bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Structure of Amorphous Hydrogenated Silicon:Carbon Alloys Using X-Ray and Neutron Scattering and Computer Simulation - The Effect of Hydrogen Dilution
Authors: Burke T. M. , Honeybone P. J. R. , Huxley D. W. , Newport R. J. , Frauenheim Th. , Blaudeck P. , Kohler Th. , Hotham C. 
Published: March 2011

ABSTRACTNeutron and X-ray diffraction techniques have been applied to the study of two samples of a-Si:C:H. Both samples were prepared using conventional glow discharge methods, but the hydrocarbon/silane precursor gas was diluted with hydrogen in one case. Analysis of the X-ray diffraction data gives a clear picture of the silicon network, since the scattering profile is dominated by the Si-Si correlations. The high real-space resolution neutron diffraction data, however allows one to comment on the effect of this dilution on the silicon-carbon bonding morphology, and in particular on the degree to which the additional hydrogen enhances hetero-coordination. In addition we present the results of a preliminary computer simulation study of the structure of a-C:H and a-Si:H using an approximate molecular dynamic density functional theory, and discuss its viability in the study of the more complex a-Si:C:H ternary alloy.
Contact-Free Determination of Scattering Times in Heterojunction Device Structures
Authors: Omling P. , Linke H. , Ramvall P. , Meyer B. K. 
Published: March 2011

ABSTRACTIn this paper we present contact-free measurement techniques which are important for the evaluation of heterojunctions of interest for optical as well as high-speed devices. The techniques are the microwave-detection of Shubnikov-de Haas oscillations, photoluminescence-detected magneto-oscillations, and optically detected cyclotron resonance using microwaves (ODCR) as well as far-infrared lasers (FIR-ODCR). The techniques are illustrated by several examples, and the possibilities to determine 2D carrier concentrations, effective masses, and scattering times in the heterojunction structures are discussed.
Photoreflectance Characterization of the Semi-Insulating InP Substrate Interface with InGaAs and InAlAs Epilayers
Authors: Zhou Weimin , Shen H. , Pamulapati J. , Dutta M. , Bennett B. R. , Perry C. H. , Weyburne D. W. 
Published: March 2011

ABSTRACTPhotoreflectance (PR) has been performed on a series of undoped and n-type, InGaAs and InAlAs molecular beam epitaxy (MBE) grown layers with different In mole fractions, and epilayer thicknesses on Fe-doped semi-insulating (SI)-InP substrates. From investigations of the temperature dependence, time constant dependence and an additional cw light beam intensity dependence, three substrate peaks are identified as an excitonic transition from the substrate, a free electron transition near the interface which gives a Franz-Keldysh oscillation (KFO), and a transition from the spin-orbit split-off valence band. The results are indicative of a redistribution of charge near the substrate interface in the process of MBE growth; the associated PR signal (phase) could be used for in-situ monitoring of epilayer growth on SI-InP wafers.
On the Origin of the Contrast Inhomogeneities Found on In0.52Al0.48As Layers Grown on InP Substrates At High Temperatures
Authors: Peiro F. , Cornet A. , Morante J. R. , Georgakilas A. 
Published: March 2011

ABSTRACTThe present work deal with the coarse contrast modulation along the <010> directions observed in (100) planar view TEM observations of In0.52Al0.48As layers grown on InP substrates at temperatures higher than 550°C. The most important features of these contrast inhomogeneites are briefly reviewed. Besides, the appearance of the contrast in [011] cross-sectioned specimens is presented and its origin related to precipitates at the layer-substrate interface. The density of precipitates (ρp) has been found to increase as Tg rises, and an approximate value of the activation energy needed to induce the precipitation has been derived from the correlation of ρp and Tg.
Heavily Carbon Doped P-Type GaAs/InGaAs Strained-Layer Superlattices Grown by Mombe
Authors: Qi Ming , Luo Jinsheng , Shirakashi J. , Tokumitsu E. , Nozaki S. , Konagai M. , Takahashi K. 
Published: March 2011

ABSTRACTHeavily carbon doped ρ-type GaAs/In0.3Ga0.7 As strained-layer superlattices (SLSs) with hole concentrations as high as 1 × 1020 / cm3 were successfully grown for the first time by metalorganic molecular beam epitaxy (MOMBE) using trimethylgallium (TMG), solid arsenic and solid indium. The single quantum well (SQW) and multiple quantum well (MQW) structures with different well width from 2 to 16nm were also designed to analyse the strain relaxation. The experimental results show that the SLS structures made of heavily carbon doped ρ—type GaAs and InGaAs have both of high hole concentration and small effective bandgap, which are satisfied for the application in heterojunction bipolar transistors (HBTs) as base layer.
Temperature Dependent Quenching Mechanisms of the Luminescence of InGaAs/GaAs Strained Quantum Wells
Authors: Martelli F. , D'Ottavi A. , Catania B. , Bruni M. R. , Simeone M. G. , Zugarini M. 
Published: March 2011

ABSTRACTIn this work we report on detailed temperature dependent photoluminescence measures on InGaAs/GaAs strained layer quantum well structures. Excitation energies above and below the GaAs band gap have been used in order to separate the contributions of the carrier trapping to the generation-recombination processes from the recombination mechanisms proper of the quantum wells. The results show that a decrease of the trapping efficiency contributes to the photoluminescence quenching, and suggest that the strong photoluminescence quenching observed in these structures should be mainly attributed to defects present in the quantum wells. A clear dependence of the luminescence quenching on the excitation intensity has also been found.
Constant Temperature LEC Growth of Uniform Composition InGaAs Bulk Crystals through Continuous Supply of GaAs
Authors: Nakajima K. , Kusunoki T. , Kuramata K. 
Published: March 2011

ABSTRACTA 45 mm long In0.05 Ga0.95 As ternary bulk crystal with an extremely uniform composition has succeeded to be grown at a constant temperature by the liquid encapsulated Czochralski (LEC) method with a continuous supply of only GaAs to the pseudobinary InAs-GaAs growth melt. A double crucible which has both growth and source melt zones has been developed to improve the controllability of die supply of GaAs to the melt. These zones are separated by a cylindrical wall with a slit through which source elements are continuously supplied from die source melt zone to the growth melt zone. These results demonstrate mat large and uniform InGaAs bulk crystals can be grown using the constant temperature LEC method with a double crucible and with a continuous supply of only GaAs.
Optical Studies of InP/GaAs/InP Single Strained Layers
Authors: Hessman Dan , Pistol Mats-Erik , Olajos Janos , Seifert Werner , Liu Xiao , Samuelson Lars 
Published: March 2011

ABSTRACTSingle strained layers of GaAs grown on InP have been studied using different optical techniques. Absorption has been measured on these structure which are believed to be type II. The absorption is found to increase slowly close to the threshold and the spectral shape is very similar to photoluminescence excitation spectra. No sharp excitonic peaks were found. The absorption has been modelled using K.p-theory including strain and confinement. The agreement with experiments is good with respect to the shape of the spectra but differs a factor of three with respect to the magnitude of the absorption. The strain and composition of the samples have been measured by a combination of photoluminescence and Raman spectroscopy.
Strain Analysis on MBE Grown InAs/AlSb Ultrathin-Layer Superlattices Using Raman Scattering
Authors: Yano Mitsuaki , Furuse Hiroshi , Okuizumi Masaru , Inoue Masataka 
Published: March 2011

ABSTRACTThis paper describes an experimental analysis of strained InAs/AlSb ultrathin-layer superlattices (ULSs) grown by MBE. Interface bonds of InSb or AlAs were selectively made in the ULSs by controlling the beam supply sequence during growth. Structural analysis was performed for ULSs on both InAs and AlSb buffer layers using Raman scattering. This analysis revealed that each constituent in the ULSs was relaxed individually only when the AlAs interface bond was combined with the AlSb buffer layer. Other combinations of the interface bond and buffer layer, however, resulted in a free-standing superlattice structure. These experimental results are consistent with the interface dependence of electron mobility reported for InAs/AlSb single quantum well structures.
High Speed InAs/AlSb and In0.53Ga0.47As/AlAs Resonant Tunneling Diodes
Authors: Chow D. H. , Schulman J. N. , ÖZBAY E. , Bloom D. M. 
Published: March 2011

ABSTRACTWe report a comparison of InAs/AlSb and In0.53Ga0.47As/AlAs resonant tunneling diodes (RTDs) for high speed switching applications. Theoretical simulations are performed for both heterostructure systems using a two band tunneling model, which includes the effects of strain and band bending. Experimental peak current densities are observed to agree well with the calculated values over the range 1×104 A/cm2 to 5× 105 A/cm2. In both types of structures, the maximum peak current density (directly related to switching speed) is determined by device heating. In this regard, InAs/AlSb RTDs are found to be slightly superior to In0.53Ga0.47As/AlAs RTDs due to the low contact and series resistances of InAs. However, higher peak-to-valley ratios and swing voltages are obtained in the In0.53Ga0.47As/AlAs devices up to their maximum attainable peak current density (3.1×105 A/cm2 in this study). Both heterostructure systems yield RTDs with estimated switching times near 1 ps.
GaAs Devices for Low Loss Power Rectification
Authors: Munukutla L. V. , Cheng S. H. , Anderson S. J. 
Published: March 2011

ABSTRACTHigh voltage GaAs Schottky rectifiers fabricated using vapor phase epitaxy have been observed to be an order of magnitude higher in switching speeds than silicon. Measured rectifier barrier heights deduced from the I-V and C-V plots were found to be in good agreement with previously reported values. Our experimental results show no correlation between the epilayer thickness and barrier height.
Selective Implantation Patterning and MBE Regrowth for Integration of Mm-Wave Application Heterojunction Devices
Authors: Brugger Hans , Wölk Claus , Müssig Harald 
Published: March 2011

ABSTRACTA technology based on a combination of selective implantation for lateral patterning and a following large area regrowth by molecular beam epitaxy (MBE) is introduced. The technology allows the monolithic integration of devices with different vertical layer sequences on s.i. GaAs substrates in a quasi planar way, e.g. a heterojunction field-effect-transistor (HFET) with a Schottky diode or a MESFET with a Schottky diode. Selective high resistive (>109 Ω/sq) and highly conducting (<20Ω/sq) buried layers are fabricated by high temperature stable oxygen and silicon implantation, respectively. The following MBE regrowth of epitaxial layers yields to an excellent surface morphology. HFET structures with pseudomorphic AlGaAs/InGaAs/GaAs heterostructures grown on implanted substrates exhibit a strong photoluminescence response. Carrier densities up to 2.0×1012cm−2 (1.6×1012cm−2) and Hall mobilities of 6150 cm2/Vs (17700 cm2/Vs) at 300 K (80 K) in the dark are achieved. The material quality is drastically improved by substrate preparation and in-situ cleaning prior to MBE regrowth.
(InAs)1/(GaAs)n Superlattice Quantum Well Lasers
Authors: Lopata J. , Dutta N. K. , chand Naresh 
Published: March 2011

Strained layer In0.2Ga0.8As/GaAs quantum-well (QW) lasers have been used to pump Erbium Doped Fiber Amplifiers for use in opto-electronic communication systems. These InGaAs/GaAs Q-W lasers grown as graded index separate confinement heterostructures (GRINSCH) emit at 980 nm and have exhibited low threshold current densities, high electrical to optical power conversion efficiencies, low noise, and low temperature sensitivities [1–3]. Recently there has been much attention toward the growth and fabrication of devices containing short period superlattices of (InAs)m/(GaAs)m or (GaAs)m/(AlAs)n compositions [4–9]. Indeed the growth of inverted MODFET structures using a (GaAs)/(AlAs) superlattice barrier in place of an AlGaAs random alloy exhibited an increase in low temperature mobility due to reductions in the number of impurities and interface roughness [7]]. Can the optical properties of strained layer InGaAs/GaAs Q-W lasers also be improved by growing an (InAs)/(GaAs)4 short period superlattice as the active layer in place of the In0.2Ga0.8 As random alloy?This paper reports the fabrication of ridge waveguide lasers using a 6 period (InAs)1/(GaAs)4 superlattice active region in a GRINSCH laser structure. One period of the superlattice consists of 1 monolayer (ML) of InAs and 4 ML of GaAs. Thus the average In composition in the superlattice is 20%. This superlattice laser is an alternative to the In0.2Ga0.8As/GaAs random alloy quantum-well laser used as a pump source for Erbium Doped Fiber Amplifiers. In a single quantum well In0.2Ga0.8As/GaAs laser the active region is a thin layer (-70Å thick) sandwiched between GaAs barrier layers. The superlattice active laser reported here has 6 periods of (InAs)1/(GaAs)4 as the light emitting region of a total width comparable to a single quantum well of random alloy composition.
Recent Developments in Gas Source Molecular Beam Epitaxy
Authors: Cunningham J. E. 
Published: March 2011

ABSTRACTWe review Gas Source Molecular Beam Epitaxy of the GaAs/AlGaAs system. Among the growing number of condensed matter discoveries in materials grown by this approach we describe within resonant tunneling structures. This example serves to demonstrate the high quality quantum well formation and suppressed rate of dopant segregation that occurs during the GSMBE approach. We find a physical basis to quantify the latter growth effects when dopant segregation is viewed in two new ways. First, the broken translational symmetry created by the surface leads to dopant motion (as segregation) that otherwise is not allowed in the crystal interior (as diffusion). Secondly, dopants can dimerize on the crystal surface and this ultimately dictates how the rates of incorporation and segregation proceeds. The manner in which growth creates or destroyes covalent bonds of dopants on semiconductor surfaces thus presents new opportunities to improve dopant control.
The Negative Persistent Photoconductivity in the Deep Quantum Wells
Authors: Lo Ikai , Mttchel W. C. , Stutz C. E. , Yen M. Y. 
Published: March 2011

ABSTRACTWe have measured the Shubnikov-de Haas effect and Quantum Hall effect on the AlxGa1−xSb/InAs quantum wells for the A1 composition (x) from 0.1 to 1.0 under the negative persistent photoconductivity (NPPC) conditions. It confirmed the prediction of ionized deep donor model that the NPPC effect is a general property for the materials containing ionized deep donors at low temperatures. The time-dependent recombination (electron capture) of the ionized deep donors has the similar property to that of DX centers. The saturated reduction of carrier concentration in the InAs well increases with increasing x, and rises steeply at about x=0.4. By comparing with the concentration of the DX center-like deep donor in the bulk AlxGa1−xSb, we believe that the ionized deep donors which cause the NPPC in the AlxGa1−xSb,/InAs QW's are the DX center-like deep donors in the AlxGa1−xSb layers.
The Structure of GaAs Grown by Chemical Beam Epitaxy on Low-Temperature Cleaned Silicon
Authors: Xing Y. R. , Kiely C. J. , Goodhew P. J. 
Published: March 2011

ABSTRACTChemical beam epitaxy (CBE) has been used to grow GaAs on silicon with a low defect density after etching in HF followed by a low temperature (600°C) in situ heat treatment. High resolution electron microscopy (HREM) and convergent beam electron diffraction (CBED) studies show the presence of 90° and 60° dislocations and some inversion domains.
Cathodoluminescence Studies of Thermal Stress in Patterned GaAs/Si
Authors: Lingunis E. H. , Haegel N. M. , Karam N. H. 
Published: March 2011

ABSTRACTThermal stress distributions in patterned GaAs/Si are studied by low temperature cathodoluminescence spectroscopy. The MOCVD-grown samples have ben patterned in the form of stripes either by selective etching or by selective GaAs/Si growth using a SiO2 mask. In this work, the relevant stress components are determined as functions of position for stripes with different width to thickness ratios from low temperature (10 K) GaAs cathodoluminescence spectra and the results are discussed in comparison with finite element elastic calculations.
Strain-Relieved Reliable Lasers Grown on Si By MOCVD
Authors: Egawa Takashi , Hasegawa Yoshiaki , Jimbo Takashi , Umeno Masayoshi 
Published: March 2011

ABSTRACTConventional GaAs-based laser diodes grown on Si substrates suffer from rapid degradation, which results from the deteriorations of optical and electrical characteristics. Electroluminescence observation shows that the optical deterioration is caused by the formation of dark-line defects. The current-voltage (I-V) characteristic of the p-n junction is degraded with aging, and results in an ohmic-like under a higher ambient temperature and a larger forward current. The deterioration of the I-V characteristic is caused by defect-accelerated impurity diffusion because the growth of GaAs on Si substrates (GaAs/Si) involves the high dislocation density, the large tensile stress and the large amount of Si near the GaAs/Si interface. A significant improvement in reliability has been achieved in the strain-relieved AlGaAs/InGaAs laser diode on Si grown with the InGaAs intermediate layer. The stress relief by the InGaAs active layer and the reduction of the dark-line defect formation by the InGaAs intermediate layer are required to fabricate reliable GaAs-based laser diodes on Si substrates.
Optical, Electrical, and Structural Characterization of GaInAsP/InP Layers Grown on Silicon Substrate for 1.35 μm Laser Applications
Authors: Mobarhan K. , Jelen C. , Kolev E. , Razeghi M. 
Published: March 2011

ABSTRACTA 1.35 μm wavelength GaInAsP / InP double heterostructure laser has been grown on Si substrate by low-pressure metalorganic chemical vapor deposition. The layers are grown directly on Si substrate coated with GaAs. Material characterization confirms the overall quality of the epitaxial layers, including excellent crystallinity and optical properties in addition to precision control over the growth, composition and doping of the different layers. Pulsed operation with output power of over 200 mW per facet was achieved at room temperature for a broad area laser with 20 μm width and 170μm cavity length.
High-Quality InSb Growth on GaAs and Si by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Choi Y. H. , Sudharsanan R. , Besikci C. , Bigan E. , Razeghi M. 
Published: March 2011

ABSTRACTWe report the first InSb film growth on Si by low-pressure metalorganic chemical vapor deposition. High-quality layers of InSb have been grown on Si and GaAs substrates. InSb films displayed mirror-like morphology on both substrates. X-ray full width at half maximum of 171 arcsec on GaAs and 361 arcsec on Si for a InSb layer thickness of 3.1 μm were measured. Room-temperature Hall mobilities of 67,000 and 48,000 cm2/V.s with carrier concentration of 1.5×1016 and 2.3×1016 cm−3 have been achieved for InSb films grown on GaAs and Si substrates, respectively. A 4.8 μ-thick InSb film on GaAs exhibited mobility of 76,200 cm2/Vs at 240 K.
SiGe/Si-Bipolar and Quantum Well Transistors, Results and Prospects
Authors: KÖNIG ULF 
Published: March 2011

ABSTRACTThe quality of SiGe/Si heterodevices recently could be improved by depositing on a SiGe buffer with a Ge grading. In house MBE grown structures reached 1.5 K mobilities of 173000 cm2/Vs. Also at room temperature (RT) the mobility is up to 4 times higher than in bulk Si or SiGe. HBTs in the discussed material system can exceed performances of conventional Si-homobipolar transistors, already with relaxed design rules. I briefly review on mesa - like SiGe HBTs with high fmax and fT around 50 GHz, owing to low base sheet resistances <1Kω□. In DC-operation high gains >400 or 13 000 at RT or 77K were obtained, n - and p - channel Si, SiGe and Ge MODFETs will be presented in more detail, n- MODFETs exhibit high transconductances above 300 mS/mm at RT and almost 1000 mS/mm at 77K. Different effects will be discussed, e.g. the influence of the gate to channel distance and effects of rapid thermal activation. Si/Ge heterosystems offer exclusive properties, e.g. the same mobility in a Si - 2DEG and a Ge - 2DHG. Complementary MODFETs (CMOD) can be envisaged. Furtheron the Si/Ge system allows the monolithic integration of heterodevices with high complexity Si - ICs (heterointegration).
Boron Diffusion in Si1−x Gex Strained Layers
Authors: Moriya N. , King C. A. , Feldman L. C. , Luftman H. S. , Green M. L. , Bevk J. , Weir B. E. 
Published: March 2011

ABSTRACTBoron diffusion in Sia7 Gea3 strained layers has been studied as a function of annealing temperature and is compared to boron diffusion in unstrained Si epitaxial layers. A lower diffusivity was observed in Sia7 Gea3 strained layers as compared to the Si control samples. Using the well-accepted model for boron diffusion via charged point defects in Si, the intrinsic diffusivities of the boron atoms in the Sia7 Gea3 layers were derived and an activation energy of 4.4 eV was estimated for the diffusion process.A new approach to describe the diffusion process is also presented here. In this model, we relate the lower diffusivity to a corresponding change in the charged point defect equilibrium concentration caused by a change in band-gap due to the strain and the existence of foreign atoms in a Si matrix.
Raman Scattering Studies of Si1−xGex Layers Grown by Atmospheric Pressure Chemical Vapor Deposition
Authors: Perry C. H. , Lu Feng , Namavar F. , Rowell N. L. 
Published: March 2011

ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08≤x≤0.2). The samples were grown using atmospheric pressure chemical vapor deposition techniques. Layer thicknesses varied from 0.1 — 10μm. The relative frequency shift of the Si-Si phonon mode for the SiGe strained epilayers from an incommensurate pseudo-alloy of the same composition is used as a quantitative measure of the lattice strain. For thicknesses below a critical value the Raman data indicate that the films are highly strained and the growth is commensurate with the substrate whereas thicker films are partially or fully relaxed. Phonon lines are sensitive to the interfaces and alloy layers. The results are consistent with other characterization studies, such as TEM and X-ray rocking curve measurements, of the same samples.
Structural Investigation of Photoluminescent Porous Si by Transmission Electron Microscopy
Authors: Shih S. , Jung K. H. , Kwong D. L. 
Published: March 2011

ABSTRACTWe have developed a new, minimal damage approach for examination of luminescent porous Si layers (PSLs) by transmission electron microscopy (TEM). In this approach, chemically etched PSLs are fabricated after conventional plan-view TEM sample preparation. A diffraction pattern consisting of a diffuse center spot, characteristic of amorphous material, is primarily observed. However, crystalline, microcrystalline, and amorphous regions could all be observed in selected areas. A crystalline mesh structure could be observed in some of the thin areas near the pinhole. The microcrystallite sizes were 15–150 Å and decreased in size when located further from the pinhole.