bluuebunny/crossref_metadata_2025 huggingface dataset:
Retarded diffusion of Sb in a high concentration As background during silicon oxidation
Authors: Perozziello E. A. , Griffin P. B. , Plummer J. D.
Published: July 2002

The effects of surface oxidation on the diffusion of antimony were studied in a constant electron concentration. An extrinsic arsenic background was used to provide a constant electron concentration for the diffusion of the antimony profile. Anneals were performed at 850, 950, and 1050 °C, and the resulting antimony diffusion was compared under inert and oxidizing conditions. The diffusion of the arsenic was also observed. Arsenic diffusion was enhanced while antimony diffusion inside the arsenic layer was retarded. These effects are direct evidence for a dual-defect (interstitial/vacancy) model for dopant diffusion and contradict vacancy-only diffusion models. A value for the energy barrier to interstitial-vacancy recombination and values of the interstitial component of Sb diffusion were extracted from the data.
Optical suppression of ionized impurity scattering in vertical hot-electron transport
Authors: Geim A. K. , Bending S. J. , Gueret P. , Meier H. P.
Published: July 2002

A striking effect of illumination on the vertical nonequilibrium electron transport has been observed in the GaAs-based tunneling hot electron transfer amplifier (THETA). Weak illumination can considerably increase the transparency of a THETA structure for quasiballistic electrons if the photon energy exceeds the GaAs band gap. The temperature and illumination intensity dependencies indicate that the effect is caused by photoneutralization of ionized impurities which are a major source of hot electron scattering.
2-picosecond, GaAs photodiode optoelectronic circuit for optical correlation applications
Authors: Li K. D. , Hou A. S. , Özbay E. , Auld B. A. , Bloom D. M.
Published: July 2002

An ultrafast GaAs Schottky photodiode is monolithically integrated with a microwave detector. By using this new optoelectronic circuit in place of a nonlinear crystal in an optical correlation setup, the high-speed photodiode can measure laser pulse durations without using expensive sampling oscilloscopes. Key advantages are that this circuit works over a broad wavelength range and at low peak optical powers. The correlated temporal response of the circuit is measured to be 1.9 ps full width at half maximum. Due to its wavelength flexibility, cross correlation with different lasers may be performed with this single device.
Picosecond electrical spectroscopy using monolithic GaAs circuits
Authors: Konishi Y. , Kamegawa M. , Case M. , Yu R. , Rodwell M. J. W. , York R. A. , Rutledge D. B.
Published: July 2002

This article describes an experimental apparatus for free-space mm-wave transmission measurements (spectroscopy). GaAs nonlinear transmission lines and sampling circuits are used as picosecond pulse generators and detectors, with planar monolithic bowtie antennas with associated substrate lenses used as the radiating and receiving elements. The received pulse is 270 mV amplitude and 2.4 ps rise time. Through Fourier transformation of the received pulse, 30–250 GHz measurements are demonstrated with ≤0.3 dB (rms) accuracy.
Polarization insensitive strained quantum well gain medium for lasers and optical amplifiers
Authors: Mathur Atul , Dapkus P. Daniel
Published: July 2002

1.3 μm In1−xGaxAsyP1−y/InP lasers with compressive and tensile strained quantum wells have been found to lase in both transverse electric (TE) and transverse magnetic (TM) polarizations. Amplified spontaneous emission spectra indicate gain in both TE and TM modes. The relative magnitudes depend on device length and injection current. This structure can be used as a polarization insensitive optical amplifier.
New technique to dope GaAs crystals with the 111In→111Cd probe for perturbed-angular-correlation spectroscopy
Authors: Adams James M. , Fu Jianming , Catchen Gary L. , Miller D. L.
Published: July 2002

Perturbed-angular-correlation (PAC) spectroscopy is an important technique for measuring defect and dopant interactions in group IV and III-V semiconductors. The probe of choice for most of the successful PAC experiments on semiconductors has been 111In→111Cd introduced by ion implantation. To expand the gamut of PAC experiments that can be performed on III-V semiconductors, we have developed a simple closed-tube, vapor-phase-epitaxy (VPE) technique to produce 111In-doped GaAs single-crystal epitaxial materials. PAC measurements on these crystals yielded nearly nonperturbed correlations that indicate that the 111In probe was incorporated substitutionally into the GaAs crystals. These correlations differ significantly from the previously reported weakly perturbed correlations that were measured on GaAs crystals implanted with 111In ions. An exploratory experiment using this VPE technique also showed that Sn can be incorporated along with 111In.
Novel electro-optical phase modulator based on GaInAs/InP modulation-doped quantum-well structures
Authors: Thirstrup C.
Published: July 2002

A novel electro-optical phase modulator working at 1.55 μm is analyzed and proposed. It is shown by a numerical model that in a GaInAs/InP pn-nin-pn multiple-quantum-well waveguide structure, large optical phase modulation can be obtained at small intensity modulation and with improved performance compared to what is achieved in quantum confined Stark effect modulators of the same material system. The device proposed is based on a modulation of the quasi-Fermi energies of the electrons in the GaInAs quantum wells. This operational principle allows GHz modulation frequencies.
Submillimeter wave response of a high T
c superconducting microbridge
Authors: Takeya Jun-ichi , Kawate Etsuo , Park Chan Hoon , Goto Toshinari
Published: July 2002

We observed the ac Josephson effect, the ‘‘Shapiro step,’’ at the high frequency of 584 GHz in an YBa2Cu3O7−δ grain boundary Josephson junction at 4.2 K for the first time. This Shapiro step grew to about 8% of the critical current without irradiation. We also noted that the critical current was gradually suppressed with increasing power. The critical current with irradiation was suppressed to about 97% of the critical current without irradiation. Detailed investigation revealed the consistency between the above two phenomena.
High conversion efficiency of second-harmonic generation in step quantum wells
Authors: Chen Zhenghao , Cui Dafu , Li Meihua , Jiang Chao , Zhou Junming , Yang Guozhen
Published: July 2002

Second-harmonic generation due to intersubband transitions in GaAs/AlxGa1−xAs step quantum well structures has been studied with a tunable TEA CO2 laser. The maximum value of χ(2)(2ω) is found to be ∼9×10−7 m/V. Using a multipass or ‘‘waveguide’’ structure, a conversion efficiency of more than 3×10−4 has been obtained.
Demonstration of the optical Kerr effect at 10.6 μm via intersubband nonlinearities in a multi-quantum well structure
Authors: Segev Mordechai , Gravé Ilan , Yariv Amnon
Published: July 2002

We demonstrate the optical Kerr effect at 10.6 μm in a GaAs/AlGaAs multi-quantum well doped structure. The effect is due to the nonlinear susceptibility χ(3) near a resonant intersubband transition.
Deposition and reduction of Nd1.85Ce0.15CuO4−y superconducting thin films
Authors: Mao S. N. , Xi X. X. , Bhattacharya S. , Li Qi , Venkatesan T. , Peng J. L. , Greene R. L. , Mao Jian , Wu Dong Ho , Anlage S. M.
Published: July 2002

Superconducting thin films of Nd1.85Ce0.15CuO4−y (NCCO) were grown at 720–820 °C by pulsed laser deposition in N2O atmosphere. The reduction subsequent to the deposition was found to be critical, and was studied systematically for various temperature, atmosphere, and duration. An ac susceptibility technique was used to stringently characterize the film quality. Very high quality films were made with optimized reduction conditions which showed a Tc(R=0) of 22.4 K, with a transition width of 0.2 K and a Jc (4.2 K) of 8×105/cm2 at zero field. Microwave surface resistance Rs was measured at 9.6 GHz and a value of ∼3 mΩ was obtained at 4.2 K in a 5000 Å thick NCCO film.
Frequency stability in ultrahigh frequency mode locking of quantum-well lasers at ≳60 GHz
Authors: Lau K. Y. , Kim I. , Paslaski J.
Published: July 2002

This letter presents experimental and theoretical results which show that megahertz frequency stability can be obtained in ultrahigh frequency mode-locked monolithic quantum-well lasers at ≳60 GHz. It is shown that the fundamental limit in the frequency stability is caused by simultaneous excitation of mode-locked ‘‘supermodes’’ by spontaneous emission.
Graded index linear and curved polymer channel waveguide arrays for massively parallel optical interconnects
Authors: Chen Ray T.
Published: July 2002

A single-mode polymer-based graded index channel waveguide array with 1250 channels/cm packaging density on a cross-link induced photopolymeric thin film is reported. This array works at 1.31 and 0.63 μm. Curved waveguides with radii of curvature from 1 to 40 mm were demonstrated. Waveguide propagation loss in the neighborhood of 0.1 db/cm was experimentally confirmed at 1.31 μm.
Chemical ordering in Zn1−xFexSe alloys
Authors: Park K. , Salamanca-Riba L. , Jonker B. T.
Published: July 2002

We have observed chemical ordering in Zn1−xFexSe (x≊0.5) epilayers as well as in nominal (ZnSe/FeSe) superlattices along the [001] growth direction and the [110] direction using transmission electron microscopy. The ordered structure consists of alternating ZnSe and FeSe layers along the [001] and [110] directions. In nominal (ZnSe/FeSe) superlattices grown on (001) GaAs substrates, strain-induced interdiffusion between the layers takes place followed by ordering of the resultant Zn1−xFexSe alloys. Computer simulated images for a Zn0.5Fe0.5Se compound were obtained and compared with experimental images. To our knowledge, this is the first observation of ordering in a II-VI alloy.
Optical bistability and nearly degenerate four-wave mixing in a GaAlAs laser under intermodal injection
Authors: Schanne P. , Heinrich H.-J. , Elsässer W. , Göbel E. O.
Published: July 2002

We demonstrate in a GaAlAs laser under intermodal optical injection, the existence of a domain, outside the injection-locking range, where the sidemode becomes the dominant lasing mode and gives rise to nearly degenerate four-wave-mixing processes. It is shown experimentally and by computer simulation that this domain is asymmetric with respect to the frequency detuning, and bistability of its borderline occurs, with a characteristic dependence on the injected light power.
Phase stability limits of Bi2Sr2Ca1Cu2O8+δ and Bi2Sr2Ca2Cu3O10+δ
Authors: Rubin L. M. , Orlando T. P. , Vander Sande J. B. , Gorman G. , Savoy R. , Swope R. , Beyers R.
Published: July 2002

We determined the phase stability limits of Bi2Sr2Ca1Cu2O8+δ and Bi2Sr2Ca2Cu3O10+δ in the temperature range 650–880 °C using a solid-state electrochemical technique. These phases decompose by incongruent melting above ∼790 °C, whereas they decompose by a solid-state reaction at lower temperatures. The solid-state decomposition reaction is reversible for Bi2Sr2Ca1Cu2O8+δ, but not for Bi2Sr2Ca2Cu3O10+δ.
Tunable wavelength conversion using a liquid crystal filter and a bistable laser diode
Authors: Tsuda Hiroyuki , Hirabayashi Katsuhiko , Iwamura Hidetoshi , Kurokawa Takashi
Published: July 2002

A tunable wavelength converter has been constructed using a liquid crystal Fabry–Perot interferometer and a multiple quantum well bistable laser diode. Input light pulses with a wavelength of 1495–1515 nm are converted to light pulses with a wavelength of 1485–1525 nm.
Comparison between theory and experiment for InGaAs/InP self-electro-optic effect devices
Authors: Mares P. J. , Chuang S. L.
Published: July 2002

Using the linewidth as the only fitted parameter, we present a detailed comparison between a theoretical model and a consistent set of experimental data for (i) the electronic properties, (ii) the optical properties, and (iii) the input power versus output power characteristics of In0.53Ga0.47As/InP self-electro-optic effect devices (SEEDs). The model includes excitonic effects, the dark current, and uses the depletion approximation to relate the applied bias to the electric field and to approximate the internal quantum efficiency. We show that the model is able to emulate and predict the behavior of quantum well modulators and SEEDs very well.
Double modulation-doped AlGaAs/InGaAs heterostructure with a graded composition in the quantum well
Authors: Yoo Tae-Kyung , Mandeville Pierre , Park Hyunchang , Schaff William J. , Eastman Lester F.
Published: July 2002

A new double modulation-doped AlGaAs/InGaAs heterostructure with a graded composition in the InGaAs quantum well (QW) has been designed and electrically characterized. An InGaAs QW with a rectangular-like potential profile in the presence of the two dimensional electron gas is obtained by a two-step grading of the In composition, which results in a broad and symmetric electron distribution profile even under various voltages. The Hall measurement shows a very high electron mobility of 7230 cm2/V s and an electron sheet density of 4.1×1012/cm2 at room temperature. To our knowledge, this is the highest mobility ever reported so far for the double modulation-doped Al0.3Ga0.7As/In0.2Ga0.8As field-effect transistor structure.
Optical nonlinearities in strained-layer InGaAs/GaAs multiple quantum wells
Authors: Jin R. , Okada K. , Khitrova G. , Gibbs H. M. , Pereira M. , Koch S. W. , Peyghambarian N.
Published: July 2002

Optical nonlinearities in strained-layer InGaAs/GaAs multiple quantum wells (MQWs) are studied using pump-probe spectroscopy. It is found that the carrier density required for absorption saturation in a strained InGaAs/GaAs MQW is about a factor of two lower than that in an unstrained GaAs/AlGaAs MQW with similar structures, while the nonlinear index change per carrier is about the same for both samples. The decrease in the saturation density in the strained MQW is explained by the increase of the top valence-band curvature caused by the compressive strain in the quantum well.
Native-oxide defined In0.5(AlxGa1−x)0.5P quantum well heterostructure window lasers (660 nm)
Authors: Maranowski S. A. , Kish F. A. , Caracci S. J. , Holonyak N. , Dallesasse J. M. , Bour D. P. , Treat D. W.
Published: July 2002

Data are presented demonstrating In0.5(AlxGa1−x)0.5P quantum well heterostructure lasers with extended current-blocking windows (∼75 μm/window) that exhibit significant improvements in output power (∼2×) compared to lasers with no windows. The windows and active stripes are defined by the formation of a thin (∼1000 Å, patterned) native oxide via H2O vapor oxidation (550 °C) of the high-gap In0.5(AlxGa1−x)0.5P upper confining layer. Devices operating at ∼660 nm with a 40 μm wide emitting aperture (∼500 μm cavity) and ∼75 μm windows (total window length ∼150 μm) exhibit 300 K continuous output powers ≳130 mW/facet (uncoated) and pulsed output powers ≳575 mW/facet (uncoated). Improvements in output power result from decreased heating at the facets and defocusing of the optical wave in the unpumped window regions.
Strained-layer InGaAs quantum well lasers emitting at 1.5 μm grown by chemical beam epitaxy
Authors: Sugiura Hideo , Noguchi Yoshio , Iga Ryuzo , Yamada Takeshi , Kamada Hidehiko , Sakai Yoshihisa , Yasaka Hiroshi
Published: July 2002

Laser characteristics of double channel planar buried heterostructure lasers with InxGa1−xAs/InGaAsP multiquantum wells (MQW) fabricated by a combination of chemical beam epitaxy and liquid phase epitaxy are described for the InAs content x of the InxGa1−xAs ranging from 0.53 to 0.71. There is no discernible difference in the minority carrier lifetime of the unstrained and strained MQWs. All the lasers have almost the same threshold current of 15±1 mA. Characteristic temperature T0 is improved in the strained lasers; the laser with x=0.62 has a T0 of as high as 98 K at 900 μm cavity length. Resonance oscillation frequency fr increases with the InAs content, i.e., the amount of the compressive strain.
Propagation loss of index imaged poly(cyclohexylsilyne) thin film optical waveguides
Authors: Hornak L. A. , Weidman T. W.
Published: July 2002

The propagation loss of optical waveguides index imaged in a 0.5 μm poly(cyclohexylsilyne) (PCHS) film through photo-oxidative cross linking with ultraviolet exposure at 310 nm is measured and compared to an experimental estimate of PCHS bulk propagation loss. Measured waveguide losses at 632.8 nm range from 0.6 dB/cm for TE operation of 2-μm-wide PCHS waveguides to 2.1 dB/cm for TM operated 4-μm-wide guides. Comparison to the bulk PCHS propagation loss estimate of 0.04 dB/cm at 632.8 nm indicates a significant increase in loss upon thin film waveguide fabrication.
Interface roughness in quantum wells prepared with growth interruptions
Authors: Orschel Benno , Oelgart Gerhard , Houdré Romuald
Published: July 2002

We use photoluminescence to examine GaAs/(AlGa)As single quantum wells of different thickness grown by molecular beam epitaxy with and without growth interruptions. We observed distinctive peaks arising from the heavy-hole exciton splitting associated with heterointerface growth ‘‘islands.’’ Comparison of the exciton peak energies with the predictions of the theory proposed by L. C. Andreani and A. Pasquarello [Phys. Rev. B 42, 8928 (1990)] (which was supported by independent experiments) yields a constant value of 0.85 monolayers for the apparent thickness fluctuations given rise to the different exciton peaks observed from each well. This behavior strongly supports the bimodal roughness model of the heterointerface in quantum wells prepared with growth interruptions as it was recently suggested by C. A. Warwick and R. F. Kopf [Appl. Phys. Lett. 60, 386 (1992)].
Calcium fluoride thin films on GaAs(100) for possible metal-insulator-semiconductor applicationsa)
Authors: Chaudhari G. N. , Rao V. J.
Published: July 2002

Calcium fluoride thin films were deposited onto low-temperature GaAs substrates by thermal evaporation followed by an in situ or ex situ annealing process. The influence of the deposition and annealing conditions on the structure and electronic properties of the films were investigated. It is shown that it was possible to obtain smooth epitaxial layers through in situ annealing. In addition, the substantial improvements in the electrical properties of the interfaces between GaAs and CaF2 have been obtained by in situ substrate annealing of CaF2 on GaAs(100) at 590 °C for 10 s which produced a dramatic reduction of capacitance frequency dispersion.
Minority electron mobility and lifetime in the p+GaAs base of AlGaAs/GaAs heterojunction bipolar transistors
Authors: Kim D. M. , Lee S. , Nathan M. I. , Gopinath A. , Williamson F. , Beyzavi K. , Ghiasi A.
Published: July 2002

AlGaAs/GaAs heterojunction bipolar transistors with different base doping concentrations grown by gas source molecular beam epitaxy were fabricated and characterized at dc and high frequency. Three different base doping concentrations; 5×1018, 1×1019, and 5×1019 cm−3 doped with Be were used for the characterization with the same structural and process parameters, including 0.2 μm base width. Minority electron mobilities in heavily doped p type were measured as 1.1×103, 1.3×103, and 3×103 cm2 V/s for 5×1018, 1×1019, and 5×1019 cm−3, respectively, by using the current gain cutoff frequency (fT) which agrees well with theoretical predictions in heavily doped p-type GaAs. Combining dc and high frequency measurements, electron lifetimes of 1.2×10−9, 5.5×10−10, and 2×10−11 s have been obtained for these three dopings, respectively.
Investigation of ballistic elastic scattering length and specularity in multiterminal GaAs/AlGaAs by magnetic electron focusing effect
Authors: Tsukagoshi K. , Takaoka S. , Murase K. , Gamo K. , Namba S.
Published: July 2002

Magnetic electron focusing effect has been investigated by paying attention to its electron density (ns) dependence in a GaAs/AlGaAs device with multiparallel terminal. With increasing ns, a ballistic elastic scattering length increases, but a specularity at boundary decreases. In a configuration in which the electrons could enter into the extra probe between injector and collector probes, still the focusing effect is clearly observed.
High-resolution transmission electron microscopy of vicinal AlAs/GaAs interfacial structure
Authors: Ikarashi Nobuyuki , Baba Toshio , Ishida Koichi
Published: July 2002

AlAs-on-GaAs vicinal interfaces grown by molecular beam epitaxy were investigated by high-resolution transmission electron microscopy in the 〈110〉 cross section, and the interfacial step structures were clearly observed. For the first time, distinctly different step interval distributions are found for interfaces tilted 2° from (001) towards (111)A and towards (111)B. Step bunching is observed for A steps, while a regular array of steps is observed for B steps. The edges of A steps are also straighter than those of B steps.
Formation of P precipitates during annealing of InP grown by gas source molecular beam epitaxy at low temperature
Authors: Claverie A. , Crestou J. , Garcia J. C.
Published: July 2002

We have studied by transmission electron microscopy the structural changes that take place in monocrystalline InP grown by gas source molecular beam epitaxy at low temperature upon annealing at about 600 °C. It is shown that the partial relaxation of the crystal which is observed by x rays is due to the formation of small precipitates (3–7 nm). Electron diffraction experiments show that the structure of these precipitates is cubic with a simple cube-to-cube orientation relationship with the substrate. Most probably, these precipitates are of alpha-white cubic P which is known to be insulating.
Growth of high quality gallium arsenide on HF-etched silicon (001) by chemical beam epitaxy
Authors: Xing Y. R. , Jamal Z. , Joyce T. B. , Bullough T. J. , Kiely C. J. , Goodhew P. J.
Published: July 2002

HF etching followed by relatively low temperature (≊600 °C) pretreatment is shown to provide a suitable substrate for the heteroepitaxial growth of GaAs on Si(100) by CBE using TEGa and AsH3 as sources. Rutherford backscattering (RBS), photoluminescence (PL), transmission electron microscopy (TEM), and Raman measurements show the low-defect nature of the GaAs epilayer.
Competitive kinetic processes during homoepitaxial growth on Ge(111)
Authors: Yokotsuka T. , Wilby M. R. , Vvedensky D. D. , Kawamura T. , Fukutani K. , Ino S.
Published: July 2002

The homoepitaxial growth of Ge(111) has been investigated with reflection high-energy electron diffraction (RHEED) measurements supported by Monte Carlo simulations. At low temperatures, the RHEED oscillations show a monolayer period, while at higher temperatures the oscillation period becomes bilayer. The simulations reveal that a short-range nonthermal diffusion process is dominant at low temperatures, and that the driving force behind the transition to bilayer growth is the increasing importance of thermal diffusion.
Photoluminescence of plasma polymerized methyl methacrylate films
Authors: Li Guifang , Tobin Jeffrey A. , Denton Denice D.
Published: July 2002

The photoluminescence properties of plasma polymerized methyl methacrylate films are investigated. The photoluminescence is a fluorescence rather than a phosphorescence process with a lifetime on the order of a few nanoseconds. The photoluminescence is a one-photon volume effect. The wavelength span of the photoluminescence using suitable UV excitation can reach over 300 nm with a FWHM exceeding 200 nm. These photoluminescent films may find potential applications in wavelength transformers for solar cells or as a gain medium for tunable solid-state dye lasers.
Morphology transformations of GaAs high-index surfaces during the initial stages of strained-layer overgrowth
Authors: Ilg Matthias , Nötzel Richard , Ploog Klaus H. , Hohenstein Matthias
Published: July 2002

We study the initial stage of InAs and Si growth on GaAs (311) and (211). In situ reflection high-energy electron diffraction shows the morphology of these surfaces to transform from corrugated to flat during deposition of fractional InAs and Si monolayers. This result is confirmed by high resolution electron microscopy investigations of an InAs monolayer embedded in (311) GaAs showing perfectly flat heterointerfaces. Our findings negate the existence of lateral patterning effects due to the surface corrugation in strained, GaAs-based heterostructures with high-index orientation, but they simultaneously demonstrate a novel method to manipulate interfaces in semiconductor heterostructures.
Observation of increased photoluminescence decay time in strain-induced quantum-well dots
Authors: Tan I-Hsing , Chang Ying-Lan , Mirin Richard , Hu Evelyn , Merz James , Yasuda Takashi , Segawa Yusaburo
Published: July 2002

We report on the observation of increased photoluminescence (PL) decay time in strain-induced quantum-well dots (SIQWDs), 120 nm in diameter. Lateral confinement was generated in a GaAs quantum well (QW) by etching a doubly exposed grating pattern into a pseudomorphic, strained layer of In0.35Ga0.65As which overlies the QWs. By spacing three QWs of different widths at varying depths from the In0.35Ga0.65As stressor, lateral strain confinement and vertical strain propagation are directly resolved by the PL spectra. The decay time of the heavy-hole-like excitons in the SIQWDs from the uppermost QW is 420 ps at 2 K, which is longer than the 270 ps PL decay time of the heavy-hole exciton in the reference QW sample.
Oxygen-related centers in chemical vapor deposition of diamond
Authors: Ruan J. , Choyke W. J. , Kobashi K.
Published: July 2002

Diamond films are grown using microwave-plasma-enhanced chemical vapor deposition (CVD). Some samples are deposited using 0.1% oxygen in the reaction gas mixture. We have measured the cathodoluminescence spectra of these diamond films (at 77 K) and found that there is a significant difference between the samples grown with oxygen and those without oxygen. Some of the impurity-related luminescence peaks are reduced in intensity or disappear when 0.1% oxygen is used. On the other hand, there are new spectral features in the films grown with oxygen. We attribute some of these new features to oxygen-related centers in diamond and conclude that oxygen could incorporate into the diamond lattice during the CVD process.
Sub-50 nm high aspect-ratio silicon pillars, ridges, and trenches fabricated using ultrahigh resolution electron beam lithography and reactive ion etching
Authors: Fischer P. B. , Chou S. Y.
Published: July 2002

We present the fabrication of sub-50 nm Si pillars, ridges, and trenches with aspect ratios greater than 10 using ultrahigh resolution electron beam lithography and chlorine based reactive ion etching. These nanoscale Si features can be further reduced to 10 nm using an additional HF wet etch. No photoluminescence was observed from arrays of 10 nm Si structures passivated with HF.
Design considerations for channel-doped back-gated high electron mobility structures
Authors: Owen P. M. , Pepper M.
Published: July 2002

We present the results of self-consistent calculations for the electronic subband structure of channel-doped, back-gated GaAs-AlGaAs heterostructures. The calculations identify the important design parameters for this system and illustrate the quantum effects occurring. We show that the doping density in the channel determines the mode of operation of the device and whether resonant effects are important. We discuss the design of velocity modulation transistors and structures with improved transconductance.
Low threshold 1.5 μm quantum well lasers with continuous linear-graded-index InGaAsP layers prepared by organometallic vapor-phase epitaxy
Authors: Lin Wei , Chang Chwan-Yang , Tu Yuan-Kuang , Dai Ting-Arn , Ho Wen-Jeng , Lee Gwo-Yue , Shi Tian-Tsorng , Shiao Hung-Pin
Published: July 2002

We report quantum well heterostructures with continuous linear-graded-index quaternary (CL-GRIN-QW) prepared by low-pressure organometallic vapor-phase epitaxy for the first time, by adopting the empirical flow-rate formulas. The linear compositional profile has been confirmed using secondary ion mass spectroscopy. Laser diodes incorporating the CL-GRIN-QW active layer structure exhibit threshold current density as low as 402 A/cm2 with a cavity length of 1500 μm and extrapolated threshold current density of infinite cavity length of about 176 A/cm2. These results demonstrate the benefits of the continuous linear-graded-index separate confinement layers for low threshold laser operation. Besides, the photoluminescence intensity of a continuous linear-graded-index strained-quantum well structure is found to be higher than that of an equivalent unstrained well design.
Optical properties of GaP/AlP short-period superlattices grown by gas source molecular beam epitaxy
Authors: Asami K. , Asahi H. , Watanabe T. , Enokida M. , Gonda S. , Fujita Sg.
Published: July 2002

Optical properties of (GaP)m/(AlP)n superlattices (SLs), with m+n=14, grown on GaP(001) by gas source molecular beam epitaxy have been studied by photoluminescence (PL), electroreflectance (ER), and optical reflectance. The dependence of the PL peak energies and the relative intensity on the monolayer number of AlP is in agreement with those theoretically predicted for the case of type II band alignment of GaP/AlP SLs. The refractive index of GaP/AlP SLs has been studied for the first time and compared with that of an AlGaP alloy. The refractive index calculated for an AlGaP alloy using a single-effective-oscillator model is consistent with the experimentally obtained results.
Time-lens producing 1.9 ps optical pulses
Authors: Godil A. A. , Auld B. A. , Bloom D. M.
Published: July 2002

A resonant microwave optical phase modulator in LiNbO3 with multiple passes, based on an off-axis path in a stable optical resonator, is demonstrated as a time-lens. With 1 W of cw microwave power at 5.2 GHz, 45 ps pulses at 1.06 μm were temporally focused to 6.7 ps (FWHM). Increasing the drive power to 13 W, at 10% duty cycle, produced 1.9 ps pulses. The aperture of the time-lens is about 31 ps. This is the first demonstration of a useful time-lens.
Transmission of phonons through grain boundaries in diamond films
Authors: Morelli D. T. , Uher C. , Robinson C. J.
Published: July 2002

The influence of grain boundary scattering of lattice waves in high quality diamond films has been determined by the measurement of thermal conductivity down to 0.15 K. We find that the mean free path for lattice vibrations (phonons) exceeds substantially the crystallite size and approaches the physical size of the sample. This implies that a significant transmission of phonons occurs between the grains of these polycrystalline diamond materials.
Catalytic effect of phosphine on the deposition of phosphosilicate glass from tetraethoxysilane
Authors: Tedder Laura L. , Crowell John E. , Uram Kevin J. , Shugrue John K. , Tribula D.
Published: July 2002

The effect of phosphorous incorporation on the deposition rate of phosphosilicate glass from the reaction of PH3, O2, and tetraethoxysilane (TEOS) has been studied. The previously reported apparent catalytic effect of PH3 on the deposition rate of SiO2 has been reproduced in this study, but by utilizing a newly designed hot-walled low-pressure chemical vapor deposition (LPCVD) reactor, homo- and heterogeneous catalytic effects were separated. These results indicate that the source of the catalytic effect is purely homogeneous, possibly involving an oxidation product of PH3 reacting with TEOS. Results obtained in a cold-wall reactor suggest that PH3 and O2 serve to poison the surface decomposition reaction of TEOS to produce SiO2.
Internal charge-phosphor field characteristics of alternating-current thin-film electroluminescent devices
Authors: Abu-Dayah A. , Kobayashi S. , Wager J. F.
Published: July 2002

The internal charge versus phosphor field (Q–Fp) technique is proposed as a method for characterization of the electrical properties of alternating-current thin-film electroluminescent (ACTFEL) devices. Q–Fp analysis provides direct information about the internal behavior of the ACTFEL device. The steady-state field and internal conduction, polarization, leakage, and relaxation charges may be readily deduced from a Q–Fp plot.
Intermittent ultraviolet irradiation for silicon selective epitaxial growth
Authors: Miyata N. , Yamazaki T. , Arimoto Y. , Ito T.
Published: July 2002

We present a cyclic process of Si growth followed by ultraviolet (UV) irradiation which suppresses Si nucleation on the SiO2 surface. We grew Si using low pressure chemical vapor deposition with a Si2H6/H2 gas system without chlorine at 700 and 650 °C. Incubation period is determined using Auger electron spectroscopy as the time for which there is less than 0.015 coverage of Si on SiO2. We show that intermittent UV irradiation within the incubation period suppresses Si nucleation on the SiO2 surface. We believe the growth/UV-irradiation cyclic process is useful for preparing a thick Si selective epitaxial growth layer.
Proximity effect reduction using thin insulating layers
Authors: Rhee Kee Woo , Peckerar Martin C.
Published: July 2002

In this letter, we demonstrate a novel method for reducing or eliminating e-beam proximity effect in patterning tungsten for use as an x-ray mask absorber material. The method involves interposting a thin (200 nm) layer of low atomic weight insulating material (such as SiO2) between the resist and the underlying substrate. Examples are shown in which gratings of 0.2 μm lines with a 0.5 μm period were written without dose correction for proximity effect compensation.
11.6 W peak power, diffraction-limited diode-to-diode optical amplifier
Authors: Mehuys David , Welch David F. , Goldberg Lew , Weller Joseph
Published: July 2002

A 600-μm-wide by 2200-μm-long broad area single-pass semiconductor amplifier is demonstrated to emit up to 11.6 W of peak power in a nearly diffraction-limited far field pattern when injected with 100 mW from a single-mode laser diode. The amplifier slope efficiency of 0.60 W/A is identical to that obtained using a 100 mW Ti:sapphire master oscillator, and only slightly lower than the slope efficiency of 0.75 W/A measured under fully saturated conditions with 400 mW of Ti:sapphire incident power.
Integrated-optical switch arrays in GaAs based on electrically controlled dynamic free carrier gratings
Authors: Aronson Lewis B. , Hesselink Lambertus
Published: July 2002

A new high density integrated-optical switch design using electrically controlled diffraction gratings formed in the intersection of crossing waveguides is proposed and demonstrated. The gratings are formed, in one implementation, by implanting donor atoms in a periodic pattern. Free carriers from the implanted ions modify the index of refraction resulting in Bragg diffraction between the waveguides. Depletion of the free carriers using a reverse bias voltage switches off the diffraction. High speed switch arrays of 100×100 elements on a single substrate may be feasible. Fabrication and demonstration of a low efficiency proof-of-concept switch array in GaAs for use at 1.55 μm are reported. Other designs capable of much higher diffraction efficiencies are described.
Transmission electron microscopy study of chemically etched porous Si
Authors: Shih S. , Jung K. H. , Qian R.-Z. , Kwong D. L.
Published: July 2002

We have developed a new, minimal damage approach for examination of luminescent porous Si (PS) layers by transmission electron microscopy (TEM). In this approach, chemically etched (CE) PS layers are fabricated after conventional plan-view TEM sample preparation. Our TEM studies show that crystalline, polycrystalline, and amorphous phases exist in the same CE sample. The microstructure is believed to gradually change from crystalline to amorphous during chemical etching in a HF-HNO3-H2O solution. The microcrystallites in the polycrystalline region are estimated to be 15–100 Å, while the pore size is on the order of 400 Å.
keV ion sputtering of hydroxyapatite
Authors: Torrisi L. , Foti G.
Published: July 2002

Thin films of hydroxyapatite have been deposited by 5 keV ion sputtering on titanium substrates at room temperature. The sputtering yield is about 5×10−2 molecules/ion for argon beam and shows a linear trend with the ion nuclear stopping power of incoming beams. Noble gases have been adopted to avoid chemical reaction between implanted ions and hydroxyapatite target. Auger electron spectroscopy has been used in a high vacuum chamber to measure in situ the stoichiometry of the deposited film.
Excimer pumped deuterated L-arginine phosphate optical parametric oscillator
Authors: Robertson Gordon , Dunn Malcolm H.
Published: July 2002

The first optical parametric oscillator (OPO) using deuterated L-arginine phosphate is reported herein. The OPO pumped at 308 nm by an XeCl excimer laser generates broadly tunable output over the spectral ranges 415 to 526 nm and 1194 to 743 nm, using a critically phase-matched type I geometry. A study of the oscillation threshold has been made under conditions of different beam sizes and across the tuning range. A discussion of the damage problem in the material and the implications of 351 nm pumping are also given.
Effects of mixing germane in silane gas-source molecular beam epitaxy
Authors: Kim Ki-Joon , Suemitsu Maki , Yamanaka Masayoshi , Miyamoto Nobuo
Published: July 2002

Growth of SiGe gas-source molecular beam epitaxy (GSMBE) using silane/germane mixture has been investigated for the germane content of 0%, 0.8%, and 2.6%. From detailed measurements on the growth rate, a separation into high- and low-temperature regions of the growth rate, as in silane-GSMBE system, has been found to exist in this silane/germane system. A simultaneous measurement on the surface hydrogen coverage has revealed that the growth in the low-temperature region is rate limited by the surface hydrogen desorption process, reasoning the enhanced growth rate with germane in terms of the reduced coverage of the surface hydrogen. All the growth rates followed a same fourth power dependence on the free-adsorption site, which suggests a validity of the four-site adsorption model, established for silane-GSMBE, in silane/germane GSMBE.
Nonpolymer new organic film for local insulation in laser-direct-writing circuit restructuring for large-scale integrated circuits
Authors: Seki Y. , Morishige Y. , Wamme N. , Ohnishi Y. , Kishida S.
Published: July 2002

A new nonpolymer organic material, hexaacetate p-methylcalix [6] arene (hereafter referred to as MC6AOAc), has been successfully applied to the localized insulator for large-scale integration (LSI) circuit restructuring. A conductive line, necessary for the restructuring, was written on the MC6AOAc film by laser chemical vapor deposition with no damage to the film. The leakage current through the film was kept within the permissible limit. The unnecessary part of the film for LSI testing was easily removed by an ethanol rinse without damage to the interconnection, in a self-aligned manner, with the written line as a mask. This technology extends the usability of the LSI circuit restructuring.
2.51 eV photoluminescence from Zn-doped CuAlSe2 epilayers grown by low-pressure metalorganic chemical vapor deposition
Authors: Chichibu S. , Matsumoto S. , Shirakata S. , Isomura S. , Higuchi H.
Published: July 2002

A photoluminescence (PL) peak at 2.51 eV was observed at 77 K in Zn-doped CuAlSe2 chalcopyrite semiconductor epilayers grown by a low-pressure metalorganic chemical vapor deposition. The emission can be seen as blue-green. The PL peak at 2.51 eV was absent in Al-rich epilayers. Photoreflectance measurements were performed on both undoped and Zn-doped CuAlSe2 epilayers. Zn doping up to the level of 0.02 at. % did not affect the valence band profile.
Ba1−xKxBiO3 thin film Josephson tunnel junctions
Authors: Fink R. L. , Hilbert Claude , Kroger Harry
Published: July 2002

We have fabricated sandwich-type Josephson tunnel junction devices from Ba1−xKxBiO3 electrodes and KNbO3 insulating barriers. Near ideal superconductor-insulator-superconductor tunnel junction gap structure was seen in high resistance devices at 4.2 K. Lower resistance devices with similar gap structure but much higher subgap leakage were hysteretic with switching voltages up to 5 mV. Hysteresis and well-defined gap structure persisted past 12 K. Magnetic field modulation of the zero-bias pair current showed Fraunhofer-like behavior with almost complete quenching at the nodes.
Infrared spectroscopic study of the chemisorption of CF3 species on silicon
Authors: Bermudez V. M.
Published: July 2002

Infrared reflection absorption spectroscopy, in conjunction with Auger electron spectroscopy, is used to study the initial adsorption of CF3 species (mainly CF3+ ions) on polycrystalline Si in a model etching environment. Only monofluorosilyl groups (SiF) are observed, with no indication of adsorbed SiF2, SiF3, or CFx(1≤x≤3). The SiF exists in one of two chemically distinct environments, depending on the coverage of coadsorbed carbon.
Second-order nonlinear optical properties of an aromatic polyurea exhibiting optical transparency down to 300 nm
Authors: Nalwa Hari Singh , Watanabe Toshiyuki , Kakuta Atsushi , Mukoh Akio , Miyata Seizo
Published: July 2002

We report here a new high performance organic polymer comprised of urea moieties for optical second-harmonic generation. The nonlinear d33 coefficient of aromatic polyurea consisting of nonlinear optical chromophores in the main chain, estimated by Maker fringe measurements was found to be approximately 15 times that of KDP crystals at 1.064 μm. The decay of second-order optical nonlinearity of poled polyurea films at ambient conditions was negligible and temporal study showed persistent optical nonlinearity at least 1000 h after poling. Aromatic polyurea films exhibited optical transparency down to ∼300 nm in UV region and optical transmission was greater than 99% from 350–2500 nm like conventional inorganic nonlinear optical materials. Aromatic polyurea is the first example of an organic nonlinear optical material showing optical transparency at such low wavelengths. The nonlinear efficiency transparency trade-off demonstrates aromatic polyurea to be a new promising organic material for nonlinear optics.
Dynamics of resonant optical waveguide semiconductor laser arrays
Authors: Ramanujan Sujatha , Winful Herbert G.
Published: July 2002

A propagation model is presented for the dynamics of antiguided semiconductor laser arrays. The model takes into account diffraction, carrier diffusion, spatial hole burning, and carrier-induced antiguiding. Numerical results reveal a variety of spatiotemporal behaviors ranging from stable, quiescent operation to periodic and erratic intensity oscillations.
Intrinsic multiplexability of surface bistable nematic displays
Authors: Barberi R. , Giocondo M. , Lagarde Ph. Martinot , Durand G.
Published: July 2002

We present a simple multiplexing procedure for the flexoelectrically controlled surface bistable nematic display. When the surface anchoring is broken, the surface bifurcation between the two stable surface orientations has a very large sensitivity to external fields. This intrinsic property allows an easy multiplexing of the display. We excite each pixel with a sequence of two signals: a large driving square pulse of arbitrary polarity (or at high frequency), which breaks the surface anchoring, and a weak control square pulse, whose polarity determines the final texture of the pixel and hence its optical state. In a matrix geometry, the rows are sequentially addressed with the driving pulse. The columns are excited in parallel with the control pulse to write or erase the corresponding pixel.
Pump-probe charge integrating technique: A study of trap emission kinetics in silicon dioxide
Authors: Poler J. C. , Irene E. A.
Published: July 2002

A new method for the study of charge emission from electrically active traps is described. This technique uses a sequence of electrostatic pulses in a pump-probe sequencing scheme, to examine the detrapping kinetics of states in the Si/SiO2 metal oxide semiconductor system. We show that with the pump-probe technique, the initial time regime of the trap emission dynamics is accessed. The results observed on oxidized lightly doped p-Si(111) substrates show trap interaction at high injection bias, and detrapping kinetics are discussed in the context of an occupation dependent trap interaction model.
Microcavity enhanced vertical-cavity light-emitting diodes
Authors: Keller U. , Jacobovitz-Veselka G. R. , Cunningham J. E. , Jan W. Y. , Tell B. , Brown-Goebeler K. F. , Livescu G.
Published: July 2002

We systematically studied microcavity enhancement and mode-coupling effects in photo- and electroluminescence of an AlGaAs/GaAs vertical-cavity light-emitting diode (LED) by continuously changing the microcavity resonance with respect to the quantum well band gap. At mode overlap we obtained maximum photo- and electroluminescence intensities and a minimum emitted linewidth of 4.6 nm at 836 nm with a FWHM divergence of 62°. However, the electrical-to-optical efficiency was less than 1 μW/mA. Application issues for optical interconnects are presented.
Enhancement of photoluminescence quantum efficiency in semiconductor structures with reduced dimensionality
Authors: Efros Al. L. , Prigodin V. N.
Published: July 2002

We have investigated photoluminescence quantum efficiency (QE) in disordered semiconductor systems. The value of QE is shown to depend strongly on the ratio of the temperature to the energy spread of localized electron states. We found that the high recombination rate of nonradiative centers (killers) could be reduced by the low mobility of carriers. The consequence is an enhancement of QE which is ever more remarkable in 1d semiconductor structures. This result can be used as an explanation for the high QE of porous Si, which is represented as an example of a disordered quasi-one-dimensional structure.
Thermal processing of a copper-poly(phenyl quinoxaline) interface: Diffusion of the metal in the polymer studied by high resolution electron-energy-loss spectroscopy
Authors: Fontaine M. , Layet J. M. , Grégoire Ch. , Pireaux J. J. , Cros A.
Published: July 2002

Thin layers of metallic copper (up to a few hundreds angström) were deposited onto poly(phenyl quinoxaline) (PPQ), a new thermostable polymer. As suggested by x-ray photoelectron spectroscopy (XPS) and ascertained by a new type of application of high resolution electron-energy-loss spectroscopy, further processing of the interface by thermal anneal (300 °C) induces diffusion of Cu species into the bulk of the polymer. By studying the electronic transitions of the Cu-PPQ system, we show that it is possible to get a significant understanding of the copper diffusion into the polymer. The combination of the spectroscopic surface sensitive methods allows us to propose a morphological description of the Cu-PPQ interface before and after anneal.
Activation energy for the C49-to-C54 phase transition of polycrystalline TiSi2 films with arsenic impurities
Authors: Matsubara Y. , Horiuchi T. , Okumura K.
Published: July 2002

The C49-to-C54 transition in TiSi2 was investigated using samples having submicron line width film, by an x-ray diffraction technique. Arrhenius plots of the transition rate show that the C49-to-C54 transition of polycrystalline TiSi2 films with arsenic impurities have an activation energy barrier strongly dependent on the arsenic concentration. The energy increases as a function of arsenic impurity concentration, from 3.5 eV for TiSi2 formed on Si substrate ion implanted with the dose of 2×1015 cm−2, to 7.8 eV with the dose of 5×1015 cm−2. The annealing time dependence of the x-ray intensity on (004) orientation indicates that TiSi2 formed on Si substrate with the arsenic dose of 2×1015 cm−2 shows a diffusion-limited process and that with the dose of 5×1015 cm−2 shows an interface-limited process. The arsenic precipitates act to pin the C49 phase in the C49-to-C54 transition.