bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion Mechanisms in Transition-Metal Oxides
Authors: Peterson N. L. 
Published: March 2011

ABSTRACTResults are presented for cation self-diffusioninCu2O and Cr2O3as a function of temperature and deviation from stoichiometry. A defect model for Cu2O involving neutral and singly charged copper vacancies, electron holes, and singly charged oxygen-interstitial ions is developed and fit to the tracer-diffusion data, the electrical-conductivity data, and the stoichiometry data, yielding concentrations and mobilities of these defects. The diffusion results for Cr2O3single crystals indicate that cation self-diffusion takes place by triply charged vacancies and that previous diffusion results for polycrystalline Cr2O3are dominated by grain-boundary diffusion.
Ion Implantation In Linbo3;
Authors: Wilson R. G. , Jamba D. M. , Betts D. A. 
Published: March 2011

ABSTRACTIon implantation is used to fabricate waveguides in LiNbO3;. We have implanted a variety of ions into LiNbO3; at energies from 100 to 300 keV and have been able to profile their depth distributions by secondary ion mass spectrometry. We report here their depth distributions and range parameters determined from Pearson IV fitting.
Time Dependence of Current Injection Phenomenon in Nickel-Doped MgO Crystals at High Temperatures
Authors: Tsang K. L. , Tohver H. T. , Chen Y. 
Published: March 2011

ABSTRACTThe electrical conduction mechanisms in MgO:Ni with Pt electrodes at 1473 K are studied over electric field ranges up to ∼10 kV/cm. The current transients induced by pulsed changes of the applied voltage as well as transient shortcircuit currents have been measured and analyzed to yield two electron hole recombination lifetimes of 10 and 250 s. The main features of the results are consistent with the double injection model of the electrical breakdown of MgO at high temperatures.
Physical Structure and the Electrochromic effect in Tungsten Oxide Films
Authors: Giri A. P. , Messier R. 
Published: March 2011

ABSTRACTIn all previous studies of tungsten oxide films it has been implicitly assumed that the film is uniform except for grain boundaries in polycrystalline films. In this study we show that amorphous tungsten oxide thin films contain highly anisotropic void networks which not only dominate their physical structure but also control their electrochromic behaviour. The void network structure is controlled primarily through ion bombardment of the growing film during deposition while the film stoichiometry HyWO3−x is controlled by the reactive sputtering processes of tungsten in Ar/O2/H2 atmospheres. The evolutionary growth model of physical structure was studied in detail by both transmission and scanning electron microscopy. On the basis of physical structure-property correlations we are able to consistently explain the basic electrochromic characteristics and chemical stability of the films. Such information leads to better understanding of the problems and limitations inherent in thin film electrochromic devices.
Sintering of AIN Powder Compacts
Authors: Akaishi M. , Horie Y. 
Published: March 2011

ABSTRACTPure-AINpowder compacts have been fabricated by isostatic pressing and impact forming in the pressurs range of 1.5 ˜ 5.5 GPa. The density of these compacts was in the range of 70 ˜ 90% of the theoretical. The mean particle size was reduced from 20 μm to a few micron meters depending on compaction pressures. The density changes observed aftersinteringat temperatures above 1,600°C were independent of initial starting densities. A similar shrinkage was observed when residual strains were eliminated by annealing at 1,550°C for 30 min. Micro-structures of the sintered specimens showed a mixed region of either extensive grain growth or little growth.
X-Ray Line Broadening Studies on Aluminum Nitride, Titanium Carbide and Titanium Diboride Modified by High Pressure Shock Loading
Authors: Morosin B. , Graham R. A. 
Published: March 2011

ABSTRACTPowders of AlN, TiC and TiB2 have been subjected to controlled shock loading with peak pressures in the samples between 14 to 27 GPa and preserved for post-shock study. Broadened x-ray diffraction peak profiles are analyzed by a simplified method and show increases in residual lattice strain and small decreases in crystallite size. Strain values range from 10−5 to 10−4 for TiB2 and to values larger than 10−3 for TiC and AlN.
The Design of Composite Materials For Electro-Mechanical and Electro-Thermal Applications.
Authors: Cross L. E. 
Published: March 2011

ABSTRACTIn composite materials for electro-mechanical applications, the importance of the mode in which the constituent phases are interconnected (connectivity) was stressed. For the tensor properties of mechanical, piezoelectric, and dielectric behavior, controlling the manner in which fields and fluxes thread through the composite can make orders of magnitude change in the coupled properties.Examples were drawn from piezoelectric ceramic:polymer composites for uniaxial and hydrostatic (hydrophone) pressure sensing where the 1:3 connected transversely reinforced composite can be shown to exhibit a figure of merit more than 103 that of the piezoceramic phase alone. In these systems, the importance of poisson ratio effects in the polymer phase were evident, and some new composite systems where the hydrostatic stiffness of the elastomer phases may be better exploited were considered.In electro-thermal applications such as in pyroelectric composites, the requirements of small-size and low-thermal mass put rigorous limits upon the scale of the composite microstructure. Techniques which achieve the appropriate scaling were described and preliminary data showed strong enhancement of the secondary effects in these composites were presented.
TEM Studies of Alloy Clustering in InAlAs Strained Layers
Authors: Peiro F. , Cornet A. , Morante J. R. , Clark S. A. , Williams R. H. 
Published: March 2011

ABSTRACTTransmission electron microscopy studies have been performed to characterise InxAl1−xAS layers grown by Molecular Beam Epitaxy on (100) InP substrates. The first observations of compositional nonuniformities in strained InAlAs layers are reported. The coarse quasiperiodic structure present in each sample has been found to be dependent upon the growth parameters and the sample characteristics such as strain, thickness and x value.
Atomie Layer Epitaxy ia a Rotating Disk Reactor
Authors: Liu H. , Zawadzki P. A. , Norris P. E. 
Published: March 2011

ABSTRACTCurrent difficulties of Atomic Layer Epitaxy (ALE) include relatively low growth rates and narrow process windows. Gas phase reaction, complex behavior of valve switching and purging times are suggested as the major causes [1,2]. We have used a movable X-shaped mechanical barrier to divide the growth chamber into four zones. Each zone supplies either source gas or purging hydrogen. If the barrier is positioned 0.5–2 mm from the wafer carrier, it can efficiently shear off the boundary layer and therefore reduce gas phase reactions. The substrate, constantly rotating beneath the barrier, is alternately exposed to group III or V sources by purging zones. The result is that process times are significantly reduced, saturated growth rate of 1 μm/hour is obtained and a relatively wide process window is observed. It was found that the growth mode was not purely ALE, due to source gas mixing which contributes an additional, possible kinetically limited, component of growth rate. However, this was also found to result in uniform film.
Quantum Well Shape Modification in Quaternary Quantum Wells
Authors: Köteles Emil S. , Masum Choudhury A. N. M. , Levy A. , Elman B. , Melman P. , Koza M. A. , Bhat R. 
Published: March 2011

ABSTRACTQuantum well interdiffusion has been employed, for the First time in the quaternary InGaAsP/InP system (grown lattice matched to InP substrates), in order to modify the as-grown, nominally square, shapes of single quantum wells so as to increase their bandgap energies. This was accomplished, in a spatially selective manner, by using low energy ion implantation through a mask to generate vacancies. Subsequent rapid thermal annealing drove these vacancies down to the quantum wells where their presence enhanced the thermally driven interdiffusion of atoms between the well and barrier layers. The goal of this work is to develop a simple process for the integration of optoelectronic devices with differing functions.
Dependence of the Defects Present in InAlAs/InP on the Substrate Temperature
Authors: Peiro F. , Cornet A. , Herms A. , Morante J. R. , Georgakilas A. , Halkias G. 
Published: March 2011

ABSTRACTThe crystalline quality of InAlAs layers, grown by Molecular Beam Epitaxy on (100) InP substrates, has been investigated by Transmission Electron Microscopy in order to study the influence of InAlAs growth temperature (Tg) on the density of structural defects present in the layers. Tg was varied from 300°C up to 530°C. The density of stacking faults and threading dislocations drops dramatically as Tg increas
Growth and Stability of Strained-Layer Multiple Quantum Wells
Authors: Niki Shigeru , Maktta Yunosuke , Yamada Akimasa , Shimada Junichi 
Published: March 2011

ABSTRACTThirty-period In0.28Ga0.72As(100Å)/GaAs (100Å) multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (lOO)-oriented GaAs substrate with a 0.5μm-thick InyGa1-yAs (0≤y≤0.28) buffer layer interposed between the QW layer and the GaAs substrate. The MQWs with y close to the average InAs mole fraction of the QW layer exhibited good crystalline quality. It indicates that the strain is well-balanced between the GaAs and In0.28Ga0.72As layer. A significant change in their photoluminescence spectra has been observed when annealed above 750δC by means of rapid thermal annealing, implying a structural disorder in the QW“region.
Chemical Beam Epitaxial Growth of GaAs Epilayer on GaAs (100) Substrate Using Unprecracked Arsine and Trimethylgallium
Authors: Park Seong-Ju , Sim Jae-Ki , Ro Jeong-Rae , Yoo Byueng-Su , Park Kyung-Ho , Lee El-Hang 
Published: March 2011

ABSTRACTWe present preliminary results aimed at investigating the effects of unprecracked arsine and trimethylgallium on the CBE (chemical beam epitaxy) growth of GaAs epilayers. We find that the growth rate rises linearly as the V/III ratio is increased when TMGa and arsine are used. All of the runs produced p-type material mainly due to carbon incorporation with the hole concentration typically of 1017 cm−3. The impurity content of the layers was found to depend distinctly on the pressure of TMGa. The significant drop in hole concentration is due in part to the hydrogen atoms generated from decomposed AsH3 which then aids in the removal of CH3 radicals on the surface. As a result of using unprecracked arsine for growth of the GaAs epilayers, we measure substantial improvements in their electrical and optical properties.
High Resolution Compound Semiconductor Mapping for Process Control
Authors: Denenberg David , Blew Austin 
Published: March 2011

ABSTRACTThis paper describes the use of advanced circuitry nondestructive eddy current techniques to map compound semiconductors. Surface profiles, contour maps and diameter scans are obtained from the process wafers tested providing the necessary information to control the processes for maximum yield.We will report on how the statistics and data analysis using sophisticated computer routines to study the radial uniformity of the compound semiconductors can be used for optimum output. Additionally, a review is presented of the basic principles of measurement and the applicable test methods and standards.Important aspects that enable feedback to deposition and implant equipment enabling uniformity improvements are discussed. Specification improvements resulting from recent circuit and software additions and the measurement results are discussed.
Advances in Photoreflectance Analysis of HBT Wafers
Authors: Denenberg David , Blew Austin 
Published: March 2011

ABSTRACTThis Poster describes the work done in a joint effort Research and Development Program with a leading University, with funding from the state, to develop a heterojunction bipolar transistor (HBT) epitaxial wafer screening tool. A computerized characteristics to HBT performance will be described.Photoreflectance data from about twenty HBT wafers that have been grown and have had test transistors fabricated from the wafers will be analyzed to determine the bandgap of the epitaxial materials and the electric fields.Comparison with previous works will be made in an attempt to reach a unified agreement in understanding that may lead to an ASTM test method.
Ordered Structure in GalnP/AIGalnP Quantum Wells and p-Doped Multiquantum Well AIGalnp Laser Diodes
Authors: Tanaka Toshiaki , Yanagisawa Hironori , Yano Shin-Ichiro , Minagawa Shigekazu 
Published: March 2011

ABSTRACTZinc doping is performed on the GalnP/AIGalnP multiquantum well (MQW) structure with the aim of dissolving the ordered atomic arrangement which results in higher quantum levels and therefore shorter lasing wavelengths. It is shown that the photoluminescence (PL) peak wavelength gradually shortens with doping and decreases by 20 nm when the hole concentration reaches 1×1018 cm−3, while the PL relative intensity becomes half that of an undoped MQW layer. Therefore, a moderate level of zinc doping of around 4∼5×1017 cm−3 is desirable to shorten the PL wavelength without decreasing the crystal quality. Transmission electron nano-diffraction patterns confirm that the ordered structure in the MQW layers disappears as the hole concentration increases. On the basis of this data, uniformly p-doped and modulation p-doped MQW laser diodes are fabricated and their characteristics are compared with the undoped MQW lasers. CW operation is achieved at wavelengths of 631 to 633 nm, which is 10 nm shorter than the 643 nm in an undoped MQW laser. Comparatively low threshold currents of 73 and 88 mA are attained for uniformly p-doped and modulation p-doped MQW lasers, respectively. However, they are about 20∼30 mA higher than those of the undoped MQW lasers. This results from the large overflow of electrons from the active layer, and the fact that the differential gain becomes smaller in the 630-nm band.
Studies of Recombination Transfer in Alloys and Thin Quantum Wells of Ga0.47In0.53As/InP Using the Optically Detected Impact Ionisation Technique
Authors: OMLING P. 
Published: March 2011

ABSTRACTThe possibilities of the optically detected impact ionisation (ODII) technique are demonstrated. It is shown how the ODII technique can be used to extract detailed spectroscopie information in thick InGaAs layers where resolved peaks from free excitons, bound excitons, and free-to-acceptor recombinations are obtained. In an investigation of single- and multiple-monolayer quantum wells of lattice-matched GalnAs in InP the experimental data show how the transfer of impact ionised electrons from the InP layers to the different InGaAs quantum wells, where they recombine as free excitons, can be studied. The recombination in a thicker quantum well (18 monolayer) shows a more complicated behaviour, and an explanation based on defect-related recombination, including bound-exciton and free-to-bound recombinations, is suggested.
Growth of GaAs and GaP from TMG: A Comparison
Authors: Eyers Markus , Sato Michio 
Published: March 2011

ABSTRACTIn the growth of GaAs and GaP from TMG strong differences are observed. Although the shape of the Arrhenius plot of the growth rate is similar, at low deposition temperatures the GaP growth rate is lower than that of GaAs. Additionally, more carbon is incorporated into GaP than into GaAs. Mass spectrometric studies on methyl desorption show that As has a stronger ability to aid the breaking of the final Ga-carbon bond than P.
Dry Etch Self-Aligned AlInAs/InGaAs Heterojunction Bipolar Transistors
Authors: Fullowan T. R. , Pearton S. J. , Kopf R. F. , Ren F. , Chen Y. K. , Smith P. R. , Chin M. A. , Lothian J. 
Published: March 2011

ABSTRACTA dry etch fabrication technology for high-speed AlInAs/InGaAs Heterojunction Bipolar Transistors (HBT's) utilizing low-damage Electron Cyclotron Resonance (ECR) CH4/H2/Ar plasma etching is detailed. The dry etch process uses triple self-alignment of the emitter and base metals and the base mesa, minimizing the base-collector capacitance (CBC). Devices with 2 × 4 μm2 emitters demonstrated current gains of 30–50 with ft and fmax values of ≥ 80 GHz and ≥100 GHz respectively. The structure employs a two-stage collector to achieve breakdown voltage (Vceo ) of 7V. The combination of processing and layer structure delivers truly scalable high yield AlInAs/InGaAs HBT's with both DC and RF characteristics suitable for large-scale, high speed digital circuit applications.
Selective Reactive ION Etching Effects on GaAs/AlGaAs Modfets
Authors: Ballegeer D. G. , Agarwala S. , Tong M. , Ketterson A. A. , Adesida I. , Griffin J. , Spencer M. 
Published: March 2011

ABSTRACTThe effects of selective reactive ion etching (SRIE) in SiCl4/SiF4 plasmas on GaAs/AlxGai-xAs heterostructures have been studied. Auger electron spectroscopy (AES) and Schottky diode measurements were performed to determine the effects of SRIE and post-SRlE processing on the surface conditions of AlGaAs layers. The degradation of the two-dimensional electron gas (2-DEG) properties of GaAs/Al0.3Ga0.7As heterostructures due to low-energy ion bombardment during SRIE were investigated by conducting Hall measurements at 300 and 77 K. Finally, measurements were performed on dry etched GaAs/Al0.3Ga0.7As modulation-doped field effect transistors (MODFETs) to determine the effects of SRIE on transconductance and threshold voltage. It is shown that extensive overetching during gate recessing results in an increase in device threshold voltages.
A Microstructual Analysis of Au/Pd/Ti Ohmic Contacts for GaAs-Based Heterojunction Bipolar Transistors (HJBTs)
Authors: Henry Bernard M. , Staton-Bevan A. E. , Sharma V. K. M. , Crouch M. A. , Gill S. S. 
Published: March 2011

ABSTRACTAu/Pd/Ti and Au/Ti/Pd ohmic structures to thin p+-GaAs layers have been investigated for use as contacts to the base region of HJBTs. The Au/Pd/Ti contact system yielded specific contact resistivities at or above 2.8 × 10−5Ω:cm2. Heat treatments up to 8 minutes at 380°C caused only limited interaction between the metallization and the semiconductor. The metal penetrated to a maximum depth of ≃2nm. Specific contact resistivity values less than 10−5Ωcm2 were achieved using the Au/Ti/Pd (400/75/75nm) scheme. The nonalloyed Au/Ti/Pd contact showed the best combination of electrical and structural properties with a contact resistivity value of 9 × 10≃6Ωcm2 and Pd penetration of the GaAs epilayer to a depth of cs30nm.
The Microstructure of ZrN/GaAs Schottky Contacts and its Correlation with Electrical Properties.
Authors: Phatak Prashant , Imaizumi Mitsuru , Weber E. R. , Newman N. , Liliental-Weber Z. 
Published: March 2011

ABSTRACTThe self-aligned GaAs metal-semiconductor field-effect transistor technology requires that the gate material maintains a good rectifying contact with the GaAs substrate when subjected to high-temperature annealing around 800–900° C. ZrN Schottky contacts to GaAs were previously shown to have excellent electrical properties at high tempratures. An increase of barrier height and a decrease in the reverse breakdown voltage with rapid thermal annealing at temperatures up to 900° C has been observed. The ideality factor increases after rapid thermal annealing at 900° C.In an attempt to explain the above observations, we investigated the interface structure of such contacts under as-deposited and annealed conditions. By high resolution TEM it was found that the interface of as-deposited samples is fairly flat but protrusions form after rapid thermal annealing treatment at 850 and 900° C. The selected area diffraction analysis shows the presence of ZrO2 near the interface.It is therefore likely that protrusions are the cause of the degradation of electrical properties of the contacts. These protrusions may be caused by the presence of a residual oxide layer before deposition. Indeed, a deposition of ZrN after sputter cleaning the substrates before deposition procedure resulted in an abrupt interface even after annealing at 900° C.
Electrical and Optical Characterization of Pseudomorphic AlGaAs/InGaAs High Electron Mobility Transistors
Authors: Winters W. E. , Yue A. S. , Streit D. 
Published: March 2011

ABSTRACTAdvances in thin-film growth techniques have allowed the succesful fabrication of transistor devices, relying on heterostructure technology to enhance their electrical performance. Devices utilizing heterostructure epitaxy have demonstrated unity current-gain cut-off frequencies well in excess of 100 GHz and maximum oscillation frequencies beyond 200 GHz.In this paper, the AlGaAs/InGaAs pseudomorphic HEMT is studied. X-ray Double-Crystal Diffractometry and Low-Temperature Photoluminescence Spectroscopy are used to demonstrate that the InGaAs pseudomorphic layer thickness of the strained layers, did not degrade the device switching speed. This suggests that HEMT devices with higher indium contents may be permitted without having to reduce the InGaAs layer thickness due to strain accommodation requirements. Since the increase in In content lowers the electron and hole effective masses and raises the low-field mobility, higher cut-off frequencies should be possible.
DC Characteristics of Nanometer-Gatelength GaAS Mesfets
Authors: Nummila K. , Tong M. , Ketterson A. A. , Adesida I. 
Published: March 2011

ABSTRACTHigh-resolution electron-beam lithography has been used to fabricate GaAs MESFETs with gate-lengths ranging from 1 μm down to 30 nm. Devices were fabricated on two MESFET epitaxial layers; one with undoped GaAs-buffer layer while the other had a p- -GaAs-buffer layer. The DC characteristics including transconductance, output conductance, threshold voltage, and subthreshold current of these devices have been measured. Devices on both epitaxial layers exhibited significant short-channel effects. A negative threshold voltage shift and an increase in the subthreshold current were observed. These effects become prominent as the device aspect ratio (gate length/channel thickness) falls below 5. It is shown however that the effects were considerably suppressed in the layer with p- -GaAs buffer due to better confinement of electrons in the channel.
Reduced Mobility and PPC in In.20Ga.80As/Al.23Ga.77 as Hemt Structure
Authors: Schacham S. E. , Mena R. A. , Haugland E. J. , Alterovitz S. A. 
Published: March 2011

ABSTRACTTransport properties of a pseudomorphic In .20Ga.80As/Al.23Ga.77As HEMT structure have been measured by Hall and SdH techniques. Two samples of identical structures but different doping levels were compared. Low temperature mobility measurements as a function of concentration shows a sharp peak at a Hall concentration of 1.9.1012/cm2. This concentration coincides with the onset of second subband occupancy, indicating that the decrease in mobility is due to intersubband scattering. In spite of the low Al content (23%) large PPC was observed in the highly doped sample only, showing a direct correlation between the PPC and doping concentration of the barrier layer.
Electronic Properties of Ultrathin Isoelectronic Intralayers in Semiconductors
Authors: Mäder K. A. , Baldereschi A. 
Published: March 2011

ABSTRACTAn empirical tight-binding Koster-Slater approach is used to determine the electronic properties of ultrathin“quantum wells”in semiconducting host materials of the zincblende or diamond structure. The“quantum well”is viewed as a giant two-dimensional isoelectronic impurity, and treated in a perturbational Green's function approach. We present results on the AlAs/GaAs and on the InP/InAs systems.