bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonplanar quantum well heterostructure window laser
Authors: Bryan R. P. , Miller L. M. , Cockerill T. M. , Coleman J. J.
Published: July 2002

Data are presented on a nonplanar graded barrier quantum well heterostructure window laser formed by a single metalorganic chemical vapor deposition (MOCVD) growth. By utilizing a selectively etched substrate, a transparent window region is formed in the vicinity of the facets thereby relaxing the maximum power limit imposed by catastrophic optical degradation. The ultimate output power available from such devices is approximately 50% higher than from devices with the same structure but grown on unetched substrates. The processing required for device fabrication is minimized by taking advantage of the properties of MOCVD growth on nonplanar substrates.
Restricted aperture acoustic microscope lens for Rayleigh wave imaging
Authors: Davids D. A. , Wu P. Y. , Chizhik D.
Published: July 2002

The performance of an acoustic microscope lens is reported that permits both Rayleigh wave velocity measurement of anisotropic media as well as raster-scanned imaging. The lens surface is spherical and uses a circular p-wave transducer; however, an acoustic absorbing layer is applied to the spherical surface in order to limit the angular range over which Rayleigh waves are launched. When operated at 50 MHz, a lens having a slot-like aperture of 0.8 mm width permits measurement of VR (θ) of y-cut quartz with a maximum error of less than 2%. The same system employed in imaging provides spatial resolution of about one wavelength in a direction parallel to the axis of the slot and between two and three wavelengths in the perpendicular direction.
Electro-optic sideband generation at 72 GHz
Authors: Kallenbach R. , Scheumann B. , Zimmermann C. , Meschede D. , Hänsch T. W.
Published: July 2002

Sidebands are observed at 72 GHz off an optical carrier at 633 nm. The laser beam is phase modulated in a LiNbO3 crystal which is exposed to a mm-wave field inside a Fabry–Perot resonator. Under optimum phase-matching conditions we obtain a modulation index of 5% derived from 200 mW microwave power. Phase matching is obtained by guiding the light beam on a zig-zag path under internal total reflections. For this unconventional type of phase matching, the optical wave fronts travel at twice the speed of the modulating wave along the resonator axis.
Photoluminescence from carriers confined at a GaxIn1−xAs-InP single heterojunction interface
Authors: Yu P. W. , Peng C. K. , Morkoç H.
Published: July 2002

The low-temperature properties of the interface photoluminescence emission in GaxIn1−xAs-InP single heterojunctions grown by molecular beam epitaxy are investigated with changes of temperature and excitation intensity at different depths across the interface. The emission energy shifts to higher energy with increasing excitation intensity and lies between the three-dimensional GaxIn1−xAs-InP near-band-edge exciton and the quasi-donor–acceptor pair transition. The new emission is attributed to the interface exciton which is indirect in real space.
Hg1−xCdxTe/Hg1−xZnxTe superlattices with constant Hg content
Authors: Feldman R. D. , Fuoss P. H. , Austin R. F. , Kahn J. L. , Norton L. J. , Brennan S.
Published: July 2002

Hg1−xCdxTe/Hg1−xZnxTe superlattices with constant Hg content have been grown by molecular beam epitaxy for x between 0.22 and 0.4. Films grown at 180 °C show x-ray satellite peaks to the fourteenth order. An annealing study conducted between 185 and 225 °C shows enhanced stability compared to HgTe/CdTe superlattices.
Saturation of the nonlinear refractive-index change in a semiconductor-doped glass channel waveguide
Authors: Banyai W. C. , Finlayson N. , Seaton C. T. , Stegeman G. I. , O’Neill M. , Cullen T. J. , Ironside C. N.
Published: July 2002

The saturated nonlinear refractive-index change in a CdSxSe1−x semiconductor-doped glass channel waveguide was measured with a picosecond pump-probe Mach–Zehnder interferometer at photon energies below the band gap. The pump-probe configuration permitted the resolution of competing thermal and electronic nonlinearities. The significance of the results for all-optical switching is discussed.
Wavelength and threshold current of a quantum well laser in a strong magnetic field
Authors: Berendschot T. T. J. M. , Reinen H. A. J. M. , Bluyssen H. J. A. , Harder C. , Meier H. P.
Published: July 2002

The threshold current and the wavelength of a high-power ridge waveguide AlGaAs graded index seperate confinement heterostructure quantum well laser have been studied in strong magnetic fields up to 20 T, to simulate the complete quantum confinement of carriers in a quantum box laser. It will be shown both experimentally and theoretically that the threshold current is increased by the application of a strong magnetic field, while its temperature sensitivity is reduced. It will further be shown that at low temperatures (T<100 K) laser emission occurs via both free carrier and excitonic transitions, while at higher temperatures (T>100 K) exciton laser emission is only observed after application of a strong magnetic field, i.e., reduction of the dimensionality.
Enhancing T
c in Bi2.1CaSr2Cu2O8+δ from 90 to 101 K by yttrium substitution
Authors: Tallon J. L. , Buckley R. G. , Staines M. P. , Presland M. R. , Gilberd P. W.
Published: July 2002

The Y and rare-earth substitution for Ca in Bi2.1CaSr2Cu2O8+δ is described with particular emphasis on Y substitution. We have prepared single phase, fully substituted material which exhibits an 8.0×b-axis incommensurate structure, rather larger than the 4.75× structure in the parent superconductor. The infrared absorption spectra of the insulating fully substituted material are shown to have features very similar to that for YBa2Cu3O7−δ. A solubility range is observed only at substitutions up to 5% at which point zero-resistance Tc is raised from 90 to 101 K. This is shown to arise from 2 copper-layer material and not from 3 copper-layer material. Combined Y and Pb substitution yields n=2 material for which Tc remains fixed at 90 K, insensitive to annealing temperature and oxygen loading.
Confined phonons in (GaAs)n1(AlAs)n2 superlattices grown along the [012] direction
Authors: Popović Z. V. , Cardona M. , Tapfer L. , Ploog K. , Richter E. , Strauch D.
Published: July 2002

The short-period (GaAs)n1(AlAs)n2 superlattices with parameters (n1,n2)=(21,25), (6,42), (14,16), and (23,8) have been grown by molecular beam epitaxy on GaAs substrates along the [012] direction and characterized by x-ray and Raman scattering spectroscopy. The appearance of distinct satellite peaks around the Bragg reflections demonstrates the formation of high quality superlattices. The observed TO and LO confined modes have frequencies which map closely those of the optical phonons of bulk GaAs and AlAs in the Γ-W-X direction.
Electrical properties of hydrogenated amorphous silicon layers on a polymer film substrate under tensile stress
Authors: Nakatani K. , Ogasawara M. , Suzuki K. , Okaniwa H. , Hamamoto K. , Ozaki H.
Published: July 2002

The electrical properties of hydrogenated amorphous silicon (a-Si:H) layers on a polyethylene terephthalate (PET) film were studied under tensile stress. As the a-Si:H layers were stretched about 1.5%, dark conductivity and photoconductivity decreased gradually at first and then steeply beyond a critical strain. It was found that the former behavior was caused by a piezoresistance effect and the latter was attributed to breaking weak SiSi bonds, as shown by an increase of the electron spin resonance (ESR) intensity of Si dangling bonds. These changes of conductivity and ESR signal intensity were almost completely restored by annealing the a-Si:H layer at 150 °C for 1 h while relaxed.
Rutherford backscattering spectroscopy and electron microprobe analyses of argon gas trapped in alumina thin films
Authors: Gignac Lynne M. , Risbud Subhash H.
Published: July 2002

rf-sputtered aluminum oxide thin films were analyzed for argon content using electron microprobe analysis (EMPA). Standardless Rutherford backscattering spectroscopy was performed on several Al2O3 films, and these data were used as calibration standards in EMPA. EMPA performed at 10 keV with two separate film standards gave reproducible trends; the estimated error in the EMPA argon analysis was calculated to be ±0.8 wt. % at 10 keV and ±1.4 wt. % at 5 keV.
Longitudinal electron drift mobility of hydrogenated amorphous silicon/silicon nitride multilayer structures revealed by time-of-flight measurements
Authors: Hattori R. , Shirafuji J.
Published: July 2002

Electron drift mobility longitudinal to hydrogenated amorphous silicon/silicon nitride multilayer structures has been measured by the time-of-flight method. Transient photocurrent shows a clear kink corresponding to the transit time. The room-temperature electron mobility in multilayer structures is smaller by three or four orders of magnitude than that observed in bulk a-Si:H. The room-temperature electron mobility decreases with decreasing well layer width at constant layer thickness of 13 Å, while the activation energy of the mobility increases. The lifetime of electrons tends to increase when the well layer thickness is reduced.
CuInSe2 films and solar cells obtained by selenization of evaporated Cu-In layers
Authors: Basol Bulent M. , Kapur Vijay K.
Published: July 2002

CuInSe2 films of various stoichiometries have been prepared by the two-stage process. In this method, Cu-In layers were first evaporated onto Mo-coated glass substrates in the form of stacks, and then they were selenized in a H2Se atmosphere at 400 °C to form the compound. CdZnS/CuInSe2 heterojunction solar cells were fabricated on these films and conversion efficiencies close to 7% were obtained.
Comment on ‘‘Small field behavior of critical current in Y1Ba2Cu3O7 sintered samples’’
Authors: Fang P. H.
Published: July 2002

This comment points out that the claimed agreement between the theory exp− eriment for an array of Josephson junctions in Y1Ba2Cu3O7 is erroneous. A phenomenological modification of the formula for the critical current is presented. (AIP)
Characterization of γ-Fe2O3 homogeneity in magnetic recording media by photoacoustics
Authors: Peralta S. B. , Williams A. W.
Published: July 2002

The degree of homogeneity of ferric oxide in magnetic tapes has been characterized using photoacoustic techniques. The method is based on excitation of the sample by a modulated laser beam and subsequent detection of its acoustic response via a condenser microphone. The acoustic response is dependent on the local thermal variations in the sample, and is a direct measurement of the distribution uniformity of the particulate metal oxide in the sample. Results of this study provide a potential means for the rapid evaluation of the quality of magnetic recording media.
Bulk superconductivity with T
c (zero) up to 95 K in a Tl0.5Pb0.5Ca0.9Ce0.1Sr2Cu2 oxide with an Y1Ba2Cu3Oy-like structure
Authors: Wu P. T. , Liu R. S. , Liang J. M. , Huang Y. T. , Wu S. F. , Chen L. J.
Published: July 2002

Bulk superconductivity with Tc (zero) up to 95 K in a Tl0.5Pb0.5Ca0.9Ce0.1Sr2Cu2 oxide with an Y1Ba2Cu3Oy -like structure was observed. Single-phase samples, tetragonal in structure with a=0.380±0.001, c=1.195±0.001 nm, and of P4/mmm space group, were prepared. The results represent the first case where Ce substitution significantly raised the Tc of a known compound. The samples were remarkably homogeneous both in composition and structure. The compounds were highly reproducible and stable. The preparative conditions were found to be much less stringent than those of other copper-based high Tc superconductors.
Y-Ba-Cu-O thin films prepared by flash evaporation
Authors: Ece M. , Vook R. W.
Published: July 2002

Oriented-Y-Ba-Cu-O thin films with thicknesses between 0.6 and 0.7 μm have been deposited on magnesium oxide substrates by the flash evaporation method. The deposition was made by dropping powders of sintered Y1 Ba2 Cu3 O7−x onto a resistively heated tungsten boat. The as-deposited films were then annealed at 930 °C in oxygen for 60 min. Annealed films were superconductors above 77 K and x-ray diffraction showed a preferred c-axis orientation. Increasing the annealing temperature to 945 °C improved the texture of the films and the transition temperature of the superconductivity.
Effects of sputtered particle energy on the properties of SiO2 films
Authors: Ohwaki Takeshi , Taga Yasunori
Published: July 2002

Secondary ion-energy distributions (SIEDs) emitted from Si under various conditions of targets (Si, SiO2) and primary ions (Ar+, O+) were measured and thin SiO2 films were deposited by magnetron sputtering techniques under the corresponding conditions to the SIED experiments. The most probable energies of silicon oxygen cluster ions of SimO+n (m, n=1, 2,...) are equal to those of Al+ thermal ions, while those of Si+l (l=1, 2,...) remain unchanged with the introduction of oxygen in chamber during Ar+ ion bombardment. The current-voltage plots of SiO2 films are also measured and found to be influenced by the deposition conditions. It is concluded that the differences in current-voltage characteristics of SiO2 films prepared under various sputtering conditions can be reasonably explained in terms of the changes in the most probable energy of the sputtered particles.
Effect of water vapor on a CH4-H2 discharge plasma
Authors: Lockwood R. B. , Miers R. E. , Anderson L. W. , Lawler J. E. , Lin Chun C.
Published: July 2002

The effects on a CH4 -H2 discharge plasma due to the addition of water vapor to the feed gas have been studied. Surprisingly it is found that the concentrations of most positive and negative hydrocarbon ions in the discharge are substantially increased. Possible mechanisms for the increase are presented.
Effects of Fe on the superconductivity of 110 K phase superconductor Bi-Pb-Sr-Ca-Cu-O
Authors: Sun Yuping , Jiang Jianyi , Zheng Fanchun , Yin Huaqing , Du Jiaju
Published: July 2002

We have investigated the effects of Fe on the structure and properties of 110 K phase superconductor Bi-Pb-Sr-Ca-Cu-O. The zero resistance temperature decreases and the x-ray diffraction intensity ratio of (200) to (001_4_) peak increases, with the increasing of the Fe atom concentration. These samples are of single (2223) phase structure. It may be suggested that a 95 K superconducting phase exists. Its structure is very similar to that of the Bi2Sr2Ca2Cu3Oy phase. The Fe atoms make the 110 K phase turn into the 95 K phase.
Chirping of electroabsorption modulation in InGaAsP
Authors: Lin S. C. , Yu P. K. L. , Chang W. S. C.
Published: July 2002

Oscillatory behaviors in the electroabsorption (EA) spectra around the fundamental edge of InGaAsP are measured for the first time. Chirping of EA modulation is obtained from these EA spectra and the corresponding electrorefraction spectra calculated from the Kramers–Kronig transform. This result is applied to the selection of material band gap for applications of laser light modulation.
Light modulation by transverse electric field induced oil surface deformation
Authors: Hoshino Yasushi , Shiwa Shinichi
Published: July 2002

Oil surface deformation on stripe electrodes by applying an electric field between neighboring electrodes is described. A laser beam can be diffracted by the deformed oil distribution on alternate electrodes. When the electrode width is 10 μm, the response times for voltage on and off are 4 and 1 ms, respectively, and light scattering efficiency is more than 90%.
NbN/MgO/NbN edge-geometry tunnel junctions
Authors: Hunt B. D. , LeDuc H. G. , Cypher S. R. , Stern J. A. , Judas A.
Published: July 2002

We report the fabrication and low-frequency testing of the first edge-geometry NbN/MgO/NbN superconducting tunnel junctions. The use of an edge geometry allows very small junction areas to be obtained, while the all-NbN electrodes permit operation at 8–10 K with a potential maximum operating frequency above 1 THz. Edge definition in the base NbN film was accomplished utilizing Ar ion milling with an Al2O3 milling mask, followed by a lower energy ion cleaning step. This process has produced all-refractory-material tunnel junctions with areas as small as 0.1 μm2, resistance-area products less than 21 Ω μm2, and subgap to normal state resistance ratios larger than 18.
Study of hydrogenation in GaSb/AlSb multiple quantum well structures by time-resolved luminescence
Authors: Capizzi M. , Coluzza C. , Frova A. , Cebulla U. , Forchel A.
Published: July 2002

Continuous and pulsed photoluminescence experiments in GaSb/AlSb multiple quantum wells have been performed before and after exposure to hydrogen. An appreciable increase in the emission efficiency has been observed for H ion doses as low as 1013/cm2. Since the results cannot be accounted for in terms of the plain passivation of nonradiative centers, the effect is ascribed mostly to a change in the mechanism of carrier relaxation within the lower end of the bound-state distribution.
Selective metallization of n-type GaAs formed by projection-patterned excimer laser doping of Si
Authors: Sugioka K. , Toyoda K. , Gomi Y. , Tanaka S.
Published: July 2002

Resistless microfabrication of the metallization of n-type GaAs formed by projection-patterned doping using a KrF excimer laser is described. Silane (SiH4 ) gas is used as a source material of the n-type dopant of Si. Copper thin films with a linewidth as narrow as 3.4 μm are deposited selectively on the doped region by electroplating using a CuSO4 aqueous solution. Using the selective metallization process, nonalloyed ohmic contacts can be formed with a specific contact resistance of 2.32×10−5 Ω cm2, which is one-thirtieth of that of the conventional alloyed contacts.
Theoretically predicted influence of donors and acceptors on quadratic hyperpolarizabilities in conjugated long-chain molecules
Authors: Yoshimura Tetsuzo
Published: July 2002

The influence of the substitution positions of donors and acceptors on quadratic hyperpolarizabilities (β) was simulated by the AM1 method using four types of conjugated long-chain molecules having polydiacetylene structures. The chain-length dependences of β are greatly affected by the molecular type. The molecule, in which donor-donor pairs and acceptor-acceptor pairs alternately appear in the chain, has a narrow energy gap of about 1.6 eV and an exceptionally large β per 10 Å chain length, about 110 times larger than β of 2-methyl-4-nitroaniline.
One-way image transmission through a distorting medium using two holograms
Authors: Lee Hee S. , Fenichel Henry
Published: July 2002

A method is described for transmission of images through a distorter. The technique uses the principle of phase conjugation and employs two holograms. The conjugate of one of the reference beams acts as a carrier for the signal through the distorting medium.
Photoemissive scanning microscopy of doped regions on semiconductor surfaces
Authors: Quiniou B. , Scarmozzino R. , Wu Z. , Osgood R. M.
Published: July 2002

Photoelectric emission induced by a focused UV laser beam (λ=257 nm) has been used to probe semiconductor surfaces. It was possible to distinguish between regions of different doping levels on a silicon surface. The spatial resolution was found to be limited only by the laser beam spot size.
Growth temperature dependent radiative relaxation in AlGaAs/GaAs multiple quantum wells
Authors: Matsueda Hideaki , Hara Kiyoaki
Published: July 2002

Decay times of photoexcited electrons in AlGaAs/GaAs multiple quantum wells are evaluated using a time-correlated photon counting method. The decay time was observed to increase with crystal growth temperature between 600 and 730 °C for metalorganic chemical vapor deposition. It also increased with the photoluminescence sample temperature, in agreement with theoretical considerations based on Fermi’s golden rule.
Multimegabar pressures using synthetic diamond anvils
Authors: Ruoff Arthur L. , Vohra Yogesh K.
Published: July 2002

Synthetic type 1B yellow diamonds containing nitrogen in single substitutional form, with extremely low birefringence, were used as anvils in a diamond anvil cell. The diamonds were well characterized by infrared and visible absorption spectra. Sensitive spectroscopic methods along with mechanical chopping techniques were used to record ruby fluorescence to 250–300 GPa, a pressure equal to or exceeding that attained with natural diamonds. Nitrogen platelets are not essential to attaining multimegabar pressures.
Droplet spraying of heavy metal fluoride glass for optical waveguide fabrication
Authors: Broer M. M. , Bautista J. R. , Bruce A. J.
Published: July 2002

We have demonstrated a novel technique for rapid thermal quenching of heavy metal fluoride glass melts for use in optical fiber preform fabrication. Molten fluoride glass droplets were sprayed from a gas-atomizing nozzle system. Amorphous ZrF4-BaF2-LaF3-AlF3-NaF particles were obtained with very high quenching rates (∼1200 K/min) compared to bulk cast glass samples.
Investigation of oxide particles in Czochralski silicon heat treated for intrinsic gettering using scanning infrared microscopy
Authors: Laczik Z. , Booker G. R. , Bergholz W. , Falster R.
Published: July 2002

The precipitation of oxygen in Czochralski silicon slices and the effect of the resulting oxide particles on the gettering of copper have been investigated. The scanning infrared microscope was used to investigate individual particles within the bulk slices. Quantitative data on particle densities and distributions, and surface denuded zone depths for low particle densities were obtained. A major change in the precipitation behavior of copper was observed on going from just below to just above the threshold oxide precipitation level for gettering to occur.
Ionization entropy and charge-state-controlled metastable defects in semiconductors
Authors: Branz Howard M. , Crandall Richard S.
Published: July 2002

We propose a new theory of entropy-driven, charge-state-controlled metastability in semiconductors. The entropy change due to metastable defect ionization near 300 K reduces the Gibbs free energy by up to 0.1 eV. This affects equilibrium populations of the various defect charge states and configurations. An example is found in the experiment of Hamilton, Peaker, and Pantelides [Phys. Rev. Lett. 61, 1679 (1988)] in which a deep level transient spectroscopy signal suddenly disappears during cooling when the ionization entropy term causes a defect’s stable local energy minimum to become metastable.
Fermi level movement for n- and p-GaAs interfaces: Effects of temperature and dopant concentration
Authors: Anderson Steven G. , Aldao C. M. , Waddill G. D. , Vitomirov I. M. , Capasso C. , Weaver J. H.
Published: July 2002

Photoemission studies demonstrate that temperature and dopant concentration dependent movement of the surface Fermi level is controlled by coupling between adatom-induced and bulk states. At a low temperature for lightly doped n- or p-GaAs, initial band bending inhibits tunneling and EF remains near the band edges until the onset of metallicity. For heavy doping, greater band bending reflects a thinner depletion region. Thermal cycling for 20≤T≤300 K for low coverages demonstrates that band bending is reversible.
Auger effects in acceptor-doped long-wavelength strained quantum well lasers
Authors: Suemune Ikuo
Published: July 2002

Auger effects in undoped and p-doped strained quantum wells (QWs) were evaluated taking the subband nonparabolicity of the valence band into account. The Auger lifetime is relatively short mainly due to the subband nonparabolicity. However, the Auger rates in a strained QW are lower, and the threshold current reduced to about 1/4 of that in a lattice-matched QW is expected. It is concluded that a high-speed laser with a relaxation oscillation frequency of near 70 GHz and with a relatively low threshold current 500 A/cm2 will be realized in a p-doped (∼5×1018 cm−3) strained QW structure.
High-frequency study of nonequilibrium transport in heterostructure bipolar transistors
Authors: Chen Y. K. , Levi A. F. J. , Nottenburg R. N. , Beton P. H. , Panish M. B.
Published: July 2002

We report results of studying nonequilibrium transport in heterostructure bipolar transistors at a millimeter-wave band. Increasing the total potential drop in the collector from 0.88 to 1.6 eV changes the measured intrinsic transit delay from 0.32 to 0.63 ps due to the increasing importance of intervalley scattering. Both the experimental and calculated data illustrate the role nonequilibrium transport and intervalley scattering have in determining the fundamental limits to device performance.
Frequency modulation response of tunable two-segment distributed feedback lasers
Authors: Kuznetsov M. , Willner A. E. , Kaminow I. P.
Published: July 2002

We describe for the first time the theory of frequency modulation (FM) response in distributed feedback (DFB) lasers with two active segments. FM response is enhanced due to two-segment operation; the enhancement decreases at higher modulation frequencies and higher photon densities. Bandwidth of the response can extend to the multigigahertz range. The FM response is dramatically different in lasers operating in the red- and blue-shifted static tuning regimes. We find good agreement between the theory and our measurements of multigigahertz FM response of two-segment DFB lasers.
Differential photoconductive sampling with a resolution independent of carrier lifetime
Authors: Paslaski J. , Yariv A.
Published: July 2002

We present a novel approach to photoconductive sampling with a resolution which is virtually independent of the carrier lifetime and is governed solely by the circuit-limited gap charging time. Using photoconductors with a carrier lifetime of 150 ps, accurate measurement of a 65-ps-wide electrical signal is demonstrated and the actual resolution is believed to be 10 ps.
Efficient phosphorus doping of amorphous silicon carbide films
Authors: Bapat D. R. , Narasimhan K. L. , Kumar Shailendra , Sardesai A. , Kshirsagar S. T.
Published: July 2002

In this letter we report on improved phosphorus incorporation in amorphous SiC films as measured by the dc conductivity and activation energy. In this process, we show that preheating of the gas mixture is an important process parameter which leads to improved impurity incorporation.
Si-Si1−xGex n-type resonant tunnel structures
Authors: Rajakarunanayake Y. , McGill T. C.
Published: July 2002

We report the first study of n-type Si-Si1−xGex resonant tunnel structures. Strain effects in these structures induce splittings of the sixfold conduction bands into twofold and fourfold states, and change the band-edge profiles considerably. We demonstrate that resonant tunneling due to twofold, fourfold, or twofold and fourfold electrons can be selectively achieved by a proper choice of the layer thicknesses and alloy concentrations in the barrier layers. The possibilities for using these phenomena for making electron filters and making accurate determinations of the band offsets are discussed.
Heteroepitaxial In0.1Ga0.9As metal-semiconductor field-effect transistors fabricated on GaAs and Si substrates
Authors: Wang G. W. , Ito C. , Feng M. , Kaliski R. , McIntyre D. , Lau C. , Eu V. K.
Published: July 2002

We present a comparison of device characteristics for In0.1 Ga0.9 As metal-semiconductor field-effect transistors (MESFETs) fabricated on GaAs and silicon substrates. The In0.1Ga0.9As layers are heteroepitaxially grown on GaAs and silicon substrates by metalorganic chemical vapor deposition. 0.5 μm gate devices fabricated on the GaAs substrate show a maximum extrinsic transconductance of 450 mS/mm and a current-gain cutoff frequency ft of 55 GHz. Despite the large lattice mismatch, the In0.1 Ga0.9 As MESFETs fabricated on the silicon substrate show a comparable ft of 52 GHz with a lower gain.
Break junction measurement of the tunneling gap of a thallium-based high-temperature superconductor crystal
Authors: Moreland John , Ginley D. S. , Venturini E. L. , Morosin B.
Published: July 2002

We have used the break junction method to measure the tunneling gap of a thallium-based high-temperature superconductor crystal in liquid helium at 4 K. The crystal was predominantly Tl2CaBa2Cu2O7 and had a superconducting onset temperature of 105 K. Tunneling data showed a symmetric gap about zero bias between two well-defined conductance peaks in the conductance versus voltage curve. The gap is consistent with a Bardeen–Cooper–Schrieffer energy gap (Δ) of 30 meV assuming a superconductor-insulator-superconductor electrode configuration. In addition, a supercurrent could be detected when the break junction was operated in a point-contact mode at temperatures as high as 95 K.
Magnetic measurements of superconducting glass-ceramic fine rods in Bi1Ca1Sr1Cu2Al0.5Ox prepared under a temperature gradient
Authors: Higashida Yutaka , Yokoyama Hisanori , Michishita Kazuo , Kubo Yukio , Yoshida Hiroshi , Abe Yoshihiro , Hosono Hideo
Published: July 2002

It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.
Angle tuning characteristics of second-harmonic generation in KTiOPO4
Authors: Nishikawa Tadashi , Uesugi Naoshi , Ito Hiromasa
Published: July 2002

The angle tuning characteristics of second-harmonic generation in KTP were experimentally demonstrated using stimulated Raman light in a single-mode fiber as a fundamental light source. The type II phase-matching condition for second-harmonic generation in the y-z plane can be satisfied over the range 1.06 –1.85 μm by varying the incident angle in the θ direction by 29°. The acceptance angles in the θ direction for type I and type II interactions were also measured. These experimental results agreed well with the theoretical values. It is also found that the effective nonlinear coefficient for type I interaction obtained experimentally is larger than the calculated value from nonlinear coefficients of the crystal.
Synthesis of graphite fiber intercalated with KHg and its superconductivity
Authors: Tsukamoto J. , Fukuda S. , Takahashi A. , Murata K.
Published: July 2002

We successfully synthesized a superconducting intercalated graphite fiber for the first time. Intercalation was carried out for a highly graphitized fiber (diameter 150 μm) with potassium mercury at an elevated temperature. The fiber consists of a pure first-stage structure C4KHg and exhibits a superconducting transition at 1.4 K.
Chemical vapor deposition of CoGa and PtGa2 thin films from mixed-metalorganometallic compounds
Authors: Chen Yea-Jer , Kaesz Herbert D. , Kim Young Kwan , Müller Hans-Joachim , Williams R. Stanley , Xue Ziling
Published: July 2002

A new process for deposition of thin metal films from organometallic precursors of limited volatility has been demonstrated. Short path vapor transport of the complexes dichloro(tetracarbonylcobalt)gallium(III) tetrahydrofuranate, (CO)4CoGaCl2(THF), or platinum(bis-dimethylglyoximato)(bis-dimethylgallium), Pt{(N2C2(CH3)2O2)(GaMe2)}2, each under a stream of hydrogen, leads to the films of the intermetallic compounds CoGa and PtGa2, respectively, on substrates such as Si (100) wafer or a glass slide at 500 °C. The compounds were identified and characterized by x-ray diffraction, Auger electron and x-ray photoelectron spectroscopies. The films are crystalline and highly reflective. The CoGa film is single phased; the PtGa2 film shows a minor constituent of Pt2Ga3.
Comment on ‘‘Aluminum cladding of high T
c superconductor by thermocompression bonding’’ [Appl. Phys. Lett. 5
3, 2342 (1988)]
Authors: Harman G. G.
Published: July 2002

This response points out the long history of reliability problems with Ag−Al metallurgical couple and indicates that the proposed system is not li kely to be improved without basic metallurgical changes. (AIP)
Response to ‘‘Comment on ‘Aluminum cladding of high T
c superconductor by thermocompression bonding’ ’’ [Appl. Phys. Lett. 5
5, 321 (1989)]
Authors: Richardson T. J. , De Jonghe L. C.
Published: July 2002

We are not convinced that the objections raised by Harman require  basic me tallurgical changes , nor that further development is a waste of time and expen se. It is our belief that these grapes ought first to be tasted before they be declared sour. (AIP)
Low-crosstalk passive polarization splitters using Ti:LiNbO3 waveguide crossings
Authors: Neyer A.
Published: July 2002

In this letter the first demonstration of low-crosstalk passive polarization splitters based on Ti: LiNbO3 single-mode waveguide crossings is reported. Polarization crosstalk of less than −20 dB for both polarizations and total insertion loss figures of −2.5 dB (TE) and −3.0 dB (TM) at λ=1.3 μm have been achieved by optimizing the design and the fabrication of the intersection area. The devices operated nearly wavelength independent (±0.3 dB) over a range of 100 nm.
Damage formed by ion implantation in silicon evaluated by displaced atom density and thermal wave signal
Authors: Hara Tohru , Takahashi Shuya , Hagiwara Hiroyuki , Hiyoshi Jun , Smith W. Lee , Welles C. , Hahn S. K. , Larson L. , Wong C. C. D.
Published: July 2002

Damage formed by BF+2 and As+ implantations in Si was evaluated quantitatively. The density of displaced atoms (Dda) was determined from 1.5 MeV He+ Rutherford backscattering spectrometery. Dda increased from 4.7×1016 to 1.6×1017 cm−2 with the dose increased from 6.0×1013 to 1.3×1014 cm−2. However, Dda saturates at around 4×1017 cm−2 for all doses above 5×1014 cm−2. The thermal wave signal intensity shows the same dose dependence as Dda. This result shows that thermal wave signal intensity has a close relation with the density of displaced atoms formed by ion implantation. Therefore, quantitative damage monitorings can be achieved by thermal wave intensity measurements. Also, the variation of thermal wave signal intensity with ion implant energy was studied.
High-efficiency DF-CO2 pulsed chemical laser
Authors: Dreiling T. D. , McGann R. L.
Published: July 2002

The operation of a very efficient, high-energy DF-CO2 pulse chemical transfer laser is described. Laser specific energies as high as 21 J/ℓ  were obtained with a wall plug laser electrical efficiency of 130%. Higher laser energy can be obtained with lower efficiencies, e.g., 29 J/ℓ  at 80%. The electrical efficiency obtained herein is the highest reported to date for pulsed chemical lasers.
Atomic layer growth of silicon by excimer laser induced cryogenic chemical vapor deposition
Authors: Tanaka T. , Fukuda T. , Nagasawa Y. , Miyazaki S. , Hirose M.
Published: July 2002

Polycrystalline silicon has been grown by ArF excimer laser (193 nm) induced dissociation of Si2H6 adsorbed on a quartz substrate cooled to −69 °C. Silicon atomic layer growth has also been achieved by controlling the Si2H6 adsorbed layer thickness. It is found that the chemical reactivity of the first one monolayer of Si2H6 in contact with the growing Si surface is extremely high compared to that of the second or third Si2H6 layer. The effective photodissociation reaction rate at 193 nm for the first Si2H6 layer is estimated to be more than 40 times faster than that of an isolated Si2H6 molecule. Such high reactivity of the first monolayer is a possible mechanism of the self-limiting process in the atomic layer growth.
Thermal equilibrium behavior in inhomogeneous, undoped amorphous silicon
Authors: Jang Jin , Lee Seung Kyu , Kim Jae Boong , Chu Hye Yong , Lee Choochon
Published: July 2002

We report a new thermal equilibrium behavior in inhomogeneous, undoped amorphous silicon. The room-temperature conductivity increases by two orders of magnitude compared with the annealed value just after fast cooling from above 180 °C. The decay of the excess conductivity follows (time)−1 behavior, which is independent of the temperature. We suggest a possible explanation based on the material inhomogeneity.
Superhot electron model for ionizing radiation dose rate response of GaAs junction field-effect transistors
Authors: Lehovec K. , Notthoff J. K. , Zuleeg R.
Published: July 2002

The ionizing radiation dose rate response of GaAs junction field-effect transistors (JFETs) cannot be explained by the usual photocurrent model. A model is proposed in which superhot electrons from a region of many tens of microns are collected ballistically over the repulsive built-in P+ gate barrier of irradiated n-JFETs providing a gate current of polarity opposite to that of the ordinary junction photocurrent. Steady state is established by inflow of thermal electrons from the source which increases the bulk electron concentration and causes a drift velocity saturated drain current through the substrate at positive drain voltages. Since collection range of holes is much shorter than of electrons, p-JFETs do not exhibit this effect.
Modification of intrinsic strain at lattice-matched GaInAs/InP interfaces
Authors: Vandenberg J. M. , Panish M. B. , Hamm R. A. , Temkin H.
Published: July 2002

We have demonstrated, by high-resolution x-ray diffraction, the presence of strained regions on the scale of about one molecular layer at each interface in lattice-matched GaInAs/InP superlattices grown by gas source molecular beam epitaxy. The existence of these interfacial regions results only from the different group V element in each interface layer of the superlattice and the lack of any significant diffusion between atomic planes during, or subsequent to epitaxy. We have demonstrated that the intrinsic strain at the interfaces of lattice-matched GaInAs/InP superlattices can be modified on the same near molecular layer scale by altering the beam sequence during growth.
Study of the interface of undoped and p-doped ZnSe with GaAs and AlAs
Authors: Kassel L. , Abad H. , Garland J. W. , Raccah P. M. , Potts J. E. , Haase M. A. , Cheng H.
Published: July 2002

We have used electrolyte electroreflectance (EER) to characterize ZnSe/GaAs and ZnSe/AlAs interfaces. The great sensitivity of EER to interface space-charge regions enabled us to detect both interface crossover transitions and transitions to triangular-well interface states. The observation of these transitions provides the first unambiguous proof that the ZnSe/GaAs interface is type I and allowed us to determine the band offsets and band bendings, the diffusion lengths across each interface, and the amount of interdiffusion.
Logic inverter based on side mode injection locking in semiconductor lasers
Authors: Provost J. G. , Frey R.
Published: July 2002

The performance of a logic inverter based on injection locking in laser diodes is presented. The fast commutation rise and fall times (5 and 2 ns, respectively) allow a 150 MHz repetition rate. Due to the gain existing in laser diodes, low optical switching energies (50 fJ) and large fan-out rates (30) are also obtained, making such an inverter attractive for the purpose of parallel optical computing, particularly if semiconductor laser arrays are used in place of single laser diodes.
External-cavity InGaAs/InP graded index multiquantum well laser with a 200 nm tuning range
Authors: Lidgard A. , Tanbun-Ek T. , Logan R. A. , Temkin H. , Wecht K. W. , Olsson N. A.
Published: July 2002

A tuning range of 200 nm has been achieved with a step-graded multiquantum well InGaAs/InP laser in an external-cavity configuration. Continuous, single-mode lasing could be observed from 1440 to 1640 nm. Depending on the current density, the laser can operate both at the n=1 and n=2 quantized states. At low current density, the n=1 state gives higher gain, whereas for higher carrier densities, the n=2 level dominates. This gives rise to a flat gain profile and an extended operating range, in fact, the widest tuning range reported so far for semiconductor lasers.
Excited-state spectroscopy of identified Mg acceptor in InP
Authors: Beye A. C. , Yamada A. , Kamijoh T. , Tanoue H. , Mayer K. M. , Ohnishi N. , Shibata H. , Makita Y.
Published: July 2002

Photoluminescence experiments under resonant excitation have been performed at low temperature in Mg+-implanted bulk InP. The energy difference between the ground 1S3/2 and excited 2S3/2 states of the Mg acceptor is accurately measured by two-hole spectroscopy of Mg-acceptor bound exciton. Selective excitation of donor-acceptor pairs luminescence allows the identification of a set of 2P3/2 and 2P5/2 excited states. The measured values to be compared with similar published data obtained for Zn and C represent an additional step in the process of accurate identification of acceptors in InP.
X-ray observation of compositional modulation caused by phase decomposition in GaInP ternary alloys
Authors: Okuda Hiroshi , Kondo Makoto , Kato Kiyoko , Nakajima Kazuo
Published: July 2002

The phase decomposition of GaInP ternary alloys grown by low-pressure metalorganic vapor phase epitaxy has been investigated using x-ray diffraction. Diffuse scattering around the Bragg peaks due to compositional modulation was observed clearly for the first time, for samples containing high dislocation densities. Thermodynamically, the present growth temperature lies between the chemical and coherent spinodal lines. It is suggested that phase decomposition of the alloys occurs clearly only when the strain relaxation during crystal growth is possible under the present growth conditions.
View on linking the particle backscattering and particle-induced x-ray emission methods of materials analysis
Authors: Li-Scholz A. , Scholz W. , Stevenson K. A.
Published: July 2002

A method employing simultaneous counting of elastically backscattered ions and particle-induced x rays is demonstrated as a particularly simple means of measuring differential non-Rutherford proton scattering cross sections. This method eliminates the need to determine total projectile number, target atom density or detector solid angles, or to use any additional reference element. Applied to elemental analysis via x rays, this method should allow equal accuracy to be attained with L x rays as with K x rays. The method’s simplicity and versatility in these applications suggest the routine linking of the two materials analysis techniques in an integrated system which lends itself to successively reducing the impact of residual uncertainties in inner shell ionization cross sections.
Void formation in pulsed laser induced via/contact hole filling
Authors: Marella Paul F. , Tuckerman David B. , Pease R. Fabian
Published: July 2002

Metal (Au, Cu, and Al-1% Cu) layers sputter deposited over vias and contact holes of varying diameter and aspect ratio are melted and planarized by irradiation with either a 600 ns pulse duration flashlamp-pumped dye laser or a 35 ns pulse duration excimer laser. High aspect ratio (≳1) vias and contact holes yield metal profiles that suffer from void formation during the laser-induced flow. This void formation is explained by considering surface tension forces that, in high aspect ratio cases, act to close off the top of a hole without filling it.
Back-contacted emitter GaAs solar cells
Authors: Araújo G. L. , Martí A. , Algora C.
Published: July 2002

A new device structure to improve the performance of concentrator GaAs solar cells is described and the first experimental results are reported. The reason for such an improvement relies on a drastic reduction of the shadowing and series resistance losses based on the possibility of back contacting the emitter region of the solar cell. The experimental results obtained with devices of these types, with a simplified structure, fabricated by liquid phase epitaxy, demonstrate the feasibility and correct operation of the proposed back contact of the emitter of the cells.
Characterization of nanostructures by reflection electron microscopy
Authors: Scherer A. , Van der Gaag B. P.
Published: July 2002

We use reflection electron microscopy (REM) to analyze ion-etched nanostructures defined in compound semiconductor heterostructures. This nondestructive imaging technique allows us to characterize 10-nm-wide features with high resolution and determine their sidewall morphology on a 1 nm scale. In addition to the inherent high-resolution available from REM, we also obtain diffraction contrast from the heterostructure material, and we can image quantum wells. We routinely use this technique to characterize and accurately measure microfabricated structures with lateral dimensions below 20 nm.
Schottky barrier contacts on defect-free GaAs (110)
Authors: Liliental-Weber Zuzanna , Weber E. R. , Washburn J. , Weaver J. H.
Published: July 2002

High resolution transmission electron microscopy and analytical electron microscopy show direct evidence for defect-free interfaces produced by in situ cluster deposition of Au, Ag, and Ti onto ultrahigh vacuum-cleaved n-GaAs. In contrast to interfaces produced by atom-by-atom deposition, no specific interface reconstruction or orientation relationship and no change of stoichiometry of the GaAs near the interface was observed. Schottky barrier heights correspond to unusual Fermi level pinning positions in the upper half of the GaAs band gap, in clear contrast to values obtained for atom deposition and for diodes prepared by standard technology on GaAs (100). These results give clear evidence that Fermi level pinning for metal/GaAs interfaces formed without defects does not follow the predictions of current metal-induced gap-state models.
Localized electrodeposition induced by Joule heat at a constriction
Authors: Chen C. Julian
Published: July 2002

We report a novel localized electrodeposition process based on localized Joule heating at a constriction and the temperature dependence of the equilibrium potential at a metal-electrolyte interface. Assuming a local temperature rise of 50 K, a deposition rate as high as 2 μm per minute of copper is theoretically predicted in acidified copper sulfate solution, which is verified by a series of experiments. Scanning electron microscopy micrographs show that the deposited copper is dense and crystalline. As an immediate application of this novel phenomenon, a method of self-induced repair for incipient opens, i.e., a self-locating and self-terminating process to treat constrictions in circuits, is established.
Photoinduced electric fields in type II heterostructures
Authors: Jezewski M. , Mollot F. , Planel R.
Published: July 2002

Specially designed structures have been grown in the GaAs/GaAlAs/AlAs system, in order to get a spatial separation of photocreated electrons and holes and thus modify the band profile under illumination in a nonstandard way. The photoinduced electric field is measured by the Stark Shift of the probing quantum well luminescence. Fields as high as 25 kV/cm are obtained under 100 W/cm2 cw illumination.
Phase gratings in Fe3+-doped triglycine sulphate single crystals recorded in the ultraviolet spectral region
Authors: Montemezzani G. , Fousek J. , Günter P. , Stankowska J.
Published: July 2002

Phase gratings have been recorded in ferroelectric triglycine sulphate crystals doped with iron by interference of two ultraviolet laser beams in the 350 nm wavelength range. The recording sensitivity increases with temperature and a diffraction efficiency exceeding 60% has been reached in a 5.5-mm-thick crystal after several hours of writing with intensities of 0.1 W/cm2. The photoinduced refractive index changes are anisotropic. The recording mechanism is not connected with the photorefractive effect and is believed to be due to the redistribution of hydrogen bonds leading to structural and refractive index modifications.
Electronic optical bistability in an InGaAs/InAlAs multiple quantum well étalon at 1.5 μm wavelength
Authors: Nonaka K. , Kawamura Y. , Kawaguchi H. , Kubodera K.
Published: July 2002

Optical bistabilities due to electronic refractive index changes are observed in an InGaAs/InAlAs multiple quantum well étalon device at around 1.5 μm wavelength. The switching speeds of less than 30 ns and the induced refractive index changes of −0.1% are observed using a tunable F-center laser.