bluuebunny/crossref_metadata_2025 huggingface dataset:
Positive charge generation in thin SiO2 films during nitridation process
Authors: Pan Paihung , Paquette Charles
Published: July 2002

Thin SiO2 films, ranging from 5 to 15 nm in thickness, were annealed in NH3 (99.999%) in a polycrystalline silicon reactor. Generation of positive charge during the initial period of nitridation was found. Large negative flatband (ΔVfb) shift (∼0.56 V) was found for films annealed in NH3 for short periods of time (10 min). The amount of capacitor-voltage (C-V) shift decreased sharply as the annealing time increased from 10 to 30 min and then decreased very slowly for annealing time >30 min. The value of the initial negative flatband shift (10 min annealing) increased with increasing SiO2 film thickness. Generation of positive charge near the SiO2/Si interface during the initial period of nitridation is proposed. From the amount of C-V and current-voltage (I-V) shifts, a charge density of 2×1011 cm−2 and a charge center ∼2.4 nm away from the SiO2/Si interface were estimated for the 10-nm SiO2 films annealed in NH3 for 10 min.
Secondary implantation of Sb into Si molecular beam epitaxy layers
Authors: Jorke H. , Herzog H.-J. , Kibbel H.
Published: July 2002

We report on the influence of low-energy Si+ ions on the incorporation of Sb adatoms existing on growing (100) Si molecular beam epitaxy layers. At a growth temperature of 650 °C employed for these experiments an increase of incorporation of about three orders of magnitude compared to the spontaneous incorporation is obtained at ion flux densities of typically 1012 cm−2 s−1. Dopant activation coefficients of almost unity are established up to 1019 cm−3. The number of incorporated adatoms is found to increase proportionally with preadjusted adatom density as well as with Si+ ion dose. At an ion energy of 500 eV the constant of proportionality is estimated to be σI =(5±2)×10−16 cm2.
Quantitative measurements of the stoichiometry of anodic oxides grown on Hg0.78Cd0.22Te
Authors: Stahle C. M. , Thomson D. J. , Helms C. R. , Becker C. H. , Simmons A.
Published: July 2002

The Hg concentration in anodic oxides grown on Hg0.78Cd0.22Te has been measured by Rutherford backscattering and surface analysis by laser ionization techniques. A significant Hg content is found, and this result is contrasted with previous compositional studies which have concluded that a very low Hg concentration exists in the anodic oxide grown on Hg1−xCdxTe. In addition, a model reaction is proposed which suggests that Hg and Te are dissolved in the anodizing solution to a much greater extent than Cd during the oxidation process.
Effect of Fe on the carrier instability in HgSe
Authors: Vaziri M. , Debska U. , Reifenberger R.
Published: July 2002

The variation in the electron carrier concentration as a function of annealing conditions in HgSe, Hg1−xMnxSe, and Hg1−xFexSe has been studied. Our results show that the carrier concentration in the Hg1−xFexSe system with x≥0.003 is very stable and shows little or no change under various annealing conditions. Measurements of the Dingle temperature from Shubnikov–de Haas oscillations, in addition to Hall mobilities determined at 4.2 K, indicate a significantly longer collision time for the conduction electrons in Hg1−xFexSe for x<0.03 than in samples of HgSe with the same electron concentration.
Perimeter-related current in high-field tunneling into SiO2
Authors: Hook Terence B. , Ma T. P.
Published: July 2002

The spatial distribution of the electric field in a metal-oxide-silicon structure with finite gate dimensions is calculated and used to determine the current expected in the Fowler–Nordheim tunneling regime. The theoretical analysis predicts a greatly enhanced perimeter current when the gate acts as the cathode. In contrast, the edge of the gate does not significantly influence the current when the silicon substrate acts as the cathode. Experimental results are in qualitative agreement with the above expectation.
Formation of low defect density SiOx films for Josephson integrated circuits
Authors: Shibayama H. , Hasuo S. , Yamaoka T.
Published: July 2002

SiOx films deposited by evaporation under oxygen atmosphere were investigated to form low defect density insulating layers in Josephson integrated circuits. The defect density is high in SiOx films deposited under an oxygen pressure of less than 1.33×10−3 Pa, but it decreases greatly in films deposited under higher oxygen pressure. This can be explained by the presence or absence of elemental Si in the films. Elemental Si is present in films deposited under low oxygen pressure, but not in films deposited under higher oxygen pressure. The insulating characteristics of a SiOx film deposited under an oxygen pressure of 1.33×10−2 Pa are excellent.
Pulse broadening of laser oscillation on the 4p 2P3/2–4s2 2D5/2 transition in the neutral copper atom by cesium vapors
Authors: Saito Hiroshi , Taniguchi Hiroshi
Published: July 2002

Experiments were carried out in order to quench the population of copper atoms in the lower laser levels [4s2 (2D5/2); metastable states] of the neutral copper atom through an energy transfer process by introducing the cesium vapors into a laser tube.
4×4 Ti:LiNbO3 integrated-optical crossbar switch array
Authors: McCaughan L. , Bogert G. A.
Published: July 2002

We have fabricated the largest integrated optical switch array to date—a square array of 16 interconnected Ti:LiNbO3 directional coupler electro-optical switches. The devices operate at ∼11 V and have 4.6–15-dB fiber-device-fiber insertion loss and extinction ratios from −12 to >−35 dB.
Free-exciton luminescence in GaSb quantum wells confined by short-period AlSb-GaSb superlattices
Authors: Ploog K. , Ohmori Y. , Okamoto H. , Stolz W. , Wagner J.
Published: July 2002

Photoluminescence and photoluminescence excitation measurements at temperatures ranging from 4 to 300 K were performed on 9.2-nm GaSb quantum wells confined by AlSb-GaSb short-period superlattices. In the temperature range 4–200 K the photoluminescence from the high-quality molecular beam epitaxially grown samples is dominated by free-exciton emission. This assignment is confirmed by photoluminescence excitation spectroscopy which reveals an energy separation of 11.5 meV between n=1 heavy-hole and n=1 light-hole free excitons for the 9.2-nm wells. At low temperatures the photoluminescence line is shifted by only 7.5 meV to low energy from the heavy-hole excitonic peak observed in the excitation spectrum. This small value of the Stokes shift indicates the absence of impurity-related trapping of excitons.
New shallow acceptor levels in neutron-irradiated Si:Ga
Authors: Fischer David W. , Mitchel W. C.
Published: July 2002

Fourier transform infrared absorption spectroscopy has been used to reveal the presence of two previously unknown shallow acceptor levels formed by neutron irradiation of Si:Ga. Absorption peaks corresponding to the strongest lines of groups III-like acceptor spectra were observed and were determined to originate from ground states with binding energies of 42.4 and 56.3 meV. These levels are designated A3 and A4, respectively. The annealing behavior of both levels is discussed and compared to other known shallow acceptor levels created in neutron-irradiated Si:Ga.
Hydrogen depth profiles in ion implanted magnetic bubble garnets
Authors: Leiberich A. , Wolfe R.
Published: July 2002

The hydrogen depth profiles of ion implanted magnetic bubble garnet films have been measured by elastic recoil analysis using 44 MeV chlorine ions. The garnets were triply implanted with Ne, N, and H and were then annealed with or without a surface coating of SiO2. At 250 °C, H was found to diffuse throughout the damaged surface layer but not into the underlying undamaged material. At 350 °C, H diffused out of the uncoated garnet, but was sealed into the implant damaged layer by the thin oxide coating. The deposition of the oxide layer at low temperature after implantation but before processing resulted in a constant H concentration profile extending throughout the implant damaged region of the bubble garnet. This retention of hydrogen correlates with previously reported improvements in propagation behavior of oxide coated ion implanted bubble devices.
Rapid thermal annealing of Si implanted GaAs for power field-effect transistors
Authors: Kanber H. , Henderson W. B. , Rush R. C. , Siracusa M. , Whelan J. M.
Published: July 2002

Rapid thermal annealing (RTA) for the electrical activation of 300-keV Si+ implants in GaAs at doses of (6–8) ×1012 cm−2 is shown to be superior to conventional annealing. Higher gateless field-effect transistor saturation currents and greater uniformities of the saturation current were measured as well as higher peak electron concentrations and mobilities. The advantages of RTA for the removal of ion implantation damage in GaAs are attributed to the heating rate being two orders of magnitude greater than that for furnace annealing. Characteristics are given for single- and four-cell GaAs power metal-semiconductor field-effect transitions fabricated using the above implant and optimized RTA conditions. A 1-μm gate length by 2400-μm gate width device has demonstrated an output power of 1.73 W with 4.9 dB associated gain, 30% power-added efficiency, and 8.1 dB linear gain at 10 GHz.
Bistable optical behavior of a nonlinear attenuated total reflection device: Resonant excitation of nonlinear guided modes
Authors: Reinisch R. , Arlot P. , Vitrant G. , Pic E.
Published: July 2002

We study the prism excitation of a nonlinear waveguide. The nonlinear medium is the substrate which exhibits Kerr effect. Our results show that such a device experiences optical bistability. We also show that there exists a close link between optical bistability and resonant excitation of nonlinear guided modes propagating along this nonlinear waveguide.
Potential material for electroluminescence devices in the visible region
Authors: Joshi N. V. , Ray S. , Menk G.
Published: July 2002

High intensity photoluminescence response has been observed in the visible region (λ=600 nm) in a diluted magnetic semiconductor system Zn1−xMnxS (0.05≤x≤0.4) at 300 and 77 K for the first time. The temperature and concentration independent position of the observed peak can be attributed to the intraionic transition of Mn++. Considering the crystal field splitting parameter and Racah’s coefficient and using the diagram proposed by Y. Tanabe and S. Sugano [J. Phys. Soc. Jpn. 9, 753 (1954)], the luminescence transition responsible for the observed peak was found to be 4T1–6A1. On the basis of high luminescence response, Zn1−xMnxS could be a promising material for electroluminescence devices in the range where photopic response of the human eye is nearly maximum.
Elastic waves propagation in polycrystalline media: A causal response
Authors: Beltzer Abraham I. , Brauner Neima
Published: July 2002

An extremely simple closed-form solution is derived for harmonic waves of an arbitrary frequency propagating in polycrystalline materials. The method applied treats the coherent wave as a causal response of a linear system. A satisfactory agreement with available numerical results is shown.
Picosecond optoelectronic measurement of microstrip dispersion
Authors: Cooper Donald E.
Published: July 2002

The broadening and distortion of 5-ps electrical pulses propagating on microstrip lines were measured. The dispersion curve of the microstrip was measured with a 150-GHz bandwidth. Comparison with an approximate analytical dispersion formula indicates that the microstrip is much less dispersive than expected.
A photoluminescence study of molecular beam epitaxy grown CdTe films on (001)InSb substrates
Authors: Feng Z. C. , Mascarenhas A. , Choyke W. J. , Farrow R. F. C. , Shirland F. A. , Takei W. J.
Published: July 2002

The radiative defect density ρ, as determined by high-resolution, low-temperature photoluminescence, was determined for 11 single crystal films of CdTe grown by molecular beam epitaxy on (001) InSb in the temperature interval 170–285 °C. A minimum of 0.6% is found for ρ near 185 °C as compared to 2.5% for the best previously reported value, indicating a high degree of perfection for our films. X-ray double-crystal rocking curves have also been obtained for these films, and a minimum in the full width at half-maximum is also found in the neighborhood of 185 °C.
Intracavity nearly degenerate four-wave mixing in a (GaAl)As semiconductor laser
Authors: Nakajima Hisao , Frey Robert
Published: July 2002

Intracavity nearly degenerate four-wave mixing has been demonstrated by injecting a low intensity probe beam of frequency ω−δω inside a (GaAl)As semiconductor laser operating above threshold at the pump frequency ω. Conjugated reflectivities as high as 5000 together with a 25% energy conversion efficiency are reported with only a few milliwatt pump power. Additional peaks related to the ac stark effect have been observed at a detuning which depended on the pump power. This process could be useful for the study of instabilities occurring in lasers as well as for optical amplification in laser diodes.
Growth of an epitaxial insulator-metal-semiconductor structure on Si by molecular beam epitaxy
Authors: Phillips Julia M. , Augustyniak W. M.
Published: July 2002

We report the first successful growth of an epitaxial insulator-metal-semiconductor structure. The substrate is Si (111), on which a layer of CoSi2 followed by a layer of CaF2 have been grown by molecular beam epitaxy. The epitaxy of the top CaF2 layer improves upon rapid thermal annealing. The epitaxial relations of the two overlayers with respect to the substrate have been determined. The lattice of the CoSi2 is rotated 180° with respect to the Si lattice, while the CaF2 is aligned with the Si lattice. This work demonstrates that it is possible to combine these materials in a single heteroepitaxial structure and may have important applications in three-dimensional integration.
Raman scattering from ZnTe-ZnSe strained-layer superlattices
Authors: Nakashima S. , Nakakura Y. , Fujiyasu H. , Mochizuki K.
Published: July 2002

Raman scattering measurements have been made to determine the elastic deformation in ZnTe-ZnSe strained-layer superlattices grown by hotwall epitaxy. Both ZnSe- and ZnTe-like modes have been observed, which confirms the formation of a superlattice in the multilayer system having a large lattice mismatch between host layers. We observe that the frequencies of the ZnSe-like longitudinal and transverse phonon modes vary strikingly with the relative thickness of ZnTe and ZnSe layers. This effect is fully accounted for by uniform misfit strains which accommodate the lattice mismatch of the host.
Magnetically tunable diluted magnetic semiconductor (Cd, Mn)Te quantum well laser
Authors: Isaacs E. D. , Heiman D. , Zayhowski J. J. , Bicknell R. N. , Schetzina J. F.
Published: July 2002

We report the first observation of strong magnetic field tuning of laser emission from Cd1−xMnxTe/Cd1−yMnyTe multiple quantum well structures. The spectral peak of the stimulated emission shifts to lower energy with increasing field at a rate of 3.4 meV/T to a maximum shift of 34 meV at 10 T. This is about five times slower than in bulk Cd1−xMnxTe with a comparable x value. Stimulated emission was observed for samples cooled to 1.9 K when optically pumped with a Nd:YAG laser.
In-phase locking in diffraction-coupled phased-array diode lasers
Authors: Wang Shyh , Wilcox Jaroslava Z. , Jansen Michael , Yang Jane J.
Published: July 2002

Design criteria are presented for strong in-phase coupling of diffraction-coupled phased-array diode lasers. Theoretical predictions are confirmed by our experimental observations of double-lobe and single-lobe far-field patterns.
Influence of the circuit impedance on an electron beam controlled diffuse discharge with a negative differential conductivity
Authors: Schaefer G. , Schoenbach K. H. , Kristiansen M. , Strickland B. E. , Korzekwa R. A. , Hutcheson G. Z.
Published: July 2002

The use of attaching gases in an externally sustained diffuse discharge opening switch with a low attachment rate at low values of E/N and a high attachment rate at high values of E/N allows the discharge to operate with low losses in the closed switch phase and to achieve fast opening after the sustainment source is turned off. Such an attacher generates a J-E/N characteristic with a negative differential conductivity in an intermediate E/N range. Such a characteristic obstructs the closing process of the discharge if it is operated in a high impedance system. Experiments demonstrating these effects are presented for electron beam sustained discharges in mixtures of argon and C2F6.
Monolithic GaAs/AlGaAs diode laser/deflector devices for light emission normal to the surface
Authors: Windhorn T. H. , Goodhue W. D.
Published: July 2002

Light emission normal to the surface of a GaAs/AlGaAs wafer has been obtained by fabricating edge-emitting double-heterostructure diode lasers with a monolithic 45° deflector adjacent to one of the laser facets. The deflector and adjacent facet were formed by ion beam assisted etching, while the other facet was cleaved. Diode laser/deflector devices with two etched laser facets could be used to fabricate monolithic two-dimensional laser arrays.
Analysis of the far-field output angle scanning by injection locking of a diode laser array
Authors: Weber Jean-Pierre , Wang Shyh
Published: July 2002

We present a linear theory to explain the experimentally observed emission angle scanning of an injection-locked diode laser array when the frequency of the injected light is changed. This theory is based on eigenmode analysis of the coupled waveguides and on the use of the antenna array theory for the far-field pattern. The experimental results are explained in terms of the resonant excitation of eigenmodes, which selects the far-field pattern associated with the resonant mode. The agreement with published results is good.
Observation of alternating reconstructions of silicon (001) 2×1 and 1×2 using reflection high-energy electron diffraction during molecular beam epitaxy
Authors: Sakamoto T. , Kawamura T. , Hashiguchi G.
Published: July 2002

Layer-by-layer alternating surface reconstructions of Si(001) 2×1 and 1×2 have been observed for the first time using reflection high-energy electron diffraction (RHEED) during molecular beam epitaxy. RHEED intensity oscillations of the specular beam and two kinds of reconstruction related spots have been monitored simultaneously. It was found that stable alternating reconstructions can be observed on the surface with a single-domain 2×1 structure obtained by high-temperature annealing. One period of the RHEED intensity oscillation observed for the specular beam during the growth corresponds to a monatomic layer or a biatomic layer height depending not only on the electron beam incident azimuth but also the glancing angle.
Photoluminescence properties of ZnSe single crystalline films grown by atomic layer epitaxy
Authors: Yao Takafumi , Takeda Toshihiko , Watanuki Ryuji
Published: July 2002

Atomic layer epitaxy has been employed to produce good-quality ZnSe single crystalline films onto (100) oriented GaAs substrates. The epilayers grown at 280 °C exhibited smooth and featureless surface texture and excellent photoluminescence characteristics. They showed dominant excitonic emission lines and a very weak deep center emission band.
Surface solidification and impurity segregation in amorphous silicon
Authors: Peercy P. S. , Poate J. M. , Thompson Michael O. , Tsao J. Y.
Published: July 2002

Real-time measurements of the melt and solidification dynamics during pulsed laser irradiation have permitted elucidation of the processes which lead to the formation of very thin (∼2 nm) buried impurity layers in amorphous silicon. These novel structures are found to result from interfacial segregation at two moving liquid silicon-amorphous silicon interfaces—one propagating toward the surface and the other propagating from the surface inward. The velocities of these interfaces are found to be remarkably low, ranging from 1 to 8 m/s for melts of <20 ns duration.
Fast and slow states at the interface of amorphous silicon and silicon nitride
Authors: Street R. A. , Tsai C. C.
Published: July 2002

The effects of a graded composition layer at the amorphous silicon/nitride interface are studied using transient photoconductivity. The graded layer causes a large increase in the density of slow states (electrons trapped within the nitride), but does not influence the fast interface states. The kinetics of trapping and release are measured and a model of field assisted hopping and thermal excitation is proposed. The different origins of slow and fast states are also discussed.
Charge carrier dynamics of a CO2 laser plasma in a magnetized cathode glow
Authors: Razdan R. , Capjack C. E. , Seguin H. J. J.
Published: July 2002

A Monte Carlo simulation of a magnetized cathode-glow region for a carbon dioxide laser discharge has been undertaken. The computational findings appear to confirm recent observations that the magnetic stabilization effect is due primarily to a Lorentz driven mixing motion of charge carriers at or near the cathode electrode surface.
Diffraction-corrected subsurface imaging with a scanning laser acoustic microscope
Authors: Mueller Rolf K. , Robbins William P. , Zhou Z. Q. , Rudd Eric
Published: July 2002

A back projection (acoustic holography) algorithm has been developed and implemented on a computer-controlled scanning laser acoustic microscope. The algorithm permits the reconstruction of clear well-defined images of acoustic features which are far below (by tens of acoustic wavelengths) the laser-scanned surface of the substrate. In essence, the algorithm corrects for the diffraction of the incident acoustic beam caused by the feature being insonified. Experimental results obtained using an electron microscope locator grid as the test feature and a compressional wave source of 100 MHz are presented.
Coherent instabilities in p-i-n avalanche GaAs diodes up to submillimeter frequency range
Authors: Lippens D. , Nieruchalski J. L.
Published: July 2002

Many-particle numerical simulations of impact ionization in submicron GaAs p-i-n diodes reveal coherent fluctuations up to the millimeter-wave range. The analysis of the auto and cross correlations of fluctuating quantities demonstrates that these spontaneous oscillations result from the delay in excess carrier generation by impact ionization owing to carrier energy relaxation effects rather than the appearance of a negative differential carrier mobility. With regard to this phenomenon, it is believed that the energy relaxation mode of operation of avalanche oscillators may be considered.
Traveling-wave amplifier made from a laser diode array
Authors: Andrews John R.
Published: July 2002

A traveling-wave amplifier has been fabricated from a ten-stripe, AlGaAs phase-locked injection laser array by antireflection coating both facets. A small-signal gain of 18.6 dB, when corrected for optical coupling efficiency, has been observed, resulting in over 100 mW of coherent optical power output. When the signal source is a single transverse and single longitudinal mode diode laser, the far-field radiation pattern is dominated by a single lobe with a divergence of 0.86° in the lateral plane.
Low-frequency noise and discrete charge trapping in small-area tunnel junction dc SQUID’s
Authors: Wakai R. T. , Van Harlingen D. J.
Published: July 2002

We present measurements of the noise properties of very small-area, high current density tunnel junction dc superconducting quantum interference devices (SQUID’s). The low-frequency noise spectra display broad curves and bumps consistent with the presence of individual Lorentzian features superimposed on a background which is always much flatter than 1/f. When these features are most prominent, the voltage across the SQUID exhibits discrete switching behavior which we attribute to the trapping and untrapping of single electrons within the tunneling barrier. This observation, along with other evidence presented, suggests that critical current fluctuations displaying tunneling kinetics dominate the low-frequency noise of these ultrasmall devices.
Application of Z-pinch discharge to additive compression of imploding shock plasmas
Authors: Matsuo H. , Ebihara K. , Ohya Y. , Fujiwara K. , Kudo H.
Published: July 2002

Cylindrical imploding shock waves were produced by detonating cylindrical explosive shells. The Z-pinch discharge was applied to the additive compression of imploding plasmas. Pulsive electric current was supplied through the axis of imploding plasmas at the instant of focusing. An additional rise of temperature of 50–100% was achieved. It might then be concluded that the additive compression of imploding shock plasmas is attained by the application of the Z-pinch discharge.
Low pressure organometallic vapor phase epitaxial growth of device quality GaAs directly on (100) Si
Authors: Shastry S. K. , Zemon S.
Published: July 2002

The epitaxial growth and properties of GaAs layers directly deposited on (100) Si substrates using a low-temperature process are reported. The GaAs layers were grown by organometallic vapor phase epitaxy with a two-step process and without any high-temperature heat treatment of the Si substrates. The layers were of single domain with net carrier concentrations less than 1014 cm−3. Intentionally doped n-type layers (Nd≂1016 cm−3) showed room-temperature electron mobility of 5780 cm2/V s. The high structural quality of GaAs is demonstrated by device characteristics as well as by x-ray diffraction measurements. The observation that an intrinsic mechanism dominates the photoluminescence spectra is another indication of high quality epitaxy.
Amplification of bulk and surface plasmons in semiconductor superlattices
Authors: Hawrylak Pawel , Quinn John J.
Published: July 2002

We study the amplification of bulk and surface plasmons in a type II semiconductor superlattice, which consists of a semi-infinite array of spatially separated electron and hole layers. Amplification is achieved by imposing an external drift velocity on the electrons. For drift velocities exceeding a threshold value, bulk plasmons can be amplified for an arbitrary plasmon wave vector parallel to the layers. Amplification of surface plasmons can occur only for finite wave vectors. Drift velocities required for these processes are calculated and are shown to be experimentally feasible.
Power loss by two-dimensional holes in coherently strained Ge0.2Si0.8/Si heterostructures: Evidence for weak screening
Authors: Xie Y. H. , People R. , Bean J. C. , Wecht K. W.
Published: July 2002

We have used the hot-carrier Shubnikov–de Haas effect to measure the power loss by hot two-dimensional holes in coherently strained Ge0.2Si0.8/Si heterostructures. The measured power loss versus carrier temperature data are best described by the two-dimensional formalism of P. J. Price [J. Appl. Phys. 53, 6864 (1982)] assuming weak screening. Excellent agreement with experiment is obtained only if scattering of the acoustic mode phonons by both the deformation potential and the piezoelectric coupling mechanisms are considered. We are therefore able to deduce a value for the piezoelectric constant for Ge0.2Si0.8 which is approximately 35% of that for InAs (e2pz≊0.22×108 dyne/cm2). In light of the fact that charge transfer effects are expected to be small in bulk (unstrained) GexSi1−x, the present observations are indicative of either a large strain induced change in ionicity or of scattering of acoustic phonons from ordered domains via the piezoelectric mechanism.
Solid phase epitaxial regrowth of ion-implanted amorphized InP
Authors: Licoppe C. , Nissim Y. I. , Krauz P. , Henoc P.
Published: July 2002

Solid phase epitaxial regrowth of implanted amorphous InP layers is shown to occur in the temperature range 230–330 °C. It leads to defective monocrystalline layers. The kinetics of growth follow an activation law with activation energy Ea=1.55 eV±0.2 eV. Roughening of the amorphous/crystalline interface occurs during growth. The dependence of interface roughening on crystal orientation is studied. In all cases, it is shown that the interface is degraded much faster than in GaAs. The comparison between the two compound semiconductors is based on chemical disorder in the amorphized layer.
High-power lasing on the Ne i 540.0-nm line in electron beam generated plasmas
Authors: Ono K. , Oomori T. , Fujita S.
Published: July 2002

Self-terminating lasing at megawatt power levels was observed on the Ne i 540.0-nm line under longitudinal electron beam excitation. A 700-kV, 12-kA, 50-ns electron beam was injected into a stainless-steel drift tube, 175 cm long and 13.4 cm in inner diameter, filled with neutral neon gas in the pressure range 0.1≤P0≤100 Torr. The drift tube was immersed in an axial magnetic guide field in the range 0≤B0≤4.2 kG. Lasing was found to occur for P0≳3 Torr, in the amplified spontaneous emission mode of operation. A maximum output pulse energy of ∼2 mJ was obtained for P0=100 Torr and B0=4.2 kG, corresponding to a peak power of ∼1 MW with an output pulse of ∼2 ns full width at half-maximum.
F2 fuel performance in XeF lasers at ambient and elevated temperatures
Authors: Kimura W. D. , Moody S. E. , Seamans J. F.
Published: July 2002

Extraction measurements of an electron beam pumped XeF laser using either F2 or NF3 as the halogen fuel (neon diluent) are presented. The laser efficiency is measured as a function of output coupling reflectivity and initial gas temperature. Despite the known absorption of F2 at the lasing wavelength (351, 353 nm), the laser efficiency is essentially identical when using either halogen fuel. Gas lifetime when using NF3 is shortened by the formation of nitrogen compounds which degrade the laser performance; this is not the case when using F2. Hence, the ability to use F2 without sacrificing laser efficiency has important implications with regard to the selection of a halogen fuel for extended gas lifetime operation.
Self-mode locking in a transverse-discharge copper-vapor laser
Authors: Im Kiegon , Kim Jin J.
Published: July 2002

A new observation of the self-mode-locking behavior of the copper-vapor laser is reported. In the present experiment, self-mode locking is observed for both of the 510.6-nm and 578.2-nm laser lines in a transverse-discharge copper-vapor laser. The conditions under which the self-locking behavior is observed are at variance from previous results, but they are consistent with the generally accepted requirements. The self-locking mechanism of the longitudinal modes is explained and a numerical comparison is made with a theory based on the third order polarization.
High photoconductive gain in GexSi1−x/Si strained-layer superlattice detectors operating at λ=1.3 μm
Authors: Temkin H. , Bean J. C. , Pearsall T. P. , Olsson N. A. , Lang D. V.
Published: July 2002

We demonstrate high photoconductive gain in GexSi1−x/Si strained-layer superlattice detectors grown by molecular beam epitaxy. The gain mechanism is considered to be the preferential hole trapping in the GexSi1−x wells. Ge0.6Si0.4 waveguide devices operating at the wavelength of 1.3 μm show an optical gain as large as 40 at a low bias of 5–7 V and a gain bandwidth product as large as 3.6 GHz. Preliminary bit error experiments show sensitivity sufficient for transmission at distances of over 25 km and data rates of 200 Mb/s.
Observation of local lattice distortion induced by In doping in GaAs
Authors: Fujiwara Y. , Kita Y. , Tonami Y. , Nishino T. , Hamakawa Y.
Published: July 2002

The In concentration dependence of newly observed Cr-related luminescence lines has been systematically investigated by a low-temperature photoluminescence (PL) method in In,Cr-codoped GaAs. As a result, it has been found that the luminescence center of these In,Cr-related PL lines is a complex of InGa-CrGa-VAs. Furthermore, their relative peak positions with respect to the well-known Cr-VAs PL line have been analyzed by using uniaxial stress data, the result suggesting that local lattice distortion of about 1% is induced by In doping in GaAs.
Semiconductor-doped glass ion-exchanged waveguides
Authors: Cullen T. J. , Ironside C. N. , Seaton C. T. , Stegeman G. I.
Published: July 2002

The properties of planar waveguides and directional couplers fabricated by potassium/sodium ion exchange in semiconductor-doped glasses are described.
Heteroepitaxy of insulator/metal/silicon structures: CaF2/NiSi2/Si(111) and CaF2/CoSi2/Si(111)
Authors: Fathauer R. W. , Hunt B. D. , Schowalter L. J. , Okamoto Masako , Hashimoto Shin
Published: July 2002

Epitaxial insulator (CaF2) layers have been grown on epitaxial metal (CoSi2 and NiSi2) layers on Si(111) by molecular beam epitaxy. The surface morphology and bulk crystallinity are much better for growth on NiSi2, with scanning electron microscopy revealing only small triangular hillocks, and channeling minimum yields as low as 3% measured in the CaF2 using 2.5 MeV 4He+ ions. CaF2 layers grown at 650 °C on CoSi2 consist of a mixture of regions either aligned or rotated 180° with respect to the CoSi2 lattice, while CaF2 layers grown at 550 °C on NiSi2 are of a single orientation, regardless of the orientation of the NiSi2 with respect to the Si substrate.
Observation of resonant tunneling in AlGaAs/GaAs triple barrier diodes
Authors: Nakagawa T. , Imamoto H. , Kojima T. , Ohta K.
Published: July 2002

Resonant tunneling and accompanying negative differential resistance are observed at 85 K in Al0.4Ga0.6As/GaAs triple barrier diodes, where two GaAs wells are separated by three AlGaAs barriers. Five resonance peaks, one small peak for one bias polarity, one medium and one large peak for each bias polarity, are observed. These are the resonance current peaks from the ground level of a populated well to the ground, the first excited or the second excited level of an adjoining unpopulated well. These are the direct electrical observations of the resonant tunneling between confined electron states in two potential wells of a semiconductor multiheterostructure.
High-resolution x-ray diffraction and transmission electron microscopy studies of InGaAs/InP superlattices grown by gas-source molecular beam epitaxy
Authors: Vandenberg J. M. , Chu S. N. G. , Hamm R. A. , Panish M. B. , Temkin H.
Published: July 2002

A three-crystal geometry has been used for high-resolution x-ray diffraction (XRD) along with lattice imaging transmission electron microscopy (TEM) to study two high-quality InGaAs/InP multiquantum well structures grown on (100) InP. These superlattices were prepared by gas-source molecular beam epitaxy using a computer controlled system and were found to have excellent optical properties. Cross-section TEM and the presence of sharp satellite reflections in the XRD profiles demonstrate very smooth interfaces with well-defined modulated structures which could be derived from a kinematic XRD step model. For one of these superlattices, excellent agreement between the step model and the measurements is obtained when the model assumes that each period consists only of the well and the barrier with ideally sharp interfaces. For the other superlattice an additional approximately 9-Å-thick layer of approximate composition In0.47Ga0.53As0.985P0.015 had to be assumed on one side of each quantum well. This additional layer is attributed to substitution of ambient P for 1.5 at. % of the As during growth interruption and is easily eliminated. The comparison of these two structures demonstrates the extreme sensitivity of the high-resolution XRD method in conjunction with the step model to study very small modifications in superlattice characteristics.
Diffusion dynamics of holes in InxGa1−xAs/GaAs strained-layer superlattices
Authors: Gourley P. L. , Wiczer J. J. , Zipperian T. E. , Dawson L. R.
Published: July 2002

We investigate the diffusion dynamics of minority-carrier holes in In0.2Ga0.8As/GaAs strained-layer superlattices by measuring their diffusion lengths, both parallel and perpendicular to the layers, and recombination lifetime for temperatures between 78 and 300 K. From these data we determine a phenomenological hopping time for interlayer motion. We also estimate the valence-band barrier heights which govern this motion, by studying the interband quantum well optical transition energies over the same temperature range.
HgTe-CdTe superlattices: Experimental and theoretical curves of band gap versus HgTe layer thickness
Authors: Reno J. , Sou I. K. , Faurie J. P. , Berroir J. M. , Guldner Y. , Vieren J. P.
Published: July 2002

An experimental curve of room-temperature band gap versus HgTe layer thickness for HgTe-CdTe superlattices is presented for the first time. The room-temperature experimental results are compared to theoretical results determined using the envelope function approximation. Also a few values of the band gap at 2 K are given and compared to theoretical predictions. A good agreement between experiment and theory is found.
Ultrathin InAs/GaAs single quantum well structures grown by atomic layer epitaxy
Authors: Tischler M. A. , Anderson N. G. , Bedair S. M.
Published: July 2002

Extremely thin InAs/GaAs single quantum well structures have been grown by atomic layer epitaxy. The wells were 2 and 4 InAs monolayers thick. Photoluminescence spectra (19 K) from these structures are sharp, intense, and uniform across the sample with full widths at half-maximum for the 2 and 4 monolayer wells of 12 and 17 meV, respectively. These results indicate the high degree of control inherent in atomic layer epitaxy as well as its ability to grow high quality materials.
New device to generate Si2H6 for amorphous silicon depositions
Authors: Dickson C. R.
Published: July 2002

A new device is described for continuous conversion of pure silane into disilane in yields up to 40%. The device was used in line with an amorphous silicon deposition system to grow 1-μm-thick films at 300 °C. The minority-carrier diffusion length measured on one of these films was 0.3 μm at one sun illumination. The device can also be used with a synthesis station to collect large quantities of pure disilane. The absence of hydrocarbons, chlorosilanes, and siloxanes at the 10–100 ppm levels was established by analysis of a collected disilane sample.
Interpretation of quantum yields exceeding unity in photoelectrochemical systems
Authors: Szklarczyk Marek , Allen Roland E.
Published: July 2002

In photoelectrochemical systems involving light shining on a semiconductor interfaced with an electrolyte, the quantum yield as a function of photon frequency ν is observed to exhibit a peak at hν≊2Eg, where Eg is the band gap of the semiconductor. The maximum in this peak is sometimes found to exceed unity. We provide an interpretation involving surface states and inelastic electron-electron scattering. The theory indicates that the effect should be observable for p-type semiconductors, but not n-type.
Effect of temperature during illumination on annealing of metastable dangling bonds in hydrogenated amorphous silicon
Authors: Jackson W. B. , Stutzmann M.
Published: July 2002

Annealing of metastable dangling bond defects in light-soaked undoped hydrogenated amorphous silicon (a-Si:H) is investigated in samples which have been illuminated at different temperatures. Based on a monomolecular annealing model, the distribution of activation energies is determined. The annealing distribution narrows and shifts to higher energies as the temperature during illumination is increased.
Hybrid phase conjugator/modulators using self-pumped 0°-cut and 45°-cut BaTiO3 crystals
Authors: Pepper David M.
Published: July 2002

We report on the demonstration of a simple, passive, alignment-free retromodulator/conjugator. By applying a time-varying electric field across a self-pumped phase conjugate mirror, simultaneous wave front reversal and temporal modulation encoding occur within the same volume. With modest signal fields (∼400 V/cm), we observe >90% depth-of-phase modulation, with a measured bandwidth in excess of 1 MHz (scalable to >10 GHz), and with excellent conjugation fidelity. We also demonstrate, for the first time, self-pumped conjugation using a 45°-cut crystal of BaTiO3 with improved performance: 62% conjugate reflectivity, 100% depth-of-phase modulation at ∼120 V/cm, and faster conjugate-wave build-up time (by a factor of ∼3). Applications of these devices to high modulation-index and high optical-power-handling modulators, remote fiber sensors, and mode-locked phase conjugate resonators are discussed.
Novel laser induced image storage by chemical modification of surfaces in i
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u textured amorphous Ge films
Authors: Rao L. Kameswara , Harshavardhan K. Solomon , Selvarajan A. , Hegde M. S.
Published: July 2002

A novel high contrast laser imaging based on chemical modification of the surfaces has been demonstrated in textured amorphous films of Ge. The process of imaging has been studied by x-ray initiated Auger electron spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, and microdensitometry. Laser irradiation transforms amorphous Ge and amorphous GeO phases to crystalline Ge and GeO phases, the GeO phase growing at the cost of the Ge phase. This leads to imaging, the contrast of which can be enhanced by annealing in air at 525 °C. Photoenhanced chemical modification of the surfaces with concomitant topological rearrangments of the irradiated network has been suggested as the phenomenon responsible for imaging in these films. Such chemical modification of the surfaces has a large potential in high-resolution high-contrast laser imaging.
Formation of CoNbZr films by a dc opposing-target sputtering method
Authors: Miura Michiyori , Tanaka Katsuyuki , Itegami Hitoshi
Published: July 2002

CoNbZr films were prepared using dc opposing-target sputtering equipment. It was investigated as to how the sputtering gas pressure influences the characteristics of the films under the condition of constant deposition rate. The saturation flux density and crystallization temperature were almost constant and independent of the sputtering gas pressure. Their values were 0.83±0.03 T and 562±1 °C. However, the anisotropy field, coercive force, and morphology of the films were significantly affected by the sputtering gas pressure.
Effect of group V/III flux ratio on deep electron traps in AlxGa1−xAs (x=0.7) grown by molecular beam epitaxy
Authors: Hayakawa T. , Kondo M. , Suyama T. , Takahashi K. , Yamamoto S. , Yano S. , Hijikata T.
Published: July 2002

The effect of group V/III flux ratio γ on deep electron traps in AlxGa1−xAs (x=0.7) grown by molecular beam epitaxy at 720 °C has been studied by deep level transient spectroscopy. The photoluminescence characteristics of a GaAs single quantum well sandwiched by Al0.7Ga0.3As are determined by the electron traps denoted as E4–E6(E6′) in Al0.7Ga0.3As with the activation energies of 0.77 eV (E4), 0.72 eV (E5), 0.90 eV (E6), and 1.00 eV (E6′). The concentrations of these traps are minimized to the order of 1013 cm−3 at γ∼2 in spite of high Al content.
Time-of-flight studies of minority-carrier diffusion in AlxGa1−xAs homojunctions
Authors: Ahrenkiel R. K. , Dunlavy D. J. , Hamaker H. C. , Green R. T. , Lewis C. R. , Hayes R. E. , Fardi H.
Published: July 2002

A novel time-of-flight technique has been developed for simultaneously measuring minority-carrier lifetime and diffusivity in homojunctions. A pulsed dye laser produces electron-hole pairs near the front surface of the device. A delay occurs before the onset of photocurrent due to the diffusion transit time of minority carriers to the junction. An analysis of this effect by both a simplified analytical model and a computer simulation gives similar results for the current as a function of time. A fit of the theory to experimental data on Al0.25Ga0.75As n/p homojunctions produces minority-carrier lifetime, diffusivity, and diffusion length.
Evidence for the formation of polycrystalline silicon by argon implantation and its passivation by atomic hydrogen
Authors: Ringel S. A. , Chien H. C. , Ashok S.
Published: July 2002

Evidence is presented through electrical measurements for the presence of microcrystallites in the surface damage layer resulting from the implantation of 20 keV Ar at a moderate dose (1013 cm−2). Low-energy (0.4 keV) atomic hydrogen is found to passivate the polycrystalline grain boundaries resulting from the argon implant. Extremely high Schottky barrier heights on p-type Si, up to 0.88 eV, are also found to result from the implantation of both argon and atomic hydrogen.
Superconductivity of Nb films recovered from megabar dynamic pressures
Authors: Nellis W. J. , Radousky H. B. , Geballe T. H. , Hammond R. H. , Koch R. , Hull G. W.
Published: July 2002

Niobium films 30 μm thick have been recovered successfully from Mbar dynamic pressures and their superconducting properties have been measured. These results demonstrate the feasibility of subjecting films to Mbar dynamic pressure for the potential synthesis of novel, metastable materials.
High performance Ga0.47In0.53As photoconductive detectors grown by chemical beam epitaxy
Authors: Antreasyan A. , Tsang W. T.
Published: July 2002

We have fabricated highly sensitive, planar, interdigitated photoconductive detectors on undoped Ga0.47In0.53As that is grown lattice matched on a semi-insulating InP substrate by chemical beam epitaxy. The devices exhibit intensity-dependent gains as high as 7000, gain-bandwidth products of 20 GHz, detectivities as large as 1012 cm Hz1/2 W−1 at 300 K, and responsivities close to 3000 A/W at λ=1.3 μm. These results are similar to the highest performance characteristics obtained with Ga0.47In0.53As photoconductive detectors that are grown by well established techniques.
Short cavity GaAs/AlGaAs multiquantum well lasers by dry etching
Authors: Yuasa Tonao , Yamada Tomoyuki , Asakawa Kiyoshi , Sugata Sumio , Ishii Makoto , Uchida Mamoru
Published: July 2002

A reactive ion beam etching method with Cl2 plasma is applied to fabricate short cavity GaAs/AlGaAs multiquantum well lasers grown by molecular beam epitaxy. Threshold currents as low as 38 mA are achieved for the 20-μm-long cavity lasers. The very short cavity lasers show single longitudinal mode operation under pulsed conditions. Cavity length dependence of the threshold current is also investigated for the dry-etched lasers with cavity lengths varying from 20 to 500 μm.
High-power AlGaAs/GaAs single quantum well lasers with chemically assisted ion beam etched mirrors
Authors: Tihanyi P. , Wagner D. K. , Roza A. J. , Vollmer H. J. , Harding C. M. , Davis R. J. , Wolf E. D.
Published: July 2002

We report the first use of chemically assisted ion beam etching to form laser mirrors on GaAlAs graded index separate confinement single quantum well heterostructures grown by metalorganic chemical vapor deposition. Over 80 mW cw optical power is obtained from the etched facet of uncoated 300-μm-long, etched/cleaved 60 μm stripe devices mounted p side up, and catastrophic failure occurs at a cw power as high as 205 mW. Differential quantum efficiencies for light emitted from the etched facet are 32% pulsed (27% cw) and the threshold current is 145 mA pulsed (150 mA cw).
Thermal stability of InGaAs/InP quantum well structures grown by gas source molecular beam epitaxy
Authors: Temkin H. , Chu S. N. G. , Panish M. B. , Logan R. A.
Published: July 2002

Single InGaAs/InP quantum wells and superlattices grown by gas source molecular beam epitaxy were subjected to brief anneals at temperatures in the 600–850 °C range. The resulting increases in the well thickness and changes in composition were monitored by low-temperature photoluminescence and transmission electron microscopy. Very sharp well-barrier interfaces are found to be present even after annealing at the highest anneal temperature. These results can be modeled assuming diffusivity proportional to the square of concentration with D0=7×1010 cm2/s and an activation energy of Q=5.8 eV.