bluuebunny/crossref_metadata_2025_split huggingface dataset:
Threading Dislocations in InxGabxAs/GaAs System
Authors: Tamura M. , Hashimoto A. , Nakatsugawa Y. 
Published: March 2011

ABSTRACTThreading dislocation morphologies and characters, as well as their generation conditions in InxGa1−xAs films grown by molecular-beam epitaxy on GaAs (001) substrates have been examined, mainly using cross-section al transmission electron microscopy (XTEM) as a function of x and film thickness. The formation of severe threading dislocations is detected in epilayers ofx≧0.2 at a fixed film thickness of 3 μm and with film thicknesses greater than 2μmat x=0.2. Most of the observed threading dislocations are 60°- and pure-edge type dislocations along the <211> and [001] directions, respectively. The former type dislocations are mainly observed in layers of x≧0.2; the latter predominantly exist in layers of X≧O.3.
Non-Contact, Wafer-Scale Deep Level Transient Spectroscopy (DLTS) Based on Surface Photovoltage (SPV)
Authors: Lagowski Jacek , Morawski Andrzej , Edelman Piotr 
Published: March 2011

ABSTRACTWe 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

ABSTRACTOptical 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTGaAs 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

ABSTRACTRaman 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

ABSTRACTDislocation 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

ABSTRACTA 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

ABSTRACTThe 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

ABSTRACTWe 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.
Oxidation and Diffusion at Poly-SiGe/GaAs Interfaces
Authors: Kavanagh K. L. , Chang J. C. P. , Sadana D. , Cardone F. 
Published: March 2011

ABSTRACTGaAs 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

ABSTRACTHydrogen 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

ABSTRACTThe 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

ABSTRACTUndoped 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

ABSTRACTMost 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

ABSTRACTCarbon 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

ABSTRACTThe 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

ABSTRACTInGaP 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

ABSTRACTDamage 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

ABSTRACTProduction 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

ABSTRACTOptical 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.
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

ABSTRACTIndium 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.