bluuebunny/crossref_metadata_2025 huggingface dataset:
InGaAsP ridge waveguide laser array with nonuniform spacing
Authors: Dutta N. K. , Koszi L. A. , Segner B. P. , Napholtz S. G.
Published: July 2002

The fabrication and performance characteristics of InGaAsP (λ∼1.3 μm) ridge waveguide laser arrays are described. The ridges have variable spacing but are chosen to be of equal widths so that the propagation constants, which determine the emission wavelengths, of the individual emitters are equal. The lasers have threshold currents in the range 300–350 mA at 30 °C and have been operated to pulsed output powers of 600 mW/facet. The far field along the junction plane is single lobed with a width characteristic of a phase locked, diffraction limited beam. Measurements of cw emission spectrum also show emission in a single fundamental supermode.
Laser produced percolation structures
Authors: Thuillard M. , von Allmen M.
Published: July 2002

Pulsed laser irradiation of thin Ti films yields structures consisting of metallic islands connected by oxide filaments. The sheet resistivity of the structure is mostly determined by the degree of oxidation of the filaments and can be varied through the laser fluence. By adding gold to the initial layer, the same structures are obtained but oxidation is inhibited. The material is essentially a two-dimensional bond percolator. The temperature coefficient of the resistance is drastically reduced compared to that of the previously investigated Ti-TiOx structures.
Raman scattering as a quantitative tool for residual acceptor assessment in semi-insulating GaAs
Authors: Wagner J. , Seelewind H. , Kaufmann U.
Published: July 2002

Electronic Raman scattering has been employed to characterize as-grown semi-insulating GaAs. All samples investigated exhibit electronic Raman signals from residual acceptors (carbon and/or zinc). The intensity of these signals varies by more than one order of magnitude from sample to sample. Comparative local vibrational mode measurements to determine the carbon content suggest a quantitative correlation with the carbon acceptor concentration. The detection limit for this Raman characterization is well below 1015 acceptors/cm3 for samples cut from 500-μm-thick standard wafer material. Spatially resolved studies show that the scattering intensity fluctuates significantly across a 2-in. GaAs wafer.
Molecular beam epitaxial growth and characterization of a novel superlattice system: Hg1−xCdxTe-CdTe
Authors: Reno J. , Sou I. K. , Wijewarnasuriya P. S. , Faurie J. P.
Published: July 2002

Hg1−xCdxTe-CdTe superlattices of both type I and type III have been grown for the first time using the molecular beam epitaxy technique. The superlattices were grown at 190 °C. They have been characterized by electron and x-ray diffraction, infrared transmission, and Hall measurements. The presence of satellite peaks in the x-ray spectra shows the superlattices to be of high quality. Infrared transmission spectra show that HgCdTe-CdTe superlattices have narrower band gaps than equivalent HgCdTe alloys. These superlattices are p type. Their Hall characterizations, along with magnetotransport experiments, seem to indicate that high hole mobilities observed in p-type HgTe-CdTe superlattices are due to some type of relationship between the two-dimensional heavy hole gas and the interface state existing in type III superlattices.
Amorphous silicon p-i-n-i-p and n-i-p-i-n diodes
Authors: Dresner Joseph
Published: July 2002

This letter describes the preparation and electrical characteristics of a-Si:H p-i-n-i-p and n-i-p-i-n thin-film diodes suitable for driving monochrome liquid crystal displays with more than 500 lines. The symmetrical current-voltage curves in the reverse breakdown regime can be described by i=i0 exp(E/E0), where E0≂9×104 V/cm. In the range 20–125 °C, the current is thermally activated with an energy of 0.25 eV. The response time to applied voltage pulses is ≤10 μs. The stability of the electrical characteristics is adequate for at least 104 h of operation in a liquid crystal display. Electrical characteristics indicate that the reverse breakdown current is a tunneling current injected into the i layer and that electrons are likely to be dominant.
Current drift mechanism in In0.53Ga0.47As depletion mode metal-insulator field-effect transistors
Authors: Taillepied M. , Gourrier S.
Published: July 2002

A study of current drift phenomena of InGaAs depletion mode metal-insulator field-effect transistors fabricated with plasma enhanced chemical vapor deposited Si3N4 is reported for the first time. The data indicate that the current varies logarithmically versus time and that the capture mechanism does not depend on temperature. A strong correlation is demonstrated between the amplitude of the hysteresis of C(V) curves measured on metal-insulator-semiconductor devices and the total oxide thickness located between the deposited dielectric film and the InGaAs layer. This behavior suggests that states situated in this native oxide layer are responsible for the current drift. Moreover, these states are energetically distributed in the band gap of InGaAs.
Preprocessing heat treatment of metal-insulator-semiconductor solar cells
Authors: Wong Dick Y. F. , Lam Y. W.
Published: July 2002

Degradation in performance is reported of metal-insulator-semiconductor solar cells after isochronal and isothermal preprocessing heat treatment. Apart from the bulk lifetime degradation, an enhanced surface recombination is also observed. This is believed to be the first time that degradation in cell performance is reported which is solely due to the heat treatment and not related to the effect of diffusion.
Chloride vapor phase epitaxial growth of a Ga0.52In0.48P/GaAs heterostructure with an abrupt heterointerface
Authors: Hoshino Masataka , Kodama Kunihiko , Kitahara Kuninori , Komeno Junji , Ozeki Masashi
Published: July 2002

Chloride vapor phase epitaxy of Ga0.52In0.48P/GaAs was studied using a reactor with two growth chambers. We have obtained high-purity epitaxial layers of both GaInP and GaAs. For the growth of a heterostructure with an abrupt interface, the optimum growth condition was investigated in detail. Abruptness of the heterointerface was investigated by observing the two-dimensional electron gas at the heterointerface of Ga0.52In0.48P/GaAs by the Hall and Shubnikov–de Haas measurements.
Metastability and polarization effects in a p
n heterojunction device due to deep states
Authors: Stavola Michael , Capasso F. , Nabity J. C. , Alavi K. , Cho A. Y.
Published: July 2002

Unusual metastable and polarization behavior has been observed for Al0.48In0.52As/ Ga0.47In0.53As avalanche photodiodes by capacitance spectroscopy. The metastability arises from interplay of the heterojunction barrier with defects in the Al0.48In0.52As layer. Defect occupation controls the reverse bias characteristics of the device while the heterojunction presents a barrier to carrier capture by the defects.
Linewidth reduction of 1.5-μm grating loaded external cavity semiconductor laser by geometric reconfiguration
Authors: Kuo Chien-Yu , van der Ziel J. P.
Published: July 2002

It is found experimentally that the linewidth of a grating loaded external cavity semiconductor laser is inversely proportional to the square of the linear dimension of the overall cavity. This observed behavior is consistent with the existing theories on the linewidth of a laser with an extended passive cavity. A slope of 6.5×105 Hz cm2 is obtained from least-squares fitting the linewidth vs 1/(cavity length)2 curve at 1 mW of power. However, the linewidth reaches a lower limit when the cavity length is extended beyond a certain limit. This result suggests that additional phase noise term should be included in the calculation of linewidths of these extended cavity semiconductor lasers. We also report a value as small as 18 kHz mW in the linewidth vs 1/(power) curve.
Device quality AlGaAs/GaAs heterostructures grown in a multichamber organometallic vapor phase epitaxial apparatus
Authors: Shealy J. R.
Published: July 2002

The use of a vertical multichamber organometallic vapor phase epitaxial (OMVPE) reactor for the growth of compound semiconductors is described. The formation of abrupt AlGaAs/GaAs heterostructures has been achieved by positioning the substrates by rotation in growth zones with the appropriate combinations of the sources; trimethylgallium, trimethylaluminum, and arsine. Photoluminescence, Raman spectroscopy, and cross-sectional transmission electron microscopy are used to demonstrate the optical quality and structural properties of the epitaxial films produced by this variation of the OMVPE technique. Device quality films are demonstrated by the fabrication of all superlattice separate confining laser structures emitting over the wavelength range from 740 to 855 nm.
Galvanomagnetic properties of lead-telluride quantum wells
Authors: Heremans J. , Partin D. L. , Dresselhaus P. D. , Shayegan M. , Drew H. D.
Published: July 2002

The first in-plane galvanomagnetic measurements on PbTe quantum wells are presented. The samples were 70-Å-wide wells sandwiched between lattice-matched PbEuSeTe layers which have 500 meV gaps. PbTe has a 187 meV gap at 0 K. The magnetoresistance and Hall effect were measured from 0 to 22 T and 0.5 to 300 K. The results can be explained if we assume that the wells are modulation doped p type to 3.7×1013 cm−2, and that there are 3×1012 cm−2 highly mobile holes which show Shubnikov–de Haas oscillations due to the splitting of size-quantized subbands into Landau levels. The influence of illumination is also shown: up to 1014 cm−2 carriers with a lifetime of the order of 102 min can be photoexcited in the structure.
Physical processes in degradation of amorphous Si:H
Authors: Redfield David
Published: July 2002

A critical analysis is given of possible mechanisms of light-induced degradation in amorphous Si:H (a-Si:H) and of the constraints imposed on degradation models by recent experimental observations. Using an analogy with processes in recombination-enhanced degradation of GaAs, it is shown that current intrinsic models for a-Si:H are deficient in two significant respects. It is also found that these intrinsic models cannot explain several important observations. An alternative extrinsic model is shown to be free of these deficiencies.
Asymmetric noise and output power in semiconductor lasers with optical feedback near threshold
Authors: Mink J. , Verbeek B. H.
Published: July 2002

An asymmetry in the output power and the low-frequency noise emitted from the rear and front facets of index-guided semiconductor lasers with a large percentage of optical feedback into the front facet is reported. Transitions from coherent to incoherent feedback-induced properties by modulation of the feedback path length can be distinguished in the output power versus current (L-I) curve. A cross-over point is found only in the front facet L-I curve corresponding to a minimum in the noise. A model is presented which correctly describes the asymmetry between the L-I curve of the front and rear facets. It also predicts the observed cross-over point in the front facet L-I curve.
Existence of metastable step density distributions on GaAs(100) surfaces and their consequence for molecular beam epitaxial growth
Authors: Chen P. , Madhukar A. , Kim J. Y. , Lee T. C.
Published: July 2002

Variations in the static and steady-state specular beam intensity (I0 and IS, respectively) in reflection high-energy electron diffraction from GaAs(100) have been examined as a function of substrate temperature (TS) and As4 pressure in molecular beam epitaxy. At a fixed As4 pressure, regimes of reversible and irreversible behavior of I0 and IS as a function of TS are identified. The irreversible regime of I0 is shown to occur at temperatures close to the congruent temperature. At each temperature in this regime, the existence of smoothest, but metastable, surface step density configuration is demonstrated. The maximum in IS is found to occur in this regime. The surface kinetic processes responsible for this behavior are discussed.
Development of preferentially current-generating silicon solar cells
Authors: Silard Andrei , Pera Florin , Nani Gabriel
Published: July 2002

The work reports the development of ‘‘preferentially current-generating’’ p+-n-n+ silicon solar cells. The distinctive trait of developed devices is their extremely large short-circuit current density Jsc=38–39.7 mA/cm2, which is the highest value of Jsc reported thus far in the literature for ‘‘back-surface-field’’-type cells under AM1 conditions. The conversion efficiency of test cells ranged from 17.1 to 18.15%. The results of this work show clearly that a simple, but adequately designed/processed p+-n-n+ cell fabricated in industrial environment on large area (2 in.) silicon wafers could possess parameters similar or superior to those of sophisticated laboratory samples elaborated on small area silicon chips.
Highly efficient multiple emitter index guided array lasers fabricated by silicon impurity induced disordering
Authors: Thornton R. L. , Burnham R. D. , Paoli T. L. , Holonyak N. , Deppe D. G.
Published: July 2002

We describe the fabrication of closely spaced arrays of buried heterostructure semiconductor lasers by the process of silicon impurity induced disordering. These devices have the low threshold currents which are associated with buried heterostructure lasers, as well as high overall device efficiency. The device we have analyzed for this letter exhibits a threshold current of 53 mA, differential quantum efficiency of 62%, and a total power conversion efficiency of 43% when operating at a power output level of 250 mW. These numbers indicate that this technology is quite promising for the fabrication of high power semiconductor laser arrays.
Electro-optical response of a liquid-crystalline fiber coupler
Authors: Goldburt E. S. , Russell P. St. J.
Published: July 2002

The electro-optical properties of a thin layer of nematic liquid crystal, sandwiched between two side-polished single-mode optical fibers and flanked by electrodes, are investigated by documenting the response of the resulting fiber coupler to electric fields of different frequencies and amplitudes. It is found that similar coupling states (corresponding to similar states of the liquid crystal) are created at every driving frequency if the correct voltage level (above a threshold dependent on the coupling state) is selected. The presence of certain resonance peaks in the frequency response of the liquid crystal (to our knowledge not before observed) is explained phenomenologically in terms of orientational standing-wave patterns between the electrodes.
Real time image subtraction and ‘‘exclusive or’’ operation using a self-pumped phase conjugate mirror
Authors: Kwong Sze-Keung , Rakuljic George A. , Yariv Amnon
Published: July 2002

Real time ‘‘exclusive or’’ operation with an interferometer using a self-pumped phase conjugate mirror is reported. Also, results of image subtraction and intensity inversion are shown.
Photoluminescence of undoped, N+-implanted and C+-implanted AlAs grown by molecular beam epitaxy
Authors: Makita Yunosuke , Kudo Kazuhiro , Momura Toshio , Takeuchi Yoshinori , Yokota Masaki , Mitsuhashi Yoshinobu , Kobayashi Toshihiko , Izumi Tomio , Matsumori Tokue
Published: July 2002

Low-temperature photoluminescence studies of undoped, N+ (nitrogen)-implanted and C+ (carbon)-implanted AlAs grown by molecular beam epitaxy are reported. It was experimentally demonstrated that a dominant emission temporarily denoted by A, observed at 13 meV below the indirect excitonic band gap, Eg,ind(X), is closely related with N isoelectronic impurity atoms. It was also found that the A emission accompanies many one-phonon and two-phonon replicas, among which the longitudinal optical phonon replica is predominant. Carbon atoms were determined not to be principal residual impurities in undoped AlAs. The two conspicuous C-related emissions were revealed by the intentional incorporation of C atoms, which are situated at 60 and 64 meV below Eg,ind(X).
New experimental method for extracting the density and generation annealing rates of interface and oxide traps
Authors: Sah Chih-Tang , Lin Wallace Wan-Li , Hsu Charles Ching-Hsiang , Pan Samuel Cheng-Sheng
Published: July 2002

A new method is proposed which gives the initial and final steady-state densities and the generation-annealing kinetic rates of each interface state and oxide trap species. The number of stress-anneal cycles required to give deterministic values of the rates is equal to the number of interface or oxide traps. An implementation example is given on the post-irradiation room-temperature annealing of the two interface and two oxide traps in a silicon metal-oxide-semiconductor capacitor. Accurate relative hydrogen concentration can also be determined at atomic hydrogen densities as low as 106 atoms/cm3.
Optical properties of β-ZnP2 via photoelectrochemistry
Authors: Ryan M. A. , Parkinson B. A.
Published: July 2002

Photocurrent spectroscopy is used to measure the polarization dependence of optical transitions in β-ZnP2 and to identify an impurity state. A large polarization dependence was measured in the photocurrent spectrum with the light polarized parallel or perpendicular to the c axis of a β-ZnP2 crystal. Structure observed in the spectra was attributed to polaritons and, in the n-type samples, to an impurity level associated with tin.
Dopant redistribution during Pd2Si formation using rapid thermal annealing
Authors: Alvi N. S. , Kwong D. L. , Hopkins C. G. , Bauman S. G.
Published: July 2002

Rapid thermal annealing has been used to form Pd2Si by reacting thin layers of Pd metal on As-implanted Si. An enhanced growth rate for the Pd2Si has been measured, which does not obey the diffusion limited growth kinetics as reported for the furnace reacted Pd2Si. The growing Pd2Si results in As redistribution which is sufficient to displace the shallow p-n junction as the silicide/silicon interface approaches the junction position. The As-implanted profile changes little in the Pd2Si region, with As accumulating at the leading edge of the silicide/silicon interface.
Luminescence investigations of highly strained-layer InAs-GaAs superlattices
Authors: Voisin P. , Voos M. , Marzin J. Y. , Tamargo M. C. , Nahory R. E. , Cho A. Y.
Published: July 2002

We describe photoluminescence investigations in InAs-GaAs superlattices in the thin layer limit (10–20 Å). The data, which are compared to theoretical results obtained from band structure calculations, yield an estimate of the conduction-band discontinuity of 550 meV at the interfaces. They also show that although the superlattice has a band gap (765 meV) close in energy to that of the corresponding bulk InxGa1−xAs alloy (800 meV), the band structures are very different. In the superlattice, electrons and light holes appear to be the important carriers, and they tend to be spatially separated, to the extent that this is meaningful in the thin layer limit.
Photochemical vapor deposition of hydrogenated amorphous silicon films from disilane and trisilane using a low pressure mercury lamp
Authors: Kumata Ken , Itoh Uichi , Toyoshima Yasutake , Tanaka Naoki , Anzai Hiroyuki , Matsuda Akihisa
Published: July 2002

The photolysis of disilane (Si2H6) and trisilane (Si3H8) under direct excitation by light from a low pressure mercury lamp was carried out to prepare hydrogenated amorphous silicon films (a-Si:H). The electronic and optical properties of the films were investigated as functions of preparation conditions such as partial pressure and substrate temperature. The conductivity of the films prepared from Si3H8 at 300 °C was 10−10 S cm−1 in the dark and 10−5 S cm−1 under the illumination of a He-Ne laser with a photon flux of 1015 cm−2 s−1. The high photoconductivity was attained when the silane gas was blown over the substrate from a slit-type nozzle placed beside the substrate plate at a pressure of less than 20 Torr.
Abrupt reduction of the partial sputtering yield of copper in silicon due to beam induced oxidation and segregation
Authors: Wittmaack K.
Published: July 2002

Boron-doped silicon samples with a submonolayer coverage of copper were sputter profiled under O+2 bombardment at energies between 4 and 12 keV and impact angles of 2° and 32°. The profiles of Cu+ secondary ions showed a peak due to the buildup of oxygen in the sample. Under conditions of incomplete oxidation (at 32°) the Cu+ intensity beyond the peak decreased exponentially with a decay length of about 39 nm (8 keV O+2). By contrast, beam induced SiO2 formation (at 2°) resulted in a rather abrupt decrease of the Cu+ intensity (factor of 10 within a sputtered depth of 1.3–3 nm depending on the beam energy). The effect is attributed to very rapid diffusion of copper away from the surface oxide (beam induced segregation).
Direct measurement of the electric-field-dependent absorption coefficient in GaAs/AlGaAs multiple quantum wells
Authors: Wood Thomas H.
Published: July 2002

Although large changes in the absorption coefficient of multiple quantum wells (MQW’s) with applied voltage have been reported, no accurate measurement of the minimum absorption coefficient, which determines the absorption component of the device insertion loss, has been reported. Using a new measurement technique, we measure this minimum absorption coefficient, and determine that, for a device with a 10:1 on/off ratio and a 7 dB insertion loss, absorption contributes 2.2 dB of the insertion loss. We are able to predict absorption losses of future devices and show that, by a slight change in operating wavelength, the absorption loss can be greatly reduced.
Model for electron cooling by radiation losses in plasmas: Application to development of soft x-ray lasers
Authors: Skinner C. H. , Keane C.
Published: July 2002

We present a simple model which may be used to evaluate the suitability of different ions for rapid plasma cooling by line radiation in recombination pumped x-ray laser schemes.
Phase-locked shallow mesa graded barrier quantum well laser arrays
Authors: Mawst L. J. , Givens M. E. , Emanuel M. A. , Zmudzinski C. A. , Coleman J. J.
Published: July 2002

Graded barrier quantum well heterostructures have been grown by metalorganic chemical vapor deposition and processed into real index-guided shallow mesa laser arrays. Single-stripe devices have threshold currents as low as 14 mA (533 μm length) and ten-element arrays have threshold currents as low as 9 mA per stripe with 52% differential quantum efficiency. These arrays operate phase locked with sharp double-lobed far-field patterns up to 1.75 times threshold current.
Small-angle scattering of shaley rocks with fractal pore interfaces
Authors: Mildner D. F. R. , Rezvani R. , Hall P. L. , Borst R. L.
Published: July 2002

Differences have been found in the outer part of the neutron and x-ray small-angle scattering curves for various porous shaly rocks, and are analyzed in terms of fractal interfaces. Neutrons are relatively insensitive to the presence of either hydrocarbons or water in the pores, and always give a smaller Porod exponent than that for x rays, indicating that the hydrocarbon and/or water tend to reside in the small re-entrant parts of the mineral-pore interfaces
Growth law for disk precipitates, and oxygen precipitation in silicon
Authors: Hu S. M.
Published: July 2002

It is shown that the energetically optimum shape of a precipitate which generates strains in the host lattice is a disc with a thickness that increases approximately with the square root of the size (disc radius). This relationship contravenes the two common assumptions that either the thickness or the aspect ratio stays unchanged during precipitate growth. From this relationship is derived a precipitate growth law of r∝t2/3. The results of the analysis are discussed with special reference to the growth of oxygen precipitates in silicon. The change in the morphology of oxygen precipitates with temperatures is also discussed.
Modeling and observation of photoconductivity in polycrystalline silicon
Authors: Singh P. K. , Singh S. N. , Kishore R.
Published: July 2002

We have developed a phenomenological model for the photoconductivity in polycrystalline semiconductors which takes into account the contributions from the majority carriers due to mobility enhancement in addition to the contributions due to photogenerated excess (minority) carriers. The model is applicable for the cases of both partially and completely depleted grains at all intensities of illumination. The model is compared with the experimental data of photoconductivity as a function of intensity of illumination obtained in polycrystalline silicon at different temperatures. The data are in good agreement with the theoretical predictions. The results clearly demonstrate that in polycrystalline materials, photoconductivity is a majority carrier phenomenon at low optical illuminations irrespective of whether the suppression of grain boundary potential barriers is partial or complete. However, at high level conditions, the photoconductivity behavior becomes an excess carrier effect as observed in single crystals.
Fabrication of arrays of GaAs optical bistable devices
Authors: Venkatesan T. , Wilkens B. , Lee Y. H. , Warren M. , Olbright G. , Gibbs H. M. , Peyghambarian N. , Smith J. S. , Yariv A.
Published: July 2002

Arrays of fast optical bistable devices (OBD’) hold excellent promise in the implementation of parallel optical computation systems. The fabrication of an array of 9×9 μm pixels of OBD’s on a GaAs/AlGaAs molecular beam epitaxial layer is reported here. The pixels were defined by reactive ion etching in a freon, helium, and oxygen gas mixture. The array, consisting of over 100×100 devices, formed good quality, uniform interferometers, exhibiting a single fringe in transmitted light. Gate recovery times were reduced by eliminating the top AlGaAs window and by etching 9×9 μm pixels in an array. Uniform arrays of such high quality optical gates or bistable devices could handle thousands of parallel channels at a rate of several gigahertz per channel.
p-n junction formation using laser induced donors in silicon
Authors: Mada Y. , Inoue N.
Published: July 2002

The generation of high concentration defect-related donor states during laser annealing of silicon with surface melting is found. Using these donors, p-n junctions are fabricated on p-type silicon substrate and good diode characteristics are obtained. Oxygen concentration increase in the laser annealed region is observed and suggests that the laser induced donors may be oxygen related. However, these donors are not oxygen thermal donors generally produced at moderate temperatures (<500 °C), because they are not annihilated by annealing at 650 °C. The present method provides for simple, low-temperature p-n junction formation without the addition of dopants. This method will be applicable to device fabrication on processed wafers without disturbing pre-existing device characteristics.
Coherent coupling of diode lasers by phase conjugation
Authors: Cronin-Golomb Mark , Yariv Amnon , Ury Israel
Published: July 2002

We report experimental demonstrations of the use of a photorefractive barium titanate ring passive phase conjugate mirror in the coherent coupling of two GaAlAs diode lasers. By cooling the crystal towards its tetragonal to orthorhombic phase transition, we were also able to achieve infrared photorefractive phase conjugation with gain.
New bar cathode system for cw CO2 transversely excited lasers
Authors: Kasamatsu M. , Shiratori S.
Published: July 2002

A new bar cathode system that is simple and easy to construct was developed. Its characteristics were investigated and compared with a conventional multipin cathode system. The result demonstrated that transversely excited CO2 lasers employing both cathode systems have similar characteristics and also gave about 10 kW output, although oscillation mode patterns of both systems differed a little from each other. The studies showed that we should be able to get a uniform gain distribution and a uniform oscillation mode with a cathode system consisting of variously shaped bars.
Optically induced absorption modulation in GaAs doping superlattices
Authors: Simpson T. B. , Pennise C. A. , Gordon B. E. , Anthony J. E. , AuCoin T. R.
Published: July 2002

Optically generated carriers are used to modulate below-gap absorption in GaAs doping superlattices. Room-temperature modulation is observed when the potential wells are deep (≳1 eV). Spatial separation of the electrons and holes leads to slow recovery of the absorption following generation of the carriers. The amplitude of the absorption modulation shows only a weak dependence on the excitation intensity.
Picosecond laser melting and evaporation of GaAs surfaces
Authors: Liu J. M. , Malvezzi A. M. , Bloembergen N.
Published: July 2002

Picosecond laser-induced melting and evaporation of GaAs surfaces are studied. The high reflectivities of molten GaAs observed at fluences above the melting threshold have a wavelength dependence inconsistent with a simple Drude model for a metallic molten GaAs surface. The observations at high laser fluences suggest that the liquid-vapor phase transition is initiated by a fast-expanding, high-density fluid.
Amorphous and crystalline oxide precipitates in oxygen implanted silicon
Authors: van Ommen A. H. , Koek B. H. , Viegers M. P. A.
Published: July 2002

We studied precipitation of oxygen in the region below the buried oxide of a silicon-on-insulator structure formed by high-dose implantation of oxygen. Underneath the oxide layer there is first a region containing amorphous precipitates, spherical in shape. At greater depth, platelike precipitates of the monoclinic silica phase coesite are observed on {113} silicon planes. The lower interface of the buried oxide is very rough compared to the upper interface. The morphology of the implanted structure is attributed to intrinsic point defects. In particular it is proposed that a high concentration of self-interstitials occurs below the oxide as soon as it becomes a continuous layer. This leads to a large reduction of the oxidation rate in this region. Oxidation then only occurs above the buried oxide, reducing the thickness of the superficial silicon film.
Structure of interfaces in amorphous silicon/silicon nitride superlattices determined by i
n s
i
t
u optical reflectance
Authors: Yang L. , Abeles B. , Persans P. D.
Published: July 2002

The formation of amorphous hydrogenated silicon/silicon nitride (a-Si:H/a-SiNx:H) interfaces is observed in real time by in situ optical reflectance measurements from growing a-Si:H/a-SiNx:H superlattices. The optical data are interpreted by a model of atomically abrupt interfaces with macroscopic roughness on a scale of 10 Å.
Patterning of fine structures in silicon dioxide layers by ion beam exposure and wet chemical etching
Authors: Cleaver J. R. A. , Heard P. J. , Evason A. F. , Ahmed H.
Published: July 2002

Fine structures can be fabricated in silicon dioxide layers by a two-stage process in which localized ion implantation enhances the rate at which the oxide can be etched chemically. This process has been investigated as a technique for maskless microfabrication using a scanning ion beam lithography system.
Integrated-optic, narrow-linewidth laser
Authors: Korotky S. K. , Marcatili E. A. J. , Eisenstein G. , Veselka J. J. , Heismann F. , Alferness R. C.
Published: July 2002

We report the demonstration of the single-frequency and narrow-linewidth (<100 kHz) operation of an extended cavity laser consisting of a Ti:LiNbO3 single-mode waveguide circuit and an InGaAsP waveguide gain medium. A parallel coupled cavity, electro-optic elements for tuning the resonant frequencies of the cavities, and an external phase modulator are integrated on the lithium niobate crystal.
Large photoenhancement of hydrogen-implanted quantized accumulation layers on ZnO surfaces
Authors: Yaron G. , Goldstein Y. , Many A.
Published: July 2002

We report in this letter on an interesting and unexpected effect which is not fully understood yet. Strong hydrogen-implanted accumulation layers on ZnO surfaces, produced and maintained at 80 K, can be further enhanced by illumination with visible light. The enhancement attained is surprisingly large, amounting to a twofold increase in surface electron density, up to 6×1014 cm−2. The photoenhanced layer is less than 10–20 Å in width, thus constituting a two-dimensional electron system, which is by far the strongest ever attained on any semiconductor surface. Measurements of the electron transport characteristics and of the spectral response of the photoenhancement process are presented.
Ion implantation and thermal oxidation as treatments to initiate sustained oxide wear in steels
Authors: Hale E. B. , Kohser R. A. , Reinbold R. A.
Published: July 2002

Both nitrogen implantation (2.5×1017 N+2 /cm2 at 180 keV) and low-temperature (≊315 °C) oxidation are shown to produce an order of magnitude reduction in the wear rate of an SAE 3135 steel. Measurements of the wear rates, wear member asymmetry behavior, and both scanning electron microscopy and Auger studies indicate that the same mechanism leads to the much improved wear rates. Both treatments substantiate the initiator/sustainer wear model, in which the initiation treatment reduces the wear to a low value that is sustained throughout the wear test. The sustained stage is a form of mild wear, which involves oxygen and appears to be oxidative wear.
Anomalous ultrasonic dispersion in fluid-coupled, fibrous composite plates
Authors: Chimenti D. E. , Nayfeh Adnan H.
Published: July 2002

The ultrasonic dispersion characteristics of vertically polarized plate waves in fluid-coupled plates of unidirectional graphite-fiber reinforced epoxy have been found experimentally to display anomalous dispersion. This anomaly consists of a mixing of the two fundamental plate modes at phase velocities near the bulk composite transverse wavespeed. A calculation of ultrasonic reflection from a fluid-coupled composite plate accounts very well for the previously unreported experimental observations. It is demonstrated that the anomalous dispersion is a consequence of the presence of the fluid and is strongly enhanced by the highly anisotropic elastic nature of the composite. It is further shown that a much weaker manifestation of the effect also exists in fluid-coupled plates of elastically isotropic materials.
Light-activated charge storage in amorphous silicon-carbon films
Authors: Könenkamp R. , Paasche S. M.
Published: July 2002

It is shown that deep trapping of excess carriers in amorphous silicon-carbon films can be used for charge storage applications. Using surface-near pulsed carrier generation ‘‘write,’’ ‘‘read,’’ and ‘‘erase’’ operations are illustrated and charge retention times determined for a set of films with differing carbon contents.
Improved uniformity of epitaxial indium-based compounds by atomic layer epitaxy
Authors: Tischler M. A. , Bedair S. M.
Published: July 2002

Atomic layer epitaxy (ALE) has been employed to grow InAs and InxGa1−xAs (0<x<0.43). The ALE of InAs, for example, proceeds by the deposition of a single layer of In followed by the deposition of a single layer of As. This cycle is repeated until the desired thickness is achieved. The column III and column V species are physically separated and thus the gas phase reaction between triethylindium and AsH3 is greatly reduced. This leads to improved incorporation of indium in the solid and improved compositional uniformity across the substrate. A self-limiting mechanism has been found which controls the thickness deposited per cycle to about one monolayer independent of the column III flux.
Ge-Si layered structures: Artificial crystals and complex cell ordered superlattices
Authors: Bevk J. , Mannaerts J. P. , Feldman L. C. , Davidson B. A. , Ourmazd A.
Published: July 2002

We report the first successful synthesis of ordered GeSi superlattices grown on (001) Si substrates by molecular beam epitaxy. Two types of structures were prepared and characterized: superlattices with one-dimensional periodicity of one unit cell (GeGeSiSi...) and complex cell superlattices made up of sublayers of pure Si and alternating bilayers of Ge and Si. In the first case, the artificial stacking in the [001] direction results in a vertical array of alternating Ge and Si monolayers parallel to the (110) or (11̄0) planes. In spite of the lattice mismatch of 4.2%, Rutherford backscattering and channeling experiments indicate high quality crystallinity in both types of structures. Long-range order is deduced from the electron diffraction patterns that exhibit characteristic superlattice reflections and from high resolution lattice imaging. The precise deposition control on the scale of a fraction of a monolayer should allow band structure engineering in this and in other related systems and in turn tailoring of the transport and optical properties over a wide range.
Peroxypolytungstic acids: A new inorganic resist material
Authors: Okamoto Hiroshi , Iwayanagi Takao , Mochiji Kozo , Umezaki Hiroshi , Kudo Tetsuichi
Published: July 2002

Recently reported amorphous polytungstic acids containing peroxo groups are found to provide a new inorganic resist. A homogeneous resist film can be formed easily with the spin coating method. This film is made insoluble in water by deep ultraviolet, x ray, and electron beam irradiation. The oxygen reactive ion etching (O2 RIE) durability is found to be high enough that a bilayer resist scheme employing this resist as a top imaging layer gives a high resolution pattern (line and space: 0.38 μm). The mechanism for the radiation induced reaction is also discussed.
Microwave equivalent circuit representation of rectangular dielectric waveguides
Authors: Dagli N. , Fonstad C. G.
Published: July 2002

Using a mode matching technique, a microwave equivalent circuit which incorporates contributions from both guided and continuum spectra has been developed to model rectangular dielectric waveguides. The equivalent circuit is modular and can be applied to complex structures. Accurate results are obtained with limited computational effort.
23.6% efficient low resistivity silicon concentrator solar cell
Authors: Green M. A. , Taouk M. , Blakers A. W. , Narayanan S. , Zhao Jianhua , Campbell P.
Published: July 2002

Significant improvements are reported in the energy conversion efficiency of low resistivity silicon solar cells when measured under concentrated sunlight. These improvements result primarily from increased short-circuit current density due to the use of a microgrooved cell structure with obliquely transversing metallization fingers. Peak efficiencies are 23.6% at 100 suns concentration with values up to 22.7% maintained at 273 suns concentration.
Impact ionization coefficients in In0.2Ga0.8As/GaAs strained-layer superlattices
Authors: Bulman G. E. , Zipperian T. E. , Dawson L. R.
Published: July 2002

The impact ionization coefficients for electrons and holes have been measured in In0.2Ga0.8As/GaAs strained-layer superlattices (SLS’s) for transport perpendicular to the superlattice. The pure electron and hole initiated primary photocurrents were produced in p+n mesa photodiodes having In0.1Ga0.9As alloy photon absorption regions and an SLS active region carrier concentration of 7.4×1015 cm−3. The impact ionization coefficient for electrons is found to be larger than for holes with a ratio that varies from 1.8 at 2.7×105 V/cm to 1.4 at 3.8×105 V/cm.
Metal halide saturable absorbers at 248 nm
Authors: Kaplan R. D. , Gibson R. B.
Published: July 2002

Optical transmissions of CsI and NaBr vapor are measured at 248 nm. Absorption of these representative alkali metal halides saturates at 10–100 mJ cm−2 fluence. Ratio of small-signal to saturated absorption coefficients is of order 10.
Involvement of oxygen-vacancy defects in enhancing oxygen diffusion in silicon
Authors: Oates A. S. , Newman R. C.
Published: July 2002

We have proposed previously that the extremely high rate of single diffusion jumps of oxygen atoms in silicon during electron irradiation of crystals above 300 °C is due to the sequential trapping and detrapping of vacancies. In support of this proposal we now demonstrate thermal dissociation of up to 75% of oxygen-vacancy centers by monitoring their destruction in irradiated and annealed crystals. An important new step is the calibration of the strength of the infrared 830 cm−1 absorption band via a novel procedure to give the concentration of oxygen-vacancy complexes in crystals.
Reverse-bias current-electric field characteristics of amorphous silicon films with blocking layers: Thickness dependence
Authors: Kakinuma H. , Nishikawa S. , Watanabe T. , Nihei K.
Published: July 2002

Static current-electric field (J-F) characteristics of p-type hydrogenated amorphous Si (a-Si:H)/intrinsic (i) a-Si:H/amorphous Si1−xCx structures under reverse-biased conditions have been studied. These structures are widely used for xerographic photoreceptors. The main variable was the thickness of the i layer (di), ranging from 2.5 to 27 μm. The J-F characteristics exhibited three distinct regions, i.e., an Ohmic region, a differential negative resistance (DNR) region, and a superlinear region with increasing F. The DNR occurred approximately at the same F (∼104 V/cm), and the J values in the other two regions proved systematically but differently dependent on the i-layer thickness. The J value at a low F value in the Ohmic region decreased rapidly below the di value of 10 μm, while for di above 10 μm the J value was constant. In the superlinear region, J for a constant F increased proportionally to di. The origins of these thickness dependences are discussed.
Electron beam induced current and cathodoluminescence study of the recombination activity of stacking faults and hillocks in hydride vapor phase epitaxy InP
Authors: Attolini G. , Frigeri C. , Pelosi C. , Salviati G.
Published: July 2002

Cathodoluminescence and electron beam induced current modes in the scanning electron microscope have been employed to study the recombination behavior of stacking faults and surrounding hillocks in undoped InP homoepitaxies grown by hydride vapor phase epitaxy. Stacking faults exhibited nonradiative recombination activity. The largest hillocks with {111} type outer surfaces showed enhanced radiative recombination on two opposite sides and no recombination on the other two, most probably because of the different incorporation of the unintentional dopant. The greater influence that the largest hillocks have, compared with the crystallographic defects, in limiting the electrical but not the optoelectronic performances of the homoepitaxies, is pointed out.
Chemical beam epitaxial growth of extremely high quality InGaAs on InP
Authors: Tsang W. T. , Dayem A. H. , Chiu T. H. , Cunningham J. E. , Schubert E. F. , Ditzenberger J. A. , Shah J. , Zyskind J. L. , Tabatabaie N.
Published: July 2002

Full widths at half-maximum intensity of the (004) Bragg reflecton peak as small as 24 arcs are obtained from InGaAs epilayers 4–6 μm thick. Such linewidth is the narrowest reported thus far for an InGaAs epilayer grown by any vapor phase technique reported in literature. Such extreme compositon uniformity is also supported by results from Auger depth profiles and 2 K photoluminescence measurements. Very intense efficient luminescence peaks due to excitonic transitions with linewidths (FWHM) as narrow as 1.2 meV are obtained. This again represents the narrowest linewidth ever reported for InGaAs grown by any technique. In fact, such a linewidth represents the narrowest linewidth ever measured for any alloy semiconductor. Further, the photoluminescence spectra reveal the donor-to-acceptor pair recombination is nearly absent. This indicates that the InGaAs is of very high purity. Hall measurements of 2–5-μm-thick epilayers grown directly on InP substrates have mobilities of 10 000–12 000 and 40 000–57 000 cm2/V s at 300 and 77 K with n=5×1014–5×1015 cm−3. These values are among the highest of all the results for InGaAs grown by other techniques.
Depth distributions of hydrogen-implanted and annealed silicon
Authors: Wilson R. G.
Published: July 2002

We have measured the redistribution of hydrogen as a function of annealing temperature in (100) and (111) Si implanted at 250 keV to a fluence of 1×1016 cm−2. The hydrogen profiles were measured using secondary ion mass spectrometry. Hydrogen (1H or 2H) begins to redistribute in hydrogen-implantation-damaged silicon between 300 and 325 °C, moving toward the surface through the implantation-damaged region at a density above 1018 cm−3. The implanted hydrogen begins to diffuse deeper into the undamaged bulk silicon at about 200 °C, but at densities below 1017 cm−3. The initial redistribution of hydrogen toward the surface is shown not to be associated with the regrowth of damage. A second phase of hydrogen redistribution, in which the density of the hydrogen distribution decreases, begins at about 550 °C, which is the temperature of the beginning of regrowth of damage. The density of the implanted hydrogen has decreased below∼1016 cm−3 by 800 °C, for initial implanted hydrogen densities of 1021 cm−3 or less. We also report range and profile shape factors for 1H and 2H atom depth distributions implanted into silicon for a few cases of ion energy and fluence.
Experimental measurement of a high-field dipole in GaAs field-effect transistors
Authors: Abeles J. H. , Leheny R. F. , Chang G. K. , Allen S. J.
Published: July 2002

GaAs short channel metal-semiconductor field-effect transistor models predict the formation of a high-field dipole layer with current saturation. In this work, the formation of such a dipole at the onset of current saturation is experimentally verified through measurement of the high-frequency conductivity of the channel. The complex conductivity and its dependence on frequency are analyzed to yield the capacitance of the high-field domain and its dependence on source-drain voltage. The corresponding peak electric field in the domain is ∼1.5×105 V/cm under current saturation conditions. The implications of the formation of such a domain on the speed of response of these devices are discussed.
Submicron silicon powder production in an aerosol reactor
Authors: Wu Jin Jwang , Flagan Richard C. , Gregory Otto J.
Published: July 2002

Powder synthesis by thermally induced vapor phase reactions is described. The powder generated by this technique consists of spherical, nonagglomerated particles of high purity. The particles are uniform in size, in the 0.1–0.2 μm size range. Most of the particles are crystalline spheres. A small fraction of the spheres are amorphous. Chain agglomerates account for less than 1% of the spherules.
Narrow spectral linewidth semiconductor optical-fiber ring laser
Authors: Tai Shuichi , Kojima Keisuke , Noda Susumu , Kyuma Kazuo , Hamanaka Koichi , Nakayama Takashi
Published: July 2002

A semiconductor optical-fiber ring laser was constructed using an AlGaAs/GaAs multiple quantum well laser diode as a gain medium. The single-mode oscillation was demonstrated and the measured spectral linewidth was less than 45 kHz. This is consistent with a theoretical calculation of its linewidth.
Modification of the scanning laser acoustic microscope for holographic and tomographic imaging
Authors: Lee Hua , Ricci Carlos
Published: July 2002

In this letter, we report the modification of the scanning laser acoustic microscope for the purpose of holographic and tomographic imaging. A very simple quadrature receiver is utilized to perform holographic recording of the resultant acoustic wave field. This quadrature detector mainly consists of a highpass-lowpass circuit pair and a multiplier, and is capable of generating accurate dual reference signals. In addition to the circuit design and frequency characteristics of the filter pair, we also provide the holographic image of a range finder reconstructed by using backward propagation method to demonstrate the resolution improvement due to this modification.