bluuebunny/crossref_metadata_2025 huggingface dataset:
Demonstration of a new oscillator based on real-space transfer in heterojunctions
Authors: Coleman Paul D. , Freeman Jay , Morkoç H. , Hess K. , Streetman B. , Keever M.
Published: February 2003

A new real-space transfer oscillator is demonstrated in a layered GaAs/nAlGaAs heterojunction. A dc bias field, plus the ac oscillating field, is applied parallel to the layer interfaces to modulate the electron transfer from the GaAs layers to the nAlGaAs layers. This periodic electron transfer results in the ac current being 180° out of phase with the ac voltage and power being generated. A unique characteristic of this oscillator is that the electron transit times are associated with transverse dimensions and not dimensions between the ohmic contacts which should permit its extension to very high frequencies.
Dose dependence of epitaxial regrowth of Se-implanted GaAs
Authors: Bhattacharya R. S. , Pronko P. P. , Ling S. C. , Wilson S. R.
Published: February 2003

High resolution Rutherford backscattering and channeling measurements have been used to investigate the annealing behavior of Se-implanted GaAs layers. The dose dependence of the as-implanted damage and residual disorder after annealing at 400 °C has been examined. Results show that the residual disorder increases rather sharply at a dose just above that required to amorphize the surface layer and then reaches a saturation level. Once the saturation level is reached, the residual disorder is dependent almost linearly on the thickness of the amorphous layer.
Hot-carrier relaxation in p-In0.53Ga0.47As
Authors: Shah Jagdeep , Nahory R. E. , Leheny R. F. , Degani J. , DiGiovanni A. E.
Published: February 2003

Experimental results demonstrate that photoinduced carrier heating in In0.53Ga0.47As is substantially reduced in the presence of a large background population of holes. These results are interpreted in terms of the increased effective coupling of carriers to the lattice in the presence of background holes.
High field temperature dependent electron drift velocities in GaAs
Authors: Windhorn T. H. , Roth T. J. , Zinkiewicz L. M. , Gaddy O. L. , Stillman G. E.
Published: February 2003

Electron drift velocities in (100) GaAs have been measured at various temperatures from 95 to 385 K for electric field strengths from about 15 to 160 kV/cm at most temperatures and as high as 236 kV/cm at 300 K using a microwave time-of-flight technique. The velocity decreases monotonically with increasing electric field strength at all temperatures over the entire field range investigated.
Observation of deep levels associated with the GaAs/AlxGa1−xAs interface grown by molecular beam epitaxy
Authors: McAfee S. R. , Lang D. V. , Tsang W. T.
Published: February 2003

We report the first direct observation of deep levels associated with the n-GaAs/N-Al0.25Ga0.75As heterointerface in a double heterostructure (DH) laser grown by molecular beam epitaxy (MBE). The concentration of these states in a nonoptimum device having a high threshold current density is 3×1010 cm−2. The states have an average energy of Ec−0.66 eV and appear to be localized in the n-GaAs within 140 Å of the interface. The relationship of these states to the laser threshold is discussed.
Effective barrier heights of mixed phase contacts: Size effects
Authors: Freeouf J. L. , Jackson T. N. , Laux S. E. , Woodall J. M.
Published: February 2003

Computer simulations of mixed phase Schottky contacts have been performed to gain insight into the effects of lateral dimensions upon device behavior. As expected, lateral dimensions comparable to the Debye length of the semiconductor result in strong modification of the device characteristics that would result from independent, parallel diodes. We suggest that such effects can play a role in most experimentally obtained contacts. Current models of Schottky barrier formation typically invoke kinetics-limited chemical interactions at the metal-semiconductor interface; such effects are unlikely to be laterally uniform over macroscopic dimensions, and may well provide strong sensitivity to seemingly minor variations in preparation techniques used by different groups. We demonstrate that mixed phase contacts, with size effects, can affect ideality factors, and can also cause disagreement between C-V and I-V barrier heights.
Mechanism of asymmetric longitudinal mode competition in InGaAsP/InP lasers
Authors: Ishikawa Hiroshi , Yano Mitsuhiro , Takusagawa Masahito
Published: February 2003

The mechanism of asymmetric longitudinal mode competition in InGaAsP/InP lasers is discussed. It is shown that the asymmetric mode competition is not due to the spatial hole burning. When we assume that the energy relaxation time of electrons in the conduction band is ∼0.3 ps, we find that the asymmetric longitudinal mode competition is well explained by the model of Bogatov et al. for the external cavity laser. The asymmetric mode competition can be understood on the basis of the pulsation of the electron population at the beat frequency between two longitudinal modes of ∼1012 Hz. The long energy relaxation time may have relevance to the observed low characteristic temperature of the quaternary lasers.
Semiconductor internal-reflection-interference laser
Authors: Choi Hong K. , Wang Shyh
Published: February 2003

A semiconductor interferometric laser with built-in index guiding for lateral mode stability is reported. Interference is caused by internal reflection from a small notch in the waveguide channel. Very stable single longitudinal mode and stable lateral mode were observed. The intereference also causes wavelength locking over the ranges of more than 7 °C within which the wavelength changes at a moderate rate of about 0.6 Å/°C.
Laser induced phase locking of hydrogen plasma striations
Authors: Glab Wallace , Nayfeh Munir H.
Published: February 2003

Laser induced transient striations of a hydrogen discharge plasma are studied as a function of the ’’detuning’’ of the discharge parameters from the steady-state oscillatory response conditions. We observed laser induced phase locking of the steady-state striations.
Rippled-field magnetron
Authors: Bekefi G.
Published: February 2003

The rippled-field magnetron is a novel crossed-field millimeter wave source in which electrons move in nearly circular paths under the combined action of a radial electric field, an axial magnetic field, and an azimuthally periodic wiggler magnetic field, Bw cos (Nϑ) oriented transversely to the flow. Estimates are given of the frequency and growth rate of the free-electron laser (FEL) type of instability excited in this smooth-bore magnetron configuration.
Effect of phosphorus and boron impurities on amorphous silicon solar cells
Authors: Moustakas T. D. , Friedman R. , Weinberger B. R.
Published: February 2003

The effect of dopant impurities (P,B) on the performance of sputtered α-SiHx solar cells has been investigated. We find, for example, that during the deposition of the N+ layer of N+-I-Pt Schottky barrier structures, the chamber is contaminated with phosphorous which subsequently degrades the intrinsic film. This effect may be eliminated by prolonged pumping of the chamber between N+ and I layer depositions or by ’’compensating’’ the effects of phosphorous in the I layer through the intentional addition of low levels of boron.
Direct observation of grain boundary effects in polycrystalline silicon thin-film transistors
Authors: Leamy H. J. , Frye R. C. , Ng K. K. , Celler G. K. , Povilonis E. I. , Sze S. M.
Published: February 2003

We have applied charge collection scanning electron microscopy to the gate capacitor of n-channel thin-film transistors that were fabricated in laser recrystallized polycrystalline silicon. The action of grain boundaries as impediments to channel current flow and as fast diffusion paths for source and drain dopants is directly observed.
Spectroscopy of donors in high purity GaAs grown by molecular beam epitaxy
Authors: Low T. S. , Stillman G. E. , Cho A. Y. , Morkoc H. , Calawa A. R.
Published: February 2003

Photothermal ionization spectroscopy has been used to determine the residual donor species present and their relative concentrations in the highest purity molecular beam epitaxial (MBE) n-GaAs yet reported. Data are presented for samples grown in two different MBE growth reactors: one using elemental As and the other using cracked AsH3 as the arsenic source. In spite of the substantial differences between growth systems, the donor backgrounds are quite similar.
Hydrogenation induced improvement in electronic properties of heteroepitaxial silicon-on-sapphire
Authors: Jastrzebski L. , Lagowski J. , Cullen G. W. , Pankove J. I.
Published: February 2003

Photovoltage spectroscopy and laser-scanning photovoltage measurements have been utilized to assess the effect of hydrogenation on electric properties of epitaxial silicon-on-sapphire (SOS) films. It has been found that hydrogenation suppresses deep levels in the middle of the energy gap, and significantly decreases the magnitude of microscopic inhomogeneities. The present results may have implications for SOS electronic devices and demonstrate a relationship between structured defects (dangling bonds) and electronic properties of SOS films.
Effect of oxide precipitates on minority-carrier lifetime in Czochralski-grown silicon
Authors: Miyagi Masami , Wada Kazumi , Osaka Jiro , Inoue Naohisa
Published: February 2003

The effect of oxide precipitate in Czochralski-grown silicon crystals on minority-carrier lifetime was investigated. The oxide precipitates, generated by heterogeneous nucleation in as-grown crystals were found to decrease the lifetime. On the other hand, the oxide precipitates generated by homogeneous nucleation decreased the lifetime when their length was greater than 100 Å. The minority-carrier lifetime was nearly proportional to the reciprocal of the oxide precipitate length.
Niobium nitride-niobium Josephson tunnel junctions with sputtered amorphous silicon barriers
Authors: Jillie D. W. , Kroger H. , Smith L. N. , Cukauskas E. J. , Nisenoff M.
Published: February 2003

Niobium nitride-niobium Josephson tunnel junctions with sputtered amorphous silicon barriers (NbN-αSi-Nb) have been prepared using processing that is fully compatible with integrated circuit fabrication. These junctions are of suitable quality and uniformity for digital circuit and S-I-S detector applications. The junction quality depends critically upon the properties of the NbN surface, and seems to correlate well with the UV/visible reflectivity of this surface.
Production of slow positrons with a 100-MeV electron linac
Authors: Howell R. H. , Alvarez R. A. , Stanek M.
Published: February 2003

Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production mechanism has been studied near 100-MeV incident energy and several characteristics that affect slow-positron production have been identified. These characteristics include the geometry of the electron-positron converter and positron moderator, the thickness of the converter, and the energy of the electron beam. The production efficiency for producing low-energy positrons has been determined experimentally. The results imply that low-energy positron beams from a linac can be of much higher intensity than those beams currently derived from radioactive sources.
Silicon ribbon growth using electron bombardment
Authors: Casenave D. , Gauthier R. , Vandekerkove L. , Pinard P.
Published: February 2003

A method for the production of polysilicon ribbons for solar energy conversion from powder as starting material has been developed. It is based upon the use of an electron beam which, while creating a mobile molten zone on the small grained polycrystalline ribbons, induces the crystallization. These ’’preribbons’’ can be produced directly from silicon powder with the same apparatus. This method is particularly economical because (1) electron beam was used as a means of crystallization (very high energy deposition rate) and (2) as a result of two purification processes peculiar to the method (purification by zone melting and vacuum evaporation), the use of silicon powder of low purity could be envisaged.
Temperature and thickness effects on the explosive crystallization of amorphous germanium films
Authors: Koba R. , Wickersham C. E.
Published: February 2003

Measurements of the interdependence of the thickness and temperature required to support the propagation of explosive crystallization fronts in sputter deposited amorphous germanium films are described. The results indicate that the minimum film thickness and minimum ambient transformation temperature are inversely related. These data support an energy balance model of the explosive crystallization phenomenon.
Codirectional TE-TM mode conversion through codirectional and contradirectional acousto-optic interactions
Authors: Binh L. N.
Published: February 2003

Codirectional TE-TM mode conversion is investigated for the codirectional and contradirectional interaction geometries between optical guided waves and surface acoustic waves in a Ti-diffused optical waveguide. The acoustic input power required for maximum mode conversion of 20 mW has been achieved for both cases. The conversion center frequencies are closely the same for both configurations.
Stimulated emission in a degenerately doped GaAs quantum well
Authors: Holonyak N. , Vojak B. A. , Morkoç H. , Drummond T. J. , Hess K.
Published: February 2003

Data are presented showing that a single GaAs quantum well as small as Lz ≲80 Å can be operated in stimulated emission if supplied sufficiently with electrons, which can be done by doping (ND≳Nc). It is shown, via photoluminescence data and an approximate analysis, that the smaller the GaAs well size Lz (1500, 400, 200, 80 Å) the greater is the effect of a fixed confining layer doping (ND ∼5×1018/cm3) in increasing the quantum-well carrier population and the luminescence energy.
Carrier conduction in thin silicon nitride films
Authors: Suzuki Eiichi , Hiraishi Hisato , Ishii Kenichi , Hayashi Yutaka
Published: February 2003

Carrier conduction in thin chemical vapor deposition (CVD) silicon nitride films in the thickness range 467 Å⩾tN⩾88 Å is investigated. The dominant carriers flowing through the thin nitride films are holes for both polarities. The enormous increase of current with decreasing film thickness can be explained by a thickness fluctuation model. The thickness fluctuation of about 25 Å is obtained in the electrical measurement. This model is confirmed by observing the appearance of microhillocks on the surface of oxidized thin nitride films.
Electrical properties of line defects in thin zone-recrystallized silicon films on silicon dioxide
Authors: Maby E. W. , Antoniadis D. A.
Published: February 2003

The electrical influence of line defects which are present in thin zone-recrystallized silicon films prepared in a movable strip heater oven has been examined in terms of both bulk and surface majority-carrier transport. Large-angle boundaries which separate large (typically 2 mm×1 cm) single-crystalline grains induce significant bulk conductivity degradation and notable surface effects in transversely intersected field-effect transistors. The influence of the majority of line defects which are regularly superimposed over the large grains at approximate 25-μm intervals is relatively minor.
Variable range hopping in Al implanted sapphire
Authors: Hauser J. J. , Rodgers J. W.
Published: February 2003

Variable range hopping conductivity (i.e. resistivity proportional to exp T−1/4) has been observed in Al implanted sapphire. The conductivity of these implanted layers was studied as a function of implanted doses.
Current-phase relationship of granular NbN weak links, inferred from Josephson interferometer characteristics
Authors: Claassen J. H.
Published: February 2003

Small-area dc superconducting quantum interference devices (SQUID’s) were made using ultra-short variable-thickness microbridges of NbN. The bridges had an effective length of ∼500 Å and a width of ∼1.5 μm. Analysis of the response to magnetic flux permits interferences to be drawn about the current-phase relationship (CPR) of the bridges. Contrary to predictions of Ginzburg–Landau theory for microbridges of these dimensions, it is found that the CPR is single valued and probably close to ideal (sinusoidal) over a large temperature range (≳2.5 K). The discrepancy with theory may be due to the granular nature of the NbN films.
Effect of strain on the critical parameters of V2(Hf, Zr) Laves phase composite superconductors
Authors: Wada H. , Inoue K. , Tachikawa K. , Ekin J. W.
Published: February 2003

Strain effects on the critical parameters of composite-processed V2(Hf, Zr) Laves phase superconductors have been examined. The critical temperature is found to be insensitive to the strain induced by the thermal differential contraction between the composite components. Critical current versus uniaxial strain curves obtained are completely flat at magnetic fields up to 19 T. It also turns out that the bulk upper critical field shows essentially no sensitivity to uniaxial strain. These results, which are quite different from those reported for A15 compound superconductors, are discussed in terms of the structural insensitivity of the Laves phase superconductor. Fractography suggests that the mechanical properties of V2(Hf, Zr) composite conductors may be improved by the grain refinement of component alloys.
A comparison of ablative acceleration measurements
Authors: Raven A. , Azechi H. , Nakai M. , Matsuo T. , Yamanaka T. , Yamanaka C.
Published: February 2003

Measurements of foil acceleration by streaked x-ray shadowgraphy are compared with optical shadowgraphy and the ablation pressure measured by layer burnthrough. The latter two show a factor 3–4 discrepancy with the x-ray shadowgraphy.
Microscopic fluorescent imaging of surface temperature profiles with 0.01 °C resolution
Authors: Kolodner Paul , Tyson J. Anthony
Published: February 2003

We have exploited the temperature-dependent fluorescence quantum efficiency in europium thenoyltrifluoroacetonate (EuTTA) to make high-resolution, noncontact temperature measurements on the surface of an integrated circuit chip. The EuTTA is spun onto the chip in a polymer film. The chip is illuminated with long-wave UV light, and the orange fluorescence is imaged onto a charge-coupled-device (CCD) camera. Digital image processing completely removes the optical features in the image, leaving a purely thermal map of the surface temperature profile with a measured temperature resolution of better than 0.01 °C and a spatial resolution of 15 μm. With a different camera and optics, 1-μm resolution should be possible, allowing thermal imaging of the smallest high-speed integrated circuits.
Topographical characteristics of recrystallized silicon films by scanning cw laser irradiation
Authors: Isu Toshiro , Sugahara Kazuyuki , Nishimura Tadashi , Akasaka Yoichi , Nakata Hidehumi
Published: February 2003

Chemical vapor deposited polycrystalline silicon on insulating layer has been crystallized by scanning cw Ar laser irradiation. Recrystallized films have several features in their topographical characteristics. A ridge with periodic humps along the trace of the laser beam scan has been observed remarkably for films thicker than 0.7 μm. It is considered that the surface feature is due to movements of molten silicon during the laser irradiation. In the case of silicon islands recrystallized by laser irradiation after local oxidation of surrounding polycrystalline silicon, a slight depression of a silicon film at the starting side of the island for the laser beam scan and swell at the counter end have been formed. These phenomena are explained by a movement of a molten silicon hump as well as in the case of continuous films.
Transient annealing of selenium-implanted gallium arsenide using a graphite strip heater
Authors: Chapman R. L. , Fan John C. C. , Donnelly J. P. , Tsaur B-Y.
Published: February 2003

A graphite strip heater has been used for transient annealing, at temperatures of 900–1140 °C, of GaAs wafers implanted at 300 °C with a 1×1015 cm−2 dose of 400-keV Se+ ions. The electrical activation of the implant produced by annealing at 1140 °C for 10 s yields a sheet resistivity of 25 Ω/⧠ and sheet carrier concentration of 1.8×1014 cm−2, compared with values of 35 Ω/⧠ and 1.1×1014 cm−2 obtained by conventional furnace annealing at 950 °C for 30 min.
Diffused epitaxial GaAlAs-GaAs heterojunction bipolar transistor for high-frequency operation
Authors: Ankri D. , Scavennec A. , Besombes C. , Courbet C. , Heliot F. , Riou J.
Published: February 2003

A GaAlAs-GaAs heterojunction bipolar transistor (HBT) has been realized by liquid phase epitaxy with a very low emitter doping. A diffused epitaxial structure has been developed. Transition frequencies close to 5 GHz for IC = 10 mA have been measured, and high transition frequency has been obtained at low current ( fT = 1.3 GHz for IC = 1 mA) in spite of a rather large emitter base area (SEB∼4.10−5 cm2). These figures are the best reported so far for HBT’s and are very promising for low-power high-speed logic.
Surface morphology of erbium silicide
Authors: Lau S. S. , Pai C. S. , Wu C. S. , Kuech T. F. , Liu B. X.
Published: February 2003

The surface of rare-earth silicides (Er, Tb, etc.), formed by the reaction of thin-film metal layers with a silicon substrate, is typically dominated by deep penetrating, regularly shaped pits. These pits may have a detrimental effect on the electronic performance of low Schottky barrier height diodes utilizing such silicides on n-type Si. This study suggests that contamination at the metal-Si or silicide-Si interface is the primary cause of surface pitting. Surface pits may be reduced in density or eliminated entirely through either the use of Si substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition and silicide formation or by means of ion irradiation techniques. Silicide layers formed by these techniques possess an almost planar morphology.
Surface etching kinetics of hydrogen plasma on InP
Authors: Tu C. W. , Chang R. P. H. , Schlier A. R.
Published: February 2003

The surface etching kinetics of hydrogen plasma on InP have been studied using Auger electron spectroscopy. It is found that the surface hydrocarbon contamination can be removed with a low power density (15 mW cm−3) of hydrogen plasma. At higher power phosphorus is preferentially removed by the hydrogen atoms in the form of hydrides, leaving the surface rich in In. The excess In is oxidized at high background pressure (∼10−6 Torr) by residual water vapor. However, at low base pressure (≲10−7 Torr) the native oxide (∼10 Å) can be etched away.
A new silicon-on-insulator structure using a silicon molecular beam epitaxial growth on porous silicon
Authors: Konaka Shinsuke , Tabe Michiharu , Sakai Tetsushi
Published: February 2003

A new silicon-on-insulator (SOI) structure has been achieved by utilizing silicon molecular beam epitaxial (Si-MBE) growth on porous silicon, silicon island patterning, and the subsequent laterally enhanced oxidation of the porous silicon. The surface of Si-MBE film grown on porous silicon at 770 °C without high-temperature preheating has a 7×7 superlattice structure when observed by a reflection high-energy electron diffraction (RHEED). Patterned Si-MBE film island, that is 7.0 μm wide and 0.35 μm thick, is successfully isolated by the laterally enhanced oxidation of porous silicon.
A new technique for gettering oxygen and moisture from gases used in semiconductor processing
Authors: Shealy J. R. , Woodall J. M.
Published: February 2003

A technique for the removal of small amounts of water vapor and oxygen from hydrogen and nitrogen is described in which the gas is purified by bubbling it through a gallium-indium- aluminum melt at room temperature. Using this technique, dew points of ⩽−80 °C are achieved when the starting gas contains as much as one part per thousand of water vapor.
Analysis of arsenic and phosphorus ion implanted silicon by spectroscopic ellipsometry
Authors: Cortot J. P. , Ged Ph.
Published: February 2003

Crystalline damage of As+ and P+ ion implanted silicon has been investigated by spectroscopic ellipsometry at wavelengths in the range 325–400 nm. The experimental procedure takes care of the presence of a technology dependent surface layer. The measurements made can be unambiguously associated with crystalline damage and are sensitive to doses as low as two orders of magnitude below the amorphization dose.
Optical response time of In0.53Ga0.47As/InP avalanche photodiodes
Authors: Forrest S. R. , Kim O. K. , Smith R. G.
Published: February 2003

Heterojunction In0.53Ga0.47As/InP avalanche photodiodes have recently been observed to have a response to long-wavelength optical pulses which contains both fast and slow components. We present evidence that the slow response is limited by charge pile-up at the semiconductor heterointerface. We find that the speed of response depends on the degree of compositional grading in the heterointerface region. The response time can be significantly reduced for compositional grading lengths of greater than 600 Å depending on the doping and depletion region width in the In0.53Ga0.47As layer.
Chemical bonding of W-Si compounds
Authors: Akimoto K.
Published: February 2003

The chemical bonding of W-Si compounds formed by plasma chemical vapor deposition [WSi (PD)] and hot pressing [WSi (HP)] was investigated by x-ray photoelectron spectroscopy and Si-Kβ emission spectroscopy. Some apparent chemical effects on the spectra of these W-Si compounds were observed and can be reasonably interpreted by a model in which chemical bonding between the W and Si atoms consists of a major σ donation and a minor π back donation. The chemical effects suggest that the bonding between the W and Si atoms in WSi(HP) is stronger than that in WSi (PD).
Acoustic wave propagation on indium phosphide surfaces
Authors: Henaff Jeannine , Feldmann Michel , Carel Michel , Dubois Reneé
Published: February 2003

In view of combined use of piezoelectric and semiconducting properties of indium phosphide, new surface (SAW) and surface skimming bulk waves (SSBW) are described. The properties of semi- insulating InP crystals are investigated in terms of piezoelectric coupling demonstrating that the SSBW branches may be more useful than the SAW branches. Two Rayleigh modes and one Bleustein–Gulyaev branch have been experimentally investigated in the 200–300-MHz range and good agreement between theory and experiment is reported.
Parametric amplification of surface acoustic wave of ZnO-Ga-doped yttrium iron garnet
Authors: Inaba R. , Mikoshiba N.
Published: February 2003

Interactions of surface acoustic wave (SAW) with magnetization are investigated on a ZnO-Ga- doped yttrium iron garnet (YIG) and GGG structure. The attenuation of SAW depends on the input power of SAW due to a nonlinear interaction with the magnetization of the YIG. Parametric amplification of SAW is closely related to the magnetic field strength and the input power. The amplification gain is 5.1 dB at 180 MHz, the magnetic field strength is 9 Oe, and the input power is −5 dBm.
Mass transport in laser surface alloying: Iron-nickel system
Authors: Chande T. , Mazumder J.
Published: February 2003

The role of fluid flow in producing uniformly alloyed beads in laser surface alloying is examined and the experimental finding that the uniformity of alloying increased with a decrease in the beam diameter is analyzed. Fluid flow can dominate the process of solute redistribution in the melt pool by producing a fine dispersion of solute rich pockets. The fineness of the scale is estimated and found to compare favorably with the experimentally measured scale of local fluctuations in composition. It is found that the magnitude of the surface tension gradients is primarily dependent upon the magnitude of the surface temperature gradients. This can be used to estimate the effect of process parameters on the vigor of the fluid flow in the pool, which controls the process of mass transport in laser surface alloying.
Picosecond electron diffraction
Authors: Mourou Gerard , Williamson Steve
Published: February 2003

A picosecond photoelectron pulse generated by a streak camera has been used to probe a thin film of aluminum producing a diffraction pattern representative of its lattice structure. Because this photoelectron pulse is in picosecond synchronism with the optical pulse, this technique will make possible the investigation of structural phase transitions in the picosecond time domain.
Polariton-induced compensation of pulse broadening in optical fibers
Authors: Fehrenbach G. W. , Salour M. M.
Published: February 2003

We report the first experimental technique for compensating the pulse broadening in single-mode optical fibers, using the ’’slow’’ anomalous pulse propagation in the exciton-polariton resonance in a direct-gap semiconductor. Mode-locked dye laser pulses of 0.7-ps duration at 8180 Å were propagated through a 100-m single-mode optical fiber and emerged with 2.8-ps duration. We have demonstrated the compensation of this pulse broadening in optical fibers by passage through a 6.3-μm-thick GaAs crystal, taking advantage of the group velocity dispersion around the discrete n = 1 exciton-polariton resonance.
Picosecond carrier dynamics and laser action in optically pumped buried heterostructure lasers
Authors: Koch T. L. , Chiu L. C. , Harder Ch. , Yariv A.
Published: February 2003

We report the observation of picosecond optical pulses and unusual pulse structures from optically pumped buried heterostructure semiconductor lasers. A model which considers the hot electron and hole energy distributions dynamically accounts well for our experimental findings. The results are relevant to the problem of the limiting response time of semiconductor lasers.
Remote temperature measurement using an acoustic probe
Authors: Husson D. , Bennett S. D. , Kino G. S.
Published: February 2003

We describe the preliminary results of a novel method for the noninvasive measurement of temperature distribution within a solid body using an acoustic beam. Applications of such a scheme could include the control and assessment of tumor treatment by hyperthermia in which small regions of tissue deep within the body are heated by either acoustic or microwave energy. A major practical difficulty in such a process is the accurate determination of the temperature distribution. The scheme we describe in this letter appears to be capable of detecting temperature differences with a sensitivity of a few tenths of a degree centigrade and with a spatial definition of the order of 1 cm3. The basic technique in which the phase differences between two colinear acoustic beams, one broad and collimated and the other focused, are compared electronically, is described, and results obtained with a tissue phantom are used to illustrate the viability of the approach.
Depth distributions and range parameters for He implanted in Si and GaAs
Authors: Wilson R. G. , Deline V. R. , Hopkins C. G.
Published: February 2003

Depth distributions for He implanted in Si and GaAs measured by secondary ion mass spectrometry (SIMS) are reported as a function of ion energy from 20 to 300 keV at 1016 cm−2 fluence. The range parameters and Pearson IV moments are determined and tabulated. The ranges of 300-keV He ions in both Si and GaAs are about 1.4 μm but the width of the profiles is greater for GaAs (σ=0.273 μm) than for Si (σ=0.140 μm). The profiles for all energies in both materials exhibit significant negative skewness (γ1≊−1.65). The SIMS detection limit for He is about 1018 cm−3 in both Si and GaAs. Implanted He depth distributions do not redistribute until an annealing temperature of 350 °C is reached.
Crystal orientation dependence of silicon autocompensation in molecular beam epitaxial gallium arsenide
Authors: Ballingall J. M. , Wood C. E. C.
Published: February 2003

Silicon-doped GaAs has been grown simultaneously on (100), (110), and (111)B oriented GaAs substrates by molecular beam epitaxy. For constant Si, Ga, and As4 fluxes the surface morphology of the (110) and (111)B faces degraded with increasing substrate temperature above ∼500 °C. (100) films had an n-type free-electron concentration of 5×1016 cm−3 independent of substrate temperature. Films on (110) substrates were p type when grown above ∼550 °C and n type below ∼550 °C whereas (111)B films were highly resisitive under most growth conditions. Low-temperature (4 K) photoluminescence showed good correlation between the Si acceptor peak heights and the compensation ratios derived from electrical measurements.
Bipolar transistor action in ion implanted diamond
Authors: Prins J. F.
Published: February 2003

Using a natural type IIb diamond, which is p-type semiconducting, as a substrate material, and implanting this diamond with carbon ions to induce n-type regions, diode and bipolar transistor action could be obtained. Owing to the geometrical positions of the collector, base, and emitter, which in this case were lateral to the surface, very low current gain was obtained. However, the results indicate that an improvement in the geometry will probably lead to a diamond transistor of high gain.
Sub-50-nm lithography in amorphous Se-Ge inorganic resist by electron beam exposure
Authors: Singh B. , Beaumont S. P. , Bower P. G. , Wilkinson C. D. W.
Published: February 2003

Ag2Se/Se90Ge10 inorganic resist has been used to produce sub-50-nm lines by electron beam lithography. 35–50-nm-wide lines have been defined by wet chemical processing in 70-nm-thick Se-Ge resist supported on a 50-nm silicon nitride membrane. The effects of different chemical etchants on resolution are described.
Highly conductive and transparent zinc oxide films prepared by rf magnetron sputtering under an applied external magnetic field
Authors: Minami T. , Nanto H. , Takata S.
Published: February 2003

Highly conductive films of zinc oxide have been prepared by rf magnetron sputtering deposition on a substrate suspended perpendicular to the target under an applied external magnetic field in pure argon gas. It is shown that a film with low resistivity (5×10−4 Ω cm) and high optical transmission (>85% between 400 and 800 nm) can be produced on low-temperature substrates with a relatively high deposition rate. The sheet resistance and Hall mobility of the film are 10 Ω/⧠ and 120 cm2/Vs respectively. The high conductivity is achieved by an increase in Hall mobility due to improved crystallization.
Raman scattering characterization of Ga1−xAlxAs/GaAs heterojunctions: Epilayer and interface
Authors: Parayanthal P. , Pollak Fred H. , Woodall J. M.
Published: February 2003

We have used Raman spectroscopy to characterize Ga1−xAlxAs/GaAs heterojunctions (x≊0.9) grown by liquid phase epitaxy. The GaAs substrate had a (100) surface and the Ga1−xAlxAs epilayer was about 5000 Å thick. Signals were observed from both the Ga1−xAlxAs epilayer and the GaAs substrate at the interface. Information about the quality of the epilayer can be gained from several aspects of the spectrum including linewidths, violations of polarization selection rules (e.g., observation of symmetry forbidden TO mode), and the amplitude of the disorder-activated LA mode (DALA). These results are correlated with the properties of the substrate and growth condition. In addition the signal observed from the GaAs substrate revealed interesting features such as coupled plasmon modes and hence yielded information about band- bending and dopant diffusion at the interface.
Self-annealed ion implanted solar cells
Authors: Gabilli E. , Lotti R. , Merli P. G. , Nipoti R. , Ostoja P.
Published: February 2003

Self-annealing implantation with dopant ions has been successfully applied to the fabrication of silicon solar cells. Experimental conditions as well as solar cell parameters are presented and discussed.
High-temperature resistivity of Cr-doped epitaxial GaP
Authors: Fritz I. J. , Biefeld R. M. , Hughes R. C.
Published: February 2003

Epitaxial layers of Cr-doped GaP have been grown by metalorganic chemical vapor deposition. The layers were characterized by capacitance and current-voltage (I-V) measurements on Schottky-barrier structures, and by I-V measurements on layers with alloyed ‘‘quasi-ohmic’’ contacts. A high degree of compensation was achieved, and resistivities of up to 106 Ω cm were measured. The temperature dependence of the resistivity was measured up to 475 °C, and analysis of the results indicates two high-temperature activated processes, with activation energies of 0.13 and about 1.0 eV. This material may be useful in GaP high-temperature device technology.
Reversible photoinduced changes in the low-temperature photoconductivity of hydrogenated amorphous silicon
Authors: Vanier P. E.
Published: February 2003

Exposure of intrinsic glow-discharge hydrogenated amorphous silicon films to white light at an intensity of 100 mW cm−2 for several hours induces changes in the temperature dependence of photoconductivity. These changes, which are reversed by heating to 200 °C, can be explained by an increase in the density of states in the lower half of the gap. The new states are different from the two types of states previously inferred from the temperature dependence of photoconductivity.
Observation of an electronic plasma in picosecond laser annealing of silicon
Authors: von der Linde D. , Fabricius N.
Published: February 2003

Changes of the optical reflectivity and transmission of Si during and after annealing with a 25-ps laser pulse at 532 nm are measured with 10-ps resolution. The reflectivity exhibits an initial minimum—which is attributed to the electron-hold plasma—followed by a jump to a value equal to the reflectivity of liquid Si. Below a well-defined threshold of (0.21±0.01) J/cm2 only the plasma effect is observed.
Lattice incorporation of n-type dopants in GaAs
Authors: Rai A. K. , Bhattacharya R. S. , Pronko P. P.
Published: February 2003

Transmission electron microscopy has been used to investigate precipitates of the n-type dopants S, Si, Se, and the deep acceptor Cr implanted in GaAs and annealed in the temperature range 800–900 °C. The lowest precipitation was observed for S and Si (4–5%) followed by Se (∼12%). Bulk precipitation was observed for Cr. These results are found to correlate inversely with the percentage substitutionality of S, Si, and Cr measured by the technique of proton induced x-ray excitation in combination with Rutherford backscattering channeling.
Transient photoacoustic monitoring of pulsed laser drilling
Authors: Yeack C. E. , Melcher R. L. , Klauser H. E.
Published: February 2003

A noncontact transient photoacoustic technique has been developed to monitor a pulsed laser drilling process. Applicaton to the drilling of holes in a composite epoxy-glass material is presented.
Operating efficiencies in pulsed carbon dioxide lasers
Authors: Smith A. L. S. , Mellis J.
Published: February 2003

Computer models of the CO2-N2-He laser system usually predict that 20%–33% of the discharge energy should be available as radiation output. Using a comprehensive kinetics model to study vibrational temperatures and stored energies, we find a deterioration in laser efficiency with increasing input energy, due to electron superelastic losses during the excitation pulse. Experimental observations support the calculated vibrational temperatures and likewise our predicted 8%–12% yield efficiency at optimum excitation is in good agreement with the values realized in working lasers.
High resolution photoacoustic microscopy on a surface acoustic wave device
Authors: Veith G.
Published: February 2003

Photoacoustic imaging of microscopic metal film test structures on a surface acoustic wave device at 76-MHz light modulation frequency is reported. The samples are evaporated on a YZ LiNbO3 crystal surface and are scanned through the focus spot of a mode-locked dye laser beam. The optically generated surface acoustic waves are detected by means of a resonant interdigital transducer. Synchronization of the focus spot position to the corresponding piezoelectric signal yields a high resolution photoacoustic image of the samples (lateral resolution 5 μm).
A two-dimensional phase separation on the spherical surface of the metallic glass Au55Pb22.5Sb22.5
Authors: Lee Mark C. , Johnson William L.
Published: February 2003

Recent experiments indicate that a phase separation in a spherical sample of the metallic glass Au55Pb22.5Sb22.5 occurs near the surface of the sphere. This strongly suggests either a contribution of surface-free energy to the decomposition process or a possible influence of near surface impurities absorbed during synthesis of the sphere. The surface phase separation has been studied as a function of cooling rate of the sphere. At high cooling rates (small sphere sizes), the surface separation disappears altogether suggesting that the surface of the parent liquid droplet is initially homogeneous.
Influence of hot carriers on the temperature dependence of threshold in 1.3-μm InGaAsP lasers
Authors: Etienne B. , Shah Jagdeep , Leheny R. F. , Nahory R. E.
Published: February 2003

Carrier heating effects are shown to contribute significantly to temperature sensitivity of threshold current in InGaAsP 1.3-μm lasers. For the empirical expression Jth∼J0 exp(T/T0), a single value of T0=90 K describes the data for 100 K<TL<350 K when T is taken to be the carrier temperature. This result is in contrast to the variation in T0 from 90 to 60 K found when T is taken to be the lattice temperature.
High quantum efficiency InGaAsP/InP lasers
Authors: Tamari N. , Oron M. , Miller B. I. , Ballman A. A. , Nahory R. E. , Martin R. J. , Shtrikman H. , Coldren L. A.
Published: February 2003

Liquid phase epitaxial grown Cd-doped InGaAsP/InP double-heterostructure stripe lasers were found to yield very high external differential quantum efficiency, ηext ∼74% in relatively long cavity lasers compared to that of our Zn-doped ones. Since Cd was found to diffuse only slightly into the active layer, the high ηext as well as the lower threshold current in the Cd-doped lasers are attributed to lower concentration of nonradiative recombination centers. The broad area lasers have lower ηext than the respective stripe lasers. Moreover, ηext is insensitive to the heat sink temperature in the range 20–70 °C in the stripe lasers while it drops considerably in the broad area ones.
Trapping parameters of dangling bonds in hydrogenated amorphous silicon
Authors: Street R. A.
Published: February 2003

The mobility, lifetime, and capture cross sections for the trapping of electrons and holes at dangling bond defects in a-Si:H are measured using time-of-flight transient photoconductivity. The magnitude obtained for the product μτNs is 3.5×108±25% cm−1 V−1 and 4×107±50% cm−1 V−1 for electrons and holes, respectively. The capture cross section is 4×10−15 cm2 for electrons and about 2×10−15 cm2 for holes. The results are consistent with the amphoteric nature of neutral dangling bonds.
Heteroepitaxial growth of Ge on 〈111〉 Si by vacuum evaporation
Authors: Garozzo M. , Conte G. , Evangelisti F. , Vitali G.
Published: February 2003

The heteroepitaxial growth of Ge on 〈111〉 Si substrates has been obtained by thermal and electron gun evaporation in the deposition temperature range 375–425 °C. Reflection high-energy electron diffraction analysis shows that the films are 〈111〉 oriented and exhibit high crystalline quality with no evidence of twins. It was also found that the films are p type with the same mobility as bulk Ge single crystals.
Transfer doping effects at the organometallic vapor phase epitaxial AlxGa1−xAs-substrate GaAs interface
Authors: Matsumoto Takashi , Bhattacharya Pallab K. , Darmawan Johan , Ludowise M. J.
Published: February 2003

Electron mobilities in Alx Ga1−xAs (0.1≤x≤0.6) crystals grown by organometallic vapor phase epitaxy on semi-insulating GaAs:Cr have been measured and analyzed. The mobilities are an order of magnitude higher than theoretical predictions, or those obtained in liquid phase epitaxial Alx Ga1−xAs for x≥0.4. The expected lower mobilities are, however, obtained when measurements are made on the epitaxial layer with the substrate removed. A persistent photoconductivity effect is observed at low temperatures in the layers with substrates. The present results indicate that transfer doping is operative at the epilayer-substrate heterointerface.
Structural phase transitions of indium/indium oxide thin-film composites
Authors: Hebard A. F. , Nakahara S.
Published: February 2003

Correlation of resisitivity measurements with transmission electron microscopy analysis reveals that indium/indium oxide thin films, prepared by reactive ion-beam sputter deposition, undergo pronounced and heretofore unrecognized structural phase transitions as a function of increasing oxide content. We have found that these films can be fabricated in a reproducible manner with microstructure characterized as either granular, with crystalline grains embedded in crystalline oxide, amorphous, or mixed amorphous and crystalline.
Charge carrier generation, transport, and trapping in a photoconductive conjugated polymer: Polyphenylacetylene
Authors: Kang E. T. , Ehrlich P. , Bhatt A. P. , Anderson W. A.
Published: February 2003

Dark currents and photocurrents were measured in 3–6-μm-thick films of polyphenylacetylene (PPA) and of iodine-doped PPA. In undoped PPA, Schottky–Richardson injection from the electrodes is observed and holes are strongly trapped. Defect states exert a major control over dark currents and photocurrents. The photoconductivity action spectrum shows a good response in the red at energies well below the absorption edge. We conclude that undoped PPA is capable of trap-modulated electron transport through states in the band gap. Doping with iodine enhances photocurrents through charge transfer interaction.
Electronic and optical properties of amorphous Si:H films deposited by chemical vapor deposition
Authors: Akhtar M. , Dalal V. L. , Ramaprasad K. R. , Gau S. , Cambridge J. A.
Published: February 2003

Doping properties, optical absorption, and infrared (IR) spectra of amorphous Si:H(a-Si:H) films prepared by chemical vapor deposition (CVD) of Si2H6 are reported. The optical absorption curves are very sharp and they indicate that the band gap of CVD a-Si:H can be changed substantially by varying the deposition temperature. A band gap of 1.5 eV has been achieved. IR spectra indicate the presence of Si–H and SiH2 bonds, but H content is less than in device-quality glow-discharge deposited a-Si:H. The activation energy of undoped films is 0.6 eV. n-type doping can be achieved by PH3 doping and the activation energy reduces to 0.12 eV upon doping. Photoinduced changes in electron trapping (Staebler–Wronski effect) are small in CVD a-Si:H films.
Amorphous-silicon charge-coupled devices
Authors: Kishida Satoru , Nara Yasuo , Kobayashi Osamu , Matsumura Masakiyo
Published: February 2003

Amorphous-silicon charge-coupled devices have been proposed and demonstrated for the first time. The cross section is of a silicon-oxynitride/amorphous-silicon/silicon-oxynitride structure sandwiched between staggered transfer electrodes. Electrons are transferred along the amorphous-silicon film with a serpentine motion. The prototype device fabricated on a glass substrate had a transfer inefficiency of as low as 0.4% transfer at 0.5–1-kHz clock frequencies.
Very high frequency GaAlAs laser field-effect transistor monolithic integrated circuit
Authors: Ury Israel , Lau Kam Y. , Bar-Chaim Nadav , Yariv Amnon
Published: February 2003

A very low threshold GaAlAs buried heterostructure laser has been monolithically integrated with a recessed structure metal-semiconductor field-effect transistor on a semi-insulating substrate. At cw operation, the device has a direct modulation bandwidth of at least 4 GHz.