bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Diffraction Studies of Low Temperature GaAs
Authors: Kowaljki G. , Leszcjynski M. , Kurpiewski A. , Kaminska M. , Suski T. , Weber E. R. 
Published: March 2011

ABSTRACTGaAs layers grown by molecular beam epitaxy (MBE) at low substrate temperatures (LT GaAs) were studied in a novel purpose designed X-ray experiment. It combines X-ray double crystal rocking curve measurements with some elements usually found in optical setups like light illumination at liquid nitrogen temperatures applied to transfer EL2 type defects into metastable state. Ability to record such transfers with the X-ray experiment as well as large lattice relaxation accompanying this process is presented.
An Investigation on the Lattice Site Location of the Excess Arsenic Atoms in GaAs layers Grown by Low Temperature Molecular Beam Epitaxy
Authors: Yu Kin Man , Liliental-Weber Z. 
Published: March 2011

ABSTRACTWe have measured the excess As atoms present in GaAs layers grown by molecular beam epitaxy at low substrate temperatures using particle induced x-ray emission technique. The amount of excess As atoms in layers grown by MBE at 2000C were found to be ∼4×1020 cm−2. Subsequent annealing of the layers under As overpressure at 600'C did not result in any substantial As loss. However, transmission electron microscopy revealed that As precipitates (2- 5nm in diameter) were present in the annealed layers. The lattice location of the excess As atoms in the as grown layers was investigated by ion channeling methods. Angular scans were performed in the <110> axis of the crystal. Our resutls strongly suggest that a, arge fraction of these excess As atoms are located in an interstitial position close to an As row. These As “intersitials” are located at a site slightly displaced from the tetrahedral site in a diamond cubic lattice. No interstitial As signal is observed in the annealed layers.
Study of Modulation in GaAs Misfets with LT-GaAs as a Gate Insulator
Authors: Yin L.-W. , Ibbetson J. , Hashemi M. M. , Jiang W. , Hu S.-Y. , Gossard A. C. , Mishra U. K. 
Published: March 2011

ABSTRACTDC characteristics of a GaAs MISFET structure using low-temperature GaAs (LTGaAs) as the gate insulator were investigated. MISFETs with different gate to channel separation (d) were fabricated. The dependence of four important device parameters such as gate-drain breakdown voltage (VBR), channel current at zero gate bias (Idss), transconductance (gm), and gate-drain turn-on voltage (Von) on the gate insulator thickness were analyzed. It was observed that (a) in terms of Idss and gin, the LT-GaAs gate insulator behaves like an undoped regular GaAs layer and (b) in terms of VBR and Von, the LT-GaAs gate insulator behaves as a trap dominated layer.
Electrical Characterization of Low Temperature GaAs Layers, and Observation of the Extremely Large Carrier Concentrations in Undoped Material
Authors: Tadayon Bijan , Fatemi Mohammad , Tadayon Saied , Moore F. , Dietrich Harry 
Published: March 2011

ABSTRACTWe present here the results of a study on the effect of substrate temperature, Ts, on the electrical and physical characteristics of low temperature (LT) molecular beam epitaxy GaAs layers. Hall measurements have been performed on the asgrown samples and on samples annealed at 610 °C and 850 °C. Si implantation into these layers has also been investigated.
Molecular Beam Epitaxy of Low Temperature Grown GaAs Photoconductors
Authors: Dykaar D. R. , Eaglesham D. J. , Keil U. D. , Greene B. I. , Saeta P. N. , Pfeiffer L. N. , Kopf R. F. , Darack S. B. , West K. W. 
Published: March 2011

ABSTRACTWe report on the characterization of Low Temperature (LT) epitaxial growth of GaAs photoconductors. Samples were characterized using electro-optic sampling, transient femtosecond reflectivity, transmission electron microscopy, and pulsed terahertz spectroscopy as a function of growth temperature, As4 flux, doping and anneal conditions. We find the strongest effect on pulsewidth to be the temperature of an ex-situ rapid thermal anneal. In addition we find evidence of a temperature threshold for As precipitation. For more than an order of magnitude change in As precipitate density we find no corresponding change in electrical pulsewidth. Doping to 1017/cm3 also produces no change in the measured electrical response.
InP Layers Grown by Molecular Beam Epitaxy at Low Substrate Temperature
Authors: Xie K. , Wie C. R. , Wicks G. W. 
Published: March 2011

ABSTRACTInP layers were grown on semi-insulating InP wafer by molecular beam epitaxy (MBE) at low substrate temperatures (<200° C), using solid phosphorus source. We use x-ray diffraction, double crystal x-ray rocking curve, Auger electron spectroscopy, and temperature-dependent Van der Pauw and Hall effect measurements to characterize the as-grown and annealed InP layers. It is found that the InP layer is in poly-crystal state with excess P over 7 at%. The layers became single crystal after annealing above 400°C. The resistivity of the InP layer decreased from 60 Ωcm for an as-grown sample to 0.82 Ωcm after 400°C RTA annealing. The different role of excess P as compared to the role played by excess As in LT-GaAs is discussed based on the P properties.
Growth and Characterization of Low Temperature InP by Gas Source MBE
Authors: Maracas G. N. , Shiralagi K. T. , Puechner R. A. , Yu F. , Choi K. T. , Bow J. S. , Ramamurti R. , Kim M. J. , Carpenter R. W. 
Published: March 2011

The introduction of GaAs grown at low MBE growth temperatures has spurred considerable activity in attempts to understand conduction mechanisms and optical properties. In LT GaAs, the formation of microscopic As precipitates dominates the conductivity, producing electronic transport mainly by variable range hopping conduction. The resulting high resistivity and short carrier lifetimes have enabled the use of LT GaAs in FET buffer layers as well as in ultra-fast optical switches. An extension to AlInAs has also been performed and it was seen that variable range hopping is also present in the Asbased ternary.We report the optical and electronic properties of InP grown at low temperatures in a gas source MBE using dimeric phosphorus produced from cracked phosphine. The conductivity is higher than the equivalent GaAs LT material and does not have the same temperature dependence. The conditions under which growth occurs ie, substrate temperatures, V/ill ratios and annealing is explored. The structural properties, temperature dependence of the conductivity, deep level structure and the photoluminescence properties of the material are also investigated.
Device Applications of Low-Temperature-Grown GaAs
Authors: Smith Frank W. 
Published: March 2011

ABSTRACTLow-temperature-grown (LTG) GaAs is a unique material that has been used in a variety of device applications to achieve record performance. LTG GaAs used as a buffer layer eliminates sidegating and backgating and in GaAs integrated circuits. Record output power density (1.57 W/mm) and superior microwave-switch performance were demonstrated when LTG GaAs was used at a gate insulator in a metal-insulator-semiconductor field-effect transistor. High-speed (0.5 ps) and high-voltage (1 kV) LTG GaAs photoconductive switches have also been demonstrated. Using the same material, researchers have demonstrated highresponsivity (0.1 A/W), wide-bandwidth (∼ 375 GHz) LTG GaAs photodetectors. Devices incorporating LTG GaAs are currently being optimized for systems applications. LTG GaAs technology can enhance system performance and enable new systems for military and commercial applications in the areas of radar, communications, instrumentation, and highspeed computing.
Transport Modeling and Compensation Mechanism for Semi-Insulating LT-Gaas and InP: Cu
Authors: Xie K. , Wie C. R. 
Published: March 2011

ABSTRACTThe compensation mechanism and transport properties of annealed GaAs grown by molecular beam epitaxy at low substrate temperature (LT-GaAs) and Cu diffused InP are analyzed by using a deep donor band model and a precipitate model. It was found that the compensation in highly resistive LT GaAs can not be explained by the precipitate model alone, and therefore a high donor density had to be considered. In Cu diffused InP, the precipitate model gives a consistent explanation for the observed carrier compensation and mobility data. For both semi-insulating LT-GaAs and fully-compensated, lightly-doped InP:Cu, the neutral impurity scattering was found to be a major carrier scattering mechanism.
Insulating and Breakdown Characteristics of Low Temperature GaAs
Authors: Grubin H. L. , Kreskovsky J. P. , Levy R. 
Published: March 2011

ABSTRACTThe electrical characteristics of an N(LT)N structure are studied through implementation of numerical simulation techniques for the case of donor traps 0.83 ev below the conduction band and acceptor traps 0.3 ev above the valence band. The results show characteristics sensitive to the relative densities of the traps. In particular, high acceptor trap / low donor trap concentrations generally result in low breakdown voltages, whereas high acceptor / high donor concentrations result in higher breakdown voltages.
Defects in Low-Temperature-Grown MBE GaAs as Studied by a Variation of TSC Spectroscopy
Authors: Fang Z-Q , Look D. C. 
Published: March 2011

ABSTRACTA zero-bias thermally stimulated current (TSC) spectroscopy under both optical (1.96eV) and electrical excitation using samples with a Schottky contact on the top was applied to annealed LTMBE GaAs grown at different temperatures, and bulk SI GaAs with different stoichiometries. The results show that: 1) the new TSC technique is capable of revealing the traps at 235K<T<380K and is effective in indicating the crystal stoichiometry of bulk SI GaAs; 2) the driving force for the currents under a zero-bias comes from the builtin surface field as well as a thermal gradient; 3) the trap species in the annealed LTMBE GaAs samples and the annealed control SI GaAs sample are similar, especially for TA(0.79eV), Ta (0.33eV), T4 (0.29eV), and T6*(0.16eV); and 4) the trap densities in LTMBE samples are higher than those in the control samples and are dependent on the MBE growth temperature.
Growth Technique For Large Area Mosaic Diamond Films†
Authors: Pryor R. W. , Geis M. W. , Clark H. R. 
Published: March 2011

ABSTRACTA new technique has been developed to grow semiconductor grade diamond substrates with dimensions comparable to those of currently available Si wafers. Previously, the synthetic single crystal diamond that could be grown measured only a few millimeters across, compared with single crystal Si substrates which typically are 10 to 15 cm in diameter. In the technique described, an array of features is first etched in a Si substrate. The shape of the features matches that of inexpensive, synthetic faceted diamond seeds. A diamond mosaic is then formed by allowing the diamond seeds to settle out of a slurry onto the substrate, where they become fixed and oriented in the etched features. For the experiments reported, the mosaic consists of seeds ∼ 100 μm across on 100 μm centers. A mosaic film is obtained by chemical vapor deposition of homoepitaxial diamond until the individual seeds grow together. Although these films contain low angle (<1°) grain boundaries, smooth, continuous diamond films have been obtained with electronic properties substantially better than those of polycrystalline diamond films and equivalent to those of homoepitaxial single crystal diamond films. The influence of growth conditions and seeding procedures on the crystallographic and electronic properties of these mosaic diamond films is discussed.
Polycrystalline Diamond Film Resistors
Authors: Edwards L. M. , Davidson J. L. 
Published: March 2011

ABSTRACTThe technology to fabricate polycrystalline diamond film resistors has been initiated using modified thick film patterning techniques andin situsolid source doping.Doping of polycrystalline diamond films in microwave plasma CVD systems has been achieved historically through use of diborane gas, which may contaminate the deposition system causing all diamond films thereafter to be doped p-type. We have attempted noncontaminatingin situdoping utilizing two solid source dopants, and have met with preliminary success.The more effective source (B2O3) produces a fairly even dopant concentration across the substrate, with sheet resistances ranging from 800 ohms per square to 4500 ohms per square. The other source (BN) showed significant doping in a narrow band surrounding the source, but the doping concentration decreased rapidly with distance from the source. Films grown afterwards with no doping were evaluated through resistance measurements; no evidence of doping contamination was observed.
Growth and Characterization of ZnSe/ZnCdSe Diode Structures on (In, Ga)As Buffer Layers
Authors: Hua G. C. , Otsuka N. , Xie W. , Grillo D. C. , Kobayashi M. , Gunshor R. L. 
Published: March 2011

ABSTRACTZnSe/ZnCdSe diode structures were grown on (In, Ga)As buffer layers by molecular beam epitaxy. Lattice distortions and defect distributions in buffer layers and diode structures were examined by X-ray diffraction and transmission electron microscopy. Diode structrues with low dislocation densities were obtained by the growth on tetragonally distorted In0.043 Ga0.957 buffer layers, the lattice spacing of which is slightly smaller than that of ZnSe.
MBE Growth and Properties of Wide Band-Gap II-VI Strained-Layer Superlattice
Authors: Wang Hailong , Cui Jie , Shen Aidong , Xu Liang , Chen Yunliang , Shen Yuhua 
Published: March 2011

ABSTRACTThe (ZnSe) /(ZnS ), strained layer super-lattices (SLSs) on (100) GaAs and (ZnTe)/(ZnSe) SLSs on (100) InP have been grown by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE). The structural characteristics of these SLSs were investigated in situ RHEED observation, low-angle X-ray diffraction spectra, TED image and AES analysis. The optical properties of the SLSs, such as refractive index of superlattice materials, photoluminescence (PL) spectra, transient PL spectra, Raman spectra, far-infrared reflectivity spectra and Optical nonlinear have been studied.
Excimer Laser Melting of MBE-ZnSe
Authors: Padmapani Nallan C. , Yi G. -J. , Neumark G. F. , Lu Z. , Chang C. C. , Tamaargo M. C. 
Published: March 2011

ABSTRACTIt has. generally been concluded that good doping in wide-gap semiconductors is best accomplished by non-equilibrium means. Excimer lasers, because of their high intensity and short pulses, are ideal for this. Our earlier laser annealing work on bulk ZnSe resulted in complications due to increased twinning of the sample. Our present work shows that twinning can be eliminated by the use of originally untwinned MBE material. The MBE samples had the additional advantage, over bulk, of a far smoother surface, which simplified the investigation of melting and evaporation. Use of power levels of 10, 20, and 35 MW/cm2 showed no melting at 10 MW/cm2, melting and no detectable evaporation at 20 MW/cm2, and evaporation at 35 MW/cm2. Combined ion beam cratering and SEM examination showed a depth of the melted layer, at 20 MW/cm2, of - 0.5 μm. Moreover, AES analysis showed minimal decomposition of the 20 MW/cm2 sample.
On the Burste In-Moss Shift in Quantum Confined Wide-Band Gap Semiconductors
Authors: Ghatak Kamakhya P. , De Badal 
Published: March 2011

ABSTRACTWe study the Burstein-Moss shift (BMS) in quantum wiies and quantum dots of wide-gap semiconductors, taking Ge as an example, it is found that the BMS increases with increasing electron concentration in a ladder like manner. The numerical values of the BMS is greatest in quantum dots and least in quantum wells. The theoretical analysis is in agreement with the experimental results as given elsewhere.
Characterization of AlXGa1-xN Grown by MOCVD at Low Temperatures
Authors: Yu Z. J. , Sywe B. S. , Edgar J. H. 
Published: March 2011

ABSTRACTThe low temperature deposition (400–650° C) of AlxGa1-xN films by metalorganic chemical vapor deposition (MOCVD) was characterized. Triethylgallium (TEG), trimethylaluminum (TMA), and ammonia (NH3) served as the precursors and both sapphire and silicon as the substrates with helium as the carrier gas. The deposition was operated at the atmospheric pressure. The crystallinity was improved even at low temperatures when AlxGal-xN was grown on a thin buffer layer of A1N at 400° C. With an AlxGa1-xN/AIN layered structure, epitaxial growth of AlxGa1-xN was obtained at 650° C on sapphire substrates. Auger results showed that the Al fraction x was less than 0.1. X-ray diffraction indicated a strong peak at 2θ =34.9 degrees for the (0002) planes from the film on sapphire substrates. The electron channelling pattern (ECP) of the film produced at 650° C revealed a 6 fold symmetry contrast pattern indicating the epitaxial growth of the film. Photoluminescence (PL) showed a dominant emission at 353 nm for the film on sapphire substrate. Surface morphology examined by SEM was featureless for the film produced at 500° C, while a relatively rough surface can be seen on the film produced at 650° C (5, 000x). The band gap was measured as 3.56 eV. The Al mole fraction x in the alloy was observed to be lower than that in the gas phase.
Low Temperature Preparation of Gallium Nitride Thin Films
Authors: Gordon Roy G. , Hoffman David M. , Riaz Umar 
Published: March 2011

ABSTRACTGallium nitride thin films were prepared by atmospheric pressure chemical vapor deposition from hexakis(dimethylamido)digallium, Ga2(NMe2)6, and ammonia precursors at substrate temperatures of 100–400 °C with growth rates up to 1000 Å/min. The films were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry and forward recoil spectrometry. The N/Ga ratio varied from 1.05 for films deposited at 400 °C to 1.5 at 100 °C. The hydrogen concentration increased from 10 atom % for films deposited at 400 °C to 24 atom % at 100 °C. Films deposited at 100 °C were amorphous but films deposited at higher temperatures were polycrystalline. Bandgaps of the films varied from 3.8 eV for films deposited at 400 °C to 4.2 eV at 100 °C.
An Investigation of Light Induced Defects in Aluminum Nitride Ceramics
Authors: Harris J. H. , Youngman R. A. 
Published: March 2011

ABSTRACTIt has been observed that aluminum nitride (AIN) ceramics exhibit a significant photo-darkening when exposed to UV or X-ray radiation, though the origin of this effect has never been understood. In this study, the optical character of these defects is investigated utilizing a UV-pump, visible-probe arrangement, where very large changes ΔT in the probe transmission T (induced absorption) are observed after excitation (Δ/T-0.60). These experiments reveal that the photo-darkening is due to the creation of light induced defects, with an energy level deep in the AIN bandgap. Utilizing these results, a light induced defect formation model is proposed which is consistent with the known defect chemistry of this material.
Crystalline Growth of Wurtzite GaN on (111) GaAs
Authors: Ross J. , Rubin M. , Gustafson T. K. 
Published: March 2011

ABSTRACTGallium Nitride films were grown on (111) Gallium Arsenide substrates using reactive rf magnetron sputtering. Despite a 20% lattice mismatch and different crystal structure, wurtzite GaN films grew epitaxially in basal orientation on (111) GaAs substrates. Heteroepitaxy was observed for growth temperatures between 550–600°C. X-ray diffraction patterns revealed (0002) GaN peak with a full-width-half-maximum (FWHM) as narrow as 0.17°. Possible surface reconstructions to explain the epitaxial growth are presented.
Structrual Characterization and Raman Scattering of Epitaxial Aluminum Nitride Thin Films on Si(111)
Authors: Meng W. J. , Perry T. A. , Heremans J. , Cheng Y. T. 
Published: March 2011

ABSTRACTThin films of aluminum nitride were grown epitaxially on Si(111) by ultra-high-vacuum dc magnetron reactive sputter deposition. Epitaxy was achieved at substrate temperatures of 600° C or above. We report results of film characterization by x-ray diffraction, transmission electron microscopy, and Raman scattering.
Tem Study of Dislocations in Plastically Deformed AlN
Authors: Audurier V. , Demenet J. L. , Rabier J. 
Published: March 2011

ABSTRACTAlN ceramics were plastically deformed using uniaxial compression under hydrostatic pressure between room temperature (RT) and 800°C. Deformation microstructures have been studied by Transmission Electron Microscopy (TEM) using the weak beam technique. The deformation substructure at RT is characterized by perfect glide loops with 1/3<1120> Burgers vector in (0001) elongated in the screw direction. When deformation temperature increases, the screw character is associated to cross slip events and dislocation dipolesare found. In the investigated temperature range, slip of dislocations with 1/3<1120> Burgers vector is also evidenced on prismatic planes. Weak beam observations failed to evidence any dislocation splitting. Some of these dislocation properties, similar to those of III-V compound semiconductors, suggest that electronic doping effects could be used to control plastic behaviour of covalent ceramics.
Temperature Dependence of Optical Properties of AlAs, Studied by In Situ Spectroscopic Ellipsometry
Authors: Yao Huade , Snyder Paul G. , Stair Kathleen , Bird Thomas 
Published: March 2011

ABSTRACTThe dielectric functions ε = ε1+iε2 of AlAs were determined from 1.5 eV to 5.0 eV, by spectroscopie ellipsometry (SE), from room temperature (RT) to ∼577 °C in an ultrahigh vacuum (UHV) chamber. Molecular beam epitaxy (MBE)-grown AlAs was covered by a thin GaAs layer, which was passivated by arsenic capping to prevent oxidation. The arsenic cap was desorbed inside the UHV chamber. SE measurements of the unoxidized sample were made, at various temperatures. Temperature dependent optical constants of AlAs were obtained by mathematically removing the effects of the GaAs cap and substrate. Quantitative analyses of the variations of critical-point energies with temperature, by using the harmonic oscillator approximation (HOA), indicate that the E1 and E1+Δ1 energies decrease -350 meV as temperature increases from RT to 500 °C.
Epitaxial Monocrystalline SiC Films Grown on Si by Low-Pressure Chemical Vapor Deposition at 750°C
Authors: Golecki I. , Reidinger F. , Marti J. 
Published: March 2011

ABSTRACTMonocrystalline, epitaxial cubic (100) SiC films have been grown on monocrystalline (100) Si substrates at 750°C, the lowest epitaxial growth temperature reported to date. The films were grown by low-pressure chemical vapor deposition, using methylsilane, SiCH3H3, a single precursor with a Si:C ratio of 1:1, and H2. The films were characterized by means of transmission electron microscopy, single- and double-crystal X-ray diffraction, infra-red absorption, ellipsometry, thickness measurements, four-point probe measurements, and other methods. Based on X-ray diffractometry, the crystalline quality of our films is equivalent to that of commercial films of similar thickness. We describe the novel growth apparatus used in this study and the properties of the films.
Evaluation of Silicon Carbide Formed with a Single Precursor of Di-Tert-Butylsilane
Authors: Tay Sing-Pin , Ellul J. P. , Hewitt Susan B. , Tarr N. G. , Boothroyd A. R. 
Published: March 2011

ABSTRACTA low temperature process of silicon carbide deposition using the pyrolysis of di-tert-butylsilane has been explored for formation of emitter structures in silicon heterojunction bipolar transistors. Near stoichiometric amorphous silicon carbide films were achieved at 775°C. Doping and annealing of these films resulted in resistivity as low as 0.02 ohm-cm.
Stress-Induced Polytypic Transformation in Sic
Authors: Yang J. W. , Suzuki T. , Pirouz P. , Powell J. A. , Iseki T. 
Published: March 2011

ABSTRACTDeformation experiments were carried out on 6H-SiC single crystals and the deformed samples were examined by electron-optical techniques to verify any evidence for stress-induced polytypic transformation.