bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incorporation of Excess Arsenic in GaAs and AlGaAs Epilayers Grown at Low Substrate Temperatures by Molecular Beam Epitaxy
Authors: Melloch M. R. , Otsuka N. , Mahalingam K. , Warrew A. C. , Woodall J. M. , Kirchner P. D. 
Published: March 2011

ABSTRACTExcess arsenic can be incorporated in GaAs and AIGaAs epilayers by growing at low substrate temperatures (LT-GaAs and LT-AIGaAs) by molecular beam epitaxy (MBE). Upon annealing these epilayers, the excess As precipitates forming GaAs:As and AIGaAs:As. Using transmission electron microscopy (TEM), we have measured the densities and sizes of the As precipitates and thereby determined the amount of excess As incorporated in these epilayers. The volume fraction of excess As as a function of inverse substrate growth temperature follows an Arrhenius-type behavior with an activation energy of 0.87 eV. The sizes of the As precipitates increase and the densities decrease with increase anneal temperatures; for Si-doped GaAs:As this results in n-type material when the densities become small enough that the depletion regions around the As precipitates no longer overlap. Also investigated is the formation of As precipitates at GaAs/AIGaAs heterojunctions and superlattices, and our attempts to tailor the As precipitate distribution.
Material and Device Characteristics of MBE Microwave Power FETs with Buffer Layers Grown at Low Temperature (300°C)
Authors: Ballingall J. M. , Ho Pin , Smith R. P. , Wang S. , Tessmer G. , Yu T. , Hall Ernest L. , Hutchins Gudrun 
Published: March 2011

ABSTRACTMBE GaAs grown at low temperature (300°C) is evaluated for its suitability as a buffer layer for microwave power FETs. Hall effect and capacitance-voltage (C-V) measurements show that low temperature (LT) buffers may have strong deleterious effects on the electronic quality of FET active layers unless they are heat-treated in-situ at 600'C and topped with a thin (∼0. lμm) 600°C GaAs buffer prior to growth of the FET active layer. The voltage isolation properties of the LT buffers are found to be thermally stable to rapid thermal anneals up to 870°C for 10 seconds.Transmission electron microscopy (TEM) cross-sections were examined on FET layers with LT buffer layers which ranged in thickness from 0.1μm to 1.0μm. The TEM reveals a high density (∼1017 cm−3) of small (<100Å) arsenic precipitates in all of the buffer layers studied. In cases where the LT buffer is not heat treated and topped with a thin 600°C GaAs buffer layer, dislocations and arsenic precipitates extend from the buffer layer into the FET active layer. Their presence in the active layer correlates with the degradation in electronic properties observed with Hall effect and CV. Microwave power FETs were measured at DC and 5 GHz. DC and RF results for devices with LT buffer layers are comparable to devices with conventional buffer layers.
A High Performance Optically Gated Heterostructure Thyristor Passivated with LT-GaAs
Authors: Zhao J. H. , Burke T. , Larson D. , Weiner M. , Chin A. , Ballingall J. M. , Yu T.-H. 
Published: March 2011

ABSTRACTA high performance, Al0.3Ga0.7As/GaAs based, optically gated thyristor with a bulk semi-insulating(SI) GaAs 650 μm in thickness as the voltage blocking layer has been fabricated and characterized for high power pulsed switching applications. Low temperature(LT) GaAs was used to passivate the device surface and was found to greatly improve the switch hold-off voltage. The switched current as a function of bias up to 2,200 V (34 kV/cm) has been tested and the maximum switched current was 240 A with a di/dt equal to 2.02×1010 A/s. The forward dynamic current-voltage characteristics have been measured and the dissipated energy per switching determined. It was found that very sensitive triggering of the switch is possible, even with a light emitting diode operating in the sub-mW range, when the thyristor is reverse biased. The sensitive triggering is a result of the carrier tunneling through the reverse biased pn junctions.
Multi-Hundred Gigahertz Photodetector Development Using LT GaAs
Authors: Chen Y. , Williamson S. , Brock T. , Smith F. W. , Calawa A. R. 
Published: March 2011

ABSTRACTWe report on the development of a new, integrable photoconductive-type detector based on low-temperature-grown GaAs. The detector has a response time of 1.2 ps and a 3-dB bandwidth of 375 GHz. The responsivity is 0.1 A/W. This is the fastest photodetector reported to date. We discuss the unique properties of this device, including its performance as functions of both light intensity and bias voltage.
Laser Quality AlGaAs-GaAs Quantum Wells Grown on Low Temperature GaAs
Authors: Hwang Y. , Zhang D. , Zhang T. , Mytych M. , Kolbas R. M. 
Published: March 2011

ABSTRACTIn this work we demonstrate that photopumped quantum wellheterostructure lasers with excellent optical quality can be grown ontop of a LT GaAs buffer layer by molecular beam epitaxy. Hightemperature thermal annealing of these lasers blue-shifts the laseremission wavelengths but the presence/absence of a LT GaAs layerhad little effect on the overall laser thresholds. Also, to first order itwas not necessary to include an AlAs barrier layer to preventadverse effects (as has been necessary in the gate stack of MESFETs to prevent carrier compensation).
The Use of Low Temperature AlInAs and GalnAs Lattice Matched to InP in the Fabrication of HBTs and HEMTs
Authors: Metzger R. A. , Brown A. S. , Wilson R. G. , Liu T. , Stanchina W. E. , Nguyen L. D. , Schmitz A. E. , McCray L. G. , Henige J. A. 
Published: March 2011

ABSTRACTAlInAs and GaInAs lattice matched to InP and grown by MBE over a temperature range of 200 to 350°C (normal growth temperature of 500°C) has been used to enhance the device performance of inverted (where the donor layer lies below the channel) High Electron Mobility Transistors (HEMTs) and Heterojunction Bipolar Transistors (HBTs), respectively. We will show that an AlInAs spacer grown over a temperature range of 300 to 350°C and inserted between the AlInAs donor layer and GaInAs channel significantly reduces Si movement from the donor layer into the channel. This produces an inverted HEMT with a channel charge of 3.0×1012 cm−2 and mobility of 9131 cm2/V-s, as compared to the same HEMT with a spacer grown at 500 °C resulting in a channel charge of 2.3×1012 cm−2 and mobility of 4655 cm2/V-s. We will also show that a GaInAs spacer grown over a temperature range of 300 to 350°C and inserted between the AlInAs emitter and GalnAs base of an npn HBT significantly reduces Be movement from the base into the emitter, thereby allowing higher Be base dopings (up to 1×1020 cm−3) confined to 500 Å base widths, resulting in an AlInAs/GaInAs HBT with an fmax of 73 GHz and ft of 110 GHz.
Low-Temperature Growth and Characterization of InP Grown by Gas-Source Molecular-Beam Epitaxy
Authors: Liang B. W. , He Y. , Tu C. W. 
Published: March 2011

ABSTRACTLow-temperature (LT) growth of InP by gas-source molecular-beam epitaxy has been studied. Contrary to GaAs, InP grown at low temperature (from 200°C to 410°C) shows ntype, low-resistivity properties. The electron concentration changes dramatically with growth temperature. A model of P antisite defects formed during LT growth was used to explain this experimental result. Ex-situ annealing can increase the resistivity, but only by a factor of about 6. Heavily Be-doped LT InP also shows n-type property. We believe this is the first report of an extremely high concentration of donors formed in LT InP and n-type doping by Be in III–V compounds.
Electron Paramagnetic Resonance Study of Low Temperature Molecular Beam Epitaxy Grown GaAs and InP Layers
Authors: von Bardeleben H. J. , Jia Y. Q. , Hirtz J. P. , Garcia J. C. , Manasreh M. O. , Stutz C. E. , Evans K. R. 
Published: March 2011

ABSTRACTThe native defects in LTMBE III-V layers have been studied by the electron paramagnetic resonance (EPR) technique for three different systems: GaAs on GaAs, GaAs on Si and InP on InP. The GaAs layers are characterised by high concentrations of ionized arsenic antisite defects(1019 cm −3), with properties similar to those of the native AsGa in amorphous GaAs. Their variation with the growth temperature, layer thickness and thermal annealings has been assessed.The results are independant on the nature of the substrate, GaAs or Si. Inspite of a 1% phosphorous excess no phosphorous antisites could be detected in the as-grown, undoped or Be doped InP layers.
Cathodoluminescence and Photoluminescence Spectroscopy Study of Low Temperature Molecular Beam Epitaxy GaAs
Authors: Viturro R. Enrique , Melloch Michael R. , Woodall Jerry M. 
Published: March 2011

ABSTRACTWe report a cathodoluminescence (CL) and photoluminescence (PL) study of molecular beam epitaxy grown GaAs at low substrate temperatures (LT GaAs), and semi-insulating LEC GaAs. The as grown LT GaAs material shows intense deep level emissions which can be associated with an excess concentration of Arsenic. These emissions subside with annealing for a few minutes at temperatures above 450 ° C. CL measurements clearly show an extremelly reduced concentration of traps in the post-growth 600 ° C annealed material. These results account for a diminished role of electronic point defects in controlling the insulative behavior of LT GaAs and strongly support the “buried” Schottky barrier model.
Annealing Characteristics Of Low Temperature Grown GaAs:Be
Authors: Bliss D. E. , Walukiewicz W. , Chan K. T. , Ager J. W. , Tanigawa S. , Haller E. E. 
Published: March 2011

ABSTRACTWe have studied the annealing characteristics of acceptor doped GaAs:Be grown at Low substrate Temperatures (300°C) by Molecular Beam Epitaxy (LTMBE). The Be was introduced in a range of concentrations from 1016 –1019 cm−3. As-grown material was found to be n-type even up to the highest Be concentration of 1019 cm−3 although Raman spectroscopy of the Be local vibrational mode indicates that the majority of the Be impurities are substitutional. We propose that Be acceptors are rendered inactive by the high concentration of AsGa-related native donor defects present. Results of slow positron annihilation studies indicate an excess concentration of VGa in LTMBE layers over bulk grown crystals. A distinct annealing stage at 500°C, similar to irradiation damaged and plastically deformed GaAs, marks a rapid decrease in the AsGa defect concentration. A second annealing stage at 800°C corresponds to the activation of Be acceptors. Analysis of isothermal annealing kinetics for the removal of AsGa-related defects gives an activation energy of 1.7 ±0.3 eV. We model the defect removal mechanism with the VGa assisted diffusion of ASGa to As precipitates.
Electrical Properties of Fine Grain Composite Carbon Films
Authors: Chen Hsiung , Dillon R. O. 
Published: March 2011

ABSTRACTWe have studied the electrical properties of boron doped composite films that consist of diamond and amorphous carbon. These films were deposited by hot filament chemical vapor deposition at a relatively high carbon/hydrogen ratio. The mixture of trimethyl borate vapor, and methane served as a source gas. The composite films had much smoother surfaces than polycrystalline diamond films.The surface morphology and average roughness were determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Raman spectroscopy and x-ray diffraction were used to analyze the structure of the films.A composite film grown with 4% methane in hydrogen had a higher resistivity than a well faceted diamond film grown at 0.5% methane. In contrast to hydrogenated amorphous carbon films which have a lower resistivity after thermal annealing, the resistivities of composite films increased by a factor of two to ten after 3 hours annealing at 600°C.
Electronic Device Fabrication Using Electron Cyclotron Resonance Etching of Boron Doped Homoepitaxial Diamond Films
Authors: Grot S.A. , Ditizio R.A. , Gildenblat G.SH. , Badzian A.R. , Fonash S.J. 
Published: March 2011

ABSTRACTWe describe the applicability of oxygen based Electron Cyclotron Resonance (ECR) etching of diamond for the purpose of fabricating electronic test structures and recessed gate field effect transistors. Boron doped homoepitaxial diamond films grown in a microwave assisted CVD reactor were used for this study. Etch rates from 8 nm/min up to 0.5 μm/min. were achieved depending on etch parameters.
Electrical Properties of Schottky Junctions on homoepitaxial flame grown diamond
Authors: Glesener J.W. , Morrish A.A. , Snail K.A. 
Published: March 2011

ABSTRACTSchottky diodes were fabricated from boron doped diamond grown in a turbulent flame. The substrates used were type IIa diamond (100) crystals 1.5 mm in diameter and.25 mm thick. A p/p+ structure was deposited using the p+ layer as an ohmic contact. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were made on the finished devices. An ideality factor of 1.8 was obtained from the I-V characteristics. Doping levels from C-V measurements indicate an acceptor concentration on the order of 5 × 1017/cm3.
Stoichiometry Control of Compound Semiconductors
Authors: Nishizawa Jun-Ichi , Suto Ken , Oyama Yutaka 
Published: March 2011

ABSTRACTVapor pressure control technology is successfully applied to the bulk crystal growth, epitaxial growth and diffusion process of ZnSe crystals. Surface morphology and the crystal quality are investigated by the optical microscope and the X-ray double crystal diffractometry as the function of the growth temperature and the applying Zn vapor pressure. The cathode luminescence is also measured to evaluate the optical properties and the effect of low temperature growth and the application of Zn vapor pressure are demonstrated, p-type ZnSe crystals are grown from the Se solution with group Ia element as a dopant under controlled Zn vapor pressure, p-n junction diodes are also prepared by the Ga diffusion from Zn solution under Se vapor pressure. Emission spectra from the p-n junction and its Zn and Se vapor pressure dependencies are also presented.
Initial Stages of Growth of ZnSe on Si
Authors: Bringans R. D. , Biegelsen D. K. , Swartz L.-E. , Ponce F. A. , Tramontana J. C. 
Published: March 2011

ABSTRACTZinc selenide films have been grown heteroepitaxially on Si(100) substrates by molecular beam epitaxy. The initial stages of growth are dominated by the reaction of Se and Si atoms to form the compound SiSe2- The compound formation disrupts epitaxy, and several growth methods which avoid this are described and compared. We find that room temperature deposition plus solid phase epitaxy does not lead to significant SiSex formation and yields uniformly thick films which are misoriented with respect to the substrate and contain large regions of twinned ZnSe. The use of an As monolayer on the Si surface before the start of ZnSe growth allows good ZnSe epitaxy without any Si-Se reaction or any misorientation. ZnSe films have also been used as interlayers for GaAs growth on Si. This has allowed us to obtain uniform GaAs films at thicknesses which typically manifest a coalesced island morphology for GaAs grown directly on Si.
In-Situ Spectroscopic Ellipsometry Applied to ZnSe and ZnCdSe Growth Process in Organometallic Vapor Phase Epitaxy
Authors: Iacoponi J. , Bhat L. B. , Johs B. , Woollam J.A. 
Published: March 2011

ABSTRACTSpectroscopie ellipsometry is a well developed technique for studying the semiconductor materials and heterostructures. Here, we have applied this technique to in-situ studies of ZnSe and ZnCdSe growth in a low pressure organometallic vapor phase epitaxy system. The growth of ZnSe on GaAs was studied using a light source in the range 2 to 4 eV, and film thickness of a few tens of angstroms could be monitored by this technique. The band gap and the composition of Zn1-χCdχSe could also be measured as a function of real time. It was found that, for a gas phase DMCd composition of 60%, the amount of Cd incorporated in the layers is less than 25%. Spectroscopie ellipsometry is demonstrated to be a valuable technique for in-situ monitoring of semiconductor growth in organometallic vapor phase epitaxy systems.
Characteristics of ZnSe Layers Grown on Zn-Stabilized and Se-Stabilized GaAs Substrates
Authors: Akram S. , Ehsani H. , Bhat L. B. , Ghandhi S.K. 
Published: March 2011

ABSTRACTOrganometallic vapor phase epitaxial (OM VPE) growth of ZnSe on GaAs was carried out using dimethylzinc (DMZn) and dimethylselenium (DMSe) as source precursors. The growth of ZnSe can be initiated either by introducing DMZn first (Zn stabilized) or DMSe first (Se stabilized).A systematic study of this growth initiation step on the properties of ZnSe epilayers was carried out using Photoluminescence (PL) and Double Crystal X-Ray Diffraction (DCD) in order to optimize the ZnSe-GaAs interface. PL and DCD data show a considerable difference in lattice relaxation mechanism between Zn and Se stabilized layers. Se stabilized layers are also seen to be considerably tilted with respect to the substrate. PL properties of Se stabilized layers exhibit strong near band edge emission (NBE) and weak deep level emission such as Y0, compared to layers grown by Zn stabilization.
Vapor-Phase Growth of Epitaxial and Bulk ZnSe
Authors: Ahlgren W. L. , Sen S. , Johnson S. M. , Konkel W. H. , Vigil J. A. , Ruth R. P. 
Published: March 2011

ABSTRACTEpitaxial and bulk ZnSe of good structural perfection have been grown by vapor-phase techniques. Epitaxial undoped ZnSe layers were grown by metal-organic chemical vapor deposition (MOCVD) on GaAs {100} substrates in a horizontal-flow quartz reactor chamber. Conventional pyrolytic growth at 450°C was used, with diethyl zinc (DEZn) and diethyl selenium (DESe) reactants transported in hydrogen carrier gas.Layers with smooth surface morphology and very good crystal structure were obtained, with no evidence of gas-phase pre-reaction. Sharp electron channeling patterns produced in the scanning electron microscope (SEM) indicated that {100}-oriented ZnSe layers were grown on (100) GaAs surfaces, as expected. X-ray rocking-curve analysis with a silicon four-crystal monochrom-ator gave full-width at half-maximum (FWHM) line widths of 165 to 180 arc-sec for layers 2.5 to 3.0 μm thick, better than values for MOCVD-grown ZnSe/GaAs reported to date in the literature known to us. Cathodoluminescence (CL) imaging in the SEM showed significant defect substructure in the layers, probably due to lattice-misfit dislocations in the interface region. Bright blue CL emission from the layers was observed in the SEM at both 77K and room temperature, indicating the dominance of radiative recombination in the material.Bulk ZnSe crystals were grown using a physical vapor transport technique. The crystals, a few millimeters on a side, had fully developed crystal facets, predominantly {110(-oriented. X-ray rocking-curve analysis gave FWHM values of about 19 arc-sec, indicating excellent structural perfection.
Optical Study of the CdTe Crystals in Far Infrared Region at Temperatures (5 – 500)K
Authors: Belogorokhov A.I. 
Published: March 2011

ABSTRACTThe semiconductors of zinc blend structure are promising candidate materials for numerous experimental and theoretical investigations. In recent years, considerable effort has been made to study the lattice infrared absorption spectrum of II-VI compounds, renewed interest has been taken in CdTe owing to its relatively high electro - optic coefficient in the near infrared. In addition, its nonlinear response to two-phonon absorption in the infrared region is of interest because the material is transparent in this spectral region.
First-Principles Investigations of Acceptors in ZnSe
Authors: Van De Walle Chris G. , Laks D. B. 
Published: March 2011

ABSTRACTWe present a theoretical formalism to investigate doping efficiencies of impurities in semiconductors, and show results for various acceptor impurities (Li, Na and N) in ZnSe. These results, obtained from first-principles calculations, yield important insights in the mechanisms that govern impurity formation energies and solubilities.
Potential Energy Surfaces and Stability of O in Elemental and Compound Semiconductors
Authors: Estreicher S. K. , Roberson M. A. , Chu C. H. , Solinsky J. 
Published: March 2011

ABSTRACTPotential energy surfaces and electronic structures of interstial oxygen (Oi) in cubic C, Si, AIP, SiC, and BN have been calculated. The equilibrium site is a bent-bridged bond. In compound semiconductors, Oi has a larger degree of bonding with the most electronegative of the host atoms (P, C, or N) than with the least electronegative one. In addition to the barrier for rotation of O, about the < 111 > axis, which does not involve breaking a bond, we calculated the barriers for migration between adjacent bond-centered sites. There are two such barriers in compound semiconductors. In order to estimate the relative stability of Oi in the various hosts, we calculated the energies involved in inserting O2 into the lattice and dissociating it into two isolated Oi's.
Optical and Electronic Properties of the Nitrides of Indium, Gallium and Aluminium and the Influence of Native Defects
Authors: Tansley T. L. , Egan R. J. 
Published: March 2011

ABSTRACTThe nitrides of Al, Ga and In are III-V compound semiconductors with properties more closely akin to those of the II-VI system and applications problems of similar type. All three have wide, direct band gaps and relatively light, therefore mobile, electrons. Less encouragingly, native point defects appear to play a significant role in both optical and electronic properties.Both experiment and theory point to a triplet of donor states associated with the nitrogen vacancy, with deep compensating centres deriving from antisite defects. The ionic radius of the metal then seems to determine the conductivity of as-grown material, indium is reluctant to occupy nitrogen sites while aluminium does so readily and gallium is equivocal. Thus the upper donor level of InN is not depleted and n-type behaviour is always observed, the equivalent level in AIN is always overcompensated and the remaining donor levels are too deep to contribute free electrons at normal temperatures so that the material is consistently insulating. GaN may be n-type or semi-insulating since compensation ratios either side of unity appear to be possible, depending on the method of growth.In this paper we review the evidence, both optical and electrical, for the existence, nature and energetic location of the four basic point defects in each nitride, noting in particular that all four broad luminescence bands in GaN:Zn can be accounted for by the presence of nitrogen on gallium sites and of nitrogen vacancies.
A Comparative Study of GaN Films Grown on Different Faces of Sapphire by ECR-Assisted MBE
Authors: Moustakas T. D. , Molnar R. J. , Lei T. , Menon G. , Eddy C. R. 
Published: March 2011

ABSTRACTGaN films were grown on c-plane (0001), a-plane (1120) and r-plane (1102) sapphire substrates by the ECR-assisted MBE method. The films were grown using a two-step growth process, in which a GaN buffer is grown first at relatively low temperatures and the rest of the film is grown at higher temperatures. RHEED studies indicate that this growth method promotes lateral growth and leads to films with smooth surface morphology. The epitaxial relationship to the substrate, the crystalline quality and the surface morphology were investigated by RHEED, X-ray diffraction and SEM studies.