bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Contact, Wafer-Scale Deep Level Transient Spectroscopy (DLTS) Based on Surface Photovoltage (SPV)
Authors: Lagowski Jacek , Morawski Andrzej , Edelman Piotr
Published: March 2011

We present a new version of a deep level transient spectroscopy which is suitable for non-contact, non-destructive determination of deep level defects in semiconductor wafers without preparation of metal-semiconductor diodes or p-n junctions.

The method relies on deep level thermal emission measurements by the surface photovoltage (SPV) transient following an optical filling pulse. Non-equilibrium occupation of deep levels is realized within the native surface depletion region by the capture of excess minority carriers. Since the native Schottky-type surface barrier is commonly present on semiconductor surfaces, the approach requires no wafer pre-treatments. Non-contact SPV measurements are realized using a capacitive coupling to the wafer front and the wafer back.

The quantitative principles of the SPV-DLTS approach are discussed using experimental data obtained on GaAs.
Investigation of Multilayer Systems for Optical Bragg Reflectors by X-ray Double Crystal Topography and - DIF-Fractometry
Authors: Jenichen B. , Köhler R. , Hey R. , Höricke M.
Published: March 2011

Optical Bragg reflectors consisting of the binaries AlAs and GaAs were investigated using double crystal topography and diffractometry. In undoped mirror stacks stress relaxation due to the formation of misfit dislocations was observed, which could be prevented by doping the stacks with 1018cm−3 silicon. In topographs taken in the substrate and different satellite reflections an unusual vanishing of the contrast of different segments of the misfit dislocations takes place, that shows these different segments to be located at different levels of the stack. The contrasts of the threading dislocations are quite similar in the substrate and the satellite reflections whereas the misfit dislocations change their contrast markedly.
Rare-Earth Doped In1−xGaxP Prepared by Metalorganic Vapor Phase Epitaxy
Authors: Neuhalfen A. J. , Wessels B. W.
Published: March 2011

The dependence of the luminescent properties of rare-earth impurities on the band structure of the host compound semiconductor has been investigated. Photoluminescence spectroscopy was used to characterize the optical properties of rare-earth doped Ini1−xGaxP layers prepared by metalorganic vapor phase epitaxy as a function of alloy composition. Thermal quenching of the Er3+, Yb3+, and Tm3+ related emission was observed over the temperature range of 15K to 360K with activation energies that depended on the alloy composition. From measurements of the thermally activated luminescence quenching, the energy levels of the isovalent erbium, ytterbium, and thulium in the alloys were determined. The variation of the position of the rare-earth related energy levels in the host semiconductor is explained in terms of a vacuum referred binding energy model that should have general applicability to other rare-earth doped semiconductor systems.
Optical Anisotropy in a GaAs/AlAs Quantum Wire Array Grown on Vicinal Substrate
Authors: Kanbe H. , Chavez-Pirson A. , Kumagai M. , Saito H. , Fukui T.
Published: March 2011

The optical properties of a quantum wire array which was successfully realized in a 4-nm-thick (GaAs)1/2 (AlAs)1/2 fractional-layer superlattice (FLS) are described. The FLS sample was grown by metalorganic chemical vapor deposition on a (001) vicinal GaAs substrate tilted 2 ° towards [110]. The nominal cross sectional size of the GaAs wires is 4×4 nm. Optical anisotropy in absorption, refractive index and photoluminescence was clearly observed by polarization spectroscopy at room temperature as well as lower temperatures.
Dry Etch Damage in GaAs P-N Junctions
Authors: Pearton S. J. , Ren F. , Abernathy C. R. , Fullowan T. R. , Lothian J. R.
Published: March 2011

GaAs p-n junction mesa-diode structures were fabricated so that both n- and p-type layers could be simultaneously exposed to either O2 or H2 discharges. This simulates the ion bombardment during plasma etching with either CCl2F2/O2 or CH4/H2 mixtures. The samples were exposed to 1 mTorr discharges for period of 1–20 min with DC biases of -25 to -400V on the cathode. For O2 ion bombardment, the collector resistance showed only minor (≤10%) increases for biases up to -200 V and more rapid increases thereafter. In our structure, this indicates that bombardment-induced point defects penetrate at least 500 Å of GaAs for ion energies of ≥200eV. The base resistance displayed only a minor increase (∼10%) over the pre-exposure value even for O+ ion energies of 375 eV, due to the very high doping (1020 cm−3 ) in the base. More significant increases in both collector and base resistances were observed for hydrogen ion bombardment due to hydrogen passivation effects. We will give details of this behaviour as a function of ion energy, plasma exposure time and post-treatment annealing temperature.
Raman Spectroscopy Study of Damage in n+ - GaAs Introduced by H2 and CH4/H2 RIE
Authors: De Wolf I. , Van Hove M. , Pereira R.-G. , Van Rossum M. , Maes H. E. , Münder H.
Published: March 2011

Raman spectroscopy is used to study crystal damage and electrical damage in n+-GaAs produced by reactive ion etching (REE). H2 RIE is compared with CH4/H2 RIE and the effect of temperature annealing is studied. The results are compared with C-V analysis. It is found that structural damage introduced by RIE in the surface layers of the sample is larger for the H2 plasma than for the CH4/H2 plasma. Annealing results in a decrease of this structural damage. H2 RIE as well as CH4/H2 RIE cause an increase of the inactive surface region. This increase is found to be larger for the H2 RDE. C-V experiments show that annealing results in a reactivation and associated decrease of the width of the inactive region.
Fermi Level Effects on Dislocation Formation in InAs1−xSbx Grown by MOCVD
Authors: Biefeld R. M. , Drummond T. J.
Published: March 2011

Dislocation formation in InAs1−xSbx buffer layers grown on InSb substrates by metal-organic chemical vapor deposition is shown to be reproducibly enhanced by p-type doping at levels exceeding the intrinsic carrier concentration at the growth temperature. To achieve a carrier concentration greater than 2 × 1018 cm−3, the intrinsic carrier concentration of InSb at 475 C, p-type doping with diethylzinc was used. Carrier concentrations up to 6 × 1018 cm−3 were obtained. The zinc doped buffer layers have proven to be reproducibly crack free for InAs1−xSbx step graded buffer layers with a final composition of x = 0.12 lattice matched to a strained layer superlattice (SLS) with an average composition of x = 0.09. These structures have been used to prepare infrared photodiodes. Details of the buffer layer growth, an explanation for the observed Fermi level effect and the growth and characterization of an infrared photodiode are discussed.
Theory of Schottky-Contact Formation on GaAs (110)
Authors: Kahen K. B.
Published: March 2011

A phenomenological theory of Schottky contact formation to GaAs (110) surfaces at room temperature is discussed. The theory splits into two regimes, low- and high-metal coverages. In the low-coverage regime the movement of the Fermi level is proposed to occur because of universal derelaxation of the GaAs (110) surface. For large metal depositions, the resulting barrier heights are hypothesized to be determined by the interaction of either free (not involved in compound formation with other species) metal or free As with the GaAs surface region. It is shown that based on simple considerations of the relative enthalpy of metal-arsenide formation, it is possible to decide which species is responsible for the barrier height and, thus, to account for the majority of barrier heights to the GaAs (110) surface.
Carbon Doping of GaAs by OMVPE Using CC14: A Comparison of Gallium and Arsenic Precursors
Authors: Hob Son W. S.
Published: March 2011

The carbon doping properties of GaAs with carbon tetrachloride as the dopant source were examined using trimethylgallium (TMGa) or triethylgallium (TEGa) as the gallium precursors and arsine or tertiarybutylarsine (TBAs) as the arsenic precursors. Secondary ion mass spectrometry (SIMS) and Hall measurements (van der Pauw method) were used to characterize the epitaxial GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained with either TMGa and TEGa. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor, over the temperature range examined (520°C - 700°C). Hydrogen at significant concentrations (0.5 – 6 × 1019 cm−3) was detected by SIMS in GaAs:C layers grown at ≤550°C utilizing all four combinations of Ga/As precursors and suggested the presence of electrically inactive C-H complexes. A post-growth anneal under helium at 550°C for 60s of these samples resulted in a 50–100% increase in hole concentration by driving out the hydrogen.
Barrier Height Reduction at the Pd-Ge/n-GaAs Interface
Authors: Meissner P. L. , Bravman J. C. , Kendelewicz T. , Spindt C. J. , Herrera-Gómez A. , Spicer W. E. , Arko A. J.
Published: March 2011

We present the first direct measurements showing changes in the Schottky barrier height for ohmic Pd-Ge contacts to n-type GaAs. The barrier height and interface chemistry were investigated with high resolution synchrotron ultraviolet photoemission spectroscopy. Interfaces were formed by the deposition of one layer each of Pd and Ge on the GaAs substrate, where the deposition sequence was varied to allow a more quantitative determination of the role of each element. A reduction of 0.35 eV in the barrier height occurred in the case where Pd was deposited first. This reduction can be described by a model in which interface states are compensated by charge from As n-type doping of the Ge layer in the Ge-GaAs heterojunction. The dramatic change in barrier height seen when Pd is deposited first contrasts sharply with the stable barrier height observed for the case where the Ge was deposited first, a constant barrier of 0.75 eV was found after every deposition and annealing step. This stability was correlated with constant Ga and As concentrations in the Ge and a relatively low overall As concentration in the overlayer.
Reverse Leakage Current in GaAs/AlGaAs Self Electro-Optic Effect Devices
Authors: Freund J. M. , Swaminathan V. , Focht M. W. , Guth G. D. , Przybylek G. J. , Smith L. E. , Leibenguth R. E. , Chirovsky L. M. F. , D'Asaro L. A.
Published: March 2011

The self-electro-optic effect device (SEED) and the symmetric SEED (S-SEED) have demonstrated considerable applications for photonic switching and logic functionality. A SEED consists of a p-i-n, mesa diode, with a multiple-quantum-well structure for the i region. The symmetric SEED consists of two p-i-n mesa diodes connected in series. The S-SEED has been fabricated in functional arrays containing as many as 32×64 elements. The SEED and S-SEED are operated under a reverse bias, thus low reverse leakage is desired. As the magnitude of the reverse leakage current increases, more incident laser power is required to switch device states and then hold that state. Therefore, understanding the origins of the reverse leakage current and its dependence on mesa and array size is imperative for optimizing device performance.
Oxidation and Diffusion at Poly-SiGe/GaAs Interfaces
Authors: Kavanagh K. L. , Chang J. C. P. , Sadana D. , Cardone F.
Published: March 2011

GaAs has been encapsulated with sputter or electron-beam deposited, thin films of Si or SiGe and annealed in open tube oxygen ambients. The presence of oxygen increases the diffusivity of both Si or Ge in the substrate. Forming gas anneals reduce the diffusivity by orders of magnitude. The diffusivities are greater for sputtered films compared to electron-beam deposited material of the same thickness. And the diffusivity is greater for thicker films and for Ge-rich films whether sputtered or electron-beam deposited.
Hydrogen Incorporation and Carrier Reduction in Hydrogenated n-GaAs:Si and p-GaAs:Zn Crystals
Authors: Zavada J. M. , Wilson R. G. , Jenkinson H. A. , Novak S. W. , Pearton S. J.
Published: March 2011

Hydrogen implantation into either n-GaAs:Si or p-GaAs:Zn crystals leads to a neutralization of charge carriers, primarily through induced crystal damage. The resulting decrease in carriers is useful in opto-electronics applications for confining electrical current or optical radiation. Exposure of the same crystal materials to a hydrogen plasma also leads to reduction of the charge carriers, but through a passivation mechanism involving hydrogen-dopant atom complexes. This technique may be useful for opto-electronics device processing but further details converning the physical mechanisms need to be established. Here we present the results of investigations aimed at correlating the changes in carrier concentration as determined by infrared reflectivity measurements with atomic depth profiles obtained from secondary ion mass spectrometry (SIMS). Differences between the use of hydrogen or deuterium plasmas are also reported.
Neutral Impurity Disordering of III-V Quantum well Structures for Optoelectronic Integration
Authors: Marsh J. H. , Andrew S. R. , Ayling S. G. , Beauvais J. , Bradshaw S. A. , Bryce A. C. , Hansen S. I. , De La Rue R. M. , Glew R. W.
Published: March 2011

The neutral impurities boron and fluorine have been studied as species for impurity induced disordering. In the GaAs/AlGaAs system fluorine disordered multiple quantum well waveguide structures exhibited blue shifts of up to 100 meV in the absorption edge (representing complete disordering) accompanied by substantial changes, > 1%, in the refractive index. The absorption coefficient in partially disordered structures at near band-edge wavelengths was as low as 4.7 dB cm−1. Integrated extended cavity lasers have been fabricated with low losses (19 ± 8.4 dB cm−1) in the passive waveguide. Disordering of GalnAs/AlGalnAs and GalnAs/GalnAsP quantum well structures lattice matched to InP has also been investigated. The temperature stability of as-grown phosphorus-quaternary material is poor, with blue shifts of the exciton peak occuring at temperatures greater than 500°C, but the aluminium-quaternary is stable to at least 650°C. Large blue shifts (up to 90 meV for phosphorus quaternary and 45 meV for aluminium quaternary samples) were observed in the fluorine-implanted samples. The estimated loss in fluorine-disordered phosphorus quaternary samples is typically around 8 dB cm“−1.
The Superlattice Diffusion Probe: A Tool for Modeling Diffusion in III-V Semiconductors
Authors: Allen E. L. , Pass C. J. , Deal M. D. , Plummer J. D. , Chia V. F. K.
Published: March 2011

Undoped AlAs/AlxGa1−xAs superlattice structures were grown by molecular beam epitaxy and annealed under Si3N4, SiO2 or WNX encapsulant films, both with and without the presence of implanted Sn. Enhancement of the Al-Ga interdiffusion coefficient occurred under the Si3N4 film due to in-diffusion of Si. Enhancement was even greater during diffusion of the Sn implant under both Si3N4 and SiO2. Underneath the WNX film, however, interdiffusion was suppressed even in the presence of Sn. We simulated these results with SUPREM IV and show that both the Fermi level effect and vacancy injection from the cap are necessary to cause significant enhancement of Al-Ga superlattice disordering.
Diffusion of P- and N-Type Dopants in GaAs/AIGaAs DH Structure Grown by MOCVD
Authors: Ogasawara N. , Karakida S. , Miyashita M. , Hayafuji N. , Tsugami M. , Mihashi Y. , Murotani T.
Published: March 2011

Most of AIGaAs laser diodes (LDs) contain the doublehetero (DH) structure. The DH structure consists of AIGaAs layers with high Al composition as cladding layers and undoped GaAs or AIGaAs with low Al composition. Therefore, it is important for improvement of device characteristics to understand and control the diffusion of dopants. However, most work on the diffusion of dopants have been carried out on the diffusion in GaAs. In this paper, we compared electrical and optical properties of Si-doped AIGaAs with those of Se-doped AIGaAs and investigated the diffusion of Si, Se and Zn in the GaAs/Al0.48Ga0.52As DH structure by secondary ion mass spectroscopy (SIMS). Doping profile of Si is controllable rather than that of Se. However, from the viewpoint of device characteristics, Se is more suitable than Si.
Hydrogen Passivation of GaAs:C Epitaxial Layers Grown from Metalorganic Sources
Authors: Stavola Michael , Kozuch D. M. , Abernathy C. R. , Hobson W. S.
Published: March 2011

Carbon is readily incorporated into epitaxial GaAs and related alloys grown from metalorganic sources. Hydrogen is also readily incorporated during growth and processing from essentially every possible source including the metalorganics, AsH3, and H2 that are used during growth or in annealing ambients. This hydrogen forms stable neutral complexes with carbon thereby altering the intended p-type doping. In this paper, the properties of the C-H complexes as well as the sources of hydrogen, the stability of passivation, and the concentration of C-H complexes in epitaxial layers will be discussed.
Spin-Splitting and Effective Mass of the 2-Dimensional Electron Gas in an Al0.6Ga0.4Sb/InAs Single Quantum Well
Authors: Manasreh M. O. , Gumbs Godfrey , Zhang C. , Lo I. , Bozada C. A. , Dettmer R. W. , Stutz C. E. , Evans K. R. , Mitchel W. C.
Published: March 2011

The 2-dimensional electron gas (2DEG) in an Al0.6Ga0.4Sb/InAs single quantum well (SQW) is studied using cyclotron resonance (CR) and Shubnikov - de Haas (SdH) techniques. SdH results show spin-splitting in Landau levels at magnetic field strength (B) as low as 1.5T. The effective mass (m*) of the 2DEG was obtained from the peak positions of the CR transmission spectra. The results exhibit oscillatory behavior as a function of B. The m* value extracted from die temperature dependence of the SdH oscillations is in good agreement with the average value of m* obtained from CR measurements. The effective mass is calculated as a function of B using an electron self-energy model based on the Hartree-Fock approximation. The calculated m* values also show oscillatory behavior similar to that of the measured CR m*. Both experiment and theory show that m* maxima are shifted from the integral values (both odd and even) of the filling factors.
GaAs Surface Passivation by InGaP Thin Film
Authors: Hyuga Fumiaki , Aoki Tatsuo , Sugitani Suehiro , Asai Kazuyoshi , Imamura Yoshihiro
Published: March 2011

InGaP thin films are evaluated as wide-bandgap materials for GaAs surface passivation. A 200-Å InGaP thin film increases GaAs photoluminescence intensity 25-fold and enables Schottky barrier heights of more than 0.6 eV on n-type GaAs layers with a carrier concentration of 3×1018 /cm3. These effects persist after annealing at 800 °C for 10 min. InGaP thin films are thus suitable as surface passivation films for high-performance GaAs-MESFETs.
Damage Accumulation in Gallium Arsenide During Silicon Implantation Near Room Temperature
Authors: Haynes T. E. , Holland O. W. , Desnica U. V.
Published: March 2011

Damage accumulation in Si-implanted GaAs has been characterized by ion channeling and Raman scattering as a function of implant temperature, dose, and dose rate. The damage was found to be extremely sensitive to temperature near room temperature (RT), such that an implant dose of 6×1014Si/cm2 which produced a peak damage fraction of 94% at 20°C gave only a 15% damage fraction at 30°C. Such a sharp damage transition obviously has important implications for controlling the activation of dopants implanted at RT. One consequence is a strong dependence of the damage on dose rate near RT: the damage increases with dose rate as the dose rate is increased over nearly two orders of magnitude. Comparison of Ion channeling results with Raman scattering measurements indicates that the morphologies of the dose-rafe-dependent and dose-dependent damage components in RT implants are distinct, ie‥ the rate-dependent component primarily consists of crystalline defects, while the dose-dependent damage nas a large amorphous contribution. These experimental observations are discussed in terms of the competition between different damage nucleation and growth mechanisms as a function of the implant parameters.
Production of Midgap Electron Traps by Ga Out-Diffusion in Rapid-Thermal-Processed GaAs with Sio2 Encapsulants
Authors: Tokuda Yutaka , Suzuki Hitoshi , Katayama Masayuki , Usami Akira
Published: March 2011

Production of midgap electron traps in rapid-thermal-processed (RTP) GaAs with sio2 encapsulant has been studied by deep-level transient spec-troscopy in connection with the rapid out-diffusion of Ga through Sio2. Sio2 films of 50 and 1250 nm in thickness have been deposited on LEC n-type (100) GaAs doped with Si. RTP has been performed at 760 and 910°C for 9 s. The broadened DLTS signal consists of four electron traps with the energy levels of Ec - 0.79, 0.83, 0.78 and 0.81 eV. The depth profiles of the total concentration of four traps coincide with those of the decreased carrier concentration multiplied by 0.14 and 0.054 with RTP at 910 and 760°C for 50-nm-thick samples, respectively. These are 0.29 and 0.026 for 1250-nm-thick samples. This means that the origin of these traps is the Ga vacancy formed by the out-diffusion of Ga since the decrease of the carrier concentration by RTP has been ascribed to the formation of VGa-SiGa complex. However, the observation of the persistent photocapacitance quenching effect indicates that these traps are correlated with the As antisite formed by the migration of As into the Ga vacancy. Four kinds of complex defects including the As antisite are produced by RTP which are complex defects of EL2 group.
Optical Characterization of Heavily Carbon Doped GaAs
Authors: Wang Lei , Haegel N. M.
Published: March 2011

Optical measurements have been performed on heavily carbon doped GaAs layers grown on semi-insulating GaAs substrates by MOMBE (metal-organic molecule beam epitaxy). Photoluminescence excitation (PLE) spectroscopy was used to measure the onsets of optical absorption in these GaAs:C epilayers. It was found that in samples with free carrier concentrations of 6.2×1019, 1.6×1020, and 4.1×1020cm−3, optical absorption begins at 1.40, 1.52, and 1.53 ev, respectively. Combined with the band gap narrowing data from photoluminescence (PL) spectra, we estimated Fermi level locations relative to the top of the valence band. We also measured reflectance in the near infrared region and estimated the effective mass of free holes using a classical two-oscillator model.
High Contrast Optically Bistable Optoelectronic Switches Using Strained InGaAs/AlGaAs Material System
Authors: Kapre R. M. , Chen Li , Kaviani K. , Hu Kezhong , Chen Ping , Madhukar A.
Published: March 2011

We report the the first demonstration of optically bistable switching in monolithic opto-electronic transistor configuration using all III-V components. A strained InGaAs/GaAs asymmetric Fabry-Perot (ASFP) modulator / detector, a strained resonant tunneling diode (RTD), and a GaAs based field-effect-transistor (FET) were used in this demonstration.
As-Implanted and Annealing Behavior of Hand Be Implants in InP and Comparison with GaAs
Authors: Zavada J. M. , Wilson R. G. , Novak S. W.
Published: March 2011

Indium phosphide (InP) and its related alloys have gained increased importance in recent years due to their widespread application in opto-electronics and high speed microelectronics. Ion beam processing has been used to produce electrical activity in selective areas of wafers and for device isolation. However, major problems remain concerning the location, electrical/chemical activity, and thermal stability of the implanted atoms in such devices. In this paper, we present detailed results concerning the distribution of 1H and Be atoms implanted into single crystal InP wafers. Secondary ion mass spectrometry has been used to depth profile 1H and Be implanted at different engergies, from 0.1 to 1.0 MeV, and with fluences up to 1016 cm2. Implanted samples have also been examined after furnace annealing to determine the onset and extent of thermal redistribution. Resulting profiles have been compared with corresponding implants into single crystal GaAs to help clarify diffusion behavior.
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

Excess 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

MBE 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

A 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

We 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

In 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

AlInAs 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

Low-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

The 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

We 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

We 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

We 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

We 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

Schottky 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

Vapor 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

Zinc 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

Spectroscopie 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

Organometallic 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

Epitaxial 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

The 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

We 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

Potential 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

The 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

GaN 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.