bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion dynamics in multiple electrostatic waves in a magnetized plasma. II. Enhancement of the acceleration
Authors: Bénisti D. , Ram A. K. , Bers A.
Published: July 2002

The maximal energy an ion can gain from a discrete spectrum of electrostatic waves propagating perpendicularly to a uniform magnetic field is investigated. In the case when the wave spectrum contains at least two on-resonance waves, the ion is shown to reach energies which are much higher than in the case of one wave. When the ion energization is enhanced, even when the ion motion is not coherent, the ion orbit remains close to orbits found from a first order perturbation analysis. This implies that, unlike in the case of a single wave, the ion can reach high energies regardless of how small the wave amplitudes are. The dependence of the ion energization on the wave spectrum characteristics is described in great detail by deriving the extent, in action, of the first order orbits, and the way these orbits may connect.
Generalized reduced magnetohydrodynamic equations
Authors: Kruger S. E. , Hegna C. C. , Callen J. D.
Published: July 2002

A new derivation of reduced magnetohydrodynamic (MHD) equations is presented. A multiple-time-scale expansion is employed. It has the advantage of clearly separating the three time scales of the problem associated with (1) MHD equilibrium, (2) fluctuations whose wave vector is aligned perpendicular to the magnetic field, and (3) those aligned parallel to the magnetic field. The derivation is carried out without relying on a large aspect ratio assumption; therefore this model can be applied to any general toroidal configuration. By accounting for the MHD equilibrium and constraints to eliminate the fast perpendicular waves, equations are derived to evolve scalar potential quantities on a time scale associated with the parallel wave vector (shear-Alfven wave time scale), which is the time scale of interest for MHD instability studies. Careful attention is given in the derivation to satisfy energy conservation and to have manifestly divergence-free magnetic fields to all orders in the expansion parameter. Additionally, neoclassical closures and equilibrium shear flow effects are easily accounted for in this model. Equations for the inner resistive layer are derived which reproduce the linear ideal and resistive stability criterion of Glasser, Greene, and Johnson [Phys. Fluids 18, 875 (1975)].
On the orbit-averaged Monte Carlo operator describing ion cyclotron resonance frequency wave–particle interaction in a tokamak
Authors: Eriksson L.-G. , Mantsinen M. J. , Hellsten T. , Carlsson J.
Published: July 2002

In a toroidal plasma the distribution function of ions interacting resonantly with waves in the ion cyclotron range of frequencies (ICRF) can be described with a three-dimensional orbit-averaged Fokker–Planck equation. This equation can be solved with a Monte Carlo method. Explicit expressions for the Monte Carlo operator describing wave–particle interaction, within the framework of quasilinear theory, are given. Furthermore, properties of the operator are discussed.
Two-dimensional electron-magnetohydrodynamic instabilities
Authors: Califano F. , Prandi R. , Pegoraro F. , Bulanov S. V.
Published: July 2002

The linear dispersion relation and the spatial structure of high frequency instabilities, with a mixed tearing-bending character is studied. These instabilities are driven by the electron velocity gradient in a collisionless electron plasma moving against a background of immobile neutralizing ions in an inhomogeneous magnetic field. As the angle between the perturbations and the magnetic field lines is varied, perturbations change from the tearing type (parallel propagation) to the bending type (perpendicular propagation).
Modeling the filamentation of ultra-short pulses in ionizing media
Authors: Couairon A. , Bergé L.
Published: July 2002

The filamentation of ultra-short pulses is investigated for plane waves propagating in gases ionized by multiphoton sources. The spatial growth rate of the filamentary modulational instability is computed as a function of the transverse wavenumber and frequency of periodic perturbations. Classical results for optical filamentation in Kerr media are recovered when the density of the electron plasma produced by ionization is close to zero. However, when the electron density is high enough, a beam with an input power above the Kerr self-focusing threshold is shown to stop forming filaments. Stability domains are expressed in terms of the electron density and pulse peak power, both for stationary perturbations and when the inertial plasma response together with the group-velocity dispersion of the wave are taken into account. These theoretical results are supported by numerical simulations and the influence of a delayed Kerr response on filament formation is finally discussed.
Optogalvanic measurements of gas temperature in the cathode fall
Authors: Doughty D. K. , Den Hartog E. A. , Lawler J. E.
Published: July 2002

Optogalvanic diagnostics are used to determine the electric field and the absolute gas temperature as a function of position in the cathode fall of an abnormal glow discharge. Gas temperatures in the cathode fall at modest current densities are as much as a factor of 2 above ambient temperatures. Symmetric charge exchange of energetic positive ions produces fast neutrals which efficiently heat gas in the cathode fall. This hot, rarefied gas has important implications in modeling the cathode fall, sputtering processes at the cathode, the glow-to-arc transition, and other phenomena.
Self-developing photoresist using a vacuum ultraviolet F2 excimer laser exposure
Authors: Henderson D. , White J. C. , Craighead H. G. , Adesida I.
Published: July 2002

An F2 excimer laser at 157 nm has been used for the first time as an exposure source for high resolution photolithography with the self-developing resist nitrocellulose. Ablative development of the nitrocellulose was observed for 157-nm energy densities greater than 0.025 J/cm2. Stencil masks fabricated using electron beam lithography were used for contact photolithography, and mask features to 200 nm were reproduced. These are the smallest features yet reproduced from a mask with an optical, self-developing resist technology.
Operation principle of the InGaAsP/InP laser transistor
Authors: Mori Yoshihiro , Shibata Jun , Sasai Yoichi , Serizawa Hiroyuki , Kajiwara Takao
Published: July 2002

A laser transistor functions both as a semiconductor laser and a heterojunction bipolar transistor. It generates stimulated emission light from the base region. We have obtained, typically, a maximum laser power of 3 mW, a current gain of 2000, and a transition frequency of 2.5 GHz for the fabricated devices. We show that the novel light output control can be obtained by changing its collector voltage. Both laser output and collector current can also be simultaneously controlled by changing the base current.
Electrical uniformity for Si-implanted layer of completely dislocation-free and striation-free GaAs
Authors: Hyuga Fumiaki , Kohda Hiroki , Nakanishi Hideo , Kobayashi Takashi , Hoshikawa Keigo
Published: July 2002

Electrical uniformity for Si-implanted layer of In-doped GaAs completely free from dislocations and striations is evaluated here using small Hall chips with 400-μm spacing. Sheet carrier concentration, which determines threshold voltages of field-effect transistors, is quite uniform across the wafer, and its standard deviation decreases to 1/5 of that for the conventional liquid-encapsulated Czochralski-grown GaAs. Hall mobility is not degraded despite a high concentration (5–10×1019 atoms cm−3) of indium. These results are promising for realizing substrates of high-performance GaAs large-scale integrated circuits.
High quality tantalum superconducting tunnel junctions for microwave mixing in the quantum limit
Authors: Face D. W. , Prober D. E. , McGrath W. R. , Richards P. L.
Published: July 2002

We report on a novel step-defined process used to produce small area (1–6 μm2), high critical current density (102–104 A/cm2) superconducting tunnel junctions with Ta base electrodes and Pb0.9Bi0.1 counterelectrodes. These junctions have extremely small subgap leakage currents, a ‘‘sharp’’ current rise of width ΔV∼30 μV at the sum-gap voltage, and show strong quantum effects when used as microwave mixers. Accurate measurements at 34.5 GHz with a 1.5 GHz intermediate frequency (IF) give single sideband mixer gains up to G=1.1±0.1 and mixer noise temperatures as low as TM=3.8±1.0 K. This value of TM is close to the quantum limit TQ=ℏω/k ln 2=2.5 K. The lowest receiver noise temperature measured at the 1.3 K input to the mixer block, TR=24±1 K, is the best value reported for any heterodyne receiver. Infinite available gain is obtained for a low (25 MHz) IF and a coupled gain as large as 1.6±0.4 is observed.
Cancellation of fiber loss by semiconductor laser pumped Brillouin amplification at 1.5 μm
Authors: Olsson N. A. , van der Ziel J. P.
Published: July 2002

The propagation loss is canceled, and 5 dB of net gain is obtained by Brillouin amplification in a 37.5-km-long single-mode optical fiber. A narrow linewidth external cavity semiconductor laser is used as the pump source and a gain of 4.3 dB/mW pump power is measured. The Brillouin linewidth is measured to be 150 MHz in contrast to previous measurements of ∼20 MHz. The Brillouin Stokes shift was 11.3 GHz at 1.5 μm wavelength.
Temperature and x-ray intensity scaling in KrF laser plasma interaction
Authors: Gupta P. D. , Popil R. , Fedosejevs R. , Offenberger A. A. , Salzmann D. , Capjack C. E.
Published: July 2002

Experimental measurements are presented of space and time integrated x-ray emission from aluminum plasma produced by 2 ns (full width at half-maximum), 268 nm Raman compressed KrF laser pulses. A single temperature spectrum was measured giving temperatures of 75–440 eV over the range of intensities 9×1011–2×1013 W/cm2. This scaling agrees well with a simple self-regulating model. Conversion of laser energy into x rays above 1 keV energy was found to scale as I2.37L reaching 0.35% at 3.5×1013 W/cm2.
Multiple wavelength optical recording using cyanine dye J aggregates in Langmuir–Blodgett films
Authors: Ishimoto C. , Tomimuro H. , Seto J.
Published: July 2002

An optical storage technique based on the characteristic absorption bands of J aggregates of organic dyes is reported. The information is written by disordering the regular structures of cyanine dye J aggregates with a laser beam. This technique gives high recording sensitivity, and the disordered dye molecules can be made to reform the J aggregate, which indicates that the recording process is reversible. The J aggregates of cyanine dyes were formed by incorporating them in Langmuir–Blodgett (LB) films. The advantages of the narrow absorption bands of J aggregates and of the controlled multilayer forming capability of LB films were combined to demonstrate multiple wavelength optical recording using two recording layers.
Growth of high mobility n-type CdTe by photoassisted molecular beam epitaxy
Authors: Bicknell R. N. , Giles N. C. , Schetzina J. F.
Published: July 2002

We report details of the successful controlled substitutional doping of CdTe films with indium. These n-type films were prepared using a new technique, photoassisted molecular beam epitaxy, in which the substrate is illuminated during the deposition process. In the present work, an argon ion laser was used as an illumination source. The incident light was found to produce immediate and significant changes in the electrical properties of the films. In particular, highly activated n-type CdTe:In layers resulted.
Microstructural studies of reactive ion etched silicon
Authors: Jeng S. J. , Oehrlein G. S.
Published: July 2002

The structures of Si near-surface damage induced after the removal of a thick SiO2 layer on Si using reactive ion etching with various etching gases were studied by transmission electron microscopy. Cross-sectional micrographs showed the presence of a fluorocarbon film on the Si surface after the SiO2 layer is etched away. No extended defects were observed in Si etched utilizing pure CF4 or CF4/20% H2 etching gas, even after a 25-min overetch into Si. For a CF4/40% H2 etching gas, no extended lattice defects were evident for overetch times of up to 5 min. However, extensive damage was found in the Si surface layer after a 10-min or longer overetch. This extensive damage consists of {111} planar defects distributing underneath the Si surface to a depth of 300 Å. The planar defects are highly decorated by impurities, likely H and possibly C, F. A pure H2 etching gas was found to introduce a heavily damaged layer and a high density of extended defects near the Si surface after only a 5-min overetch. These observations indicate that H ion bombardment plays an important role in the formation of Si near-surface damage during reactive ion etching.
Amplification of high bandwidth signals through two-wave mixing in photorefractive Bi12SiO20 crystals
Authors: de Montchenault G. Hamel , Loiseaux B. , Huignard J. P.
Published: July 2002

We report a new nearly degenerate two-wave mixing interaction in photorefractive Bi12SiO20 crystals in which the signal beam is time modulated at high frequency. The beam coupling phenomena and the time integration properties of the crystal allow us to achieve a differential gain γdiff on the transmitted signal beam. The dependence of γdiff versus the duty cycle of the modulated signal is analyzed. Amplification and regeneration of periodic, or random sequences of information bits are experimentally demonstrated.
Determination of the band-edge offset in heterojunctions by electron beam induced current (GaAs/GaAlAs)
Authors: Eisenbeiss A. , Heinrich H. , Opschoor J. , Tijburg R. P. , Preier H.
Published: July 2002

The electron beam induced current generated at a GaAs/Ga0.48Al0.52As heterojunction was investigated as a function of externally applied bias. In the absence of interface charge the flatband voltage was determined and the band-edge offset evaluated. For the valence-band-edge offset 5.5 meV/% Al was obtained.
Millimeter-band oscillations based on resonant tunneling in a double-barrier diode at room temperature
Authors: Brown E. R. , Sollner T. C. L. G. , Goodhue W. D. , Parker C. D.
Published: July 2002

A double-barrier diode at room temperature has yielded oscillations with fundamental frequencies up to 56 GHz and second harmonics up to 87 GHz. The output powers at these frequencies were about 60 and 18 μW, respectively. These results are attributed to a recent improvement in the material parameters of the device and to the integration of the device into a waveguide resonator. The most successful diode to date has thin (∼1.5 nm) AlAs barriers, a 4.5-nm-wide GaAs quantum well, and 2×1017 cm−3 doping concentration in the n-GaAs outside the barriers. This particular diode is expected to oscillate at frequencies higher than those achieved by any reported p-n tunnel diode.
Effect of thermal pretreatment on electron irradiation induced defects in hydrogen-grown silicon
Authors: Wu Jin , Qin Guo-Gang
Published: July 2002

Wafers of float zone Si grown in hydrogen (Si[H]) were annealed at various temperatures in the range of 300–750 °C before irradiation with 5 MeV electrons. It was found that hydrogen-related deep levels were no longer observed, when the preannealing temperature was above 500 °C (450 °C) in the case of irradiated n-type Si[H] (p-type Si[H]) samples. Similarly, the convergence of annealing temperatures of different irradiation defects towards a common temperature normally observed in Si[H] was no longer observed, if the Si[H] sample had been annealed at or above 550 °C. A dynamic model is proposed to explain the experimental results.
Orientation dependence of the phase modulation in a p-n junction GaAs/AlxGa1−xAs waveguide
Authors: Faist J. , Reinhart F.-K. , Martin D. , Tuncel E.
Published: July 2002

Phase modulation has been measured in a reverse-biased P-i-N GaAs/AlxGa1−xAs double heterostructure with heavily doped (N, P∼1018 cm−3) AlxGa1−xAs layers. These measurements were performed at two wavelengths (1.09 and 1.15 μm), for both TE and TM modes and with light propagating in the [110] and [11̄0] directions. We found that the effective quadratic electro-optic coefficients R11 and R12 have approximately the same magnitude and sign. The values are −(40±10)×10−17 cm2/V2 and −(54±10)×10−17 cm2/V2 for λ=1.15 μm and λ=1.09 μm, respectively. The contribution of the plasma effect due to the free carrier is comparable and has the same sign.
Compression of nonlinearly chirped pulses using Gires–Tournois interferometers
Authors: Zhao W. , Bourkoff E.
Published: July 2002

In optical pulse compression experiments in the femtosecond regime, cubic phase distortion can adversely affect the compression ratio. This distortion arises from both the cubic phase of the grating pair used in such experiments and also from pulse propagation in the fiber, when taking into account the cubic order dispersion and shock terms. We numerically analyze how the cubic distortion, which leads to nonlinearly chirped pulses, can be compensated by Gires–Tournois interferometers. We discuss design considerations and show how the use of such interferometers can lead to even shorter optical pulses by utilizing more of its available bandwidth.
Resonant tunneling of holes in AlAs/GaAs triple barrier diodes
Authors: Nakagawa T. , Fujita T. , Matsumoto Y. , Kojima T. , Ohta K.
Published: July 2002

Resonant tunneling of holes is observed at 85 K in an AlAs/GaAs/AlAs/GaAs/AlAs triple barrier structure sandwiched by p-GaAs layers. Two to seven resonances are observed in the current-voltage characteristics for all samples and bias polarities. The resonance peak voltages are observed to decrease according to the increase of the well thickness. The edge energies of hole subbands in the well are calculated from the resonance voltages, and comparison with the theoretical value is discussed.
Impurity-induced disorder-delineated optical waveguides in GaAs-AlGaAs superlattices
Authors: Julien F. , Swanson P. D. , Emanuel M. A. , Deppe D. G. , DeTemple T. A. , Coleman J. J. , Holonyak N.
Published: July 2002

Layer intermixing in GaAs-AlGaAs superlattices achieved by Zn thermal diffusion has been used to fabricate buried channel optical waveguides. Linear waveguides with small, abrupt bends were made and light was seen to be transmitted through these for bend angles up to 7.5 degrees corresponding to an effective index of refraction difference of 0.9% for a 50% average Al composition of the layers bounding the superlattice. For radiation between the band gap of bulk GaAs (870 nm) and the effective band gap of a 10-nm GaAs quantum well (840 nm), the 3-mm-long waveguides appeared to be semitransparent suggesting a possible use in planar, buried channel all-semiconductor integrated optoelectronics.
Experiments of the superconducting proximity effect between superconductor and semiconductor
Authors: Hatano Mutsuko , Nishino Toshikazu , Kawabe Ushio
Published: July 2002

Coherence length in a semiconductor induced by the superconductor proximity effect is obtained experimentally from superconducting transition temperature measurements based on the de Gennes–Werthamer–Hauser theory. It was found that the coherence length in the semiconductor increases with increase in the carrier concentration n as a function of n1/3. This result agreed with the numerical result derived from the Seto–Van Duzer theory.
Iterative method for computing the inverse Abel transform
Authors: Vicharelli Pablo A. , Lapatovich Walter P.
Published: July 2002

A rapidly converging iterative method based on deconvolution techniques is proposed for the computation of the inverse Abel transform. The calculations only involve repeated applications of the forward Abel transform and no derivatives are needed. The iterative method is shown to be less susceptible to noise amplification when compared with other techniques.
Electro-optical performance of a new, black-white and highly multiplexable liquid crystal display
Authors: Schadt Martin , Leenhouts Frans
Published: July 2002

A new, low bias tilt field-effect liquid crystal display (LCD) is presented with better image quality than supertwist or superbirefringence LCD’s at the same high level of multiplexing. In its positive contrast mode, the display image is black on white with virtually no inherent coloration and with a comparably large contrast as that of twisted nematic LCD’s. The viewing range of the display is as wide as that of superbirefringence LCD’s, whereas its image quality is an order of magnitude less dependent on cell gap variations. With specifically designed liquid crystal mixtures, multiplexing ratios of 1000:1 and response times below 300 ms result.
Formation of amorphous Ni-Zr alloys by mechanical alloying of mixtures of the intermetallic compounds Ni11Zr9 and NiZr2
Authors: Lee P. Y. , Koch C. C.
Published: July 2002

Amorphous Ni40Zr60 and Ni50Zr50 alloy powders were synthesized by mechanical alloying of mixtures of the intermetallic compounds Ni11Zr9 and NiZr2. Milling these compounds together in the proper proportions resulted in material transfer and amorphization of alloys with compositions Ni40Zr60 and Ni50Zr50. After crystallization in a differential scanning calorimeter, the same products of crystallization were observed as for crystallization of liquid quenched amorphous alloys of the same compositions. The driving force for the amorphization of Ni11Zr9+NiZr2 mixtures is believed to be either the steep rise in free energy of the line compounds as material transfer moves their compositions off stoichiometry, or the creation of a critical defect concentration in the intermetallic compounds.
Precision of series-array Josephson voltage standards
Authors: Kautz R. L. , Lloyd Frances L.
Published: July 2002

Comparison of two series-array Josephson voltage standards operated at over 1 V shows that they differ in voltage by less than 2 parts in 1017.
Strain-induced In incorporation coefficient variation in the growth of Al1−xInxAs alloys by molecular beam epitaxy
Authors: Turco F. , Massies J.
Published: July 2002

The reported experimental results demonstrate the influence of the substrate-induced strain on the In incorporation coefficient in the growth of AlInAs by molecular beam epitaxy. AlInAs has either been grown lattice matched to InP or with a 2.3% lattice mismatch with GaAs. The In incorporation coefficient has been determined through reflection high-energy electron diffraction intensity oscillations. The strain effect on the In incorporation coefficient is supported by a thermodynamic analysis applied to the more simple but similar case of strained InAs growth.
Thermally stable, low-resistance NiInW ohmic contacts to n-type GaAs
Authors: Murakami Masanori , Price W. H.
Published: July 2002

A new thermally stable, low-resistance NiInW contact metal to n-type GaAs has been developed by depositing a thin In layer with Ni and W layers and annealing at elevated temperatures for a short time. Low resistances of ∼0.3 Ω mm were obtained at annealing temperatures in the range of 800 to 1000 °C. The contact resistances were stable during subsequent annealings at 400 °C for 100 h and 500 °C for 10 h. The thermal stability of the contact resistance and the surface morphology of this contact are superior to those of the conventionally used AuNiGe contacts and this new contact is suitable for various device applications. Further reduction of the contact resistance can be achieved simply by reducing the sheet resistance of the contact metals.
Selectively enhanced silicide formation by a gold interlayer: Probing the dominant diffusing species and reaction mechanisms during thin-film reactions
Authors: Chang Chin-An , Song Jerng-Sik
Published: July 2002

Formation of silicides in the presence of a thin gold interlayer is studied, making use of the rapid outdiffusion of Si through gold. With Si being the dominant diffusing species, an enhanced rate is expected, as observed for PtSi, Fe3Si, CoSi, and MoSi2. No enhancement is expected when metal is the dominant diffusing species, in agreement with the results on Pt2Si, Co2Si, and Ni2Si. Such studies thus provide valuable information regarding reaction mechanisms.
Equilibrium temperature and related defects in intrinsic glow discharge amorphous silicon
Authors: McMahon T. J. , Tsu R.
Published: July 2002

We find the equilibrium temperature for intrinsic glow discharge amorphous silicon to be 195–200 °C. Defects left behind after fast cooling result in a temperature-dependent dc photoconductivity which shows small differences in the tail state recombination kinetics when compared to defects left behind in the same number after light soaking. Finally anneal kinetics of fast cool defects follow neither singly activated, mono-, nor bimolecular kinetics with a temperature dependence indicating activation energies from 1.0 to 1.4 eV. Unlike the distribution of defects left behind in similar number as a result of light soaking at room temperature, the distribution of defects resulting from fast cooling from higher temperature is shifted to higher energies and requires much longer anneal times.
Novel high quantum efficiency Si-TaSi2 eutectic photodiodes
Authors: Ditchek B. M. , Yacobi B. G. , Levinson M.
Published: July 2002

A high quantum efficiency photodiode has been fabricated using the in situ junctions in a Si-TaSi2 eutectic composite. Due to the three-dimensional distribution of junctions in this photodiode, it yields a nearly constant quantum efficiency of about 50% between 450 and 1000 nm. In addition, the average lateral distance between junctions of only 8 μm gives this novel photodiode an inherently good spatial resolution for photodiode array applications.
Continuous room-temperature operation of an InGaAs-GaAs-AlGaAs strained-layer laser
Authors: Yang Y. J. , Hsieh K. Y. , Kolbas R. M.
Published: July 2002

We report the first continuous wave room-temperature InGaAs-GaAs-AlGaAs strained-layer semiconductor laser diode grown by molecular beam epitaxy. The laser is a multiple quantum well transverse junction stripe laser with a lateral heterojunction fabricated by zinc diffusion enhanced compositional disordering. The low-threshold (20 mA) and single-mode performance of the laser demonstrates that a high-quality lateral p+-p-n junction and lateral heterobarrier can be formed by zinc diffusion compositional disordering of a strained-layer InGaAs-GaAs-AlGaAs quantum well heterostructure.
Electrical and structural characterization of ultrathin epitaxial CoSi2 on Si(111)
Authors: Phillips Julia M. , Batstone J. L. , Hensel J. C. , Cerullo M.
Published: July 2002

We report the fabrication of epitaxial CoSi2 layers on Si(111) as thin as 1 nm. The crystalline lattice of these layers is coherent with the Si lattice, and the silicide is electrically continuous. There are pronounced structural differences between films which are less than 3 nm thick and those which are thicker. The resistivity of the layers increases sharply with decreasing thickness. This is the first report of the growth of coherent, electrically continuous CoSi2 layers on Si.
Nanometer-scale columns in GaAs fabricated by angled chlorine ion-beam-assisted etching
Authors: Goodhue W. D. , Pang S. W. , Johnson G. D. , Astolfi D. K. , Ehrlich D. J.
Published: July 2002

Angled chlorine ion-beam-assisted etching has been used in combination with masked ion beam lithography to produce columns in GaAs with widths of less than 10 nm and height-to-width ratios greater than 25. This technique allows the highly controllable fabrication of structures with dimensions smaller than initially defined by the lithography. It can be applied to the fabrication of ultrasmall GaAs/AlGaAs quantum well structures having quantized energy states in two or three dimensions while at the same time being compatible with full-wafer processing.
Assessment of the surface-photovoltage diffusion-length measurement
Authors: McElheny P. J. , Arch J. K. , Fonash S. J.
Published: July 2002

We undertake a reevaluation of the surface-photovoltage diffusion-length experiment, numerically solving the governing equations without any prior assumptions. We find that, although the technique is applicable for crystalline semiconductors, it does not measure, in general, a simple diffusion length LD=(kTμτ)1/2 for amorphous materials. It is demonstrated that this failure is attributable to the localized gap states inherent in amorphous semiconductors. The presence of localized gap states results in drift and diffusion terms of comparable magnitude and, hence, results in the inability to simply measure the (μτ)1/2 product. We also demonstrate that using thicker samples does not, in general, alleviate this problem.
Determination of the natural valence-band offset in the InxGa1−xAs system
Authors: Hwang J. , Pianetta P. , Shih C. K. , Spicer W. E. , Pao Y.-C. , Harris J. S.
Published: July 2002

The natural valence-band offset (NVBO) between semiconductors in a common anion alloy system can be determined through photoemission core level measurements. In this work, we tested this method in the InxGa1−xAs system. The NVBO between GaAs and InAs is measured to be 0.11±0.05 eV. This result is in approximate agreement with the experimental value of 0.17±0.07 eV determined by x-ray photoemission spectroscopy measurements.
Characteristics of Si-doped GaAs epilayers grown by metalorganic chemical vapor deposition using a silane source
Authors: Liu Chee-Wee , Chen Sheng-Li , Lay Jyh-pyng , Lee Si-Chen , Lin Hao-Hsiung
Published: July 2002

The silicon doping of GaAs grown by metalorganic chemical vapor deposition using a silane source has been investigated. The amphoteric property of the Si dopant is demonstrated for the first time. It is found that the doping characteristics are strongly temperature dependent. At the growth temperature higher than 600 °C and the arsine to trimethylgallium mole ratio (AsH3/TMG) around 217, the conduction is n type and the carrier concentration increases as the temperature increases. On the other hand, when the growth temperature is lower than 600 °C, the carrier concentration increases as the temperature decreases and the conduction becomes p type at 400–450 °C. In addition, when the AsH3/TMG mole ratio is below 50, the Si-doped GaAs layers also become p type. The GaAs light-emitting diode is thus successfully fabricated using a single silicon dopant.
Hg incorporation in CdTe during the growth of HgTe-CdTe superlattices by molecular beam epitaxy
Authors: Reno J. , Sporken R. , Kim Y. J. , Hsu C. , Faurie J. P.
Published: July 2002

HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
Optically induced regeneration of the stable configuration of the EL2 defect in GaAs
Authors: von Bardeleben H. J. , Bagraev N. T. , Bourgoin J. C.
Published: July 2002

Electron paramagnetic resonance measurements on the EL2 defect in semi-insulating GaAs show that after optically induced quenching into the metastable configuration the original stable configuration can be optically regenerated at temperatures below 140 K. We determined the spectral dependence of this regeneration in the 70–140 K temperature range. It is characterized at 90 K by an absorption band centered at (0.8±0.1) eV. However, the spectral dependence is temperature dependent and the thermal activation energy varies with the photon energy.
Rapid annealing of Hg1−xCdxTe by immersion in a hot mercury bath
Authors: Kalish R. , Fastow R. , Richter V. , Shaanan M.
Published: July 2002

A simple technique for annealing ion implanted Hg1−xCdxTe in a mercury atmosphere has been developed. In this technique, Hg1−xCdxTe is sandwiched between two silicon wafers and immersed in a hot mercury bath. This permits rapid annealing at well defined temperatures and times. Indium-implanted Hg1−xCdxTe (x=0.23 and x=0.7) samples have been annealed using this method at temperatures ranging from 260 to 350 °C and for times ranging from 3 s to 1 h. The near surface crystalline quality, as measured by ion channeling, improved after annealing and was comparable to that obtained by other annealing techniques. No change in surface stoichiometry, as measured by particle-induced x-ray emission, was detected in the Hg0.77Cd0.23Te samples.
Interface structure and lattice mismatch of epitaxial CoSi2 on Si(111)
Authors: Zegenhagen J. , Huang K.-G. , Hunt B. D. , Schowalter L. J.
Published: July 2002

We have used the x-ray standing-wave technique and bulk x-ray diffraction to investigate the structural properties of thin CoSi2 layers grown epitaxially on Si(111). The perpendicular lattice mismatch with respect to the Si substrate was found to be −0.0152±0.0003 and −0.016±0.001 for 6-nm-thick and 16-nm-thick layers, respectively. The distance between Si(111) and the first Co layer was measured to be (0.288±0.005) nm and is thus stretched by (0.014±0.005) nm compared with a value determined by Si-like bulk bond length. The Co atoms are attached to the Si(111) dangling bonds in agreement with the model of fivefold coordinated metal atoms at the interface.
Heteroepitaxial growth of Cd1−xMnxTe on GaAs by metalorganic chemical vapor deposition
Authors: Nouhi Akbar , Stirn Richard J.
Published: July 2002

In this letter we report on preliminary results of heteroepitaxial growth of the dilute magnetic semiconductor alloy Cd1−xMnxTe on GaAs by metalorganic chemical vapor deposition. Dimethylcadmium (DMCd), diethyltellurium (DETe), and tricarbonyl (methylcyclopentadienyl) manganese (TCPMn) were used as source materials. The TCPMn had to be heated to as high as 140 °C to provide the required vapor pressure. Films with Mn atomic fractions up to 30% have been grown over the temperature range 410–450 °C. Results of optical absorption/transmission, photoluminescence, and x-ray diffraction measurements are presented along with a scanning electron micrograph showing good surface morphology of the grown layers.
Rapid thermal diffusion and ohmic contacts using zinc in GaAs and GaAlAs
Authors: Tiwari Sandip , Hintzman Jeffrey , Callegari Alessandro
Published: July 2002

We report behavior of zinc diffusion and p-type ohmic contacts to GaAs and GaAlAs (aluminum mole fraction ∼0.3) by Zn3As2 as vapor source and zinc embedded in tungsten films as solid source using rapid thermal processing. Tungsten acts as an inert refractory metallurgy during the processing. The diffusion profiles show high surface concentrations (mid 1019 cm−3 to low 1020 cm−3) and a diffusion profile in agreement with Tuck’s model of substitutional-interstitial diffusion in the presence of vacancy nonequilibrium. Both GaAs and GaAlAs show excellent transport properties with mobilities of 75–100 and 40–60 cm2 V−1 s−1, respectively, at room temperature. Short-time (sub-12-s) diffusions lead to sub-1000-Å diffused contacts in the 650–900 °C temperature range with contact resistances below a measurement accuracy of 5×10−7 Ω cm2. The contact technology has been demonstrated in heterostructure bipolar transistors and p-channel heterostructure field-effect transistors. It is an attractive alternative to conventional gold-based contact metallizations.
GaAs heteroepitaxial growth on Si for solar cells
Authors: Itoh Yoshio , Nishioka Takashi , Yamamoto Akio , Yamaguchi Masafumi
Published: July 2002

Thermal annealing effects on the reduction of dislocation density in GaAs on Si substrates were investigated. The dislocation density in GaAs films grown on Si substrates by metalorganic chamical vapor deposition was reduced by in situ thermal annealing to 2×106/cm2. We have found that the cooling and heating cycle of the GaAs film is most important factor in reducing the dislocation density in thermal annealing. Solar cells fabricated using GaAs films with 5×106/cm2 etch pit density have 18% conversion efficiency for the active area under AM1.5 simulated illumination.
Increased XeF(B→X) laser efficiency at high pump rate and elevated temperature
Authors: Litzenberger L. , Mandl A.
Published: July 2002

A XeF(B→X) laser efficiency of 6.0% has been observed in an electron beam pumped device. This is the highest XeF(B→X) laser efficiency reported to date. Mixtures of NF3 , Xe, and Ne at 425 K and a density of 3 amagat were pumped at a rate of 280 kW/cm3 with a 550 ns pulse. This deposited 150 J/l into the laser gas. Subsequent experiments at 190 J/l input (and 460 K) yielded specific laser outputs as high as 11 J/l.
Ionization-enhanced solid phase epitaxy of amorphous silicon with boron impurities
Authors: Park Won Woo , Becker M. F. , Walser R. M.
Published: July 2002

We have made the first high-resolution, laser interferometric measurements of the functional dependence of the velocity of (100) silicon solid phase epitaxy on the concentration of implanted boron impurities NB. At all measurement temperatures (450–550 °C), and for all NB<5×1019 cm−3 the fractional increase in the velocity was identically equal to the dimensionless ratio NB/Ni, where Ni is a thermally activated factor. This result disagrees with the predictions of all models for the effect of impurities on solid phase epitaxial growth.
Characterization of Mn-doped InAsxP1−x grown by organometallic vapor phase epitaxy
Authors: Huang K. , Wessels B. W.
Published: July 2002

Epitaxial layers of InAsxP1−x:Mn are grown by organometallic vapor phase epitaxy on (100) oriented InP substrates. The InAsxP1−x layers are deliberately doped with Mn from the vapor phase. Photoluminescent properties are studied as a function of alloy composition for x=0–0.52. Experimental data indicate that the manganese acceptor level is pinned to the vacuum level for the range of alloy compositions studied.
Chemical vapor deposition of a silicon nitride layer with an excellent interface by NH3 plasma treatment
Authors: Shimoda Sugirou , Shimizu Isamu , Migitaka Masatoshi
Published: July 2002

A new metal-insulator-semiconductor field-effect transistor (MISFET) fabrication technology has been developed by using a silicon nitride insulator. MISFET’s with high field-effect mobility were obtained by exposing a silicon surface to a NH3 plasma before silicon nitride (SiNx) deposition as a gate insulator in a rf plasma. An Auger spectrum showed possible nitridation of silicon by NH3 plasma treatment.
Laser-induced homoepitaxy of GaP
Authors: Solanki R. , Sudarsan U. , Johnson J. C.
Published: July 2002

Laser-induced pyrolytic process is utilized to ‘‘direct write’’ epitaxial GaP structures. The precursors used were trimethylgallium and tertiarybutylphosphine, a new phosphorus donor. Dependence of the epitaxial growth on several deposition parameters is examined.
Parasitic-free measurement of the fundamental frequency response of a semiconductor laser by active-layer photomixing
Authors: Newkirk Michael A. , Vahala Kerry J.
Published: July 2002

We report the measurement of the fundamental (intrinsic) frequency response of a GaAs semiconductor laser to 12 GHz by directly photomixing two optical sources in the active region of the laser. This novel technique reveals the underlying fundamental frequency response of the device as parasitic effects are avoided. Well beyond the relaxation resonance, the theoretically predicted 40 dB/dec signal rolloff is observed. Other features of the measured response function are also observed to be the theoretical ideal.
Chemical ordering in GaxIn1−xP semiconductor alloy grown by metalorganic vapor phase epitaxy
Authors: Bellon P. , Chevalier J. P. , Martin G. P. , Dupont-Nivet E. , Thiebaut C. , André J. P.
Published: July 2002

GaInP films grown by metalorganic vapor phase epitaxy on GaAs substrates are observed by transmission electron microscopy in cross sections. A 1/2 (111) (CuPt type) ordering is observed, for the first time in this system, with only two orientation variants occurring. A layered structure (layer thickness 2 nm) develops parallel to the substrate and extra diffuse scattering is also observed at 2/9 (220). The observation of the 1/2 (111) ordering is not predicted by the current first-principle phase diagram calculations. Substrate effects on the orientation and number of ordering variants are identified.
Threshold voltage of charge storage in acoustic-charge-transport devices: Experiments and model
Authors: Schmukler Bruce , Hoskins Michael J.
Published: July 2002

This letter presents a simple theory to calculate the threshold voltage of charge storage in acoustic-charge-transport devices and experimental results that correlate well with the theory. It is found both experimentally and theoretically that the threshold voltage of charge storage increases with increasing surface acoustic wave power and nominal charge-transport depth. The threshold voltage of charge storage is also shown to be relatively independent of the amount of charge stored and is shown to decrease with increasing negative bias on the charge-storage electrode.
Effects of filament and reactor wall materials in low-pressure chemical vapor deposition synthesis of diamond
Authors: Singh B. , Arie Y. , Levine A. W. , Mesker O. R.
Published: July 2002

Well-faceted diamond crystals and polycrystalline films have been produced by low-pressure, hot-filament-activated, chemical vapor deposition with the use of methane/ hydrogen gas. The effects on growth and morphology of varying filament and reactor tube materials as well as tube diameter are reported. Tungsten and tantalum filaments, operated under similar conditions, produced diamonds at essentially the same growth rates (typically ∼2 μm/h) and with similar crystallographic properties. Platinum filaments produced only graphitic deposits. Diamond growth and morphology appeared not to be influenced by changing the reactor wall material from fused quartz to Al2O3 or Pyrex or by varying the tube diameter.
Photoluminescence studies of silicon-on-insulator substrates formed by oxygen implantation
Authors: Davey S. T. , Davis J. R. , Reeson K. J. , Hemment P. L. F.
Published: July 2002

Photoluminescence spectroscopy has been used to study silicon-on-insulator substrates formed by oxygen implantation. Samples having post-implantation anneals at 1200 and 1300 °C were investigated. The dislocation-related D-line emission is observed in all the samples, but with lower intensity in the samples annealed at the higher temperature, indicative of their superior crystal quality. Group V contaminants in some samples were identified from their excitonic emission. Additional low-temperature anneals at 450 and 750 °C significantly increased the intensity of the excitonic emission from the samples, and in addition, emission from thermal donors was also observed.
Materials choice for ballistic transport: Group velocities and mean free paths calculated from realistic band structures
Authors: Krishnamurthy Srinivasan , Sher A. , Chen A.-B.
Published: July 2002

We studied the effects of realistic band structures on the group velocities and mean free paths due to scattering by longitudinal optical phonons, ionized impurities, alloy disorder, and other electrons on limiting ballistic transport in GaAs, InAs, InP, GaInAs, GaAlAs, and InAsP alloys. The upper cutoff frequency and fraction of ballistic electrons transporting through devices made from these materials are calculated. For thick devices (≥500 Å), GaInAs alloys have distinct advantages. However, for thin devices (≊100 Å), the cutoff frequencies range around 15 THz, and none of the materials have an appreciably higher ballistic fraction than GaAs.
Anomalous co-diffusion effects of germanium on group III and V dopants in silicon
Authors: Pfiester J. R. , Griffin P. B.
Published: July 2002

Anomalous diffusion effects are observed when germanium is co-diffused with phosphorus, boron, or arsenic in inert or oxidizing ambients. The germanium, an uncharged column IV dopant with a covalent radius close to that of silicon, appears to alter the point defect population in the silicon lattice. During oxidation, the usual oxidation enhanced diffusion is not observed when Ge is present in the lattice. The anomalous tail diffusion of high-concentration phosphorus is also reduced when Ge is present.
Birefringent channel waveguides defined by impurity-induced superlattice disordering
Authors: Kapon E. , Stoffel N. G. , Dobisz E. A. , Bhat R.
Published: July 2002

The waveguiding characteristics of GaAs/AlGaAs channel waveguides defined by silicon-induced superlattice disordering were investigated at 1.15 μm wavelength. These waveguides guide laterally only TE-polarized light. Because of the birefringence of the superlattice core of the waveguide, only the TE mode experiences a positive refractive index step between the unmixed and disordered superlattices. The TM mode, on the other hand, experiences a negative refractive index step resulting in antiguiding. The operation of these waveguides as efficient waveguide polarizers is demonstrated.
Photoluminescence identification of residual donors in undoped GaAs grown by metalorganic chemical vapor deposition
Authors: Watkins S. P. , Haacke G. , Burkhard H.
Published: July 2002

A photoluminescence technique was used to identify residual donors in the 1014 cm−3 range in high-purity GaAs grown by metalorganic chemical vapor deposition. The measurements were taken at zero magnetic field. A narrow-linewidth tunable laser was used to resonantly enhance a specific narrow-linewidth ‘‘two-electron’’ satellite line of the donor-bound exciton, enabling determination of the 1s-to-2s donor energy separations. Ge was identified as the dominant residual donor. Lower levels of the donors X1 and X2 were observed in some samples. These are attributed to Si (or possibly Sn) and S donors.
Unusual room-temperature intermixing and oxidation in copper deposited on a fluorinated amorphous silicon system
Authors: Cytermann C. , Brener R. , Sacher E. , Pratt B. , Weil R.
Published: July 2002

The room-temperature behavior of Cu thin films on crystalline and amorphous silicon (c-Si and a-Si) substrates was studied by Auger electron spectroscopy. All samples, except Cu/ a-Si:F, behaved as usual metal on silicon systems. It was found that F greatly enhances Cu-Si intermixing which proceeds up to the sample surface. After prolonged room-temperature exposure to air, this system settles into the unusual configuration: Cu/SiO2/a-Si:F. The effect is explained in terms of the permeability of Cu3Si to oxygen and the low solubility of Cu in SiO2.
Photoluminescence studies of selective-area molecular beam epitaxy of GaAs film on Si substrate
Authors: Lee Henry P. , Wang Shyh , Huang Yi-He , Yu Peter
Published: July 2002

GaAs films have been grown on Si substrates patterned with SiN by molecular beam epitaxy. The pattern consists of bare Si stripe of width ranging from 10 to 100 μm surrounded by SiN on both sides and a reference area of bare Si. 77 K photoluminescence (PL) spectrum and intensity are measured on the single crystalline GaAs films grown on these stripes and the reference area. For 1.5- and 3-μm-thick films, PL intensity from the 10 μm stripe shows 140% and 75% increase over the reference area, respectively. This remarkable increase in the PL intensity is believed due to the reduction of dislocations inside the window area. The improvement in the optical quality makes selective-area molecular beam epitaxy a very attractive technique for the fabrication of optical devices on Si substrate.