bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interface Recombination and Threshold Current in Grinsch-QW ALGaAs/GaAs Laser Diodes
Authors: Xie K. , Kim H. M. , Wie C. R. , Varriano J. A. , Wicks G. W. 
Published: March 2011

ABSTRACTA series of Graded-Index Waveguide Separate-Confinement Heterostructure Quantum Well (GRINSCH-QW) laser diodes were grown by MBE at the systematically varied substrate temperatures. The threshold current of laser diodes were found to depend strongly on the growth temperature. The structure and electrical characteristics of the laser diodes were studied by double-crystal x-ray diffraction, I-V-T, C-V and deep level transient spectroscopy (DLTS). The interface recombination is found to be the dominant carrier transport process in the high threshold current laser diodes and is closely related to the presence of the high concentration of deep traps and interface states. In the low threshold current laser diodes, diffusion process is found to be the dominant carrier transport process.
AlAs-GaAs Beterojunction Engineering by Means of Group IV Interface Layers
Authors: Bratina G. , Sorba L. , Biasiol G. , Vanzetti L. , Franciosi A. 
Published: March 2011

ABSTRACTValence and conduction band discontinuities in AlAs-GaAs heterostruc-tures have been tuned through fabrication of epitaxial Ge layers at the interface. The local interface dipole associated with the Ge layer can be added to, or subtracted from the natural band offsets depending on the growth sequence. Comparison with earlier results for AlAs-Si-GaAs heterostructures, shows that the observed dipole is consistent in direction and order of magnitude for Ge and Si interface layers. The dipole initially increases with interface layer thickness more rapidly for Ge than for Si, however the total maximum dipole achievable at the interface is identical (0.4eV), within experimental uncertainty, for the two group IV elements.
High Performance Quantum Well Asymmetric Fabry-Perot Reflection Modulators: Effect of Layer Thickness Variations
Authors: Law K-K. , Whitehead M. , Merz J. L. , Coldren L. A. 
Published: March 2011

ABSTRACTWe present a study of the effects of the active cavity layer thickness variation on the operating characteristics of normally-on low-voltage high performance asymmetric Fabry-Perot modulators. For a modulator consisting of 25.5 periods of a multiple-quantum-well active region (100Å GaAs / 45Å (GaAs/AlAs) short period superlattices) with 5 pairs and 20.5 pairs of top and bottom quarter-wave stacks respectively, assuming only layer thickness variation in the active cavity caused by Ga flux nonuniformity, the shift of the Fabry-Perot mode wavelength is ∼5.8 times that of the QW heavy-hole exciton. This affects the relative distance between the wavelengths of the quantum well exciton and the Fabry-Perot resonance, and hence the performance of the modulators. Also, the tolerable percentage change of the Fabry-perot mode wavelength should be less than 0.13% in order that such modulator arrays have at least 10:1 contrast ratios at a fixed optimum operating wavelength. This defines the epitaxial growth tolerance for obtaining the uniformity of the operating wavelength of an array and the precision with which we can obtain a desired wavelength, its reproducibility, and its uniformity across a wafer.
Simulation Design and Device Characteristics of AlAs/GaAs/AlAs Resonant Tunneling Structures with a GalnAs Emitter Spacer Layer
Authors: Choi Y. W. , Kim H. M. , Wie C. R. 
Published: March 2011

ABSTRACTElectrical and structural investigation of AlAs/GaAs/AlAs resonant tunneling structures with pseudomorphic strained Ga1−xInxAs (x=0, 0.05, 0.1, 0.15, and 0.2) emitter spacer layer are presented. As indium composition increased, the peak current density, peak voltage, and peak to valley ratio increased. For a theoretical understanding of these increases, a self-consistent simulation was employed. In the simulation, we treated the 2-dimensional electrons confined in the low energy bandgap GalnAs emitter spacer well as pseudo-3-dimensional electrons, distributed continuously down to the emitter launching energy. In the simulation, we used the bottom energy of the pseudo-3-dimensional electrons to be ⅔δEc below the emitter conduction band edge. Using the above values, an excellent agreement of peak current density and peak voltage between the experiment and the simulation was achieved. Also, for structural identification, standard double crystal x-ray rocking curve technique has been used. From the interference analysis of the x-ray results, we could obtain the indium composition times thickness product.
Dependence of Interdiffusion in AlGaAs on Stoichiometry between Ga-RICH and As-Rich Solidus Limits
Authors: Olmsted B. L. , Houde-Walter S. N. , Viturro R. E. 
Published: March 2011

ABSTRACTAl-Ga interdiffusion of undoped AlGaAs/GaAs multiple quantum wells was studied by varying the crystal defect concentrations and is shown to be mediated predominantly by column III vacancies from the Ga-rich to the As-rich side of the solidus. An increase of two orders of magnitude has been observed in the interdiffusion coefficient when going from the inclusion of excess Ga to excess As in the evacuated ampoule. The in-diffusion of column HI vacancies from the surface in an As-rich ambient, as well as the out-diffusion of column III vacancies from the n-type substrate in an As-poor ambient, were observed using secondary ion mass spectroscopy. The role of SiO2 and Si3N4 encapsulations in controlling the interdiffusion was also determined. We have also observed that the photoluminescence intensity in the Ga-rich crystal is several orders of magnitude stronger than that of the As-rich crystal. Finally, cathodoluminescence spectroscopy reveals a deep level which has been associated with a Ga vacancy complex in the samples annealed with excess As that correlates with the extent of Al-Ga intermixing.
Effect of Surface Ambient on Manganese Diffusion in Gallium Arsenide
Authors: Wu C. H. , Hsieh K. C. 
Published: March 2011

ABSTRACTData are presented showing the effects of diffusion sources, surface encapsulation, and As overpressure on Mn diffusion in GaAs. Four different Mn-containing sources are used, including Mn, Mn,MN3As, and MnAs granules as well as Mn thin film deposited directly onto GaAs substrate. Smooth surface morphology with high surface Mn concentration can be obtained using MnAs (and in certain conditions, Mn3As) as diffusion source; different degrees of surface degradation are observed if otherwise sources are used as diffusion source. Data also show surface encapsulation and As overpressure have significant effects on the reaction between the source and GaAs and the Mn diffusion in GaAs.
The Effect of Co-Implantation on the Electrical Activity of Implanted Carbon in GaAs
Authors: Moll A. J. , Walukiewicz W. , Yu K. M. , Hansen W. L. , Haller E. E. 
Published: March 2011

ABSTRACTWe have undertaken a systematic study of the effect of co-implantation on the electrical properties of C implanted in GaAs. Two effects have been studied, the additional damage caused by co-implantation and the stoichiometry in the implanted layer. A series of co-implant ions were used: group III (B, Al, Ga), group V (N, P, As) and noble gases (Ar, Kr). Co-implantation of ions which create an amorphous layer was found to increase the electrical activity of C Once damage was created, maintaining stoichiometric balance by co-implantation of a group III further increased the fraction of electrically active carbon impurities. Co-implantation of Ga and rapid thermal annealing at 950°C for 10 s resulted in carbon activation as high as 68%, the highest value ever reported.
Damage Related Defect Levels in Oxygen Implanted GaAs and InP
Authors: He L. , Anderson W. A. 
Published: March 2011

ABSTRACTOxygen ion-implantation can be used to create high resistivity regions in GaAs and InP. We have studied the low dose oxygen implantation in GaAs and InP by photoreflectance spectroscopy (PR), deep level transient spectroscopy (DLTS) and current-voltage (I-V) characteristics. Rapid thermal annealing (RTA) treatments were carried out at different temperatures after implantation to study the annealing temperature effect. The surface disturbance by implantation was studied by PR. Free carrier compensation was observed in every implanted sample and gave improved I-V properties. By DLTS tests, one electron trap with Ea = Ec-0.15eV and a hole trap with Ea = Ev + 0.76eV in the starting GaAs wafer disappeared after O+ implantation due to carrier compensation. In undoped InP, three new electron traps with Ea = Ec-0.47eV, 0.28eV and O.lleV were created after O+ implantation which are believed to be damage related. The comparison of the results from undoped and n-type doped InP indicated that the carrier compensation effect is substrate doping dependent.
The Effect of Si Planar Doping on DX Centers in Al.20Ga.74As
Authors: Solomon G. S. , Roos G. , Muñoz-Merino E. , Harris J. S. 
Published: March 2011

ABSTRACTThe effect of planar Si doping on the DX center in AlGaAs is investigated using Capacitance-Voltage and Deep Level Transient Spectroscopy techniques. We observe an increase of approximately six orders of magnitude in the DX center capture cross section in Al.26Ga.74As with planar doped Si spikes of 2×1012cm−2 as compared to conventional homogeneous Si doped Al.26Ga.74As. We also observe a small increase in the DX activation energy which was initiated at a lower planar doping of 4×1011 cm−2 and remained constant for the higher planar doping case. We believe the DX center concentration is not changed by the planar doping levels studied here. A model is proposed to explain the increase in capture cross section based on a biaxial stress state in the planar doped AlGaAs region.
Crystal Structure Of Lt Gaas Layers Before And After Annealing
Authors: Liliental-Weber Zuzanna 
Published: March 2011

ABSTRACTThe structural quality of GaAs layers grown at low temperatures by solid-source and gassource MBE at different growth conditions is described. Dependence on the growth temperature and concentration of As [expressed as As/Ga beam equivalent pressure (BEP)] used for the growth is discussed. A higher growth temperature is required to obtain the same monocrystalline layer thickness with increased BEP The annealing of these layers is associated with the formation of As precipitates. Semicoherent precipitates with lowest formation energies arc formed in the monocrystalline parts of the layers grown with the lowest BEP. Precipitates with higher bormation energies are formed when higher BEP is applied; they are also formed in the vicinity of structural defects. Formation of As precipitates releases strain in the layers. Arsenic precipitates are not formed in annealed ternary (InAlAs) layers despite their semi-insulating properties. The role of As precipitates in semi-insulating properties and the short lifetime of minority carriers in these layers is discussed.
Defect Model and Growth Characteristics of Low Temperature GaAs
Authors: Fatemi M. , Tadayon B. , Dietrich H. B. , Tadayon S. 
Published: March 2011

ABSTRACTLow-temperature GaAs layers (LTGaAs) grown by molecular beam epitaxy on GaAs substrates have been characterized by x-ray diffraction techniques. X-ray rocking curve measurements on more than 200 anneal conditions show that through appropriate choice of growth condition, layers with different states of strain are obtained. Three distinct ranges of low temperature growth are defined, labelled as “low-range,” “mid-range,” and “high-range,” corresponding to growth temperatures less than 260 °C, between 260 and 450 °C, and more than 450 °C, respectively. 0.5μm thick films grown in the low-range are amorphous, whereas those in the mid-range are fully strained and lattice-matched to the substrate, and those grown above 450 °C are indistinguishable from ordinary GaAs. Notable properties of mid-range layers are the random behavior of the as-grown strain, and the expansion and contraction of the lattice parameter with thermal anneals up to 900 °C. A growth model for LTGaAs based on arsenic antisite defects is proposed.
Long Wavelength Characterization of Internal Quantum Efficiency in LT-GaAs MSM Photodiodes
Authors: Morse Jeffrey D. , Mariella Raymond P. 
Published: March 2011

ABSTRACTMetal-Semiconductor-Metal (MSM) photodiodes fabricated from low temperature (LT) grown GaAs by molecular beam epitaxy have been characterized for wavelengths extending out to 1.5μm. External quantum efficiencies on the order of 0.5 % have been measured for subbandgap wavelengths, which translates to internal quantum efficiencies of 2–4 % for the interdigitated electrode structure with lμm finger spacing and width. Although the effective lifetime of the LT-GaAs has been determined to be <1ps, an MSM photodiode response of ∼10ps full width at half maximum was measured by correlation techniques at 820 nm wavelength, and a system limited response of 3GHz was measured at 1.3 μm wavelength. These experimental results will be described in detail.
Incorporation of Silicon in Low Temperature Molecular Beam Epitaxial GaAs
Authors: Manasreh M. O. , Evans K. R. , Stutz C. E. , Look D. C , Hemsky J. 
Published: March 2011

ABSTRACTThe localized vibrational mode (LVM) of silicon donor (SiGa) in molecular beam epitaxial GaAs layers grown at various temperatures is studied using the infrared absorption technique. It is found that the total integrated absorption of this LVM is decreased as the growth temperature decreases. This finding suggests a nonsubstitutional incorporation of Si in GaAs layers grown at ∼200 °C. On the other hand, an almost complete substitutional incorporation is obtained in GaAs layers grown at temperatures higher that 350 °C. Thermal annealing does not cause any recovery of the SiGa LVMs in present GaAs layers grown at ∼200°C.
Structural and Defect Study of Low Temperature INP Grown by Gas Source Molecular Beam Epitaxy
Authors: Garcia J. Ch. , Hirtz J. P. , Maurel P. , Von Bardeleben H. J. , Bourgoin J. C. 
Published: March 2011

ABSTRACTThe low temperature growth procedure used in the case of GaAs to introduce high concentrations of deep traps such as arsenic antisite defects has been extended to the growth of InP by gas source molecular beam epitaxy. The low temperature growth of InP induces a strong group V stoechiometric deviation (of the order of +1%). On the other hand, Secondary Ion Mass Spectrometry reveals high levels of hydrogen ranging from 3.1018 to 3.1019 cm−3 depending on growth temperature. Undoped layers are found to be resistive without any post annealing. Annealing experiments above 250°C lead to conductive layers suggesting a passivation effect of both shallow donors and acceptors by hydrogen.
Optically Detected Magnetic Resonance of Arsenic Antisites in GaAs MBE Layers Grown at Low Temperatures
Authors: Rong F. C. , Fotiadis L. , Sun H.-J. , Watkins G. D. , Taysing-Lara M. A. , Flemish J. , Chang W. H. 
Published: March 2011

ABSTRACTObservation of Arsenic antisites (AsGa) in GaAs layers grown by molecular beam epitaxy (MBE) at low substrate temperatures (∼ 200°C) is reported, using electron paramagnetic resonance (EPR), magnetic circular dichroism in absorption (MCDA), and MCDA tagged by optically detected magnetic resonance (MCDA-ODMR). This experiment confirms that there is a MCD absorption band directly associated with AsGa in the GaAs layers. The AsGa concentration in the GaAs layers is found to decrease by about one order of magnitude after annealing at 600°C for two minutes.
Photoreflectance and X-Ray Photoelectron Spectroscopy in Lt MBE GaAs
Authors: Look D. C. , Hoelscher J. E. , Grant J. T. , Stutz C. E. , Evans K. R. , Numan M. 
Published: March 2011

ABSTRACTIt has recently been shown that a 1000Å cap layer of molecular beam epitaxial (MBE) GaAs grown at 200°C passivates the surface of a GaAs active layer (n≃2×1017cm−3) in the sense of reducing the free–carrier depletion which arises from surface acceptor states. The same phenomenon holds for active-layer concentrations up to 7×1018cm−3, for caps as thin as 14Å, and for either As2 or As4 anion species. In an attempt to understand these effects, we have applied photoreflectance (PR) and x–ray photoelectron spectroscopy (XPS). In general, the PR shows contributions from the surface, cap/active–layer interface, and active–layer/buffer–layer interface, because each of these regions can have a different electric field. In fact the various field strengths can be determined from Franz–Keldysh oscillations (FKO), and good agreement with Hall–effect measurements is usually found. However, for 200°C material, no PR is seen, suggesting that there is no surface charge (no surface acceptor states below the Fermi level) or at least no surface–charge modulation by the light. The XPS data, which arise only from the near–surface (∼30Å) region, show that the binding energies in the capped samples are increased (i.e., surface Fermi pinning energy decreased) by 0.2 eV with respect to those in the uncapped samples. These data are discussed in relation to a passivation model.
Fluorine Atom Addition to the Diamond (111) Surface
Authors: Freedman Andrew , Robinson Gary N. , Stinespring Charter D. 
Published: March 2011

ABSTRACTDiamond (111) surfaces with the dehydrogenerated 2×1 reconstruction have been exposed to a beam of atomic fluorine at 300 K. The uptake of fluorine, as measured using X-ray photoelectron spectroscopy, is quite efficient and saturates at a coverage of less than a monolayer. Low energy electron diffraction patterns indicate that fluorine termination of the diamond surface produces a lxi bulk-like reconstruction in contrast to the disordered surface produced on the (100) surface.
Characterization of the Si/Diamond Interface
Authors: Williams K. E. , Speck J. S. , Drory M. D. 
Published: March 2011

ABSTRACTAuger spectroscopy is used to determine the bonding states of carbon in the interfacial region between silicon and PECVD diamond films. SiC and sp2-hybridized carbon are observed. We suggest a possible growth sequence for diamond films to account for the interfacial layer.
Optical Evidence of Reduction of Radiative Defects in Diamond Films Grown by Acetylene-Oxygen Flames
Authors: Freitas J. A. , Strom U. , Doverspike K. , Marks C. M. , Snail K. A. 
Published: March 2011

ABSTRACTRaman scattering and photoluminescence spectroscopies have been used to characterize polycrystalline diamond films deposited on molybdenum substrates by laminar and turbulent premixed oxygen-acetylene flames in air. Samples deposited under laminar flame conditions are characterized by a high degree of incorporation of nitrogen-vacancy complexes. However, samples deposited with a turbulent flame show a significant decrease in the concentration of these defects and a reduction of the amorphous carbon film component.
Tantalum and Tantalum Silicide High Temperature Rectifying Contacts on Type MB Natural Diamond
Authors: Sahaida Scott R. , Thompson Dale G. 
Published: March 2011

ABSTRACTTantalum and tantalum suicide contacts were investigated as high temperature rectifying contacts on type MB natural diamond. Tantalum and silicon were co-sputtered using DC and RF planar magnetrons, respectively. Current-voltage measurements of tantalum suicide subjected to various anneals and of pure tantalum contacts were recorded at 50°C intervals up to 400°C which was the desired operating temperature of the rectifying contact. Tantalum contacts to diamond maintained good rectification up to 300°C whereas amorphous tantalum suicide operated well up to 400°C.
Chemical Vapor Deposition of Diamond Films Using Water:Alcohol:Organic-Acid Solutions
Authors: Rudder R. A. , Posthill J. B. , Hudson G. C. , Malta D. P. , Thomas R. E. , Markunas R. J. , Humphreys T. P. , Nemanich R. J. 
Published: March 2011

ABSTRACTA low pressure chemical vapor deposition technique using water-alcohol vapors has been developed for the deposition of polycrystalline diamond films and homoepitaxial diamond films. The technique uses a low pressure (0.50 – 1.00 Torr) rf-induction plasma to effectively dissociate the water vapor into atomic hydrogen and OH. Alcohol vapors admitted into the chamber with the water vapor provide the carbon balance to produce diamond growth. At 1.00 Torr, high quality diamond growth occurs with a gas phase concentration of water approximately equal to 47% for methanol, 66% for ethanol, and 83% for isopropanol. A reduction in the critical power necessary to magnetically couple to the plasma gas is achieved through the addition of acetic acid to the water.alcohol solution. The lower input power allows lower temperature diamond growth. Currently, diamond depositions using water:methanol:acetic-acid are occurring as low as 300 ° C with only about 500 W power input to the 50 mm diameter plasma tube.
High Quality Epitaxial Films of ZnSe and ZnSe/ZnS Strained Layer Superlattices Grown by MOCVD
Authors: Pong Chungdee , DeMattei R. C. , Feigelson R. S. 
Published: March 2011

ABSTRACTHigh quality epitaxial films of ZnSe and ZnSe/ZnS strained layer superlattices (SLS) have been grown on (100) GaAs substrates using diethylZinc, dimethylSelenide, diethylSelenide, and propyleneSulfide as reagents in both atmospheric and low pressure environment. This source combination produces the results showing the influence of process conditions, such as reagent flow ratio (fv1/f11) and substrate temperature, on the film stoichiometry, surface morphology, and crystalline quality. Low temperature photoluminescence (PL), Rutherford backscattering spectrometry (RBS), cross-sectional TEM, and x-ray diffraction have been used to characterize the films. Photoluminescence studies at 2.8 K on samples of ZnSe/ZnS strained layer superlattices; 10 periods ZnSe(1.5 nm)/ZnS(8.5 nm), have shown quantum size effect with the peak energy blue-shifted to 3.03 eV with the FWHM=73 meV. Atomic force microscopy (AFM) was applied to study surface morphology of multilayer samples.
The Application of Lamma-1000 to the Elemental Analysis of CdTe Compound
Authors: Belogorokhov A. I. , Khar'Kovsky A. Yu. 
Published: March 2011

ABSTRACTData from numerous LMMS analysis of specimens of a polished sample of CdTe crystal are treated statistically to estimate the accuracy and reproducibility of quantitative analysis. The data are consistent with the instrument producing a fixed condition in plasma for a given laser power. The plasma chemistry is shown to control the conditions reached in the plasma for a given power.
Theory of Doping of Diamond
Authors: Bernholc J. , Kajihara S. A. , Antonelli A. 
Published: March 2011

ABSTRACTElectronic applications of diamond require control over native defects as well as the ability to dope it p- and n-type. B is an excellent p-type dopant, but n-type doping has proven very difficult. Diamond films have also been very difficult to anneal, indicating a high activation energy for self-diffusion. We have investigated the properties of native defects and impurities through large-scale band structure and Car-Parrinello calculations. We indeed find that the activation energy for self-diffusion is very high in the intrinsic material, but it decreases by as much as 3 eV in either p- or n-type material. P, Li, and Na are shallow donors, but their solubilities are too low for incorporation into diamond through in-diffusion. It is energetically favorable for B and N to dissolve in diamond, which explains their prevalence in natural diamond. The calculations explain for the first time the reasons for the distortion of atoms around N from the fully tetrahedral site, as well as why N is a deep rather than a shallow donor. We also consider the effects of simultaneous doping with N and B on the thermodynamic equilibrium between diamond and graphite.