bluuebunny/crossref_metadata_2025 huggingface dataset:
Small-area high-speed InP/InGaAs phototransistor
Authors: Campbell J. C. , Burrus C. A. , Dentai A. G. , Ogawa K.
Published: February 2003

We describe the fabrication and characteristics of a small-area (diameter ≃20 μm) InP/InGaAs heterojunction phototransistor, a promising photodetector/preamplifier for long-wavelength optical receivers. The high sensitivity (hfe ≃100 at 20-nW incident power) and small junction capacitance (≲0.2 pF) of the device combine to produce a gain-bandwidth product in excess of 1.7 GHz.
Electrical characteristics of Al contact to NiSi using thin W layer as a barrier
Authors: Bartur M. , Nicolet M-A.
Published: February 2003

We show that the thermal instability that is observed in Schottky diodes with an Al film on NiSi contact to 〈Si〉 can be removed by introducing a very thin (∼250 Å) tungsten film between the Al and the NiSi layers. This structure can be formed by sequential evaporation of Ni, W, and Al and subsequent thermal annealing to form NiSi. Schottky barrier measurements show that the contact is thermally stable at 450 °C up to about 1-h annealing with very little change in the electronic barrier height. A model, derived from the electrical measurements, is proposed for the failure mode of the tungsten barrier after excessive annealing.
A novel method for high resolution observation of magnetic structures in superconductors
Authors: Stöhr Peter L.
Published: February 2003

The magnetic structure of a superconductor in the intermediate state is imaged to a resolution of <0.9 μm using the response of the superconductor to electron beam irradiation.
Magnetic properties of amorphous and crystallized (Fe0.82B0.18)0.9Tb0.05La0.05
Authors: Koon N. C. , Das B. N.
Published: February 2003

The magnetic properties of (Fe0.82B0.18)0.9Tb0.05La0.05 in both the amorphous and crystallized states are presented. When amorphous, the alloy is magnetically soft and has a low coercive force, comparable to the corresponding alloy without rare earths. Upon annealing near the crystallization temperature of 900 K, however, the intrinsic coercive force at 300 K rises to 9 kOe, with a remanent magnetization of slightly less than 5 kG. In the amorphous state this and related alloys appear to have potential for use in devices requiring large, isotropic magnetostriction, while in the crystallized state they appear potentially useful as low cobalt permanent magnets.
Cube-root broadening of surface-charge packets
Authors: Thornber K. K. , Nelson D. F. , Cooper J. A.
Published: February 2003

The width of a surface-charge packet in the proximity of a conducting sheet increases asymptotically only as the cube root of the time due to space-charge repulsion. By contrast, thermal diffusion broadens as the square root of the time, and is otherwise negligible here. The cube-root behavior is invariant over a wide range of transverse and normal electric fields, and may have significant implications for the minimum spatial variation of charge density achievable in devices.
Coherent radiation from a relativistic electron beam in a longitudinal, periodic magnetic field
Authors: McMullin W. A. , Bekefi G.
Published: February 2003

The longitudinal wiggler, beam interaction is a novel source of submillimeter wave radiation. It comprises a relativistic electron beam gyrating in a longitudinally rippled, periodic magnetic field of the form B = ẑ[B0+B1 sin(k0 z)], where k0 = 2π/l and l is the period. Axial and transverse electron density bunching gives rise to a convectively unstable wave that propagates along the guiding magnetic field ẑB0. Its growth rate has been computed for the case of a cold beam.
Measurements of the dynamics of imploding wire arrays
Authors: Benjamin R. F. , Pearlman J. S. , Chu E. Y. , Riordan J. C.
Published: February 2003

Detailed observations of the dynamics of pulsed generator driven imploding wire arrays are presented. Peak velocities up to 20 cm/μs are measured. The peak implosion velocity is given as a function of array mass and is found to decrease monotonically with increasing mass. For more massive arrays, a core plasma is observed even when the wires in the array do not appear to implode. This core plasma may represent a significant current shunt and could cause a large decrease in the array implosion efficiency.
Extremely low threshold (AlGa)As modified multiquantum well heterostructure lasers grown by molecular-beam epitaxy
Authors: Tsang W. T.
Published: February 2003

It is shown that by modifying the layer structures of the conventional multiquantum well (MQW) lasers, extremely low Jth of 250 A/cm2 (averaged value) for broad-area Fabry–Perot diodes of 200×380 μm was obtained. This was achieved as a result of utilizing the beneficial effects of the two-dimensional nature of the confined carriers, the improved injection efficiency of the carriers into the GaAs wells, and an increased optical confinement factor in these modified MQW lasers. It was also determined that for low threshold operation the optimal AlAs composition x in the AlxGA1−xAs barrier layers is about 0.19 when GaAs wells are used and for barrier and well thicknesses ≳30 and 100 Å, respectively.
Aluminum nitride on silicon surface acoustic wave devices
Authors: Pearce L. G. , Gunshor R. L. , Pierret R. F.
Published: February 2003

Reactive rf planar magnetron sputtering has been used at substrate temperatures below 300 °C to deposit highly oriented piezoelectric AlN films on silicon for surface acoustic wave device applications. The substrates were (100)-oriented, n-type silicon with and without a thermally grown oxide. Several new AlM-on-silicon surface acoustic wave devices were fabricated and tested. The devices reported herein include two-port delay lines, degenerate monolithic convolvers, and two-port surface acoustic wave resonators utilizing metal strip reflector arrays.
Electromigration in aluminum/poly-silicon composites
Authors: Vaidya S.
Published: February 2003

A composite metallization of Al over doped poly-Si should exhibit superior electromigration resistance, since even after the Al develops an open circuit, the poly-Si would be expected to provide electrical continuity. However, results indicate that poly-Si reduces the lifetime of Al by a ×2 and a further decrease occurs over stepped topographies. Thus, while electron beam evaporated Al/poly-Si exhibits acceptable lifetimes, induction-source Al/poly-Si may be only marginal in this regard. Failures occur predominantly at steps by nonuniform grain boundary diffusion in Al, until the metal opens up. This followed by the electromigration of Si into Al and localized melting.
Stoichiometric disturbances in ion implanted GaAs and redistribution of Cr during annealing
Authors: Magee T. J. , Kawayoshi H. , Ormond R. D. , Christel L. A. , Gibbons J. F. , Hopkins C. G. , Evans C. A. , Day D. S.
Published: February 2003

Using the Boltzmann transport equation, calculations were obtained predicting the zones of stoichiometric imbalance produced in GaAs after ion implantation at energies of 50, 100, and 300 keV. The recoiling Ga and As atoms were shown to produce a zone of interstitials at depths exceeding Rp . Secondary-ion mass spectrometry profiling indicated that Cr was rapidly redistributed into these regions at temperatures ⩽500 °C. Transmission electron microscopic analyses obtained on horizontally sectioned and vertical cross section samples indicated that the interstitials coalesced into small clustered sites (50–100 Å) and were responsible for the development of Cr gettering at depths ≳Rp .
Absorption and stimulated emission in an AlAs-GaAs superlattice
Authors: Coleman J. J. , Dapkus P. D. , Clarke D. R. , Camras M. D. , Holonyak N.
Published: February 2003

Absorption and stimulated-emission data (77 and 300 K) are presented on a 50-period, all binary A1As-GaAs superlattice (SL) grown by metalorganic chemical vapor deposition (MO-CVD). Laser operation of the SL is observed ΔE∼h/ωLO below the absorption, which corresponds accurately to the lowest confined-particle transistions determined from the measured (transmission electron microscope, TEM) barrier and well sizes of LB ∼120 Å and Lz ∼160 Å.
Self-focusing of a low power cw laser beam via optically induced birefringence in a nematic liquid-crystal film
Authors: Khoo I. C. , Zhuang S. L. , Shepard S.
Published: February 2003

We present the results of a detailed experimental study of the self-focusing of a low intensity cw laser in its passage through a nematic liquid-crystal film. The results are in quantitative agreement with our theory of optically induced birefringence as a function of geometry, thickness, and intensity. We have also quantitatively measured the relative contribution from thermal lensing effect.
Exceptional second-order nonlinear optical susceptibilities of quinoid systems
Authors: Lalama S. J. , Singer K. D. , Garito A. F. , Desai K. N.
Published: February 2003

A new class of organic quinoid systems possessing intrinsically large, nonlinear second-order optical susceptibilities has been developed based on theoretical calculations and dc-induced second-harmonic generation measurements of the molecular second-order optical susceptibilities β. For one example, 2-(4-dicyanomethylenecyclohexa-2, 5-dienylidine)-imidazolidine (DCNQI), βx = −240±60×10−30 cm5/esu. The unusually large magnitude and sign originate from certain charge-correlated features in the quinoid ground and excited states.
Laser induced irreversible absorption changes in alkali halides at 10.6 μm
Authors: Wu S.-T. , Bass M.
Published: February 2003

Laser induced irreversible changes in the absorption of alkali halides has been observed by using repetitively pulsed laser calorimetry. These changes occur at intensities below that required for laser induced breakdown and necessitate a change in the definition of laser damage threshold. A simple model is proposed to explain these observations based on the accumulation of microscopic failures as a result of each pulse.
Scaling characteristics of ultrasmall Josephson junctions
Authors: Rogovin D. , Nagel J.
Published: February 2003

Recent advances in the technology of ultrasmall Josephson junctions focus interest on the scaling characteristics of these devices. We examine the size dependence of the pair current, the rms noise current as well as the voltage fluctuations of ultrasmall junctions, and find novel scaling behavior. Among other things, the low-temperature zero voltage, dc pair current depends on the cube of the junction area.
Interaction between arsenic, hydrogen, and silicon matrix in doping of sputtered amorphous hydrogenated silicon
Authors: Toulemonde M. , Siffert P. , Deneuville A. , Bruyère J. C.
Published: February 2003

Simultaneous variations of the concentrations of As, Si, and H in As doped and undoped sputtered a-Si:H structures are reported. The As is substitutional for Si, but most of the As atoms are also connected with an additional hydrogen and so inefficient for doping. The As doping also decreases significantly the material density. These results are shown to reject the usual assumption according to which doping atoms just supply carriers in the otherwise unchanged distribution of states of undoped a-Si:H.
Low temperature recombination lifetime in Si metal oxide semiconductor field effect transistors
Authors: Zetterlund B. , Steckl A. J.
Published: February 2003

The recombination lifetime τr has been measured at low temperature in Si p-channel metal oxide semiconductor field effect transistors (MOSFET’s) using the charge pumping technique. Measurements were performed over the 40–300-K range. A monotonically increasing lifetime with decreasing temperature was measured. τr was found to be proportional to exp(Ar/kT), where Ar is a constant determined from the slope of ln τ vs 1/T. For a typical MOSFET the lifetime ranged from 80 ns at 300 K to 370 μs at 100 K. The value of Ar in this case was determined to be 106 meV.
A novel three-step process for low-defect-density silicon on sapphire
Authors: Amano Jun , Carey Kent
Published: February 2003

A novel three-step process for producing low-defect-density epitaxial silicon layers on sapphire substrates has been developed. The three-step process utilizes a simple room-temperature ion implantation and solid-phase epitaxial regrowth. Both megaelectron volt helium backscattering and transmission electron microscopy (TEM) results indicate the excellent crystalline quality of silicon-on-sapphire (SOS) wafers produced by the three-step process. The backscattering minimum yields at the interface and the surface of the three-step SOS layer are 0.14 and 0.03, respectively. A TEM micrograph of the top 500 Å of the three-step SOS layer shows none of the planar defects which are common to standard SOS layers.
Multiplication noise of InP avalanche photodiodes
Authors: Shirai T. , Osaka F. , Yamasaki S. , Kaneda T. , Susa N.
Published: February 2003

An InP avalanche photodiode with a guard ring structure is fabricated. The maximum avalanche gain obtained is 210 at a primary photocurrent of 0.2 μA, and uniform photoresponse without local enlargement is obtained at an avalanche gain of 10. Multiplication noise characteristics are investigated, and the effective ionization rate ratio of holes to electrons is found to be 1.7–1.8.
Volume pinning force and upper critical field of irradiated Nb3Sn
Authors: Maier P. , Seibt E.
Published: February 2003

Irradiation by neutrons and ions in A15 superconductors (Nb3Sn, V3Ga) exerts a stronger influence on the pinning behavior than in nonordered alloys (NbTi). In this work it is shown for deuteron irradiated Nb3/Sn wires prepared by the bronze process that the dose curve of the volume pinning force PV can be conveniently described by a sum of two terms, due to the grain boundary pinning and to the radiation pinning, respectively. After deduction of the contribution by the radiation-induced pinning centers, good agreement is obtained between the measured PV values and those calculated using the upper critical field Bc2 and the transition temperature Tc on the basis of the irradiation fluence. The use of a theoretical relationship between Bc2 and Tc is supported by measured values. Application to multifilamentary superconductors with high current carrying capabilities simplifies the calculation of PV, since the radiation induced volume pinning force can be neglected.
Polarization independent optical filter using interwaveguide TE↔TM conversion
Authors: Alferness R. C. , Buhl L. L.
Published: February 2003

We report the first demonstration of a polarization-independent, integrated-optic wavelength filter. Polarization-independent filtering is achieved via wavelength selective TE↔TM conversion between a pair of mismatched Ti-diffused lithium niobate waveguides. A peak coupling efficiency of ∼75% and 5-Å filter bandwidth have been achieved.
A solar simulator-pumped atomic iodine laser
Authors: Lee Ja H. , Weaver W. R.
Published: February 2003

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 μm for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power observed was 4 W for which the system efficiency reached 0.1%. These results indicate that direct solar pumping of a gas laser for power conversion in space is indeed feasible.
Redistribution of oxygen within damage regions of boron-implanted silicon
Authors: Magee T. J. , Leung C. , Kawayoshi H. , Furman B. , Evans C. A. , Day D. S.
Published: February 2003

The redistribution and gettering of 16O in Si within boron-implanted regions has been investigated using transmission electron microscopy and secondary-ion mass spectrometry profiling. It has been shown that low-temperature (⩽ 600 °C) secondary annealings following normal high-temperature (900–1000 °C) annealing result in the rapid diffusion and gettering of oxygen within residual damage regions. The gettered oxygen is present in the form of SiOx precipitates stabilized along dislocations lines and residual damage structure.
The effect of photoelectrochemical etching on the performance of CdTe polysulfide photoelectrochemical cells
Authors: Müller N. , Tenne R.
Published: February 2003

Photoelectrochemical etching of n-CdTe single crystals was found to improve both short circuit current and photovoltage of a CdTe-polysulfide photoelectrochemical solar cell. Variation of the photoetching time influences drastically the power output and the spectral response of the cell. The experimental results can be interpreted as follows: a short photoetching mainly removes recombination centers near the electrode surface, whereas a prolonged photoetching leads to photocorrosion of the electrode. Pits of ∼0.1 μ appear on the surface of the electrode after the photoetching similar to those found in CdSe.
Applicative aspects of the transport phenomena in liquids induced by laser beams
Authors: Delfino G.
Published: February 2003

Mass and heat transport induced by an Ar+ laser beam in liquid samples are considered. The use of the Onsager reciprocity and of the Gibbs–Duhem relations permits us to derive an approximate relation which relates local temperatures to temperature gradients by means of several physical parameters, i.e., density, specific heat, thermal conductivity, diffusion coefficient, viscosity, and surface tension of the specimen. The measure of one of these parameters, if unknown, is also possible.
Heating of a dense plasma using an intense, relativistic electron beam
Authors: Montgomery M. D. , Parker J. V. , Riepe K. B. , Sheffield R. L.
Published: February 2003

We report observations of heating of a dense (∼1017 cm−3) plasma using a 3-MeV electron beam with a current density of 5×105 A/cm2. The measured, strong dependence of heating on beam transverse temperature and the short saturation distance (<4 cm) are evidence that the beam-to-plasma energy transfer takes place via a fast growing microinstability such as the relativistic electron-electron two stream.
Slip deformation and melt threshold in laser-pulse-irradiated Al
Authors: Follstaedt D. M. , Picraux S. T. , Peercy P. S. , Wampler W. R.
Published: February 2003

We have examined pulse laser-irradiated 〈110〉 Al single crystals near the threshold energy for melting by ion channeling and electron microscopy. We find that slip deformation occurs at incident energies <3.5 J/cm2, where melting does not occur for our 20 nsec (full width at half maximum) pulse width, as well as at energies ≳3.5J/cm2, where a near-surface layer is melted. This slip deformation results in an increase in the channeling minimum yield χmin, which is attributed to small-angle misalignments between slip planes across the surface. The abrupt increase in χmin with melting suggests that channeling can provide a sensitive monitor of the threshold for melting.
The low-temperature thermal expansion of Hg1−xCdxTe alloys
Authors: Caporaletti O. , Graham G. M.
Published: February 2003

The linear coefficient of thermal expansion of semiconducting Hg1−xCdxTe has been determined for alloy compositions x = 0.20 and 0.30, of interest to infrared detector technology. The temperature dependence is similar to that of other compounds of zinc blende structure. The thermal expansion coefficient becomes negative at 64 K and is insensitive to composition except below 30 K, where the alloys richer in HgTe exhibit a deeper negative minimum.
Periodic motion of the crystallization front during beam annealing of Si films
Authors: Lemons R. A. , Bösch M. A.
Published: February 2003

Periodic surface topography is observed in Si films deposited on fused quartz when the films are crystallized by a scanning laser or electron beam. The formation and character of this topography depends upon the structure of the Si film. With amorphous Si, periodic features can be formed at the leading edge of the beam. We thick these are produced by self sustained crystallization as has been previously studied in Ge and other materials. Liberation of latent heat in the film enables the crystallization front to propagate a short distance ahead of the beam. In the moving temperature gradient this motion is periodic and therefore leaves a periodic crystal grain pattern. With polycrystalline silicon films, recrystallization requires the beam to melt the film. Periodic structures form at the trailing edge of the molten pool. Similar ripples have been studied in other materials. The temperature distribution in the melt can cause a surface tension gradient that pulls material to the edges. When this material solidifies, expansion of the silicon may enhance the ripple amplitude.
New Fermi energy pinning behavior of Au on GaAs (110) suggesting increased Schottky-barrier heights on n-type GaAs
Authors: Skeath Perry , Su C. Y. , Hino I. , Lindau I. , Spicer W. E.
Published: February 2003

An unusually large Schottky barrier (≳1.1 eV) is demonstrated by studies of Au on atomically clean n-type GaAs. It is suggested that this large barrier is produced by Au moving beneath the surface and introducing new gap states close to the valence band maximum. These new gap states can overcome the defect states (produced during the adsorption process) that normally pin the Fermi energy near midgap, thus increasing the barrier height. Starting with an atomically clean surface appears essential.
Picosecond microwave pulses generated with a subpicosecond laser-driven semiconductor switch
Authors: Mourou G. , Stancampiano C. V. , Antonetti A. , Orszag A.
Published: February 2003

A subpicosecond laser has been used to trigger a GaAs photoconductive switch driving a dipole antenna. The microwave transient produced was measured with a correlation technique to have a FWHM of less than 3 psec. This technique was also used in a contactless measurement of the 250-psec lifetime of a GaAs sample.
Long pulse behavior of the avalanche/self-sustained discharge pumped XeCl laser
Authors: Levatter Jeffrey I. , Robertson Karin L. , Lin Shao-Chi
Published: February 2003

Homogeneous and stable avalanche/self-sustained discharges of 200-nsec duration have been obtained in typical XeCl laser gas mixtures at relatively high gas pressures (1–4 atm) and high energy loadings (100–400 J/liter-atm). The laser output waveform, however, is found to be surprisingly sensitive to changes in gas pressure and composition. Under certain conditions, the laser power remains nearly constant for 200 nsec, so that the total output energy scales roughly with the discharge duration. The highest XeCl laser pulse energy extracted from a 1-liter volume in this series of experiments is 3.2 J at ∼4% intrinsic efficiency.
Single-crystal Si films on SiO2 prepared by using a stationary graphite heater for lateral epitaxy by seeded solidification
Authors: Fan John C. C. , Tsaur B.-Y. , Geis M. W.
Published: February 2003

Continuous single-crystal Si films on SiO2 have been prepared by a simplified version of the technique for lateral epitaxy by seeded solidification (LESS). The new method employs transient heating by a simple stationary graphite heater, while the original method utilized two graphite heaters, one of which was moved during LESS processing. The Si films obtained by the one-heater method are comparable in crystal quality to those prepared by the two-heater method.
Recovery of range-zone luminescence by pulsed laser annealing in Cd+-implanted GaAs
Authors: Norris C. B. , Peercy P. S.
Published: February 2003

The effects of 300-K implantation of 200-keV Cd+ ions and subsequent pulsed laser annealing in GaAs were investigated by means of depth-resolved cathodoluminescence at 80 K. We found that lattice order could be restored sufficiently to increase the implanation-quenched luminescence by 2–3 orders of magnitude with either ruby or Nd:glass lasers. Thus the luminescence is recovered to within an order of magnitude of that in unimplanted material.
The physical content of the singularity expansion method
Authors: Űberall Herbert , Gaunaurd Guillermo C.
Published: February 2003

The singularity expansion method describes the echo return from pulsed radar signals in terms of a Prony-series superposition of damped sinusoids. These are obtained as the residues of poles of the scattering amplitude in the complex frequency plane. For the example of radar scattering from a conducting sphere, we show that these poles can be regrouped into infinite subsets whose residues sums represent individual creeping waves, the nth pole in the subseries corresponding to the resonance caused by a standing creeping wave with n+1/2 wavelength spanning the circumference. The corresponding Prony subseries thus appears simply as a mathematical device which synthesizes the physical creeping wave.
Deuterium in He-implanted Fe: Trapping and the surface permeation barrier
Authors: Myers S. M. , Besenbacher F. , Bo/ttiger J.
Published: February 2003

Deuterium (D) and He were ion-implanted into Fe, and the D depth distribution was monitored during linear ramping of temperature. Defects associated with He, possibly small bubbles, were observed to trap the D with an enthalpy of 0.75±0.07 eV. The previously air-exposed Fe surface was a substantial permeation barrier to D: data analysis yielded a recombination coefficient of 10−18±0.7 cm4/sec at 500 K.
Pulsating output of separate confinement buried optical guide lasers due to the deliberate introduction of saturable loss
Authors: van der Ziel J. P. , Tsang W. T. , Logan R. A. , Augustyniak W. M.
Published: February 2003

Proton bombardment at 3×1015–1016-cm−2 dosage level and 300 keV has been used to introduce a ∼4-μm-long nonradiative region at one of the mirror facets. The region acts as a saturable absorber and converts the initially temporally stable optical emission to a pulsating behavior with a repetition rate in the 0.5–3-GHz range.
Thermal contact probing by photoacoustic effect
Authors: Monchalin J.-P. , Parpal J.-L. , Bertrand L. , Gagné J.-M.
Published: February 2003

The influence on the photoacoustic signal of the thermal contact resistance at the interface sample substrate is investigated using a thin metallic foil (thickness ∼12.5 μm) as sample. The foil is either applied by pressure against the substrate or epoxyed on it. The resistance is determined by interpreting magnitude and phase data obtained by varying the laser source modulation frequency. In the light of the results obtained with the thin foil, we discuss the limitations introduced by thermal contact in the photoacoustic detection of aerosols collected on a surface.
Integrated grating acoustic scanner
Authors: Chen W. H. , Lean E. G.
Published: February 2003

This letter describes a new type of electronically scanned and focused acoustic imaging device called the integrated grating acoustic scanner. In this device, a nonlinear chirped surface acoustic wave pulse expansion/compression filter and an array of grooves were integrated on the same piece of piezoelectric single-crystal plate. The periodical grooves scattered a chirped surface-wave pulse coherently into a focused bulk-wave spot, which scans at the surface-wave velocity. A 150-MHz integrated LiNbO3 grating scanner with 1-cm field of view and 40-μm resolution has been constructed and studied.
A high gain In0.53Ga0.47As/InP avalanche photodiode with no tunneling leakage current
Authors: Kim O. K. , Forrest S. R. , Bonner W. A. , Smith R. G.
Published: February 2003

We have fabricated high quantum efficiency, high-gain (≊5500) avalanche photodiodes with long-wavelength sensitivity up to λ = 1.7 μm. The primary dark current density at breakdown is JPR⩽8×10−5 A/cm2 with no evidence for tunneling leakage prior to avalanche. To fabricate avalanche photodiodes with no tunneling leakage and high photoresponse at breakdown, we find that the total number of fixed charges in the n-InP layer must lie in the range of 2×1012 cm−2⩽σB⩽3×1012 cm−2.
Analysis of high resistivity semiconductor specimens in an energy-compensated time-of-flight atom probe
Authors: Melmed A. J. , Martinka M. , Girvin S. M. , Sakurai T. , Kuk Y.
Published: February 2003

It is shown that high resistivity semiconductor specimens (at least up to 8.6×103, and probably up to 2.4×104 Ω cm) can be analyzed in a conventional energy-compensated time-of-flight atom probe by using pulses of longer than usual duration and that the necessary pulse width increases with specimen resistance.
The effect of As/Ga flux ratio on the photoluminescent spectra from molecular beam epitaxially-grown Sn-doped AlxGa1−xAs
Authors: Tsang W. T. , Swaminathan V.
Published: February 2003

It is shown that the As/Ga flux ratio γf during molecular beam epitaxial growth has significant effects on the photoluminescent (PL) spectra at 5.5 K from a Sn-doped AlxGa1−x As (x∼0.27–0.33) layer. At any growth temperature Ts samples grown under low γf have higher PL intensity than those grown under high γf . Based on the 5.5-K PL spectra we arrive at the important conclusion that the highest-quality AlxGa1−xAs is grown under conditions of high Ts and low γf , followed by layers grown at high Ts and high γf, and at low Ts and low γf , with the poorest-quality layers grown under conditions of low Ts and high γf. The present results are consistent with the fact that low-threshold double-heterostructure lasers are obtained only when Ts is high.
Temperature dependence of optical gain spectra in GaInAsP/InP double-heterostructure lasers
Authors: Jung H. , Göbel E. , Romanek K. M. , Pilkuhn M. H.
Published: February 2003

Optical gain spectra of GaInAsP/InP double heterostructures (DHs) have been recorded in the temperature range of 80–300 K. These data are compared with threshold currents of DHs injection lasers fabricated from the same wafers. An identical behavior of maximum optical gain and threshold current is observed, i.e., two T0 values (100 and 63 K) with a break-point temperature of TB ≃260 K are found. Furthermore, characteristic changes of the optical gain spectrum are observed close to the break-point temperature.
Tunneling-determined threshold current in Pb1−xSnxTe diode lasers
Authors: Eger D. , Oron M. , Zemel A. , Zussman A.
Published: February 2003

The current transport mechanism in n+-n-p+ homostructure diode lasers of Pb1−xSnxTe prepared by liquid-phase epitaxy was studied using measurements of the I-V characteristics as a function of temperature. It is found that the lasing threshold is dominated by excess tunneling current and not by diffusion current as previously assumed. To the best of our knowledge this is the first attempt to study the diffusion component of the injected current which determines the population inversion, and hence the threshold current, by analyzing the I-V characteristics. The results of this work raise some doubt about the validity of the existing theoretical calculations of the threshold current in lead-salt diode lasers.
Annealing and anomalous high-energy electron irradiation effects in low-cost silicon N+P solar cells
Authors: Garlick G. F. J. , Kachare A. H.
Published: February 2003

Silicon solar cells of N+P type made from multiple ingots grown from a single crucible were either subjected to 1-MeV electron irradiation (fluence up to 1016 electrons/cm2) and then annealed at 450 °C for 20 min or to the annealing alone with no electron irradiation. Electron irradiation gave the expected degradation of longer-wavelength cell response but at shorter wavelengths produced a marked enhancement of response with peak change of some 40% at 0.44 μm. Subsequent thermal anneal at 450 °C reduced the long-wavelength degradation, but the enhancement at shorter wavelengths persisted. Excitation at the shorter wavelength is predominantly in the N+-diffused layer and to some extent in the junction region of the cell. Anneal of unirradiated cells at 450 °C also produced the shorter-wavelength enhancement at about half of that due to electron irradiation and more enhancement into the longer wavelength region (up to 0.8 μm), finally giving a small degradation. These effects in the different cell regions are attributed to a decrease in interstitial oxygen-impurity complexes which act as deep recombination levels and the formation of substitutional oxygen-silicon vacancy centers which act as donors. The investigations indicate that thermal regimes during cell processing can produce cell spectral characteristics that might be further improved by modification of such regimes.
A subharmonic Josephson relaxation oscillator—amplification and locking
Authors: Calander N. , Claeson T. , Rudner S.
Published: February 2003

The inductance of the shunt loop in a resistively shunted Josephson tunnel junction may cause relaxation oscillations at subharmonics of the Josephson frequency. The relaxation period, the injection locking to a subharmonic of a strong external signal, and the amplification of weak signals were studied in detail. Gains up to 15 dB were achieved, but the noise temperature, which depended upon the harmonic of the relaxation frequency at which the amplification occurred, was high.
Electrical conductivity of semi-insulating polycrystalline silicon and its dependence upon oxygen content
Authors: Ni James , Arnold Emil
Published: February 2003

An explanation is given for the strong dependence of electrical conductivity of semi-insulating polycrystalline silicon films on oxygen content. The proposed model assumes a shell structure such that each Si grain is surrounded by a layer of SiO2, the thickness of which is related to the oxygen content of the film. The conduction proceeds by tunneling of thermally generated carriers through the oxide layers separating adjacent grains. The model properly predicts the dependence of the low-field conductivity on both oxygen concentration and temperature without any adjustable parameters. Evidence for oxide barrier lowering for barrier thicknesses <5 Å is observed.
Study of ultraviolet light-induced aging of ZnS phosphor powder by two-beam photoacoustic spectroscopy
Authors: Simmonds P. E. , Eaves L.
Published: February 2003

A two-beam photoacoustic technique is employed to monitor ultraviolet light-induced darkening of ZnS (Mn, Cu) powder used for large-area electroluminescent panels. The darkening process occurs for ultraviolet irradiation at wavelengths less than 345 nm. Photoacoustic measurements are made of the light-induced change in the absorption spectrum and the influence of doping and contamination by atmospheric water on darkening rates.
Low-noise GaAs field-effect transistors prepared by molecular beam epitaxy
Authors: Omori M. , Drummond T. J. , Morkoç H.
Published: February 2003

The noise performance of ’’T’’ shaped Ti/W/Au gate GaAs Schottky-barrier field-effect transistors (FET’s) fabricated on channel layers grown by molecular beam epitaxy (MBE) is reported. The nominal gate length was about 0.7 μm with a total gate width of 250 μm. Typical noise figures and the associated gains at room temperature were 1.2 and 14 dB at 4 GHz, and 1.9 and 8.5 dB at 12 GHz. To our knowledge, these are the best results reported to date by MBE. These preliminary results, while not reaching the state of the art, do show the promise of MBE for high-quality GaAs FET’s.
Lorentz electron microscopy of amorphous Fe40Ni40B20
Authors: Fidler J. , Skalicky P.
Published: February 2003

Using transmission electron microscopy we studied changes in the magnetic domain structure during annealing. At room temperature the domain structure is determined by magnetostatic effects. Cross-tie walls are observed, and the domains vanished at fields of 25 A/cm. After heating the specimen, a two-stage crystallization behavior occurs. The first stage (140–250 °C) is identified as primary crystallization of polycrystalline δ-Fe Ni. Further heating (up to 400 °C) shows the formation and growth of (Fe Ni)3B spherulites. The domain structure is determined by the crystallization process. Large spherulites exhibit stripe domains and inside of nonspherulite areas magnetization ripple structures occur. Both of the crystallization centers act as pinning sites for domain walls and are sources of increased coercivity in Fe40Ni40B20 amorphous ribbons.
Subpicosecond pulses from passively mode-locked GaAs buried optical guide semiconductor lasers
Authors: van der Ziel J. P. , Tsang W. T. , Logan R. A. , Mikulyak R. M. , Augustyniak W. M.
Published: February 2003

We report the observation of bursts of transform-limited 0.65-psec pulses at 1-GHz repetition rates by passive mode locking of a buried optical guide laser in an external cavity. The lasers contain a saturable absorber at the exit facet, specifically introduced by 600-keV proton bombardment at a 3×1015- cm−2 dosage level.
Phase noise of single-mode diode lasers in interferometer systems
Authors: Dandridge A. , Tveten A. B.
Published: February 2003

Measurements have been made of the phase noise of six different types of single-mode diode laser in an unbalanced Michelson interferometer, as a function of optical path difference. The frequency dependence of the phase noise has also been determined. Possible origins of the frequency fluctuations which result in the phase noise are discussed. The detrimental effect of the phase noise on the sensitivity and dynamic range of optical fiber interferometer sensors is briefly discussed.
Microscopically textured optical storage media
Authors: Craighead H. G. , Howard R. E.
Published: February 2003

A new optical information storage technique is described which operates by irreversibly altering the absorption properties of a microscopically textured surface. Reflectance changes of greater than a factor of 100 have been obtained by local melting of the surface. A random array of Si columns with cross-sectional dimensions less than 100 nm, formed on a Si film by reactive ion etching, has a visible reflectance of less than 0.01. By irradiation with a focused laser beam, at a power density of ≲8 mW/μm2, the columns melt to form a surface with a specular reflectance of ∼0.4. The applicability of this surface structure as a permanent optical storage medium is discussed. In general, this surface texturing can be applied to a wide variety of materials with the advantages of increased sensitivity to the writing beam, large contrast between the written and unwritten areas and reduced lateral energy flow.
GaAs-AlxGa1−x As superlattices as sources of polarized photoelectons
Authors: Alvarado S. F. , Ciccacci F. , Campagna M.
Published: February 2003

We have measured the spin polarization of electrons optically pumped by polarized light and photoemitted from GaAs-AlxGa1−xAs superlattices with negative electron affinity. We find a maximum polarization of 49%, in contrast to the expectations related to polarized photoluminescence studies. Reasons for these findings based on the difference between photoemission from negative electron affinity sources and photoluminescence are discussed.
Condensation of bombarding gallium ions on a silicon surface
Authors: Ishitani T. , Shimase A. , Tamura H.
Published: February 2003

Direct observation of bombarding 5–15-keV Ga+ ion condensation on a Si target is achieved using a scanning ion microscope with a liquid-Ga ion source. The liquidlike pieces of condensed Ga move about easily to join or split. Condensation takes place beyond a critical ion dose, which is roughly explained by an implanted-ion build-up model.
Preheat-aided optical disc recording
Authors: Goldberg Mark W. , Cassidy J. Christopher
Published: February 2003

Analytic and experimental results are presented to demonstrate the advantages of using a cw preheat spot in conjunction with a larger write spot in an optical disc recording system. When compared with conventional single spot writing, the use of preheat allows smaller holes to be recorded while requiring up to 50% less power from the write source. Results are presented for a preheat-to-write-spot ratio that assumes a He-Cd laser preheat source and semiconductor laser write source. An increase in packing density of almost a factor of 2 and an increase in bandwidth of 15% are demonstrated.
Time- and space-resolved temperature of a 10.6-μm laser-irradiated foil
Authors: Nishimura H. , Yagi M. , Matsuoka F. , Yamada K. , Yamanaka T. , Nakai S. , Yamanaka C.
Published: February 2003

Energy flow to a target rear surface due to hot electrons was experimentally studied by irradiating a 10-μm wavelength laser. Lateral heat conduction produced a plasma of low and uniform temperature, whose size was nearly one order larger than that of a laser focal spot for plane targets. Experimental results were simulated by using a one-dimensional hydrodynamic simulation code to investigate the effects of hot electron diffusion.
Enhancement of the Young’s modulus in the ultrafine Cu-Nb filamentary composites
Authors: Cohen David E. , Bevk J.
Published: February 2003

Measurements of the Young’s modulus are reported for in-situ formed Cu-Nb wire composites containing 7.5 and 15.0 vol.% niobium filaments. Comparison of the experimental values for the as-drawn and annealed wires shows rapidly diverging trends with decreasing wire diameter. In composites with the smallest filaments (50–200 Å) the modulus increases by almost 100% upon annealing and exceeds the maximum values calculated from bulk elastic constants. However, plastic strain (in elongation) of as little as 0.02% results in a substantial (∼25%) reduction in modulus, suggesting that most of the enhancment in the annealed composites originates from the thermally induced elastic strains at the matrix-filament interfaces.
Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses
Authors: Liu J. M. , Yen R. , Kurz H. , Bloembergen N.
Published: February 2003

Ultrafast melting and resolidification on a (111) sufarce of a silicon crystal wafer, induced by 20-ps pulses at 532-nm wavelength, is accompanied by the emission of charged particles. This emission is studied as a function of pulse energy, in combination with time-resolved reflectivity changes and post-annealing morphology. The data provide evidence that thermalization time for a dense carrier plasma and the lattice is shorter than 10−11 s.
Josephson single-flux-quantum logic circuits using niobium weak links
Authors: Tamura H. , Okabe Y. , Sugano T.
Published: February 2003

Josephson logic circuits using fluxoid quantization in a one-junction interferometer to represent logical states have been fabricated from thin films of Nb by means of photolithography, electron beam lithography, and reactive ion etching. A variable thickness bridge is used as a Josephson junction in the one-junction interferometer. The logic circuits have shown AND and OR logic functions.
Transport properties of GaAs-AlxGa1−x As heterojunction field-effect transistors
Authors: Tsui D. C. , Gossard A. C. , Kaminsky G. , Wiegmann W.
Published: February 2003

We report low field transport properties of n-channel GaAs-AlxGa1−x As heterojunction field-effect transistors. Studies of the Shubnikov-de Haas effect confirm that the devices are insulated-gate field-effect transistors, with AlxGa1−x As as the gate insulator. The channel mobility increases with density following μ2∼ nγ, with γ varying from 0.45 to 1.4. μ = 1.2×105 cm2/V sec at 78 K and 3.6×105 cm2/V sec at 4.2 K are observed at n∼4×1011/cm2.
Electron-hole recombination in reactively sputtered amorphous silicon solar cells
Authors: Moustakas T. D. , Wronski C. R. , Tiedje T.
Published: February 2003

The electron-hole recombination has been investigated in reactively sputtered hydrogenated amorphous silicon (a-SiHx) metal Schottky barrier solar cell structures. We find that electron-hole recombination proceeds through states in the middle of the gap. These states, whose density depends on the degree of hydrogenation, have been associated with Si dangling bonds and their effective carrier capture cross section was estimated to be 6×10−15 cm2.
Explosive crystallization of a-Si films in both the solid and liquid phases
Authors: Auvert G. , Bensahel D. , Perio A. , Nguyen V. T. , Rozgonyi G. A.
Published: February 2003

In this letter, we show that explosive crystallization can occur sequentially along the same laser scan line either from the liquid phase or in the solid phase. Which phase dominates depends on the laser scan speed, the proximity of the a-Si melting isotherm, and the magnitude of the ’’thermal kick’’ provided by fluctuations in laser power or at localized regions of higher absorption.
Stability of n-i-p amorphous silicon solar cells
Authors: Staebler D. L. , Crandall R. S. , Williams R.
Published: February 2003

Unencapsulated, amorphous silicon indium tin oxide/n-i-p/stainless-steel solar cells were tested for stability. All cells have excellent shelf life. Changes occur during exposure to light, but can be controlled by the deposition conditions of the amorphous silicon. The changes are due to trapping and recombination of optically generated carriers in the i layer, and are reversibly annealed out above 175 °C. Preliminary life tests on two relatively stable cells showed a small initial drop to 5%, followed by a weak logarithmic decay that predicts only ∼20% further decrease in efficiency after 20 years in sunlight. Work is continuing on improving the efficiency and stability of these cells.
The reliability of (AlGa)As double-heterostructure lasers grown by molecular beam epitaxy
Authors: Tsang W. T. , Hartman R. L. , Schwartz B. , Fraley P. E. , Holbrook W. R.
Published: February 2003

The cw accelerated aging behavior of proton-bombarded stripe geometry lasers fabricated from MBE grown DH wafers have been studied. The laser diodes were formed into a 5-μm-wide shallow proton-irradiated stripe geometry and operated without mirror coatings in dry nitrogen 70 °C ambients at constant power outputs of 2.5 mW and 3.0 mW/mirror. A feasibility demonstration of long lifetimes was obtained for lasers from three selected MBE wafers; where a median lasing lifetime of 8800 h with a standard deviation of 1.5 was found at 70 °C, which projects to a mean laser lifetime ≳106 h at room temperature. After initial aging, long-term degradation rates as low as 0.7 mA/kh for the operating current at 70 °C have been measured. The present results also show that the rate of change of the operating current with aging for MBE diodes is more uniform than for typical LPE diodes fabricated with the same technology. Data are presented for lasers from one of the wafers that show that after 1500 h of 70 °C cw aging, many of the electrooptical characteristics are relatively unchanged.
Photodissociation of HgBr, XΣ1/2
Authors: Krauss M. , Stevens W. J.
Published: February 2003

Transition moments and energies have been calculated for the X-A, bound to continuum, transition in HgBr. Absorption at the laser wavelength of 502 nm has been examined for two sets of absorbing states: A thermal distribution of vibrational levels at 500° K and the terminus vibrational level of the B-X laser transition. In the first case a cross section of 7×10−20 cm2 is calculated. Since no fast reaction for removal of the X state is known, the number density can exceed 1016 cm−3 and a significant absorption will result in late times. In the second case the laser photon can be coherently absorbed in the X-A transition leading to photon induced predissociation of the v = 0, B state. An upper bound to the predissociation rate for a 2-MW/cm2s flux is 106 s−1. Electron dissociative attachment of the X state is also shown to be improbable as a means of fast removal. Energy curves of the ground states of both the neutral and negative ion of HgBr are shown not to cross in any accessible region.
High-resolution pattern definition in tungsten
Authors: Randall John N. , Wolfe J. C.
Published: February 2003

We describe a process for high-resolution pattern definition in tungsten films. The high etch ratio of tungsten to a Au/Pd durable mask in an SF6/O2 plasma permits the use of a high-resolution, thin resist, electron beam lithographic process. 200-nm lines have been etched with vertical walls in 1000-nm tungsten films.