bluuebunny/crossref_metadata_2025_split huggingface dataset:
OMVPE Growth of Epitaxial InSb Thin Films Using a Novel Group V Source Compound
Authors: Stauf Gregory T. , Gaskill D.K. , Bottka N. , Gedridge R.W. 
Published: March 2011

ABSTRACTTo date, OMVPE has failed to grow epitaxial InSb at temperatures below about 400 °C. Therefore, we have studied InSb deposition using the novel group V source triisopropylantimony (TIPSb) with trimethylindium (TMIn), comparing this with results in the same reactor using trimethylantimony (TMSb). We have grown InSb on both GaAs and on high-resistivity p-type InSb substrates, exploring the effects of temperature, substrate, V/ill ratio, and thickness on film properties. Our best results with TMSb and TMIn were obtained using a V/ill ratio of 8 and growth temperature of 450 °C. The unintentionally doped films exhibited good crystallinity and were n-type about lx1015 cm-3 down to 5 K, with 77 K mobilities of 90,000 and 253,00°Cm2/V-sec for InSb on GaAs and on InSb, respectively. These results are comparable to the best published MBE data. While InSb films could not be grown well at temperatures below 425 °C using TMSb, specular epilayers were obtained with TIPSb at temperatures as low as 300 °C, though with a low deposition rate. Our best conditions with TIPSb were with a Vill ratio of about 12 and a substrate temperature of 350 °C. The results of variable temperature and variable magnetic field Hall, double crystal x-ray diffractometry, Nomarski microscopy, Auger electron spectroscopy and scanning electron microscopy will be presented.
Electron Mobility In N-Type Epitaxial ZnSe
Authors: Vaziri M. , Reifenberger R. 
Published: March 2011

ABSTRACTAn analysis of the temperature dependent mobility in lightly doped ZnSe epitaxial layers grown on a semi-insulating GaAs substrate by Molecular Beam Epitaxy is reported. Our results indicate that the temperature dependence of the mobility is in poor agreement with calculated values based on typical phonon and ionized impurity scattering mechanisms. Good agreement between theory and experimental data call be obtained by including a scattering term associated with the space-charge region surrounding defects.
Orientation Dependence of the Stability of Strained Sn Eplayers Grown On Cd0.8Zn0.2Te Substrates
Authors: Niles David W. , HÖChst Hartmut 
Published: March 2011

ABSTRACTThe strain energy density in epitaxial overlayers depends strongly on the substrate's surface orientation. The affect of a growth orientation dependent strain energy contribution to the phase stability was studied by growing overlayers of metastable, semiconducting a-Sn films on the (100) and (111) surfaces of Cd0.8Zn0.2Te substrates. On the (100) surface the α-phase of Sn remains stable for coverages up to and beyond 125 ML. On the (111) surface though, the Sn overlayer shows metallic behavior from a partial α→β phase separation for coverages lower than 100 ML. Static calculations using the stress-strain relationship bear out these experimental results by showing that the strain energy density for the (111) growth direction is 38% larger than for the (100) direction.
Implant Isolation of Device Structures Containing Buried, Highly-Doped Layers
Authors: Pearton S. J. , Ren F. , D'Asaro L. A. , Hobson W. S. , Fullowan T. R. , Lothian J. , Abernathy C. R. , Kopf R. F. , Kuo J.-M. 
Published: March 2011

ABSTRACTThe formation of high resistivity (> 107 Ω□) regions in GaAs-AlGaAs HBT and SEED structures by oxygen and hydrogen ion implantation is described. Multiple energy implants in the dose range 1013 cm−3 (for O+) and 1015 cm−2 (for H+), followed by annealing around 500°C are necessary to isolate structures ∼2 μm thick. In each case, the evolution of the sheet resistance of the implanted material with annealing is consistent with a reduction in hopping probabilities of trapped carriers between deep level states for temperatures up to ∼600°C, followed by significant annealing of these deep levels. A comparison of the relative thermal stability of O+ or H+ ion implantisolated p+ material is given. Small geometry (2 × 9 μm2) HBTs exhibiting current gain of 44 and cut-off frequency fT as high as 45 GHz are demonstrated using implant isolation.
Phase Relations and Bulk Crystal Growth in the System CuInTe2-MnIn2Te4
Authors: Kelliher James T. , Bachmann Klaus J. 
Published: March 2011

ABSTRACTRecently manganese substituted I-III-VI2 compounds have been investigated. Their magnetic properties are similar to the paramagnetic transistion metal ion substituted II-VI materials, but their crystal structure is non-cubic resulting in anisotropies in their physico-chemical properties that do not exist in the zincblende structure diluted magnetic semiconductors (DMS) materials. In this paper, we report the phase relations on the pseudobinary cut CuInTe2-MnIn2Te4 based on x-ray diffraction and differential thermal analysis data. The range of chalcopyrite structure alloys of composition Cu1−xMnx□xIn2Te4 is limited to x<0.52 due to an eutectic at x=0.74, T= 734°C. A second eutectic exists at x = 0.97, T = 737.5°C. A heretofore unknown congruently melting compound exists in between the two eutectics at x= 0.85, Tm = 760°C. Also, the thus far unknown melting point of the compound MnIn2Te4 was determined (740°C ). Based on the analyses of the first to freeze parts of directionally solidified melts in this range of liquidus compositions by inductively coupled plasma emission spectroscopy the solidus is constructed.
Intrinsic Carrier Concentrations in Long Wavelength HgCdTe Based on the New, Nonlinear Temperature Dependence of Eg(x,T)
Authors: Seiler D. G. , Lowney J. R. , Littler C. L. , Yoon I. T. 
Published: March 2011

ABSTRACTIntrinsic carrier concentrations of narrow-gap Hg1-xCdxTe alloys (0.17≦ x ≦0.30) have been calculated as a function of temperature between 0 and 300 K by using the new nonlinear temperature dependence of the energy gap obtained previously by twophoton magneto-absorption measurements for samples with 0.24≦ x ≦0.26. We report here experimental values for Eg(x,T) for samples with x = 0.20 and 0.23 obtained by one-photon magneto-absorption measurements. These data confirm the validity of the new Eg(x,T) relationship for these : values. In this range of composition and temperature, the energy gap of mercury cadmium telluride is small, and very accurate values are needed for the gap to obtain reliable values for the intrinsic carrier density. Large percentage differences exist between our new calculations and previous values for ni at low temperatures. Even at 77 K, differences approaching 10 percent exist, confirming the importance of using the new ni results for materials and device characterization and a proper understanding of device operation in long-wavelength materials.
Process Control For Composites Using Computed Tomography
Authors: Engler Philip , Friedman William D. , Santana Mark W. , Chi Frank 
Published: March 2011

ABSTRACTStructural information provided by computed tomography (CT) can be used for quality control and optimization of processes for manufacturing better materials. The squeeze casting method for producing metal matrix composites involves infiltrating a preform of ceramic fibers with molten metal under high pressure. Part quality can be improved if CT is used before infiltration to determine if the preforms have the desired distribution of fibers and are free of defects. Measurements do not require uniform shapes, and CT systems can even be used to obtain accurate densities on complicated part shapes that are not amenable to bulk density measurements based on weight and size. With this quantitative distribution information as a guide, preform production can be modified to produce either a more uniform fiber distribution or to selectively increase the fiber concentration in critical areas. Problems occurring during later stages of processing can be detected in CT images of the completed part. For example. CT can be used to detect unreinforced regions in metal matrix composites caused by cracking of the preform during the squeeze casting process. CT scans of completed parts can also detect and distinguish variations in structure such as microporosity.
Impact of X-Ray Tomographic Microscopy on Deformation Studies of a SiC/Al MMC
Authors: Breunig T.M. , Stock S.R. , Kinney J.H. , Guvenilir A. , Nichols M.C. 
Published: March 2011

ABSTRACTDamage in a continuous, aligned-fiber SiC/Al metal matrix composite (MMC), e.g. fiber fracture, fiber-matrix interphase microcracking, intra-ply matrix voids and cracks, is examined with synchrotron x-ray tomographic microscopy (XTM). Quantitative three-dimensional measurements of damage are reported in as-fabricated and monotonically loaded SiC/Al. The XTM results indicate that increases in observed macroscopic structural stiffness during the first few fatigue cycles of an MMC coupon correspond to elimination of processing-related matrix porosity and to displacement of the fibers from a somewhat irregular arrangement into a more nearly hexagonal array. The XTM data also show that the carbon cores of the SiC fibers begin to fail at or below 828 MPa, that is, at loads far less than those for fracture of the entire fiber. The implications of these results and of the use of in situ loading for fatigue damage quantification are also discussed for mechanical/thermal modelling.
Response Time of a-Si:H Photosensors in Optically Addressed Spatial Light Modulators
Authors: Moddel Garret , Barbier Pierre R. 
Published: March 2011

ABSTRACTA successful application for a-Si:H is as the photosensor in a liquid crystal optically addressed spatial light modulator (OASLM). We analyze the response time of an a-Si:H p-i-n photodiode in a “pseudo-OALSM,” in which the liquid crystal is replaced by an equivalent capacitor, under both forward and reverse bias. Under reverse bias the two important effects are the photocurrent response time, and residual trapped charge. Under forward bias the mechanism shifts from double injection regimes to ohmic transport as a function of voltage. We relate these characteristics to the operation of an OASLM.
Comprehensive Kinetic of Defects in a-SI:H
Authors: Redfield David , Bube Richard H. 
Published: March 2011

ABSTRACTLThe introduction of several new principles into the analysis of transition kinetics of metastable defects in a-Si:H has produced substantially improved rate equation for the density of defects as functions of time, light intensity, and temperature. The solution of this equation is stretched exponential (SE) having properties that explain in unifying way many observations of defect properties, including generation and anneal of the defect density in homogeneous films and degradation and anneal of solar cells. Major consequences are found for both the steady-state and transient properties of the defect density and for interpretations of microscopic models of the defects. These properties are also shown to be analogous to those of metastable centers in other materials, particularly the metastable DX center in AlGaAs which offers rare insight into the microscopic origins of stretched exponentials that can be applied to a-Si:H in ways that provide new perspectives on effects of alloying and hydrogen on stability.
Correlation Between Amorphous Silicon Solar Cell Parameters and Pbotoinduced Current Noise Power Spectrum
Authors: Demichelis F. , Rava P. , Tagliaferro A. 
Published: March 2011

ABSTRACTA new technique based on measurements of photoinduced current noise in amorphous silicon solar cells is reported. A 1/fn (n-1) component, superimposed to a frequency independent one due to simple shot noise, is attributed to the presence of defects limiting the conversion efficiency of the cell. In particular large defects can easily be detected since they are characterized by a very large increase of the l/fn component. In general a correlation is found between the intensity of the l/fn component and short circuit current density, fill factor and cell conversion efficiency.
The Structure of Hydrogenated Amorphous Silicon-Carbon Alloys as Investigated by Exafs
Authors: Pascarelli S. , Boscherini F. , Mobilio S. , Evangelisti F. 
Published: March 2011

ABSTRACTWe have studied the local structure of hydrogenated amorphous silicon-carbon alloy films, a-Si1−xCx:H, by measuring the extended x-ray absorption fine-structure (EXAFS) at the Si K edge.We find that first coordination shell average bond lengths are 2.35 Å for Si-Si and 1.86 Å for Si-C and are constant with concentration to within × 0.015 Å.By comparing the composition of the first coordination shell around Si with the average concentration we show that the alloy tends to be chemically ordered, in that heteroatomic bonds are preferred.
Control of Photo-Induced Degradation in a-Si:H Prepared from Xe-Diluted Silane
Authors: Mashima Satoshi , Hasezaki Kazuhiro , Suzuki Atsushi , McElheny Peter J. , Matsuda Akihisa 
Published: March 2011

ABSTRACTFilms were prepared by the Xe-dilution method in an attempt to mimic the microstructure found in low-photodegradation deuterated films which show a greater number of clustered deuterium and microvoids when compared to conventional hydrogenated films. Common features were found for the light soaking behaviors in the film properties characterized by the electron spin resonance, gas thermal evolution, Raman spectroscopy, and infrared spectroscopy among deuterated, conventional hydrogenated, and Xe-diluted films.
The Effect of Light Soaking on Electron Mobilities in Hydrogenated Amorphous Silicon
Authors: Antoniadis Homer , Wang Qi , Schiff E. A. , Guha S. 
Published: March 2011

AbstractElectron drift mobilities μe were measured in undoped hydrogenated amorphous silicon specimens for different light soaking states. Standard transient photocurrent and time-of-flight techniques were employed; the light soaking state was monitored using the electron deep-trapping mobility-lifetime product μτe,t. Two different measurement series are reported. The first series measured a specimen from the reactor at Syracuse at room-temperature. No significant effects of light soaking on μe were found. The second series measured a solar-optimized specimen from Energy Conversion Devices, Inc. below 200°K. In these measurements we found a decrease in μe of about a factor 3.
Barrier Limited Transport Mechanisms in Doped μc-Si and μc-Si,C
Authors: Lucovsky G. , Wang C. 
Published: March 2011

ABSTRACTAn analysis of the room-temperature dark conductivities and activation energies for doped μc-Si and μc-Si,C is used to develop a band alignment model which shows that the maximum attainable dark conductivities in these materials are determined by transport through, or over interfacial potential barriers between Si crystallites, c-Si, and the intervening amorphous regions: a-Si:H or a-Si,C:H, respectively. For all levels of doping in μc-Si,C, the transport is limited by thermionic emission over interfacial barriers at the c-Si/a-Si,C:H interface, placing a significant constraint on applications requiring both high optical transparency and high conductivity.
Influence of Doping on the Structural Properties of Micro-Crystalline Silicon Prepared with the VHF-GD Technique at Low Deposition Temperatures.
Authors: Fingera F. , Prasad K. , Dubail S. , Shah A. , Tang X.-M. , Weber J. , Beyer W. 
Published: March 2011

ABSTRACTIn doped and undoped microcrystalline silicon prepared with Very High Frequency Glow Discharge, hydrogen is found to be mainly located at the grain boundaries from where it desorbs easily at low annealing temperatures. In undoped material hydrogen evolution peaks are between 400°C and 500°C. Upon doping, a new major peak appears at 300°C and a strong reduction of the typical Si-H infrared absorption bands are found for doped samples when annealed up to 300°C. This is accompanied by an increase of the conductivity due to either de-passivation of dopants in the crystallites or a favourable reconstruction at the grain boundaries. Hydrogen profiles show a hydrogen depletion at the film/air interface that is more profound in doped material, thus correlating with the appearance of the low temperature evolution peak. The high free carrier density in the crystallites of the doped material gives rise to strong optical absorption. Although correlating nicely with conductivity, the free carrier absorption cannot be evaluated simply in terms of die Drude theory. In view of the high conductivities and the dominance of Si-H surface bonds we argue that our material does not contain a large amount of amorphous tissue.
Device Application and Growth Mechanism for Hemispherical-Grained Si.
Authors: Watanabe Hirohito , Aoto Nahomi , Adachi Saburo , Kikkawa Takamaro 
Published: March 2011

ABSTRACTA polycrystalline-silicon surface with hemispherical-grain (HSG) is deposited by low-pressure chemical vapor deposition at the transition temperature of the film structure from amorphous to polycrystalline. The surface area of the HSG-Si film is about twice as large as Si films deposited at other temperatures. It is found that the HSG-Si is not formed during deposition, but formed during annealing of amorphous Si surface after deposition. At the annealing temperature which is maintained to be the transition temperature, HSG-Si is formed by the nuclei generation on the amorphous-Si surface and the outward crystalline growth of grains dixough migration of surface Si atoms. By applying the HSG-Si film as the storage electrode for a 64Mbit dynamic random access memory (DRAM) stacked-capacitor with a SiO2Si3N4 dielectric film, twice the capacitance is obtained. The increase in the capacitance makes it possible to reduce the DRAM cell area, even by using a relatively thick dielectric film for higher reliability. Consequently, the HSG-Si technique is applicable to the fabrication process for 64Mbit and larger DRAMs.
Physical Properties of Undoped and Doped Microcrystalline SiC:H Deposited by PECVD
Authors: Demichelis F. , Pirri C. F. , Tresso E. , Dellamea G. , Rigato V. , Rava P. 
Published: March 2011

ABSTRACTExperimental results on a systematic investigation on the elemental composition, structural, optical and electrical properties of undoped and doped microcrystalline silicon carbide films deposited by Plasma Enhanced Chemical Vapor Deposition.The doped samples show high values of dark conductivity accompanied by good optical properties so to satisfy the requirements for heterojunction window material.
Dice (Dynamic Inner Collection Efficiency) Characterization of Photovoltaic Performance in A-Sl Solar Cells
Authors: Ohnishi M. , Takahama T. , Kuwano Y. 
Published: March 2011

ABSTRACTA new analytical method for amorphous silicon solar cells, called DICE (dynamic inner collection efficiency), has been developed. The depth profile of the photovoltaic characteristics of solar cells under any operating condition are obtained by this method in a non-destructive way for the first time. It was experimentally confirmed by the DICE characterization that 1ight-induced deterioration does not occur homogeneously in the thickness direction of the I-layer, and that the main deterioration region in the I-layer changes according to the duration and load condition of light exposure.The DICE method also contributed to an improvement in the conversion efficiency of two kinds of a-Si solar cells, an integrated-type submodule and a new type of ultralight flexible module. A total area efficiency of 10.6% was obtained with a size of 10 cm × 10 cm integrated-type a-Si solar cell submodule on a glass substrate, and the world's highest powet—to-weight ratio of 275 mW/g was achieved in the flexible module on a plastic film.
Effect of Light Exposure Conditions on the Light-Induced Degradation in Amorphous Silicon Alloy Solar Cells
Authors: Nakata Y. , Yokota A. , Sannomiya H. , Moriuchi S. , Inoue Y. , Nomoto K. , Itoh M. , Tsuji T. 
Published: March 2011

ABSTRACTLight-induced changes in current-voltage characteristics of amorphous single-junction solar cells made of silicon alloys, a-SiC, a-Si, and a-SiGe have been studied systematically. The effect of the light intensity and the bias voltage on the light-induced degradation in the conversion efficiency and other photovoltaic parameters has been clarified quantitatively, and it has been shown that the light-induced degradation characteristics of the photovoltaic parameters can be described by a single function of some normalized parameters of exposure condition. Theoretical background for the experimental results is also examined and discussed by applying a defect creation model modified to an active layer of the a-Si alloy solar cells. Utilizing these analytical formula, we propose an accelerated test method by solar simulator indoor measurement instead of natural sunlight outdoor testing.
High Efficiency Stable a-Si Three Junction 12″ × 13″ Modules
Authors: Bennett Murray S. , Catalano A. , Newton J. , Poplawski C. , Arya R. , Rajan K. , Wood G. , Wiedeman S. 
Published: March 2011

ABSTRACTThree junction a-Si based photovoltaic modules have been made using a design which provides high initial efficiency and good resistance to photodegradation. The cells have a Si/Si/SiGe configuration in which the i-layer in the middle junction is 4000Å thick. The most efficient module measured to date has an aperture area efficiency of 9.82%. This design will limit light-induced efficiency losses to 15% or less, based on small area results, however defect related problems have increased this value to 17 – 23%. Preliminary data on the effect of shunts on stability is presented. We discuss various concerns related to large area deposition and scale-up.
Sub-Bandgap Optical Absorption in Amorphous Silicon using Photo-Pyroelectric Spectroscopy
Authors: Fan J. , Kakalios J. 
Published: March 2011

ABSTRACTMeasurements of the optical absorption spectrum of doped and undoped hydrogenated amorphous silicon (a-Si:H) for photon energies ranging from 0.8 to 2.5 eV are obtained using photo-pyroelectric spectroscopy (PPES). This technique, based upon the pyroelectric effect, has a simpler experimental set-up than photo-thermal deflection spectroscopy, and presently has a sensitivity of ad > 10-3, where d is the sample thickness. In addition, using PPES we have measured the non-radiative quantum efficiency in a-Si:H, and find that it has a strong wavelength dependence for sub-bandgap illumination.
A Spatially Resolved Study of Chemical Vapor Deposition of a-Si:H with Pure Thermal Excitation of Disilane
Authors: Amato G. , Spagnolo R. , Fizzotti F. , Manfredotti C. , Menna P. , Nobile G. 
Published: March 2011

ABSTRACTOptical, electronic and structural properties of a-Si:H samples grown by Low Pressure Chemical Vapor Deposition have been investigated by means of IR spectroscopy, Raman scattering and Photothermal Deflection Spectros-copy.Samples grown at different positions along the tube show very different properties that can be related to the amount of H and to the nature of the Si-H bonds.The most important parameters governing the thermally excited growth of a-Si:H are presented and discussed.
Amorphous Hydrogenated Silicon Carbide Prepared from DC-Biased RF-Plasma-Enhanced Chemical Vapor Deposition
Authors: Lu Hsueh Yi , Petrich Mark A. 
Published: March 2011

ABSTRACTWe present evidence that an independently applied dc bias voltage has a significant effect on the plasma deposition of amorphous hydrogenated silicon carbide. Deposition rates increase with either positive or negative dc voltages applied to the powered rf electrode. The microstructure of the films (as determined by infrared absorption) can be reduced by increasing the plasma potential (positive dc bias voltages). Negative dc biases, or excessively high positive biases, result in increased amounts of film microstructure. Film carbon content is increased when positive biases are applied, but the optical band gaps decrease suggesting increased amounts of graphitic bonding configurations. Negative biases do not change the carbon content of the films, but do increase both deposition rate and microstructure.