bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear-induced phase transformation in yttria stabilized zirconia: X-ray photoelectron spectroscopic studies
Authors: Chatterjee Dilip , Majumdar Debasis , Ghosh Syamal , Blanton Thomas
Published: July 2002

X-ray photoelectron spectroscopy has been used to study near-surface phase transformation in yttria stabilized zirconia subjected to sliding wear. Characteristic differences are observed in the valence bands of the tetragonal and the monoclinic phases of zirconia. These valence bands have been used as ‘‘fingerprints’’ to monitor phase transformation during wear under different loading conditions. Conventional and glancing angle x-ray diffraction techniques were found inadequate to detect this phase transformation.
Parametric amplification using superconductor-insulator-superconductor junctions: A study carried out on an electronic simulator
Authors: Zhou J. H. , Xu H. F. , Yang S. Z. , Wu P. H.
Published: July 2002

An ideal superconductor-insulator-superconductor (SIS) junction biased below the gap voltage is a purely reactive device based on which reflection parametric amplifier can be built. Using an electronic simulator to model the junction, we have observed gain as high as 10 dB and have shown that the quantum reactance of the simulator are on the same orders of magnitudes as those of a SIS junction, thus demonstrating, for the first time, the feasibility of this new type of parametric amplifier.
Photoluminescence-dark-spot-free AlGaAs grown on Si substrate
Authors: Wada Naoki , Iwabu Koichi , Sakai Shiro , Fukui Masuo
Published: July 2002

GaAs and AlGaAs are grown on an UCGAS (undercut GaAs on Si) in which a part of the GaAs layer grown on Si substrate is separated from the substrate by the post-growth processing. The grown layers are characterized by the high-magnification (×1600) photoluminescence image which is capable of visualizing the very small (less than 1 μm) dark spots in the AlGaAs layer. No dark spot is found in the layer grown on the UCGAS. A planar AlGaAs on Si, on the other hand, has the dark-spot density (DSD) of more than 108 cm−2. The DSDs of the layers grown on planar GaAs on Si and on the mesa are more than 108 cm−2 and in the order of 107 cm−2, respectively. The dark-spot-free region exactly corresponds to the UCGAS part, showing that the UCGAS is quite effective to eliminate the defects in AlGaAs on Si. The two factors, the reduced stress and the absence of the GaAs/Si interface in the UCGAS, are thought to be responsible for this improvement.
High-brightness diode-laser-pumped semiconductor heterostructure lasers
Authors: Le H. Q. , Goodhue W. D. , Di Cecca S.
Published: July 2002

A novel, generic design for diode-pumped lasers and amplifiers utilizing semiconductor heterostructures has been implemented in the InGaAs/GaAs/AlGaAs material system. The spatial and spectral characteristics of these heterostructures are optimized to provide low output beam divergence, low aspect ratio, high efficiency, and low threshold. A pump-power-limited cw output of 0.58 W was obtained with diode-array pumping, and a peak power of 33 W per facet was achieved with pulsed Ti:Al2 O3 laser pumping. A near-diffraction-limited output beam with a divergence of 14° by 3.4° has been obtained.
Operation of the sapphire Cerenkov laser
Authors: Fisch E. E. , Walsh J. E.
Published: July 2002

First operation of a sapphire-based Cerenkov free electron laser is reported. It is a tunable source of coherent millimeter and submillimeter radiation. The phase velocity of light in sapphire is about one-tenth of that in free space so that Cerenkov radiation is obtained at modest electron beam energies. In addition to its role as a Cerenkov coupler, the sapphire forms a high Q resonator obviating external mirrors. The spontaneous Cerenkov emission is well-confined by this resonator and can build to watts of power. Measured tuning and threshold currents are presented and compared with the predictions of free electron laser theory.
Performance prediction of high T
c superconducting small antennas using a two-fluid-moment method model
Authors: Cook G. G. , Khamas S. K. , Kingsley S. P. , Woods R. C.
Published: July 2002

The radar cross section and Q factors of electrically small dipole and loop antennas made with a YBCO high Tc superconductor are predicted using a two-fluid-moment method model, in order to determine the effects of finite conductivity on the performances of such antennas. The results compare the useful operating bandwidths of YBCO antennas exhibiting varying degrees of impurity with their copper counterparts at 77 K, showing a linear relationship between bandwidth and impurity level.
X-ray photoelectron spectroscopy analysis of photostimulated chemical vapor deposition hydrogenated amorphous silicon/amorphous aluminum oxide
Authors: Uwasawa K. , Ishihara F. , Matsumoto S.
Published: July 2002

We have fabricated multilayer structures consisting of hydrogenated amorphous silicon (a-Si:H) and amorphous aluminum oxide (a-AlxO1−x) by photostimulated chemical vapor deposition (photo-CVD) using ArF excimer laser. X-ray photoelectron spectroscopy (XPS) analysis of the multilayer samples demonstrated that the a-Si:H/a-AlxO1−x heterostructure grown by the photo-CVD had an ideally sharp interface and no mixing layer. The XPS valence-band spectrum for a-AlxO1−x deposited on a-Si:H also determined the valence-band offset at about 4 eV in the a-Si:H/a-AlxO1−x superlattices.
Application of scanning electron acoustic microscopy to the characterization of n-type and semi-insulating GaAs
Authors: Meńdez B. , Piqueras J.
Published: July 2002

A series of GaAs wafers with different doping levels and electrical resistivity has been used to investigate the scanning electron acoustic microscopy (SEAM) application to the characterization of this material. It has been found that SEAM is particularly useful to characterize semi-insulating GaAs as compared with n-type material. The SEAM signal generation mechanisms in GaAs are discussed.
Visible light emission at room temperature from anodized plasma-deposited silicon thin films
Authors: Bustarret E. , Ligeon M. , Bruyère J. C. , Muller F. , Hérino R. , Gaspard F. , Ortega L. , Stutzmann M.
Published: July 2002

In situ boron-doped hydrogenated silicon films plasma-deposited on various conductive substrates (including transparent oxides on glass) have been anodized in hydrofluoric acid solutions and subsequently electrochemically oxidized in an aqueous electrolyte. At room temperature, the resulting layers yield visible photoluminescence and electroluminescence intensities and spectral shapes similar to those of p-type crystalline porous silicon obtained in the same way. The results demonstrate the technological feasibility of light-emitting devices by applying electrochemical processes to deposited silicon-based films.
InGaAsP/InP horizontal cavity surface-emitting lasers radiating in two opposite directions
Authors: Wakabayashi S. , Mutoh K. , Nakajima M. , Toyoda Y.
Published: July 2002

A 1.3 μm InGaAsP/InP surface-emitting laser of a new design is demonstrated. It consists of internal and external 45° micromirrors and emits beams from both the front and rear surfaces. The device has a buried crescent laser structure with reflection mirrors etched at vertical and 45° to the plane of the active layer. The mirror facets are fabricated using one reactive ion-beam etching process. A threshold current of 80 mA, and each output power above 0.2 mW are achieved at room temperature.
Improved optical transmission of KTiOPO4 crystals through cerium-doping and oxygen annealing
Authors: Bordui P. F. , Blachman R. , Norwood R. G.
Published: July 2002

KTiOPO4 single crystals were grown from cerium-doped potassium phosphate fluxes. Cerium-doped crystals exhibited increased optical transmission relative to undoped material from the UV band edge to roughly 800 nm. Oxygen annealing was performed on undoped and cerium-doped crystals. The effects on transmission of oxygen annealing were qualitatively similar to those brought about by cerium doping although roughly five times smaller in magnitude. Cerium doping had no observable influence on the nonlinear optical coefficients but altered slightly the crystal’s birefringence.
Resonant tunneling of electrons in Si/Ge strained-layer double-barrier tunneling structures
Authors: Chiang J. C. , Chang Yia-Chung
Published: July 2002

Resonant-tunneling characteristics of electrons in Si/Ge strained-layer double-barrier structures are investigated within an antibonding-orbital model. The model is capable of describing the low-lying conduction bands accurately throughout the entire Brillouin zone. J-V curves for some selected Si/Ge strained-layer double-barrier structures for three different crystallographic orientations are studied. Negative differential resistances are found for these structures grown along [001] and [111] directions, but not along the [110] direction.
Growth rate suppression of InGaAs film grown by laser-assisted chemical beam epitaxy
Authors: Iga Ryuzo , Sugiura Hideo , Yamada Takeshi
Published: July 2002

The mechanism for the grow rate suppression of InGaAs by Ar ion laser-assisted chemical beam epitaxy is studied. A comparison of the cross-sectional profile in the laser-irradiated area with the distribution of the substrate temperature formed by laser irradiation reveals that laser-induced heating is due to the growth rate suppression. The dependence of the InGaAs growth rate on the AsH3 flow rate suggests that the decrease in the As flux suppresses the InGaAs growth rate without laser irradiation. These results indicate that the evaporation of As atoms from the growing surface due to laser-induced heating is the cause of the growth rate suppression of InGaAs.
Application of an emitter edge-thinning technique to GaAs/AlGaAs double heterostructure-emitter bipolar transistor
Authors: Liu Wen-Chau , Guo Der-Feng , Lour Wen-Shiung
Published: July 2002

A GaAs/AlGaAs double heterostructure-emitter bipolar transistor (DHEBT), prepared by molecular beam epitaxy, has been fabricated with improved performance. The employment of emitter edge-thinning technique has caused a significant suppression of the surface leakage current. A common-emitter current gain of up to 140 with a negligible collector offset voltage (∼40 mV) was obtained. The undesired knee-shaped characteristics and the reachthrough effect, always observed on the conventional double heterojunction bipolar transistor (DHBT), were eliminated. An interestingly bi-directional and three-terminal controlled switching phenomena may also be exhibited by this device. This gives a substantial flexibility in the device and circuit applications. The electrical performance is believed to be further improved with an adequate design to minimize the area difference between emitter-base (EB) and the base-collector (BC) junction.
Silicon epitaxy from silane by atmospheric-pressure chemical vapor deposition at low temperatures
Authors: Agnello P. D. , Sedgwick T. O. , Bretz K. C. , Kuan T. S.
Published: July 2002

Epitaxial silicon has been grown in an ultraclean system at atmospheric pressure and low temperatures (650–750 °C) using silane as a Si source in a He carrier gas. The depositions were nonselective (blanket) and demonstrate the broad capabilities of the low-temperature atmospheric-pressure growth apparatus that has previously been used for selective deposition of Si and SiGe from dichlorosilane (DCS) in H2. n-type doping using PH3 was also carried out and doping levels exceeding 1×1020/cm3 were obtained. However, abrupt doping pulses, as have been obtained for Si growth from DCS in the same temperature regime, were not achieved. In addition, PH3 was found to diminish the growth rate and degrade the crystal quality of the layers. The films grown from silane exhibited higher levels of oxygen at the interface between the epitaxial layer and the substrate than did films grown from DCS in the same temperature range. However, high quality films, free from extended defects, as determined by transmission electron microscopy (TEM), could still be achieved.
InGaAs/GaAs quantum wires defined by lateral top barrier modulation
Authors: Gréus Ch. , Forchel A. , Straka J. , Pieger K. , Emmerling M.
Published: July 2002

We have fabricated buried InGaAs/GaAs quantum wires with widths down to 35 nm by using a novel and simple approach. The essential technological step is a selective wet etch process by which the material of the top GaAs barrier layer of a quantum well substrate is removed between quantum wire regions defined by high resolution electron beam lithography. The semiconductor vacuum boundary which locally replaces the energy band discontinuity of the quantum well induces a potential barrier which leads to a lateral potential well within the InGaAs layer. The wires show high emission intensity even for narrow wire widths and a significant shift of the emission to high energy for the smallest wires.
Electron velocity-field characteristics of In0.52Al0.48As
Authors: Kim H. S. , Tian H. , Kim K. W. , Littlejohn M. A.
Published: July 2002

Theoretical results of electron transport in n-type In0.52Al0.48As are presented. The transport properties of this important semiconductor were obtained using the Monte Carlo method. In particular, velocity-electric field characteristics for different temperatures and doping concentrations in bulk In0.52Al0.48As are calculated for the first time. Physical parameters for In0.52Al0.48As (which is lattice-matched to InP and In0.53Ga0.47As) were obtained based on interpolation of available experimental and theoretical results for InAs, AlAs, and In0.75Al0.25As. Our study suggests that In0.52Al0.48As has electron transport properties which are comparable to and complimentary with those of other materials lattice-matched to InP.
Characteristics of plasma deposited tungsten Schottky contacts to GaAs
Authors: Kim Yong Tae , Lee Chang Woo , Han Chul Won , Hong Jong Sung , Min Suk-Ki
Published: July 2002

A low resistive tungsten (W) Schottky contact to GaAs has been developed by plasma enhanced chemical vapor deposition. The resistivity of tungsten (W) films deposited on GaAs at 300 °C is about 18 μΩ cm and the film structure is (111) oriented α-phase W coexisting with (200) and (211) oriented β-phase tungsten. The resistivity of W films deposited above 350 °C is increased due to the diffusion of Ga and As atoms from GaAs into W films. This has been confirmed by secondary ion mass spectroscopy. I-V characteristics of GaAs Schottky contacts formed at 300 °C show that the maximum barrier height is 0.81 eV and the ideality factor is 1.04. They are not degraded during rapid thermal annealing at temperatures ranging from 500 to 700 °C for 10 s without an arsenic overpressure.
Large negative differential resistance in a quasi-one-dimensional quantum wire
Authors: Yu-Kuang Hu Ben , Das Sarma S.
Published: July 2002

We calculate finite temperature inelastic scattering rates and mean free paths of electrons injected into a quantum wire containing a quasi-one-dimensional electron gas. We show that there is a very sharp increase in the electron scattering rate at the one-dimensional plasmon emission threshold. Based on these results, we suggest the possibility of a one-dimensional hot-electron device which possesses an I-V curve with a sharp onset of a large negative differential resistance.
Carrier-induced change in index, gain, and lifetime for (InAs)1/(GaAs)4 superlattice lasers
Authors: Dutta N. K. , Chand N. , Lopata J.
Published: July 2002

The carrier density dependence of gain, index, and carrier lifetime has been measured for (InAs)1/(GaAs)4 short-period superlattice lasers. The 500-μm-long lasers have a threshold current density of 200 A/cm2 and exhibit a small carrier-induced change in refractive index (Δn/ΔN∼2×10−22 cm3). The small Δn/ΔN also results in small linewidth enhancement factor (α∼1.1) of these lasers. The measured dependence of carrier lifetime on carrier density can be fitted to a bimolecular recombination model which suggests that radiative recombination is the dominant recombination mechanism in these structures.
Synchrotron radiation-assisted silicon homoepitaxy at 100 °C using Si2H6/H2 mixture
Authors: Nara Yasuo , Sugita Yoshihiro , Horiuchi Kei , Ito Takashi
Published: July 2002

Epitaxial silicon film is deposited on a Si(100) substrate by synchrotron radiation irradiation. Reflection high-energy electron diffraction and high-resolution transmittance electron microscopy observation reveal that epitaxial growth can be realized at temperatures as low as 100 °C. At substrate temperatures above 300 °C, the films show a clear 2×1 reconstructed surface, indicating a fairly good crystal quality. Below 500 °C, the growth rate increases as the substrate temperature is lowered, meaning that the surface adsorption of source gas and/or photogenerated radicals plays an important role in the epitaxial growth reaction.
Small-signal predictions of the well-barrier hole burning model on quantum-well laser dynamics
Authors: Vassell M. O. , Sharfin W. F. , Rideout W. , Lee Johnson
Published: July 2002

The mutual effect of well-barrier (WB) hole burning and nonlinear gain on the resonance characteristics of quantum-well lasers are investigated. A small-signal impulse response is derived in order to connect the experimental fitting parameters (damping rate, resonance frequency, and K factor) with the parameters (capture time, ratio of carrier capture and release times, and nonlinear gain coefficient) of the WB model. This connection is examined from approximate analytic formulae, and limits on the 3 dB bandwidth are deduced from exact numerical data. It is shown that both mechanisms tend to increase the degree of damping, but the WB process becomes more efficient with nonlinear gain than without it.
Influence of iodine implantation on the properties of polypropylene
Authors: Švorč́̌ik V. , Rybka V. , Volka K. , Hnatowicz V. , Kvítek J. , Peřina V.
Published: July 2002

The implantation of iodine atoms into polypropylene and the related changes of substrate physicochemical properties have been studied by means of optical spectroscopy, by the Rutherford backscattering technique and by the measurement of substrate surface energy. Iodine atoms are not chemically bonded in the polymer. During the ion implantation, carbonyl groups and conjugated double bonds are created in the polymer and its surface polarity is increased. The latter effect is more pronounced for the implantation of heavier I+ ions than for F+ ion implantation. After ion implantation, the electrical conductivity of the polypropylene is increased by eight orders of magnitude.
Ion-induced modification of graphite coatings
Authors: Gupta B. K. , Janting J. , Jensen U. M. , Pedersen G. N. , So/rensen G.
Published: July 2002

Burnished graphite powders and physical vapor-deposition (PVD) coatings of layered crystalline materials such as MoSx have often been used as solid lubricants. This letter will report on a novel ion-induced modification of a graphite-powder coating on a silicon surface. Even at very low ion doses, the bombardment results in structural modifications observed as a considerable reduction in x rays reflected from the (002) sliding planes, which indicates an amorphization process. Transmission electron microscopy (TEM) studies have confirmed almost complete amorphization with 200 keV Ar ions at 1016 ions cm−2. A commercial scanning tunneling microscope (STM) was used as an advanced profilometer to study ion-induced changes in the surface morphology at the powder surface. The mechanical properties of the combined graphite-coating/silicon system were studied by nanoindentation technique, and the perspectives in ion-beam burnishing of graphite coatings will be discussed.
Fabrication of thin film Nb-(fine Nb wires)-NbN weak links for superconducting quantum interference device applications
Authors: Abe H. , Hamasaki K. , Ikeno Y.
Published: July 2002

Thin film Nb-(fine Nb wires)-NbN dc-superconducting quantum interference devices (SQUIDs) with well-balanced critical current have been reproducibly fabricated by applying an electric field simultaneously to two insulating Nb/MgO/NbN edge-sandwiches (each junction area=0.2 μm2) in a superconducting loop, in liquid helium. Although the critical current of a dc-SQUID is not yet controlled sufficiently, this fabrication technique is well suited to use in short weak link dc-SQUIDs, thanks to the reproducibility of dc-SQUIDs with well-balanced critical current, the simplicity of fabrication processes, and the large device resistance.
Theoretical analysis of dynamic response of asymmetric dual quantum well lasers
Authors: Ikeda Sotomitsu , Shimizu Akira
Published: July 2002

Dynamic responses of the photon and carrier densities in an asymmetric dual quantum well laser which exhibits wavelength switching are analyzed theoretically. The laser consists of two different quantum wells isolated by a high and/or thick barrier layer that results in an inhomogeneous carrier injection into the two wells. The calculated pulse response at a voltage of the dual-wavelength lasing shows that the emission of the shorter wavelength light precedes that of the longer wavelength light by a nanosecond, in agreement with recent experimental results.
Ballistic electron emission microscopy of laterally patterned microstructures
Authors: Davies A. , Couillard J. G. , Craighead H. G.
Published: July 2002

Ballistic electron emission microscopy (BEEM) has been used to investigate and image microfabricated Au/SiGe features. Electron beam lithography and dry etching were used to construct arrays of holes in a SiO2 layer and etched indentations in SiGe. The electronic transport properties of the fabricated structure and adjacent unpatterned region were then characterized and imaged with BEEM. These studies demonstrate that BEEM is capable of resolving transport variation with 1–2 nm spatial resolution and can be used to study the microscopic effects of reactive ion etching. The types of imaging contrast and subsurface electron transport information obtainable from BEEM cannot be obtained by other scanned beam or scanned probe techniques.
In situ infrared and mass spectroscopic study of the reaction of WF6 with hydrogenated amorphous silicon
Authors: Wadayama Toshimasa , Shibata Hironobu , Ohtani Tsutomu , Hatta Aritada
Published: July 2002

The reaction process of tungsten hexafluoride (WF6) with photochemically deposited hydrogenated amorphous silicon was studied by polarization modulation infrared spectroscopy and quadruple mass spectrometry. Infrared absorption bands due to species (SiH3 and SiH2) incorporated in the hydrogenated amorphous silicon were decreased in intensity during exposure of WF6. The reduction rate was faster for the SiH3 species than for the SiH2 species. The mass spectrometric analysis revealed that evolution of hydrogen into the gas phase took place prior to that of silicon fluorides. These results strongly suggest that WF6 reacts preferentially with the SiH3 species present in the hydrogen-rich surface layer.
Photoacoustic studies of interaction of O2 with Cu2O thin films
Authors: Abu-Zeid M. E. , Yousef Y. A. , Kordia H. A.
Published: July 2002

Photoacoustic spectroscopy was used, for the first time, for the determination of the thickness of CuO impurity layer developed over the surface of Cu2O thin films during their electrodeposition processes. The thickness of the CuO protective layer over the surface of Cu2O thin films when the latter were heated in oxygen was also determined.
Glow discharge plasma switch controlled by a small magnetic field
Authors: Rocca J. J. , Floyd K.
Published: July 2002

A cold plasma switch scheme with opening and closing capabilities is reported. An externally applied magnetic field causes a low pressure hollow cathode discharge to transition from a low impedance mode sustained by oscillating beam electrons into a virtually collisionless high impedance mode. The impedance of a 10 A discharge was demonstrated to increase by 20 with the application of a field of 0.018 T.
Absence of low temperature saturation of electron–electron scattering in a single mode quantum wire
Authors: Fasol Gerhard
Published: July 2002

At helium temperatures electron–electron scattering determines the phase breaking and therefore limits the size of quantum interference devices. The electron–electron scattering times and scattering lengths are calculated numerically for ideal single mode quantum wires. The striking result of the present work is that there is no saturation of the electron–electron scattering time at low temperatures in an ideal single mode quantum wire without impurity scattering, in contrast to the two- and three-dimensional cases. Phase coherence lengths up to 10 mm are predicted for mK temperatures and up to 50 μm around 4 K. Conditions to observe such long coherence lengths are discussed.
Low-threshold InGaAs strained-layer quantum well lasers (λ=0.98 μm) with GaInP cladding layers prepared by chemical beam epitaxy
Authors: Tsang W. T. , Kapre R. , Wu M. C. , Chen Y. K.
Published: July 2002

We report on the InGaAs/GaAs/GaInP strained-layer quantum well (QW) lasers grown by chemical beam epitaxy (CBE). The single QW broad-area layers have a very low threshold current density of 70 A/cm2, which is among the lowest value reported for InGaAs/GaAs/GaInP lasers. Ridge-waveguide lasers emitting at 0.98 μm have a continuous wave (cw) threshold of 7.8 mA for a 500-μm-long cavity and a differential quantum efficiency as high as 0.9 mW/mA. Internal quantum efficiency of 0.95 and internal waveguide losses of 2.5 cm−1 were obtained. Linear cw output power of 100 mW was obtained. These results demonstrate that CBE is capable of growing 0.98 μm InGaAs strained-layer QW lasers having performance similar to the best prepared by other epitaxial growth techniques.
Many-body treatment on the modulation response in a strained quantum well semiconductor laser medium
Authors: Chow W. W. , Pereira M. F. , Koch S. W.
Published: July 2002

The carrier density modulation response of a semiconductor laser medium is analyzed. The differential gain and linewidth enhancement factor are computed as functions of strain and threshold gain. The example of InGaAs/InP with different InAs content is used to illustrate the situations of zero, tensile and compressive strain.
Critical currents of silver-sheathed bismuth-based tapes at 20 K: Small coils and field orientation anisotropy in external fields up to 20 T
Authors: Sato Ken-ichi , Shibuta Nobuhiro , Hikata Takeshi , Kato Takeshi , Iwasa Yukikazu
Published: July 2002

Critical currents, including field orientation anisotropy, of silver-sheathed bismuth-based superconducting tapes, for both small coils and short samples, have been measured at 20 K (liquid hydrogen) in external fields up to 20 T. The performance of two small coils is consistent with the critical current data of short samples. One coil, at 20 K and in a field of 20 T, for example, produced a self field of 0.35 T (Ic=136 A; Jc=1.7×104 A/cm2). Short-sample critical current data indicate that field orientation anisotropy is more pronounced at 20 K than at 4.2 K. At 20 K and 20 T, e.g., Jc(H∥), critical current density in the parallel field orientation, is 5.23×104 A/cm2, while Jc(H⊥), critical current density in the perpendicular field orientation, is 1.75×104 A/cm2, an anisotropy factor, Jc(H⊥)/Jc(H∥), of 0.34. In the field range 2–15 T, the anisotropy factor at 20 K ranges 0.51–0.55.
Role of stress in irradiation-then-anneal technique used for improving radiation hardness of metal-insulator-semiconductor devices
Authors: Shu Kuei , Liao Chang , Hwu Jenn-Gwo
Published: July 2002

The improvement efficiencies of the newly reported irradiation-then-anneal (ITA) treatments applied to improve the radiation hardness of metal-insulator-semiconductor (MIS) devices with various interfacial stresses were studied. Each ITA treatment includes an irradiation of Co-60 with a total dose of 106 rads (SiO2) and an anneal in N2 at 400 °C for 10 min, successively. It is found that the efficiency of improvement strongly depends on the number of ITA treatments and especially on the interfacial stress of device. These dependencies should be explained by the possible release of SiO2/Si interfacial stress by ITA treatments.
Ambipolar lifetimes in GaAs/AlGaAs self-electro-optic-effect devices
Authors: Swaminathan V. , Freund J. M. , Focht M. W. , Guth G. D. , Przybylek G. J. , Smith L. E. , Leibenguth R. E. , D’Asaro L. A.
Published: July 2002

We have used an electrical technique to determine the ambipolar lifetime in p-i-n GaAs/AlGaAs self-electro-optic-effect devices in which the i region consists of a multiple quantum well structure (MQW). From an analysis of the voltage drop in the i region obtained from the forward current-voltage characteristics, values for the ambipolar lifetimes are derived for diodes with different MQW. A value of 80–90 ps is determined for the ambipolar lifetime which is found not to change significantly when the AlxGa1−xAs barrier thickness or composition is reduced from 65 to 35 Å or x∼0.3 to 0.2, respectively, in the MQW. Since these changes in the barrier have previously been shown to improve photoresponse efficiency of the p-i-n diode, it is inferred that the carrier escape and collection times are smaller than 80–90 ps in devices with thin (35 Å) or low (x∼0.2) AlxGa1−xAs barrier.
Loading effect of quartz microwave window on SF6 plasma in an electron cyclotron resonance reactor
Authors: Watts Andrew J. , Varhue Walter J.
Published: July 2002

The choice of dielectric material for use as a microwave window, or liner, in an electron cyclotron resonance reactor can affect the plasma conditions and process results. SF6 plasma characterization data were compared using a quartz window with and without an alumina cover plate. Both free fluorine and ion current density were suppressed when only the quartz window was used. The loading effect of the uncovered quartz window resulted in a reduced silicon etch rate at the downstream substrate position. The etch rate was further decreased by an SiO2 deposition at the substrate.
Magnetically enhanced reaction sintering of textured YBa2Cu3Ox
Authors: Sarkar Partho , Nicholson Patrick S.
Published: July 2002

Liquid phase reaction sintering of YBa2Cu3Ox electrophoretically deposited thick films has been conducted in a magnetic field (∼1 T). The magnetic field influences the crystallographic orientation of the final microstructural grains (texturing). It is suggested that the magnetic field does not influence the orientation of nuclei during the nucleation process but induces physical rotation of the monograins in the sintering liquid and influences their grain growth.
Stacking faults under reoxidized nitrided oxides
Authors: Kolachina Sivarama Krishna , Lal R.
Published: July 2002

Processing induced stacking faults below reoxidized nitrided oxides have been observed by electron beam induced current (EBIC) imaging and by secondary electron imaging after preferential etching. Comparative studies of stacking fault lengths with those of dry and nitrided oxides show that the growth rates of stacking faults are anomalously high during reoxidation. A large proportion of these stacking faults show electrical activity in EBIC images. This is reflected in the degradation of effective generation lifetimes as seen in transient capacitance measurements.
Tunneling stabilized magnetic force microscopy of BaFe12O19 with a thin film tip
Authors: Wadas A. , Hug H. J. , Güntherodt H.-J.
Published: July 2002

Magnetic domains of BaFe12O19 have been imagined with a scanning tunneling microscope having a flexible, magnetic tip. We have found that Co thin films evaporated on a silicon tip, integrated with a cantilever, can give high lateral resolution, below 50 nm. Therefore, we have been able to image domains and domain walls simultaneously. We have observed domains of 1.9 μm width and domain walls of 270 nm width. We explained the data using existing models.
Electrochromism of vanadium-titanium oxide thin films prepared by spin-coating method
Authors: Nagase Katsumi , Shimizu Youichi , Miura Norio , Yamazoe Noboru
Published: July 2002

Electrochromic properties of V2O5-TiO2 thin films prepared by a spin-coating method were strongly dependent on the film compositions and heat-treatment temperatures. It was found that the nearly amorphous film of V2O5-TiO2 (3:7 in molar ratio) heat-treated at 400 °C showed coloration to reddish brown when polarized at −0.8 V vs SCE. This new coloration was concluded to be ascribable to amorphous vanadium oxide.
Epitaxial growth of an Al/CaF2/Al/Si(111) structure
Authors: Cho C.-C. , Liu H.-Y. , Tsai H.-L.
Published: July 2002

Despite their large lattice mismatch (∼25%), epitaxial CaF2 films have been grown on single crystal Al(111) on Si(111) by low temperature molecular beam epitaxy. X-ray diffraction shows that the orientations of the CaF2 are the same as those of the Al films, whether the orientations of the Al are the same rotated 180° or with respect to the underlying Si substrate. Furthermore, our successful fabrication of an epitaxial Al/CaF2/Al/Si(111) structure suggests that Al can be a useful conductor material in three-dimensional device integration.
New method of generating cylindrical imploding shocks using a flyer disk
Authors: Fujiwara K. , Hiroe T. , Matsuo H.
Published: July 2002

A pancake-like explosive layer loaded over a circular disk (flyer) was detonated from the periphery. The flyer was locally accelerated downward causing a deformation front to propagate toward the center as it was swept by the detonation front. This acted as a cylindrical piston and a cylindrical imploding shock was generated. Shocks were observed by framing camera photographs. The motion of the flyer was also investigated analytically assuming a simple theoretical model.
Interband absorption in α-Sn/Ge short-period superlattices
Authors: Olajos Janos , Wegscheider Werner , Abstreiter Gerhard
Published: July 2002

Band-to-band infrared absorption has been studied in a series of Sn1Gem (m=11, 15, and 21) strained layer superlattices for the first time. The absorption coefficient shows a quadratic increase with two onsets, characteristic for indirect transitions. From a numerical fit to the absorption spectra, band gap energies are determined in the energy range between 0.55 and 0.75 eV, in accordance with theoretical calculations. The temperature dependence of the band gaps show the usual behavior, at low temperatures quadratic and at higher temperatures linear decrease with increasing temperature.
Change in bonding properties of amorphous hydrogenated silicon-carbide layers prepared with different gases as carbon sources
Authors: Fölsch J. , Rübel H. , Schade H.
Published: July 2002

Amorphous hydrogenated silicon-carbide films (a-SiC:H) were deposited in a standard rf glow discharge. Various gases as carbon sources, in addition to silane (SiH4), were used, namely methane (CH4), disilylmethane (DSM), trisilylmethane (TSM), and tetrasilylmethane (TetraSM). All our films show low hydrogen contents (NH≤2.5×1022 cm−3 for EG≤2.4 eV, determined by elastic recoil detection analysis) and low Urbach energies (E0≤70 meV for EG≤2.0 eV, determined by photothermal deflection spectroscopy). Infrared spectroscopy reveals that the more Si—C bonds are offered in the gas phase by using different carbon sources as feedstock, the more Si—C bonds are incorporated into the a-SiC:H solid. Furthermore, the number of CH3 groups decreases with the increasing number of Si—C bonds. The ratio of the hydrogen to the carbon content suggests less CH3 groups to be present in our films, compared to films of other authors.
Inversion from selective homoepitaxy of Si to selective Si film deposition on SiO2 using an ultraclean electron cyclotron resonance plasma
Authors: Matsuura Takashi , Ohmi Tadahiro , Murota Junichi , Ono Shoichi
Published: July 2002

Plasma enhanced selective deposition of Si has been investigated using an ultraclean electron cyclotron resonance plasma. Selective homoepitaxy of Si without substrate heating has been achieved for the first time by decomposition of SiH4 with a plasma generated from dilute H2 in Ar mixtures. Moreover, the selectivity can be inverted to deposit Si films only on SiO2 through changes in the plasma conditions. Based on the x-ray photoelectron spectroscopy analysis and experiments investigating growth with and without ion bombardment, it is concluded that competitive contributions of ion induced decomposition of SiH4 and chemical etching with hydrogen radicals play important roles in the selectivity inversion.
Accelerated bulk synthesis of CaxY1−xBa2Cu4Oy (x=0, 0.1) by molten silver
Authors: Wu Nae-Lih , Yu Hon-Da , Wei S. H.
Published: July 2002

A new process which enables fast bulk synthesis of CaxY1−xBa2Cu4Oy (x=0, 0.1) (the 124 compound) has been developed. This process involves calcination of a reactant mixture containing CaxY1−xBa2Cu3Ox (the 123 compound) and CuO in a 1:1 ratio with silver under conditions where 124 is a stable phase and where melting of silver takes place. The calculation time required for complete 124 formation can be reduced, for example, to less than 10 h with an addition of 20% (by weight) silver. Energy dispersive x-ray spectroscopy and x-ray diffraction analyses indicate no substitution of Ag within the 124 structure. The synthesized bulks contain 124 grains and Ag aggregates and show Tc(onset) of 80 K and Tc(zero) of 78 K for the pure 124 and those of 87 and 80 K for the Ca-doped (x=0.1) one. The phase diagram showing the dependence of the acceleration effect on temperature and oxygen pressure is established.
Molecular beam epitaxial growth of InGaAlAs/InGaAs heterojunction bipolar transistors on highly resistive low temperature InAlAs epilayers
Authors: Dodabalapur A. , Chang T. Y.
Published: July 2002

In0.52Al0.48As epilayers grown by molecular beam epitaxy (MBE) at low temperatures typically possess resistivities of more than 105 Ω cm. We propose the use of such highly resistive epilayers to vertically isolate different devices on InP substrates. We demonstrate that high performance In0.52Ga0.24Al0.24As/In0.53Ga0.47As heterojunction bipolar transistors can be grown on top of such high resistivity buffer In0.52Al0.48As layers. Such HBTs have dc current gains of 1000 and emitter-base pn junctions with ideality factors of 1.05. However, the MBE growth conditions required to obtain such good material are quite critical. We describe these conditions and also the electrical properties of both the HBTs and the resistive InAlAs layers.
Optical evaluation of an AlAs/AlGaAs visible Bragg reflector grown by chemical beam epitaxy
Authors: Armstrong J. V. , Farrell T. , Boyd A. , Beanland R.
Published: July 2002

A 21 layer AlAs/Al0.4Ga0.6As multilayer structure, designed as a Bragg reflector centered at 670 nm, has been grown by chemical beam epitaxy. The growth was monitored in real time by dynamic optical reflectivity (DOR) using a 670 nm semiconductor diode laser. The resultant DOR trace was compared to a computer simulation for the growth structure and good agreement is obtained using layer thicknesses measured by transmission electron microscopy. The wavelength dependent reflectivity of the Bragg reflector was measured using a grating spectrometer and good agreement is obtained to a computer simulation once the dispersive complex refractive index is taken into account.
Low-temperature Si/Si1−xGex/Si heterostructure growth at high Ge fractions by low-pressure chemical vapor deposition
Authors: Schütz Reiner , Murota Junichi , Maeda Takahiro , Kircher Roland , Yokoo Kuniyoshi , Ono Shoichi
Published: July 2002

The growth of a Si/Si1−xGex/Si heterostructure at high Ge fractions was investigated by an ultraclean low-pressure chemical vapor deposition using SiH4 and GeH4 gases in the temperature range of 450–650 °C. It was found that a lowering of the deposition temperatures of the Si1−xGex and Si capping layers is necessary with the increasing Ge fraction in order to prevent island growth of the layer during deposition. For a Ge fraction around 0.2, atomically flat surfaces and interfaces can be obtained by depositing Si1−xGex and Si capping layers at 550 °C. For higher Ge fractions, even much lower deposition temperatures are suitable, namely 450 °C for a Si0.3Ge0.7 layer and 500 °C for a Si0.5Ge0.5 layer, respectively, with a Si capping layer deposited at temperatures of 550 °C or less. Nevertheless, the degradation of the Si0.3Ge0.7 layer with the capping layer was not observed even after a wet oxidation at 700 °C.
High power monolithically integrated diode laser, preamplifier, and coherent beam expander
Authors: O’Brien S. , Mehuys D. , Welch D. F. , Parke R. , Scifres D.
Published: July 2002

An integrated coherent beam expander utilizing a transverse leaky mode waveguide has been integrated with a single mode distributed Bragg reflector laser and a preamplifier producing powers in excess of 70 mW cw in a single spectral and spatial mode across an aperture over 100 μm wide. The far-field pattern in the direction parallel to the plane of the p-n junction, consists of one main lobe 0.45° wide, indicating that the beam is coherent over the full emitting aperture. The expanded beam is suitable as an injection source for an integrated broad area amplifier.
La2−xSrxCuO4(110) thin films epitaxially grown along the CuO2 plane on Pr2CuO4 single crystals
Authors: Sato H. , Naito M. , Arima T. , Tokura Y.
Published: July 2002

The epitaxial growth of superconducting copper oxide films on nondoped insulating copper oxide single crystals produced high-quality epitaxy perpendicular to the c axis, namely along the CuO2 plane. The (110) oriented La1.84Sr0.16CuO4 (LSCO) thin films with Tc=21 K were successfully grown on (110) Pr2CuO4 single-crystal substrates using 90° off-axis sputtering. The x-ray diffraction and the anisotropic resistivity indicate perfect in-plane epitaxy. Scanning electron microscopy (SEM) shows fairly smooth surface of the (110) LSCO film.
Coulomb enhancement of the third-order optical nonlinearities in quantum wells
Authors: Zal/użny M.
Published: July 2002

The investigation of Khurgin and Li [Appl. Phys. A 53, 527 (1991)] on the electrostatic Coulomb enhancement of the third-order intersubband nonlinearities in stepped quantum wells is extended by taking into account the modification of the intersubband resonant energy by the depolarization effect. It was found that the ratio of the depolarization enhancement factor (ηd) to the electrostatic Coulomb enhancement factor (ηe) strongly depends on the shape of the quantum well. Obtained results show that, in the case of the conventional square quantum well, factor ηd is several times larger than ηe while in strongly asymmetric stepped quantum wells ηd≪ηe.
Low-temperature solid-phase heteroepitaxial growth of Ge-rich SixGe1−x alloys on Si (100) by thermal annealing a-Ge/Au bilayers
Authors: Ma Z. , Xu Y. , Allen L. H.
Published: July 2002

Heteroepitaxial layers of SixGe1−x alloys were grown on Si(100) by thermal annealing bilayers of a-Ge/Au deposited on single-crystal Si (sc-Si) substrates at 300 °C. During annealing, Ge dissolves into the Au layer and then grows epitaxially to the substrate, with the final structure changing from a-Ge/Au/sc-Si to Au/SixGe1−x/sc-Si. The SixGe1−x layer was found to be Ge rich (x≊0.15) from AES and STEM analysis and to be epitaxial to the Si(100) substrate from the x-ray rocking curve and RBS channeling measurements. Stacking faults and microtwins are the major defects in the epitaxial film, as observed by cross-sectional TEM. High-resolution TEM analysis of the SixGe1−x/Si interface shows that the growth initiates at specific areas of the original Au/Si interface. This work demonstrates for the first time both heteroepitaxial growth and the growth of SixGe1−x alloys on Si(100) using solid phase epitaxy with an eutectic-forming metal as the transport medium.
InGaAs/AlGaAs strained quantum well laser with semi-insulating low temperature GaAs and lateral n-p-n current confinement structures grown by molecular beam epitaxy
Authors: Takamori T. , Sin Y. K. , Watanabe K. , Kamijoh T.
Published: July 2002

A combination of a lateral n-p-n junction using an amphoteric doping of Si in GaAs and a semi-insulating GaAs grown at low temperature is applied for the first time to a novel current confinement structure for an index-guided InGaAs strained quantum well laser grown by two-step molecular beam epitaxy. A threshold current of 7.4 mA and total external differential quantum efficiency of 59% under room temperature continuous wave operation are achieved with devices fabricated by a self-aligned process.
Evidence of carrier confinement in nonlinear GaAs/AlGaAs multiple quantum-well microresonators fabricated using alloy mixing techniques
Authors: Massa J. S. , Buller G. S. , Walker A. C. , Oudar J. L. , Rao E. V. K. , Sfez B. G. , Kuselewicz R.
Published: July 2002

Time-resolved photoluminescence measurements with <5 μm spatial resolution have provided direct evidence of carrier confinement in micrometer-dimensioned GaAs/AlGaAs multiple quantum-well microresonators delineated by alloy mixing. Carriers are confined in individual devices of size 2–50 μm without degradation of lifetime.
Theoretical analysis of gain saturation coefficients in InGaAs/AlGaAs strained layer quantum well lasers
Authors: Seki Shunji , Sotirelis Paul , Hess Karl , Yamanaka Takayuki , Yokoyama Kiyoyuki
Published: July 2002

The gain saturation coefficient ε of InGaAs/AlGaAs strained layer quantum well lasers (SL-QWLs) is calculated as a function of strain from intrasubband relaxation times. The intrasubband relaxation times are in turn obtained within the random phase approximation (RPA) including carrier-carrier as well as carrier-polar optical phonon interactions. The band structures are included by using the Luttinger–Kohn Hamiltonian [Phys. Rev. 97, 869 (1955)] and a multiband effective mass equation. It is demonstrated that the gain saturation coefficient increases with compressive strain in the active layer of quantum wells due to a corresponding increase of the intrasubband relaxation time.
In-depth distribution of ion irradiation defects evaluated by mobility of Al0.3Ga0.7As/GaAs two-dimensional electron gas
Authors: Takeuchi Yukihiro , Soga Hajime , Ueno Yoshiki , Kanayama Toshihiko , Sugiyama Yoshinobu , Tacano Munecazu
Published: July 2002

It has been found that the low-temperature (<100 K) mobility of two-dimensional electron gas is a sensitive and quantitative measure for ion irradiation defects. With this technique, the depth distribution of defects resulting from 10-keV Ar ion irradiation (projected range=8.8 nm) to doses of 0.3–6.78×1011/cm2 onto Al0.3Ga0.7As/GaAs heterostructures was evaluated at depth of 60–120 nm. The distribution, which was estimated by reciprocal of mobility, has been found to be exponential with a 1/e penetration length of 20 nm for irradiation temperatures of 85–90 K and 16 nm for room temperature. From this result, it is suggested that the cause of defect penetration in deep regions is the ion channeling.
Some notes on the metal-insulator-semiconductor conductance technique
Authors: Pluciński K. J.
Published: July 2002

This letter reports the study of the small-signal approximations forming the basis of the theory of the metal-insulator-semiconductor conductance technique. It is shown that these approximations may cause significant errors in evaluation and interpretation of the results of the conductance measurements.