bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Interface Mixing in a Symmetrically Strained Ge/Si Superlattice
Authors: Bowman R. C. , Adams P. M. , Chang S. J. , Arbet V. , Wang K. L. 
Published: March 2011

ABSTRACTRaman scattering and x ray diffraction were used to study the effects of annealing on a Ge/Si superlattice that had been grown upon a Ge0.4Si0.6 alloy buffer layer which distributes the strain between the layers. Anneals above 910K caused substantial mixing at the Ge-Si interfaces. The interdiffusion coefficients obtained from the x-ray data were found to obey an Arrhenius relation with an activation energy of 3.1±0.2eV. Initial intermixing seems to be dominated by the diffusion of Si atoms into the Ge layers via a vacancy mechanism.
Defects at the Interface of GaAsxP1−x/Gap Grown by Vapor Phase Epitaxy
Authors: Takeda Seiji , Hirata M. , Fujita H. , Sato T. , Fujii K. 
Published: March 2011

ABSTRACTDefects and microstructures in a ternary GaAsxP−x compound have been studied by transmission electron microscopy. The compound was grown on a (100) GaP substrate by vapor phase epitaxial. Crystal growth striation contrast was detected in a TEM image. This contrast was explained by local compositional variation of As and P. The distribution of misfit dislocations in the interface region was also studied.
Effects of Charge Transfer on the Microscopic Theory of Strain-Layer Epitaxy
Authors: Tsu Raphael , Zypman Fredy , Greene Richard F. 
Published: March 2011

ABSTRACTWhenever an atom of As is substitutionally replaced by a P-atom in a compound such as GaAs, due to the difference in ionicity, local puckering is effected by charge transfer. This paper deals with a calculation of the total energy stored, Eex = E(strain) + E(interface) = Es + Eint. For thick epilayers of GaP on GaAs, Eex is dominated by Es. However, for severalatomic layers of GaP on GaAs, the dominant stored energy is actually represented by the electrical dipole-dipole energy at the interface. The creation of dislocations may release the strain energy, it cannot affect the interface dipoleterm. Only inter-diffusion can lower the interface energy.
Formation of Insulating Layers in GaAs-Aigaas Heterostructures
Authors: Hobson W. S. , Pearton S. J. , Abernathy C. R. , Neida A. E. Von 
Published: March 2011

ABSTRACTWe describe two methods for producing thermally stable high resistivity layers in GaAs-AlGaAs heterostructures. These rely on the interaction of implanted ions with dopant impurities already present in a buried layer in the heterostructure. In the first case, oxygen implanted at a concentration above that of the acceptors in p-type GaAs is shown to create thermally stable, highresistivity material only in the case of Be-doping in the GaAs. The effect is not seen for Mg-, Znor Cd-doping. Similarly there is no apparent interaction of 0 with n-type dopants (S or Si). The Be-O complex in p-type GaAs is a deep donor, creating material whose sheet resistivity shows a thermal activation energy of 0.59 eV. In the second case oxygen implantation into n+ AlGaAs, followed by annealing above 600°C, creates a deep acceptor level that compensates the shallow donors in the material. Temperature dependent Hall measurements show the resistivity of the compensated AlGaAs has a thermal activation energy of 0.49 eV, in contrast to a value of 0.79 eV for non-induced damage compensation.
Defect Heterojunction Model for Anomalous Photoresponse of P/N GaAs Grown on N-Ge Substrates
Authors: Partain Larry , Grounner Marc 
Published: March 2011

ABSTRACTA GaAs p/n junction grown on a n-Ge substrate has an anomalous photoresponse that includes a quantum yield response starting at the 0.7-eV band edge of Ge. In terrestrial sunlight, its I-V characteristic has an anomalous “notched” shape that is progressively removed by increasing the infrared light content. The I-V is well modeled by a space-charge-limited-current diode theory with a GaAs/Ge interface defect density of 1.92 (1012) cm−2 eV−1 at 0.4 eV below the conduction band edge. Similar defect densities have been reported for GaAs/oxide interfaces and for a GaAs p/n junction interface specially selected for high defect densities.
Crystallinity of Isolated Silicon Epitaxy (ISE) Silicon-on-Insulator Layers
Authors: Allen L.T.P. , Zavracky P.M. , Vu D.P. , Batty M.W. , Henderson W.R. , Boden T.J. , Bowen D.K. , Gorden-Smith D. , Thomas C.R. , Tjahjadi T. 
Published: March 2011

ABSTRACTIsolated silicon epitaxy (ISE) is a proven method of producing single crystalline silicon-on-insulator (SOI) material with excellent electrical properties. The presence of the remaining isolated dislocation trails in the epitaxial silicon has led to this investigation of the crystallinity throughout the ISE SOI layer and across the isolated dislocations. The structural perfection of these layers has been examined by defect etching, Nomarski optical microscopy, electron channeling patterns, and with more sensitivity using double crystal synchrotron X-ray diffraction and topography. Defect etching reveals the dislocation density within the layers of production ISE SOI material to be ~5×l0 5 /cm2. Electron channeling pattern techniques have reached the resolution limit of angular orientation resolution for the isolated silicon layer. Finally, synchrotron studies have shown that orientation homogeneity across 5" wafers are preserved to 0.006° and the variation in orientation across the defect trails to be, in general, less than 10 arcsec (0.003°), indicating single crystalline ISE SOI production material.
EPR Studies of DX Center Related Paramagnetic States in Ga0.69 Al0.31 As:Sn
Authors: Von Bardeleben H.J. , Bourgoin J.C. , Basmaji P. , Gibart P. 
Published: March 2011

ABSTRACTThe electron paramagnetic resonance study of the DX center in Sn doped direct gap Ga0.69Al0.31 As shows the existence of a shallow effective mass like excited configuration of this defect. The photoexcitation spectrum for this transformation has a threshold at 0.8 eV; the photoionization of the DX center is not a transition to the lowest r conduction band as previously assumed. After photoexcitation additional paramagnetic defects are observed.
Electron-Radiation-Induced Epitaxial Growth of CoSi2 on Si(111)
Authors: Nieh C. W. , Lin T. L. , Fathauer R. W. 
Published: March 2011

ABSTRACTWe report electron-radiation-induced epitaxial growth of CoSi2 on Si(111) from an amorphous Co/Si 1:2 mixture with epitaxial CoSi2 nuclei. Under the electron beam of a Philips EM430 electron microscope, the epitaxial nuclei grow parallel to the surface with a growth rate orders of magnitude higher than that for thermally activated growth. The substrate temperature during irradiation and the electron energy dependence were studied. Electron-radiation-induced growth shows very weak temperature dependence in the temperatures between 100°K and 300°K and the activation energy is 0.03 eV. The growth rate increases significantly as the electron energy increased to 200 KeV which is about the threshold energy for displacing Si atoms.
Electric Field Dependence of the Electron Drift Velocity in Hydrogenated Amorphous Silicon
Authors: Devlen R. I. , Schiff E. A. , Tauc J. , Guha S. 
Published: March 2011

ABSTRACTWe present room temperature measurements on the electron drift velocity in hydrogenated amorphous silicon (a-Si:H) for large electric fields (1.3 × 105 to 3 × 105 cm/s). The experimental time resolution was ˜ 1ps and velocities as high as 8 × 105 cm/s were observed. The electron transport was non-dispersive, and the velocity was found to be a superlinear function of the applied field.
Study of the Density of Bulk Gap States in Undoped a-Si:H by Depletion Width Modulation Electron Spin Resonance
Authors: Essick J. M. , Cohen J. D. 
Published: March 2011

ABSTRACTThe density of gap states in the bulk of intrinsic a-SiH has been probed using depletion width modulation electron spin resonance spectroscopy (DWM ESR) as well as complementary capacitance techniques. Our sample consists of a 2.85 micron thick layer of undoped a-Si:H sandwiched between a large area Pd Schottky barrier contact and a p+ c-Si substrate, allowing charge-counting capacitance and spin-counting ESR measurements to be performed on the same sample. DWM ESR measures the spin change that occurs when electrons are removed from gap states by increasing reverse bias on a Schottky barrier. The phase of the signal indicates whether unpaired spins are created or destroyed with increasing bias, thus revealing the defect charge state at the Fermi level The DWM ESR signal from our sample indicates that removing electrons from gap states leads to a reduction of the spin signal. This is qualitatively consistent with a band of Do states near EFo. However, for all metastable states and at all temperatures studied, the magnitude of the DWM ESR signal account for only about 14% of the responding charge as determined by junction capacitance. This would occur only if the majority of the filled bulk gap states were doubly occupied with a small correlation energy Ueff. In that case the majority of transitions caused by depletion width modulation would be D−/D+ which would produce no spin change. Model calculations show that the small observed Do/D+ DWM ESR signal would indeed result from the occupation statistics for a near zero value of Ueff at the moderate temperatures of the experiment. Comparison with our data sets the overall limits If −20meV < Ueff < 50 meV. Implication for recent models of the density of states in intrinsic a-Si:H are discussed.
Emission Energy Dependence of Transient Photoluminescence in Hydrogenated Amorphous Silicon
Authors: Longeaud C. , Merk E. 
Published: March 2011

ABSTRACTThe dependence upon emission energy of the transient photoresponse of photoluminescence in amorphous silicon in the time range 100 ns to 20 μs, and for temperatures between 100 K and 160 K has been the subject of a detailed study. Analysis of this dependence, as a function of temperature, is carried out in terms of band tail carrier thermalisation and recombination. By using the simple multiple trapping treatment for the thermalisation of photoexcited carriers in their respective band tails, and by allowing for a fast time- and temperaturedependent recombination through defects deep in the gap, we are able to reproduce the correct energy and time dependence, as well as the temperature behaviour. On the basis of this analysis, the significance of the dispersive parameters deduced from transient photoluminescence decays is discussed. Comparison with the results of transient experimental techniques such as time of flight will be given.
Substrate Interactions in the Formation of Amorphous Silicon/Dielectric Interfaces
Authors: Parsons G. N. , Kim S. S. , Lucovsky G. 
Published: March 2011

ABSTRACTUsing Remote PECVD we have deposited layers of “device quality” a-Si:H and Si-based dielectrics. We find that the formation of depletion or accumulation layers at a-Si:H/dielectric interface depends on the specific dielectric (SiO2 or Si3N4) and on the film deposition sequence. In addition, we have studied process-gas/substrate interactions by in-situ Auger Electron Spectroscopy (AES) and determined that Si-O or Si-N bonds are produced at a-Si and c-Si surfaces exposed to plasma excited He/O2, or NH3 mixtures, respectively. These process-gas/substrate interactions occur in parallel with film deposition and are correlated with the electronic properties of the interfaces, and the layer deposition sequence.
Raman Studies of Boron Induced Structural Changes in Amorphous Silicon-Boron Alloys
Authors: Yang G. , Bai P. , Tong B. Y. , Wong S. K. , Hill I. 
Published: March 2011

ABSTRACTA new amorphous Si1-x.Bx. alloy with composition of boron x ranging from 0.01 to 0.5 was produced in a low pressure chemical vapor deposition (LPCVD) system. We performed Raman scattering experiments on the a-Si1−xBx alloys and specifically monitored the Si-Si TO-like mode at around 480cm−1 and the TA-like mode at around 130cm−1. A pronounced broadening of the TO-like band as well as a decrease of the intensity ratio ITo/ITA are observed with an increase of boron concentration in the a-Si1−x Bx alloys. Based on the Raman spectra, the structural changes induced by boron incorporation in the a-Si network are discussed in the conceptual framework of the continuum random network (CRN) model. We conclude that boron incorporation enhances the structural disorder and induces topological changes in the amorphous network.
The Determination of the Quality of a-Si:H Films for Application in Solar Cells
Authors: Grunow P. , Herm D. , Könenkamp R. , Küppers U. , Kunst M. , Neitzert H. C. , Werner A. 
Published: March 2011

ABSTRACTSeveral stationary and transient techniques are used to characterize a large number of intrinsic a-Si:H films prepared in a narrow range of production conditions. Correlation between stationary photoconductivity, the activation energy of the dark conductivity and the long-time range decay of the transient photoconductivity and photoinduced absorption is observed. The applicability of a-Si:H films for solar cells in view of these properties is discussed.
Thin Film Photovoltaic Options – an Overview
Authors: Stone Jack L. 
Published: March 2011

ABSTRACTSignificant deployment of the promising option of photovoltaics for energy will require cost-effective technologies that compete effectively with conventional sources. One such option utilizes thin films of a variety of photovoltaic materials. These thin films must be manufacturable in large quantities, and they must have high performance and acceptable reliability. Amorphous silicon (a-Si) was the first successfully demonstrated thin film to be widely adopted by industry. This material is already used to power a larger number of such consumer products as calculators, watches, and battery chargers. Recently, a-Si solar cells have been scaled up to large-area modules for power applications. Large fields of these modules have been deployed by utility companies for their evaluation. Polycrystalline thin films such as copper indium diselenide (CIS) and cadmium telluride (CdTe) have recently shown promise in following the path of a-Si. High-efficiency, large-area submodules have been successfully tested. By combining these materials in hybrid combinations, researchers have demonstrated much higher efficiencies. Even higher efficiencies have been demonstrated with more conventional materials such as silicon and gallium arsenide in thin-film form. Such devices have a high degree of acceptability because of their successful application for power uses in their non-thin-film form. Extensive examples are given to demonstrate the technical viability of these photovoltaic approaches for possible use in utility-scale power plants and in other near-term, highvalue markets.
Midgap Defects in a-SiGe:H Devices from Capacitance Measurements
Authors: Hegedus Steven S. , Zhou Theodore X. 
Published: March 2011

ABSTRACTWe have measured the capacitance of a-SiGe:H p-i-n solar cells as functions of temperature, frequency and bias. The density of states at the Fermi level g(EF) has been determined from two methods. We find that g(EF) increases from 1–2×1016 to 5–10×1017/(cm3eV) as the Ge content increases from 0 to 63%.
Microvoids and Photoconductivities in a-SiC:H and a-Si:H
Authors: Mahan A. H. , Williamson D. L. , Nelson B. P. 
Published: March 2011

ABSTRACTSmall microvoids having a radius of gyration between 3.3Å-4.6Å are found by the Small Angle X-Ray Scattering (SAXS) technique to exist in both glow discharge a-Si1−xCx:H (O<x<0.3) and a-Si:H (40°C<Ts<250°C) films. Included in these results are the first observation of microvoids, as detected by SAXS, in device quality a-Si:H. The volume fraction of microvoids (vf) is found to increase from 0.01 in device quality a-Si:H to greater than 0.20 for both the a-SiC:H(x=.30) and a-Si:H(Ts=40°C) films. Tilting experiments indicate that the microvoids are non-oriented (spherical) in a-SiC:H and are oriented (columnar) in non-device quality a-Si:H. The normalized coplanar photoconductivities of all samples decrease with increasing vf, but for a given vf the photoconductivity is larger in a-SiC:H than in a-Si:H. We discuss reasons for this behavior.
Electron Trapping Properties of Silicon Nitride Determined by Avalanche Injection
Authors: Park Y. C. , Jackson W. B. , Johnson N. M. , Hagstrom S. B. 
Published: March 2011

ABSTRACTThis paper presents the results of a comparison of the electron trapping in plasma-enhanced chemical vapor deposited nitrides (PECVD) to low pressure CVD (LPCVD) nitrides. The electron trapping was investigated using avalanche injection of electrons from the c-Si substrate over a thermal Si02 barrier into the various nitrides. The average trapping distance was 3–20nm in the various nitrides and the density of the traps was found to be around 2X1018 cm−3 for the PECVD nitrides while the density for LPCVD nitride was about 4X1018traps cm−3.
ESR in 13C Enriched a-Si1−xCx:H
Authors: Xu Xixiang , Kidoh Hideo , Morimoto Akiharu , Kumeda Minoru , Shimizu Tatsuo 
Published: March 2011

ABSTRACTThe effect of using the 13C isotope on the ESR signal in a-Si1−x Cx:H is investigated. The ESR linewidth increases with increasing the C content for a-Si1−x Cx.:H with 12C, while it is almost unchanged for a-Si1−x Cx:H with 12C. However, a doublet line which is expected for a C dangling bond having the hyperfine interaction with the 13C nucleus was not detected. In the range of a small x, it is possible that Si dangling bonds with 13C at the back bonds are the origin of the wide ESR signal. In the range of a large x, 13C dangling bonds should exist, but they are in a clustered form, being observed as an exchange narrowed single line instead of the hyperfine split line.
IR and Sims Study of Hydrogen Diffusion in RF Sputter Deposited Boron Doped a-Si:H and Undoped a-Ge:H
Authors: Mitra S. , Wu X.-L. , Shinar R. , Shinar J. 
Published: March 2011

ABSTRACTSecondary ion mass spectrometry (SIMS) and IR measurements of long range deuterium motion in rf sputter deposited (rf sp) p-doped a-Si:H and undoped a-Ge:H are compared to recently published results on undoped rf sp a-Si:H, which exhibited strongly power-law time dependent diffusion constants (exponent α= 0.75±0.1) in films of as-deposited content of di-H and tri-H bonds (usually associated with microvoids) Ndo –4–5 at.%. In pdoped a-Si:H samples where Ndo-l.8–3.8at.%, the diffusion is much faster, but the exponent is similar. In undoped a-Ge:H exhibiting a stretch vibration band indicative of mono-H bonding only, the diffusion is about one order of magnitude faster than in undoped a-Si:H, and α = 0.23. The results are discussed in relation to both the multiple trapping (dispersive) and defect mediated diffusion models.
The Application of Thick Hydrogenated Amorphous Silicon Layers to Charged Particle and X-Ray Detection
Authors: Perez-Mendez V. , Cho G. , Fujieda I. , Kaplan S. N. , Qureshi S. , Street R. A. 
Published: March 2011

ABSTRACTWe outline the characteristics of thick hydrogdenated amorphous silicon layers which are optimized for the detection of charged particles, x-rays and γ-rays. Signal amplitude as a function of the linear energy transfer of various particles are given. Noise sources generated by the detector material and by the thin film electronics - a-Si:H or polysilicon proposed for pixel position sensitive detectors readout are described, and their relative amplitudes are calculated. Temperature and neutron radiation effects on leakage currents and the corresponding noise changes are presented.
Electron Cyclotron Resonance Deposition of a-Si:H and a-C:H Films
Authors: Shing Y. H. , Yang C. L. , Allevato C. E. , Pool F. S. 
Published: March 2011

ABSTRACTAmorphous silicon (a-Si:H) and amorphous carbon (a-C:H) films have been deposited by electron cyclotron resonance (ECR) microwave plasma enhanced CVD. A high deposition rate of ˜ 25 Å/sec and a light-to-dark conductivity ratio of 1 × 105 for a- Si:H films have been achieved by the ECR process using a pure silane plasma. ECR microwave plasmas have been analyzed by in situ optical emission spectroscopy (OES) and have shown a strong H * emission at 434 nm indicating higher chemical reactivity than RF plasmas. The linear correlation between the film deposition rate and the SiH* emission intensity of ECR silane plasma suggests that SiH* species are related to the neutral radicals which are responsible for the a-Si:H film deposition. Hard and soft a-C:H films have been deposited by ECR with and without RF bias power, respectively. The RF bias to the substrate is found to play a critical role in determining the film structure and the carbon bonding configuration of ECR deposited a-C:H films. Raman spectra of these films indicate that ECR deposition conditions can be optimized to produce diamond films.
In-Situ Kelvin Probe Study of the SnO2 / p (a-Si:H) Interface. Effects of Hydrogen and Argon Plasma Treatment
Authors: Cabarrocas P. Roca i 
Published: March 2011

ABSTRACTWe present an in-situ Kelvin probe study of the effects of hydrogen and argon plasma treatments on fluorine doped tin-oxide (SnO2) substrates, as well as the consequences of these treatments on the subsequent growth of a-Si:H. We found that the effect of both hydrogen and argon plasmas is to enhance the reactivity of SnO2 substrates in a silane plasma. Moreover, the, doping level (Fermi level) of boron doped a-Si:H layers deposited on SnO2 is reached more quickly when the substrate has been treated previously with an argon plasma. As a consequence, we expect a higher open circuit voltage (Voc) for SnO2/p-i-n solar cells in which the substrate has been treated by an argon plasma. The Kelvin probe results have been confirmed by Voc measurements on solar cells deposited on treated and untreated substrates.
Experimental and Theoretical Analysis of Resonant Tunneling Through a-Si:H/a-Si1−xCx:H Double-Barrier in p-i-n Structure
Authors: Jiang Yeu-Long , Hwang Huey-Liang 
Published: March 2011

ABSTRACTa-Si:H/a-Si1−x Cx:H double-barrier structure imbedded in the i layer were fabricated by glow discharge. By using the built-in field in the i layer and the external applied bias, the effects of photo-excited carriers driven by electric field in the i layer tunneling through the double-barrier quantum well were examined. Distinct current bumps are distinctly observed when the quantum well structure is imbedded in the middle section of the i layer. A simple theoretical analysis was developed to study the quantum transport behavior.
Band Offsets and Anomalous Deep Defect Distribution at the Hydrogenated Amorphous Silicon-Crystalline Silicon Interface via Junction Capacitance Techniques
Authors: Essick J. M. , Cohen J. D. 
Published: March 2011

ABSTRACTA novel a-Si:H/c-Si Schottky diode heterostructure device premits the study of the capacitive response to relatively low temperatures (25 K) and also allows fast pulse filling capture measurements of electrons from the c-Si substrate into a-Si:H defect states. These latter measurements, as well as capacitance vs. temperature measurements on these diodes, indicate a nearly zero conduction band offset (50±50 meV). We also have observed trapping of holes at the a-Si:H/c-Si valence band discontinuity ΔEv. A clear threshold for the subsequent optical release of these trapped holes by sub-bandgap light yields a value of ΔEv = 0.58±0.02 eV. Finally, photocapacitance spectra along with thermally stimulated capacitance (TSCAP) measurements indicate an anomalously large (l×1018/cm3) Gaussian-shaped defect band located a Ec - 0.88 eV with a FWHM of 0.46 eV. Model calculations of the high temperature capacitance-voltage dependence indicate these defects lie predominately within 350 Å of the a-Si:H/c-Si interface.