bluuebunny/crossref_metadata_2025 huggingface dataset:
Species and deposition angle dependence of ion beam induced densification of germanium selenide films
Authors: Venkatesan T. , Wilkens B. J.
Published: February 2003

The ion beam induced densification of obliquely deposited germanium selenide films shows strong dependence on the irradiating species and the deposition angle of the film. For a film deposited at 75° the Ar+ and Ne+ irradiations follow the simple statistics to be expected if each ion resulted in a compressed cylinder along the ion’s path. The He+ and H+ irradiations do not produce densification that follows similar statistics, indicating a strong nonlinearity of the irradiation phenomenon with respect to the energy deposited by the ions. The energy density in the track of an ion seems to be the relevant parameter rather than the total deposited energy. Films deposited at larger angles densify at lower ion doses. This can be understood if the low density of the as-deposited films depends on two types of voids, enclosed and canyonlike. Based on electron microscope pictures we propose that the films deposited at larger angles are dominated by canyonlike voids (which are easier to fill in by irradiation) whereas films deposited at smaller angles contain more of enclosed voids (which are harder to fill in by irradiation).
Diffusivity of oxygen in silicon at the donor formation temperature
Authors: Stavola M. , Patel J. R. , Kimerling L. C. , Freeland P. E.
Published: February 2003

We present data on oxygen diffusivity in silicon for the temperature range 270–400 °C. The diffusivity is determined from the recovery kinetics of a stress induced dichroism in the 9-μm oxygen infrared absorption band. We combine our data for well dispersed oxygen (i.e., crystals heat treated at 1350 °C for 20 h), with Mikkelsen’s recent mass transport work at higher temperature to obtain the diffusivity, D=0.17 exp (−2.54/kT), for the range 330–1240 °C. We have also found that the oxygen atomic hopping times can be as much as 100 times faster in crystals that have not received the 1350 °C heat treatment.
Investigation of Sn-doped GaAs epilayers grown by low pressure metal-organic chemical vapor deposition
Authors: Lee M. K. , Chang C. Y. , Su Y. K.
Published: February 2003

Tetraethyltin was used as a source of Sn dopant in homoepitaxial GaAs films grown from triethylgallium and arsine by low pressure metal-organic chemical vapor deposition. Epitaxial crystallinity was examined by using the x-ray back reflection Laue method. The carrier concentration is uniform in the Sn-doped epilayers and the transition region can be controlled to within 0.2 μm. The current-voltage characteristics were also examined. The accumulation of Sn on the surface of the epilayer was observed by Auger electron spectroscopy.
Secondary electron emission from uranium surfaces due to bombardment by high-energy ions
Authors: Chen Hao-Lin , Solarz Richard , Erbert Gaylen
Published: February 2003

The secondary emission of electrons from uranium surfaces was studied as a function of energy and type of the bombarding ions in the range 1.0–5.0 keV. The value of the secondary electron yield (i.e., the number of electrons ejected from a surface per impinging ion) was found to increase linearly with increasing ion energy and to scale roughly as the inverse square root of the mass of impinging ions.
Dynamic and noise properties of multiple quantum well injection lasers
Authors: Lindström C. , Scifres D. R. , Burnham R. D.
Published: February 2003

The fast pulse response and the dc noise spectra of multiple quantum well lasers grown by metalorganic chemical vapor deposition and with different stripe widths are reported. A best rise time of 100 ps corresponding to a modulation bandwidth of ∼3.6 GHz, was obtained. The dc noise spectra showed a damped shot noise resonance at a high frequency (∼3.0 GHz). The improvement in pulse and noise performances of these lasers compared to conventional double heterostructure lasers is explained with the small active volume and the high charge densities present in quantum well lasers.
Low dose depth distribution of recoil implanted atoms
Authors: Falcone G. , Oliva A.
Published: February 2003

Recoil implantation of atoms from a layer deposited on a substrate is described in terms both of the linear cascade theory and of the continuous slowing down approximation. The model is valid within the limit of low incident ion doses and for layer thicknesses large enough to contain the main part of the deposited energy. Results are compared to experimental data with satisfactory agreement. Ad hoc experiments can give information concerning the interactions of atoms colliding at low energy.
Optical absorption spectra of surface or interface states in hydrogenated amorphous silicon
Authors: Jackson W. B. , Biegelsen D. K. , Nemanich R. J. , Knights J. C.
Published: February 2003

The optical absorption of doped and undoped hydrogenated amorphous silicon (a-Si:H) films ranging from 5 nm to 10 μm was measured using photothermal deflection spectroscopy. The absorption spectra show that there is a high defect layer associated with the surface or interface of the film. From comparison of defect absorption and dangling bond spin densities, it is found that a-Si:H films which have ∼1015 bulk defects/cm3 exhibit surface or interface layers with ∼1012 dangling bonds/cm2.
Structural difference rule for amorphous alloy formation by ion mixing
Authors: Liu Bai-Xin , Johnson W. L. , Nicolet M-A. , Lau S. S.
Published: February 2003

We formulate a rule which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results we have obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.
Growth of single crystal epitaxial silicides on silicon by the use of template layers
Authors: Tung R. T. , Gibson J. M. , Poate J. M.
Published: February 2003

A novel crystal growth technique for silicide epitaxy is presented which utilizes thin silicide (<60 Å) template layers to pin the subsequent growth under ultrahigh vacuum conditions. Single crystal NiSi2 films can be grown with either type A or type B orientations on Si (111). Continuous single crystal NiSi2 is grown on Si (100) with a flat interface and uniform thickness. Thick CoSi2 can be grown on Si (111) by a similar process using thicker templates.
Instabilities in superconducting tunnel junctions in different thermal environments
Authors: Adler J. G. , Will T. A.
Published: February 2003

Instabilities in superconducting tunnel junctions have been studied in three environments: low pressure He gas, normal liquid He I, and superfluid He II. It is demonstrated that the effect arises at a bias voltage V0 where junction dissipation is sufficient to drive a region of the electrode(s) normal. The transition is accompanied by a small excess current, which is due to the appearance of electrode resistance and junction heating. For Pb electrode junctions immersed in liquid He the critical junction dissipation marks the outset of film boiling, which shows up as excessive noise in the tunneling curves. This critical heat flux, ≂1 W/cm2 at 4.2 K, limits the useful energy range for tunneling spectroscopy and leads to catastrophic burnout of high density Josephson arrays.
1.5–1.6-μm Ga0.47In0.53As/Al0.48In0.52As multiquantum well lasers grown by molecular beam epitaxy
Authors: Temkin H. , Alavi K. , Wagner W. R. , Pearsall T. P. , Cho A. Y.
Published: February 2003

The first successful preparation of optically pumped and current injection Ga0.47In0.53As/Al0.48 In0.42As multiquantum well lasers is reported. These devices, operating at room temperature in the 1.5–1.6-μm range, have been prepared by molecular beam epitaxy with well thicknesses as low as 80–90 Å and barrier thicknesses as low as 30 Å. In the broad area devices with a total active layer thickness of 0.14 μm we have observed threshold current density as low as 2.4 kA/cm2.
Short cavity InGaAsP/InP lasers with dielectric mirrors
Authors: Koren U. , Rav-Noy Z. , Hasson A. , Chen T. R. , Yu K. L. , Chiu L. C. , Margalit S. , Yariv A.
Published: February 2003

Short cavity length (38 μm) lasers have been fabricated using a recently developed microcleavage technique. SiO2-amorphous Si multilayer coatings have been evaported on the lasers to obtain high reflectivity mirrors. The lasers have current thresholds as low as 3.8 mA with 85% reflecting front mirror and high reflectivity rear mirror and 2.9 mA with two high reflectivity mirrors. Single longitudinal mode operation is observed over a wide range of driving currents and temperatures.
New large optical cavity laser with distributed active layers
Authors: Tsang W. T. , Olsson N. A.
Published: February 2003

A new semiconductor current injection laser having multiple active layers distributed within a large optical cavity (LOC) waveguide is shown to operate as an efficient, low-threshold, high-peak power laser diode. The use of distributed active layers in LOC laser structure leads to improved efficiency in utilizing the injected carriers when compared to the conventional single active layer LOC laser structure.
High-resolution submillimeter-wave radiometry of supersonic flow
Authors: Dionne G. F. , Weiss J. A. , Fitzgerald J. F. , Fetterman H. R. , Litvak M. M.
Published: February 2003

The recent development of a high-resolution submillimeter-wave heterodyne radiometer has made possible the first measurements of H2O molecule rotational line excitation temperatures and detailed profiles in supersonic flow. Absorption signals were measured across the flow for the 211←202 (752 GHz) para-H2O rotational transition against a hot background. These signals decrease downstream owing to the volume expansion of the gas away from the sonic nozzle exit in the high-vacuum chamber. Radiative transfer calculations based on the large-velocity-gradient approximation and multilevel statistical equilibrium agree with these results and with the measured spectral line shapes. The data reveal nearly isentropic gas expansion and cooling. These studies have shown that submillimeter-wave heterodyne radiometry can be useful for remote sensing of supersonic flow with low mass flux, provided the signal transmission is through a dry or thin atmosphere.
Electroabsorption by Stark effect on room-temperature excitons in GaAs/GaAlAs multiple quantum well structures
Authors: Chemla D. S. , Damen T. C. , Miller D. A. B. , Gossard A. C. , Wiegmann W.
Published: February 2003

We report the first observation of electroabsorption in GaAs/GaAlAs multiple quantum well structures. We have been able to induce Stark shifts for room-temperature exciton resonances of ∼10 meV for applied field ∼1.6×104 V/cm in a sample with 96-Å GaAs layers, giving large changes in optical absorption (e.g., a factor of 5 or ∼4×103 cm−1 increase). This should permit optical modulators with micron path lengths and potentially very fast operation.
High resolution acoustic microscopy in superfluid helium
Authors: Foster J. S. , Rugar D.
Published: February 2003

An acoustic microscope has been developed which utilizes liquid helium at temperatures less than 0.2 K as the coupling medium. At the operating frequency of 4.2 GHz, the acoustic attenuation of the helium is negligible and the acoustic wavelength is 570 Å. Micrographs of a silicon integrated circuit are presented which demonstrate the good signal-to-noise ratio of the imaging and resolution better than 500 Å.
Integrated arrays of 1.3-μm buried-crescent lasers
Authors: Temkin H. , Logan R. A. , van der Ziel J. P.
Published: February 2003

Arrays of five InGaAsP buried-cresent large-optical-cavity lasers operating at 1.3 μm are described. The monolithically integrated arrays have threshold as low as 60 mA, external quantum efficiencies η≊55%, and operate in the fundamental transverse mode up to 50 mW per facet at room temperature. Despite the very close center to center spacing of 8 μm, no electrical or optical interaction between lasers has been observed.
Time and space resolved vacuum-ultraviolet spectroscopy of an argon gas-puff Z pinch
Authors: Marrs R. E. , Dietrich D. D. , Fortner R. J. , Levine M. A. , Price D. F. , Stewart R. E. , Young B. K. F.
Published: February 2003

Time and radially resolved vacuum-ultraviolet spectra from an argon gas-puff Z pinch have been obtained using a grazing incidence spectrometer with gated microchannel plates curved to the Rowland circle. Most of the 50–300-Å radiation is emitted from a dense core (r≊0.4 mm, ne≳1019 cm−3, Te≊150 eV) which forms when the plasma assembles on the axis.
Kinetics of self-interstitials generated at the Si/SiO2 interface
Authors: Taniguchi K. , Antoniadis D. A. , Matsushita Y.
Published: February 2003

The kinetics of self-interstitials in silicon were investigated by monitoring oxidation stacking faults on backside oxidized silicon wafers in the temperature range 1100–1200 °C in a wet O2 ambient. The diffusion coefficient and thermal equilibrium concentration of self-interstitials were obtained by optimizing model parameters to match calculated and experimental observations of growth of oxidation stacking faults at the front surface of silicon wafers protected from oxidation by a composite SiO2/poly Si/Si3N4 film.
Optical transmission at 3.39 μm during pulsed laser annealing of silicon
Authors: Lyon S. A. , Chen Y. H. , Lin J. F. , Worlock J. M.
Published: February 2003

We have measured the infrared transmission at 3.39 μm, for bulk Si and Si:Au and for silicon on sapphire during pulsed laser annealing. The transmission drops sharply and remains near zero for approximately 100 ns in all samples. The infrared transmission in bulk Si requires milliseconds to completely recover. We attribute this effect to a thermally induced change in the index of refraction of the silicon and associated tuning of the Fabry–Perot cavity formed by the faces of the Si wafers. Our experiments yield no evidence for an optical gap as expected for a Bose condensed exciton phase, and thus are supportive of the thermal melting model of laser annealing.
Diffusion of arsenic in silicon: Validity of the percolation model
Authors: Mathiot D. , Pfister J. C.
Published: February 2003

It is shown that the percolation model previously proposed to explain the high concentration diffusion of phosphorus in Si holds also in the case of arsenic. Suitable numerical values of the parameters are derived, and it is shown that the model allows the simulation of arsenic diffusion in a wide range of experimental conditions.
Optimization of electrically excited XeF(C→A) laser performance
Authors: Nighan W. L. , Nachshon Y. , Tittel F. K. , Wilson W. L.
Published: February 2003

Significantly improved output power and spectral characteristics have been obtained for an electron beam-pumped XeF(C→A) laser by selective tailoring of kinetic processes. Using a high pressure Ar-Xe mixture containing both NF3 and F2 in combination, a laser pulse energy density of 0.1 J/l was obtained corresponding to an electrical-optical conversion efficiency of approximately 0.1%. Modeling of kinetic processes and analysis of laser spectral output confirm that the improved laser efficiency is primarily a consequence of reduced absorption by Xe-related excited species.
Pearson distributions for ion ranges
Authors: Winterbon K. B.
Published: February 2003

Type IV Pearson distributions have been used by several groups to represent ion implantation range distributions. It is pointed out here that these distributions are inappropriate, and type VI (or possibly type V) distributions should be used instead. It must be remembered that these distributions are only approximations to the true range distribution.
Simple method for the spectral control of merocyanine photodiodes
Authors: Iriyama Keiji , Yoshiura Masahiko
Published: February 2003

A simple method for the spectral control of merocyanine photovoltaic cell (Al merocyanine film/Ag) has been developed. The spectral control was achieved by soaking in an Al dye cell in which an aqueous solution was placed ( pH 7.0) for forming a new absorption peak around 600 nm, probably due to J aggregation. Ag was evaporated on the dye film thus treated and then dried to form the counterelectrode as an ohmic contact. The merocyanine photodiode thus prepared has exhibited a power conversion efficiency about 3.3% under the 600-nm monochromatic light illumination (0.09 mW/cm2).
Determination of the minimum x-ray flux for effective preionization of an XeCl laser
Authors: Tallman C. R. , Bigio Irving J.
Published: February 2003

We have varied the x-ray flux used to preionize a discharge-pumped XeCl laser. With a laser gas pressure of 4 atm, as little as 10−4 rad (∼7×10−9 J/cm2) of 20–40-kV x rays was found to be sufficient for effectively stabilizing the discharge. The discharge was highly uniform and the laser yielded ∼5 J/l specific energy. This represented a 35% improvement over the performance of the same laser with UV preionization.
Nonlinear optical studies of picosecond relaxation times of electrons in n-GaAs and n-GaSb
Authors: Kash Kathleen , Wolff P. A. , Bonner W. A.
Published: February 2003

The third order nonlinear optical susceptibility of free carriers has been studied in n-GaAs and n-GaSb as a function of the frequency difference δω between two Q-switched CO2 laser beams for different lattice temperatures. The nonlinear response of the electron gas results from the modulation of the carrier mass as the kinetic energy and electron distribution are driven at frequency δω. This modulation arises both from the nonparabolicity of the light mass Γ minimum and, at high temperatures, from the transfer of electrons between the Γ and the heavier mass L minima. The frequency dependence of the response yields the intervalley and energy relaxation times.
Realization of an InSb bistable device as an optical a
n
d gate and its use to measure carrier recombination times
Authors: Seaton C. T. , Smith S. D. , Tooley F. A. P. , Prise M. E. , Taghizadeh M. R.
Published: February 2003

We report the novel operation of a natural reflectivity InSb bistable resonator at 77 K, pumped with a cw CO laser at 1819 cm−1, as a single pulse detector with definite threshold energy and as an optical AND gate. The two switching pulses for the AND gate logic operation are 30-ps single, switched-out pulses from a mode-locked neodymium: yttrium aluminum garnet (Nd:YAG) laser. Introduction of a variable time delay between the logic pulses provides a unique technique for measurement of the photogenerated carrier lifetime and yields a recombination time ∼90 ns for a cw CO holding intensity ∼80 W/cm2.
High power single mode InGaAsP lasers fabricated by single step liquid phase epitaxy
Authors: Oron M. , Tamari N.
Published: February 2003

Lasing properties of an InGaAsP (λ=1.3 μm) crescent-shaped buried heterostructure laser are presented. The structure was grown by single step liquid phase epitaxy on a mesa substrate. High output power in pulsed operation (150 mW/facet) and high external differential quantum efficiency (60%) are realized in this structure even though there is no special layer for current blocking. Fundamental mode operation up to a power level of 30 mW/facet is found. These characteristics are attributed to the effect of the mesa on current flow and they demonstrate the importance of substrate topography on laser performance.
Impurity induced disordering of strained GaP-GaAs1−xPx(x∼0.6) superlattices
Authors: Camras M. D. , Holonyak N. , Hess K. , Ludowise M. J. , Dietze W. T. , Lewis C. R.
Published: February 2003

Data are presented showing that Zn diffusion into a strained GaP-GaAs1−xPx  (x∼0.6) superlattice (40 periods, Lz∼120 Å GaAsP quantum wells, LB∼120 Å GaP barriers) enhances the interdiffusion of As and P (anion interchange) at the heteriointerfaces, thus resulting in disordered indirect gap bulk crystal GaAs1−xPx (x∼0.8).
Comparison of band-gap shrinkage observed in luminescence from n+-Si with that from transport and optical absorption measurements
Authors: Dumke W. P.
Published: February 2003

The luminescence data of Schmid, Thewalt, and Dumke on heavily doped n-type Si have been analyzed and compared with the published band-gap shrinkage results of infrared absorption measurements and of transport measurements in bipolar transistors with heavily doped bases. The gap shrinkage observed in luminescence behaves similarly to that observed in transport. The luminescence results are consistent with a density of filled states characteristic of a parabolic conduction band. It is argued that the comparison of the results of luminescence, absorption, and transport measurements indicates a nonrigid gap shift.
X-ray photoelectron spectroscopic study of the oxide removal mechanism of GaAs (100) molecular beam epitaxial substrates in i
n s
i
t
u heating
Authors: Vasquez R. P. , Lewis B. F. , Grunthaner F. J.
Published: February 2003

A standard cleaning procedure for GaAs (100) molecular beam epitaxial (MBE) substrates is a chemical treatment with a solution of H2SO4/H2O2/H2O, followed by in situ heating prior to MBE growth. X-ray photoelectron spectroscopic (XPS) studies of the surface following the chemical treatment show that the oxidized As is primarily As+5. Upon heating to low temperatures (<350 °C) the As+5 oxidizes the substrate to form Ga2O3 and elemental As (As0), and the As+5 is reduced to As+3 in the process. At higher temperatures (500 °C), the As+3 and As0 desorb, while the Ga+3 begins desorbing at ∼600 °C.
Photon-assisted tunneling at 246 and 604 GHz in small-area superconducting tunnel junctions
Authors: Habbal F. , Danchi W. C. , Tinkham M.
Published: February 2003

We have observed photon-assisted tunneling effects at 246 and 604 GHz in small-area superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal metal (SIN) superconducting junctions. We find excellent agreement with the Tien–Gordon theory, and infer that the responsivity of SIN junctions approaches the quantum limit at low temperatures for photon energies less than 2Δ.
H+2 ion-implantation effect in vacuum-evaporated permalloy films
Authors: Imura R. , Sugita Y.
Published: February 2003

This letter reports that the magnetoresistance ratio Δ ρ/ρ increases and the coercive force Hc reduces in vacuum-evaporated permalloy films by implanting H+2 ions. The increase in Δ ρ/ρ is due to a decrease in the resistivity ρ, and the magnetoresistance coefficient Δ ρ remains almost unchanged. By implanting H+2 ions ρ becomes nearly equal to that of the permalloy bulk in the film thickness range of more than 3000 Å. The coercive force Hc remarkably decreases to the small value in the thinner films range. The grain size of ion-implanted films is about the same as that of non-ion-implanted films. This shows that the decrease in ρ is not due to the grain growth mechanism as in annealed films but may be due to some mechanism of the grain boundary change caused by implanted ions. The mechanism of decrease in ρ and Hc remains to be clarified.
Plasma ion temperature measurements via charge exchange recombination radiation
Authors: Fonck R. J. , Goldston R. J. , Kaita R. , Post D. E.
Published: February 2003

Spatially and temporally resolved plasma ion temperatures can be determined by measuring the Doppler-broadened line profiles of transitions excited by charge-exchange recombination reactions between fast hydrogen atoms and fully ionized low-Z ions. Plasma rotation velocity profiles can also be obtained. A sample result from the PDX tokamak using He+ radiation is presented, and expected line intensities for model cases for PDX and TFTR are calculated.
Picosecond correlation measurements of indium phosphide photoconductors
Authors: Downey P. M. , Auston D. H. , Smith P. R.
Published: February 2003

The response times of InP photoconductors under picosecond optical illumination are observed to differ widely depending on whether the electrical bias is dc or a short pulse. The use a pulsed bias gives a slower response (>100 ps) which is more characteristic of the intrinsic material properties, than a dc bias which gives a very fast (<15 ps) response and can be attributed to imperfect contacts.
Growth of CdTe films on sapphire by molecular beam epitaxy
Authors: Myers T. H. , Lo Yawcheng , Bicknell R. N. , Schetzina J. F.
Published: February 2003

Results of initial attempts to grow cubic-phase CdTe films on sapphire by molecular beam epitaxy are reported. Depositions have been completed on (11̄02) R-plane, (12̄10) A-plane, and (0001) basal plane substrates. Substrate temperatures in the range 260–350 °C were employed along with deposition rates of 1.5–7.5 Å/s. Depositions on (11̄02) sapphire generally produced films containing some elements of the hexagonal phase, as disclosed by x-ray diffraction and UV reflectance measurements. Sharp cubic-phase epitaxy was obtained for thick (∼5 μm) CdTe films grown on (12̄10) and (0001) sapphire substrates. The epitaxial films are smooth and mirrorlike in appearance. Nomarski micrographs show a featureless CdTe surface.
Characteristics of modulation-doped AlxGa1−xAl/GaAs field-effect transistors: Effect of donor-electron separation
Authors: Drummond T. J. , Fischer R. , Su S. L. , Lyons W. G. , Morkoç H. , Lee K. , Shur M. S.
Published: February 2003

The dc characteristics of modulation-doped AlxGa1−xAs/GaAs field-effect transistors have been studied experimentally and theoretically to determine the effect of the thickness of the undoped AlxGa1−xAs spacer layer commonly left at the heterointerface. Increasing the thickness of the spacer layer decreases charge transfer and increases mobility. Current transport in short channel transistors, however, is limited by the electron saturation velocity which is independent of the spacer thickness. Due to increased charge transfer, decreasing the spacer thickness from 100 to 20 Å doubled the maximum saturation current and transconductance. This should allow faster switching speeds to be obtained. A maximum current of 24 mA was obtained for a gate width of 145 μm with a 40-Å spacer and a transconductance of 250–275 mS/mm was obtained for a device with a 20-Å spacer. Theoretical results indicate that intrinsic transconductances greater than 900 mS/mm are possible. Preliminary small-signal rf measurements indicate a maximum available gain of about 9 dB at 8 GHz.
Evaluation of aluminum-GaAs Schottky barriers using Norde’s modified current-voltage analysis
Authors: Schwartz G. P. , Gualtieri G. J.
Published: February 2003

Schottky barrier heights for aluminum-(100) GaAs diodes with and without an interfacial native oxide layer have been evaluated using Norde’s method of current-voltage analysis. Barrier heights determined by Norde’s method on sputter-annealed, oxide-free substrates are systematically lower (0.53–0.59 eV) than values determined by photoresponse measurements (0.78±0.03 eV). Anomalous structure in the form of a second minimum was observed in the Norde plots for unsputtered substrates on which a thin native oxide was present. The barrier heights obtained from the second minimum observed at high forward bias (∼0.75 V) were 0.90–0.95 eV, whereas photoresponse measurements indicated barriers of 1.00±0.01 eV.
Orientation effect of self-aligned source/drain planar GaAs Schottky barrier field-effect transistors
Authors: Yokoyama N. , Onodera H. , Ohnishi T. , Shibatomi A.
Published: February 2003

The effect of orientation on self-aligned source/drain planar GaAs Schottky barrier field-effect transistors (FET’s) has been investigated. The dependence of the threshold voltage of FET’s on gate length was measured for FET’s oriented in two perpendicular [110] directions. Both stress-enhanced lateral spread of implanted ions and lateral diffusion at the gate material/GaAs interface are proposed as possible mechanism to account for the orientation effect. The experiments indicate that the preferred direction for the self-aligned FET fabrication on a (100) substrate is [011̄].
Infrared to visible up-conversion using GaP light-emitting diodes
Authors: Eisfeld W. , Werling U. , Prettl W.
Published: February 2003

Electroluminescence excited by infrared radiation has been observed in GaP light-emitting diodes (LED’s) at low temperatures providing a new efficient method to convert infrared radiation within a broad spectral range into visible light. Using 10.6-μm radiation of a CO2 laser an up-conversion quantum efficiency of 3.4×10−6 was found. If a low dark current photomultiplier is employed to detect the LED emission the dominant noise source is due to conversion of thermal background radiation yielding a noise equivalent power of NEP=1.6×10−9 W/Hz1/2.
Pulsed UV laser Raman spectroscopy of silane in a linear-flow chemical vapor deposition reactor
Authors: Breiland W. G. , Kushner M. J.
Published: February 2003

For the first time, spatially resolved relative concentrations of silane inside a chemical vapor deposition reactor have been measured with spontaneous Raman spectroscopy using the third harmonic of a Q-switched neodymium:yttrium aluminum garnet laser. Concentration profiles were obtained under both atmospheric and low total pressure conditions. Considerable depletion of silane in the gas phase was observed.
Selective enhancement of the 251-μm line in an optically pumped CH3OH laser
Authors: Sakurai Toshio
Published: February 2003

To obtain a high output power on the 251-μm line of a CH3OH laser, four types of far-infrared output mirror are examined. It is found that the capacitive aluminium-mesh mirror of the Danielewicz type, which is fabricated by conventional vacuum deposition techniques in the present work, selectively extracts an output power of 18 mW from a 25-W pump. Also, exact assignment of the line is achieved by tuning the far-infrared cavity using the mirror.
Evidence of stress-mediated Hg migration in Hg1−xCdxTe
Authors: Raccah P. M. , Lee U. , Silberman J. A. , Spicer W. E. , Wilson J. A.
Published: February 2003

Photoemission results from some 〈110〉 cleaved surfaces of Hg1−xCdxTe indicate that the Fermi level is pinned suggesting that while the bulk of the material is p type the area stressed during cleavage has been converted to n type. Electrolyte electroreflectance (EER) measurement confirmed the n-type character of the cleaved surface and showed that the alloy composition x at the surface, after cleavage, is high (x=0.22) compared to the bulk value (x=0.185). The high x value associated with the n character indicates that under stress the Hg migrates, at least partially, via the formation of donor defects. The defect density is reflected in the EER linewidth.
Plasma parameter estimation from rf impedance measurements in a dry etching system
Authors: van Roosmalen A. J.
Published: February 2003

The rf impedance of a dry etching system excited at 13.56 MHz is calculated from the settings of the matching network between the generator and the reactor. It is demonstrated that fundamental plasma parameters, which are useful in the evaluation of dry etching techniques, can be derived from these measurements. For an oxygen discharge at 27 Pa and 350 W m−2 the following parameter values are obtained: maximum ion bombardment energy 76 V, electron density in the glow 5×1014 m−3, ion flux density on the substrates 0.08 A m−2.
New experimental evidence of surface ripples on gallium arsenide in laser annealing
Authors: Tsukada Noriaki , Sugata Sumio , Mita Yoh
Published: February 2003

This letter presents new experimental evidence of periodic structure or ripples which occur on the surface of crystalline or ion-implanted gallium arsenide in laser annealing. A new kind of ripple, whose direction does not depend on the electric field vector of the laser beam, appears for the larger angle of incidence between the laser beam direction and the surface normal. The variation in this ripple spacing with the incident angle of the laser beam to the surface normal is different from that for previously reported ripples, whose direction is always found to be almost perpendicular to the electric field vector for the linearly polarized laser beam. We suggest that the spacing for the new ripples can be interpreted from the reinforcement of the initially induced weak and straggling surface disturbances caused by the interference between the incident laser beam and succesively scattered waves.
Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN-coated sapphire substrates
Authors: Yoshida S. , Misawa S. , Gonda S.
Published: February 2003

The electrical and luminescent properties of the GaN epitaxial films grown on AlN-coated sapphire by reactive molecular beam epitaxy have been studied. The GaN films on AlN epitaxial films have larger Hall mobilities and show more intense cathodoluminescence peaks at a wavelength of 360 nm than those of the GaN films grown directly on sapphire, which suggests that the crystal qualities of GaN films are improved by use of AlN-coated sapphire as substrates. The lattice matching and small difference of the thermal expansion coefficients between GaN and AlN are considered to result in the improvements.
Diode laser threshold current density and lasing wavelength as functions of active region thickness
Authors: Streifer W. , Scifres D. R. , Burnham R. D.
Published: February 2003

Based on a simple model of the band-to-band absorption of a diode laser active region, we formulatean expression for modal gain as a function of pumping current. Using this result yields expressions for threshold current density and lasing photon energy which depend on device parameters including active region thickness, laser length, internal losses, facet reflectivity, etc.
Ultraviolet photodecomposition for metal deposition: Gas versus surface phase processes
Authors: Wood Thomas H. , White J. C. , Thacker B. A.
Published: February 2003

Photodecomposition of organometallic gases has been shown to be potentially useful for high resolution direct metal deposition. However, a number of problems, particularly the low writing rates, must first be solved. An understanding of the deposition mechanism is essential to this task. In particular, the decomposition must be shown to occur either in the gas phase or in the adsorbed layer. We show that this question can be resolved by the dependence of the writing rate on spot size. Measurements of the process show that the decomposition occurs in the gas phase. This result is shown to cause inhomogeneous deposition for exposures through masks with varying feature sizes, and effect will be important to future applications.
Confocal surface acoustic wave microscopy
Authors: Smith I. R. , Wickramasinghe H. K. , Farnell G. W. , Jen C. K.
Published: February 2003

When the scanning acoustic microscope is used in a defocussed mode to measure surface acoustic wave properties, circular surface wave fronts are generated on the specimen which propagate to a diffraction-limited focus. Thus, high resolution surface wave images are simply formed and a wide range of established nondestructive testing techniques become available to the acoustic microscope. Images obtained in the reflection mode are presented which demonstrate the unexpectedly high spatial resolution.
High resolution ion beam lithography at large gaps using stencil masks
Authors: Randall J. N. , Flanders D. C. , Economou N. P. , Donnelly J. P. , Bromley E. I.
Published: February 2003

High resolution masked ion beam lithography (MIBL) is demonstrated at large mask-to-sample gaps using two new types of membrane stencil masks. Single layer Si-rich silicon nitride (SiN) membranes and Si3N4-SiO2-Si3N4 (N-O-N) sandwich structure membranes are deposited by processes which allow the stress in the films to be adjusted. Transmission holes are reactive-ion etched entirely through the membranes. This type of stencil mask virtually eliminates mask-induced scattering. Lines and spaces of 160 nm have been exposed in 0.5-μm polymethylmethacrylate (PMMA) at gaps as large as 275 μm, using 100-keV protons. Some of the stencil mask limitations are overcome by multiple exposures. The results suggest that MIBL can be an extremely high resolution proximity printing technique.
Submicron multifilamentary high performance Nb3Sn produced by powder metallurgy processing of large powders
Authors: Otubo J. , Pourrahimi S. , Zhang H. , Thieme C. L. H. , Foner S.
Published: February 2003

Powder metallurgy processed submicron multifilamentary Nb3Sn superconducting wires were fabricated starting with 250–500-μm-diam powders. A multiple strand bundling procedure was used to simulate large scale production with actual areal reductions greater than 106 to achieve submicron fibers. Both external tin and tin core processing were successful. Typical Cu-36 wt.% Nb-Sn materials gave overall critical current densities of 8×104 A/cm2 at 12 T, 3×104 A/cm2 at 14 T, and 6×103 A/cm2 at 16 T. These results demonstrate that particle size and billet size can be scaled from earlier laboratory scale to large scale fabrication to produce high performance materials.
Electrically amplified optical recording in polymer films
Authors: Bosch M. A. , Good E. , Lemons R. A.
Published: February 2003

The laser power required to record high contrast marks in a polymer film can be reduced two orders of magnitude by depositing the film on a transparent conductor-photoconductor-conductor sandwich. The sensitivity of this medium is controlled by adjusting the voltage applied to the conductors. In the power limited regime, as little as 0.1 mW of laser power can increase the ohmic heating at the focus enough to produce symmetric micrometer size bubbles in the adjacent polymer film without damaging the photoconductor. However, due to the high dark resistivity of the photoconductor, the power dissipation in the unilluminated region is only ≊0.01 W/cm2.
Generation of high-power picosecond continuously tunable radiation between 215 and 245 nm by mixing of Raman and optical parametric light
Authors: Takagi Y. , Sumitani M. , Nakashima N. , O’Connor D. V. , Yoshihara K.
Published: February 2003

Upconversion by mixing of optical parametric light with the fourth harmonic of a neodymium:yttrium aluminum garnet (Nd:YAG) laser and fourth harmonic pumped H2 and N2 Raman light has been used to generate high-power picosecond continuously tunable UV light ranging from 215–245 nm with an energy of more than 100 μJ. The tunability is based on generation of optical parametric light with a range from 900 to 1400 nm.
Near-field and far-field patterns of phase-locked semiconductor laser arrays
Authors: Scifres D. R. , Streifer W. , Burnham R. D. , Paoli T. L. , Lindström C.
Published: February 2003

A gain-guided phase-locked semiconductor laser array has been observed to emit a single narrow lobed far-field radiation pattern up to 70 mW, at which power level it exhibits a distinct change. We show that this effect results from a new phase-locked mode attaining threshold; the original mode remains phase locked above this power level.
Interactions between H2 and N2 plasmas and a GaAs(100) surface: Chemical and electronic properties
Authors: Friedel P. , Gourrier S.
Published: February 2003

The existence and possible origin of surface states on GaAs surface exposed to an N2 plasma have been studied on surfaces cleaned by H2 plasma in a UHV system. The H2 plasma is shown to be very effective in reducing the C and N concentrations at the surface and to a lesser extent, the O concentration. A subsequent heating around 530 °C removes the remaining oxygen and gives a clean surface. The interaction of these clean surfaces with an N2 plasma shows a two-time constant behavior: (i) a rapid (5 s for our experimental conditions) dielectric (nitride) formation associated with an increase of the work function; (ii) a slow (∼100 s) decrease of the surface photovoltage and of As concentration at the surface. Comparison of n- and p-type samples seems to indicate that this is due to a reduction of the band bending depending on the final As concentration.
Substrate surface excitations and ionization of particles sputtered from GaAs
Authors: Šroubek Z.
Published: February 2003

The ionization probabilities of Ga, As, and Zn sputtered from GaAs by He+ and Ar+ ions at different primary ion energies and angles of incidence have been investigated. The data indicate that electronic excitations in the collision cascade are responsible for the ionization of particles sputtered from GaAs. In the ionization process the local atomic order is preserved.
Effect of gettering on leakage current in shallow junctions
Authors: Ghezzo M. , Gildenblat G. , Cohen S. S.
Published: February 2003

Shallow junctions in silicon, which have been subjected to a threshold adjust implant, show an increase of leakage current unless annealed at a high temperature. In very large scale integration technology, a high-temperature treatment is not desirable. We have found that a backside gettering treatment of the As and P implanted junctions allows the annealing temperature of threshold control implantation to be reduced from 1100 to 950 °C, while maintaining a low level of leakage current density.
Electronic properties of amorphous silicon selenium films
Authors: Wakim F. G. , Abo-Namous S. A. , Al-Jassar A. , Hassan M. A.
Published: February 2003

The presence of selenium in amorphous silicon films increases the optical gap from 1.25 to 1.8 eV. At the same time, the room-temperature resistivity increases by four orders of magnitude and thermal activation energy increases from 0.16 to 0.76 and 0.41 eV for the high and low-temperature regions, respectively.
Diffusion limited precipitation of oxygen in dislocation-free silicon
Authors: Binns M. J. , Brown W. P. , Wilkes J. G. , Newman R. C. , Livingston F. M. , Messoloras S. , Stewart R. J.
Published: February 2003

The kinetics of oxygen precipitation in silicon have been determined from measurements of the IR 9-μm absorption band (4.2 K) and we obtain the time constant τ0 for the exponential approach to equilibrium for several temperatures. The density N of precipitate particles was measured directly by chemical etching, and inferred from IR scattering and cold neutron scattering. We use our values of τ0 and N to calculate the diffusion coefficient of oxygen in bulk silicon. This is the first time that this procedure has been used, and we obtain D=0.02 exp(−2.42 eV/kT) cm2 s−1 in the temperature range 650–1050 °C.
Disappearance of topographical contrast in the backscattered electron image in scanning electron microscopy
Authors: Ikuta T.
Published: February 2003

A computer analysis of the topographical contrast due to surface projection in the backscattered electron image in the scanning electron microscope is described. Present results show that disappearance of the topographical contrast may occur at a certain condition between the incident beam angle and the detector take-off angle. This condition just corresponds to the experimental results previously reported.
Amplification of total-reflection-mode acoustic surface waves in n-type GaAs films
Authors: Wu Chhi-Chong , Tsai Jensan
Published: February 2003

The effect of nonparabolicty on the amplification of total-reflection-mode acoustic surface waves in n-type GaAs films has been investigated quantum mechanically in the GHz frequency region. Numerical results are obtained for an n-type GaAs epitaxial layer on a semi-insulating GaAs substrate at 77 K. Results show that the amplification coefficient oscillates with the frequency in the high-frequency region due to the inter-sub-band transitions.
Estimation of the band gap of InPO4
Authors: Wager J. F. , Wilmsen C. W. , Kazmerski L. L.
Published: February 2003

The band gap of a thin layer of InPO4 was estimated to be 4.5 eV using a novel approach employing ultraviolet photoelectron spectroscopy and electron energy loss spectroscopy. The technique measures the conduction-band minimum and valence-band maximum referenced to the In 4d core line energy. Since this technique is highly surface sensitive, it can be used to measure the band gap of a thin layer. This parameter is difficult to measure in such layers using conventional techniques.
New concept in optical information storage: Thermal relaxation of strain birefringence
Authors: Puebla Claudio , Michl Josef
Published: February 2003

Theoretical and preliminary experimental results are presented to demonstrate a new concept in optical information storage. The recording medium is a birefringent sheet of stretched polymer; the recording event is a modification of the birefringence by the action of heat, for instance, that generated by an absorbed laser pulse, or derived from contact with a heat source; the readout is based on the detection of changes in the state of polarization of a reading beam.
Lattice location of chromium in semi-insulating GaAs by ion channeling techniques
Authors: Haga T. , Abe Y.
Published: February 2003

Proton-induced x-ray emission combined with ion channeling techniques has been used to investigate the lattice location of Cr in GaAs grown by the Czochralski method. The angular dependence of Cr x-ray yields about the 〈100〉 and 〈110〉 directions indicated that the Cr atoms occupied the substitutional sites with no trace of well-defined Cr interstitials at the concentrations studied. Fe and Ni impurities in Cr-doped GaAs were located at the substitutional sites whereas Cu impurities were more likely distributed among random sites with respect to the host atoms.
Observation of defects in mercury cadmium telluride crystals grown by chemical vapor transport
Authors: Irene E. A. , Tierney E. , Wiedemeier H. , Chandra D.
Published: February 2003

A mixture of nitric and hydrochloric acids was found to yield etch pits on mercury cadmium telluride crystals grown by chemical vapor transport using iodine or mercuric iodide as the transport agent. Two types of pits were observed by optical microscopy: triangular pyramidal and round saucer shaped pits. Transmission electron microscopy confirmed that two types of defects were present: dislocations and second phase occlusions. The present study suggests that the defects are near the crystal surface and therefore will probably not significantly affect the electrical characteristics.
Direct measurement of the melt depth of silicon during laser irradiation
Authors: Hayafuji Y. , Aoki Y. , Usui S.
Published: February 2003

We have studied the change in morphology of laser irradiated silicon wafers by annihilating the oxygen thermal donors and the oxidation-induced stacking faults in order to verify the melting of the near-surface regions. The laser beam used was of 1.06 μm with a diameter of 40 μm, generated from a Q-switched neodymium:yttrium aluminum garnet (Nd:YAG) laser with a 150-ns pulse width and at a repetition rate of 12 kHz. Laser beam irradiation above about 6 J/cm2 annihilated both thermal donors and stacking faults, giving evidence of melting and suggesting that the annihilation of the thermal donors and of the stacking faults can be useful in studying the surface morphology in laser/electron beam irradiation.