bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Time Resolved Photoluminescence of Nanoscale InP Islands in In0.48Ga0.52P
Authors: Eberl K. , Kurtenbach A. , HÄusler K. , Noll F. , RÜhle W.W. 
Published: April 2011

ABSTRACTNanoscale InP islands are formed during InP/In0 48Ga0.52P heteroepitaxy due to the lattice mismatch of about 3.7%. The samples are prepared by solid source molecular beam epitaxy on (001) GaAs substrate. Atomic force microscopy measurements show that the size of the islands is typically 15 to 50 nm in diameter and about 5 to 10 nm high depending on the nominally deposited InP layer thickness, which is between 1 and 7.5 monolayers. Transmission electron micrographs show the coherent incorporation into the In0.48Ga0.52P matrix for InP islands with 2.5 monolayers. Resonantly excited time-resolved photoluminescence (PL) measurements of the self assembling InP dots are performed for optical characterisation. The decay times are typically 400 ps. The dependence on excitation power and temperature indicates the quantum dot nature of the InP islands. Finally a pronounced alignment of the InP islands is obtained on strained In0.61Ga0.39P buffer layers.
Dielectric Function and Band Gaps of Si1−xCx AND Si0.924−xGe0.076Cx (0≤x≤0.014) Semiconductor Alloys Grown on Si
Authors: Lee Hosun , Floro J.A. , Strane J. , Lee S. R. , Jones E. D. , Mayer T. , Picraux S. T. 
Published: April 2011

ABSTRACTWe have characterized the optical properties of heteroepitexial Si1−xCx and Si0.924−xGe0.076Cx (0≤x≤0.014) alloys grown on Si substrates by solid phase epitaxy using spectroscopic ellipsometry. The measured dielectric function confirms that the samples are of good crystalline quality. We determined the E1 and E2 band gaps by lineshape-fitting the features in the second derivative spectra of the dielectric functions. Also, we discuss the shift of the band gaps with C concentration arising from strain and chemical alloying.
Structural and Compositional Study of Sil-xGex Multilayer Structures Using Medium Energy Ion Scattering
Authors: Hucknall P.K. , Sugden S. , Sofield C.J. , Noakes T.C.Q , Mcconville C.F. 
Published: April 2011

ABSTRACTThe ability to determine structural and compositional information from the sub-surface region of a semiconductor material has been demonstrated using a new time-of-flight medium energy ion scattering spectroscopy (ToF-MEISS) system. A series of silicon-silicon/germanium (Si/Sil-xGex) hetero-structure and multilayer samples, grown using both solid source molecular beam epitaxy (MBE) and gas source chemical vapour deposition (CVD) on Si(100) substrates, have been investigated. These data indicate that each individual layer of Sil-xGex can be uniquely identified with a depth resolution of approximately 3 nm. A comparison of MBE and CVD grown samples has also been made using layers with similar structures and composition and the results compared with conventional Rutherford back-scattering spectrometry (RBS).
Calculation of Optical Characteristics for Si1-xGExAlloy
Authors: Litovchenkoe V. G. , Frolov S. I. , Shkarban B. N. , Kruger D. 
Published: April 2011

ABSTRACTIn the framework of virtual crystal approximation using the empirical pseudopotential theory optical transitions of Si1 -xGexhave been calculated. The effects of hydrostatic and uniaxial stress, and alloy stoichiometry on the optical gaps were investigated. Since the mechanical stress and material composition affect the distinctive behaviour of different optical transitions it allows to put forward a spectral measurement technique for determination of crystal lattice strain and alloy parameter x simultaneously.
A New Approach for Determining Epilayer Strain Relaxation and Composition Through High Resolution X-Ray Diffraction
Authors: Matney K. M. , Goorsky M.S. 
Published: April 2011

ABSTRACTWe developed a new method of determining epilayer relaxation (along one direction) and composition using a symmetric and any single asymmetric high resolution x-ray diffraction scan. The previous use of small angle approximations can be very detrimental to calculated results and should be avoided. This new method does not employ small angle approximations or first order Taylor approximations, producing accurate results. The effect of x-ray geometry (glancing incident versus glancing exit) on the analysis of epilayer composition and strain is also reviewed. It is also shown that the glancing exit geometry is generally less susceptible to experimental error.
Effects of Strain-Induced Defects on Excess Carrier Lifetime and Ambipolar Diffusion in nipi-Doped In0.2Ga0.8As/GaAs Mqws
Authors: Lin H.T. , Rich D.H. , Larsson A. 
Published: April 2011

ABSTRACTThe effects of strain-induced defects on excess carrier lifetime and transport in a nipi-doped In0.2Ga0.8As/GaAs multiple quantum well (MQW) structure were examined with a new method called electron beam-induced absorption modulation (EBIA) in which the kinetics of carrier transport and recombination are examined with a high-spatial, -spectral and -temporal resolution. The excess carrier lifetime and ambipolar diffusion were found to be reduced by factors of ∼1013 and ∼103 compared to theoretical values, respectively, and this is attributed to the presence of strain-induced defects. The MQW excitonic absorption coefficient sensitively depends on the carrier density in the QWs, as a result of screening of the electron-hole (e-h) Coulombic interaction. Likewise, ambipolar diffusion is found to depend on the excess carrier density in a nonlinear fashion, as a result of the e-h plasma-induced changes in the local depletion widths in the vicinity of structural defects.
Effects of Silicon Misorientation Angle on the Rf and Dc Characteristics of GaAs-on-Si Mesfets
Authors: Papavassiliou Christos , Constantinidis G. , Kornilios N. , Georgakilas A. , LÖchterman E. , Panayotatos P. 
Published: April 2011

ABSTRACTA systematic experimental investigation has been undertaken for the optimization of the wafer parameters and processing for silicon wafers intended for use as substrates for MBE growth, with emphasis on heteroepitaxial growth of GaAs-on- Si. Within this investigation, results are presented of an initial study focused on the optimization of the magnitude of the misorientation angle towards a <110> direction for the growth of GaAs on (001) Si wafers. This angle controls the structure of the stepped (001)Si surface and can influence the defect density and surface smoothness of the GaAs-on-Si layers. Silicon substrates misoriented from 0 deg. up to 9 deg. were cut to specification and subsequently used for the epitaxial growth of GaAs MESFET structures. MESFETs were fabricated and their dc and RF characteristics compared. The resistivity of the GaAs-on-Si buffer layers was evaluated and correlated to the results from device characterization. This work presents the effects of the magnitude of the angle of misorientation in the range from 0 to 9 deg.
Degradation and Recovery of Si1−xGex Devices by Irradiation
Authors: Ohyama H. , Vanhellemont J. , Takami Y. , Hayama K. , Kudo T. , Hakata T. , Kobayashi K. , Sunaga H. , Hironaka I. , Poortmans J. , Caymax M. 
Published: April 2011

ABSTRACTResults are presented of a study on the degradation and recovery behavior of strained Si 1−xGex diodes and heterojunction bipolar transistors (HBTs) by electron and neutron irradiation. The degradation of device performance and the generation of lattice defects are reported as a function of germanium content and radiation source. Isochronal annealing is performed to study the recovery behavior of the irradiated devices. The radiation source dependence of the degradation is discussed taking into account the absorbed energy dunng irradiation.
Boron Diffusion in Si and Si1−xGex
Authors: Kuo P. , Hoyt J. L. , Gibbons J. F. , Turner J. E. , Lefforge D. 
Published: April 2011

ABSTRACTBoron diffusion in in-situ doped Si and strained Si1−xGex (x < 0.20) epitaxial layers, subjected to inert-ambient furnace annealing, was investigated as a function of temperature (T = 750 °C - 850 °C). Boron diffusivity parameters were extracted from SUPREM IV, a process simulation program. We observed slower B diffusion in strained Si1−xGex relative to that in Si for B concentration levels ranging from 2×1017 to 3×1019 cm−3. Using relaxed graded Si1−xGex as “substrates”, we also characterized B diffusion in relaxed Si1−xGex (x < 0.60) at T = 800 °C. We propose a reaction of mobile B atoms pairing with Ge atoms to model the slower B diffusion in both fully strained and relaxed Si1−xGex.
Low Temperature SiGe Heteroepitaxy by Ultrahigh Vacuum Electron Cyclotron Resonance Chemical Vapor Deposition
Authors: Joo Sung-Jae , Hwang Ki-Hyun , Hwang Seok-Hee , Yoon Euijoon , Whang Ki-Woong 
Published: April 2011

ABSTRACTDislocation-free Si1−xGex epilayers are successfully grown on (100) silicon at 440°C by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition (UHV-ECRCVD). The effects of process parameters on the crystallinity of Si1−xGex epitaxial layers were studied. As the GeH4 flow rate increases and consequently Ge fraction increases above 20%, Si1−xGex epilayers become damaged heavily by ions. When Ge fraction is larger than 20%, process parameters like total pressure need to be adjusted to reduce the ion flux for high quality Sil−xGex. Growth rate of Si1−xGex epitaxial layers increases at 440°C with Ge content in the film. It is presumed that the hydrogen desorption from the surface is the rate-limiting step, however, the enhancement in growth rate is comparatively suppressed and delayed.
Defect-Free Band-Edge Photoluminescence in SiGeC Strained Layers Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Liu C. W. , Amour A. St. , Sturm J. C. , Lacroix Y. R. J. , Thewalt M. L. W. 
Published: April 2011

ABSTRACTThe defect-free band-edge photoluminescence at both 30K and 77K was observed for the first time in Si/SiGeC/Si quantum wells. The SiGeC samples were prepared by rapid thermal chemical vapor deposition (RTCVD) by using methylsilane as carbon source added in a dichlorosilane and germane mixture. Deep photoluminescence around 0.8 eV, previously reported by Boucaud et al., was no longer observed under any excitation conditions. Compared to control Si/SiGe/Si quantum wells, the initial effect of adding the C is to decrease the bandgap of the host SiGe layers, despite the fact that the diamond has a large bandgap.
The Effects of Rapid Recrystallization and Ion Implanted Carbon on The Solid Phase Epitaxial Regrowth of Si1−xGex Alloy Layers On Silicon
Authors: Antonell M.J. , Haynes T.E. , Jones K.S. 
Published: April 2011

ABSTRACTTransmission electron microscopy has been combined with time-resolved reflectivity and ion channeling to study the effects of regrowth temperature and carbon introduction by ion implantation on the solid phase epitaxial regrowth (SPER) of strained 2000Å, Sio.88Ge0.12/Si alloy films grown by molecular-beam epitaxy (MBE). Relative to the undoped layers, carbon incorporation in the MBE grown SiGe layers prior to regrowth at moderate temperatures (500- 700°C) has three main effects on SPER; these include a reduction in SPER rate, a delay in the onset of strain-relieving defect formation, and a sharpening of the amorphous-crystalline (a/c) interface, i.e., promotion of a two-dimensional (planar) growth front.1 Recrystallization of amorphized SiGe layers at higher temperatures (1 100°C) substantially modifies the defect structure in samples both with and without carbon. At these elevated temperatures threading dislocations extend completely to the Si/SiGe interface. Stacking faults are eliminated in the high temperature regrowth, and the threading dislocation density is slightly higher with carbon implantation.
Influence of Hydrogen On The Solid Phase Epitaxial Regrowth of Strained Layer Silicon Germanium Alloys
Authors: Love D. , Endisch D. , Simpson T.W. , Lowes T.D. , Mitchell I.V. , Baribeau J.-M. 
Published: April 2011

ABSTRACTStrained layer Si/Si0.79Ge0.21 superlattices consisting of 16 alternating 19.0 nm Si0.79Ge0.21 / 18.5 nm Si layers have been amorphized by Si ion irradiation, then implanted with H ions to nominal atomic concentrations of 1%, 0.1% and 0.05% within the amorphized region. Subsequent solid phase epitaxy (SPE) at a regrowth temperature of 575°C was monitored in situ by time resolved reflectivity (TRR) measurements, while changes in the H distribution were measured by elastic recoil detection analysis (ERDA). Analysis was supplemented by Rutherford backscattering spectrometry (RBS), x-ray double crystal diffraction and reflectivity (DCD/XRF) and transmission electron microscopy (TEM). TRR data reveals a decrease in the initial SPE rate in the Si substrate from 4.9 Å/sec (no H) to 2Å/sec for 1% H concentration as well as a rate decrease as the interface enters the Si/SiGe layers. TRR also indicates an increased roughness in the crystal/amorphous interface with increasing H concentration. ERDA reveals that a significant fraction of the implanted H is stable in the amorphous region for the anneal times (10-30 min) at 575°C, while in the regrown lattice the H concentration has dropped below 20 ppm, near the detection limit of the ERDA. DCD shows almost no strain in the regrown structures. TEM and RBS channeling techniques reveal degradation in the crystal quality of epitaxially regrown structures and a large concentration of strain relieving defects originating near the second deepest of eight SiGe layers in all regrown structures. XRF indicates decreasing sharpness of the regrown Si/SiGe interfaces with increasing H concentration.
A New type of Graded Buffer Layer for Gas-Source Molecular Beam Epitaxial Growth of Highly Strained INxGA1−XP/GAP Multiple Quantum Wells on Gap
Authors: Bi W. G. , Tu C. W. 
Published: April 2011

ABSTRACTA new type of graded buffer layer, called graded short-period superlattice (GSSL) buffer layer, is proposed, and its effect on improving the material quality is investigated by comparing the qualities of 50-period InGaP/GaP multiple quantum wells (MQWs) grown on top of it and on a linearly graded (LG) buffer layer. Unlike the linearly graded buffer layer, in which the In composition is changed 1% per step size with a constant composition InGaP, the new buffer uses InGaP/GaP short-period superlattice within each step, while maintaining the average In composition of the short-period superlattice being changed the same amount per step size. Characterization of these structures by high-resolution X-ray diffraction and low-temperature photoluminescence indicates that, while the MQWs grown on a GSSL buffer show comparable structural properties as compared with those on an LG buffer, they exhibit higher PL intensity and narrower PL line width.
Layer Tilt and Relaxation in InGaAs/GaAs Graded Buffer Layers
Authors: Matney K.M. , Eldredge J.W. , Goorsky M.S. 
Published: April 2011

ABSTRACTWe investigated the effect of substrate inclination and direction on the structural properties of an InGaAs linearly compositionally graded buffer layer with a AlGaAs/InGaAs superlattice grown by molecular beam epitaxy on 2° offcut GaAs substrates. Reciprocal space maps were used to determine the relaxation and tilt of the buffer layer and superlattice with respect to each other and to the substrate. From (004) reciprocal space maps, a linear relationship between tilt and In mole fraction was observed for the buffer layer. This tilt was greatly reduced near the top of the buffer which was found to be completely strained. Interestingly, the tilt along a <110> direction was greater than that observed along the miscut axis. This may be due to the miscut axis not being parallel to a low index plane. Reciprocal space maps of asymmetric diffraction planes were used to determine the relaxation of the buffer layer as a function of In mole fraction. Along a <110> direction in which no tilt was seen in the (004), the majority of the buffer layer was found to be completely relaxed. However, the top of the buffer layer was found to be completely strained, corresponding to a denuded zone observed in cross section transmission electron microscopy.
Simulation of the Growth of Lattice Mismatched Semiconductors
Authors: Rouhani M. Djafari , Malek R. , Gue A.M. , Esteve D. 
Published: April 2011

ABSTRACTWe have studied the growth of lattice mismatched semiconductors through the association of the Monte Carlo technique and the Valence Force Field (VFF) approximation. The Monte Carlo technique monitors the atomic motion in the deposited layer using the Arrhenius law and taking into account the impingment of atoms from the gas phase, intralayer and interlayer migrations of atoms and evaporation from the surface. The VFF approximation is used as an energy model to determine the local strain and stress inside the deposited layer by minimizing the total energy. This is performed after each single atomic motion. The strain is assumed to enhance the atomic motion by lowering the activation energy barrier related to the particular event. Results concerning the case of large lattice mismatches are presented. It is observed that the growing surface becomes rapidly rough, showing grooves with (111) facets. The strain relaxation occurs as a result of this roughening and allows the determination of the critical thickness. At higher lattice mismatches, it is seen that the layer orientation changes from(100) to (111) from the beginning.
Etching Reactions at Solid Surfaces
Authors: Winters Harold F. , Coburn J. W. 
Published: April 2011

AbstractAn understanding of etching reactions in a plasma environment requires a knowledge of: (1) the types of gas phase particles which react at the surface, (2) the etch products formed, and (3) the processes which lead from reactants to products. Experimental data relavant to these topics are reviewed in this paper. A conceptual framework for understanding the etching reaction is reviewed and it is shown that the experimental data presently available is consistent with this framework. The influence of ion bombardment on etching reactions is extensively discussed.
Non-Stoichiometry and the Electronic Structure of Amorphous Silicon Nitride
Authors: Ley L. , Kaercher R. , Johnson R. L. 
Published: April 2011

AbstractWe have measured core-, valence-, and conduction band densities of states of amorphous hydrogenated (a-SiNx:H) and unhydrogenated (a-SiNx) silicon nitride with x varying between 0 and 2. From an analysis of the Si 2p core level spectra in terms of five chemically shifted components the number of Si-N bonds is calculated and compared to the total nitrogen concentration. Above x ≈ 0.8 the average silicon coordination of nitrogen starts to deviate from three. The addition of hydrogen increases this deviation because N-H bonds are favored over N-Si bonds accounting thus for the excess nitrogen concentration (x ≥ 1.33) found in hydrogenated samples. A band of N2p lone pair states is identified at the top of the valence bands in stoichiometric Si3N4. This band determines the character and position of the valence band maximum (VBM) above x = 1.1. Below x = 1.1 Si-Si bonding states mark the VBM. The conduction band minimum (CBM) is determined by Si-Si antibonding states up to x = 1.25 and its position relative to the core levels is virtually unaffected by the presence of nitrogen or hydrogen. Above x = 1.25 a percolation-like transition to Si-N antibonding states occurs which is accompanied by a sharp recession of the CBM. The position of the Fermi level within the gap is investigated as a function of x and hydrogen content. Si-H and N-H bonding states are identified at 6.3 and 9.8 eV below the VBM in nearly stoichiometric a-Si3N4. Si-Si bonding defect states lie 0.5 to 1.0 eV above the VBM and the corresponding antibonding states (3.0 ± 0.3) eV above the VBM.
Deposition of Amorphous Carbon Films from Laser-Produced Plasmas
Authors: Marquardt C. L. , Williams R. T. , Nagel D. J. 
Published: April 2011

AbstractAmorphous carbon films deposited by sputtering or ion-beam techniques, as well as a-C:H films produced by glow discharge in hydrocarbon vapor, can exhibit interesting and desirable properties such as hardness, wide optical gap, high resistivity and chemical inertness. A critical parameter common to all methods for producing such films appears to be kinetic energy of the ions or atoms incident on the growing film. We report an investigation of laser-produced carbon plasmas as a deposition source which can supply ions and atoms having energies requisite for the production of hard carbon films. The plasmas were generated by focusing 1.06 μm radiation from a Q-switched Nd:YAG laser onto a carbon rod which could be rotated within the vacuum chamber to present a fresh surface for each shot. Plasma temperature, varied as a function of laser pulse energy, was monitored by recording X-UV plasma emission spectra during deposition. Films having thicknesses up to ˜0.5 μm were deposited on various substrates and were evaluated by microscopic inspection, thickness profiling, optical transmission measurements and hardness testing. Hardness increased significantly with plasma temperature, from about 3 to over 7 on the Mohs scale. There was no corresponding increase in optical gap, which remained near 0.4 eV for all films.
Plasma Deposition of Amorphous Metal Alloys
Authors: Hays Auda K. 
Published: April 2011

AbstractRapid solidification, sputtering and electroless chemical deposition have been used to produce amorphous metal alloys which possess excellent corrosion and abrasion resistance. This paper discusses a new technique for obtaining amorphous metal alloy coatings. This technique consists of dissociating mixtures of organometallics (metal carbonyls) and metalloid hydrides in a hydrogen carrier gas using a radio-frequency discharge. In particular, the formation of Ni-P alloys is discussed.Plasma decomposition of Ni(CO)4 and PH3 in argon and hydrogen carrier gases [Ni(CO) 4/PH3˜8/l] yielded films that were black and silver, respectively, in appearance. Both films were amorphous as determined by transmission electron microscopy. Films deposited using a hydroqen carrier gas were three orders of magnitude more conductive than those deposited using an argon carrier gas. Analysis of both films using electron microprohe analysis and inductively-coupled plasma spectroscony showed an enrichment of P in the films over the P content in the plasma qas mixtures. Reducinq the P content of the plasma gas mixture [Ni(CO)4/PH3˜17/Il yielded crystalline films with no P enrichment. The grain size in these films was ˜Å as determined by x-ray line-broadeninq.Using Auger electron spectroscopy, films deposited using hydroqen and argon carrier gases were determined to have, in addition to Ni and P, small amounts of carbon (8–12 at%) and oxygen (1–4 at%). Infrared spectra of both crystalline and amorphous films showed chemisorhed CO.
Amorphous Polyphosphide Thin Films Prepared by Sputtering
Authors: Schachter Rozalie , Viscogliosi Marcello 
Published: April 2011

AbstractA sputtering method to prepare amorphous polyphosphide thin films has been investigated. The method consists of sputtering from a polyphosphide (KP15) target and plasma cracking of a P4 vapor stream injected into the plasma from an external phosphorus source. From the deposition rates of KP15 thin films, we determine that the plasma cracking efficiency of the P4 molecule into reactive P species required for compound growth is significantly higher than thermal cracking efficiency. We conclude that this method is applicable to other compound semiconductors (InP) and that the P4 delivery system used here should be useful in other techniques such as MBE or OMCVD