped electron distributions than comparable shallow donor-doped structures, especially at low temperatures due to the removal of ionized impurity scattering. Such polarization-induced three-dimensional electron slabs can be utilized in a variety of device structures owing to their high conductivity and continuously changing energy gap.

Jena, Debdeep; Heikman, Sten; Green, Daniel; Buttari, Dario; Coffie, Robert; Xing, Huili; Keller, Stacia; Denbaars, Steve; Speck, James S.; Mishra, Umesh K.; Smorchkova, Ioulia

2002-12-01

18

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

19

Percolation model for long wave phonons in random zincblende alloys: from II-VI's to III-V's  

Microsoft Academic Search

We propose a simplified version of our 1-bond 2-mode percolation model initially developed for the q 0 phonon properties of the stiff Be-VI bond in (Zn,Be)-chalcogenides, which open the class of random mixed crystals with contrast in the bond stiffness. The simplified version applies to the usual alloys, i.e. made of soft-like bonds only. It is derived from detailed comparison

A. Chafi; O. Pagès; D. Fristot; A. V. Postnikov; T. Tite; J. P. Laurenti; D. Bormann; O. Maksimov; M. C. Tamargo

2006-01-01

20

Empirical tight-binding calculations of the electronic structure of dilute III-V-N semiconductor alloys  

NASA Astrophysics Data System (ADS)

We present empirical tight-binding (TB) calculations of the electronic structure of GaP1-xNx and InyGa1-yAs1-xNx alloys with low nitrogen content (x<0.05) over the entire Brillouin zone. Following the method recently developed for GaAs1-xNx [Shtinkov et al., Phys. Rev. B 67, 081202 (2003)], we add to the TB basis an additional anion s orbital (sN) in order to account for the N-induced change of the electronic structure. The band structures of GaP1-xNx and InyGa1-yAs1-xNx are calculated using an sp3d5s*sN TB parametrization. Our TB results are in excellent agreement with experimental and other theoretical data without introducing any additional fitting parameters, demonstrating that the developed method is a promising tool for modeling a wide range of dilute nitride materials and heterostructures. .

Turcotte, S.; Shtinkov, N.; Desjardins, P.; Masut, R. A.; Leonelli, R.

2004-05-01

21

III-V compounds under strain and compression  

NASA Astrophysics Data System (ADS)

This work uses density functional theory within the local density approximation (LDA) and the generalized gradient approximation to investigate the electronic and structural properties of group III-V compounds under conditions of strain and compression, with primary emphasis on the III-V nitrides. The III-V nitrides are of particular importance in semiconductor devices because of their wide band gaps, large piezoelectric response, and spontaneous polarization allowed by the wurtzite structure. Polarization induced bound charge arising from differences between opposite sides of a III-V nitride heterojunction is also useful in creating quasi-two dimensional electron gases with large carrier concentrations. All of the III-V nitrides, including BN and TlN, are examined in this work, with a prediction for the lattice constants of TlN in wurtzite. In Chapter 2, local densities of state for Al0.25Ga0.75N and InN are determined and agree well with experimental measurements from electron energy loss spectra. The behavior of the structure parameters of all III-V nitrides in the wurtzite structure under biaxial and uniaxial compression are determined in Chapter 3, along with various elastic constants and moduli. Using the Berry Phase concept, the spontaneous polarization and the piezoelectric polarization arising from biaxial strain are determined for all III-V nitrides in the wurtzite structure in Chapter 4. Calculation of the spontaneous polarization of selected III-V ternary nitride alloys then allows determination of the bound charge induced by polarization differences at AlxGa 1-xN/GaN and InxT 1-xN/TlN interfaces. Finally, in Chapter 5 a systematic study of all III-V compounds under hydrostatic compression is undertaken, and calculated enthalpies are used to determine transition pressures between structural phases, with a possible stable phase of sc16 predicted in the boron III-V compounds other than BN.

Alldredge, Erik Scott

22

Dry etching of III-V nitrides  

SciTech Connect

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

Pearton, S.J. [Florida Univ., Gainesville, FL (United States); Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States); McLane, G.F. [Army Research Laboratory, Ft. Monmouth, NJ (United States); Constantine, C. [Plasma Therm IP, St. Petersburg, FL (United States)

1995-12-01

23

Progress and continuing challenges in GaSb-based III V alloys and heterostructures grown by organometallic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

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 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.

Wang, C. A.

2004-12-01

24

Modeling the elastic properties of the ternary III-V alloys InGaAs, InAlAs and GaAsSb using Tersoff potentials for binary compounds  

NASA Astrophysics Data System (ADS)

This work evaluates the suitability of the empirical Tersoff potential for structural calculations in ternary III-V alloys, using parameter sets for the corresponding binary compounds. In particular, the elastic properties of randomly alloyed InxGa1 - xAs, InxAl1 - xAs and GaAs1 - xSbx are compared to values obtained experimentally over the whole composition range. Different In-As interactions were evaluated for InxGa1 - xAs to provide an optimum fit around the technologically relevant composition of 53% In, required for lattice-matching with InP substrates. The experimental values of the bulk modulus were reproduced with an error well below 5% for all three ternaries, while the calculations led to deviations in the shear modulus of up to 13%. For the particular compositions, lattice-matched to InP, the error in the bulk modulus is well below 2%, while for the shear modulus an error around 10% has to be expected, according to this analysis.

Detz, H.; Strasser, G.

2013-08-01

25

Engineering InAs(x)P(1-x)/InP/ZnSe III-V alloyed core/shell quantum dots for the near-infrared.  

PubMed

Quantum dots with a core/shell/shell structure consisting of an alloyed core of InAs(x)P(1-x), an intermediate shell of InP, and an outer shell of ZnSe were developed. The InAs(x)P(1-x) alloyed core has a graded internal composition with increasing arsenic content from the center to the edge of the dots. This compositional gradient results from two apparent effects: (1) the faster reaction kinetics of the phosphorus precursor compared to the arsenic precursor, and (2) a post-growth arsenic-phosphorus exchange reaction that increases the arsenic content. The cores have a zinc blend structure for all compositions and show tunable emission in the near-infrared (NIR) region. A first shell of InP leads to a red-shift and an increase in quantum yield. The final shell of ZnSe serves to stabilize the dots for applications in aqueous environments, including NIR biomedical fluorescence imaging. These NIR-emitting core/shell/shell InAs(x)P(1-x)/InP/ZnSe were successfully used in a sentinel lymph node mapping experiment. PMID:16045339

Kim, Sang-Wook; Zimmer, John P; Ohnishi, Shunsuke; Tracy, Joseph B; Frangioni, John V; Bawendi, Moungi G

2005-08-01

26

The III-V photocathode - A major detector development.  

NASA Technical Reports Server (NTRS)

Description of new (III-V) photocathodes which show improvements in sensitivity of as much as ten to a hundred times over conventional cathodes in the near infrared and useful improvements at shorter wavelengths. The development stems from a combination of basic knowledge of the photoemission process, gained in the 1950s, and the advancing understanding of the technology of III-V materials, in the 1960s. The superior performance of these cathodes is due to the fact that the vacuum level at the surface lies below the bottom of the conduction band in the bulk of the material. Consequently, the threshold of response is set by the III-V bandgap. The bandgap (and the threshold of response) can be varied by alloying different III-V materials together. A reduction in thermionic emission is realized with these cathodes. At present no semitransparent III-V cathodes with comparably interesting performance are available. The problems hindering further improvements, as well as the problems of placing these cathodes in practical multipliers and image tubes, are discussed briefly.

Spicer, W. E.; Bell, R. L.

1972-01-01

27

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

28

Photodetectors using III-V nitrides  

DOEpatents

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

Moustakas, T.D.; Misra, M.

1997-10-14

29

Photodetectors using III-V nitrides  

DOEpatents

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

Moustakas, Theodore D. (Dover, MA); Misra, Mira (Arlington, MA)

1997-01-01

30

III-V arsenide-nitride semiconductor  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

31

Photodetectors using III-V nitrides  

DOEpatents

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

Moustakas, T.D.

1998-12-08

32

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

33

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.

Alivisatos, A. Paul (Berkeley, CA); Olshavsky, Michael A. (Brunswick, OH)

1996-01-01

34

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

35

III-V nitride materials and processes  

SciTech Connect

The First Symposium on III-V Nitride Materials and Processes was held in Los Angeles, California, May 6--8, 1996, and focused on recent experimental and theoretical developments and applications in the rapidly growing area of refractory III-V nitrides. The symposium was jointly sponsored by the Dielectric Science and Technology, Electronics and Luminescence and Display Materials Divisions of the Electrochemical Society. Subject areas included crystal growth (bulk and thin films), structure and microstructure, formation of defects, doping, optoelectronic properties and device structures. Particular attention was placed on the role of heteroepitaxy in the stabilization of the various allotropic phases (wurtzite, zincblende, sodium chloride) and the formation of native defects. Hydrogen passivation of Mg acceptors in GaN, as well as compensation, was addressed. The application of GaN, InN, AlN, ScN, etc. to optical devices (visible and UV emitters, full color displays, detectors) as well as high temperature electronics was covered in a number of presentations. Twenty two papers were processed separately for inclusion on the data base.

Moustakas, T.D. [ed.] [Boston Univ., MA (United States); Dismukes, J.P. [ed.] [Univ. of Toledo, OH (United States); Pearton, S.J. [ed.] [Univ. of Florida, Gainesville, FL (United States)

1996-12-31

36

Chemical Etching of Group III - V Semiconductors  

NASA Astrophysics Data System (ADS)

Chemical etching is basically a process used to selectively remove controlled amounts of material from the original substrate. The etch depth can be designed to be just tens of angstroms or up to a few hundred angstroms. The etching process is one of the important stages in the fabrication of micro electronics devices. Errors at this stage will severely impair performance of these devices. Due to the present diadvantages of dry etching, wet chemical etching will still be useful for some time. it is infact one of the standard technique for the processing of Integral Circuits (Ics). This article reviews the chemical etchants used for the reatment of GaAs and others III - V. Semiconductors, the factors involved in their mechanism and the many potential pitfalls, arwillan detects associated with them. The article should present an understandable account for the non-specialist reaser yet it does offer a useful material and information for the specialists readers an well.

Kadhim, Najah J.; Laurie, Stuart H.; Mukherjee, D.

1998-07-01

37

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

38

First principles study of III-V diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

As a good candidate for spintronic applications, diluted magnetic semiconductors (DMS) have been widely investigated in the past several years. First principles calculations are used to study the magnetic exchange interactions and Curie temperature (Tc) in III-V based diluted magnetic semiconductors and delta-doped layers. The local spin density approximation (LSDA) is combined with a linear-response technique to map the magnetic energy onto a Heisenberg hamiltonian, but no significant further approximations are made. The effect of disorder inherent in the DMS system on the ferromagnetism in these materials is studied. Large dispersion in the pairwise exchange interactions is shown. The dispersion strongly reduces Curie temperature of these materials. Clustering due to the annealing process further decreases Tc. With all the factors taken into account, Tc is reasonably predicted by the local spin-density approximation in manganese(Mn) doped gallium arsenide (GaAs) ((GaMn)As). Based on the result of (GaMn)As, two kinds of ternary alloy systems, manganese and chromium (Cr) co-doped GaAs ((Ga,Mn,Cr)As) and Mn and phosphorus (P) co-doped GaAs ((GaMn)(AsP)) are predicted to have higher Tc by double-exchange and Ruderman Kittel-Kasuya-Yosida (RKKY) models. LSDA calculations are used to test the prediction. The results show that neither co-doping Mn with Cr, nor alloying As with P improves Tc. Another approach to increase Tc is to develop delta-doped (GaMn)As, which is confirmed by LSDA calculations. By studying the exchange interactions of the high Mn concentration systems, this high Tc case is explained by considering the ferromagnetic (FM) and anti-ferromagnetic (AFM) contribution of bands with different symmetries and the crystallographic dependence of exchange interactions.

Xu, Jialei

39

Enhancing hole mobility in III-V semiconductors  

NASA Astrophysics Data System (ADS)

Transistors based on III-V semiconductor materials have been used for a variety of analog and high frequency applications driven by the high electron mobilities in III-V materials. On the other hand, the hole mobility in III-V materials has always lagged compared to group-IV semiconductors such as germanium. In this paper, we explore the use of strain and heterostructure design guided by bandstructure modeling to enhance the hole mobility in III-V materials. Parameters such as strain, valence band offset, effective masses, and splitting between the light and heavy hole bands that are important for optimizing hole transport are measured quantitatively using various experimental techniques. A peak Hall mobility for the holes of 960 cm2/Vs is demonstrated and the high hole mobility is maintained even at high sheet charge.

Nainani, Aneesh; Bennett, Brian R.; Brad Boos, J.; Ancona, Mario G.; Saraswat, Krishna C.

2012-05-01

40

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

41

Progress Towards III-V Photovoltaics on Flexible Substrates  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

42

Dipole scattering in polarization induced III-V nitride two-dimensional electron gases  

NASA Astrophysics Data System (ADS)

Unusually large spontaneous and piezoelectric fields in the III-V nitrides have led to the making of an entirely new class of two-dimensional electron gas. Fluctuation from a perfectly periodic binary structure in highly polar semiconductor alloys present the same physical situation as a random distribution of microscopic dipoles. The excess dipole distribution in the barrier layers is evaluated by a method similar to the virtual crystal approximation. It is shown that the mobility of electrons in the two-dimensional electron gas formed in highly polar heterostructures is intrinsically limited by scattering from such dipoles.

Jena, Debdeep; Gossard, Arthur C.; Mishra, Umesh K.

2000-10-01

43

First-principles study of III-V semiconductor nanowires  

NASA Astrophysics Data System (ADS)

Semiconductor nanowires play an important role in nanotechnology and present challenges in fundamental physics as well. Physical properties of semiconductor nanowires are expected to be essentially different from those of bulk crystals. They can be tuned by a wide range of parameters such as diameters, aspect ratios, orientations, and chemical compositions. Previously, we have studied single-cystal Si wires of different orientations using the density functional theory in the local density approximation (LDA). Due to the importance of III-V binary semicondutors, III-V semicondutor nanowires have legitimately attracted much interest recently. In this work, we studied from first-principles the III-V nanowires of GaAs and GaN, specially focusing on the size-dependent properties as a function of chemical species and compositions.

Zhao, Xinyuan; Chou, Mei-Yin

2004-03-01

44

III-V semiconductor solid solution single crystal growth  

NASA Technical Reports Server (NTRS)

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

Gertner, E. R.

1982-01-01

45

III-V\\/Silicon Lattice-Matched Tandem Solar Cells  

Microsoft Academic Search

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

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

2005-01-01

46

Preparation of Epitaxial Films of Iii-V Compounds.  

National Technical Information Service (NTIS)

An attempt is made to bring out a coherent and brief account of the techniques used for the preparation of epitaxial films of III-V compounds. Relative merits of the important techniques are discussed. Factors influencing the growth and quality of the fil...

S. K. Sharma V. K. Jain

1970-01-01

47

Approaches for III/V Photonics on Si  

SciTech Connect

We investigated different approaches to overcome difficulties in III/V-on-Si heteroepitaxy, namely growth on compliant substrates and virtual Ge substrates, both realized on top of Si substrates, and in addition, directly on Si. The prospect of this work was the realization of a light emitter on standard Si(100) substrate, capable of being integrated in established industrial processes.

Wiesner, M.; Schulz, W.-M.; Rossbach, R.; Jetter, M.; Michler, P. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, University of Stuttgart, Stuttgart, Germany and Stuttgart Research Center of Photonic Engineering (SCoPE) (Germany); Angelopoulos, E. A.; Burghartz, J. N. [Institut fuer Mikroelektronik Stuttgart (IMS CHIPS), Stuttgart (Germany); Werner, J.; Oehme, M.; Schulze, J. [Institut fuer Halbleitertechnik, University of Stuttgart, Germany and Stuttgart Research Center of Photonic Engineering (SCoPE) (Germany)

2011-12-23

48

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

49

Towards vertical III-V nanowire devices on silicon  

Microsoft Academic Search

In this paper, we have grown III-V nanowires by metal organic vapor phase epitaxy (MOVPE) using the vapor-liquid-solid (VLS) growth mechanism. In addition, the author discusses the fabrication and characterization of reproducible axial InP nanowire LED devices.

EPAM Bakkers; M. T. Borgstrom; W. van den Einden; Weert van MHM; E. D. Minot; F. Kelkensberg; Kouwen van MP; J. A. van Dam; L. P. Kouwenhoven; V. Zwiller; A. Helman; O. Wunnicke; M. A. Verheijen

2007-01-01

50

The integration of III-V optoelectronics with silicon circuitry  

Microsoft Academic Search

The integration of III-V optoelectronics with silicon circuitry provides the potential for fabricating dense parallel optical interconnects with data links capable of Terabit aggregate data rates. This paper reviews many of the current approaches used for the fabrication of integrated optoelectronic devices and then highlights the performance results. Finally, the applied method is reviewed in greater detail with recent results

David L. Mathine

1997-01-01

51

Projected performance of III-V epitaxial multijunction solar cells in space  

NASA Technical Reports Server (NTRS)

The monolithic epitaxial multijunction stack, to be fabricated from III-V quaternary alloys, has been analyzed for use in space with a detailed computer model. AlGaInAs and AlGaAsSb three-junction cells, each having an AlAsSb window, were modeled as functions of temperature, concentration, minority carrier diffusion length, etc., as were AlGaAs/GaAs and AlGaAsSb/InP two-junction cells. Cell efficiencies for one expected operating point in space (50 suns, 125 C) were around 20% for the two-junction cells and around 23-24% for the three-junction cells, using projected minority carrier diffusion lengths of 1.5 microns. Longer diffusion lengths in the III-V alloys (approaching those of GaAs) would allow the three-junction cells to reach 30% efficiency, if such conditions as 100 suns, 50 C can be achieved. The major technological challenges facing the high-efficiency multijunction cell are summarized and discussed in light of the modeling results.

Maloney, T. J.

1981-01-01

52

Assessment of a low-cost gold-free metallization for III–V high concentrator solar cells  

Microsoft Academic Search

A gold-free metallization is proposed to be used as the grid contact in III–V concentrator solar cells. This metallization is based on the Cu\\/Ge system which has been reported to attain very low specific contact resistances on n-GaAs. In this letter, we show that metal layers with low resistivity (13??cm) can be obtained if the copper content in the alloy

Ignacio Rey-Stolle; Beatriz Galiana; Carlos Algora

2007-01-01

53

Investigation of new semiinsulating behavior of III-V compounds  

NASA Technical Reports Server (NTRS)

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

1990-01-01

54

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

55

III-V Growth on Silicon Toward a Multijunction Cell  

Microsoft Academic Search

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

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

2005-01-01

56

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

NASA Astrophysics Data System (ADS)

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

Ridley, B. K.

2009-04-01

57

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

58

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

59

Integrated Optical Pumping of Cr & Ti-Doped Sapphire Substrates With III-V Nitride Materials.  

National Technical Information Service (NTIS)

The goal of this proposal was to investigate the potential advantages of integrating III-V nitride structures on doped sapphire substrates and doped sapphire waveguide structures. III-V Nitride structures are typically grown on undoped synthetic sapphire ...

J. Muth

2005-01-01

60

III-V semiconductors on silicon-germanium substrates for multi-junction photovoltaics  

NASA Astrophysics Data System (ADS)

The epitaxial integration of high quality III-V semiconductors with Si is of fundamental interest for photovoltaic devices since Si substrates offer a lighter, stronger, and cost effective platform for device production. However, the lattice-mismatch between conventional III-V photovoltaic materials and Si generates threading dislocations in the epitaxial device layers, which can limit solar cell performance, depending of the density of such defects, the particular III-V material, and the device design. By using compositionally step-graded SiGe interlayers up to 100% Ge, which is lattice-matched to GaAs, the ˜4% lattice-mismatch between Si and GaAs and In0.49 Ga0.51P is accommodated in the Group IV alloy system; this has produced defect densities less than 1 x 106 cm -2 in fully relaxed the Ge/SiGe/Si (SiGe) virtual substrates. This unique approach to III-V/Si integration is employed in this dissertation for the development of GaAs and In0.49Ga0.51P single junction (SJ) solar cells and ultimately In0.49Ga0.51P/GaAs dual junction (DJ) solar cells, integrated on a Si platform. The residual threading dislocation density (TDD) present in the SiGe substrates transfers to the epitaxially grown III-V layers and thus can influence III-V solar cell performance. In this dissertation we report, for the first time, on the impact of TDD on the minority carrier electron lifetime in GaAs grown on SiGe. The electron lifetime in metamorphic p-type GaAs was found to be lower than that of holes in n-type GaAs at a given TDD. This resulted from the higher mobility of electrons compared to holes and thus enhanced interactions with the TD array. Incorporating a TDD dependent lifetime into metamorphic GaAs solar cell device models, higher reverse saturation current densities and lower open-circuit voltages for n+/p compared to p+/n were predicted. This result was experimentally confirmed in this dissertation by diode and solar cell device measurements of both n +/p and p+/n GaAs cells grown on GaAs and SiGe substrates. The higher performance of the p+/n GaAs-on-SiGe solar cell, by virtue of its higher opencircuit voltage, offers great potential for both space and terrestrial photovoltaic applications. The extension of this technology to space applications has lead to the development of large area GaAs-on-SiGe solar cells (up to 4 cm2) with no degradation in cell performance. These large area cells will be flown on the International Space Station to test their actual space performance, which indicates their technological importance. Meanwhile, record terrestrial performance was measured and suggests efficiencies higher than 20% are realizable with current SiGe substrate technologies. (Abstract shortened by UMI.)

Andre, Carrie L.

61

Hot-electron drift velocity in III V semiconductors under the condition of impact ionization  

NASA Astrophysics Data System (ADS)

A calculation has been carried out for the drift velocity of electrons in the highfield region under the condition of impact ionization in III V semiconductor compounds. The energy-balance equation of the one-electron model has been solved considering alloy scattering and carrier-carrier interaction, in addition to optical phonon and ionization scattering. Fairly good agreement is obtained for GaAs with the available experimental and Monte-Carlo results. Graphs for the high-field drift velocity has also been plotted for Ga1- x InxAs ( x = 0.53) at different ratios of ionization mean-free path and optical phonon mean-free path. The plot of high-field drift velocity versus ionization rate reveals that the high-field drift velocity strongly depends on the ionization rate of carriers, and vice versa.

Singh, S. R.; Pal, B. B.

1987-05-01

62

Effective electron mass in quantum wires of III-V, ternary and quaternary materials.  

PubMed

In this paper, an attempt is made to study the effective electron mass (EEM) in Quantum wires (QWs) of III-V, ternary and quaternary materials on the basis of three and two band models of Kane within the framework of k x p formalism. It has been found, taking QWs of InAs, InSb, GaAs, Hg(1-x)Cd(x)Te and In(1-x)Ga(x)As(1-y)P(t) that the 1D EEM increases with electron concentration per unit length and decreases with increasing film thickness respectively. For ternary and quaternary materials the EEM increases with increase in alloy composition. Under certain special conditions all the results for all the 1-D materials get simplified into the well known parabolic energy bands and thus confirming the compatibility test. The results of this paper find two applications in the fields of nanoscience and technology. PMID:23447948

Paitya, N; Ghatak, K P

2012-12-01

63

Recent Soviet microelectronics research on III-V compounds semiconductors  

NASA Astrophysics Data System (ADS)

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

Sello, H.; Kirkpatrick, C. G.

1988-08-01

64

Recombination imaging of III-V solar cells  

NASA Technical Reports Server (NTRS)

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

Virshup, G. F.

1987-01-01

65

Carbon doping of III-V compound semiconductors  

SciTech Connect

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

Moll, A.J.

1994-09-01

66

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 InAs 0.25P 0.75 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

67

III-V nanowire arrays: growth and light interaction.  

PubMed

Semiconductor nanowire arrays are reproducible and rational platforms for the realization of high performing designs of light emitting diodes and photovoltaic devices. In this paper we present an overview of the growth challenges of III-V nanowire arrays obtained by molecular beam epitaxy and the design of III-V nanowire arrays on silicon for solar cells. While InAs tends to grow in a relatively straightforward manner on patterned (111)Si substrates, GaAs nanowires remain more challenging; success depends on the cleaning steps, annealing procedure, pattern design and mask thickness. Nanowire arrays might also be used for next generation solar cells. We discuss the photonic effects derived from the vertical configuration of nanowires standing on a substrate and how these are beneficial for photovoltaics. Finally, due to the special interaction of light with standing nanowires we also show that the Raman scattering properties of standing nanowires are modified. This result is important for fundamental studies on the structural and functional properties of nanowires. PMID:24334728

Heiss, M; Russo-Averchi, E; Dalmau-Mallorquí, A; Tütüncüo?lu, G; Matteini, F; Rüffer, D; Conesa-Boj, S; Demichel, O; Alarcon-Lladó, E; Fontcuberta i Morral, A

2014-01-10

68

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

69

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

NASA Astrophysics Data System (ADS)

The electronic band structures and excited states of III-V semiconductors such as GaP, AlP, AlAs, and AlSb for various polytypes are determined employing the screened-exchange density functional calculations implemented in the full-potential linearized augmented plane-wave methods. We demonstrate that GaP and AlSb in the wurtzite (WZ) structure have direct gap while III-V semiconductors in the zinc blende, 4H, and 6H structures considered in this study exhibit an indirect gap. Furthermore, we find that inclusion of Al atoms less than 17% and 83% in the hexagonal AlxGa1-xP and AlxGa1-xAs alloys, respectively, leads to a direct transition with a gap energy of ˜2.3 eV. The feasibility of III-V semiconductors with a direct gap in WZ structure offers a possible crystal structure engineering to tune the optical properties of semiconductor materials.

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

2014-03-01

70

Binary III-V semiconductor core optical fiber.  

PubMed

For the first time to the best of our knowledge a glass-clad optical fiber comprising a crystalline binary III-V semiconductor core has been fabricated. More specifically, a phosphate glass-clad fiber containing an indium antimonide (InSb) core was drawn using a molten core approach. The core was found to be highly crystalline with some oxygen and phosphorus diffusing in from the cladding glass. While optical transmission measurements were unable to be made, most likely due to free carrier absorption associated with the conductivity of the core, this work constitutes a proof-of-concept that optical fibers comprising semiconductor cores of higher crystallographic complexity than previously realized can be drawn using conventional fiber fabrication techniques. Such binary semiconductors may open the door to future fiber-based nonlinear devices. PMID:20389508

Ballato, John; Hawkins, Thomas; Foy, Paul; McMillen, Colin; Burka, Laura; Reppert, Jason; Podila, Ramakrishna; Rao, A M; Rice, Robert R

2010-03-01

71

III-V Nanowire Array Growth by Selective Area Epitaxy  

SciTech Connect

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 AsH{sub 3} decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

Chu, Hyung-Joon; Stewart, Lawrence [Ming Hsieh Department of Electrical Engineering, University of Southern California (United States); Yeh, Tingwei [Mork Family Department of Chemical Engineering and Material Science, University of Southern California 3651 Watt Way, VHE-314, Los Angeles, CA90089 (United States); Dapkus, P. Daniel [Ming Hsieh Department of Electrical Engineering, University of Southern California (United States); Mork Family Department of Chemical Engineering and Material Science, University of Southern California 3651 Watt Way, VHE-314, Los Angeles, CA90089 (United States)

2011-12-23

72

III-V/II-VI heterovalent double quantum wells  

NASA Astrophysics Data System (ADS)

We report on design, fabrication by molecular beam epitaxy, and photoluminescence (PL) studies of III-V/II-VI heterovalent structures containing a GaAs/AlGaAs/ZnSe/ZnCdMnSe double quantum well (QW). The studies of temperature-dependent and time-resolved PL have provided an insight into the nature of the exciton localization potential induced by the heterovalent interface. It is found that under the resonant conditions the observed emission mostly originates from the recombination of excitons confined in type II quantum-dot-like structures, where the holes are localised within the GaAs QW due to the well width fluctuations and the electrons are localized in the plane of the ZnCdMnSe QW due to the fluctuations of the conduction band offset at the heterovalent interface, induced by random variation of the interface microscopic structure.

Toropov, A. A.; Sedova, I. V.; Sorokin, S. V.; Terent'ev, Ya. V.; Ivchenko, E. L.; Lykov, D. N.; Ivanov, S. V.; Bergman, J. P.; Monemar, B.

73

III-V nanowires grown in a simple, homebuilt system.  

NASA Astrophysics Data System (ADS)

Semiconductor nanowires are promising experimental platforms for studying quantum transport due to their built-in one-dimensional confinement of charge carriers. To enable the study of III-V semiconducting nanowires, we built a simple tube furnace based MOCVD reactor. Growth of InP and InAs nanowires using trimethylindium, di-tert-butylphosphine and triethylarsenic has been studied as a function of temperature, pressure, precursor concentration and growth substrate. At optimal growth conditions, wires of 20-100 nm in diameter and up to 10 ?m in length are achievable on InAs substrates. Characterization was performed using SEM, EDS and TEM; both wurtzite and zincblende structures have been observed. We will also present transport measurements of nanowires grown using this system. 8pt

Schroer, M. D.; Petta, J. R.

2009-03-01

74

Characteristics of III-V Semiconductor Devices at High Temperature  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

75

III-V MOSFETs: From Materials & Physics to Devices  

NASA Astrophysics Data System (ADS)

Gallium-Arsenide metal-oxide-semiconductor field-effect-transistors (MOSFET) have finally been demonstrated with performance metrics matching the predictions of semiconductor device models. Recent discoveries and inventions in many areas including materials and fabrication, semiconductor physics, interface chemistry, semiconductor interface analysis, and semiconductor device design and process have contributed to this success. In my invited talk, I will review some select areas including the unique properties of interfaces formed between Ga2O molecules and a GaAs surface, a high permittivity (? 20) GdGaO/Ga2O3 dielectric stack providing both a device quality interface and band-offsets on GaAs required for MOSFET operation, a semiconductor heterostructure for mitigation of high band-edge interface-state density, and device design criteria for high electron channel mobility and MOSFET drive current. Performance metrics of present metal-gate GaAs enhancement-mode MOSFETs such as electron channel mobility, drive current, transconductance, and threshold voltage will be discussed. GaAs MOSFETs with In0.3Ga0.7As channel layers exhibit typical electron peak mobilities exceeding 5,000 cm^2/Vs, an improvement of a factor of 20 over silicon based high-? metal-gate inversion-mode MOSFETs. Even higher electron mobilities surpassing 12,000 cm^2/Vs have been measured in In0.75Ga0.25As channel layers. Beside the use of channel materials such as InxGa1-xAs with high bulk electron mobility, the physics of device operation is distinctively different from silicon inversion-mode MOSFETs. III-V MOSFET are now considered an option for CMOS based circuitry beyond the 22 nm node of the International Technology Roadmap for Semiconductors. High channel mobilities and the first successful implantation of III-V MOSFETs seem to justify such contemplation, however, many obstacles remain.

Passlack, Matthias

2008-03-01

76

Progress in the melt growth of III V compounds  

NASA Astrophysics Data System (ADS)

Semiconductor behaviour was predicted and discovered in the III-V semiconductor compounds almost 50 years ago at the beginning of the 50s. The demand for high-purity single crystals was axiomatic in view of the prior pioneering research on germanium as a semiconductor device material. However, while the development of semiconductor grade Ge took about a decade, the comparable development of the readily dissociable III-V compounds have followed a very much slower evolution, which is still in progress. This review discusses some of their intrinsic material problems and some of the solutions that have required so much research and development effort to produce single crystal compounds suitable for high-performance devices. The primary focus of the paper is the compounds of major commercial importance, GaAs and InP. While most of the problems that arise in the growth of high-quality single crystals of these materials have been endured over the years, new and more refined technical and scientific solutions to these have been developed. The growth techniques that will be considered include Liquid Encapsulation, Vertical Gradient Freeze, Vapour Pressure Controlled Czochralski and Hot Wall Pulling techniques including Pressure Balancing. The practical constraints to implementing these techniques and their advantages and limitations are considered. Problems of twinning, cellular structure, dislocation formation, lineage, constitutional supercooling and defects are reviewed. The significance of technique in relation to recent developments in commercial exploitation, especially with regard to size, is noted. In addition, related areas of scientific interest which have either not been researched significantly or could be of future significance such as the potential of electromagnetic stirring are highlighted.

Mullin, J. B.

2004-03-01

77

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

78

III-V Compound Detectors for CO2 DIAL Measurements  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

79

Demonstration of heterogeneous III-V/Si integration with a compact optical vertical interconnect access.  

PubMed

Heterogeneous III-V/Si integration with a compact optical vertical interconnect access is fabricated and the light coupling efficiency between the III-V/Si waveguide and the silicon nanophotonic waveguide is characterized. The III-V semiconductor material is directly bonded to the silicon-on-insulator (SOI) substrate and etched to form the III-V/Si waveguide for a higher light confinement in the active region. The compact optical vertical interconnect access is formed through tapering a III-V and an SOI layer in the same direction. The measured III-V/Si waveguide has a light coupling efficiency above ~90% to the silicon photonic layer with the tapering structure. This heterogeneous and light coupling structure can provide an efficient platform for photonic systems on chip, including passive and active devices. PMID:24322256

Ng, Doris Keh Ting; Wang, Qian; Pu, Jing; Lim, Kim Peng; Wei, Yongqiang; Wang, Yadong; Lai, Yicheng; Ho, Seng Tiong

2013-12-15

80

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

81

Fullerene Molecules and Other Clusters of III-V Compounds  

NASA Astrophysics Data System (ADS)

The goal of the our work is to derive geometries of fullerene-like cages and other clusters of atoms from groups III and V of the periodic table. Our previous research focused on Carbon Fullerenes and on GanAsn clusters (n = 1 thru 12). Our research group has made an original discovery about GanAsn clusters. In our work on nanotechnology to date, we used the hybrid ab initio methods of quantum chemistry to derive the different geometries for the clusters of interest. We also calculated binding energies, bond-lengths, ionization potentials, electron affinities and HOMO-LUMO gaps, and IR spectra for these geometries. Of particular significance was the magic number for GaAs cluster stability that we found at n = 8. This is important because materials containing controlled III-V nanostructures provide the capability of preparing new classes of materials with enhanced optical, magnetic, chemical sensor and photo-catalytic properties. The second phase of the investigation will examine the effects of confinement on the optical properties the clusters. It will be interesting to observe novel linear as well as nonlinear optical processes in them. The third phase of the investigation will focus on the improved design of solar cells based on the optical properties of the clusters.

Hira, Ajit; Auxier, John, II; Lucero, Melinda

2010-03-01

82

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

83

Hot-hole lasers in III--V semiconductors  

SciTech Connect

Following the success of p-Ge hot-hole lasers, there is potential for using other semiconductor materials, notably III--V materials such as GaAs and InSb. Previous analysis had suggested that a large effective mass ratio between the heavy and light holes is advantageous, which implies that InSb would make an excellent hot-hole laser. Using our Monte Carlo simulation of both GaAs and InSb hot-hole lasers in combination with a rate equation model, we see that previously accepted criteria used to predict performance are not always reliable, and we suggest suitable alternatives. The simulation results include gain and gain bandwidth as a function of field strength and laser frequency, and alternative field orientations and photon polarizations are considered. Comparisons are made with bulk 1-Ge systems. The optimum conditions predicted by our simulation could then be used in the design of quantum-well hot-hole lasers. {copyright} 2001 American Institute of Physics.

Kinsler, P.; Wenckebach, W. Th.

2001-08-15

84

Backgating effect in III-V MESFET's: A physical model  

NASA Astrophysics Data System (ADS)

The backgating (sidegating) effect in III-V MESFET's devices is analyzed through the modelisation of a Metal (Schottky barrier)-N (channel)-SI (Semi Insulating)-N+ (back-gate contact) structure. Numerical and analytical results, using the drift-diffusion charge transport model, show that along the applied voltage range associated with backgating: (i) quasi space charge neutrality across most of the bulk SI layer and (ii) quasi Boltzmann equilibrium for the free electron across the reverse biased N (channel)-SI contact prevail for GaAs (SI) or InP (SI). The circumstances under which a negative bias applied on the back-gate (N+) contact will either develop across the reverse biased N-SI contact (strong backgating) or across the SI layer (negligible backgating) are described by means of a simple analytical relation as a function of the deep level parameters values. The electric field dependence of the carrier mobility (Gunn effect) produces a backgating effect with a threshold voltage. The presence of a low lifetime, buffer layer, at the N-SI interface is shown to strongly reduce it.

Manifacier, J. C.; Ardebili, R.

2014-01-01

85

Atomic hydrogen cleaning of polar III V semiconductor surfaces  

NASA Astrophysics Data System (ADS)

Atomic hydrogen (H*) generated by a simple thermal cracker source has been used to efficiently clean the polar surfaces of several III-V semiconductors at temperatures significantly lower than those normally required for oxide desorption. The process of atomic hydrogen cleaning (AHC) is demonstrated for the preparation of the (001) and (111)A surfaces of InAs, and the InSb(001) and GaSb(001) surfaces. Both the substrate anneal temperature and the required H* dose vary for the different materials, but in all cases clean, well-ordered surfaces can be produced, as determined by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). It is found that both the InAs and GaSb surfaces can be cleaned with H* exposures at a specific temperature (as low as 470 K for GaSb and 700 K for InAs); however, for InSb it is also necessary to supply an Sb 4 flux from a Knudsen cell to avoid decomposition of the surface. High resolution electron energy loss spectroscopy (HREELS) has been used to monitor the surface plasmon excitations in these doped materials to measure the carrier concentration in the near-surface region. It is found that no measurable passivation of donors or acceptors occurs in either the n-type or p-type materials studied. In addition, and in contrast to ion sputtering procedures, no defect induced increase in the carrier concentration occurs as a result of atomic hydrogen cleaning.

Bell, G. R.; Kaijaks, N. S.; Dixon, R. J.; McConville, C. F.

1998-04-01

86

Epitaxial III-V films and surfaces for photoelectrocatalysis.  

PubMed

Efficient photoelectrochemical devices for water splitting benefit from the highest material quality and dedicated surface preparation achieved by epitaxial growth. InP(100)-based half-cells show significant solar-to-hydrogen efficiencies, but require a bias due to insufficient voltage. Tandem absorber structures may provide both adequate potential and efficient utilization of the solar spectrum. We propose epitaxial dilute nitride GaPNAs photocathodes on Si(100) substrates to combine close-to-optimum limiting efficiency, lattice-matched growth, and established surface preparation. Prior to a discussion of the challenging III-V/Si(100) heterojunction, we describe the closely related epitaxial preparation of InP(100) surfaces and its beneficial impact on photoelectrochemical water-splitting performance. Analogies and specific differences to GaP(100) surfaces are discussed based on in situ reflectance anisotropy and on two-photon photoemission results. Preliminary experiments regarding GaP/Si(100) photoelectrochemistry and dilute nitride GaPN heteroepitaxy on Si(100) confirm the potential of the GaPNAs/Si tandem absorber structure for future water-splitting devices. PMID:22890851

Döscher, Henning; Supplie, Oliver; May, Matthias M; Sippel, Philipp; Heine, Christian; Muñoz, Andrés G; Eichberger, Rainer; Lewerenz, Hans-Joachim; Hannappel, Thomas

2012-08-27

87

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

88

Unified mechanism for Schottky-barrier formation and III-V oxide interface states  

Microsoft Academic Search

Extensive experimental evidence indicates that the Schottky-barrier formation on III-V semiconductors is due to defects formed near the interface by deposition of the metal (or of oxygen). Detailed level positions are established and assigned to either missing column III or V atoms. This model also applies to formation of states at III-V oxide interface states.

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

1980-01-01

89

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

90

III-V semiconductor photodetectors for infrared applications  

NASA Astrophysics Data System (ADS)

This thesis demonstrated the III-V semiconductor infrared photodetectors grown by solid source molecular beam epitaxy utilizing novel materials, device structures and substrate orientations. The photodetectors investigated in this thesis have spectral response ranging from 1.3mum to 12mum. Three photodetector structures were investigated: heterojunction photodiodes, heterojunction phototransistors, and superlattice photodiodes. Chapter 2 and 3 discuss two infrared heterojunction photodiodes at room temperature. Chapter 2 studies an InGaAsSb photodiode with a high detectivity and a 50% cutoff wavelength at 2.6mum. Chapter 3 describes a non-cryogenic InAsSb photodiode with a 50% cutoff wavelength at 4.3mum. Chapter 4 and 5 present two infrared heterojunction phototransistors (HPTs). A p-n-p InGaAsSb HPT is investigated in Chapter 4 by taking the advantageous band offsets between AlGaAsSb and InGaAsSb. The HPT exhibits a high optical gain and a 50% cutoff wavelength of 2.5mum at room temperature. In Chapter 5, the first InAs HPT structure is proposed and room temperature operation is demonstrated with an optical gain of 8.4 and a 50% cutoff wavelength of 3.5mum. In Chapter 6, the first type-II InAs/GaSb superlattice photodiodes grown on (311)B GaSb substrate is presented and compared with the corresponding photodiodes grown on (100) GaSb substrate. At 80K, the (311)B devices exhibit longer cutoff wavelength and detectivity twice as high as their (100) counterparts. At last, a mid-IR type-II superlattice photodiode was demonstrated at 80K with cutoff wavelength at 6.6mum. The device exhibits a near BLIP detectivity at 80K and higher temperature operation up to 280K.

Shao, Hui

91

Swift-heavy-ion-induced damage formation in III-V binary and ternary semiconductors  

SciTech Connect

Damage formation in InP, GaP, InAs, GaAs, and the related ternary alloys Ga{sub 0.50}In{sub 0.50}P and Ga{sub 0.47}In{sub 0.53}As irradiated at room temperature with 185 MeV Au ions was studied using Rutherford backscattering spectroscopy in channeling configuration, transmission electron microscopy, and small-angle x-ray scattering. Despite nearly identical ion-energy loss in these materials, their behavior under swift-heavy-ion irradiation is strikingly different: InP and Ga{sub 0.50}In{sub 0.50}P are readily amorphized, GaP and GaAs remain almost undamaged and InAs and Ga{sub 0.47}In{sub 0.53}As exhibit intermediate behavior. A material-dependent combination of irradiation-induced damage formation and annealing is proposed to describe the different responses of the III-V materials to electronic energy loss.

Schnohr, C. S.; Kluth, P.; Giulian, R.; Llewellyn, D. J.; Byrne, A. P.; Cookson, D. J.; Ridgway, M. C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Australian Synchrotron, Clayton, Victoria 3168 (Australia); Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2010-02-15

92

Far Infrared Studies of Iii-V Semiconductor Structures.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. This thesis reports the behaviour of impurities in III-V semiconductors using the sensitive technique of far infrared photoconduction (FIRPC) at low temperatures and at magnetic fields up to 10 T. The thesis reports the effects of inadvertent and intentional impurities in both bulk epitaxial and low dimensional structure systems grown by molecular beam epitaxy (MBE). High mobility bulk n-GaAs has been investigated and the present measurements shows a variety of optical transitions involving the shallow donor impurities. The first observation of the D^- transitions in MBE n-GaAs is reported as well as central-cell splitting of the impurity shifted cyclotron resonance (ISCR). Inadvertent contaminants are identified by measurements of central -cell splittings and a clear observation of the "bottle -neck" effect is reported. A distinct splitting of the cyclotron resonance is seen and is taken as evidence of transitions between spin-split higher Landau levels. Measurements on high mobility GaAs/AlGaAs heterojunctions have shown a cyclotron resonance splitting observed only in photoconduction. This has been explained using a coupled oscillator model of impurities that have migrated to the interface during growth. GaAs/AlGaAs multi-quantum wells (MQW) have been grown with intentional silicon doping in the well centres. Zeeman spectroscopy of the 1s to 2p _{+1} transition has been performed up to 10 T and show linewidths much narrower than for other reported samples. Transitions involving higher states of the confined impurity are clearly seen in these samples. Time-resolved far infrared photoconduction measurements have been carried out on bulk n-InP, GaAs/AlGaAs heterojunctions, and multiquantum wells. These measurements have enabled the investigation of electron recombination dynamics after the termination of the laser pulse. The time response of suitably doped MQW samples indicates potential as fast, sensitive, detectors of long wavelength (100 mu m) radiation.

Grimes, Richard Thomas

1990-08-01

93

BAs-GaAs Semiconductor Alloys as a Photovoltaic Alternative to Nitride Alloys  

SciTech Connect

Nitrogen alloyed III-V semiconductor compounds have been intensely studied in recent years due to unusual effects caused by nitrogen alloying. These effects are exploited in band gap engineering for specific applications such as solar cells and blue lasers.

Hart, G. L. W.; Zunger, A.

2000-01-01

94

Characterization of III-V materials by optical interferometry  

NASA Astrophysics Data System (ADS)

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

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

1993-09-01

95

Atomic layer etching of III–V compound materials using a low angle forward reflected Ne neutral beam  

Microsoft Academic Search

Atomic layer etching characteristics of III-V compound materials have been investigated using a Ne neutral beam and Cl2 gas. At the monolayer etching condition, the roughness of the III-V compound materials surface was remaining similar to that of the un-etched III-V compound materials surface. In addition, the III-V compound materials etched by the atomic layer etching showed the surface composition

W. S. Lim; G. Y. Yeom; S. D. Park; Y. Y. Kim; B. J. Park

2009-01-01

96

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

97

Scanning transmission electron microscopy study of III-V nitrides  

NASA Astrophysics Data System (ADS)

A study of the electronic properties of the III-V nitrides and the characterization of nitride-based heterostructures, interfaces and quantum wells using scanning transmission electron microscopy (STEM) are presented. Examination of the epitaxially grown GaN/Al0.25Ga0.75N heterostructure shows that, in contrast to expectations, the interface between GaN buffer and Al0.25Ga0.75N barrier is not atomically sharp, but diffuse. High spatial resolution electron energy loss spectroscopy measurements and annular dark field imaging indicate that these interfaces can be up to 20 A wide. The effects of the presence of the diffuse interface between the GaN and AlxGa1- xN layers on formation of the quasi-two-dimensional electron gas at the heterointerface are studied. Electronic energy levels and the distribution of these highly localized electrons at the interface are calculated for different interface widths and for various physical parameters of the structure. The long-range and atomic level uniformities of the GaN quantum wells grown in an AlN matrix are characterized using electron energy loss spectroscopy and annular dark field imaging. The effects of the incident electron beam broadening inside the specimen on STEM measurements are discussed and mechanisms to minimize them are suggested. For quantitative correlation, the measured intensity of the nitrogen K-edge is compared with the propagating beam intensity obtained from multislice calculations. Possible effects of strain in the structure on its electronic states and energy-loss spectra are predicted. The electron-beam-induced damage of the wurtzite InN in STEM is studied and knock-on type damage with ejection of nitrogen atoms from a sample is observed. From comparison of the measured integrated intensity of the nitrogen K-edge and indium M4,5-edge with a calculated mass-loss model the vacancy-enhanced displacement energy for nitrogen atoms in InN is obtained. Investigations of the electronic structure of the wurtzite InN are carried out and excellent agreement between measured spectra of the nitrogen K-edge and the indium M4,5 -edge and corresponding nitrogen 2p and the indium 5p partial density of states (DOS) of the conduction band is obtained. The calculations of DOS are performed using density functional theory (DFT). DFT calculations of nitrogen 2p partial DOS of the conduction band in strained and relaxed wurtzite InN combined with multiple scattering x-ray absorption near edge structure calculations of the corresponding nitrogen K-edge spectra suggest that a strong modification of the electronic structure should be expected in epitaxially grown multilayer structures when a significant mismatch in lattice constants between layers is present.

Mkhoyan, Karen Andre

98

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

SciTech Connect

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

Anderson, T.J.

1998-07-21

99

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

National Technical Information Service (NTIS)

The High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrators project seeks to provide new photovoltaic cells for Concentrator Photovoltaics (CPV) Systems with higher cell efficiency, more favorable temperature coefficients and less sensi...

S. Hubbard

2012-01-01

100

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

NASA Technical Reports Server (NTRS)

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 incorporated into a transport theory for devices constructed from these materials, and experiments conducted to test the theory. The vacancies and other defects in the III-V compounds are detected by measurement of the nuclear magnetic resonance (NMR) line width. Most of the III-V compounds have at least one isotope with a nuclear quadrupole moment. In a crystal with a cubic crystal field (characteristic of most III-V compounds) there is no quadrupole splitting of the Zeeman resonance line. However, a defect removes the cubic symmetry locally and causes splitting which result in a change of the NMR width. This change can be used to detect the presence of vacancies.

Soest, J. F.

1973-01-01

101

Etching Chemistry of III-V Semiconductors and the Development of Surface Roughness.  

National Technical Information Service (NTIS)

This research addressed the need for basic information concerning halogen etching of III-V semiconductors. The reactions of halogens with semiconductor surfaces are the fundamental chemical interactions in processes employed for device manufacture. In thi...

J. A. Yarmoff

2000-01-01

102

Etching Chemistry of III-V Semiconductors and the Development of Surface Roughness.  

National Technical Information Service (NTIS)

This research addresses the need for fundamental information concerning halogen etching of III-V semiconductors. The reactions of halogens with semiconductor surfaces are the fundamental chemical interactions in processes employed for device manufacture. ...

J. A. Yarmoff

1998-01-01

103

Electrolitic Deposited Ohmic Contacts on III-V Compound Semiconductors: A Review.  

National Technical Information Service (NTIS)

The electroplating technology for ohmic contacts to group III-V compound semiconductors is reviewed. The reviewed technology is divided into four parts: the semiconductor surface preparation before electroplating; the choice of the metals or the metal all...

S. Blasko M. J. Geerts J. C. van den Heuvel

1988-01-01

104

Fermi level stabilization in semiconductors: Implications for implant activation efficiency. [III-V semiconductors  

SciTech Connect

We propose the existence of a Fermi level stabilization energy in III-V semiconductors which provides a reference level for the electronic part of defect annihilation energies. It is shown that the position of the stabilization energy with respect to the band edges determines the maximum free carrier concentration which can be obtained through doping. The proposed model accounts for previously unexplained trends in implant activation efficiency in III-V semiconductors. 16 refs., 3 figs.

Walukiewicz, W.

1987-11-01

105

Integration of III-V materials with silicon for optoelectronic integrated circuit applications  

NASA Astrophysics Data System (ADS)

Integration of III-V materials with Si substrates has been studied extensively in recent years since it has a wide range of applications on optoelectronic integrated circuits (OEIC). It enables the combinations of III-V based optoelectronic devices with Si-based microelectronic devices and circuits. The conventional approach for III-V integration with Si is based on wafer bonding and etch-back. Although it provides III-V materials transferred on Si with relatively high crystalline quality, the etch-back process in this approach etches off the initial III-V growth substrate thus it gives low yield and increases the cost. Recently, another III-V layer transfer approach using the ion-cut (smart-cutRTM) process has been demonstrated, based on hydrogen ion implantation and wafer bonding. This approach has the advantage of saving the initial III-V substrate for reuse, but the transferred structure usually suffers from the hydrogen implantation induced damage. This dissertation demonstrates a new approach that combines ion-cut and selective chemical etch for InP-based III-V layer transfer. This layer transfer scheme takes advantage of conventional ion-cutting process by conserving III-V substrates for reuse, and simultaneously improving the transferred layer quality and surface condition without using chemical and mechanical polishing. The effects of hydrogen ion implantation conditions (temperature, dose rate, and energy) on III-V ion-cut process have been investigated and the physical mechanism behind these effects was examined. Based on these findings, the hydrogen implantation conditions were optimized in our study that led to successful III-V layer transfers. Based on our layer transfer scheme, two approaches have been explored for integrating an III-V based device on Si. One way is to transfer an InP layer onto Si and use this transferred structure as a growth template. Instead of growing complicated III-V device structures which are out of the growth capacity in our laboratory, we focused on the fundamental issues with the transferred structure that must be solved for the growth template purpose. Particularly there is a bubble issue that always shows up when the transferred structures are heated up in the growth chamber. We studied the origin of these bubbles and implemented a simple and effective approach that can constantly solve the bubble problem. Another way is to grow an III-V device on III-V substrate and transfer the whole device structure onto Si. InP/InGaAs/InP p-i-n photodiodes were transferred onto Si substrate and the effects of the hydrogen implantation on the device performance have been discussed.

Chen, Peng

106

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

NASA Astrophysics Data System (ADS)

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

Huang, Jingyi

107

Development of III-V p-MOSFETs with high-kappa gate stack for future CMOS applications  

NASA Astrophysics Data System (ADS)

As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, non-silicon materials and new device architectures are gradually being introduced to improve Si integrated circuit performance and continue transistor scaling. Recently, the replacement of SiO2 with a high-k material (HfO2) as gate dielectric has essentially removed one of the biggest advantages of Si as channel material. As a result, alternate high mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. III-V materials in particular have become of great interest as channel materials, owing to their superior electron transport properties. However, there are several critical challenges that need to be addressed before III-V based CMOS can replace Si CMOS technology. Some of these challenges include development of a high quality, thermally stable gate dielectric/III-V interface, and improvement in III-V p-channel hole mobility to complement the n-channel mobility, low source/drain resistance and integration onto Si substrate. In this thesis, we would be addressing the first two issues i.e. the development high performance III-V p-channels and obtaining high quality III-V/high-k interface. We start with using the device architecture of the already established InGaAs n-channels as a baseline to understand the effect of remote scattering from the high-k oxide and oxide/semiconductor interface on channel transport properties such as electron mobility and channel electron concentration. Temperature dependent Hall electron mobility measurements were performed to separate various scattering induced mobility limiting factors. Dependence of channel mobility on proximity of the channel to the oxide interface, oxide thickness, annealing conditions are discussed. The results from this work will be used in the design of the p-channel MOSFETs. Following this, InxGa1-xAs (x>0.53) is chosen as channel material for developing p-channel MOSFETs. Band engineering, strain induced valence band splitting and quantum confinement is used to improve channel hole mobility. Experimental results on the Hall hole mobility is presented for InxGa1-xAs channels with varying In content, thickness of the quantum well and temperature. Then, high mobility InxGa 1-xAs heterostructure thus obtained are integrated with in-situ deposited high-k gate oxide required for high performance p-MOSFET and discuss the challenges associated with the gated structure and draw conclusions on this material system. Antimonide based channel materials such as GaSb and InxGa 1-xSb are explored for III-V based p-MOSFETs in last two chapters. Options for Sb based strained QW channels to obtain maximum hole mobility by varying the strain, channel and barrier material, thickness of the layers etc. is discussed followed by the growth of these Sb channels on GaAs and InP substrates using molecular beam epitaxy. The physical properties of the structures such as the heterostructure quality, alloy content and surface roughness are examined via TEM, XRD and AFM. Following this, electrical measurement results on Hall hole mobility is presented. The effect of strain, alloy content, temperature and thickness on channel mobility and concentration is reported. Development of GaSb n- and p-MOS capacitor structures with in-situ deposited HfO2 gate oxide dielectric using in-situ deposited amorphous Si (a-Si) interface passivation layer (IPL) to improve the interface quality of high-k oxide and (In)GaSb surface is presented. In-situ deposited gate oxides such as Al2O3 and combination oxide of Al 2O3 and HfO2 with and without the a-Si IPL are also explored as alternate gate dielectrics. Subsequently, MOS capacitor structures using buried InGaSb QWs are demonstrated. Development of an inversion type bulk GaSb with implanted source-drain contacts and in-situ deposited gate oxide HfO2 gate oxide is discussed. The merits of biaxial compressive strain is demonstrated on strained surface and buried channel In0.36 Ga0.64Sb QW MOSFETs with thin top

Nagaiah, Padmaja

108

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

SciTech Connect

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

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

2008-11-01

109

Electrical performance of III-V gate-all-around nanowire transistors  

NASA Astrophysics Data System (ADS)

The performance of III-V inversion-mode and junctionless nanowire field-effect transistors are investigated using quantum simulations and are compared with those of silicon devices. We show that at ultrascaled dimensions silicon can offer better electrical performance in terms of short-channel effects and drive current than other materials. This is explained simply by suppression of source-drain tunneling due to the higher effective mass, shorter natural length, and the higher density of states in the confined channel. We also confirm that III-V junctionless nanowire transistors are more immune to short-channel effects than conventional inversion-mode III-V nanowire field-effect transistors.

Razavi, Pedram; Fagas, Giorgos

2013-08-01

110

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

111

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

112

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

NASA Technical Reports Server (NTRS)

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

Soest, J. F.

1972-01-01

113

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

114

III-V multiple quantum well long-wavelength infrared detectors  

Microsoft Academic Search

Quantum well infrared photodetectors (QWIP), based on intersubband absorption in III-V multiple quantum well (MQW) structures, have advanced considerably in the last several years for infrared detection in the spectral regions 3-5 mum and 8-12 mum. This investigation explored the molecular beam epitaxially grown n-type GaAs\\/AlGaAs, p-type lattice matched InGaAs\\/InP, and n-type lattice matched InGaAs\\/InP III-V intersubband photodetectors. In addition,

Deepak Kumar Sengupta

1997-01-01

115

Fabrication of high-efficiency heterogeneous Si/III-V integration with short optical vertical interconnect access  

NASA Astrophysics Data System (ADS)

Silicon nanophotonic platform based on a silicon-on-insulator substrate enables dense photonic integration due to transparency for light propagation and ultra-high refractive index contrast for light confinement. Here, we integrate silicon together with III-V for high-efficiency heterogeneous Silicon/III-V and short vertical optical interconnect access. The fabrication involves 3 critical processes: 1) obtaining more than 80% maximum bonded areas of Si with III-V, 2) precise alignment of III-V nano-devices on top of the passive devices and 3) vertical sidewall etch profile of Si and III-V devices. The measurement results show around 90% coupling efficiency. The realization of this heterogeneous Si/III-V integration platform will open up enormous opportunities for photonic system on silicon through integrating various devices.

Ng, Doris K. T.; Pu, Jing; Wang, Qian; Lim, Kim-Peng; Wei, Yongqiang; Wang, Yadong; Lai, Yicheng; Ho, Seng-Tiong

2013-03-01

116

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

NASA Astrophysics Data System (ADS)

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

Carlin, Andrew M.

117

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

Microsoft Academic Search

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

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

2005-01-01

118

Multi-color Long Wavelength Infrared Detectors Based on III-V Semiconductors.  

National Technical Information Service (NTIS)

Several III-V semiconductor material systems were investigated for multi-color photodetectors taking into consideration the enhanced properties of low dimensional systems, such as InAs quantum dots and GaAs quantum rings. The emphasis was placed on detect...

O. Manasreh

2010-01-01

119

Characterization of the Isc Versus Irradiance Relationship for Silicon and III-V Concentrator Cells.  

National Technical Information Service (NTIS)

The responsivity (which is defined as the short-circuit current divided by the irradiance) of silicon and III-V concentrator cells was measured for irradiances up to 1000X. The silicon cells have various resistivities and thicknesses and have both planar ...

J. M. Gee

1987-01-01

120

Engineering supermode silicon\\/III-V hybrid waveguides for laser oscillation  

Microsoft Academic Search

We analyze a silicon\\/III-V hybrid semiconductor waveguide structure for laser oscillation. We show that, by optimally designing and controlling the resonant supermode behavior in such structures, the modal gain can be enhanced five times compared with that of the existing silicon evanescent laser, while maintaining efficient coupling to outside silicon waveguide circuits. © 2008 Optical Society of America OCIS codes:

Xiankai Sun; Amnon Yariv

2008-01-01

121

Sputtering of III-V semiconductors under argon atom and ion bombardment  

NASA Astrophysics Data System (ADS)

III-V semiconductors sputtering under argon neutral and ion projectiles with energies from 150 to 600 eV was investigated. It is shown that the dependency on energy of sputtering yield is well described by the Sigmund-Falcone and Haff-Switkowski models in Yudin's approximation. It analyses the relation of the surface binding, atomization and amorphization energies.

Soshnikov, I. P.; Kudriavtsev, Yu. A.; Lunev, A. V.; Bert, N. A.

1997-05-01

122

Advanced single crystal III-V solar cell technology and its applications  

Microsoft Academic Search

Solar cells made from III-V single crystal semiconductors currently hold the world record for direct energy conversion efficiency from sunlight into electricity. This is true for both space and terrestrial applications, and for both one sun (flat plate collector) systems and concentration based systems which use lenses or mirrors to focus the light into a smaller collector area. This paper

T. A. Cross; C. R. Huggins

1995-01-01

123

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

National Technical Information Service (NTIS)

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, ...

J. C. Zolper S. J. Pearton C. R. Abernathy

1995-01-01

124

Atomic layer molecular beam epitaxy (Almbe) of III–V compounds: Growth modes and applications  

Microsoft Academic Search

A new development of molecular beam epitaxy (MBE) for III–V compounds is described, based on cyclic perturbation of the growth front at atomic layer level by periodic pulsing, alternating or interrupting the molecular beams. The modification of the growth mechanism caused by this perturbations is discussed and related to periodic changes of surface stoichiometry which induce 2D growth mechanism by

F. Briones; L. González; A. Ruiz

1989-01-01

125

GaAs FET Device Fabrication and Ion Implantation Technology (Microwave III-V Compound Semiconductors).  

National Technical Information Service (NTIS)

Microwave Schottky barrier FETs and ion implantation have been selected to provide a bench mark technology for evaluation of III-V compound semiconductor materials grown at NRL and elsewhere. FETs used here employ a nominal one micron gate length and are ...

K. J. Sleger H. B. Dietrich

1979-01-01

126

Monte Carlo simulation of III-V material-based MOSFET for high frequency and ultra-low consumption applications.  

PubMed

High-mobility III-V heterostructures are emerging and very promising materials likely to fulfil high-speed and low-power specifications for ambient intelligent applications. The main objective of this work is to theoretically explore the potentialities of MOSFET based on III-V materials with low bandgap and high electron mobility. First, the charge control is studied in III-V MOS structures using a Schrödinger-Poisson solver. Electronic transport in III-V devices is then analyzed using a particle Monte Carlo device simulator. The external access resistances used in the calculations are carefully calibrated on experimental results. The performance of different structures of nanoscale MOS transistor based on III-V materials is evaluated and the quasi-ballistic character of electron transport is compared to that in Si transistors of same gate length. PMID:21137856

Shi, Ming; Saint-Martin, Jérôme; Bournel, Arnaud; Maher, Hassan; Renvoise, Michel; Dollfus, Philippe

2010-11-01

127

Experimental demonstration of a hybrid III-V-on-silicon microlaser based on resonant grating cavity mirrors.  

PubMed

We present the experimental demonstration of a novel class of hybrid III-V-on-silicon microlasers. We show that by coupling a silicon cavity to a III-V waveguide, the interaction between the propagating mode in the III-V waveguide and the cavity mode in the silicon resonator results in high, narrowband reflection back into the III-V waveguide, forming a so-called resonant mirror. By combining two such mirrors and providing optical gain in the III-V wire between these two mirrors, laser operation can be realized. This optically pumped device measures 55 by 2 ?m, requires microwatt-level threshold pump power, and shows single-mode laser emission with a side-mode suppression ratio of up to 39 dB. PMID:23939092

de Koninck, Yannick; Raineri, Fabrice; Bazin, Alexandre; Raj, Rama; Roelkens, Gunther; Baets, Roel

2013-07-15

128

Anisotropic photonic properties of III-V nanowires in the zinc-blende and wurtzite phase  

NASA Astrophysics Data System (ADS)

Some critical aspects of the anisotropic absorption and emission properties of quasi one-dimensional structures are reviewed in the context of III-V compound semiconductor nanowires. The unique optical and electronic properties of III-V nanowires stem from the combination of dielectric effects due to their large aspect ratio, and their specific crystallographic structure which can differ significantly from the bulk case. The growth conditions leading to single-crystal nanowires with either zinc blende or wurtzite phase are first presented. Dipole selection rules for interband transitions in common III-V compounds are then summarized for the two different phases, and corroborated by ab initio Density Functional Theory calculations of the oscillator strength. The optical anisotropy is discussed considering both the effect of refractive index mismatch between the nanowire and its surroundings and the polarization of the emitting dipoles set by the nanowire crystallographic structure and orientation. Finite Difference Time Domain simulations are finally employed to illustrate the influence of the emitting dipole orientation and the nanowire diameter on the distribution of radiation in the far-field. The importance of the correlation between structural and optoelectronic properties is highlighted in view of potential applications in future nanowire photonics.Some critical aspects of the anisotropic absorption and emission properties of quasi one-dimensional structures are reviewed in the context of III-V compound semiconductor nanowires. The unique optical and electronic properties of III-V nanowires stem from the combination of dielectric effects due to their large aspect ratio, and their specific crystallographic structure which can differ significantly from the bulk case. The growth conditions leading to single-crystal nanowires with either zinc blende or wurtzite phase are first presented. Dipole selection rules for interband transitions in common III-V compounds are then summarized for the two different phases, and corroborated by ab initio Density Functional Theory calculations of the oscillator strength. The optical anisotropy is discussed considering both the effect of refractive index mismatch between the nanowire and its surroundings and the polarization of the emitting dipoles set by the nanowire crystallographic structure and orientation. Finite Difference Time Domain simulations are finally employed to illustrate the influence of the emitting dipole orientation and the nanowire diameter on the distribution of radiation in the far-field. The importance of the correlation between structural and optoelectronic properties is highlighted in view of potential applications in future nanowire photonics. This article was submitted as part of a collection highlighting papers on the `Recent Advances in Semiconductor Nanowires Research' from ICMAT 2011.

Wilhelm, Christophe; Larrue, Alexandre; Dai, Xing; Migas, Dmitri; Soci, Cesare

2012-02-01

129

High crystalline-quality III-V layer transfer onto Si substrate  

NASA Astrophysics Data System (ADS)

In this study, an approach combining ion cutting and selective chemical etch for the transfer of high crystalline-quality III-V layers on SiO2/Si substrate has been investigated. This layer transfer scheme takes advantage of the ion-cutting process by conserving III-V substrates for reuse and simultaneously improving the transferred layer quality and surface condition without using chemical and mechanical polishing. The relocation of the ion-implantation damage maximum enables the transfer of relatively defect-free InP-based layers onto a Si substrate coated with an oxide layer and results in structures ready for further optoelectronic device fabrication or epitaxial growth.

Chen, Peng; Jing, Yi; Lau, S. S.; Xu, Dapeng; Mawst, Luke; Alford, T. L.; Paulson, Charles; Kuech, T. F.

2008-03-01

130

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

131

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

132

MBE growth technology for high quality strained III-V layers  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

133

Spin-orbit interaction strength and anisotropy in III-V semiconductor heterojunctions  

NASA Astrophysics Data System (ADS)

The spin-orbit interaction strength for electrons in III-V semiconductor heterojunctions and the corresponding in-plane anisotropy are theoretically studied, considering Rashba and Dresselhaus contributions. Starting from a variational solution of Kane's effective Hamiltonian for the Rashba-split subbands, the total spin-orbit splitting at the Fermi level of the two-dimensional electron gas in III-V heterojunctions is calculated analytically, as a function of the electron density and wave-vector direction, by adding the Dresselhaus contribution within quasidegenerate first-order perturbation theory. Available GaAs and InGaAs experimental data are discussed. Effects of the barrier penetration are identified, and the spin-orbit anisotropy is shown to be determined by more than one parameter, even in the small-k limit, contrary to the commonly used ?/? (where ? is the Rashba and ? the Dresselhaus interaction) single-parameter picture.

Toloza Sandoval, M. A.; Ferreira da Silva, A.; de Andrada e Silva, E. A.; La Rocca, G. C.

2013-02-01

134

High crystalline-quality III-V layer transfer onto Si substrate  

SciTech Connect

In this study, an approach combining ion cutting and selective chemical etch for the transfer of high crystalline-quality III-V layers on SiO{sub 2}/Si substrate has been investigated. This layer transfer scheme takes advantage of the ion-cutting process by conserving III-V substrates for reuse and simultaneously improving the transferred layer quality and surface condition without using chemical and mechanical polishing. The relocation of the ion-implantation damage maximum enables the transfer of relatively defect-free InP-based layers onto a Si substrate coated with an oxide layer and results in structures ready for further optoelectronic device fabrication or epitaxial growth.

Chen Peng; Jing Yi; Lau, S. S. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Xu Dapeng; Mawst, Luke [Electrical and Computer Engineering Department, University of Wisconsin, Madison, Wisconsin 53706 (United States); Alford, T. L. [School of Materials, Arizona State University, Tempe, Arizona 85287-8706 (United States); Paulson, Charles; Kuech, T. F. [Department of Chemical and Biological Engineering, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2008-03-03

135

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

136

High dielectric constant oxides on III-V complementary metal-oxide-semiconductors  

NASA Astrophysics Data System (ADS)

Suitable gate dielectrics are needed for III-V channel metal-oxide-semiconductor field-effect transistors (MOSFETs). III-V semiconductor surfaces tend to have high interface trap state density (Dit). High quality gate dielectrics require a high dielectric constant, a stable interface, and low Dit. The major challenges are scaling down the dielectric to achieve high capacitance densities, understanding defects at the oxide/semiconductor interface, and developing techniques to passivate Dit at the interface. By using nitrogen plasma pre-treatment passivation technique, MOSCAPs with ALD HfO 2 directly on InGaAs as high-k gate stack, with accumulation capacitance density 2.4 mu F/cm2 (EOT=0.6 nm) and 2.5 x 10 12 cm2 eV-1 midgap Dit have been achieved.

Chobpattana, Varistha

137

Fundamental Studies of Halogen Reactions with Iii-V Semiconductor Surfaces  

NASA Astrophysics Data System (ADS)

It is technologically important to understand how halogens react with semiconductor surfaces because halogen compounds are commonly used to etch semiconductor wafers in the microelectronics industry. Halogens are also model adsorbates for studying chemisorption on covalently bonded materials, such as semiconductors, owing to the simple nature of the bonds that they form. The growing use of III-V materials in the manufacture of optoelectronic devices has prompted investigations of the reactions of molecular halogens (XeF2, Cl2, Br2, and I2) with III-V semiconductor surfaces (GaAs, GaSb, InP, InAs, and InSb). This review examines the more fundamental of these investigations, which involve model systems in ultra-high vacuum, focusing on the chemistry of the halogen surface reactions and the physical and electronic structure of the reacted surfaces.

Simpson, William C.; Yarmoff, Jory A.

1996-10-01

138

Hybrid III-V/silicon single-mode laser with periodic microstructures.  

PubMed

In this Letter, a III-V/silicon hybrid single-mode laser operating at C band for photonic integration circuit is presented. The InGaAlAs gain structure is bonded onto a patterned silicon-on insulator through wafer to wafer directly. The mode selected mechanism based on a hybrid III-V/silicon straight cavity with periodic microstructures is applied, which only need low cost i-line projection photolithography in the whole technological process. At room temperature, we obtain 0.62 mW output power in continuous-wave. The side mode suppression ratio of larger than 20 dB is obtained from experiments. [corrected]. PMID:23503234

Zhang, Yejin; Qu, Hongwei; Wang, Hailing; Zhang, Siriguleng; Ma, Shaodong; Qi, Aiyi; Feng, Zhigang; Peng, Hongling; Zheng, Wanhua

2013-03-15

139

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

NASA Astrophysics Data System (ADS)

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 FM only at low temperature (below about 150 K). Here we present the results of our studies in III-V (InSb) and II-IV-V 2 (CdGeAs 2 and CdGeP 2) materials doped with Mn which exhibit robust ferromagnetism at room temperature. ?SR experiments show that this ferromagnetism is a bulk phenomenon.

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

2006-03-01

140

Universal alignment of transition metal impurity levels in III V and II VI compound semiconductors  

NASA Astrophysics Data System (ADS)

Existence of a universal energy reference level E HO (Hasegawa-Ohno's hybrid orbital energy level) is pointed out for transition metal (TM) deep levels in tetrahedral semiconductors. When viewed from this reference level, each TM energy level E(TM) in major III-V and II-VI compound semiconductor satisfies a simple universal relation of E( TM) = E HO ± ( m + {1}/{2}) ? E with m = 0, 1, 2, -- and the empirical energy separation quantum ?E = 0.244 eV for II-VI compounds and 0.240 eV for III-V compounds. The so-called vacuum level pinning of TM levels is not generally valid. The band line-up based on the new TM level alignment is in excellent agreement with experiment.

Hasegawa, Hideki

1986-04-01

141

Electronic, linear, and nonlinear optical properties of III-V indium compound semiconductors  

Microsoft Academic Search

We have made an extensive theoretical study of the electronic, linear, and nonlinear optical properties of the III-V indium compound semiconductors InX (X=P, As, and Sb) with the use of full potential linear augmented plane wave method. The results for the band structure, density of states, and the frequency-dependent linear and nonlinear optical responses are presented here and compared with

Ali Hussain Reshak

2006-01-01

142

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

143

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

144

Electrochemical processes for formation, processing and gate control of III–V semiconductor nanostructures  

Microsoft Academic Search

This paper reviews recent efforts by authors’ group to utilize electrochemical processes for formation, processing and gate control of III–V semiconductor nanostructures. Topics include precise photo-anodic and pulsed anodic etching of InP, formation of arrays of ?001?-oriented straight nanopores in n-type (001)InP by anodization and their possible applications and macroscopic and nanometer-scale metal contact formation on GaAs, InP and GaN

Hideki Hasegawa; Taketomo Sato

2005-01-01

145

Molecular beam epitaxy passivation studies of Ge and III–V semiconductors for advanced CMOS  

Microsoft Academic Search

Future CMOS technologies will require the use of substrate material with a very high mobility in order to fulfil the performance requirements. Therefore, combination of Ge p-MOS with n-MOS devices made out of high mobility III\\/V compounds, such as GaAs, has recently received some attention for its possible use in advanced CMOS applications. In this work, the physical, chemical and

C. Merckling; J. Penaud; D. Kohen; F. Bellenger; A. Alian; G. Brammertz; M. El-Kazzi; M. Houssa; J. Dekoster; M. Caymax; M. Meuris; M. M. Heyns

2009-01-01

146

Alternative materials for RF MEMS switches in III–V technology  

Microsoft Academic Search

In this work we develop surface-micromachined RF MEMS switches in III-V technology making use of materials which can be alternative to the ones commonly used. In this way, some technological constraints concerning RF MEMS reliability can be overcome. Specifically, we evaluate the potential of tantalum nitride (TaN) and tantalum pentoxide (Ta2O5) to be used for the switches actuation pads and

Anna Persano; Fabio Quaranta; Adriano Cola; Maria Concetta Martucci; Pasquale Cretì; Antonietta Taurino; Pietro Siciliano; Romolo Marcelli; Giorgio De Angelis; Andrea Lucibello

2010-01-01

147

Optimized Tersoff potential parameters for tetrahedrally bonded III-V semiconductors  

Microsoft Academic Search

We address the issue of accurate parametrization for the Abell-Tersoff empirical potential applied to tetra- hedrally bonded semiconductor materials. Empirical potential methods for structural relaxation are widely used for group IV semiconductors while, with few notable exceptions, work on III-V materials has not been extensive. In the case of the Abell-Tersoff potential parametrizations exist only for III-As and III-N, and

D. Powell; M. A. Migliorato; A. G. Cullis

2007-01-01

148

III-V solar cell growth on wafer-bonded GaAs\\/Si-substrates  

Microsoft Academic Search

The MOVPE (Metal Organic Vapour Phase Epitaxy) growth of GaAs single-junction solar cells on layer transferred GaAs\\/Si-substrates is reported. This novel type of alternative substrates for III-V epitaxial growth was realised by performing the Smart Cuttrade technology. HRXRD-measurements proved good material quality by a FWHM of about 30 arcsecond reveal a dislocation density below 4times105 cm -2 for a 5

J. Schone; F. Dimroth; A. W. Bett; A. Tauzin; C. Jaussaud; J.-C. Roussin

2006-01-01

149

First principles pseudopotential calculations of zone boundary phonon frequencies of III-V zincblende semiconductors  

Microsoft Academic Search

Longitudinal zone boundary X phonon frequencies have been calculated by a first principles pseudopotential method for III-V zincblende semiconductors AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs and InSb. The phonon frequencies have been evaluated from total energy calculations in the frozen phonon approximation. The calculated phonon frequencies agree very well with the experimental values.

Wang Jian-Qing; Gu Zong-Quan; Li Ming-Fu

1991-01-01

150

First Principles Study of the Cross-Sectional Surface Structure of III-V Superlattices  

Microsoft Academic Search

Using first-principles density-functional theory and scanning tunneling microscopy, we study the detailed interface structure and cross-sectional STM topography of 6.1-Å III-V superlattices. We first determine the interface geometry of InAs\\/GaSb superlattices within the Local Density Approximation (LDA) and pseudopotential formalism. By integrating the resulting local density of states, we then generate simulated STM images over the cross-sectional surface and compare

Seong-Gon Kim; S. C. Erwin; B. Z. Nosho; L. J. Whitman

2000-01-01

151

Porous III-V compound semiconductors: formation, properties, and comparison to silicon  

Microsoft Academic Search

Pore formation in n-type III-V semiconductors will be discussed and compared to pore formation in silicon. While by now many different kinds of pores were produced in silicon, the pore zoology in III-Vs was rather limited until recently. This paper will briefly review the specific pore morphologies in some compound semiconductors, nucleation and formation mechanisms, the relation to comparable Si

H. Föll; J. Carstensen; S. Langa; M. Christophersen; I. M. Tiginyanu

2003-01-01

152

Nuclear quadrupolar spin-lattice relaxation in some III-V compounds  

Microsoft Academic Search

Measurements of the spin-lattice relaxation rates in the group-III-V compounds, GaAs, GaSb, InAs, and InSb, are presented as a function of temperature from 4 to 300 K. These rates, except for GaSb, are separated into magnetic and quadrupolar parts. The quadrupolar rates are separated into relaxation by acoustic phonons and that by optical phonons. A simple phenomenological model fits the

John A. McNeil; W. Gilbert Clark

1976-01-01

153

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

DOEpatents

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

Alivisatos, A. Paul (Oakland, CA); Peng, Xiaogang (Fayetteville, AR); Manna, Liberato (Palo del Colle, IT)

2001-01-01

154

Device physics studies of III-V and silicon MOSFETs for digital logic  

NASA Astrophysics Data System (ADS)

III-V's are currently gaining a lot of attraction as possible MOSFET channel materials due to their high intrinsic mobility. Several challenges, however, need to be overcome before III-V's can replace silicon (Si) in extremely scaled devices. The effect of low density-of-states of III-V materials is investigated by analyzing the semiconductor capacitance for different device structures and scaling. Solid solubility limit of dopants in the III-V materials are also significantly lower than that in Si, causing high series resistance, and transconductance degradation due to source exhaustion. The metallic source/drain Schottky barrier MOSFET is explored as an alternative to effectively eliminate these issues. The performance of a Si channel SOI MOSFET fabricated at IBM is analyzed and interpreted using ballistic transport. The ballistic ratio and extracted mean free paths demonstrate that scattering effects cannot be ignored in modern Si channel devices. Scattering has been implemented within the non-equilibrium Green's function (NEGF) framework to investigate effects of phonon and surface roughness scattering on device performance. The computational complexity is greatly reduced by analytically integrating over the transverse (width) dimension, making it possible to include scattering in planar FETs. The model has been carefully benchmarked with analytical formulas and Boltzmann transport calculations (2-D Monte Carlo results) for simple potential profiles. The scattering model is used to study the role of phonon scattering on the on-state characteristics of Si channel devices. Finally, the role of surface roughness scattering and its implementation issues within NEGF is discussed.

Pal, Himadri Sekhar

155

The first ten megawatts of III–V multi-junction concentrator solar cell production  

Microsoft Academic Search

Manufacturing technology is being developed for the mass-production III–V multijunction solar cells and receiver sub-assemblies to help enable the emerging concentrator PV industry. Production contracts of various sizes have allowed us to begin exercising this manufacturing technology, and significant momentum has been realized toward fulfilling large production contracts. Over 400,000 solar cells equivalent to 10 megaWatts under standard test conditions

Daniel Aiken; Brad Clevenger; Frederick Newman; Bruce Smith; Cory Tourino; Jerry Wilson; Jody Wood

2008-01-01

156

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

NASA Astrophysics Data System (ADS)

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

Nemcsics, Ákos

2014-05-01

157

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

PubMed

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

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

2011-05-23

158

III-V quantum light source and cavity-QED on silicon.  

PubMed

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. PMID:23393621

Luxmoore, I J; Toro, R; Del Pozo-Zamudio, O; 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

159

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

160

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

161

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

PubMed

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. PMID:23182996

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

2012-12-21

162

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

163

Study of III-V Semiconductor Clusters using Anion Photoelectron Spectroscopy  

NASA Astrophysics Data System (ADS)

III-V semiconductor materials are used in various electronic applications. III-V clusters are therefore a subject of extensive investigation because of the desired capability to fine tune the properties in a bottom-up approach. Evidence for band gap tunability is presented as one of the examples here. It is shown that changing the amount of gallium, changes the band gap in Bi3Gay^(-) clusters. Now, depending upon how stable the cluster is for a given band gap it can be used to assemble nanomaterials. It is found that Bi3Ga2^-, Bi3Ga3, Bi3Ga4^- and Bi3Ga5 are stable with a calculated band gap ranging from 1.17 eV to 1.89 eV, using mass spectrometry, photoelectron spectroscopy and computational results. Additionally, it is shown that the electronic properties remain similar when an element from III-V cluster is replaced with another from the same group. This gives an opportunity to fine tune the material further depending upon the requisite physical properties. In this context, the example given is for gallium in BixGay clusters replaced with indium to make BixIny clusters. The electronic properties remain similar but unlike gallium, indium is not a liquid at room temperature which makes indium relatively easier to handle.

Gupta, Ujjwal; Ulises Reveles, J.; Melko, Joshua; Khanna, Shiv; Castleman, A. W., Jr.

2008-05-01

164

Anisotropic photonic properties of III-V nanowires in the zinc-blende and wurtzite phase.  

PubMed

Some critical aspects of the anisotropic absorption and emission properties of quasi one-dimensional structures are reviewed in the context of III-V compound semiconductor nanowires. The unique optical and electronic properties of III-V nanowires stem from the combination of dielectric effects due to their large aspect ratio, and their specific crystallographic structure which can differ significantly from the bulk case. The growth conditions leading to single-crystal nanowires with either zinc blende or wurtzite phase are first presented. Dipole selection rules for interband transitions in common III-V compounds are then summarized for the two different phases, and corroborated by ab initio Density Functional Theory calculations of the oscillator strength. The optical anisotropy is discussed considering both the effect of refractive index mismatch between the nanowire and its surroundings and the polarization of the emitting dipoles set by the nanowire crystallographic structure and orientation. Finite Difference Time Domain simulations are finally employed to illustrate the influence of the emitting dipole orientation and the nanowire diameter on the distribution of radiation in the far-field. The importance of the correlation between structural and optoelectronic properties is highlighted in view of potential applications in future nanowire photonics. PMID:22327202

Wilhelm, Christophe; Larrue, Alexandre; Dai, Xing; Migas, Dmitri; Soci, Cesare

2012-03-01

165

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

166

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

167

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

168

Examination of the Ion Beam Response of III-V Semiconductor Substrates  

NASA Astrophysics Data System (ADS)

This work examines the response of the III-V materials to ion beam irradiation in a series of four experimental studies and describes the observed results in terms of the fundamental materials processes and properties that control ion-induced change in those compounds. Two studies investigate the use of Ga+ focused ion beam (FIB) irradiation of III-V substrate materials to create nanostructures. In the first, the creation of FIB induced group III nanodots on GaAs, InP, InAs, and AlAs is studied. The analysis of those results in terms of basic material properties and a simple nanodot growth model represents the first unified investigation of the fundamental processes that drive the nanodot forming behavior of the III-V compounds. The second nanostructure formation study reports the discovery and characterization of unique spike-like InAs nanostructures, termed "nanospikes," which may be useful for nanoscale electronic or thermoelectric applications. A novel method for controlling nanospike formation using InAs/InP heterostructures and film pre-patterning is developed, and the electrical properties of these ion erosion created nanostructures are characterized by in-situ TEM nanoprobe testing in a first-of-its-kind examination. The two remaining studies examine methods for using ion beam modification of III-V substrates to accommodate lattice-mismatched film growth with improved film properties. The first examines the effects of film growth on a wide range of different FIB created 3-D substrate patterns, and finds that 3-D surface features and patterns significantly alter film morphology and that growth on or near FIB irradiated regions does not improve film threading defect density. The second substrate modification study examines broad beam ion pre-implantation of GaAs wafers before InGaAs film growth, and is the first reported study of III-V substrate pre-implantation. Ar + pre-implantation was found to enhance the formation of threading defects in InGaAs films and so improve their roughness and degree of relaxation. This effect, combined with a threading dislocation filtering structure, is anticipated to produce high quality buffers for lattice-mismatched film growth.

Grossklaus, Kevin A.

169

Bonding III-V material to SOI with transparent and conductive ZnO film at low temperature.  

PubMed

A procedure of bonding III-V material to SOI at low temperature using conductive and transparent adhesive ZnO as intermediate layer is demonstrated. Bonding layer thickness of less than 100 nm was achieved in our experiment that guaranteed good light coupling efficiency between III-V and silicon. This bonding method showed good bonding strength with shear stress of 80 N/cm2. The lowest resistance of the bonded samples was 48.9 ? and the transmittance of the spin-coated ZnO layer was above 99%. This procedure is applicable for fabricating hybrid III-V/Si lasers. PMID:24977526

Huang, Xinnan; Gao, Yonghao; Xu, Xingsheng

2014-06-16

170

New narrow electronic band in heavily doped III–V semiconductors due to electron-phonon coupling  

Microsoft Academic Search

Electron-phonon interaction in heavily doped III–V semiconductors can lead to a singularity in the density of the localized electronic states in the narrow energy region near the bottom of the conduction band.

E. Ya Sherman

1995-01-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

172

Electronic structure and v alence of Mn imputiries in III-V semiconductors  

NASA Astrophysics Data System (ADS)

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 doe change the valence of Mn in GaP, favoring the divalent state under certain circumstances. Work supported by the Defense Advanced Research Project Agency and by the Division of Materials Science and Engineering, U.S. Department of Energy, under Contract DE-AC05-00OR22725 with UT-Battelle LLC.

Schulthess, T. C.; Temmerman, W.; Szotek, Z.; Stocks, G. M.; Butler, W. H.

2004-03-01

173

Optically Detected Magnetic Resonance and Microwave Electric Field Effects in Iii-V Semiconductors  

NASA Astrophysics Data System (ADS)

The optically detected magnetic resonance (ODMR) technique was employed at 3 and 16 GHz to study the P _{rm In} antisite defect in zinc-doped InP. A model for the competing antisite -to-acceptor and shallow-donor-to-acceptor luminescent processes was developed based on the ODMR and time resolved photoluminescence measurements. The proposed model is in good agreement with the observed ODMR effects. The ODMR technique was also used to study defects in the ternary III-V semiconducting system GaPSb. The study revealed the presence of at least three impurity or defect-related spin dependent recombination centers. No unambiguous identification of the microscopic defects or impurities was possible based solely on the 3 GHz ODMR measurements, but the tentative assignment include a residual shallow acceptor impurity (perhaps carbon), a phosphorous antisite occupying an antimony lattice site, a phosphorous interstitial and a residual shallow donor. The effects of the microwave electric field on the photoluminescent processes, frequently observed as nonresonant background signals in ODMR measurements, were investigated in a large number of binary and ternary III -V semiconductors using the microwave modulated photoluminescence (MMPL) technique. The experimental and theoretical investigations of the MMPL in III-V semiconductors revealed that changes in the donor-to-acceptor photoluminescence (PL) intensity in the binary compounds examined was due to the impact ionization of neutral donors by photoexcited free carriers accelerated in the microwave electric field. Elastic scattering processes were shown to be important in the impact ionization process. The randomization of the free carrier velocity vector in the elastic scattering processes allows the carriers to gain energy from a time varying electric field. For a fraction of the free carriers the energy gain from even a small microwave electric field is sufficient to impact ionize neutral donors. In many ternary compounds the observed MMPL signal was attributed to a thermal modulation of the PL by the microwave electric field, i.e., microwave heating.

Viohl, Ingmar

174

Evaluation of selective energy contact for hot carrier solar cells based on III–V semiconductors  

Microsoft Academic Search

We investigate hot carrier solar cells using III-V semiconductors. Here, the properties of a quantum well double barrier resonant tunneling structure comprised of Al0.6Ga0.4As\\/GaAs\\/Al0.6Ga0.4As was used as selective energy contacts (SEC). The sample was fabricated by MBE on GaAs(001). The GaAs epitaxial layers were used as the optical absorbing layer. A quantum well resonant tunneling structure was adopted here for

Shuhei Yagi; Ryuji Oshima; Yoshitaka Okada

2009-01-01

175

Low coverage of III V semiconductor surfaces within TB-LMTO-ASA approach  

NASA Astrophysics Data System (ADS)

The self-consistent Green's function technique for surface and interfaces is applied to semi-infinite crystals of various III-V semiconductors in the tight-binding LMTO-ASA scheme. We have studied the deposition of metallic and nonmetallic full monolayers and half monolayers on an ideal unrelaxed (110) surface of GaAs, InAs and InP. The surface and ionization energies for different low coverages of a (110) surface by Al, Cu and S are calculated and compared.

Adamowicz, L.; Zbroszczyk, M.

1997-04-01

176

III-V/silicon photonic integrated circuits for communication and sensing applications  

NASA Astrophysics Data System (ADS)

In this paper we review our work in the field of heterogeneous integration of III-V semiconductors and non-reciprocal optical materials on a silicon waveguide circuit. We elaborate on the heterogeneous integration technology based on adhesive DVS-BCB die-to-wafer bonding and discuss several device demonstrations. The presented devices are envisioned to be used in photonic integrated circuits for communication applications (telecommunications and optical interconnects) as well as in spectroscopic sensing systems operating in the short-wave infrared wavelength range.

Roelkens, Gunther; Keyvaninia, Shahram; Stankovic, Stevan; De Koninck, Yannick; Tassaert, Martijn; Mechet, Pauline; Spuesens, Thijs; Hattasan, N.; Gassenq, A.; Muneeb, M.; Ryckeboer, E.; Ghosh, Samir; Van Thourhout, D.; Baets, R.

2013-03-01

177

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

178

A New Thermal-Oxidation Method for III-V Semiconductors  

NASA Astrophysics Data System (ADS)

A new thermal-oxidation method for III-V semiconductors that utilizes boiling water under high pressure conditions has been proposed and applied to InSb. The grown oxide has been characterized by RBS, AES and XPS measurements. The oxidation temperature was decreased below 200°C. The oxidized Sb distributed uniformly throughout the oxide and there was no pile-up of the Sb at the oxide-semiconductor interface. The resistivity of the oxide at 77 K was as high as 1014 ? cm.

Takagi, Yuhichi; Sugiura, Osamu; Naruke, Yasuo; Takahashi, Toshio; Matsumura, Masakiyo

1984-07-01

179

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

180

Monolithic III-V Nanowire Solar Cells on Graphene via Direct van der Waals Epitaxy.  

PubMed

Novel solar cells, based on dense arrays of InGaAs nanowires, are grown directly on graphene. Here, graphene serves as the conductive back contact and growth template for van der Waals epitaxial assembly of vertical nanowires. Although far from being the optimum material, core-shell p-n junction In0.25 Ga0.75 As nanowire arrays demonstrate a conversion efficiency of 2.51%, representing a new record for substrate-free, III-V nanowire-based solar cells. PMID:24652703

Mohseni, Parsian K; Behnam, Ashkan; Wood, Joshua D; Zhao, Xiang; Yu, Ki Jun; Wang, Ning C; Rockett, Angus; Rogers, John A; Lyding, Joseph W; Pop, Eric; Li, Xiuling

2014-06-01

181

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

182

Polaron properties of III-V nitride compounds: second-order effects  

NASA Astrophysics Data System (ADS)

The polaron binding energy and effective mass are obtained for bulk III-V nitride compounds with wurtzite crystalline structure with the use of a recently derived dielectric continuum Fröhlich-like electron-phonon interaction Hamiltonian which accounts for the mixing of the longitudinal optical and transverse optical polarization due to the anisotropy. Corrections are calculated up to second order in the coupling constants. Numerical results are reported for GaN and AlN. Good quantitative agreement with experimental results for the electronic effective mass is obtained for GaN.

Mora-Ramos, M. E.; Rodríguez, F. J.; Quiroga, L.

1999-10-01

183

Epitaxy of group IV optical materials and synthesis of IV/III-V semiconductor analogs by designer hydride chemistries  

NASA Astrophysics Data System (ADS)

The thesis studies new methods to fabricate optoelectronic Ge1-y Sny/Si(100) alloys and investigate their photoluminescence (PL) properties for possible applications in Si-based photonics including IR lasers. The work initially investigated the origin of the difference between the PL spectrum of bulk Ge, dominated by indirect gap emission, and the PL spectrum of Ge-on-Si films, dominated by direct gap emission. It was found that the difference is due to the supression of self-absorption effects in Ge films, combined with a deviation from quasi-equilibrium conditions in the conduction band of undoped films. The latter is confirmed by a model suggesting that the deviation is caused by the shorter recombination lifetime in the films relative to bulk Ge. The knowledge acquired from this work was then utilized to study the PL properties of n-type Ge1-ySny/Si (y=0.004-0.04) samples grown via chemical vapor deposition of Ge2H 6/SnD4/P(GeH3)3. It was found that the emission intensity (I) of these samples is at least 10x stronger than observed in un-doped counterparts and that the I dir/Iind ratio of direct over indirect gap emission increases for high-Sn contents due to the reduced gamma-L valley separation, as expected. Next the PL investigation was expanded to samples with y=0.05-0.09 grown via a new method using the more reactive Ge3H 8 in place of Ge2H6. Optical quality, 1-um thick Ge1-ySny/Si(100) layers were produced using Ge 3H10/SnD4 and found to exhibit strong, tunable PL near the threshold of the direct-indirect bandgap crossover. A byproduct of this study was the development of an enhanced process to produce Ge 3H8, Ge4H10, and Ge5H 12 analogs for application in ultra-low temperature deposition of Group-IV semiconductors. The thesis also studies synthesis routes of an entirely new class of semiconductor compounds and alloys described by Si5-2y(III-V) y (III=Al, V= As, P) comprising of specifically designed diamond-like structures based on a Si parent lattice incorporating isolated III-V units. The common theme of the two thesis topics is the development of new mono-crystalline materials on ubiquitous silicon platforms with the objective of enhancing the optoelectronic performance of Si and Ge semiconductors, potentially leading to the design of next generation optical devices including lasers, detectors and solar cells.

Grzybowski, Gordon

184

Anomalous behaviours of the electrical resistivity of the melt of a typical III-V Ga-Sb system  

NASA Astrophysics Data System (ADS)

The electrical resistivity, icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/>, was measured for the melt of a typical III-V semiconductor system, Ga-Sb, by the direct-current four-probe method. Similarly to the case for solid substitutional alloys, the Nordheim rule almost establishes the concentration dependence of icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/>. That is, a rather parabolic form of icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/>icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/> was obtained as a function of composition; icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/>icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/> is the deviation of the resistivity from the linear law relating the resistivities of the pure components, liquid Ga and liquid Sb. In spite of this rather simple behaviour of the concentration dependence of icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/> itself, its temperature coefficient, dicons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/>/dT, shows a clear minimum at the eutectic composition and even a negative temperature coefficient was observed near the eutectic point. This negative dicons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/>/dT may be the first indication for the existence of particular hidden structure, related to concentration fluctuations, in the liquid near the eutectic point. In addition, this strange behaviour of dicons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/>/dT was discussed on the basis of the effective-medium theory.

Aoki, H.; Shibata, T.; Itami, T.

1999-12-01

185

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

186

Research advances on III-V MOSFET electronics beyond Si CMOS  

NASA Astrophysics Data System (ADS)

An overview is given on recent advances of science and devices of III-V based and Si MOS and MOSFET. Firstly, we have integrated molecular beam epitaxy (MBE) with atomic layer deposition (ALD) for the growth of excellent high- ? dielectrics with abrupt interfaces, critical for further complementary metal-oxide-semiconductor (CMOS) scaling beyond the 45 nm node. Secondly, we showed that epitaxial yttrium-doped HfO 2 films on GaAs(1 0 0) have stabilized the cubic phase, and led to enhancement of ? over 30. Thirdly, inelastic electron tunneling spectroscopy (IETS) was applied to probe the phonon modes and charge trappings within the high- ? dielectrics. Fourthly, scaling of the high- ? oxides approaching 1.0 nm capacitance equivalent thickness (CET) is achieved in a Ga 2O 3(Gd 2O 3)[GGO]/In 0.2Ga 0.8As (InGaAs) gate stack that has undergone 850 °C rapid thermal annealing, and which has unpinned the surface Fermi level of the III-V semiconductor. Finally, we have demonstrated a self-aligned inversion-channel In 0.53Ga 0.47As MOSFETs made of Al 2O 3(2 nm)/GGO(7 nm) gate oxide and TiN metal gate at 1-?m gate length, reaching a world record of drain current and transconductance.

Kwo, J.; Hong, M.

2009-03-01

187

Metal-seeded growth of III-V semiconductor nanowires: towards gold-free synthesis.  

PubMed

Semiconductor nanowires composed of III-V materials have enormous potential to add new functionality to electronics and optical applications. However, integration of these promising structures into applications is severely limited by the current near-universal reliance on gold nanoparticles as seeds for nanowire fabrication. Although highly controlled fabrication is achieved, this metal is entirely incompatible with the Si-based electronics industry. In this Feature we review the progress towards developing gold-free bottom-up synthesis techniques for III-V semiconductor nanowires. Three main categories of nanowire synthesis are discussed: selective-area epitaxy, self-seeding and foreign metal seeding, with main focus on the metal-seeded techniques. For comparison, we also review the development of foreign metal seeded synthesis of silicon and germanium nanowires. Finally, directions for future development and anticipated important trends are discussed. We anticipate significant development in the use of foreign metal seeding in particular. In addition, we speculate that multiple different techniques must be developed in order to replace gold and to provide a variety of nanowire structures and properties suited to a diverse range of applications. PMID:24522389

Dick, Kimberly A; Caroff, Philippe

2014-03-21

188

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

189

Anomalous first-order Raman scattering in III-V quantum dots: Optical deformation potential interaction  

NASA Astrophysics Data System (ADS)

In contrast to the most commonly studied nanocrystals of II-VI materials, resonant Raman spectra of colloidal III-V quantum dots (QDs) show two almost equally intense peaks centered approximately at the longitudinal and transverse optical (TO) bulk phonon frequencies. The “anomalous” spectra of III-V QDs are explained in the framework of a microscopic theory for the first-order resonant Raman scattering, which takes into account the optical deformation potential (ODP) and Fröhlich exciton-phonon interactions—valid for spherical nanoparticles. It is obtained that: (i) the “anomalous” TO peak is mostly due to confined phonon modes with the angular momentum lp=3 ; (ii) Raman intensity depends on the QD radius (R) as R-3 for the ODP mechanism, while for the Fröhlich one it is proportional to R-1 ; and (iii) the relative intensity ITO/ILO ratio value is higher in backscattering configuration for cross polarization than for parallel one. Raman spectra calculated within the Luttinger-Kohn Hamiltonian for the electronic states and a phenomenological theory of optical vibrations including rigorously both the mechanical and electrostatic matching boundary conditions explain the experimental data for InP QDs using bulk phonon parameters and ODP constant.

Rolo, Anabela G.; Vasilevskiy, Mikhail I.; Hamma, Mimoun; Trallero-Giner, Carlos

2008-08-01

190

Calculation of the electron mobility in III-V inversion layers with high-? dielectrics  

NASA Astrophysics Data System (ADS)

We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-? dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs.

O'Regan, T. P.; Fischetti, M. V.; Sorée, B.; Jin, S.; Magnus, W.; Meuris, M.

2010-11-01

191

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

NASA Astrophysics Data System (ADS)

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

Granados Alpizar, Bernal

192

Ab initio synthesis of single-layer III-V materials  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

193

Simulation studies on the liquid phase electroepitaxial growth of III V compound semiconductors  

NASA Astrophysics Data System (ADS)

In this paper, the growth kinetics of liquid phase electroepitaxy of III-V binary and ternary compound semiconductors have been studied. Concentration profiles of solute atoms such as As, P, Sb in front of a crystal (GaAs, InP, InAs, GaSb) interface growing in a In- or Ga-rich solution for the case of growth of binary compounds and for the case of ternary compounds (InGaAs, AlGaSb, InAsP) have been constructed using a computer simulation technique. The effect due to Peltier heating or cooling and electromigration during the growth have been incorporated to simulate the concentration profiles. The growth velocity in the absence and presence of convection, due to the Peltier effect and electromigration are calculated under different conditions. The results are discussed in detail.

Dhanasekaran, R.; Qhalid Fareed, R. S.; Ramasamy, P.

2001-07-01

194

Ab initio study on microscopic properties of III-V/water interfaces for photoelectrochemical hydrogen production  

NASA Astrophysics Data System (ADS)

Photoelectrodes made of III-V semiconductors are known to exhibit very high solar-to-hydrogen conversion efficiency (from solar energy to chemical energy as H2 bond); however, photocorrosion of the electrode in electrolyte solution remains an issue. Based on ab-initio molecular dynamics simulations, we study the structure, stability, and chemical activity of GaP/InP(001) semiconductor electrodes in contact with water. We will show how surface oxygen and hydroxyl change the electronic and chemical properties of water at the interface, leading to the formation of a strong hydrogen-bond network where fast surface hydrogen transport seems to be realized. Implications from our findings will be discussed in detail at the presentation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.

Wood, Brandon; Choi, Woon Ih; Schwegler, Eric; Ogitsu, Tadashi

2013-03-01

195

Phase transitions in Group III-V and II-VI semiconductors at high pressure  

NASA Technical Reports Server (NTRS)

The structures and transition pressures of Group III-V and II-VI semiconductors and of a pseudobinary system (Ga/x/In/1-x/Sb) have been investigated. Results indicate that GaP, InSb, GaSb, GaAs and possible AlP assume Metallic structures at high pressures; a tetragonal, beta-Sn-like structure is adopted by only InSb and GaSb. The rocksalt phase is preferred in InP, InAs, AlSb, ZnO and ZnS. The model of Van Vechten (1973) gives transition pressures which are in good agreement with measured values, but must be refined to account for the occurrence of the ionic rocksalt structure in some compounds. In addition, discrepancies between the theoretical scaling values for volume changes at the semiconductor-to-metal transitions are observed.

Yu, S. C.; Liu, C. Y.; Spain, I. L.; Skelton, E. F.

1979-01-01

196

Proposal for Compact Solid-State III-V Single-Plasmon Sources  

NASA Astrophysics Data System (ADS)

We propose a compact single-plasmon source operating at near-infrared wavelengths on an integrated III-V semiconductor platform, with a thin ridge waveguide serving as the plasmon channel. By attaching an ultrasmall cavity to the channel, it is shown that both the plasmon-generation efficiency (?) and the spontaneous decay rate into the channel can be significantly enhanced. An analytical model derived with the Lorentz reciprocity theorem captures the main physics involved in the design of the source and yields results in good agreement with fully vectorial simulations of the device. At resonance, it is predicted that the ultrasmall cavity increases the ? factor by 70% and boosts the spontaneous decay rate by a factor of 20. The proposed design could pave the way toward integrated and scalable plasmonic quantum networks. Comparison of the present design with other fully dielectric competing approaches is addressed.

Gan, C. H.; Hugonin, J. P.; Lalanne, P.

2012-04-01

197

Complex bandstructure of direct bandgap III-V semiconductors: application to tunneling  

NASA Astrophysics Data System (ADS)

Band to band tunneling in semiconductors fundamentally depends of the complex bandstructure of the semiconductor within its bandgap. In this work, the orientation dependent complex bandstructure of InSb, InAs, GaSb, InP and GaAs, and the orientation dependent probability of band to band tunneling in these materials have been computed using an sp3d5s? tight binding model. These direct bandgap III-V materials are attractive candidates for Tunnel FETs. Comparison of our results with Kane's two-band model commonly used in TCAD simulation, demonstrates the inaccuracies of the latter. Our results will be useful in the design of better performing Tunnel FETs in these materials.

Ajoy, Arvind

2012-10-01

198

Analytical modeling of III-V solar cells close to the fundamental limit  

NASA Astrophysics Data System (ADS)

A highly effective strategy of photon management is to use a back surface reflector. In this work, we present a full analytical model incorporating effects from both the modified generation function and photon recycling in GaAs solar cells with a BSR. We discuss the impact of doping concentration, non-radiative recombination, solar cell dimensions and BSR reflectivity on the efficiency, and compare the prediction of the device models to experimental data measured on GaAs devices. We use the model to predict the performance of alternative III-V materials, such as InP, comparing the predicted performance to state-of-the-art GaAs solar cells.

Lumb, Matthew P.; Steiner, Myles A.; Geisz, John F.; Walters, Robert J.

2014-03-01

199

Development of molecular beam epitaxy technology for III–V compound semiconductor heterostructure devices  

SciTech Connect

Molecular beam epitaxy (MBE) is a versatile ultrahigh vacuum technique for growing multiple epitaxial layers of semiconductor crystals with high precision. The extreme control of the MBE technique over composition variation, interface sharpness, impurity doping profiles, and epitaxial layer thickness to the atomic level makes it possible to demonstrate a wide variety of novel semiconductor structures. Since its invention nearly 40 years ago, the MBE technique has evolved from a laboratory apparatus for exploring new materials and novel devices to a favored tool for the mass production of III–V high-speed devices. This paper will review some of the past developments in this technology and propose an outlook of future developments.

Cheng, K. Y. [Department of Electrical Engineering, National Tsing Hua University, 101 Kuang Fu Road, Section 2, Hsinchu, Taiwan 30013 (China)] [Department of Electrical Engineering, National Tsing Hua University, 101 Kuang Fu Road, Section 2, Hsinchu, Taiwan 30013 (China)

2013-09-15

200

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 treatment. X-ray Photoelectron Spectroscopy has shown that the sulfur resides on the surface as a single reduced sulfur species, either as sulfide of 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.

1993-10-01

201

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

2008-07-01

202

Characterization and Application of Mev Ion Implanted Layers in Iii-V Compound Semiconductors.  

NASA Astrophysics Data System (ADS)

Ion implantation at keV energies has become a well-established technique for surface modification of solid materials, especially semiconductors. The technique of MeV ion implantation has attracted considerable attention in recent years as it provides an extension of ion implantation technique with a high potential for interface modification of solid materials and for 3-dimensional electronic device fabrication. Extending the ion energy from keV to MeV provides many advantages in terms of the great ion range for deep implantation and the minimized surface damage for modification of deeply buried layers. It also gives rise to many interesting questions about the mechanism of radiation damage and ion-radiation-induced phase transitions. A comprehensive experimental study, from the fundamental to the practical, has been undertaken to investigate MeV ion irradiation effects in III-V compound semiconductors, especially InP and GaAs, and to explore the possibility of its application to optoelectronic semiconductor device fabrication. Characterization of implanted samples has been conducted by a variety of analytical techniques, such as NRRA, CRBS, XRC, XTEM, HRTEX, SIMS, and IVC. The results have not only demonstrated the complementary nature of all these techniques but also have given clear pictures about the implant distribution, profiles and microstructures of radiation damage and lattice defects, structural phase transformation, and the build-up of lattice strain, as well as electrical property changes. They have revealed the physical relation among all of the effects and led to a better understanding of physical processes involved in MeV ion implantation into III-V compound semiconductors. It has been discovered that MeV nitrogen ion implantation can create a deeply buried high resistivity layer in n -type InP crystals, similar to the case where MeV oxygen ion implantation generates a semi-insulating layer in GaAs -AlGaAs systems. Application of this technique to the fabrication of GaAs-AlGaAs quantum well laser devices with MeV oxygen ions for the electrical isolation and carrier confinement has resulted in a device with high quantum efficiency, low current threshold, and excellent electrical characteristics. In this thesis, the experimental studies on MeV ion implanted InP and GaAs are presented. Based on the experimental results obtained, the mechanism of MeV-ion -implantation-induced damage and phase transitions in III -V compound semi-conductors is discussed in terms of electronic spikes and nuclear spikes. A mechanism for ion-implantation -induced lattice strain in III-V compound crystals is also proposed. Finally, an example of the application of MeV ion implantation to semi-conductor laser device fabrication is given.

Xiong, Fulin

203

Strain-induced spin splittings in III-V and II-VI semiconductors  

NASA Astrophysics Data System (ADS)

We have calculated the strain-induced spin splittings in III-V and II-VI semiconductors using a fourteen-band basis for a strain-dependent k .p Hamiltonian. Using deformation potentials from pseudopotential calculations we find quantitative agreement with the precessional rates observed in [1]. For GaAs, the contribution of upper-conduction-band deformation potentials to the strain-induced spin splitting is not negligible. The ratio of the strain-induced spin precession frequency to the drift velocity is similar for GaAs and InAs, but is an order of magnitude larger for GaSb and InSb. For ZnSe it is a factor of 2 smaller than GaAs. This work was supported by an ONR MURI. [1] Kato et al., Nature 427, 50 (2004).

Moehlmann, B. J.; Flatté, Michael E.

2008-03-01

204

Band-Gap Engineering by III-V Infill in Sodalite  

NASA Astrophysics Data System (ADS)

We study the structure of III-V clusters in sodalite by ab initio molecular dynamics (Car-Parrinello) and find strong bonding of the group III atoms to the oxygens of the cage with loss of tetrahedral order. The clusters introduce optically active states in the zeolite energy gap and turn it into a semiconductor with energy gap determined by its chemical nature rather than by quantum confinement. Within the local density approximation we find values of ~0.4 and ~1.9 eV for InAs and GaN clusters of the same size. We suggest that the growth of selected compounds in zeolite may lead to wide gap semiconductors for blue light emitting devices.

Trave, A.; Buda, F.; Fasolino, A.

1996-12-01

205

A study of second harmonic generation of III-V compounds grown on Si (111) substrates  

NASA Astrophysics Data System (ADS)

Optical second harmonic generation has been applied to the structure and interface study of III-V compounds. The symmetric property of the molecular beam epitaxy (MBE) grown AlN/Si(111) and GaN/AlN/Si(111) structures have been studied by measuring the rotational dependences of the polarized second harmonic generation signal under different polarized fundamental beams. These structures have also been measured by high-resolution electron energy beam diffraction, X-ray crystallography and photoluminescence spectrum for reference. Compared to the various contributions of the nonlinear response from the bulk and interfaces, we can express the interface strain as a function of the sample rotation £r. This provides another representation for the epitaxy quality and growth parameters characterization with an inexpensive method.

Chen, Jau-Shiu; Lue, Juh-Tzeng; Gwo, Shang-Jr

2003-03-01

206

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

207

Heteroepitaxial III-V on Si(100) tandem absorbers structures for photoelectrolysis  

NASA Astrophysics Data System (ADS)

Dilute nitride GaP(N,As)/Si(100) tandem absorber structures are considered for efficient direct photoelectrochemical water splitting. Both Si and GaP have already been usedfor hydrogen evolution; their monolithic integration promises sufficient voltage for bias-free photoelectrolysis and efficient use of the solar spectrum. The preparationof the III-V/Si(100) heterointerface thereby is the crucial step towards low-defect absorber structures. We study the growth of GaP/Si(100) quasi-substrates, as the template for the integration of lattice-matched dilute nitride layers, in situ during metalorganic vapor phase epitaxy. Reflection anisotropy spectroscopy provides precise control over the epitaxial surface structure during preparation enables in situ quantification of anti-phase disorder and allows optical access to the heterointerface.

Supplie, O.; Döscher, H.; May, M. M.; Hannappel, T.

2013-12-01

208

Advances in Single and Multijunction III-V Photovoltaics on Silicon for Space Power  

NASA Technical Reports Server (NTRS)

A collaborative research effort at MIT, Ohio State University and NASA has resulted in the demonstration of record quality gallium arsenide (GaAs) based single junction photovoltaic devices on silicon (Si) substrates. The ability to integrate highly efficient, radiation hard III-V based devices on silicon offers the potential for dramatic reductions in cell mass (approx.2x) and increases in cell area. Both of these improvements offer the potential for dramatic reductions in the cost of on-orbit electrical power. Recently, lattice matched InGaP/GaAs and metamorphic InGaP/InGaAs dual junction solar cells were demonstrated by MBE and OMVPE, respectively. Single junction GaAs on Si devices have been integrated into a space flight experiment (MISSES), scheduled to be launched to the International Space Station in March of 2005. I-V performance data from the GaAs/Si will be collected on-orbit and telemetered to ground stations daily. Microcracks in the GaAs epitaxial material, generated because of differences in the thermal expansion coefficient between GaAs and Si, are of concern in the widely varying thermal environment encountered in low Earth orbit. Ground based thermal life cycling (-80 C to + 80 C) equivalent to 1 year in LEO has been conducted on GaAs/Si devices with no discernable degradation in device performance, suggesting that microcracks may not limit the ability to field GaAs/Si in harsh thermal environments. Recent advances in the development and testing of III-V photovoltaic devices on Si will be presented.

Wilt, David M.; Fitzgerald, Eugene A.; Ringel, Steven A.

2005-01-01

209

Surface passivation of III–V semiconductors for future CMOS devices—Past research, present status and key issues for future  

Microsoft Academic Search

Currently, III–V metal–insulator–semiconductor field effect transistors (MISFETs) are considered to be promising device candidates for the so-called “More Moore Approach” to continue scaling CMOS transistors on the silicon platform. Strong interest also exists in III–V nanowire MISFETs as a possible candidate for a “Beyond CMOS”-type device. III–V sensors using insulator–semiconductor interfaces are good candidates for “More Moore”-type of devices on

H. Hasegawa; M. Akazawa; A. Domanowska; B. Adamowicz

2010-01-01

210

Electronic structure of amorphous III-V and II-VI compound semiconductors and their defects  

NASA Astrophysics Data System (ADS)

The local electronic structure of bulk and defect sites has been calculated for nine amorphous III-V compound semiconductors and for two amorphous II-VI compound semiconductors using the tight-binding recursion method. We find that structural disorder in a chemically ordered, tetrahedrally coordinated network causes a smoothing of the valence-band density of states, but little movement of the band edges, so that theoretically little change in the band gap is expected. Experimentally, the optical gap is found to close up and we attribute this to the presence of significant numbers of defect states at the band edges. The principal defects studied are undercoordinated atoms (``dangling bonds'') and like-atom bonds (``wrong bonds''). In all III-V compounds we find that anion dangling bonds give rise to occupied acceptorlike states at or below the valence-band edge (Ev) and that cation dangling bonds produce empty donorlike states at or above the conduction-band edge (Ec). Isolated wrong bonds are found to introduce gap states in some of the compounds; usually anion wrong bonds introduce donor states near Ec while cation wrong bonds introduce acceptor states near Ev. Overall, a much lower density of states at the Fermi level EF is expected for these compounds compared to a-Si, and this is indeed found experimentally. In the wider-gap compounds such as a-GaAs, we propose that clusters of wrong bonds are the most probable cause of mid-gap states, while in some cases like a-InP isolated cation wrong bonds may also be responsible. We argue that the dangling-bond concentration in these materials is intrinsically high, of order 1-5 and that they are the predominant defect in annealed material. We also show that stoichiometry changes produce a combination of wrong bonds and trivalent sites of the excess species. This frequently leads to an increased density of mid-gap states, but EF does not shift from mid-gap. We have also calculated the electronic structure of various hydrogen configurations and compared them to the photoemission spectra.

O'reilly, E. P.; Robertson, J.

1986-12-01

211

Growth of III-V nitrides and buffer layer investigation by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

III-V nitrides have been investigated intensively due to the enormous interest in optoelectronic device applications in the green, blue, violet, and near-ultraviolet regions. Advances in III-V nitride materials for short wavelength light sources will lead to both a revolution in optical disk storage, as higher densities can be achieved with short wavelengths, and a major impact on imaging and graphic technology as high quality red, green, and blue light-emitting diodes (LED) and lasers become available. High quality GaN films have mostly been prepared by metal-organic vapor phase epitaxy (MOCVD), molecular beam epitaxy (MBE) and vapor phase epitaxy (VPE). Compared to these techniques, pulsed laser deposition (PLD) is a relatively new growth technique used widely for the growth of oxide thin films. However, several advantages of PLD make it worthy of study as a method of growing nitrides. The congruent ablation achieved with short UV-laser pulses allows deposition of a multicomponent material by employing a single target and the ability for depositing a wide variety of materials. This advantage makes PLD very suitable for growing multilayer structures sequentially in the same chamber and investigating the effect of buffer layers. Moreover, the strong nonequilibrium growth conditions of PLD may lead to different nucleation and growth processes. In this work, GaN and (Al,Ga)N films have been epitaxially grown on (0001) sapphire substrate by PLD, which has been successfully applied to controlling the lattice constant and band gap of (Al,Ga)N. Room-temperature photoluminescence of PLD-GaN exhibits a strong band edge emission at 3.4eV. The threading dislocations of GaN are predominantly screw dislocations with Burgers vector of <0001> while edge dislocations with Burgers vector of 1/3<11-20> are the dominant ones in GaN grown by MBE, MOCVD and VPE. This variation observed in defect characteristics may come from the difference in nucleation and growth kinetics between PLD and other deposition techniques. In addition, epitaxial ZnO buffer layers with better crystalline structure and surface flatness have been developed by PLD for GaN epitaxy. The effects of ZnO buffer on GaN grown by both PLD and VPE were studied.

Huang, Tzu-Fang

1999-11-01

212

Specific Approach for Size-Control III-V Quantum/Nano LED Fabrication for Prospective White Light Source.  

National Technical Information Service (NTIS)

This research achieved a nano-structure LED to enhance the light extraction efficiency in III-V nitride LED. The Triangular lattice PC LED with diameter/periodicity of 300/500nm were patterned separately using the AAO template, E-beam lithography, and the...

H. Hwang

2007-01-01

213

Bianchi type-I, III, V, VIo and Kantowski-Sachs universes in creation-field cosmology  

NASA Astrophysics Data System (ADS)

The solutions of Einstein’s equations in the presence of a creation field have been obtained for Bianchi type-I, III, V, VIo and Kantowski-Sachs (KS) universes in the quadrature form. Some physically interesting cases have been studied in detail.

Singh, T.; Chaubey, R.

2009-05-01

214

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

215

A review on fabrication technologies for the monolithic integration of tapers with III-V semiconductor devices  

Microsoft Academic Search

The past few years a lot of effort has been put in the development and fabrication of III-V semiconductor waveguiding devices with monolithic integrated mode size converters (tapers). By integrating a taper with a waveguide device, the coupling losses and the packaging cost of OEICs in future fiber-optical networks can be much reduced. This paper gives an overview of different

Ingrid Moerman; Peter P. Van Daele; Piet M. Demeester

1997-01-01

216

Low temperature selective epitaxy of III V compounds by laser assisted chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Laser Assisted Chemical Vapor Deposition (LCVD) is a new approach for low temperature selective epitaxy of III-V compounds with great potential for maskless multicomponent device integration on the same wafer. GaAs substrates were thermally biased to temperatures as low as 250°C and exposed simultaneously to fluxes of trimethylgallium (TMG) and arsine (AsH 3). Ar ion laser scanning of the substrate, at carefully selected growth conditions, resulted in epitaxial selective deposition at rates as low as a few Å/s per scan. The LCVD growth rates as a function of deposition temperatures are reported for different laser powers and seem to follow an Arrhenius type relation. Activation energies in the range 10-13 kcal/mol were estimated for growth temperatures in the range 250-400°C. X-ray diffraction topography is demonstrated as a powerful nondestructive tool for structural characterization. We have utilized this technique to optimize the LCVD growth conditions in order to achieve device quality films that are free from lattice distortion. Low temperature photoluminescence shows the presence of impurity peaks that can be related to carbon.

Karam, N. H.; Liu, H.; Yoshida, I.; Jiang, B.-L.; Bedair, S. M.

1988-12-01

217

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

218

Exploring cryogenic focused ion beam milling as a Group III-V device fabrication tool  

NASA Astrophysics Data System (ADS)

In this paper, we compare the features observed on a Group III-V strained layer superlattice (SLS) materials system as a result of room temperature Ga+ focused ion beam (FIB) milling to the features observed as a result of cryogenic FIB (cryo-FIB) milling at -135 °C under the same beam conditions (30 kV:1 nA). The features on the cryo-FIB milled material were observed both when the material was still cold and after it returned to room temperature. Although cryo-FIB milling yielded patterned features that were initially cleaner than comparable features defined by FIB milling at room temperature, we found that both room temperature FIB milling and cryo-FIB milling with subsequent sample warm-up resulted in the formation of Group III enriched features. These findings suggest that the structural and chemical properties of features fabricated by cryo-FIB milling are temperature-dependent, which is an important consideration when it comes to device fabrication. These dependencies will need to be better understood and controlled if cryo-FIB milling is to have future applications in this area.

Dolph, Melissa Commisso; Santeufemio, Christopher

2014-06-01

219

Ion implantation for high performance III-V JFETS and HFETS  

SciTech Connect

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

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

1996-06-01

220

Interpreting interfacial structure in cross-sectional STM images of III V semiconductor heterostructures  

NASA Astrophysics Data System (ADS)

Using model GaSb-InAs heterostructures, we have systematically examined how cross-sectional scanning tunneling microscopy (XSTM) can be used for the study of III-V heterostructure interfaces. The interpretation of interfacial structure in XSTM images is impeded by the fact that only every other III or V plane as grown on the (001) substrate is seen in each image. We show how this structural artifact affects spectral analyses of interfacial roughness, preventing an accurate analysis when interfaces are just a few layers wide. Additional complications arise due to the inequivalence of the (110) and (1¯10) cleavage surfaces and the dependence of interfacial bond orientation on growth order. By taking advantage of the different bond orientations on the two cleavage surfaces, we demonstrate that the contrast observed at the interfacial layers in this system is caused primarily by the geometry of the interfacial bonds, not electronic structure differences. Finally, we illustrate how careful design of model heterostructures can be used to circumvent many limitations of XSTM, and thereby allow one to obtain detailed atomic-scale information about all the growth layers in the structure.

Nosho, B. Z.; Barvosa-Carter, W.; Yang, M. J.; Bennett, B. R.; Whitman, L. J.

2000-10-01

221

Growth mechanisms of III V compounds by atomic hydrogen-assisted epitaxy  

NASA Astrophysics Data System (ADS)

Epitaxial layers of InP and InGaAsP have been grown on (1 0 0) InP substrates by gas source molecular beam epitaxy while simultaneously exposed to an atomic hydrogen flux produced by a thermal cracker. Transmission electron microscopy and photoluminescence studies indicate improved structural and optical properties of the InGaAsP layers, while Hall effect measurements indicate no degradation in the electrical properties, as compared to layers grown by conventional epitaxy without hydrogen. This improvement is attributed to a reduction in lateral composition modulation (LCM), which develops at the surface of the InGaAsP layers during growth due to the existence of a miscibility gap. A detailed atomistic model, including surface reconstruction effects based on reflection high energy electron diffraction observations, is developed to explain the growth processes occurring on H-exposed (1 0 0) III-V surfaces. A simple rate equation model is used to understand the reduction in LCM in terms of a decreased surface diffusion length of adatoms in the presence of H.

LaPierre, R. R.; Robinson, B. J.; Thompson, D. A.

1998-07-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

223

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

224

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22234 Actions at 1.0 percent methane (I-A, I-B, III, V-A, and...

2009-07-01

225

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22234 Actions at 1.0 percent methane (I-A, I-B, III, V-A, and...

2013-07-01

226

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

227

III-V semiconductor waveguides for photonic functionality at 780 nm  

NASA Astrophysics Data System (ADS)

Photonic integrated circuits based on III-V semiconductor polarization-maintaining waveguides were designed and fabricated for the first time for application in a compact cold-atom gravimeter1,2 at an operational wavelength of 780 nm. Compared with optical fiber-based components, semiconductor waveguides achieve very compact guiding of optical signals for both passive functions, such as splitting and recombining, and for active functions, such as switching or modulation. Quantum sensors, which have enhanced sensitivity to a physical parameter as a result of their quantum nature, can be made from quantum gases of ultra-cold atoms. A cloud of ultra-cold atoms may start to exhibit quantum-mechanical properties when it is trapped and cooled using laser cooling in a magneto-optical trap, to reach milli-Kelvin temperatures. The work presented here focuses on the design and fabrication of optical devices for a quantum sensor to measure the acceleration of gravity precisely and accurately. In this case the cloud of ultra-cold atoms consists of rubidium (87Rb) atoms and the sensor exploits the hyperfine structure of the D1 transition, from an outer electronic state of 5 2S ½ to 5 2P3/2 which has an energy of 1.589 eV or 780.241 nm. The short wavelength of operation of the devices dictated stringent requirements on the Molecular Beam Epitaxy (MBE) and device fabrication in terms of anisotropy and smoothness of plasma etch processes, cross-wafer uniformities and alignment tolerances. Initial measurements of the optical loss of the polarization-maintaining waveguide, assuming Fresnel reflection losses only at the facets, suggested a loss of 8 dB cm-1, a loss coefficient, ?, of 1.9 (+/-0.3) cm-1.

Maclean, Jessica O.; Greenaway, Mark T.; Campion, Richard P.; Pyragius, Tadas; Fromhold, T. Mark; Kent, Anthony J.; Mellor, Christopher J.

2014-03-01

228

Diffraction-anomalous-fine-structure spectroscopy applied to the study of III-V strained semiconductors  

NASA Astrophysics Data System (ADS)

The effect of built-in strain on III-V epitaxial semiconductors has been investigated by extended diffraction anomalous fine structure (EDAFS) at the Ga and As K edges. A general formalism is presented for analyzing the diffraction-anomalous-fine-structure (DAFS) oscillations, valid for any type of crystallographic structure. The EDAFS spatial selectivity provides a unique tool for studying systems that are out of the reach of other x-ray techniques. We study two different systems grown on a GaAs(001) substrate: a strained layer superlattice of (GaP)2(InP)3 and three single epilayers of GaAs1-xPx (x=0.20-0.23) partially relaxed, with a different amount of residual strain. The bond distance Ga-P in the SLS is stretched by about 0.04 Å in agreement with the predictions of the elastic theory. The Ga-As and Ga-P bond lengths in GaAs1-xPx remain very close to their respective bulk values, independent of the residual strain. The GaAs1-xPx epilayers have also been measured by switching the light polarization vector from the [110] to the [11¯0] crystallographic direction. An effect is observed on the EDAFS at the Ga K edge for the most strained sample, suggesting an ordering of the P atoms in the [001] growth direction. We also point out the interest of the DAFS spectra analysis for obtaining further information about the average crystallographic structure.

Proietti, M. G.; Renevier, H.; Hodeau, J. L.; García, J.; Bérar, J. F.; Wolfers, P.

1999-02-01

229

The genetic analysis of a reciprocal translocation, eT1(III; V), in Caenorhabditis elegans.  

PubMed

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

Rosenbluth, R E; Baillie, D L

1981-01-01

230

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

231

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

232

Studies on incorporation of As 2 and As 4 in III-V compound semiconductors with two group V elements grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Under the assumption that one incident As 4 molecule produces one active As 2 molecule before incorporating into epitaxial alloys, a novel thermodynamic model is developed to describe the molecular beam epitaxy (MBE) growth of III-V compound semiconductors with two group V elements using As 4 flux. A parameter ?d representing the activation energy of As 4 dissociation process is introduced in the model. High quality InAs yP 1- y materials were grown on InP substrates using our home made all solid source MBE (SSMBE) system with valved cracker cells under different substrate temperatures and arsenic fluxes with different As 2/As 4 ratios. By taking into account the As 2/As 4 ratio, the model is used to calculate the compositions of the grown samples. The calculated results are in good agreement with the experimental data. Both the experiments and the calculations show the lower incorporation efficiency of As 4 than that of As 2.

Hao, Zhi-Biao; Ren, Zai-Yuan; Guo, Wen-Ping; Luo, Yi

2001-04-01

233

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

234

A survey of ohmic contacts to III-V compound semiconductors  

SciTech Connect

A survey of ohmic contact materials and properties to GaAs, InP, GaN will be presented along with critical issues pertaining to each semiconductor material. Au-based alloys (e.g., GeAuNi for n-type GaAs) are the most commonly used contacts for GaAs and InP materials for both n- and p-type contacts due to the excellent contact resistivity, reliability, and usefulness over a wide range of doping levels. Research into new contacting schemes for these materials has focused on addressing limitations of the conventional Au-alloys in thermal stability, propensity for spiking, poor edge definition, and new approaches for a non-alloyed contact. The alternative contacts to GaAs and InP include alloys with higher temperature stability, contacts based on solid phase regrowth, and contacts that react with the substrate to form lower bandgap semiconductors alloys at the interface. A new area of contact studies is for the wide bandgap group III-Nitride materials. At present, low resistivity ohmic contact to p-type GaN has not been obtained primarily due to the large acceptor ionization energy and the resultant difficulty in achieving high free hole concentrations at room temperature. For n-type GaN, however, significant progress has been reported with reactive Ti-based metalization schemes or the use of graded InGaN layers. The present status of these approaches will be reviewed.

Baca, A.G.; Zolper, J.C.; Briggs, R.D. [Sandia National Labs., Albuquerque, NM (United States); Ren, F. [Lucent Technologies, Murray Hill, NJ (United States); Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States)

1997-04-01

235

Gold-Free Ternary III-V Antimonide Nanowire Arrays on Silicon: Twin-Free down to the First Bilayer  

PubMed Central

With the continued maturation of III–V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III–V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal–oxide–semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1–x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires’ complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform.

2013-01-01

236

Impact of vacuum anneal at low temperature on Al2O3/In-based III-V interfaces  

NASA Astrophysics Data System (ADS)

We report on the effect of vacuum anneal on interfacial oxides formed between Al2O3 and III-V semiconductors. On InGaAs, no interfacial oxide is detected after annealing at 600 °C under UHV whereas annealing under secondary vacuum favours the regrowth of thin InGaOx interfacial oxide. Lowering the temperature at 400 °C highlights the effect of III-V substrates since In-OH bonds are only formed on InAs by OH release from TMA/H2O deposited alumina. On InGaAs, regrowth of InGaOx is observed, as a result of preferential oxidation of Ga. On InP, a transition from InPOx to POx is highlighted.

Martinez, E.; Grampeix, H.; Desplats, O.; Herrera-Gomez, A.; Ceballos-Sanchez, O.; Guerrero, J.; Yckache, K.; Martin, F.

2012-06-01

237

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

238

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

PubMed

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

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

2013-12-30

239

Bianchi type- I, III, V, VIo and Kantowski-Sachs models in scalar-tensor theories with dynamic cosmological constant  

NASA Astrophysics Data System (ADS)

The effect of a time-dependent cosmological constant is considered in a family of scalar-tensor theories. The Bianchi type I, III, V, VIo and Kantowski-Sachs models for vacuum and perfect fluid matter are found. The gravitational constant decreases with time so that these models satisfy the Dirac hypothesis. The “cosmological constant” also decreases with time, therefore it can have a very small value at the present time.

Singh, T.; Chaubey, R.

2008-12-01

240

An ultrahigh vacuum, low-energy ion-assisted deposition system for III-V semiconductor film growth  

Microsoft Academic Search

A novel ion-assisted deposition system is described in which the substrate and growing film can be bombarded with high current densities (greater than 1 mA\\/sq cm) of very low energy (10-200 eV) ions. The system design philosophy is similar to that used in III-V semiconductor molecular-beam epitaxy systems: the chamber is an all-metal ultrahigh vacuum system with liquid-nitrogen-cooled shrouds, Knudsen-cell

S. Rohde; S. A. Barnett; C.-H. Choi

1989-01-01

241

Tunnel Diode Modeling, Including Nonlocal Trap-Assisted Tunneling: A Focus on III–V Multijunction Solar Cell Simulation  

Microsoft Academic Search

Multijunction solar cells (MJCs) based on III-V semiconductors constitute the state-of-the-art approach for high-efficiency solar energy conversion. These devices, consisting of a stack of various solar cells, are interconnected by tunnel diodes. Reliable simulations of the tunnel diode behavior are still a challenge for solar cell applications. In this paper, a complete description of the model implemented in Silvaco ATLAS

Mathieu Baudrit; Carlos Algora

2010-01-01

242

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

Microsoft Academic Search

We report research activities and technical progress on the development of high-efficiency long wavelength ( 540nm) green light emitting diodes which covers whole years of the three-year program 'Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications'. The research activities were focused on the development of p-type layer that has less\\/no detrimental thermal annealing effect on as

Russell Dupuis

2007-01-01

243

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

244

III-V nitride micro- and nano-scale cantilevers for multimodal sensing applications  

NASA Astrophysics Data System (ADS)

Recent research trends in chemical and biological sensing have been geared toward developing molecular sensor devices that are fast, label free, miniaturized and portable. The performance of these devices can be dramatically improved by utilizing multimodal detection techniques, new materials and micro-/nanofabrication technologies. This is especially true for micro-/nanoscale cantilever sensors, which undergo changes in mechanical or electrical properties upon the specific binding of molecules. To develop the sensor devices with the above attributes, we utilized III-V nitride materials: InN nanowires for realizing nanoscale cantilevers and AlGaN/GaN heterostuctures with or without embedded HFETs, for developing microcantilevers. There are mainly two approaches of fabricating these sensor devices: bottom-up approach for nanocantilevers, and top-down approach for microcantilevers. InN NWs, which exhibit interesting properties such as high carrier density, superior electron mobility, strong surface charge accumulation, and chemical inertness, were synthesized using Chemical Vapor Deposition (CVD) technique by Vapor-Liquid-Solid (VLS) mechanism. The synthesis process was optimized to obtain growth direction modulation and enhanced performance of the devices, largely avoiding the complexity of nanofabrication/etching typically involved in the realization of nanoscale sensors. With dimensions much smaller than conventional cantilevers, the nanocantilevers are expected to have dramatically improved physical, chemical, and biological sensitivity for sensor applications. The piezoresistive and piezoelectric properties of AlGaN/GaN heterostructures, their wide bandgap, and chemical inertness make the microcantilevers very attractive for developing highly sensitive sensors suitable for harsh environment applications. The large variation in 2-dimensional electron gas (2DEG) at the interface with mechanical strain makes these microcantilevers much more sensitive than conventional Si based piezoresistive microcantilevers. A process was developed to fabricate free standing AlGaN/GaN microcantilevers on Si(111) substrate using various processing steps involving photolithography, GaN and through wafer Si etching, and dielectric and metal deposition. The detection performance of these cantilevers is largely improved by the utilization of a multimodal detection technique.

Quddus, Ehtesham B.

245

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

246

Time and spatially resolved studies of recombination mechanisms in III-V semiconductor films  

NASA Astrophysics Data System (ADS)

The family of III-V nitrides (GaN, InGaN, AlGaN) are currently the object of intense research due to their numerous applications, ranging from optoelectronic devices such as UV or blue-green light emitting diodes, laser diodes, and UV solar blind detectors, to high power/high temperature electronics. Many of these new devices and applications depend on the optical properties of GaN, such as the type of carriers involved in recombination and their lifetime. Carrier lifetime is critical for determining, for example, the frequency response of photoconducting detectors, the gain in bipolar transistors, and the conductivity modulation of thyristors. The lifetime is also a measure of material quality since it is directly affected by traps and recombination centers. Time-resolved photoluminescence (TRPL) spectroscopy is a powerful experimental tool to investigate carrier dynamics due to the combination of temporal and spectral information. It provides valuable scientific understanding of the materials by investigating properties such as carrier lifetimes, non-radiative processes and optical non-linearities. However, many time domain optical processes are associated with local properties of the materials such as recombination at impurity or defect locations, lifetime in quantum confined systems, local piezoelectric effects and strain, and transport to and recombination near interfaces. Thus high spatial resolution in time dependent processes is required. This work explores the use of time and spatially resolved photoluminescence experiments to elucidate recombination mechanisms on a macroscopic and microscopic scale in a variety of materials and quantum confined systems. Beginning with the presentation of the experimental instrumentation built to accommodate high temporal and spatial resolution, the dissertation goes on to apply spatially resolved TRPL to study recombination processes in GaN films and InAs self-assembled quantum dots (SAD's). Typically, epitaxial GaN is grown on lattice mismatched substrates resulting in strained films. Thick films were examined in order to minimize the influence of the strain on the fundamental physical properties of the material system. It is shown, for the first time, that the recombination mechanism in bulk GaN is dominated by radiative recombination at room temperature, and the polariton character of free exciton at 4K is confirmed. In the case of epitaxial lateral overgrown GaN, the saturation of defect levels is responsible for a two-fold increase in the free exciton lifetime. It is also shown that sub-micron resolved photoluminescence studies identify, for the first time, the hydrostatic strain in epitaxial lateral overgrown GaN and its influence on the carrier lifetime. Band filling effects were identified and carrier lifetime was measured in the case of SAD's.

Bunea, Gabriela Elena

2001-02-01

247

X-ray studies of III-V native oxide/gallium arsenide interface  

NASA Astrophysics Data System (ADS)

Three x-ray techniques have been employed to study wet-thermal native oxides of AlGaAs on GaAs. For these materials, a knowledge of the role of As at the interface is important for understanding Fermi-level pinning and is a central issue in efforts to develop high performance III-V MOSFET devices. This study is focused on how the As is incorporated at the interface, the interfacial strain, and related local structural parameters. X-ray absorption fine-structure spectroscopy (XAFS) was used to determine the site of residual As in wet-oxidized Al0.96Ga0.04As. In a ˜0.5 mum oxide film removed from its GaAs substrate, the remaining As atoms were found to be coordinated with oxygen in the form of amorphous As oxides, with a mixture of ˜80% As3+ and ˜20% As 5+ sites. These two sites are locally similar to As2O 3 and As2O5. Through this measurement, no evidence of interstitial or substitutional As, As precipitates, or GaAs was seen, implying that less than 10% of the As atoms are in these forms. To characterize the oxide structure in both the oxide film and the interfacial region, x-ray reflectivity and reflection-mode XAFS experiments were performed for a thin (300 A) oxidized AlxGa1-xAs (x = 0.96) film grown on GaAs. X-ray reflectivity studies showed that the composition of the surface oxidized film is not homogeneous as a function of depth. Reflection-mode XAFS, which uses the total external reflection of x-rays to confine an x-ray beam to the interfacial region, provided details of the local environment of As atoms at the interface of the oxide/GaAs. Analysis through this technique revealed that As atoms are in the form of mixed As oxides, with the local environment appearing to resemble As2O3 and As 2O5 in the interfacial region, which is consistent with the above observation from the isolated oxide film.

Cheong, Seong-Kyun

248

Photonic crystal active and passive device components in III-V semiconductors  

NASA Astrophysics Data System (ADS)

Photonic crystals (PC's) are emerging as potentially important candidates in propelling the development in planar photonic integrated circuits, high capacity optical fibers and nanoscopic lasers. Photonic crystals are expected to play a role analogous to that played by crystalline semiconductors in the development of electronic circuits. What makes these photonic crystals more interesting is that introducing "defects"---a missing period or phase slip, in the PC lattice introduces defect modes that lie within the bandgap of the PC. In this investigation, both two dimensional and three dimensional photonic crystals have been fabricated and studied using III-V compound semiconductors which are presently the most useful material systems for integrating with existing optoelectronic technology. A novel single step epitaxial technique to fabricate GaAs-based 3D photonic crystals with sub-micron feature size has been developed employing MBE growth on patterned substrates, ebeam and optical lithography, and lateral wet oxidation of AlGaAs. Transmission characteristics of the fabricated 3D PCs have been measured revealing a 10dB stopband centered at 1 mum for the smallest feature sizes. Electrically injected 2D photonic crystal defect microcavities were designed and fabricated to realize low threshold vertically emitting light sources. The electroluminescent devices were fabricated with GaAs- and InP-based quantum wells heterostructures with emission wavelengths at 0.94mum and 1.55 mum respectively. The light-current, spectral, near- and far-field characteristics of these devices have been studied in detail. The processing and high-aspect ratio etch techniques were carefully developed to create the 2D PCs embedded in the electrically injected apertures. Quantum dots with emission wavelength of 1.04 mum were incorporated into electrically injected 2D PC microcavities to study the electrical and optical confinement simultaneously provided in this configuration. Weak microcavity effects were observed in the fabricated devices. Passive 2D PC's with linear defects, which act as efficient waveguides to confine and channel light even around very sharp bends, have also been investigated. A novel microfluidic sensor using 2D GaAs-based photonic crystal waveguides to detect one or more fluids on the basis of their refractive index properties have been designed, fabricated and demonstrated for the first time.

Sabarinathan, Jayshri

249

Research on Nucleation of II-VI/III-V Semiconductor Heterojunctions.  

National Technical Information Service (NTIS)

Two studies were carried out in this program. The first one is molecular dynamics (MD) simulations of MBE growth of ZnSe, and the second one is the analysis of phase separation of ZnSe based alloy epilayers. One study involved molecular dynamics simulatio...

N. Otsuka R. L. Gunshor

1995-01-01

250

Alloy  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

251

Low melting metal-induced synthesis of multi-component III-V semiconducting nanowires  

Microsoft Academic Search

Semiconductor multi-component alloys provide a natural means of tuning the band gap and other parameters to optimize and extend the application of semiconductor electronic\\/optoelectronic devices. In this study, multi-component nanowires have been synthesized in vapor phase by laser ablation of solid targets consisting of initial bulk materials. Growth of nano-crystals is believed to seed from low melting metallic droplets generated

Romaneh Jalilian; Zhiqiang Chen; Gamini Sumanasekera

2008-01-01

252

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

253

Threading dislocation reduction in III-V films: Theoretical modeling and experimental methods  

NASA Astrophysics Data System (ADS)

Heteroepitaxy remains the most efficient and successful way to integrate materials with the same crystal structure but different lattice constants and optoelectronic properties. The purpose of this work is to understand the processes of strain relaxation and subsequent threading dislocation (TD) reduction through modeling and experiment. The interpretation of these data is made according to a previously published model that is based on dislocation reactions. 1,2 These reactions are the sole mechanism for threading dislocation reduction in III--V epitaxial films.3 Gallium nitride, with no available substrate even close to the lattice-matched condition, has a unique microstructure that develops as a result of initial island growth. Dislocation densities on the order of 109--10 10/cm2 are routinely measured in GaN grown on sapphire. Dislocation reduction in these hexagonal films is extremely slow, and it is shown in Chapter II that film thicknesses on the order of a substrate thickness are required to reduce threading dislocation densities to a low (10 6/cm2) level. A model is developed to treat the reduction of TDs in (0001)-oriented films that explains the non-saturating TD density in GaN. Screw dislocation behavior is shown to strongly affect the dislocation density falloff with thickness. Threading dislocation reduction in low-temperature-grown GaAs (250--350°C) and InGaAs was known to be more efficient than in high-temperature-grown GaAs (580°C). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to study the microstructure of GaAs grown on InP substrates at temperatures between 250 and 580°C to determine the mechanism by which TD reduction was enhanced. While a high level of arsenic antisite defects [ASGa] may affect the TD density at temperatures below 300°C, they do not account for the improved dislocation reduction. When dislocations are generated at high temperature, the TD density on the (111)A and (111)B planes is asymmetric. In Chapter III, it is shown that at low temperature, the TD density is symmetric between the (111)A and B planes. The symmetric distribution of TDs leads to a greater TD reaction probability and enhanced TD reduction with growth thickness. A model is developed to explain the greater TD reduction based on enhanced reaction probability. An engineering approach to reducing threading dislocation densities in compressively strained thin films makes up the remainder of the thesis. (Abstract shortened by UMI.) 1A. E. Romanov, W. Pompe, G. Beltz and J. S. Speck, Phys. Stat. Sol. B, 198, 599 (1996). 2A. E. Romanov, W. Pompe, G. Beltz and J. S. Speck, Phys. Stat. Sol. B , 199, 33 (1997). 3A. Rockett and C. J. Kiely, Phys. Rev. B, 44, 1154 (1991).

Mathis, Sheila Kathleen

254

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

255

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

Microsoft Academic Search

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

Daoxin Dai; Di Liang; John E. Bowers

2009-01-01

256

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

257

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

258

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

259

A mechanism for twin formation during Czochralski and encapsulated vertical Bridgman growth of III V compound semiconductors  

NASA Astrophysics Data System (ADS)

Conditions are derived for which nucleation in twin orientation on an "edge" facet during the Czochralski growth of semiconductors is thermodynamically favoured over nucleation in the correct orientation. The model is based on ideas presented by Voronkov [Sov. Phys.-Cryst. 19 (1975) 573] concerning the conditions necessary for the edge facets to be anchored at the three phase boundary. It is shown that the conditions are satisfied for GaAs, InP and InSb but not for Ge and Si. The main features of twinning in the III-V compounds are accounted for and predicted conditions for the avoidance of twinning are listed.

Hurle, D. T. J.

1995-02-01

260

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

261

First-principles study of the surface energy and work function of III-V semiconductor compounds  

Microsoft Academic Search

Surface energy and work function of 12 III-V semiconductors, AlP, AlAs, AlSb, AlBi, GaP, GaAs, GaSb, GaBi, InP, InAs, InSb, and InBi, on (110) surfaces are calculated using ab initio density functional theory. The obtained values are proportional to the corresponding cohesive energy and are in good agreement with available experimental data and theoretical models. The linear relationship among cohesive

W. Liu; W. T. Zheng; Q. Jiang

2007-01-01

262

Resonant spin-dependent electron coupling in a III-V/II-VI heterovalent double quantum well  

NASA Astrophysics Data System (ADS)

We report on design, fabrication, and magneto-optical studies of a III-V/II-VI hybrid structure containing a GaAs/AlGaAs/ZnSe/ZnCdMnSe double quantum well (QW). The structure design allows one to tune the QW levels into the resonance, thus facilitating penetration of the electron wave function from the diluted magnetic semiconductor ZnCdMnSe QW into the nonmagnetic GaAs QW, and vice versa. Magneto-photoluminescence studies demonstrate level anticrossing and strong intermixing resulting in a drastic renormalization of the electron effective g factor, in perfect agreement with the energy level calculations.

Toropov, A. A.; Sedova, I. V.; Sorokin, S. V.; Terent'Ev, Ya. V.; Ivchenko, E. L.; Ivanov, S. V.

2005-05-01

263

Effects of a Gaussian size distribution on the absorption spectra of III-V semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

The advancement in the fabrication of low-dimensional semiconductor structures has made it possible to grow zero-dimensional electron-hole systems called quantum dots (QDs). In recent years, there have been extensive studies on III-V semiconductor QDs. In this paper, we have formulated the absorption spectra of realistic QD systems with dot size distribution described by a Gaussian function. The dots were approximated as cubic boxes having finite potentials at the boundaries. The effects of size nonuniformity on the optical absorption spectra of few realistic QD systems were analyzed, and the results have been compared with ideal dots having infinite potentials at the boundaries.

Kumar, Subindu; Biswas, Dipankar

2007-10-01

264

A proposal of monolithicly integrated multijunction solar cells using lattice-matched II\\/VI and III\\/V semiconductors  

Microsoft Academic Search

High-efficiency multijunction solar cells are highly desirable for space and terrestrial applications. This paper proposes novel multijunction solar cell designs using lattice-matched II\\/VI (ZnCdMg)(SeTe) and III\\/V (InAlGa)(AsSb) direct bandgap materials that can be grown on GaSb or InAs substrates. Both material systems have been studied in detail separately for different applications. The combination of these lattice-matched materials uniquely offers very

Yong-Hang Zhang; Song-Nan Wu; Ding Ding; Shui-Qing Yu; Shane R. Johnson

2008-01-01

265

Continuous-wave quasi-phase-matched waveguide correlated photon pair source on a III–V chip  

SciTech Connect

We report on the demonstration of correlated photon pair generation in a quasi-phase-matched superlattice GaAs/AlGaAs waveguide using a continuous-wave pump. Our photon pair source has a low noise level and achieves a high coincidence-to-accidental ratio greater than 100, which is the highest value reported in III–V chips so far. This correlated photon pair source has the potential to be monolithically integrated with on-chip pump laser sources fabricated on the same superlattice wafer structure, enabling direct correlated/entangled photon pair production from a compact electrically powered chip.

Sarrafi, Peyman, E-mail: peyman.sarrafi@mail.utoronto.ca; Zhu, Eric Y.; Dolgaleva, Ksenia; Aitchison, J. Stewart; Qian, Li [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)] [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada); Holmes, Barry M.; Hutchings, David C. [School of Engineering, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom)] [School of Engineering, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom)

2013-12-16

266

alloys  

NASA Astrophysics Data System (ADS)

Structural, magnetic and magnetostrictive properties of Tb0.4Nd0.6(Fe0.8Co0.2) x (1.50 ? x ? 1.90) alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain technique. XRD analysis shows the presence of single Laves phase with a cubic MgCu2-type structure for the high Nd content alloy around the composition of x = 1.80, which tends to be formed by curing at relatively low annealing temperature. The easy direction of magnetization at room temperature is observed toward <111> axis, accompanied by a rhombohedral distortion with a large spontaneous magnetostriction ?111. An optimized effect on the linear anisotropic magnetostriction, 360 ppm at 3 kOe, was observed for the high Nd content Tb0.4Nd0.6(Fe0.8Co0.2)1.80 alloy, which can be attributed to its single Laves phase, the large ?111 (~1,520 ppm) of the MgCu2-type (Tb,Nd)(Fe,Co)2 phase and the good soft magnetic behaviors.

Pan, Z. B.; Liu, J. J.; Wang, R.; Liu, X. Y.; Wang, J.; Sun, N. K.; Si, P. Z.

2014-06-01

267

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

268

All-silicon and epitaxially grown III-V-on-silicon photodetectors for on-chip optical interconnection applications  

NASA Astrophysics Data System (ADS)

In this paper we review our recent progress in two complementary approaches to photodetectors on silicon photonic chips for on-chip optical interconnection applications, namely epitaxially grown III-V-on-silicon and all-silicon microcavity-enhanced photodetectors, both for the 1550nm wavelengths. On the epitaxially grown III-V-on-silicon photodetectors front, we have demonstrated both normal-incidence and waveguide-butt-coupled p-i-n photodetectors. We simulate the silicon waveguide butt-coupling to the InGaAs absorption region and estimate the absorption efficiency using a three-dimensional finite-difference time-domain method. We optimize the InGaAs absorption region in order to attain a bandwidth of 46 GHz. We also report our latest experimental demonstration of all-silicon microresonator enhanced linear-absorption photodetectors using defect-state absorption in pn-diode-integrated microresonators. Our initial experiments reveal the measured bandwidths to be exceeding 10 GHz.

Poon, Andrew W.; Feng, Shaoqi; Li, Yu; Geng, Yu; Lau, Kei May

2013-03-01

269

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

270

High-coherence semiconductor lasers based on integral high-Q resonators in hybrid Si/III-V platforms.  

PubMed

The semiconductor laser (SCL) is the principal light source powering the worldwide optical fiber network. The ever-increasing demand for data is causing the network to migrate to phase-coherent modulation formats, which place strict requirements on the temporal coherence of the light source that no longer can be met by current SCLs. This failure can be traced directly to the canonical laser design, in which photons are both generated and stored in the same, optically lossy, III-V material. This leads to an excessive and large amount of noisy spontaneous emission commingling with the laser mode, thereby degrading its coherence. High losses also decrease the amount of stored optical energy in the laser cavity, magnifying the effect of each individual spontaneous emission event on the phase of the laser field. Here, we propose a new design paradigm for the SCL. The keys to this paradigm are the deliberate removal of stored optical energy from the lossy III-V material by concentrating it in a passive, low-loss material and the incorporation of a very high-Q resonator as an integral (i.e., not externally coupled) part of the laser cavity. We demonstrate an SCL with a spectral linewidth of 18 kHz in the telecom band around 1.55 ?m, achieved using a single-mode silicon resonator with Q of 10(6). PMID:24516134

Santis, Christos Theodoros; Steger, Scott T; Vilenchik, Yaakov; Vasilyev, Arseny; Yariv, Amnon

2014-02-25

271

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

NASA Astrophysics Data System (ADS)

A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k?) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg1-xCdxTe, and In1-xGaxAsyP1-y lattice matched to InP, as example of III-V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

Dey, Anup; Maiti, Biswajit; Chanda Sarkar, Debasree

2014-04-01

272

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

PubMed Central

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

2013-01-01

273

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

PubMed

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. PMID:23633475

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

2013-06-01

274

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

275

Fully first-principles sX-LDA calculations of excited states and optical properties of III-V semiconductors  

NASA Astrophysics Data System (ADS)

III-V semiconductors are important for their extensive applications as optical devices such as laser diodes and infrared sensors. Optical properties, [?_2(?), n, k, R, and ?], of III-V semiconductors (InAs, InSb, GaSb, and AlSb), are investigated using our highly precise full-potential linearized augmented plane wave(E.Wimmer,H.Krakauer, M.Weinert, A.J.Freeman, PRB,24), 864 (1981)(FLAPW) method with the screened-exchange local density approximation( R.Asahi,W.Mannstadt, A.J.Freeman,PRB,59), 7486 (1999)(sX-LDA) solved self-consistently and with spin-orbit coupling included. The imaginary part of the dielectric constant, ?_2(?) is calculated using the longitudinal expression with full e^iqotr matrix elements, due to the nonlocality of the potential in the sX-LDA method(R.Del Sole, R.Girlanda, PRB 48), 11789 (1993). The structure of the ?_2(?)'s are analyzed with band structures and consideration of interband transitions. The result shows good agreement of the peak positions in ?_2(?) with experiment( D.E.Aspnes,A.A.Studna, PRB 27), 985 (1983) .

Hyon Rhim, Sung; Kim, Miyoung; Freeman, A. J.

2004-03-01

276

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

277

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

NASA Technical Reports Server (NTRS)

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

Wickenden, Dennis K.

2003-01-01

278

Electron-spin relaxation in bulk III-V semiconductors from a fully microscopic kinetic spin Bloch equation approach  

NASA Astrophysics Data System (ADS)

Electron spin relaxation in bulk III-V semiconductors is investigated from a fully microscopic kinetic spin Bloch equation approach where all relevant scatterings, such as, the electron-nonmagnetic-impurity, electron-phonon, electron-electron, electron-hole, and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings are explicitly included. The Elliott-Yafet mechanism is also fully incorporated. This approach offers a way toward thorough understanding of electron spin relaxation both near and far away from the equilibrium in the metallic regime. The dependences of the spin relaxation time on electron density, temperature, initial spin polarization, photo-excitation density, and hole density are studied thoroughly with the underlying physics analyzed. We find that these dependences are usually qualitatively different in the nondegenerate and degenerate regimes. In contrast to the previous investigations in the literature, we find that: (i) In n -type materials, the Elliott-Yafet mechanism is less important than the D’yakonov-Perel’ mechanism, even for the narrow band-gap semiconductors such as InSb and InAs. (ii) The density dependence of the spin relaxation time is nonmonotonic and we predict a peak in the metallic regime in both n -type and intrinsic materials. (iii) In intrinsic materials, the Bir-Aronov-Pikus mechanism is found to be negligible compared with the D’yakonov-Perel’ mechanism. We also predict a peak in the temperature dependence of spin relaxation time which is due to the nonmonotonic temperature dependence of the electron-electron Coulomb scattering in intrinsic materials with small initial spin polarization. (iv) In p -type III-V semiconductors, the Bir-Aronov-Pikus mechanism dominates spin relaxation in the low-temperature regime only when the photoexcitation density is low. When the photoexcitation density is high, the Bir-Aronov-Pikus mechanism can be comparable with the D’yakonov-Perel’ mechanism only in the moderate temperature regime roughly around the Fermi temperature of electrons, whereas for higher or lower temperature it is unimportant. The relative importance of the Bir-Aronov-Pikus mechanism decreases with the photoexcitation density and eventually becomes negligible at sufficiently high photoexcitation density. The effect of electric field on spin relaxation in n -type III-V semiconductors is also studied with behaviors very different from those in the two-dimensional case reported. Finally, we find good agreement of our calculation with the experimental results.

Jiang, J. H.; Wu, M. W.

2009-03-01

279

Heterogeneously integrated III-V/Si single mode lasers based on a MMI-ring configuration and triplet-ring reflectors  

NASA Astrophysics Data System (ADS)

In this paper we show that using a DVS-BCB adhesive bonding process compact heterogeneously integrated III-V/silicon single mode lasers can be realized. Two new designs were implemented: in a first design a multimode interferometer coupler (MMI) - ring resonator combination is used to provide a comb-like reflection spectrum, while in a second design a triplet-ring reflector design is used to obtain the same. A broadband silicon Bragg grating reflector is implemented on the other side of the cavity. The III-V optical amplifier is heterogeneously integrated on the 400nm thick silicon waveguide layer, which is compatible with high-performance modulator designs and allows for efficient coupling to a standard 220nm high index contrast silicon waveguide layer. In order to make the optical coupling efficient, both the III-V waveguide and the silicon waveguide are tapered, with a tip width of the III-V waveguide of around 500nm. The III-V thin film optical amplifier is implemented as a 3?m wide mesa etched through to the n-type InP contact layer. In this particular device implementation the amplifier section was 500?m long. mW-level waveguide coupled output power at 20°C and a side mode suppression ratio of more than 40dB is obtained.

Keyvaninia, S.; Verstuyft, S.; Lelarge, F.; Duan, G.-H.; Messaoudene, S.; Fédéli, J. M.; Geluk, E. J.; De Vries, T.; Smalbrugge, B.; Bolk, J.; Smit, M.; Van Thourhout, D.; Roelkens, G.

2013-05-01

280

High-performance III-V MOSFET with nano-stacked high-k gate dielectric and 3D fin-shaped structure.  

PubMed

A three-dimensional (3D) fin-shaped field-effect transistor structure based on III-V metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication has been demonstrated using a submicron GaAs fin as the high-mobility channel. The fin-shaped channel has a thickness-to-width ratio (TFin/WFin) equal to 1. The nano-stacked high-k Al2O3 dielectric was adopted as a gate insulator in forming a metal-oxide-semiconductor structure to suppress gate leakage. The 3D III-V MOSFET exhibits outstanding gate controllability and shows a high Ion/Ioff ratio?>?105 and a low subthreshold swing of 80 mV/decade. Compared to a conventional Schottky gate metal-semiconductor field-effect transistor or planar III-V MOSFETs, the III-V MOSFET in this work exhibits a significant performance improvement and is promising for future development of high-performance n-channel devices based on III-V materials. PMID:22853458

Chen, Szu-Hung; Liao, Wen-Shiang; Yang, Hsin-Chia; Wang, Shea-Jue; Liaw, Yue-Gie; Wang, Hao; Gu, Haoshuang; Wang, Mu-Chun

2012-01-01

281

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

282

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

283

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

NASA Technical Reports Server (NTRS)

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

Larsson, Anders G.; Maserjian, Joseph

1992-01-01

284

Au-seeded growth of vertical and in-plane III-V nanowires on graphite substrates.  

PubMed

Graphene is promising as a transparent, flexible, and possibly cost-effective substrate for nanowire-based devices. We have investigated Au-seeded III-V nanowire growth with graphite as a model substrate. The highest yield of undoped vertical nanowires was found for InAs, but we also observed vertical nanowires for the InP, GaP, and GaAs materials. The yield of vertical nanowires for GaP and GaAs was strongly improved by supplying the p-dopant DEZn before nanowire growth but not by supplying H2S or HCl. In-plane GaAs and GaP nanowire growth exhibited an unexpected behavior, where the seed particles seemingly reflected on the side facets of other nanowires. These results pave the way for vertical and in-plane hybrid graphene- nanowire devices. PMID:24592968

Wallentin, Jesper; Kriegner, Dominik; Stangl, Julian; Borgström, Magnus T

2014-04-01

285

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

286

Quantum beat phenomenon due to polariton in III-V and IV-IV semiconductors doped with quantum dot  

NASA Astrophysics Data System (ADS)

The quantum beat phenomenon due to polaritons has been studied in III-V and IV-IV band gap materials doped with a four-level atom. There is a band gap in the polariton spectrum in these semiconductors due to the coupling of photons and optical phonons. The atom is prepared in such way that it is in top two excited states and emits spontaneously two polaritons with different resonance frequencies. It is found that when the two polariton resonance frequencies lie outside the band gap the quantum beat phenomenon can be observed. On the other hand, when both or one of the resonance frequencies lie within the energy gap no quantum beat phenomenon is observed.

Singh, Mahi R.; Mukherji, D.

2003-04-01

287

Volatile products and endpoint detection in reactive ion etching of III-V compounds with a broad beam ECR source  

NASA Astrophysics Data System (ADS)

A broad beam ECR plasma source has been applied to low pressure hydrocarbon reactive ion etching of III-V compounds. An additional RF bias is applied to the sample stage providing the means for independent control of current density and bombarding energy of ions on the sample surface. Chemical aspects of the etching process have been investigated with a differentially pumped energy selective Hiden quadrupole mass spectrometer. In particular, the dominant group III volatile species in InP and GaAs have been clearly identified for the first time as In(CH 3) 2+ and Ga(CH 3) 2+, respectively. Finally, we report the application of volatile product identification to endpoint detection and demonstrate resolution for multiple layers as thin as 50 Å. These results confirm that etch uniformity over the surface area of the sample is very good for these sources.

Melville, D. L.; Budinavicius, J.; Thompson, D. A.; Simmons, J. G.

288

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

289

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

PubMed

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 ?g/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7?±?0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5?±?0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe(0) nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Mosaferi, Mohammad; Nemati, Sepideh; Khataee, Alireza; Nasseri, Simin; Hashemi, Ahmad Asl

2014-01-01

290

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

PubMed Central

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

2014-01-01

291

Real-time synchrotron x-ray studies of III-V nitride growth  

NASA Astrophysics Data System (ADS)

My thesis research has examined the atomic structure and surface morphology of the group III-nitrides and related thin films during growth using real-time synchrotron-based x-ray scattering and lab-based x-ray diffraction. The synchrotron-based surface-sensitive x-ray techniques monitor the surface evolution in real time without interruption of the process due to the non-invasive nature of x-rays. By utilizing the high brilliance of synchrotron radiation, x-ray measurements can overcome a number of the difficulties encountered in traditional electron-based and scanning techniques, providing important complementary information on surface topography evolution, film nucleation and strain relaxation. A unique ultra-high vacuum growth chamber for these experiments was designed and constructed by our group. I have set up and optimized the system for thin film growth by molecular beam epitaxy. The real-time x-ray studies facility consists of a base diffractometer and an ultra-high vacuum chamber with processing and analysis instrumentation. Understanding how heteroepitaxial thin film nucleation and initial growth occurs in the presence of mismatch strain is an issue of widespread significance in materials physics. My thesis presents detailed studies of the plasma nitridation of c-plane sapphire at low and high substrate temperatures, which converts the sapphire surface to relaxed AIN. Models of the film nucleation and growth were developed to explain the experimental results. Surface morphology evolution during continued thin film growth is a complex issue, involving stochastic deposition kinetics and surface diffusion. My thesis research has studied the surface morphology evolution during GaN growth by migration-enhanced molecular beam epitaxy which utilizes alternative supplies of Ga and N sources to achieve atomic flat surface and large area uniformity. Subsequent formation of self-organized GaN nanodots by droplet heteroepitaxy and plasma nitridation has also been studied, as has the kinetics of Ga nanodroplet formation and evaporation on substrate surfaces. Finally I have investigated ordering in group III-nitride films, a complex phenomenon believed to be driven by processes at the growing surface, possibly influenced by strain. My thesis describes our observation of a new incommensurate ordering along the [0001] direction in wurtzite Al0.72Ga0.28 N alloys grown by plasma-assisted molecular beam epitaxy on c-plane sapphire.

Wang, Yiyi

292

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

293

Alloys  

NASA Astrophysics Data System (ADS)

The effects of mechanical deformation and subsequent annealing on the thermoelectric properties and microstructure have been investigated for p-type (Bi0.25Sb0.75)2Te3 alloys prepared by melting followed by quenching. The mechanically deformed pellets were prepared by repetition of cold-pressing of quenched samples at room temperature. Cold-pressed pellets were then annealed at 300°C in vacuum, and the thermoelectric properties and microstructure were traced through the course of the heat treatment. For the heavily deformed samples, the Seebeck coefficient rapidly increased at the very early stage of annealing and did not change as the annealing time increased, due to recrystallization of a new ?-phase which equilibrated at the annealing temperature of 300°C (?300-phase). At the initial stage of annealing (recovery stage), the electrical resistivity sharply increased, probably due to the interaction of antistructural defects with vacancies produced during the cold-pressing treatment. However, for the lightly deformed samples, recrystallization occurred only at some portion of the grain boundaries, and the newly generated ?300-phase slowly replaced the original, as-solidified ?ingot-phase.

Jung, Sung-Jin; Kim, Seong Keun; Park, Hyung-Ho; Hyun, Dow-Bin; Baek, Seung-Hyub; Kim, Jin-Sang

2014-06-01

294

Basic studies of III-V high-efficiency cell components: Annual subcontract report, 15 August 1985-14 August 1986  

SciTech Connect

This report documents research on the fabrication and photovoltaic characterization of the basic building blocks of III-V cells: the pn junction, the pn heterojunction, the isotype (p-p and n-n) heterojunction, and graded-gap semiconductors. The goal of the project is to maximize cell performance by characterizing the electrical properties of high-efficiency cell components. Other goals are to demonstrate new cell structures fabricated by molecular beam epitaxy (MBE), develop measurement techniques, and characterize methodologies. This work should help identify paths toward higher efficiency III-V cells.

Lundstrom, M S; Melloch, M R; Kyono, C S; McMahon, C P; Noren, R E; Rancour, D P

1987-03-01

295

Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds  

SciTech Connect

To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of l-InAs was investigated using the synchrotron x-ray diffraction and an ab initio molecular-dynamics simulation (AIMD). The x-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9 GPa. Corresponding to this change, the coordination number (China), which is maintained up to 9 GPa, markedly increases from 6.0 to 7.5. The AIMD simulation revealed that this change is related to the change in the pressure dependence of all three pair correlations. In particular, a marked change is observed in the As-As correlation; in the low-pressure region, the position of the first peak in g{sub AsAs}(r), r{sub AsAs}, increases while maintaining the CN{sub AsAs}, but in the high-pressure region, the r{sub AsAs} stops increasing and the CN{sub AsAs} begins to increase. The AIMD simulation also revealed that each partial structure of l-InAs is similar to that for the pure-element liquid with the same valence electron number. Upon compression, each partial structure approaches the respective one for a heavier element in the same group. These findings suggest that the structures of liquid compounds are locally controlled by the number of the valence electrons in each ion pair and that the change in each partial structure obeys the empirical rule that the high-pressure state resembles the ambient state of a heavier element in the same group. Comparing the pressure-induced structural change of l-InAs to those of other liquid III-V compounds (GaSb and InSb) has revealed that, although the high-pressure behaviors of these three liquids are apparently different, their structural changes are systematically understood by a common structural sequence. This systematics originates from the same effect on each partial structure between increasing the atomic number and the pressurization.

Hattori, T.; Tsuji, K.; Miyata, Y.; Sugahara, T.; Shimojo, F. [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Kouto, Sayo, Hyogo 679-5148 (Japan); Department of Physics, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan)

2007-10-01

296

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

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Main fans (I-A, I-B, I-C, II-A, III...Mines Ventilation § 57.22202 Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). (a) Main fans shall beâ (1) Installed on the...

2009-07-01

297

Development of Ultra-Low Noise, High Performance III-V Quantum Well Infrared Photodetectors (QWIPs) for Focal Plane Array Staring Image Sensor Systems.  

National Technical Information Service (NTIS)

During this reporting period (02-01-94 to 04-30-94) we have continued to make excellent progress. We report two new normal incidence p-type strained-layer III-V quantun well infrared photodetectors (QWIPs) for 3-5 and 8-14 um detection. An ultra-low dark ...

S. S. Li

1994-01-01

298

High-brightness blue-green LEDs and first III-V nitride-based laser diodes  

NASA Astrophysics Data System (ADS)

InGaN single-quantum-well-structure (SQW) light-emitting diodes (LEDs) with an emission wavelength between violet and orange were fabricated. The maximum on-axis luminous intensity of green LEDs was 12 cd and the output power was as high as 3 mW at a forward current of 20 mA, while those of blue LEDs were 2 cd and 5 mW, respectively. The peak wavelength and the full width at half-maximum of the green LEDs were 525 nm and 30 nm, respectively, while those of blue LEDs were 450 nm and 20 nm, respectively. Successfully, InGaN multi-quantum-well (MQW) structure laser diodes were fabricated from III-V nitride materials for the first time. The laser consisted of a InGaN MQW, GaN optical guiding layers and AlGaN cladding layers. The observed stimulated emission was at a wavelength around 420 nm, with a threshold current of 610 mA (8.7 kA/cm2) and a threshold voltage of 21 V under pulsed current injection at room temperature. The stimulated emission also showed a strong transverse electric polarization. The beam full widths at half power for the parallel and perpendicular far-field radiation patterns were 5 and 17 degrees, respectively.

Nakamura, Shuji

1996-05-01

299

Study of Metal Organic Chemical Vapour Deposition (MOCVD) semiconductors III-V hyperstructures with Secondary Ion Mass Spectrometry (SIMS)  

NASA Astrophysics Data System (ADS)

One of the most promising technologies in high efficiency solar cells is based on quaternary structures grown by epitaxial techniques as Metal Organic Chemical Vapour deposition (MOCVD). The semiconductors III-V structures are elaborated under tailored parameters, allowing the use of a broader area of the solar spectrum. Analytical techniques capable of providing accurate and precise information in cross sections about the composition and thickness of the layers are demanded. Secondary Ion Mass Spectrometry (SIMS) has been used for characterization of these structures due to its high depth resolution and sensitivity, stability and reproducibility. It was detected the diffusion process of Al and In across the cell interfaces and the layer diffusion over GaAs substrates. The Al diffusion was associated at incorrect incorporation of elements during growth process and the layer diffusion was associated at changes of manufacturing parameters. Such studies show the SIMS ability to diagnose of faults during the growth process, detection of impurities and incorrect diffusion of dopants that may affect the layer properties and the structure functionality.

Laserna, J. J.; Téllez Lozano, H.; Vadillo, José M.; Padilla, D.

2014-06-01

300

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

2012-03-01

301

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

302

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

SciTech Connect

Secondary-ion emission from III-V semiconductive chemical compounds (InP, InAs, and InSb) has been experimentally studied at heavy-ion energies from 0.5 to 5.0 MeV, 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 S{sub e}{sup -1}, where S{sub e} 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 SiO{sub 2}. 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 [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

2004-10-01

303

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

304

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

NASA Astrophysics Data System (ADS)

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

Torfi, Amin

305

The role of vicinal silicon surfaces in the formation of epitaxial twins during the growth of III-V thin films  

NASA Astrophysics Data System (ADS)

We examine the role of vicinal surface steps in the formation and propagation of twins during the growth of epitaxial III-V thin films (GaAs, InP, GaSb, AlSb) on silicon substrates. This is achieved through the combined use of two-dimensional X-ray diffraction and conventional transmission electron microscopy techniques, which allow for both a macro and nano/micro characterization of the material systems. Observed is a systematic suppression of twins formed opposite to the tilt direction of vicinal substrates through a process of step-flow overgrowth of nucleated twins, and an enhancement of twins toward the tilt direction when the fastest growth planes are aligned with the step-flow. These results indicate a probable path to the enhancement of the electronic mobility of lateral devices based on III-V semiconductors on silicon.

Devenyi, G. A.; Woo, S. Y.; Ghanad-Tavakoli, S.; Hughes, R. A.; Kleiman, R. N.; Botton, G. A.; Preston, J. S.

2011-12-01

306

Theory of excitons in cubic III-V semiconductor GaAs, InAs and GaN quantum dots: Fine structure and spin relaxation  

Microsoft Academic Search

Exciton fine structures in cubic III-V semiconductor GaAs, InAs and GaN quantum dots are investigated systematically and the exciton spin relaxation in GaN quantum dots is calculated by first setting up the effective exciton Hamiltonian. The electron-hole exchange interaction Hamiltonian, which consists of the long- and short-range parts, is derived within the effective-mass approximation by taking into account the conduction,

H. Tong; M. W. Wu

2011-01-01

307

First-principles pseudopotential study of the phase stability of the III-V semiconductors GaAs and AlAs  

Microsoft Academic Search

A first-principles pseudopotential study of the phase stability of the III-V semiconductors GaAs and AlAs is reported. For both compounds we study the zinc-blende, wurtzite, NaCl, CsCl, beta-tin, NiAs, and sc16 structures, the latter being the binary analog of the metastable bc8 structure observed in Si and Ge. For GaAs we have also considered a structure of orthorhombic symmetry with

A. Mujica; R. J. Needs; A. Muñoz

1995-01-01

308

Si(100) versus Ge(100): Watching the interface formation for the growth of III-V-based solar cells on abundant substrates  

Microsoft Academic Search

We investigated the atomic surface properties of differently prepared silicon and germanium (100) surfaces during metal-organic vapour phase epitaxy\\/chemical vapour deposition (MOVPE\\/MOCVD), in particular the impact of the MOVPE ambient, and applied reflectance anisotropy\\/difference spectroscopy (RAS\\/RDS) in our MOVPE reactor to in-situ watch and control the preparation on the atomic length scale for subsequent III-V-nucleation. The technological interest in the

S. Bruckner; O. Supplie; E. Barrigon; P. Kleinschmidt; A. Dobrich; I. Rey-Stolle; C. Algora; H. Doscher; T. Hannappel

2011-01-01

309

Sulfide passivation of III-V semiconductor surfaces: role of the sulfur ionic charge and of the reaction potential of the solution  

Microsoft Academic Search

A model is proposed for describing the effect of a solution on the electronic properties of sulfided surfaces of III-V semiconductors\\u000a which treats the adsorption of sulfur in terms of a Lewis oxide-base interaction. According to this model, the density of\\u000a states on a sulfided surface, which pin the Fermi level, decreases as the global hardness of the electron shell

V. N. Bessolov; Yu. V. Zhilyaev; E. V. Konenkova; M. V. Lebedev

1998-01-01

310

Measurement and comparison of 1\\/f noise and g-r noise in silicon homojunction and III-V heterojunction bipolar transistors  

Microsoft Academic Search

This paper experimentally determines and compares the 1\\/f noise and the g-r noise, as components of the base noise current spectral density, in Si homojunction and III-V heterojunction bipolar transistors (HBTs) in common-emitter configuration. The noise spectra for each of these devices are obtained as functions of the base bias current (IB), and the 1\\/f noise has been found to

Ashish K. Kirtania; Mukunda B. Das; S. Chandrasekhar; Leda M. Lunardi; G.J. Qua; R. A. Hamm; Li-Wu Yang

1996-01-01

311

The FUSE Spectra of two WC4+O5-6 III-V binaries in the LMC  

NASA Astrophysics Data System (ADS)

O stars are the most massive of the main-sequence stars. Wolf-Rayet (WR) stars are evolved O stars that have lost most or all of their hydrogen. Both emit stellar winds with very high terminal velocity and very high density. The mass loss for these stars is then also very high, and that affects profoundly their evolution. Such strong winds also have impacts on the local interstellar medium by pushing it and by increasing its metallicity. For all these reasons, it is of the greatest interest to better know the properties of these winds. One of the best ways to do it is to study the wind-wind collision in a O+WR binary system. Such a collision leads to the formation of a cone-shaped shock surface around the star having the wind with the lowest momentum. This cone spins with the orbital motion, which induces variations in the binary spectrum with phase. These variations allow deducing a lot of information about the geometry of the shock cone and about the winds of both stars. My project is on two WR+O binaries in the Large Magellanic Cloud (LMC): Br22 and Br32. These two systems have almost identical spectral types (WC4+O5-6 III-V), but have periods of respectively 14.9 and 1.9 days. This great similitude makes them very interesting to study in parallel. Also, both systems have been intensively studied in the optical spectrum recently (Bartzakos 2001). My work is to complement this latter work by studying the far ultraviolet portion of the spectra, obtained at different phases with the Far Ultraviolet Spectroscopic Explorer (FUSE), a satellite spectroscopic telescope. The strongest lines in this portion is Ovi_1032-1037 (Ovi is only observable with FUSE) and Ciii_1175. I fitted these lines with a program made by Sergey Marchenko. This code accounts for the orbital geometry of the stars and the cone, the atmospheric eclipses, and the extra emission produced by the shock region. With that, I have been able to put constraints on many parameters of the stellar winds in Br22 and Br32.

Boisvert, Philippe; Marchenko, S. V.; St-Louis, N.; Moffat, A. F. J.

2005-08-01

312

Lattice Matched Iii-V IV Semiconductor Heterostructures: Metalorganic Chemical Vapor Deposition and Remote Plasma Enhanced Chemical Vapor Deposition.  

NASA Astrophysics Data System (ADS)

This thesis describes the growth and characterization of wide gap III-V compound semiconductors such as aluminum gallium arsenide (Al_{rm x} Ga_{rm 1-x}As), gallium nitride (GaN), and gallium phosphide (GaP), deposited by the metalorganic chemical vapor deposition (MOCVD) and remote plasma enhanced chemical vapor deposition (Remote PECVD). In the first part of the thesis, the optimization of GaAs and Al_{rm x}Ga _{rm 1-x}As hetero -epitaxial layers on Ge substrates is described in the context of the application in the construction of cascade solar cells. The emphasis on this study is on the trade-offs in the choice of the temperature related to increasing interdiffusion/autodoping and increasing perfection of the epilayer with increasing temperature. The structural, chemical, optical, and electrical properties of the heterostructures are characterized by x-ray rocking curve measurement, scanning electron microscopy (SEM), electron beam induced current (EBIC), cross-sectional transmission electron microscopy (X-TEM), Raman spectroscopy, secondary ion mass spectrometry (SIMS), and steady-state and time-resolved photoluminescence (PL). Based on the results of this work the optimum growth temperature is 720^circC. The second part of the thesis describes the growth of GaN and GaP layers on silicon and sapphire substrates and the homoepitaxy of GaP by remote PECVD. I have designed and built an ultra high vacuum (UHV) deposition system which includes: the gas supply system, the pumping system, the deposition chamber, the load-lock chamber, and the waste disposal system. The work on the deposition of GaN on Si and sapphire focuses onto the understanding of the growth kinetics. In addition, Auger electron spectroscopy (AES) for surface analysis, x-ray diffraction methods and microscopic analyses using SEM and TEM for structural characterization, infrared (IR) and ultraviolet (UV) absorption measurements for optical characterization, and electrical characterization results on the GaN films are presented. In the deposition GaP thin films by remote PECVD, trimethylgallium and in-situ generated phosphine precursors are employed as source gases which permits homo- and heteroepitaxial growth as substrate temperature of 590-620^ circC. Also, the growth kinetics of gallium phosphide is discussed. As in the case of GaN, the surface, structural, chemical, optical, and electrical properties are characterized and the results are discussed.

Choi, Sungwoo

1992-01-01

313

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

314

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

NASA Astrophysics Data System (ADS)

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 the CMOS scaling up to and beyond the 16-nm technology node. AlGaN/GaN heterostructure is useful in a MOS-high electron mobility transistor (MOS-HEMT) device for providing a high current-carrying two dimensional electron gas (2DEG) channel. The interaction of GaAs surface with atomic layer deposition of high- k dielectrics was investigated to gain fundamental insights into the chemical properties of GaAs surface oxides and high-k/GaAs interface. Electrical characterization of devices was performed to understand the impact of high-k/GaAs interface on MOS device characteristics in order to form a suitable metal/high-k/GaAs gatestack for future high-speed logic and power devices. Reduction of native oxides on GaAs was found to occur during atomic layer deposition (ALD) of high-k dielectrics- HfO2 and Al2O3/HfO 2 nanolaminates on GaAs. Reaction between ALD metal precursor and native oxides on GaAs was identified to be the cause for consumption of native oxides. It was established that the ALD growth temperature has a strong impact on this phenomenon. During post-dielectric annealing the residual arsenic oxides at the interface decomposed leading to an increase in the interfacial gallium oxides. Presence of gallium oxide, Ga2O3 was identified as a cause for observed frequency dispersion in MOS capacitance-voltage curves indicative of a high interface state density. The chemical properties of the AlGaN/GaN heterostructure surface prepared by wet chemical treatment using HCl/HF and NH4OH solutions were investigated and compared. Both HCl and NH4OH solutions were effective in etching the native oxide layer and reducing the surface carbon content; HCl treatment being slightly more effective. Atomic layer deposition of Al 2O3 on AlGaN/GaN surface revealed a reduction of surface gallium oxides due to the reaction between metal precursor and Ga2O 3. This oxide reduction provides an in-situ ALD surface cleaning action and provides a passivation effect useful for suppressing surface states. The interface and electrical properties of Al2O3 and SiO 2 grown by ALD on HCl-treated AlGaN/GaN surface were investigated. An upward band bending in the semiconductor was observed; Al2O 3 resulting in a greater band bending at the interface than SiO2. SiO2 based device yielded a more positive threshold voltage than Al2O 3 suggesting the potential use of a thin SiO2 interface passivation layer to achieve enhancement mode operation. Energy band alignment of ALD dielectrics- SiO2, HfO2, HfAlO and Al2O 3 on GaN was determined using x-ray photoelectron spectroscopy. Fundamental chemical properties of the AlGaN/GaN heterostructure surfaces, interaction of the AlGaN/GaN surfaces with atomic layer deposition of dielectrics and electrical properties of AlGaN/GaN based MOS devices were studied and are the key to improving the device performance of MOS-HEMT transistors for high-power applications.

Suri, Rahul

315

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

316

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

PubMed

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

Kazior, Thomas E

2014-03-28

317

Comparison of dry etching techniques for III-V semiconductors in CH{sub 4}/H{sub 2}/Ar plasmas  

SciTech Connect

Dry etching of III-V semiconductors under reactive ion etching, magnetron, or electron cyclotron resonance (ECR) conditions has been performed in the same reactor using the CH{sub 4}/H{sub 2}/Ar plasma chemistry. The use of ECR conditions with additional RF-biasing provides the fastest etch rates, although this produces rough surface morphologies for InP. Materials such as GaAs, AlGaAs, and GaP display smooth, stoichiometric surfaces even at the highest ECR powers employed. The etching is limited by sputter-induced desorption of the etch products for all of the III-Vs investigated.

Pearton, S.J.; Lee, J.W.; Lambers, E.S.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States); Ren, F.; Hobson, W.S. [AT and T Bell Labs., Murray Hill, NJ (United States); Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States)

1996-02-01

318

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

319

Selective area growth of III-V nanowires and their heterostructures on silicon in a nanotube template: towards monolithic integration of nano-devices.  

PubMed

We demonstrate a catalyst-free growth technique to directly integrate III-V semiconducting nanowires on silicon using selective area epitaxy within a nanotube template. The nanotube template is selectively filled by homo- as well as heteroepitaxial growth of nanowires with the morphology entirely defined by the template geometry. To demonstrate the method single-crystalline InAs wires on Si as well as InAs-InSb axial heterostructure nanowires are grown within the template. The achieved heterointerface is very sharp and confined within 5-6 atomic planes which constitutes a primary advantage of this technique. Compared to metal-catalyzed or self-catalyzed nanowire growth processes, the nanotube template approach does not suffer from the often observed intermixing of (hetero-) interfaces and non-intentional core-shell formation. The sequential deposition of different material layers within a nanotube template can therefore serve as a general monolithic integration path for III-V based electronic and optoelectronic devices on silicon. PMID:23637047

Kanungo, Pratyush Das; Schmid, Heinz; Björk, Mikael T; Gignac, Lynne M; Breslin, Chris; Bruley, John; Bessire, Cedric D; Riel, Heike

2013-06-01

320

Selective area growth of III-V nanowires and their heterostructures on silicon in a nanotube template: towards monolithic integration of nano-devices  

NASA Astrophysics Data System (ADS)

We demonstrate a catalyst-free growth technique to directly integrate III-V semiconducting nanowires on silicon using selective area epitaxy within a nanotube template. The nanotube template is selectively filled by homo- as well as heteroepitaxial growth of nanowires with the morphology entirely defined by the template geometry. To demonstrate the method single-crystalline InAs wires on Si as well as InAs-InSb axial heterostructure nanowires are grown within the template. The achieved heterointerface is very sharp and confined within 5-6 atomic planes which constitutes a primary advantage of this technique. Compared to metal-catalyzed or self-catalyzed nanowire growth processes, the nanotube template approach does not suffer from the often observed intermixing of (hetero-) interfaces and non-intentional core-shell formation. The sequential deposition of different material layers within a nanotube template can therefore serve as a general monolithic integration path for III-V based electronic and optoelectronic devices on silicon.

Das Kanungo, Pratyush; Schmid, Heinz; Björk, Mikael T.; Gignac, Lynne M.; Breslin, Chris; Bruley, John; Bessire, Cedric D.; Riel, Heike

2013-06-01

321

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

SciTech Connect

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

NONE

1998-06-01

322

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

323

X-ray reflectivity and reflection-mode XAFS study of III-V compound native oxide/GaAs interfaces  

NASA Astrophysics Data System (ADS)

We have performed x-ray reflectivity and reflection mode XAFS experiments at the MRCAT undulator beamline at the Advanced Photon Source (APS). In these experiments, fluorescence-mode XAFS has been used to study the local environment about Ga and As in both an oxidized thin film and at the interface between a thin (300 Åoxidized AlAs layer and the GaAs substrate. For the interface study, the measurements were performed in a reflection-mode geometry. X-ray reflectivity data was also obtained to study the oxide film on a GaAs substrate, determining structural properties such as thickness, roughness and density. We are interested in determining how the As is incorporated at the interface, the interfacial strain, and related structural parameters; this information may be central to developing high performance III-V MOSFET devices.

Cheong, Seong-Kyun; Shibata, Tomohiro; Boyanov, Maxim; Lahiri, Debdutta; Bunker, Bruce A.; Hall, Douglas C.; Snider, Gregory L.

2000-03-01

324

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

325

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

326

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

327

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

NASA Technical Reports Server (NTRS)

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

Kim, J. S.

1978-01-01

328

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

NASA Astrophysics Data System (ADS)

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

Manciu, Felicia Speranta

329

Epitaxial lift-off of II-VI semiconductors from III-V substrates using a MgS release layer  

NASA Astrophysics Data System (ADS)

Epitaxial lift-off (ELO) is a post-growth process that allows an epitaxial layer to be removed from its original substrate and transferred to a new one. ELO has previously been successfully demonstrated for III-V materials and also ZnSe based II-VI semiconductors using a MgS sacrificial layer. Following the recent successful growth of epitaxial MgS layers on GaP and InP substrates, in this paper we compare ELO of II-VI epilayers grown on GaP, GaAs, and InP substrates using MgS sacrificial layers in the range of 7-15 nm thick. Good quality lifted layers are obtained rapidly from InP and GaAs substrates. For GaP substrates, ELO is much slower and good quality lifts have only been achieved with ZnSe epilayers. Photoluminescence spectra obtained from epitaxial layers before and after ELO show changes in peak positions, which are compatible with changes of strain in the layer. The layers produced by ELO are flat and free of cracks, suggesting that this is an efficient and convenient method for the transfer of II-VI epitaxial layers to other substrates.

Rajan, Akhil; Davidson, Ian A.; Moug, Richard T.; Prior, Kevin A.

2013-12-01

330

Theoretical modeling and optimization of III-V GaInP/GaAs/Ge monolithic triple-junction solar cells  

NASA Astrophysics Data System (ADS)

We design and optimize monolithic III-V GaInP/GaAs/Ge triple-junction (TJ) solar cells by using a commercial software Silvaco ATLAS simulator to obtain the maximum short-circuit current density J sc . The maximum J sc , which is a current matching value between the GaInP top and GaAs middle subcells, can be determined by varying the base thicknesses of the GaInP top and GaAs middle subcells. From the numerical simulation results, a matched maximum J sc value of 13.92 mA/cm2 is obtained at base thicknesses of 0.57 ?m and 3 ?m for the GaInP top and GaAs middle subcells, respectively, under 1-sun air mass 1.5 global spectrum illumination, leading to a high power conversion efficiency of 30.72%. The open-circuit voltage and the fill factor are 2.55 V and 86.55%, respectively. For the optimized cell structure, the external quantum efficiency and the photogeneration rate distributions are also investigated. To obtain efficient antireflection coatings (ARCs), we perform optical reflectance calculations by using a rigorous coupled-wave analysis method. For this, a silicon oxide/titanium oxide double-layer is used as an ARC on the TJ solar cell.

Leem, Jung Woo; Yu, Jae Su; Kim, Jong Nam; Noh, Sam Kyu

2014-05-01

331

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

PubMed

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

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

2014-03-10

332

Structural properties of bismuth-bearing semiconductor alloys  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

333

Solvothermal syntheses, crystal structures, and properties of new mercury(II)-thioantimonates(III) and a mixed-valent thioantimonate(III,V)  

NASA Astrophysics Data System (ADS)

New heterometallic thioantimonates(III) [Co(dien)2]HgSb2S5 (1), [Ni(dien)2]HgSb2S5 (2) and [H2dien]HgSb8S14 (3), and a mixed-valent thioantimonate(III,V) [Co(dien)2]2Sb4S9 (4) were solvothermally prepared in diethylenetriamine (dien) solvent from Co(Ni)-Hg-Sb-S, Hg-Sb-S and Co-Sb-S systems, respectively. In 1 and 2, the bimeric subunit Sb2S5 condenses with HgS4 tetrahedron via sharing common S atoms to form an one-dimensional [HgSb2S5]n2n- chain, in which a new ?3-1?2S1,S5:2?S2:3?S4 bridging mode of the Sb2S5 subunit is obtained. In 3, four SbS3 trigonal pyramids and a linear HgS2 unit condense via sharing S atoms to generate an one-dimensional double-lined [HgSb8S14] n2n- chain. In 4, three SbIIIS3 pyramids and a SbVS4 tetrahedron share common corners to form an one-dimensional mixed-valent [Sb4S9]n4n- anion. The syntheses of 1-4 demonstrated that the Hg2+ ion is easily incorporated into thioantimonate networks, and has a higher affinity to S than that of transition metals. 1-4 exhibit semiconducting properties with optical band gaps in 2.0-2.4 eV.

Tang, Weiwei; Tang, Chunying; Wang, Fang; Chen, Ruihong; Zhang, Yong; Jia, Dingxian

2013-03-01

334

Are there predictive factors for the outcome of endoscopic treatment of grade III-V vesicoureteral reflux with dextranomer/hyaluronic acid in children?  

PubMed

Dextranomer/hyaluronic acid (Dx/HA) copolymer has been used widely for the treatment of vesicoureteral reflux (VUR) in children since 2001. However, the factors that influence the outcome of injection therapy with Dx/HA have remained unclear. In this study, we retrospectively evaluated the outcomes in 101 consecutive children to determine the cure and to identify the factors that can impact treatment outcomes of Dx/HA injection. Endoscopic treatment with Dx/HA was performed in 133 ureters, in 101 patients with grade III-V VUR. Of the patients, 68 (67.3%) were girls and the mean age was 6.5 years. Before and after the treatment, the presence and grades of VUR were determined by voiding cystourethrograms. The patients' age, gender, laterality, preoperative reflux grade, ureteral duplication, morphology of ureteral orifice, renal hypoplasia and experience with surgery were assessed as predictive factors related to the success rates of Dx/HA injection therapy. The cure rates were 54.8% after the first injection, 66.9% after the second and 73.6% after the third injection. Patients with a high grade (grade IV or V), duplicated system, golf hole-shaped orifice and renal hypoplasia had significantly lower cure rates (P<0.05). Experience with the technique also correlated with the positive outcome of the procedure. New contralateral vesicoureteral reflux developed in five (7.2%) patients with unilateral VUR, and all of them resolved spontaneously during the first year of followup. No treatment-related significant complication was encountered. Although, endoscopic treatment of VUR with Dx/HA provides a high rate of success in children with medium or high grade VUR, treatment failure may be seen in some patients. However, we showed that endoscopic treatment with Dx/HA was effective in selected patients with grade V VUR, and we emphasize the need for further large-scale studies to confirm our findings. PMID:17356857

Altug, Ugur; Cakan, Murat; Yilmaz, Sevgin; Yalçinkaya, Fatih

2007-06-01

335

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

336

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

NASA Astrophysics Data System (ADS)

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 moments, , of orders n=-1, 1, 2, and 4. Notwithstanding the obvious differences in concrete shapes of spectra presented for one and the same material by different authors, the respective magnitudes of estimated moments have been found in most cases to be nearly the same (to within uncertainties of some few percent). For most materials under study, the average phonon temperatures of the lower and upper sections of PDOS spectra, ?L and ?U, are found to be by factors of order 0.6 lower or 1.4 higher, respectively, than the average phonon temperature, ?P, of the total PDOS spectra. The estimated high-temperature limits of Debye temperatures, ?D(?), are found to be significantly higher (by factors of order 1.4) than ?P, implying an order-of-magnitude equality, ?D(?)~?U (within differences not exceeding an order of +/-10%, for all materials under study). The phonon temperatures, ?g, that are effective in controlling the observable temperature dependences of fundamental energy gaps, Eg(T), are found to be usually of the same order as the respective average phonon temperatures, ?g~?P. The existing differences between these two qualitatively different types of characteristic phonon temperatures are seen to be limited, for diamond, 3C-SiC, Si, Ge, AlN, GaN, GaP, GaAs, GaSb, InP, InSb, ZnS, ZnSe, ZnTe, and CdTe, to an order of +/-12%. We design an exemplary way for precalculating harmonic parts of isochoric heat capacities on the basis of the estimated quadruplets of PDOS spectra moments. This novel calculation scheme is exemplified for silicon and germanium.

Pässler, Roland

2007-05-01

337

III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers  

NASA Astrophysics Data System (ADS)

This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further experimentally prove the importance of interface roughness on intersubband scattering by measuring the electron transit time of different quantum cascade lasers and comparing them to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when the interface roughness scattering is included. Lastly, we study the effect of growth asymmetry on scattering mechanisms in mid-infrared Quantum Cascade lasers. Due to the dopant migration of around 10 nm along the growth direction of InGaAs/InAlAs Quantum Cascade laser structures, ionized impurity scattering is found to have a non-negligible influence on the lifetime of the upper laser level when the laser is biased in the polarity that electrons flow along the growth direction, in sharp contrast to the situation for the opposite polarity.

Chiu, YenTing

338

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

339

Ballistic transport in II-VI semiconductor compounds and alloys  

NASA Technical Reports Server (NTRS)

Realistic band structures are used in calculating the group velocity and scattering rates for electrons with injection energies up to 1 eV in ZnTe, CdTe, and the low-effective-mass alloy Hg(0.7)Cd(0.3)Te. Scattering from longitudinal optical phonons, ionized impurities, and alloy disorder have been included in the full band-structure calculation, which automatically includes both intra- and intervalley scattering. Of the II-VI materials considered, at 77 K HgCdTe is superior for low injection energies (up to 0.25 eV) while CdTe is superior at higher injection energies (1 eV) at room temperature. The attainable mean free paths (equal to or greater than 1000 A) and group velocities (equal to or greater than 10 to the 8th cm/s) for both systems are comparable to values found in III-V systems.

Berding, M. A.; Krishnamurthy, S.; Sher, A.; Chen, A.-B.

1988-01-01

340

Phonons in HgCdSe crystalline alloys  

NASA Astrophysics Data System (ADS)

Phonons vibrational frequencies for HgCdSe (x ? 0.5) crystalline alloys were theoretical and experimentally studied. Two simple expressions that summarize the optical modes behavior with composition were derived. Such that the behavior of the vibrational properties of II - VI and III - V semiconductors at the ? point can be expressed as function of the product of the ionic charges (Z1Z2) and the nearest neighbor distance, d. A good agreement has been found between the observed and calculated values of the vibrational frequencies ?LO for the ternary HgCdSe alloys. Furthermore, our calculations suggest a non typical behavior of the acoustic vibrational modes similar to the one reported for HgSe. Besides, we also report the theoretical dependence of the phonon dispersion relation as function of composition.

Miranda, David A.; López R., S. A.; Romero, A. H.

2013-12-01

341

Alloy materials  

DOEpatents

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

Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)

2002-01-01

342

Iridium alloy  

US Patent & Trademark Office Database

An iridium alloy consists essentially of iridium and at least one of W and Zr, and optionally Rh. When present, W comprises between 0.01 and 5 wt % of the alloy; when present in combination with W, Zr comprises between 0.01 and 0.5 wt % of the alloy; when present alone or in combination with Rh only, Zr comprises between 0.01 and 0.09 wt % of the alloy; and when present, Rh comprises between 0.1 and 5 wt % of the alloy. The alloys may be modified by the addition of platinum and other platinum group metals and base metals. The alloys demonstrate enhanced physical and chemical properties and are suitable for use as electrode materials in spark plugs and other high temperature applications.

2009-01-27

343

Structural properties of bismuth-bearing semiconductor alloys  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

344

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

345

Nanoscale assembly of silicon-like [Al(As1-xNx)]ySi5-2y alloys: Fundamental theoretical and experimental studies of structural and optical properties  

NASA Astrophysics Data System (ADS)

Ab initio theoretical simulations of Al(As1-xNx)Si3 alloys, a new class of optoelectronic materials, confirm that these compounds are likely to be disordered via a mechanism that preserves the integrity of the constituent III-V-Si3 tetrahedra but randomizes their orientation in the average diamond lattice of the compound. This type of disorder is consistent with experimental structural data and with the proposed growth mechanism for such alloys, according to which “III:V(SiH3)3” intermediate complexes are formed in the gas phase from reactions between group-III atomic beams and V(SiH3)3 molecules, delivering the entire III-V-Si3 tetrahedra to the growing film. Experimental optical studies of these Al(As1-xNx)Si3 alloys as well as more general [Al(As1-xNx)]ySi5-2y compounds grown on Si substrates were carried out using spectroscopic ellipsometry. The resulting dielectric functions are found to be similar to broadened versions of their counterparts in pure Si. This broadening may have important practical applications, particularly in photovoltaics, because it dramatically enhances the optical absorption of Si in the visible range of the electromagnetic spectrum. A critical point analysis reveals the existence of direct optical transitions at energies as low as 2.5 eV, well below the lowest direct absorption edge of Si at 3.3 eV. Such transitions are predicted theoretically for perfectly ordered III-V-Si3 compounds, and the experimental results suggest that they are robust against tetrahedra orientational disorder.

Jiang, L.; Sims, P. E.; Grzybowski, G.; Beeler, R. T.; Chizmeshya, A. V. G.; Smith, D. J.; Kouvetakis, J.; Menéndez, J.

2013-07-01

346

Mechanosensory afferent input and neuronal firing properties in rodent spinal laminae III-V: re-examination of relationships with analysis of responses to static and time-varying stimuli.  

PubMed

Relationships between neuronal firing pattern and mechanosensory input in the deep dorsal horn were investigated using whole-cell recordings from isolated hamster spinal cord with innervation from an attached skin patch. Neurons that fired repetitively to depolarizing current (tonic cells) responded to both moving and static stimulation of their cutaneous receptive fields, and discharged continuously for the duration of stimulus application. Neurons responding to depolarizing current with transient, rapidly adapting firing (phasic cells) were significantly more responsive to stimulus movement than to static skin contact. Phasic cells typically issued a brief discharge at the onset or termination of a stimulus; their responses during static skin contact were weaker than tonic cells. Tonic cells were activated during both ramp and steady-state skin indentations, whereas phasic cells responded with their strongest excitation to displacement velocities exceeding 8 microm/ms. Mechanosensory input to phasic cells originated primarily from low threshold receptors, whereas tonic cells demonstrated a mixture of inputs from both low and high threshold sources. A third class of neurons responded to depolarizing current with a pronounced firing delay and displayed a sensitivity to cutaneous stimuli that was similar to tonic cells except they showed a modest decrease in firing as skin indentation velocity increased. The results suggest a correlation between functional properties of mechanoreceptive afferent fibers and intrinsic discharge properties of laminae III-V neurons that may significantly influence integration of cutaneous mechanosensory information at the first spinal relay. PMID:15713261

Schneider, Stephen P

2005-02-01

347

'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

2012-04-01

348

Growth of dilute BGaP alloys by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Crystal growth of dilute BGaP alloys by solid-source molecular-beam epitaxy (MBE) equipped with electron beam evaporation system as the B source is investigated with changing growth condition of the growth temperature and the V/III ratio. The B composition for BGaP alloys increases with decrease of growth temperature and increase of III/V ratio. The B incorporation into the GaP matrix is difficult compared to other group-III atoms (Al or In) incorporations due to bonds in the matrix are highly strained calculated by valence force-field model. The possibilities of forming and conserving B3P bonds opportunity increased with decrease of growth temperature and increase of the V/III ratio.

Urakami, N.; Fukami, F.; Sekiguchi, H.; Okada, H.; Wakahara, A.

2013-09-01

349

Aluminum alloy  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

350

Distributed feedback GaSb based laser diodes with buried grating  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

351

GaSb based ternary and quaternary diffused junction devices for TPV applications  

SciTech Connect

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

Sundaram, V.S.; Saban, S.B.; Morgan, M.D.; Horne, W.E.; Evans, B.D.; Ketterl, J.R. [EDTEK Inc. 7082 S. 220th Street Kent, Washington 98032 (United States); Morosini, M.B.; Patel, N.B. [Instituto de Fisica, UNICAMP, Campinas, Brasil (Brazil); Field, H. [NREL, Golden, Colorado (United States)

1997-03-01

352

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  

SciTech Connect

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 vs. deposition potential indicate that the potential of perfect stoichiometry (PPS), the potential at which x /sub Cd/ is identical to x /sub Te/ and x /sub CdTe/ approx. = 1, can li positive of the pure cadmium Nernst potential (E /sub Cd/ ) at the sharp positive shoulder of a nearly constant current plateau. This plateau corresponds to cadmium underpotential depositing on a nearly 1:1 basis with tellurium only because of the reduction in cadmium activity associated with compound formation. This is named conventional underpotential deposition (CUD). n-CdTe can be deposited within this plateau region, but native p-CdTe can be deposited only within a very small potential range positive of the PPS. When the cadmium and tellurium ion concentrations are of the same order of magnitude, the PPS can be shifted negative of E /sub Cd/ and onto the steep portion of the cadmium current curve. If the diffusion-limited current densities are matched so that equal molar fluxes occur at the cathode, the PPS shifts onto the diffusion-limited, nearly-constant current region negative of E /sub Cd/ so stoichiometric CdTe (MX) can be plated over a broad potential range. This is named matched diffusion-limited current (MDLC) deposition. The activity coefficient parameter, BETA, has negligible effect on the PPS during CUD, but varies the width of the plateau region. Less negative ..delta..G/sup 0/ /sub MX/ values shift the PPS negative and decrease the plateau width.

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

1985-12-01

353

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

354

Electronic Band Structure of GaNxPyAs1-x -y Highly Mismatched Alloys: Suitability for Intermediate-Band Solar Cells  

NASA Astrophysics Data System (ADS)

Formation of an intermediate band in GaNxP0.4As0.6-x alloys due to the isovalent doping by nitrogen is studied by photoreflectance and absorption spectroscopy. The fundamental energy gap transition (E0) observed for an N-free alloy is replaced by two optical transitions (E- and E+) in GaNPAs layers. The E - and E+ transitions are explained within the band anticrossing model, where the localized level of nitrogen interacts with the conduction band of the GaPAs host, splitting it into two subbands. The valence band (VB) is mostly unaffected by nitrogen incorporation as confirmed by the same spin-orbit splitting for N-free and N-containing alloys. The energy position of the E - subband and a strong optical absorption between the VB and the E- subband indicates the GaNPAs alloys have an electronic structure suitable for intermediate-band solar cells. Such an electronic structure is not observed for other III-V alloys like GaInAs, GaInAsP, etc., for which the virtual crystal approximation can be applied to describe the evolution of the electronic structure with the alloy content. Results obtained in this work clearly show that GaNPAs with a few percent of nitrogen is an unusual material system, for which the electronic structure properties differ very significantly from properties of well-known III-V alloys, and the application of virtual crystal approximation in this case is inappropriate or very limited.

Kudrawiec, R.; Luce, A. V.; Gladysiewicz, M.; Ting, M.; Kuang, Y. J.; Tu, C. W.; Dubon, O. D.; Yu, K. M.; Walukiewicz, W.

2014-04-01

355

VAl Alloy  

NASA Astrophysics Data System (ADS)

Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.

Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

2014-06-01

356

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

357

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

358

Alloy softening in binary molybdenum alloys  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

359

Carrier and Spin Dynamics in InAsP Ternary Alloys  

NASA Astrophysics Data System (ADS)

The recent rapid progress in the field of spintronics involves extensive measurements of carrier and spin relaxation dynamics in III-V semiconductors. In addition, as the switching rates in electronic and optoelectronic devices are pushed to higher frequencies, it is important to understand carrier dynamic phenomena in semiconductors on femtosecond time-scales. In this work, we employed time and polarization-resolved differential transmission measurements in near and mid-infrared, to probe carrier and spin relaxation times in several InAsP ternary alloys. Our results demonstrate the unique and complex dynamics in this material system that can be important for electronic and optoelectronic devices. We present our experimental observations and compare them with the observations in InAs and InP.

Meeker, Michael; McCutcheon, Kelly; Bhowmick, Mithun; Magill, Brenden; Khodaparast, Giti A.; Tischler, Joe G.; Choi, Sukgeun G.; Palmstrøm, Chris J.

2013-03-01

360

Advanced battery grid alloys  

Microsoft Academic Search

The alloys used in lead-acid batteries have changed markedly during the past five years. The problems in casting lead-calcium alloys have been overcome by the addition of aluminum to the alloys. The aluminum protects the alloys and prevents loss of calcium, yielding greatly improved grain structures and corrosion resistance. Concern about reduced water loss has led to a dramatic reduction

Prengaman

1984-01-01

361

Planar Hall effect in III-Mn-V ferromagnetic semiconductor alloys  

NASA Astrophysics Data System (ADS)

Recently Tang et al. have observed giant planar Hall effect in epitaxial GaMnAs thin films. The effect was in this case found to be about 4 orders of magnitude stronger than in metallic ferromagnets. The origin for such unusually large planar Hall resistance still remains unclear. It is therefore important to increase our data-base on this effect by studying it in GaMnAs over a wide range of Mn concentrations, as well as in other III-V-based ferromagnetic alloys. Here we report a detailed study of the planar Hall effect in both GaMnAs digital and random alloys with various Mn concentrations; and in quaternary GaMnAsSb alloys. Preliminary observations of the planar Hall effect in thin compressively-strained InMnAs ferromagnetic films grown on InAlAs buffers will also be reported. These results provide important information on the magnetic anisotropy in the III-Mn-V family of ferromagnetic semiconductors.

Lim, W. L.; Liu, X.; Ge, Z.; Dobrowolska, M.; Furdyna, J. K.; Wojtowicz, T.

2004-03-01

362

Extrusion of Almgsi Alloys.  

National Technical Information Service (NTIS)

Contents: Influence of the composition and structure on the behavior of aluminum-magnesium-silicon alloys on surface treatment, resistance to corrosion of aluminum-magnesium-silicon alloys; influence of the composition on the mechanical properties of alum...

G. E. Gardam

1966-01-01

363

High strength alloys  

DOEpatents

High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

2010-08-31

364

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

365

Advanced battery grid alloys  

SciTech Connect

The alloys used in lead-acid batteries have changed markedly during the past five years. The problems in casting lead-calcium alloys have been overcome by the addition of aluminum to the alloys. The aluminum protects the alloys and prevents loss of calcium, yielding greatly improved grain structures and corrosion resistance. Concern about reduced water loss has led to a dramatic reduction in the antimony content of battery grid alloys to levels of less than 2% Sb. New, very low antimony alloys which can be handled or conventional or continuous casting equipment have increased conductivity, reduced corrosion rates, reduced self-discharge and reduced gassing rates compared to conventional 3-5% alloys, but retain the ability to recover from deep discharge.

Prengaman, R.D.

1984-10-01

366

Precipitation-hardening alloys  

SciTech Connect

Designers of stainless steel and nickel alloy products are routinely faced with making tradeoffs between the properties needed for manufacturing and those required for its end use. When such compromises begin to adversely impact cost or performance, precipitation hardening (PH) alloys may offer a solution. Despite their more complex metallurgy, PH alloys are not necessarily more costly than many nonage-hardenable alloys. In fact, performance may be substantially higher than such alloys, without a cost penalty. Although corrosion resistance is decreased (or possibly increased) during the aging cycle, it is only by a slight amount. This article takes a closer look at PH stainless steel and nickel alloys, and provides several examples of applications.

Brucker, R. [Ulbrich Stainless Steels and Special Metals, North Haven, CT (United States)

1995-12-01

367

Application of Rapidly Solidified Alloys.  

National Technical Information Service (NTIS)

This program is being conducted for the purpose of applying the principle of rapid solidification of aluminum and iron alloy powders and subsequent development of stronger alloy compositions for fan blade application (Al alloys) and higher speed bearing m...

A. R. Cox T. D. Tillman J. W. Simon

1979-01-01

368

Uranium-titanium-niobium alloy  

Microsoft Academic Search

This patent describes a uranium alloy having small additions of Ti and Nb. It shows improved strength and ductility in cross-section of greater than one inch over prior uranium alloy having only Ti as an alloy element.

Ludtka

1990-01-01

369

Uranium-titanium-niobium alloy  

SciTech Connect

This patent describes a uranium alloy having small additions of Ti and Nb. It shows improved strength and ductility in cross-section of greater than one inch over prior uranium alloy having only Ti as an alloy element.

Ludtka, G.M.

1990-11-06

370

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

371

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

372

Aluminum alloy development  

SciTech Connect

Development of an aluminum alloy which has higher strength than previous alloys while still showing acceptable levels of corrosion resistance and fracture is presented. Two different approaches to this goal are described; a final thermomechanical treatment method employed deformation and aging, while the second method depended solely on thermal practices to enhance the strength/corrosion resistance combination. Attention is given to a 7055 alloy that offers significant weight savings potential for applications requiring high compression strength combined with good corrosion resistance. It is indicated that structures including keel beams, horizontal tails, upper wings, cargo rails, and seat tracks on commercial transports are all candidate applications for this alloy.

Not Available

1991-09-01

373

Machinability of Titanium Alloys  

NASA Astrophysics Data System (ADS)

Titanium and its alloys find wide application in many industries because of their excellent and unique combination of high strength-to-weight ratio and high resistance to corrosion. The machinability of titanium and its alloys is impaired by its high chemical reactivity, low modulus of elasticity and low thermal conductivity. A number of literatures on machining of titanium alloys with conventional tools and advanced cutting tool materials is reviewed. The results obtained from the study on high speed machining of Ti-6Al-4V alloys with cubic boron nitride (CBN), binderless cubic boron nitride (BCBN) and polycrystalline diamond (PCD) are also summarized.

Rahman, Mustafizur; Wong, Yoke San; Zareena, A. Rahmath

374

(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

375

(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

376

Lattice constant grading in the Al.sub.y Ga.sub.1-y As.sub.1-x Sb.sub.x alloy system  

DOEpatents

Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5 .mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photolvoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of growing layer.

Moon, Ronald L. (Palo Alto, CA)

1980-01-01

377

Lattice constant grading in the Al.sub.y Ca.sub.1-y As.sub.1-x Sb.sub.x alloy system  

DOEpatents

Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5.mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photovoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of the growing layer.

Moon, Ronald L. (Palo Alto, CA)

1981-01-01

378

Aluminum battery alloys  

SciTech Connect

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, D.S.; Scott, D.H.

1985-11-19

379

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 sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

Conner, William V. (Boulder, CO)

1983-01-01

380

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

381

Aluminum battery alloys  

DOEpatents

Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, David S. (Richmond, VA); Scott, Darwin H. (Mechanicsville, VA)

1985-01-01

382

Shape Memory Alloys  

Microsoft Academic Search

This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,

Abhijit Bhattacharyya; Dimitris C Lagoudas

2007-01-01

383

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

384

Formable Sheet Titanium Alloys.  

National Technical Information Service (NTIS)

The objectives of this program were to evaluate three promising experimental alloys by optimizing mill processing using formability, formageability, and uniformity and consistency of properties as the criteria. The three alloys (1) Ti-8V-7Cr-3Al-4Sn-1Zr, ...

G. Lenning

1976-01-01

385

Advanced Cast Aluminum Alloys.  

National Technical Information Service (NTIS)

A recent advancement in cast aluminum alloys has demonstrated that complex shapes can be cast from a microalloyed Al-Cu alloy in dry sand molds with chills and that these castings can be heat treated to produce mechanical and physical properties nearly co...

A. P. Druschitz J. Griffin

2009-01-01

386

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

387

Alloys in energy development  

SciTech Connect

The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

Frost, B.R.T.

1984-02-01

388

First III–V-nitride-based violet laser diodes  

Microsoft Academic Search

InGaN multi-quantum-well (MQW) structure laser diodes (LDs) were grown by metalorganic chemical vapor deposition on a sapphire substrate with (112?0) orientation (A face). The mirror facet for a laser cavity was formed by cleaving the substrate along the (11?02) orientation (R-face). The structure of the LDs was an InGaN MQW\\/GaN\\/AlGaN separate confinement heterostructure (SCH). As an active layer, the InGaN

Shuji Nakamura

1997-01-01

389

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

2009-01-01

390

Monolithic III-V/Silicon Spatial Light Modulator  

NASA Technical Reports Server (NTRS)

Current techniques for growth of device-quality GaAs on silicon substrates enables fabrication of silicon-based version of photodiode-coupled spatial light modulator. Monolithic photodiode-coupled light-modulator array constructed on silicon substrate by growing InAs/GaAs multiple-quantum-wells over silicon PIN diode layer. Intermediate GaAs buffer layer confines attice-misfit dislocations to vicinity of silicon. Use of silicon makes available wider range of auxiliary on-chip signal-processing circuitry for coding and decoding of data, addition or subtraction of brightness levels, spatial reformatting, and rescaling.

Maserjian, Joseph; Eng, Sverre T.

1989-01-01

391

III-V Solar Cells and Concentrator Arrays  

NASA Astrophysics Data System (ADS)

Semiconductor heterostructures allow us to solve the problems of controlling the fundamental parameters of the semiconductor devices. These heterostructures provide the ability to change the electronic band structure, band gaps and refractive indices of the material itself during epitaxial growth, as well as to control the effective masses and mobilities of the charge carriers in it. The development of the physics and technology of semiconductor heterostructures has resulted in remarkable changes in our everyday life. Heterostructure electronics is widely used in many areas. It is hardly possible to imagine our life without double heterostructure (DHS) laser-based telecommunication systems, heterostructure solar cells (HSSCs) and light-emitting diodes (LEDs), heterostructure bipolar transistors and low-noise, high-electron mobility transistors for high-frequency applications including, for example, satellite television. Now DHS lasers exist in practically every home in CD players. Heterostructure solar cells are widely used for space and terrestrial applications.

Alferov, Z. I.; Andreev, V. M.; Rumyantsev, V. D.

392

III-V Nanowires—Extending a Narrowing Road  

Microsoft Academic Search

Semiconductor nanowires have attracted considerable attention during the last decade and are considered as an alternative path to extend the road for scaled semiconductor devices. The interest is motivated by the improved electrostatic control in the cylindrical geometry and the possibility to utilize heterostructures in transistor design. Currently, nanowire transistors have been realized both in III-Vs and in group IV

Lars-Erik Wernersson; Claes Thelander; Erik Lind; Lars Samuelson

2010-01-01

393

Physics and Technology of III-V Pseudomorphic Structures.  

National Technical Information Service (NTIS)

We have shown that pseudomorphic InAsP on InP is a viable alternative to the conventional InGaAsP for long wavelength optical fiber communications. The layer thickness and composition are independently controlled in gas source molecular beam epitaxy. We d...

C. W. Tu

1997-01-01

394

The Performance of Advanced III-V Solar Cells  

NASA Technical Reports Server (NTRS)

Test results show triple junction solar cells with efficiencies as high as 27% at 28C and 136.7 mw/sq cm. Triple junction cells also achieve up to 27.5% at -120 C and 5 mw/sq cm, conditions applicable to missions to Jupiter. Some triple junction cells show practically no degradation as a result of Low Intensity Low Temperature (LILT) effects, while others show some; this degradation can be overcome with minor changes to the cell design.

Mueller, Robert L.; Gaddy, Edward; Day, John H. (Technical Monitor)

2002-01-01

395

Random stacking sequences in III-V nanowires are correlated  

NASA Astrophysics Data System (ADS)

We investigate crystal plane stacking in InP nanowires with marked wurtzite/zinc-blende phase mixing. We measure the length distributions of hexagonal and cubic segments and the frequencies of all short sequences of monolayers. This reveals spatial correlations extending over several monolayers, which we describe in terms of conditional probabilities. Results can be modeled by considering the energy barriers for nucleation on top of all types of preexisting stacking. A quantitative agreement is obtained only if the interaction with the underlying layers involves the edge energy of the nucleus.

Priante, Giacomo; Harmand, Jean-Christophe; Patriarche, Gilles; Glas, Frank

2014-06-01

396

Structural properties of <111>B -oriented III-V nanowires  

NASA Astrophysics Data System (ADS)

Controlled growth of nanowires is an important, emerging research field with many applications in, for example, electronics, photonics, and life sciences. Nanowires of zinc blende crystal structure, grown in the <111>B direction, which is the favoured direction of growth, usually have a large number of twin-plane defects. Such defects limit the performance of optoelectronic nanowire-based devices. To investigate this defect formation, we examine GaP nanowires grown by metal-organic vapour-phase epitaxy. We show that the nanowire segments between the twin planes are of octahedral shape and are terminated by {111} facets, resulting in a microfaceting of the nanowires. We discuss these findings in a nucleation context, where we present an idea on how the twin planes form. This investigation contributes to the understanding of defect formation in nanowires. One future prospect of such knowledge is to determine strategies on how to control the crystallinity of nanowires.

Johansson, Jonas; Karlsson, Lisa S.; Patrik T. Svensson, C.; Mårtensson, Thomas; Wacaser, Brent A.; Deppert, Knut; Samuelson, Lars; Seifert, Werner

2006-07-01

397

Characterization of Hydrogen Complex Formation in III-V Semiconductors  

SciTech Connect

Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55?m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

Williams, Michael D.

2006-09-28

398

The III-V heterojunction structures and high speed devices  

NASA Astrophysics Data System (ADS)

Much better p-GaAs/n-Si heterojunction has been obtained. This led to new experimental and theoretical studies of these diodes and progress has been made in the understanding of the electrical properties of the GaAs/Si interface. The study about dislocation reduction by annealing has been continued in connection with N. Otsuka from Purdue University. Interesting features has been revealed by TEM plan view made such as the creation of a clearly observable misfit dislocation network after annealing.

Morkoc, Hadis

1987-03-01

399

Spin Decoherence in III-V Quantum Wells and Superlattices  

NASA Astrophysics Data System (ADS)

Electron spin decoherence in zincblende type quantum wells (QW) and superlattices (SL) near room temperature is dominated by the precessional D'yakonov-Perel' (DP) mechanism. The effective precession is a direct result of the spin splitting of the conduction band due to bulk inversion asymmetry (BIA) of the constituent zincblende semiconductors and also to any native interface asymmetry (NIA) of the heterointerfaces. The effect of BIA is dominant in common atom (CA) systems such as GaAs/AlGaAs QWs. However, in no common atom (NCA) systems such as InAs/GaSb, the interface bonds are different in character from those in the bulk and are asymmetrically oriented (giving rise to NIA). To accurately describe the DP spin relaxation mechanism we employ a nonperturbative nanostructure model based on a fourteen-bulk-band basis, including both BIA and NIA. Quantitative agreement between these calculations and measurements is found for GaAs/AlGaAs, InGaAs/InP, and GaSb/AlSb QW's, as well as for an InAs/GaSb SL.

Lau, Wayne H.; Flatté, Michael E.

2001-03-01

400

Catalyst-free, III-V nanowire photovoltaics  

NASA Astrophysics Data System (ADS)

We report on room temperature, photovoltaic operation of catalyst-free GaAs p-i-n junction nanowire arrays. Growth studies were first performed to determine the optimum conditions for controlling the vertical and lateral growth of the nanowires. Following this, devices consisting of axial p-i-n junctions were fabricated by planarising the nanowire arrays with a hard baked polymer. We discuss the photovoltaic properties of this proof-of-concept device, and significant improvements to be made during the growth.

Davies, D. G.; Lambert, N.; Fry, P. W.; Foster, A.; Krysa, A. B.; Wilson, L. R.

2014-05-01

401

Scanning Tunneling Microscopy of III-V Semiconductors.  

National Technical Information Service (NTIS)

Scanning tunneling microscopy and theory were combined to create novel depressive quantum dots at room temperature on the (110) surfaces of InSb --- dots which merit further exploration as potential nanopixels for tiny-device lithography; develop a strain...

J. D. Dow

1994-01-01

402

Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals.  

National Technical Information Service (NTIS)

Nonlinear optical processes provide a physical mechanism for converting the frequency of light. This allows the generation of tunable light sources at wavelengths inaccessible with lasers, leading to a diverse set of applications in fields such as spectro...

K. Rivoire

2012-01-01

403

III–V nitride based light-emitting devices  

Microsoft Academic Search

High brightness InGaN single-quantum-well structure (SQW) blue and green light-emitting diodes (LEDs) with luminous intensities of 2 cd and 10 cd have been achieved and commercialized. By combining these high-power and high-brightness blue InGaN SQW LED, green InGaN SQW LED and red AlInGaP LED, many kinds of applications, such as LED full-color displays and LED white lamps for use in

Shuji Nakamura

1997-01-01

404

Magnesium silicide intermetallic alloys  

SciTech Connect

Methods of induction melting an ultra-low-density magnesium silicide (Mg[sub 2]Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg[sub 2]Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 [times] 10[sup 5] Pa), at a temperature close to but not exceeding 1,105 C [+-] 5 C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg[sub 2]Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg[sub 2]Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg[sub 2]Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg[sub 2]Si matrix were found in the Mg[sub 2]Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

Li, G.H.; Gill, H.S.; Varin, R.A. (Univ. of Waterloo, ON (Canada). Dept. of Mechanical Engineering)

1993-11-01

405

Magnesium silicide intermetallic alloys  

NASA Astrophysics Data System (ADS)

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

Li, Gh.; Gill, H. S.; Varin, R. A.

1993-11-01

406

Low Sb alloys  

SciTech Connect

A major change in the battery industry is a reduction in the amount of lead in the battery and an increase in the performance of the battery. This reduction in lead comes from the grids. The grids are thinner and lighter, but present several problems. As battery grids become thinner, the resistance to the passage of current increases. The lowest resistance alloys are lead-calcium and low antimony alloys. Fluidity is a problem. The alloys used in the continuous grid casting processes must be very fluid in order to be processed into thin grids. Other problems are also discussed including freezing range, gassing, grain structure, and rate of strengthening.

Prengaman, R.D.

1983-10-01

407

Lightweight Disk Alloy Development.  

National Technical Information Service (NTIS)

A 3-year program was conducted with the intention of developing NiAl-base alloys with mechanical and physical properties suitable for use as a lightweight turbine disk material. The program emphasized overcoming the room temperature brittleness problem an...

C. C. Law D. M. Pease M. J. Blackburn P. C. Clapp S. M. Russell

1991-01-01

408

Electroplating on titanium alloy  

NASA Technical Reports Server (NTRS)

Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

Lowery, J. R.

1971-01-01

409

Brazing dissimilar aluminum alloys  

NASA Technical Reports Server (NTRS)

Dip-brazing process joins aluminum castings to aluminum sheet made from different aluminum alloy. Process includes careful cleaning, surface preparation, and temperature control. It causes minimum distortion of parts.

Dalalian, H.

1979-01-01

410

Corrosion behavior of alloys  

NASA Astrophysics Data System (ADS)

Studies of molten nitrates at temperatures in the 450 - 550 C range were made to obtain information which will ultimately permit an understanding of the corrosion behavior of structural alloys, such as Incoloy 800, that will be employed in thermal loops in solar power systems. Initial activity will involve studies of species expected to exist in these melts from corrosion of structural alloys, i.e., iron, nickel and chromium.

Osteryoung, R. A.; Fernandez, H.

1981-03-01

411

Magnesium silicide intermetallic alloys  

Microsoft Academic Search

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not

Gh. Li; H. S. Gill; R. A. Varin

1993-01-01

412

Magnesium silicide intermetallic alloys  

Microsoft Academic Search

Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots\\u000a of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under\\u000a overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not

G. H. Li; H. S. Gill; R. A. Varin

1993-01-01

413

nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP.  

EPA Pesticide Factsheets

Did you mean: nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. ?

414

nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP.  

EPA Pesticide Factsheets

Did you mean nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. nanostructured alloys. Metal matrix composites. Quasicrystal. Dental Implant. Laser Processing. Mg alloy. PLD. TCLP. ?

415

Disk Alloy Development  

NASA Technical Reports Server (NTRS)

The advanced powder metallurgy disk alloy ME3 was designed using statistical screening and optimization of composition and processing variables in the NASA HSR/EPM disk program to have extended durability at 1150 to 1250 "Fin large disks. Scaled-up disks of this alloy were produced at the conclusion of this program to demonstrate these properties in realistic disk shapes. The objective of the UEET disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. Scaled-up disks processed in the HSR/EPM Compressor / Turbine Disk program were sectioned, machined into specimens, and tested in tensile, creep, fatigue, and fatigue crack growth tests by NASA Glenn Research Center, in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. Additional sub-scale disks and blanks were processed and tested to explore the effects of several processing variations on mechanical properties. Scaled-up disks of an advanced regional disk alloy, Alloy 10, were used to evaluate dual microstructure heat treatments. This allowed demonstration of an improved balance of properties in disks with higher strength and fatigue resistance in the bores and higher creep and dwell fatigue crack growth resistance in the rims. Results indicate the baseline ME3 alloy and process has 1300 to 1350 O F temperature capabilities, dependent on detailed disk and engine design property requirements. Chemistry and process enhancements show promise for further increasing temperature capabilities.

Gabb, Tim; Gayda, John; Telesman, Jack

2001-01-01

416

Ultrahigh temperature intermetallic alloys  

SciTech Connect

A new family of Cr-Cr{sub 2}Ta intermetallic alloys based on Cr-(6--10)Ta (at.%) is under development for structural use in oxidizing environments in the 1,000-1,300 C (1,832--2,372 F) temperature range. Development objectives relate to high temperature strength and oxidation resistance and room temperature fracture toughness. The 1,200 C (2,192 F) strength goals have been met: yield and fracture strengths of 275 MPa (40 ksi) and 345 MPa (50 ksi), respectively, were achieved. Progress in attaining reasonable fracture toughness of Cr-Cr{sub 2}Ta alloys has been made; current alloys exhibit room-temperature values of about 10--12 MPa{radical}m (1.1 MPa{radical}m = 1 ksi{radical}in.). Oxidation rates of these alloys at 950 C (1,742 F) in air are in the range of those reported for chromia-forming alloys. At 1,100 C (2,012 F) in air, chromia volatility was significant but, nevertheless, no scale spallation and positive weight gains of 1--5 mg/cm{sup 2} have been observed during 120-h, 6-cycle oxidation screening tests. These mechanical and oxidative properties represent substantial improvement over Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr alloys previously developed.

Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.

1998-11-01

417

Band structure properties of novel BxGa1-xP alloys for silicon integration  

NASA Astrophysics Data System (ADS)

We have grown and investigated the band-structure properties of novel III-V alloys based upon BxGa1-xP. These layers are utilized as strain-compensating layers for the lattice-matched integration of novel direct bandgap Ga(NAsP) quantum well lasers on silicon. Experimental and theoretical studies reveal the dependence of the direct and indirect band gaps for strained BxGa1-xP layers grown on silicon as a function of Boron composition from which we derive the properties of free-standing BxGa1-xP. For Boron fractions up to 6%, we find that the bowing parameter for the lowest (indirect) band gap is - 6.2 +/- 0.2 eV. High crystalline quality and promising optical material properties are demonstrated and applied to monolithically integrated Ga(NAsP)/(BGa)P multi-quantum well heterostructures on (001) silicon substrates. Our results show that novel (BGa)P layers are suitable for strain compensation purposes, which pave the way towards a commercial solution for the monolithic integration of long term stable laser diodes on silicon substrates.

Hossain, Nadir; Hosea, T. J. C.; Sweeney, Stephen J.; Liebich, Sven; Zimprich, Martin; Volz, Kerstin; Kunert, Bernardette; Stolz, Wolfgang

2011-09-01

418

Above-room-temperature ferromagnetism in GaSb/Mn digital alloys*  

NASA Astrophysics Data System (ADS)

As an effort to realize spintronic applications with 6.1 angstrom III-V semiconductors, digital alloys of GaSb/Mn were fabricated by molecular beam epitaxy and characterized with a wide range of experimental techniques. Cross sectional scanning electron microscopy studies indicate that the Mn-containing layers consist of quasi-2D islands of MnSb and isolated Mn ions. Two ferromagnetic phases were observed, with a low temperature phase having a Tc typically below 50 K and the other one observable at 400 K. The properties of the two phases, including their anisotropy and interaction, were studied with both magnetization measurements and magnetotransport techniques. For external tuning of ferromagnetism in this material system, gated structures were fabricated for studies of electrically controlled ferromagnetism. Systematic and significant changes in coercive fields were observed as a function of applied bias. * In collaboration with G. B. KIM, M. CHEON, X. CHEN, S. WANG, B. D. McCOMBE, Y. SASAKI, X. LIU, T. WOJTOWICZ, J. K. FURDYNA, G. BOISHIN and L. J. WHITMAN; this work was supported by DARPA/ONR (N00014-00-1-0951)

Luo, H.

2003-03-01

419

Mechanical behavior and properties of mechanically alloyed aluminum alloys  

Microsoft Academic Search

The fracture and deformation behaviors of several product forms produced from mechanically alloyed (MA) aluminum alloys 9052 and 905XL were studied. The main operative strengthening mechanism is strengthening due to the submicron grain size. Ductility and toughness were found to be controlled by the morphology of the prior particle boundaries. We propose that the work-hardening behavior of these MA alloys

H. R. Last; R. K. Garrett

1996-01-01

420

Electrostatic Deflection Binary Alloy Evaporator.  

National Technical Information Service (NTIS)

A new technique for producing thin film binary alloys is discussed which used periodic deflection of an electron beam between two sources in a vacuum evaporator. This technique makes it possible to produce high quality binary alloys of predetermined ratio...

E. A. Stern J. L. Erskine J. M. Tracy

1970-01-01

421

Finding the Alloy Genome  

NASA Astrophysics Data System (ADS)

First-principles codes can nowadays provide hundreds of high-fidelity enthalpies on thousands of alloy systems with a modest investment of a few tens of millions of CPU hours. But a mere database of enthalpies provides only the starting point for uncovering the ``alloy genome.'' What one needs to fundamentally change alloy discovery and design are complete searches over candidate structures (not just hundreds of known experimental phases) and models that can be used to simulate both kinetics and thermodynamics. Despite more than a decade of effort by many groups, developing robust models for these simulations is still a human-time-intensive endeavor. Compressive sensing solves this problem in dramatic fashion by automatically extracting the ``sparse model'' of an alloy in only minutes. This new paradigm to model building has enabled a new framework that will uncover, automatically and in a general way across the periodic table, the important components of such models and reveal the underlying ``genome'' of alloy physics.

Hart, Gus L. W.; Nelson, Lance J.; Zhou, Fei; Ozolins, Vidvuds

2012-10-01

422

Aluminum-lithium alloys II  

SciTech Connect

The topics covered in this volume include: methods of alloy preparation (including ingot casting, rapid solidification, and mechanical alloying); processing and alloying effects on microstructure and properties; superplastic deformation; and physical metallurgy fundamentals. Other topics discussed include: weldability; sodium and hydrogen effects on fracture; corrosion behavior (including general corrosion, stress corrosion, and high-temperature oxidation); and monotonic and cyclic properties at ambient and elevated temperatures. Attention is also given to the use of Al-Li alloys in aircraft structures.

Starke, E.A. Jr.; Sanders, T.H. Jr.

1984-01-01

423

Laser boriding of titanium alloys  

Microsoft Academic Search

The low wear resistance of titanium and its alloys limits their use in machine building. Methods for the surface hardening of titanium and its alloys, which tend to enhance their antifriction properties. are of significant interest in this respect. Laser alloying is one of the most promising methods of improving the strength of the surface. In this study. we investigated

V. S. Postnikov; M. N. Tagirov

1994-01-01

424

Tantalum and tantalum alloy tubing  

SciTech Connect

The specification includes ordering information, manufacture, chemical requirements, tension testing, flare test, ultrasonic test, hydrostatic test, pneumatic proof test, dimensions and tolerances, finish, packaging, marking, inspection, and certification. The specification covers tantalum and tantalum alloy tubing of the following types: Alloy 400 (unalloyed tantalum) and Alloy 401 (tantalum-10% tungsten). (JMT)

Not Available

1981-01-01

425

Modeling dissolution in aluminum alloys  

Microsoft Academic Search

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working,

Tracie Lee Durbin

2005-01-01

426

De-alloyed platinum nanoparticles  

DOEpatents

A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

Strasser, Peter (Houston, TX); Koh, Shirlaine (Houston, TX); Mani, Prasanna (Houston, TX); Ratndeep, Srivastava (Houston, TX)

2011-08-09

427

Method of preparing alloy compositions  

Microsoft Academic Search

This patent describes a method of improving the oxidation resistance of an existing crystalline nickel-based alloy composition. It comprises the steps of: providing an existing crystalline nickel-based alloy comprising: nickel; chromium; and at least one additional alloy element selected from the group consisting of nickel, chromium, molybdenum, manganese, silicon, carbon, vanadium, cobalt, copper, nitrogen, titanium, zirconium, aluminum, and mixtures thereof,

Corwin

1990-01-01

428

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

429

ELECTROLESS-PLATED BRAZING ALLOYS  

Microsoft Academic Search

The electroless-plating process deposits an Ni-P brazing alloy that ; exhibits excellent wetability and flowability in conjunction with each high-; temperature alloys as austenitic stainless steels or Inconel when heated above ; the eutectic temperature in a dry hydrogen atmosphere. Complex tubeto-fin heat ; exchanger assemblies can be fabricated by preplating with electroless Ni-P alloy ; and then brazing at

P. Patriarca; G. M. Slaughter; W. D. Manly

1957-01-01

430

Formation of amorphous Fe-B alloys by mechanical alloying  

SciTech Connect

Using a novel ball mill with controlled ball movement we have produced for the first time amorphous Fe{sub 50}B{sub 50} and Fe{sub 40}B{sub 60} alloys and nanocrystalline Fe{sub 80}B{sub 20} and Fe{sub 66}B{sub 34} alloys by mechanical alloying. The structural evolution of elemental powder mixtures is studied following milling and subsequent thermal treatment. Upon heating both amorphous and nanostructural mechanically alloyed Fe-B alloys transform into a mixture of equilibrium phases.

Calka, A.; Radlinski, A.P. (Department of Electronic Materials Engineering, Research School of Physical Sciences, Australian National University, Canberra, Australia (AU))

1991-01-14