bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of a solid lubricant in boron carbide by nitrogen ion implantation and laser annealing
Authors: Reeber Robert R. , Kusy Robert P. , Yu Ning , Chu Wei-Kan
Published: July 2002

A boron nitride(lubricant)/boron carbide composite (approximately 70% boron nitride) has been formed in approximately the first 750 Å of surface and near-surface regions of a polycrystalline boron carbide sample by implanting nitrogen (N) ions at 100 keV with a total dose of 4×1017 N ions/cm2 followed by xenon chloride laser annealing. The composition and the profile of the boron, carbon, and nitrogen in the sample at various stages were determined by Rutherford backscattering spectrometry. During laser annealing, the deeply implanted N atoms diffused back toward the heated surface with about 50% of them remaining in the near-surface region. Argon sputtering and x-ray photoelectron spectroscopy measurements confirmed the formation and distribution of boron nitride.
Dark current and diffusion length in InGaAs photodiodes grown on GaAs substrates
Authors: Ishimura E. , Kimura T. , Shiba T. , Mihashi Y. , Namizaki H.
Published: July 2002

In0.53Ga0.47As photodiodes grown on GaAs substrates have been fabricated and analyzed. The dislocation density in the InGaAs layer is 2×107 cm−2. A lowest dark current of 3.8×10−4 A/cm2 at 10 V bias is obtained, which is very stable during a bias-temperature test of Vb=−10 V, T=175 °C, and t=100 h. The quantum efficiency is more than 85% at λ=1.3 μm. This device is expected to be practically used. The dark current has been successfully explained by the thermionic emission and thermionic field emission from traps at midgap. The diffusion length of holes in the InGaAs layer is explained by the recombination at dislocations with the finite recombination velocity of S∼104 cm/s.
Nonplanar silicon oxidation in dry O2+NF3
Authors: Imai K. , Yamabe K.
Published: July 2002

Nonplanar silicon oxidation in a dry O2+NF3 gas mixture has been investigated. Oxide morphologies at silicon corners following 800 °C oxidation in dry O2 and in dry O2+NF3 gas are observed using a scanning electron microscope. While a serious decrease in oxide thickness at convex silicon corners is observed following oxidation in dry O2, no inhibition of oxide growth occurs and the Si/SiO2 interface is smoothly rounded off at the corners following oxidation in dry O2+NF3. The effects of adding NF3 gas to a dry O2 atmosphere on nonplanar oxidation are discussed. Furthermore, a sacrificial oxidation in dry O2+NF3 prior to forming the thin capacitor oxide is found to be very effective for reducing the oxide leakage current for a trenched capacitor.
Critical thickness in epitaxial CdTe/ZnTe
Authors: Cibert J. , Gobil Y. , Dang Le Si , Tatarenko S. , Feuillet G. , Jouneau P. H. , Saminadayar K.
Published: July 2002

The critical thickness for coherent growth of CdTe on ZnTe by molecular beam epitaxy is assessed by reflection high-energy electron diffraction, low-temperature photoluminescence, and transmission electron microscopy. The value is found to be 5 monolayers for this high mismatch system (6%). As opposed to similar studies on III-V and Si-Ge systems, there is no evidence of island formation before relaxation by dislocations at the interface.
High-conductance customized copper interconnections produced by laser seeding and selective electrodeposition
Authors: Gupta Arunava , Chen C. Julian
Published: July 2002

We report a two-step process for producing high-conductance customized copper interconnections utilizing a localized electrodeposition process induced by Joule heat at a constriction. An initial metal interconnection is made by localized decomposition of an organometallic film using a focused laser beam. The conductance of such an initial interconnection can be low, but is enough to induce localized copper deposition by passing an ac current through the entire line in a copper-containing electrolyte. The interconnections produced by this process are solid, continuous, and highly conducting.
Bulk semiconductor saturable absorber for a NaCl color center laser
Authors: Soccolich C. E. , Islam M. N. , Young M. G. , Miller B. I.
Published: July 2002

Using bulk InGaAsP as a saturable absorber we have passively mode locked a NaCl color center laser to produce transform-limited, pedestal-free pulses near 1.6 μm as short as 197 fs with up to 4.2 kW peak power. Our results simplify the saturable absorber material requirements and prove that excitons are not required for generating subpicosecond pulses. By comparing a dozen samples we find that a minimum band-edge absorbance of 40% is required to generate subpicosecond pulses, although details of the band edge are not critical. In addition, we find stable mode locking always occurs on the long-wavelength side of the laser gain peak.
Stimulated visible light emission from ultrathin GaAs single and multiple quantum wells sandwiched between indirect-gap (Al0.49Ga0.51As) confining layers
Authors: Lee J. H. , Hsieh K. Y. , Hwang Y. L. , Kolbas R. M.
Published: July 2002

Spontaneous and stimulated emission from a series of Al0.7Ga0.3As -Al0.49Ga0.51As-GaAs ultrathin single [1,2, and 3 monolayer (ML), 1 ML=2.83 Å] and multiple (2 ML) quantum well separate confinement heterostructures are demonstrated and compared to a control sample (0 ML). Spectra from sample to sample are very different and depend on the alignment of the n=1, Γ electron bound state in the quantum well with the Xminima (lowest band edge) in the indirect-gap (Al0.49Ga0.51As) confining layers. Some samples (3 ML single and 2 ML multiple quantum well) can support stimulated emission despite the fact that the quantum well is undoped, unstrained, and very thin (Lz ≪scattering path length) and that most of the wave function is in the indirect-gap confining layers. These experimental results can be explained using a simple model based on the spatial extent of the wave function (rather than the well width) under the special condition of band alignment between the Γ and X states.
Optical waveguide intensity modulators based on a tunable electron density multiple quantum well structure
Authors: Zucker J. E. , Wegener M. , Jones K. L. , Chang T. Y. , Sauer N. , Chemla D. S.
Published: July 2002

With a recently developed semiconductor heterostructure it has become possible to tune continuously the electron density in multiple quantum wells. Here we demonstrate the first electro-optic waveguide intensity modulators based on this concept. We achieve a 22 dB on/off ratio for 9 V applied at 1.54 μm wavelength in a rib waveguide electroabsorption modulator. Electrorefractive devices include a waveguide Mach–Zehnder interferometer with an active length 650 μm operating at 1.58 μm wavelength with 5.4 V half-wave voltage. We show that the operating voltage can be further reduced by operating the Mach–Zehnder modulators in push-pull configuration.
Dual-wavelength multiple quantum well n-i-p-i-n photodetector using an optically bistable abrupt absorption edge
Authors: Tokuda Yasunori , Kanamoto Kyozo , Abe Yuji , Tsukada Noriaki
Published: July 2002

A novel method for wavelength-selective demultiplexing photodetection, making use of an extremely abrupt absorption edge of the optical bistability, has been proposed. As a demonstration of the principle, experimental data are presented on the dual-wavelength selectivity of an n-i-p-i-n photodetector with two intrinsic detection regions composed of GaAs/AlAs multiple quantum wells.
Single-crystalline aluminum layer buried in α-Al2O3
Authors: Ohkubo Masataka , Suzuki Noritomo , Hioki Tatsumi
Published: July 2002

Single-crystalline aluminum layer buried in α-Al2O3 has been synthesized by high-dose ion implantation of aluminum ions at an elevated temperature. It has been revealed by a high-resolution transmission electron microscope that the aluminum layer has interfaces which are remarkably smooth and abrupt within a few atomic layers. This observation is comparable to that in mesotaxy of silicides buried in silicon.
Radiative recombination in surface-free n+/n−/n+GaAs homostructures
Authors: Smith L. M. , Wolford D. J. , Venkatasubramanian R. , Ghandhi S. K.
Published: July 2002

We show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may both be enhanced by three to four orders of magnitude by the preparation of thin n+, doped layers at the surface and substrate interfaces. Samples were prepared by organometallic vapor phase epitaxy with n− region (∼1015 cm−3) thicknesses of 3–10 μm and n+ regions Si doped to concentrations of 5×1018 cm−3. Time-resolved luminescence in such structures (25–300 K), under both surface and bulk (near-band- edge) excitation conditions, reveals band-to-band-dominated recombination spectra, with carrier lifetimes ranging from a minimum of 150 ns at 50 K to 800 ns at room temperature. This is in sharp contrast to the subnanosecond lifetimes and poor raditive efficiencies typical in conventionally prepared, bulk or epitaxial GaAs, but is comparable to the best reported for high-purity LPE GaAs/AlxGa1−xAs double heterostructures.
Double-sided epitaxy of multiquantum well modulator arrays by molecular beam epitaxy
Authors: Scott E. G. , Rejman-Greene M. A. Z.
Published: July 2002

We report, for the first time, the growth of high quality InP/InGaAs multiquantum well modulator arrays on both the [100] and the [1̄00] faces of the same InP wafer using an indium-free wafer mounting technique in gas source molecular beam epitaxy.
Quantum well lasers with active region grown by laser-assisted atomic layer epitaxy
Authors: Chen Q. , Osinski J. S. , Dapkus P. D.
Published: July 2002

Laser-assisted atomic layer epitaxy (LALE) is used to locally deposit device-quality material for the first time, as demonstrated by successfully fabricating broad-area lasers with a GaAs quantum well grown in this way. By hybridizing LALE with conventional metalorganic chemical vapor deposition epitaxy, heterostructures are grown which allow characterization of material quality by photoluminescence and capacitance-voltage measurements. In addition, graded-index separate-confinement heterostructure lasers with threshold current densities of 650 A/cm2 for 580-μm-long devices were made using the LALE quantum well deposit, while devices made away from the deposit did not lase.
Excimer laser induced etching of InP
Authors: Donnelly V. M. , Hayes T. R.
Published: July 2002

We report 193 nm ArF excimer laser induced etching of InP in Cl2. Etching occurs by desorption of an In-chloride layer, as evidenced by an etch rate which increases linearly with laser repetition rate and is nearly pressure independent between 2 and 50 mTorr Cl2. At substrate temperatures near 150 °C, the etch rate increases above a ‘‘threshold’’ fluence of 0.02 J/cm2 and saturates at 2.3 Å/pulse by ∼0.12 J/cm2, corresponding to nearly one monolayer of InP removed per laser pulse. On samples masked with SiO2 stripes, etched surfaces were smooth, with little or no undercutting of the mask edge. Sidewalls on etched features slope out at a ∼45° angle. Etching mechanisms and implications for in situ processing are discussed.
Effect of nucleation mechanism on planar defects in InAs on Si (100)
Authors: Choi C.-H. , Hultman L. , Ai R. , Barnett S. A.
Published: July 2002

Suppression of three-dimensional (3D) island nucleation during growth of InAs on Si (100), achieved by using very low energy, high-flux Ar ion irradiation, reduced planar defect densities. For 13 eV ion irradiation, 3D islands nucleated after ∼2 monolayers (ML) of deposition, similar to conventional molecular beam epitaxy. High-resolution transmission electron microscopy studies of nominally 18-ML-thick films showed 3D InAs islands with {111} facets. A high density of {111} twins and stacking faults was observed adjacent to many of the {111} facets. Most of these defects propagated into the film upon further growth. When nucleation was carried out with 28 eV ion irradiation, flat InAs films were observed for thicknesses up to ∼10 ML. The 3D islands that nucleated at higher thicknesses were flatter with less faceting than in the 13 eV case. The density of planar defects in the initial nucleation layer and in thicker InAs films was reduced when 3D island nucleation was suppressed. These results indicate that planar defects formed directly on the {111} facets of the 3D islands.
Vertical monolithic integration of a GaAs/AlGaAs V-channeled substrate inner stripe laser diode and a heterojunction bipolar transistor
Authors: Jan Yu-Heng , Lee Si-Chen
Published: July 2002

A GaAs/AlGaAs V-channeled substrate inner stripe laser diode has been successfully integrated with a GaAs/AlGaAs heterojunction bipolar transistor in a vertical configuration for the first time. An ‘‘effective’’ threshold current (base current) as low as 8 mA was obtained. The maximum power output was beyond 5 mW per facet and the single longitudinal mode operation was achieved.
Creation of p-n junction in Hg0.3Cd0.7Te
Authors: Barbot J. F. , Kronewitz J. , Schröter W.
Published: July 2002

We have used local plastic deformation and electron irradiation to create p-n junctions in Hg0.3Cd0.7Te. The electron induced current mode of scanning electron microscopy was used to detect the local conversion from p type to n type. Control experiments with CdTe and independent results show that the migration of interstitial mercury and its reaction with an acceptor must be responsible for the observed conversion.
Copper-oxygen intercalation and related phase transformations in YBaCuO
Authors: Fendorf M. , Burmester C. P. , Wille L. T. , Gronsky R.
Published: July 2002

Phase transformations in the system Y2Ba4Cu6+xO14+x (0≤x≤4) are investigated by high-resolution transmission electron microscopy (TEM) and static lattice Monte Carlo computer simulations. Micrographs reveal dislocations and stacking faults associated with the diffusion of copper and oxygen as the stoichiometric parameter x varies locally during a phase transformation, and these defects are accurately reproduced by the calculations in ‘‘snapshots’’ of the simulated structures. In addition, the simulations show the occurrence of the well known YBa2Cu3O7, YBa2Cu4O8, and Y2Ba4Cu7O15 phases and predict the formation of Y2Ba4Cu9O17 and YBa2Cu5O9 structures at higher oxygen partial pressures. Based on experimental images and Monte Carlo results, an atomic mechanism involving the intercalation and removal of extra CuO planes by partial dislocation climb is proposed for changes in the layered YBaCuO crystal structure.
Preparation and critical current density of Bi2Sr2Ca2Cu3O10+x superconducting whiskers
Authors: Matsubara Ichiro , Tanigawa Hideo , Ogura Toru , Yamashita Hiroshi , Kinoshita Makoto , Kawai Tomoji
Published: July 2002

The whiskers of the Bi2Sr2Ca2Cu3O10(2223) phase have been prepared by heating the Bi2Sr2CaCu2O8(2212) whiskers inside of a calcined Bi2Sr2Ca4Cu6Pb0.5Ox powder. Temperature and magnetic field dependence of the critical current density (Jc) have been measured. The whisker yields a maximum Jc of 7.3×104 A/cm2 at 77 K, and higher than 1×104 A/cm2 below 96 K in zero applied field. At 77 K the 2223 whisker shows Jc values above 1×104 A/cm2 up to 1 T, in contrast to the 2212 whisker (1×102 A/cm2, B=1 T) which shows the steep decrease of Jc in magnetic field above 0.2 T.
Low-threshold high-efficiency high-yield impurity-induced layer disordering laser by self-aligned Si-Zn diffusion
Authors: Zou W. X. , Law K-K. , Gossard A. C. , Hu E. L. , Coldren L. A. , Merz J. L.
Published: July 2002

Stripe geometry lasers defined by impurity-induced layer disordering (IILD) have been fabricated utilizing a novel technology of self-aligned Si-Zn diffusion from which both optical and electrical confinements are obtained simultaneously. The fabrication process is considerably simpler than that for the conventional IILD lasers and the parasitic p-n junction area in the laser structures is minimized. Typical lasers with threshold current Ith=5.2 mA and differential quantum efficiency ηd=81% at room-temperature continuous operation as well as highly uniform yield ≳80% have been obtained.
Infrared absorption in n-type ZnSe/GaAs heteroepitaxial films
Authors: Deneuville A. , Lindauer G. , Tanner D. B. , Park R. M. , Holloway P. H.
Published: July 2002

We report on the variation of the absorption coefficient αf with wave number W, for Cl-doped n-type (9.4×1016–8×1018 cm−3) ZnSe epitaxial films grown on GaAs. Below the classical mid-infrared range of W, αf has large values (1.6×103–2.11×104 cm−1) appropriate for thin-film measurements, with αf proportional to W−p. Large variations of αf and p occur as a function of the free-electron concentration. The results are compared to a recent theoretical model by Ruda [J. Appl. Phys. 61, 3035 (1987)], which is specific to ZnSe.
Effect of light on the DX centers in Si- and Te-doped GaAlAs
Authors: Seguy Patrice , Yu Peter Y. , Li Ming-fu , Leon Rosa , Chan K. T.
Published: July 2002

Deep level transient spectroscopy (DLTS) and constant temperature capacitance transient measurements have been performed on the DX centers under light illumination in GaAlAs alloys doped with Si and Te. Assuming that the effect of light is to ionize the DX centers, experimental DLTS spectra have been simulated numerically. The stimulated spectra reproduces qualitatively the spectra in Te-doped samples only. In Si-doped samples, the stimulated spectra cannot reproduce the light-induced peak reported recently by Jia et al. [J. Appl. Phys. 66, 5632 (1989)]. Our results confirm that this peak may be associated with a light-induced metastable center related to Si in GaAlAs.
Silicon epitaxial growth on silicon-on-insulator structures by rapid thermal processing chemical vapor deposition
Authors: Hsieh T. Y. , Jung K. H. , Kwong D. L.
Published: July 2002

We have used rapid thermal processing chemical vapor deposition (RTPCVD) for silicon epitaxial growth on silicon-on-insulator (SOI) substrates. The surface morphology of SOI rapid thermal annealed in different ambients was also examined. A short, high-temperature H2 anneal formed an undulating SOI surface, which planarized after RTPCVD. However, severe surface pitting was observed after a high-temperature N2 anneal. No significant changes in the defect density of the silicon layers occurred after RTPCVD and no stacking faults were observed in the epilayers.
Unintentional indium incorporation in GaAs grown by molecular beam epitaxy
Authors: Myers D. R. , Dawson L. R. , Klem J. F. , Brennan T. M. , Hammons B. E. , Simons D. S. , Comas J. , Pellegrino J.
Published: July 2002

We have quantified unintentional indium incorporation in GaAs grown by molecular beam epitaxy in a variety of commercial systems. We find that the unintentional indium density in the epitaxial GaAs is more a function of mounting technique and prior machine history than of the manufacturer’s design. The indium densities detected in the epitaxial GaAs for substrates that only partially obscure an indium-bearing mount are equal to levels reported to result in minimum defect densities and narrowest photoluminescence linewidths in In-doped GaAs.
Characterization of SiGe/Si heterostructures formed by Ge+ and C+ implantation
Authors: Fukami Akira , Shoji Ken-ichi , Nagano Takahiro , Yang Cary Y.
Published: July 2002

Formation of SiGe/Si heterostructures by germanium ion implantation was investigated. A germanium-implanted layer was grown epitaxially in the solid phase by thermal annealing. Two kinds of crystalline defects were observed. One is a misfit dislocation, and the other is a residual dislocation caused by ion bombardment. The p-n junction formed in the SiGe layer has a leakage current three orders of magnitude larger than that of a pure Si p-n junction fabricated with an identical process except for the Ge+ implantation. Carbon doping in the SiGe layer improves its crystalline quality and the junction characteristics.
Novel indium oxide/n-GaAs diodes
Authors: Golan A. , Bregman J. , Shapira Y. , Eizenberg M.
Published: July 2002

Diodes with transparent top contacts were fabricated by depositing indium oxide layers onto n-type GaAs by means of reactive evaporation of In in the presence of oxygen. The electrical characteristics as well as the structural properties and chemical composition of the resulting junctions were studied using Auger electron spectroscopy, x-ray diffraction, optical absorption, capacitance-voltage, and dark current-voltage measurements. The best diodes were obtained under deposition conditions of substrate temperature 250 °C and oxygen pressure 5×10−4 mbar; these diodes exhibited a Schottky barrier height of 0.85 V with an ideality factor of 1.04. The indium oxide films were found to be polycrystalline and to have an electrical resistivity of 3×10−4 Ω cm and an optical transmittance above 90% over the whole visible range. The effect of deviations from the optimal deposition parameters on the diode properties is discussed.
Effects of strain in multiple quantum well distributed feedback lasers
Authors: Tanbun-Ek T. , Logan R. A. , Chu S. N. G. , Sergent A. M. , Wecht K. W.
Published: July 2002

A survey of graded-index separate confinement multiple quantum well distributed feedback lasers comparing the effects of strain in the quantum well upon threshold, output power, and linewidth is reported. Lasers with either compressive or tensile strained quantum wells and a long cavity length (890 μm) show lower threshold current (10–20 mA) as well as lower linewdith power product than lasers with unstrained quantum wells and have a comparable minimum linewidth to the unstrained quantum well lasers. A minimum linewidth as narrow as 900 and 440 kHz for compressive strain and unstrained quantum well lasers, respectively, was obtained at output power of 30 mW. Single longitudinal mode operation with a maximum output power over 80 mW was observed in all the structures.
Vertical-cavity surface-emitting lasers with semitransparent metallic mirrors and high quantum efficiencies
Authors: Tu Li-Wei , Schubert E. Fred , Kopf Rose F. , Zydzik George J. , Hong Minghwei , Chu S. N. George , Mannaerts Joseph P.
Published: July 2002

Semitransparent thin silver films are employed as both the top mirrors and electrodes for GaAs vertical-cavity surface-emitting lasers. The semitransparent silver films allow the emission of light from the top epitaxial side. Quarter-wave AlAs/AlxGa1−xAs stacks are used as the bottom n-type mirrors. Light output versus excitation current measurements yields an efficiency of 0.76 mW/mA from the top silver mirror side, which corresponds to an external differential quantum efficiency of 54% at a lasing wavelength of 0.88 μm. The internal differential quantum efficiency is estimated to be ≳94%. An optical output power of 10 mW is obtained at a pulsed excitation current of 72 mA.
Chemically enhanced self-sputtering of carbon
Authors: Davis J. W. , Haasz A. A.
Published: July 2002

New results obtained for graphite self-sputtering, in the presence of thermal atomic hydrogen, show that chemically enhanced self-sputtering (CES) can exceed unity erosion yield even at normal angles of incidence. CES yields were found to depend on the φC+/φH0 flux ratio and graphite temperature, with peak erosion occurring at about 800 K. No dependence on angles of incidence was observed.
Using decomposed disilane as a gas source for Si epitaxial growth on Ge (111): Photoemission studies
Authors: Van S. , Steinmetz D. , Ringeisen F. , Bolmont D. , Koulmann J. J.
Published: July 2002

A good Si epitaxial growth rate on Ge (111) has been achieved at substrate temperatures as low as 350 °C thanks to the use of decomposed disilane in the catalytic chemical vapor deposition (CTL-CVD) method. For substrate temperatures in the (100–200 °C) range, an exposure of the Ge (111) wafer to decomposed disilane led to the formation of an amorphous silicon film. The growth rate of this Si layer was found to be several times higher when using decomposed disilane rather than undecomposed disilane. At substrate temperatures above 400 °C, an interdiffusion of Si into Ge occurred in both cases of disilane and decomposed disilane exposures.
Growth of in situ doped silicon epitaxial layer by rapid thermal processing
Authors: Lee S. K. , Ku Y. H. , Hsieh T. Y. , Jung K. H. , Kwong D. L. , Spratt David , Chu P.
Published: July 2002

In this letter, rapid thermal processing chemical vapor deposition has been used to grow high quality in situ doped silicon epitaxial layers. Device quality epilayers have been obtained for both boron and phosphorus doping with abrupt dopant transition profiles. The mobility values of these doped epilayers are very close to the values for bulk silicon under the same doping concentration.
Single-mode semiconductor optical waveguides with large dimensions suitable for compact bend applications
Authors: Deri R. J. , Shahar A. , Colas E. , Thurston R. N. , Tomlinson W. J. , Yi-Yan A. , Seto M.
Published: July 2002

We demonstrate a novel waveguide structure for realization of integrated optics with compact waveguide bends (radii≊1 mm), low propagation loss (0.45 dB/cm), and large guide dimensions (5 μm width) to facilitate input coupling. Experimental results using single-mode GaAs/AlGaAs heterostructure guides at 1.52 μm wavelength are presented.
Temperature dependence of optical phase conjugation in semiconductor-doped glasses
Authors: Dutton T. , Dvornikov A. , Van Wonterghem B. , Rentzepis P. M.
Published: July 2002

We measured optical phase conjugation via low-power degenerate four-wave mixing at 532 nm as a function of temperature in semiconductor-microcrystallite-doped glasses. We find that the overall efficiency of the phase conjugation process increases with decreasing temperature and is temperature independent between 77 and 100 K. The results are interpreted as the combined effect of the increased transmission due to the increased band gap and an effective χ(3) which increased due to a decrease of the trapped carrier recombination rate.
Giant microwave losses in a YBaCuO bicrystal
Authors: Pakulis E. J. , Blum S. E.
Published: July 2002

We have observed a large peak in microwave losses, as a function of temperature, in a superconducting Y1Ba2Cu3O7 bicrystal containing a large-area, low-angle grain boundary. The maximum observed loss was approximately twice the normal state loss. We attribute the peak to enhanced losses occurring within the grain boundary due to the concentration of microwave field lines in the boundary as they are expelled from the superconducting regions. At high microwave powers, bistability in the absorption was observed, resulting in hysteretic absorption curves as a function of both T and magnetic field H.
Photoemission from thin-film lanthanum hexaboride
Authors: May P. G. , Petkie R. R. , Harper J. M. E. , Yee D. S.
Published: July 2002

Lanthanum hexaboride (LaB6) is investigated for its potential as a low work-function photocathode for high brightness e-beam applications. Thin films of LaB6 at room temperature are shown to have quantum efficiencies of 0.2×10−3 at 442 nm excitation but readily form an inhibiting oxide. This oxide is easily removed by in situ 500 eV Ar+ ion sputtering, which restores photoemission for over 30 min at an oxygen partial pressure of 10−9 Torr.
Onset of subharmonics generated by forward wave interactions in Bi12SiO20
Authors: Webb D. J. , Au L. B. , Jones D. C. , Solymar L.
Published: July 2002

The threshold conditions, under which a spatial subharmonic beam may arise when a Bi12SiO20 crystal is illuminated by two pump beams, are investigated. It is shown that a nonlinear theory based on the material equations leads to good qualitative agreement with experiments
Effect of annealing on superconductivity of Pb-doped Bi-Sr-Ca-Cu-O single-crystal superconductors
Authors: Gao Y. , Li Y. , Merkle K. L. , Jiang P. Z. , Chang Y. C. , Shi H. , Lam D. J.
Published: July 2002

The microstructure of high quality Pb-doped Bi2Sr2CaCu2Ox single crystals grown by the flux technique has been studied by transmission electron microscopy (TEM). The single crystals have a superconducting transition temperature (Tc) of about 90 K as grown; Tc drops to about 83 K after annealing in air at 600 °C. TEM results show that the as-grown crystals exhibit twinning. The twin boundaries were found to be parallel to the (100) and (010) lattice planes. However, upon annealing the twin structure disappeared. This microstructure change is discussed in terms of a possible cause for the Tc decrease in the annealed crystals.
Bulk superconductivity in single CuO layer Bi-Sr-Cu-O ceramics
Authors: Schneemeyer L. F. , Sunshine S. A. , Fleming R. M. , Glarum S. H. , van Dover R. B. , Marsh P. , Waszczak J. V.
Published: July 2002

Despite early recognition that a relatively low-temperature superconductor occurs in samples of approximate composition Bi2Sr2CuO6, studies of this material have been plagued by difficulties in the preparation of single phase material with a large superconducting fraction. We report the first preparation of ceramic samples in the Bi-Sr-Cu-O system that show bulk superconductivity at 4–15 K. Structural, chemical, and electronic characterizations of superconducting and nonsuperconducting ceramics of composition Bi2.05Sr1.95CuO6 are described.
YBa2Cu3O7−δ-Ag-Al/Al2O3/Pb tunnel junctions based on the superconducting proximity effect
Authors: Gijs M. A. M. , Scholten D. , van Rooy Th. , Gerrits A. M.
Published: July 2002

YBa2Cu3O7−δ-Ag-Al/Al2O3/Pb superconducting tunnel junctions with high subgap resistance were fabricated using the proximity effect induced superconductivity in the Ag-Al layer by the YBa2Cu3O7−δ film. At low temperature an energy gap of 9–10 meV is found to be induced in the aluminum layer. Above 20 K the induced gap disappears mainly due to the decreased normal metal coherence length. At higher voltages (V≤120 meV) the dynamic conductance dI/dV∝V, characteristic for the normal tunneling density of states of the oxide superconductor.
Patterned YBa2Cu3O7−x thin films from photopolymerizable precursors
Authors: Hung Yann , Agostinelli John A.
Published: July 2002

A technique which combines the fabrication and patterning of thin films of the high Tc superconductor YBa2Cu3O7−x has been developed. The technique possesses the essential features of the metalorganic decomposition method with the additional attribute that the metalorganic precursor is photopolymerizable. Patterns are generated directly in the precursor film using optical exposure through a mask followed by development in a solvent. A subsequent thermal treatment transforms the patterned precursor film to the oriented superconducting phase with c axis perpendicular to the substrate surface. Resistivity measurements for such a patterned film on a single crystal (100)MgO substrate show an onset to the superconducting state occurring at 85 K with zero resistivity below 67 K.
Novel integrated acousto-optic and electro-optic heterodyning device in a LiNbO3 waveguide
Authors: Xu G. D. , Tsai C. S.
Published: July 2002

A wideband integrated optic heterodyning device that utilizes simultaneously a wideband acousto-optic (AO) Bragg cell and a wide-angle electro-optic (EO) Bragg grating lens has been realized, for the first time, in a Y-cut LiNbO3 waveguide 1×8×20 mm3 in size. The device has demonstrated a bandwidth of 240 MHz centered at 350 MHz and a single-tone instantaneous and two-tone third-order spurious-free dynamic ranges of 44.6 and 36.0 dB, respectively, at the optical wavelength of 0.6328 μm. The device suggests a new and simple architecture for wideband integrated optic interferometric rf spectrum analyzers.
High performance surface-emitting lasers with 45° intracavity micromirrors
Authors: Ou S. S. , Yang J. J. , Jansen M. , Sergant M. , Mawst L. J. , Wilcox J. Z.
Published: July 2002

For the first time, high performance GaAs/GaAlAs surface-emitting lasers with internal 45° micromirrors, which totally reflect and emit the beam from the substrate in junction-down configuration, have been demonstrated. The 45° and 90° mirrors of the device were fabricated by using ion milling and reactive ion etching techniques, respectively. Typical threshold current density of 440 A/cm2, external differential efficiencies of 52%, and output power in excess of 1 W under quasi-cw operation have been achieved.
Disorder of ZnSe/ZnS strained-layer superlattices by N+ or Li+ ion implantation and low-temperature annealing
Authors: Yokogawa Toshiya , Saitoh Tohru , Narusawa Tadashi
Published: July 2002

We demonstrate layer disordering of ZnSe/ZnS strained-layer superlattices (SLSs) induced by low-damage N+ or Li+ ion implantation and low-temperature annealing. The interdiffusion of Se and S atoms was observed by secondary-ion mass spectrometry analyses. By reflectance measurements, a significant decrease in the refractive index, which is useful for waveguiding applications, was measured in the disordered SLS. In photoluminescence (PL) spectra, strong excitonic emission around 400 nm was observed in the disordered SLS corresponding to a damage recovery. A slight red shift of the PL peak observed in the early stages of annealing is interpreted as the relaxation of misfit strain by interdiffusion. For longer annealing times, the PL peak for an implanted SLS shifted towards the higher energy side, which clearly indicates layer disordering of the SLSs. This low-temperature planar process will be very useful for the fabrication of II-VI semiconductor optoelectronic devices.
Electrical characterization of GaAs PiN junction diodes grown in trenches by atomic layer epitaxy
Authors: Neudeck P. G. , Kleine J. S. , Sheppard S. T. , McDermott B. T. , Bedair S. M. , Cooper J. A. , Melloch M. R.
Published: July 2002

We report the electrical characterization of GaAs PiN junction diodes grown over the sidewalls of patterned trenches by atomic layer epitaxy. The diodes exhibit excellent rectifying behavior demonstrating that high quality GaAs was grown on the entire trench structure including sidewalls and corners. The sidewall material is characterized electrically through reverse bias diode leakage from thermal generation in the depletion region. 2-μm-deep trenches contribute a leakage current of less than 60 μA/cm2 of sidewall area under 1 V reverse bias at 144 °C, which is satisfactory for most device applications.
Plasma-enhanced chemical vapor deposition of low-resistive tungsten thin films
Authors: Kim Yong Tae , Min Suk-Ki , Hong Jong Sung , Kim Choong Ki
Published: July 2002

Controlling the wafer temperatures from 200 to 500 °C at H2/WF6 flow ratio equal to 24, low-resistive (about 11 μΩ cm) tungsten thin films are deposited by plasma-enhanced chemical vapor deposition. The as-deposited tungsten films have (110), (200), and (211) oriented bcc structures and Auger depth profile shows that fluorine and oxygen impurities are below the detection limit of Auger electron spectroscopy.
Amorphous-deposited polycrystalline silicon for contact-hole plugs
Authors: Drynan J. M. , Kikkawa T.
Published: July 2002

Silicon films deposited using the low-pressure chemical vapor deposition method at deposition temperatures between 500 and 540 °C are amorphous and exhibit better contact-hole coverage than those deposited at higher temperatures. Phosphorus diffusion and annealing transform these low-temperature amorphous films into polycrystalline ones with dominant (111) crystal orientations and resistivities in the range of 3×10−3 Ω cm, whereas films deposited at higher temperatures have both (111) and dominant (220) crystal orientations and resistivities in the range of 13×10−3 Ω cm.
Electrical characterization of InxGa1−xAs/Al0.4Ga0.6As/GaAs pseudomorphic semiconductor/insulator/semiconductor heterostructures
Authors: Collot P. , Barbier E. , Schmidt P. E. , Arnodo C. , Gaonach C. , Favre J.
Published: July 2002

Two pseudomorphic InxGa1−xAs/Al0.4Ga0.6As/GaAs semiconductor/insulator/ semiconductor heterostructures (PM-SIS) with indium mole fractions x=0.15 and 0.25 were investigated and compared to a conventional GaAs/AlGaAs/GaAs SIS structure by means of current-temperature and capacitance-voltage characterizations. High reduction in gate leakage current is observed in the pseudomorphic structures compared with the conventional one. The conventional SISs is normally off, while the PM-SISs are normally on with a sheet carrier density at 0 V of 1.8×1011 cm−2 and 2.2×1011 cm−2 with x=0.15 and 0.25, respectively.
Action of copper indium diselenide photoelectrochemical cells
Authors: Chu J. W. , Haneman D.
Published: July 2002

It is shown that long-term operation of photoelectrochemical cells with CuInSe2 polycrystalline photoelectrodes in standard HI-based electrolytes, can leave the surfaces clean and stoichiometric. Formation of a surface heterojunction is not necessary. The key factor is the ensurement of sufficient stirring of the electrolyte to prevent growth of CuI and other crystallites. Even when these occur, the underlying surface can remain stoichiometric and there is no iodine-containing surface layer. The cells can therefore act as Schottky diodes and not as heterojunctions.
Local distribution of deep centers in GaP studied by infrared cathodoluminescence
Authors: Domínguez-Adame F. , Piqueras J. , Fernández P.
Published: July 2002

Near-infrared cathodoluminescence (CL) in the scanning electron microscope has been used to characterize GaP:S. Spectra of as-grown crystals show a broadband at about 1240 nm, probably related to PGa antisite defects. This emission has been found to be higher at dislocations giving a CL image opposite to the visible CL image.
Determination of the gain nonlinearity time constant in 1.3 μm semiconductor lasers
Authors: Eom J. , Su C. B. , Rideout W. , Lauer R. B. , LaCourse J. S.
Published: July 2002

By comparison of the measured K factors (ratio of the damping factor to the square of the resonance frequency) of distributed feedback and Fabry–Perot lasers, it is found that the relaxation time associated with nonlinear gain for 1.3 μm InGaAsP lasers is about 0.1 ps. This short time constant is consistent with spectral hole burning being the dominant process responsible for the nonlinear gain.
Ferroelectric properties of lead-zirconate-titanate films prepared by laser ablation
Authors: Kidoh Hideo , Ogawa Toshio , Morimoto Akiharu , Shimizu Tatsuo
Published: July 2002

Ferroelectric lead-zirconate-titanate (PZT) thin films have been deposited by excimer laser ablation on sapphire substrates with and without an electrode. In preparation for the films, O2 gas pressure has greatly influenced the film structure and morphology. For the first time, we have confirmed the ferroelectric properties of PZT films prepared by laser ablation without post-annealing. It appears to be possible to use these films for nonvolatile random access memories with some additional improvements in the film properties.
Compositional effects on plasma-enhanced metalorganic chemical vapor deposition of YBa2Cu3O7−x thin films
Authors: Zhao J. , Chern C. S. , Li Y. Q. , Norris P. , Gallois B. , Kear B. , Wu X. D. , Muenchausen R. E.
Published: July 2002

Epitaxial YBa2Cu3O7−x superconducting thin films with a zero resistance transition temperatures of about 90 K have been prepared, in situ, on LaAlO3 by a plasma-enhanced metalorganic chemical vapor deposition process at a substrate temperature of 670 °C in 1 Torr partial pressure of N2O. The composition of the films was varied systematically to investigate the effect of changes in the Ba/Y and Cu/Y ratio on the film properties. The results indicated that superconducting current densities exceeding 106 A/cm2, measured at 77 K by a transport method, could be obtained on films with an anomalously wide range of film compositions. Excess Cu (up to 60%) and deficiency in Ba (down to 30%) from their stoichiometric values did not significantly degrade the superconducting properties of the films. As the composition approached the Y-Ba-Cu ratio of 1-2-3, an improvement in surface morphology and a decrease in superconducting transition temperature were found.
Structural properties of CdTe-ZnTe strained-layer superlattice grown on GaAs by hot-wall epitaxy
Authors: Sugiyama I. , Hobbs A. , Ueda O. , Shinohara K. , Takigawa H.
Published: July 2002

CdTe-ZnTe strained-layer superlattices (SLSs) were grown on GaAs by hot-wall epitaxy. The individual layer thickness of the SLS is well controlled and the thickness fluctuation is less than ±1 monolayer. High-resolution transmission electron microscopy images show coherent SLS growth. We found that two-thirds of the threading dislocations can be reduced by inserting the SLS in CdTe/GaAs.
Fast nonlinear photoresponse of current biased thin-film Bi2Sr2CaCu2O8 to pulsed far-infrared radiation
Authors: Huggard P. G. , Schneider Gi. , O’Brien T. , Lemoine P. , Blau W. , Prettl W.
Published: July 2002

The response of a polycrystalline thin-film Bi2Sr2CaCu2O8 superconducting stripe to short-pulse far-infrared (λ=447 μm) radiation is reported. Under constant current bias, a photosignal is generated when the maximum zero voltage current is exceeded. Measurements of the sensitivity as a function of temperature, bias current, and intensity reveal the signal source to be nonbolometric. The response is found to obey a (power)1/2 law over more than 2 orders of magnitude. We believe the detection mechanism arises from the interaction of grain boundary Josephson junctions with radiation induced screening currents.
Polarization switching and bistability in an external cavity laser with a polarization-sensitive saturable absorber
Authors: Ozeki Y. , Tang C. L.
Published: July 2002

Polarization switching and hysteresis are observed in a semiconductor laser with a two-armed polarization-sensitive external cavity. An intracavity polarization-dependent saturable absorber is placed asymmetrically in one of the two arms of the external cavity so that one polarization mode is saturated more strongly than the other. The observed phenomena can be explained by the complementary processes of competition in the gain region and the polarization-dependent saturable loss in the external cavity. This mechanism is potentially useful as the basis of a two-mode switchable and bistable diode laser for applications as high-speed optical memories and logic gates.
High-power 1.48 μm multiple quantum well lasers with strained quaternary wells entirely grown by metalorganic vapor phase epitaxy
Authors: Joma M. , Horikawa H. , Matsui Y. , Kamijoh T.
Published: July 2002

This letter describes 1.48 μm multiple quantum well (MQW) lasers with strained GaInAsP quaternary wells entirely grown by metalorgainic vapor phase epitaxy. The GaInAsP quaternary layers with 1.5% biaxially compressed strain showed an excellent crystal quality and an abrupt interface within half-monolayer fluctuations which was verified with photoluminescence spectroscopy. The maximum continuous wave output power of 140 mW was obtained at 20 °C with 1500-μm-long lasers whose facets were coated by anti- and high-reflection films. The small internal loss of 12 cm−1 and a high internal efficiency of 70% were obtained.
Small-divergence electron beams produced by multiphoton excitation of metallic surfaces
Authors: Moustaizis S. D. , Tatarakis M. , Doukas A. G. , Fotakis C.
Published: July 2002

The angular distribution of photoelectrons produced by laser-induced four-photon excitation in gold metalic targets is reported. Laser-target interaction time effects have been investigated by using two Nd:YAG lasers emitting at 1.06 μm pulses of 35 ps and 20 ns duration. Both lasers produced four-photon electron angular distributions of 9°±2° full width at half maximum. This width was independent from the intensity of the picosecond laser up to the breakdown threshold at a laser intensity of 1.4 GW/cm2. In contrast, the distribution produced by the nanosecond pulses was broadened at intensity levels higher than 60 MW/cm2, which is indicative of a significant contribution from thermionic emission. These results are compared to those obtained by D. Charalambidis, E. Hontzopoulos, C. Fotakis, Gy. Farkas, and Cs. Tóth [J. Appl. Phys. 65, 2843 (1989)], for single photon excitation by using a KrF excimer laser.
Polytypic phase formation in DyAl3 by rapid solidification
Authors: Xu Yan , Altounian Z. , Muir W. B.
Published: July 2002

Amorphous ribbons of AlxDy100−x, 93≳x≳85, were obtained by melt spinning. During crystallization, in addition to Al, four different metastable crystalline phases of DyAl3 were observed. These phases are, in order of appearance, the high-pressure face-centered cubic phase, γ-DyAl3 and three polytypic rhombohedral phases, β-DyAl3, β′-DyAl3, and α′-DyAl3. It is the first time that the β′ phase in rare-earth trialuminides and the α′ phase in Dy-Al alloy system have been observed. It is shown that all these phases are associated with the polytypic packing of the hexagonal DyAl3 atomic layers. The relative stability of the phases is found to be related to the hexagonal to cubic stacking ratio in the structure.
Towards optimization and understanding of the photoelectronic properties in CuGaSe2
Authors: Balberg I. , Albin D. , Noufi R.
Published: July 2002

The photoconductivity and the minority-carrier diffusion length of CuGaSe2 were studied in the photocarrier grating configuration. In order to shed some light on the carrier recombination processes, both He-Ne and Ar-laser illuminations were used and the light was applied either to the substrate surface or to the free surface of the films. The substantial variation of the photoelectronic properties along the film growth axis, and their dependence on the light wavelength, are interpreted in terms of the polycrystalline nature of the films. It is suggested that by properly combining deposition conditions and composition one can get a significant improvement in the phototransport properties of these materials.
In-phase operation of high-power nonplanar periodic laser arrays
Authors: Bryan R. P. , Cockerill T. M. , Miller L. M. , Tang T. K. , DeTemple T. A. , Coleman J. J.
Published: July 2002

The transformation of nonplanar periodic laser array modes from weakly locked out-of-phase to locked in-phase operation is investigated. A comparison study of near-field and far-field patterns is made for devices with differing mesa widths and heights. Data are presented which show that the mesa height and width can be adjusted to force in-phase operation. An array of 19 elements shows an essentially single-lobed far-field pattern centered at 0° with full width at half maximum of 1.6°, to output powers of more than 500 mW/uncoated facet.
Carbon-hydrogen complex in GaP
Authors: Clerjaud B. , Côte D. , Hahn W-S. , Ulrici W.
Published: July 2002

The carbon-hydrogen complex in GaP is evidenced by the observation of the 12C-H, 13C-H, and 12C-D stretching local modes of vibration. Experiments performed with D2O enriched wet boric oxide encapsulant clearly shows that a source of hydrogen contamination during liquid-encapsulation Czochralski growth is the water contained in the encapsulant.
Low-threshold operation of a GaAs single quantum well mushroom structure surface-emitting laser
Authors: Yang Y. J. , Dziura T. G. , Fernandez R. , Wang S. C. , Du G. , Wang S.
Published: July 2002

Room-temperature continuous-wave (cw) lasing operation with a threshold current (Ith) of 3 mA and a pulsed Ith as low as 1.5 mA were achieved in mushroom structure surface- emitting lasers utilizing a 300 Å GaAs single quantum well as an active layer and an AlAs/Al0.1Ga0.9As multilayer as the top and the bottom distributed Bragg reflectors. A series resistance of 250 Ω was obtained on devices with an 8×8 μm2 active region using selective zinc diffusion. A differential quantum efficiency of 12%–20% and a maximum cw light output power exceeding 1 mW were achieved. The emission wavelength was 860 nm with a spectral linewidth of ∼0.5 Å.
Fast recovery of excitonic absorption bleaching in tunneling biquantum well structures
Authors: Tackeuchi Atsushi , Muto Shunichi , Inata Tsuguo , Fujii Toshio
Published: July 2002

This letter demonstrates the fast recovery from excitonic absorption bleaching in tunneling biquantum well structures. A tunneling biquantum well consists of a series of narrow and wide wells. Recovery time was reduced to 1 ps using 1.7-nm-thick tunneling barriers, three orders of magnitude shorter than the few nanoseconds recovery due to radiative recombination. This is the fastest tunneling process observed to date.