bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of hydrogen ion implantation on Al/Si Schottky diodes
Authors: Yapsir A. S. , Hadizad P. , Lu T.-M. , Corelli J. C. , Lanford W. A. , Bakhru H.
Published: July 2002

Al/Si(p) and Al/Si(n) Schottky diodes were implanted with hydrogen ions such that the peak of the hydrogen distribution was localized at the metal-semiconductor interface. Current-voltage (I-V) measurements indicated more ohmic behavior in the Al/Si(n) and more rectifying behavior in the Al/Si(p) diodes. For both cases, annealing at 200 °C for 30 min caused the I-V curves to almost revert to the pre-implantation characteristics. A similar behavior was observed using the capacitance-voltage (C-V) measurement technique. No significant change of the hydrogen concentration or redistribution of the concentration was observed after the 200 °C heat treatment. Correlation between the hydrogen depth profiling data and the electrical measurements indicated that, as far as I-V and C-V were concerned, the implanted hydrogens were electrically inactive.
Effect of hydrogen on electromigration and 1/f noise in gold films
Authors: Rodbell K. P. , Ficalora P. J. , Koch Roger
Published: July 2002

The 1/f noise of polycrystalline gold films (5 μm wide and 0.5 μm thick) was found to decrease in the presence of hydrogen, to a level comparable with that in a single-crystal gold film. Additionally, hydrogen was found to segregate to the metal-substrate interface. On the basis of these results and recent evidence in the literature, we propose that hydrogen interacting with interface defects is responsible for both the observed 1/f noise decrease and the previously reported electromigration enhancements.
Electro-optic measurement of standing waves in a GaAs coplanar waveguide
Authors: Zhu Z. H. , Pan C. L. , Lo Y. H. , Wu M. C. , Wang S. , Kolner B. H. , Wang S. Y.
Published: July 2002

We have successfully measured, for the first time, standing waves in a GaAs coplanar waveguide at frequencies of 8.2107 and 12.310 GHz by using harmonic-mixing electro-optic probing. The technique is nondestructive and has great potential in expanding the measuring frequency band to millimeter wave. This letter describes the principle of the technique, the experimental setup, and the measurement results.
Heterojunction double-barrier diodes for logic applications
Authors: Liu H. C. , Coon D. D.
Published: July 2002

The use of heterojunction double-barrier diodes in logic circuits is examined. Switching time limitations are estimated based on circuit considerations and device architecture. Dispersion effects involving quantum mechanical resonant tunneling time delay are also included. These theoretical considerations indicate that picosecond or subpicosecond switching times might be achievable with appropriately designed AlxGa1−xAs/GaAs devices.
Thermal annealing of semi-insulating GaAs under controlled arsenic pressure
Authors: Obokata T. , Sato T. , Fujii T.
Published: July 2002

Bulk, undoped, semi-insulating, liquid encapsulated Czochralski GaAs crystals have been annealed under controlled arsenic pressures, and the uniformities of EL2 concentration and resistivity were investigated. Crystals were grown from different melt compositions from Ga rich to As rich. Arsenic pressure was changed from 0 (vacuum) to 3.4×103 Torr. As a result, it was found that both EL2 concentration and resistivity in the crystal grown from As-rich melt have the lowest fluctuations around 530 Torr arsenic pressure.
Optical properties of HgTe-CdTe superlattices
Authors: Leopold D. J. , Wroge M. L. , Broerman J. G.
Published: July 2002

Optical transmittance spectra of HgTe-CdTe superlattices grown on GaAs substrates by molecular beam epitaxy were measured as a function of temperature between 40 and 360 K. Low substrate temperatures (150–170 °C) were required during growth to minimize interdiffusion and improve crystal quality. The highest quality superlattices exhibit sharp absorption edges with positive temperature coefficients in reasonable agreement with theory. In addition, many superlattices exhibit higher energy absorption features with temperature dependences similar to the lower energy fundamental absorption edge. The higher energy absorption features are associated with optical transitions involving higher order (n=2,3) superlattice minibands.
Effects of surface defects on the orientation of NiSi2 formed on Si (111) substrates
Authors: Akinci Gulden , Ohno Timothy , Williams Ellen D.
Published: July 2002

The effects of surface reconstruction, surface steps, and deposition temperature on the growth of NiSi2 on Si(111) have been investigated using low-energy electron diffraction and Auger electron spectroscopy. Surface reconstruction was changed by diffusion of Ni into the substrate, forming a ((19)1/2×(19)1/2) R±23.4° structure. On planar (unstepped) Si(111), the formation of the two domains of NiSi2 occurs under the same conditions on the (19)1/2 and the clean surface (7×7) reconstructions. On vicinal (stepped) Si(111), different step structures form on the clean and Ni-diffused surfaces. The growth of NiSi2 proceeds differently on the two step structures, both cases being different from growth on the planar surfaces. Specific types of step edges, 〈11̄0〉 vs 〈1̄1̄2〉, appear to favor formation of type B or type A silicides, respectively. At deposition temperatures above 200 °C, a considerable amount of Ni diffuses into the Si substrate without reacting. However, the orientation of the silicide which does form is the same as at lower deposition temperature.
Structure and optical properties of Ge-Si ordered superlattices
Authors: Bevk J. , Ourmazd A. , Feldman L. C. , Pearsall T. P. , Bonar J. M. , Davidson B. A. , Mannaerts J. P.
Published: July 2002

We report the synthesis, structural characterization, and optical studies of ultrathin Ge-Si superlattices, grown by molecular beam epitaxy, on (001) silicon substrates. Structures consist of alternating layers of pure Ge and Si, with layer thicknesses of 1, 2, 4, and 6 monolayers. Using high-resolution transmission electron microscopy, we provide direct observation of order in these pseudomorphic layered films. Systematic study of optical transitions by means of Schottky barrier electroreflectance reveals that each of the ordered structures displays a unique set of optical transitions. Of particular interest is the 4×4 structure which shows new, well defined optical transitions at 0.76, 1.25, and 2.31 eV. These transitions constitute the first observation of structurally induced optical transitions in Ge-Si and may make the 4×4 structure suitable for optoelectronic devices.
1.55-μm optical logic étalon with picojoule switching energy made of InGaAs/InP multiple quantum wells
Authors: Tai K. , Jewell J. L. , Tsang W. T. , Temkin H. , Panish M. , Twu Y.
Published: July 2002

We have constructed all-optical logic étalons operating in the 1.55-μm wavelength region using InGaAs/InP multiple quantum well (MQW) structures. These étalons have low-energy requirements with several nanosecond recovery times, exhibit high on/off contrast (>20:1 if desired) with large on-state transmission (>40%), and have signal gain, thus making them possible to cascade. For example, we have performed gating using 6 pJ input energy with 5:1 contrast and gain about 2 at 100 MHz operating frequency. These étalons also show optical bistability. The nonlinear coefficients for the InGaAs/InP MQW’s deduced from experimental results are found to be on the same order as those for GaAs/GaAlAs MQW’s.
Optical reading of field-effect transistors by phase-space absorption quenching in a single InGaAs quantum well conducting channel
Authors: Chemla D. S. , Bar-Joseph I. , Klingshirn C. , Miller D. A. B. , Kuo J. M. , Chang T. Y.
Published: July 2002

We present the first observation of absorption quenching by electrical control of the carrier density in a single semiconductor quantum well used as conducting channel in a field-effect transistor. The effect is large enough to allow direct reading of the transistor logic state.
Modulation of Renninger scan intensity: A new x-ray technique to characterize epitaxial structures
Authors: Greenberg B. , Ladell J.
Published: July 2002

We have demonstrated a new x-ray diffraction technique to characterize epitaxial structures. It makes use of Renninger scans [Z. Phys. 106, 141–176 (1937)] in which a crystal is rotated about the normal to a set of diffracting planes while diffraction from those planes is measured. To obtain these scans an x-ray beam passes through, and is modulated by, the epitaxial layer on the way into and/or out from a substrate reflection. The scans show multiple diffraction features from the substrate and new features which are due to the epitaxial layer. These modulations of Renniger scan intensity data, which we call MORSI, yield information about the orientation, lattice dimensions, and structural perfection of the sample in a variety of directions. In addition to the new features, changes are observed in the shape of a given multiple beam interaction from sample to sample. These appear to be due to differences in the perfection of substrate material. In this letter we report a MORSI study of a 1.4-μm-thick ZnSe layer grown by molecular beam epitaxy on a (001) oriented GaAs substrate using the GaAs (004) for the Renninger scan.
Deep levels associated with vacancy-impurity complexes in GaAs
Authors: Shen Yu-Tang , Myles Charles W.
Published: July 2002

A theory of the deep energy levels produced by triplet vacancy-impurity complexes in GaAs is described. The major chemical trends in the deep levels of a1 and b1 symmetry are predicted for 56 such complexes.
Xenon excited state density measurements in electron beam pumped XeCl laser mixtures
Authors: Kannari F. , Kimura W. D. , Seamans J. F. , Guyer Dean R.
Published: July 2002

Time-dependent density measurements of the lowest xenon excited states (5p56s) in electron beam (e-beam) pumped XeCl laser mixtures (nonlasing) are performed using pulsed hook interferometry. The e-beam pulse length is ≊0.45 μs (full width at half-maximum) with an average excitation rate of ≊250 kW/cm3. Density differences (ΔN*) of transitions at 823.2 nm (6s[3/2]02 –6p[3/2]2), 828.0 nm (6s[3/2]01 –6p[1/2]0), and 840.9 nm (6s[3/2]02 –6p[3/2]1) are obtained for various HCl and Xe concentrations. For a 98.3% Ne/1.5% Xe/0.16% HCl mixture at 3000 Torr, ΔN* (823.2 nm) and ΔN*(828.0 nm) are relatively constant at ≊3×1014 and ≊1.7×1014 cm−3, respectively. At lower initial HCl concentrations, the ΔN*(823.2 nm) density starts out similar to the 0.16% HCl case, but tends to increase dramatically during the e-beam pulse. For a 0.04% HCl mixture, a ΔN*(840.9 nm) density of ≊4.5×1015 cm−3 is measured at the end of the e-beam pulse. Preliminary comparisons of the data with a computer model show good agreement for HCl concentrations ≥0.16%, but disagreements at leaner concentrations.
Measurement of the coherence of a single-mode phase-locked diode laser array
Authors: Carlson N. W. , Masin V. J. , Lurie M. , Goldstein B. , Evans G. A.
Published: July 2002

The coherence of the light output of a single-mode phase-locked array has been experimentally measured. An analysis of the effects of partial coherence on the far-field pattern of a single-mode phased array is also presented.
Inhomogeneous lattice distortion in the heteroepitaxy of InAs on GaAs
Authors: Munekata H. , Segmüller Armin , Chang L. L.
Published: July 2002

Lattice relaxation in InAs epitaxial films, grown by molecular beam epitaxy on GaAs, has been studied by grazing-incidence x-ray diffraction, supplemented by in situ reflection electron diffraction. Inhomogeneous lattice distortion has been found in that the films consist of weakly and strongly strained regions, and the latter disappear with increasing film thickness. The (100) orientation is favored over the (110) in the formation of the strongly strained domains because of the relatively low elastic energies.
Polarization bistability in external cavity semiconductor lasers
Authors: Fujita T. , Schremer A. , Tang C. L.
Published: July 2002

Polarization bistability between the transverse electric (TE) and transverse magnetic (TM) modes is observed in an external cavity semiconductor laser. Hysteresis in the polarization-resolved output power is obtained by controlling the optical feedback power of the TE mode via an intracavity electro-optic modulator. Transitions between single external-cavity frequencies of TE and TM modes are also demonstrated. Nonlinear gain saturation is the origin of this bistability.
Lattice relaxation of pressure-induced deep centers in GaAs:Si
Authors: Li M. F. , Yu P. Y. , Weber E. R. , Hansen W.
Published: July 2002

Deep centers induced by hydrostatic pressure in GaAs:Si have been studied by deep level transient spectroscopy and constant temperature capacitance transient techniques. The capture behavior of these centers has been studied in detail and found to be consistent with the multiphonon emission theory. The pressure coefficients of the ionization energy and the barrier height are consistent with the large lattice relaxation model proposed by D. V. Lang and R. A. Logan [Phys. Rev. Lett. 39, 635 (1977)].
Inverted surface effect of p-type HgCdTe
Authors: Chen M. C.
Published: July 2002

By surface passivation using anodic sulfidization, we demonstrated that the inverted surface effect which gives rise to negative Hall coefficients commonly measured in p-type HgCdTe at low temperatures can be eliminated. Our results of Hall measurements as a function of magnetic field at 77 K and computer simulations allow us to distinguish two different existing models (with shunting or nonshunting n-type inversion layer) of the inverted surface effect. Bulk and surface transport parameters such as hole concentration, hole mobility, surface electron concentration, and surface electron mobility have been derived from computer best fits of experimental Hall coefficient curves.
Laser-induced structural instabilities in amorphous materials
Authors: Abdulhalim I. , Beserman R. , Khait Yu. L. , Weil R.
Published: July 2002

Amorphous materials irradiated by cw lasers undergo structural changes, which depend quasiperiodically on the irradiation time. The changes in the transmitted light intensity are related to the changes of the Raman line shape. The structural changes between metastable states are favored by the photogenerated free carriers.
Low internal loss separate confinement heterostructure InGaAs/InGaAsP quantum well laser
Authors: Koren U. , Miller B. I. , Su Y. K. , Koch T. L. , Bowers J. E.
Published: July 2002

The structure and properties of a high performance InGaAs/InGaAsP separate confinement heterostructure multiple quantum well laser operating at 1.54 μm are described. The laser has low threshold current (18 mA), high quantum efficiency (22% facet), high cw output power (42 mW/facet), and weak dependence of the threshold currents and efficiencies on cavity length.
Titanium-oxygen reaction at the Ti/La1.85Sr0.15CuO4 interface
Authors: Meyer H. M. , Hill D. M. , Anderson Steven G. , Weaver J. H. , Capone D. W.
Published: July 2002

High-resolution x-ray photoemission has been used to study the reaction between vapor deposited Ti and La1.85Sr0.15CuO4. For low Ti coverages we observe a sharp decrease in electron emission within ∼2 eV of the Fermi level because of disruption of hybrid Cu 3dx2−y2-O 2px,y orbitals, the loss of metallic character of the surface region, and the loss of superconductivity. Ti 2p and O 1s core level results show that oxygen is removed from the superconductor to form TiO2 at low coverages. At higher coverage, the reaction becomes diffusion limited; a Ti-rich oxide or solution grows. The Cu 2p3/2 emission shows that oxygen withdrawal rapidly reduces the Cu2+ configuration. Ti metal forms after ∼10 Å deposition.
Monte Carlo investigation of minority-electron transport in In0.53Ga0.47As
Authors: Osman M. A. , Grubin H. L.
Published: July 2002

The transport of minority electrons in p-type In0.53Ga0.47As has been investigated for 1017 and 5×1017 cm−3 doping levels. Using Monte Carlo methods and including inelastic electron-hole (e-h) scattering, it is found that the mean electron velocity for fields below 4 kV/cm is smaller when e-h scattering is included than when it is absent. The mean velocities above 4 kV/cm are higher when e-h scattering is included and reach a peak at 5 kV/cm. The study reveals that the principal contribution of the e-h scattering is a more efficient channel of electron energy relaxation, with the consequence of a significantly reduced transfer of carriers to the upper valleys for fields below 6 kV/cm.
Mechanism of a hydrogenating polycrystalline silicon in hydrogen plasma annealing
Authors: Nakazawa Kenji , Arai Hitoshi , Kohda Shigeto
Published: July 2002

The hydrogenation mechanism has been studied in the hydrogen plasma annealing of a polycrystalline silicon (polysilicon). Hydrogen depth profile measurements reveal that hydrogen atoms are introduced into the polysilicon by diffusion in which the diffusion constant and the surface density of hydrogen atoms increase as the rf power rises. The density of dangling bonds measured by electron spin resonance (ESR) shows that hydrogen atoms passivate dangling bonds more effectively with a higher rf power. By using the polysilicon hydrogenated at various rf powers, thin-film transistors (TFT’s) have been fabricated to investigate the effect of hydrogenation on the TFT field-effect mobility. The results show that hydrogen plasma annealing with a rf power of 50 W increases the field-effect mobility. However, a decrease of the field-effect mobility, which is considered to be caused by plasma induced surface damage, is also observed when the rf power is higher than 50 W.
GaAs/AlGaAs quantum well lasers with active regions grown by atomic layer epitaxy
Authors: DenBaars S. P. , Beyler C. A. , Hariz A. , Dapkus P. D.
Published: July 2002

Atomic layer epitaxy (ALE) is a relatively new crystal growth technique which allows control of the growth process at the monolayer level through a self-limiting, surface-controlled growth mechanism. We report here the use of ALE to grow high-quality GaAs/AlGaAs quantum wells and the first successful demonstration of an injection laser with a quantum well active region grown by ALE. Room-temperature threshold current densities as low as 640 A/cm2 have been achieved in nonoptimized separate confinement structures.
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u arsenic doping of epitaxial silicon at 800 °C by plasma enhanced chemical vapor deposition
Authors: Comfort James H. , Reif Rafael
Published: July 2002

A comparison of in situ arsenic doping of epitaxial silicon films deposited at 800 °C by both very low pressure chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) is presented. The growth rate and morphology of films deposited by CVD are degraded in the presence of arsine. PECVD growth rates are insensitive to arsine. Moreover, PECVD deposits show an order of magnitude increase in active dopant incorporation and exhibit superior morphology relative to CVD.
Reactive magnetron sputtering of thin-film superconductor YBa2Cu3O7−x
Authors: Char K. , Kent A. D. , Kapitulnik A. , Beasley M. R. , Geballe T. H.
Published: July 2002

Superconducting thin films of YBa2Cu3O7−x have been successfully made by co-sputtering from the three targets in an Ar and O2 mixture atmosphere. After high-temperature anneal films are superconducting with an onset temperature at 90 K, a full transition temperature as high as 88 K, and a critical current density in excess of 1×105 A/cm2 at 78 K and 2×106 A/cm2 at 4.2 K. Highly oriented thin films have been obtained on SrTiO3 {100} substrates.
Optical properties of general twisted nematic liquid-crystal displays
Authors: Ong Hiap Liew
Published: July 2002

An analytic expression for the optical field propagating normally in a general twisted nematic liquid-crystal structure is obtained for the first time. Based upon this, analytic expressions are obtained for the optical transmissions of the general twisted nematic liquid-crystal displays (including standard twisted nematic, supertwisted, supertwisted birefringence effect, lower twisted, and optical mode interference) with arbitrary polarizer orientations, liquid-crystal indices of refraction, twist angle, surface pretilt angle, and cell thickness. Routes for improving the display performances are discussed.
Monolithic integration of an AlGaAs/GaAs multiple quantum well distributed feedback laser and a grating coupler for surface emission
Authors: Noda Susumu , Kojima Keisuke , Mitsunaga Kazumasa , Kyuma Kazuo , Hamanaka Koich , Nakayama Takashi
Published: July 2002

Monolithically integrated surface-emitting device consisting of an AlGaAs/GaAs multiple quantum well distributed feedback laser and a grating coupler is demonstrated for the first time. The grating coupler was made by utilizing the properties of low loss and easily saturable absorption in the multiple quantum well structure. No additional crystal growths or complicated fabrication processes were required for the integration. An output power of 2 mW and a narrow beam divergence of 0.22° were obtained under continuous wave operation.
Defects in (111) HgTe grown by molecular beam epitaxy
Authors: Feldman R. D. , Nakahara S. , Austin R. F. , Boone T. , Opila R. L. , Wynn A. S.
Published: July 2002

Room-temperature Hall mobilities of (100) HgTe films grown by molecular beam epitaxy can reach values of 27 000–31 000 cm2 V−1 s−1, while the mobilities of (111) films are only 14 000–16 000 cm2 V−1 s−1. We show that the defects which lead to the lower mobilities of (111) films are present in the first 1000 Å of growth. Transmission electron microscope studies reveal a cellular structure of high-angle grain boundaries with some twinning about the (111) growth axis. These defects, and hence the reduced mobilities of the films, appear to result from island nucleation of the films.
Enhancement in excitonic absorption due to overlap in heavy-hole and light-hole excitons in GaAs/InAlGaAs quantum well structures
Authors: Kothiyal G. P. , Hong S. , Debbar N. , Bhattacharya P. K. , Singh J.
Published: July 2002

In this letter we present experimental and theoretical results for excitonic transitions in coherently strained GaAs/InGaAlAs multiquantum well structures grown on a GaAs substrate. Absorption spectra of the structure with the substrate removed show an extremely sharp exciton peak with an absorption constant corresponding to nearly twice the value of that in the lattice-matched GaAs/AlGaAs system. Theoretical calculations suggest that the biaxial tensile strain in the well region, occurring after the substrate is removed, causes the heavy-hole and light-hole exciton states to coincide for a specific composition of the quaternary alloy. A comparison between the experiments and theory is made and the potential for devices based on this phenomenon is discussed.
Electrical transport and i
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u x-ray studies of the formation of TiSi2 thin films on Si
Authors: Hensel J. C. , Vandenberg J. M. , Unterwald F. C. , Maury A.
Published: July 2002

The formation of TiSi2 thin films on Si has been investigated by in situ x-ray diffraction and electrical transport. The x-ray results show unequivocally that the staging proceeds through two orthorhombic polytypes of TiSi2 according to the sequence: sputter-deposited metallic Ti or TiSix alloy films on Si(001)→TiSi2 (C49 structure)→TiSi2 (C54 structure), with no evidence of lower silicides. Electrical transport shows metallic behavior for all phases and distinctive features in the annealing curves which correlate with the structural transformations. Most important, the resistivity, characteristically very high for the C49 phase, undergoes a precipitous drop at the C49→C54 transition. In the C54 phase when fully annealed the resistivity is 12.4 μΩ cm at room temperature and 0.66 μΩ cm at 4.2 K.
High-speed diffusion-driven photodetector
Authors: Kostenbauder Adnah G.
Published: July 2002

We describe a novel ultrafast photodetector based upon combining the Dember effect and optically generated fine carrier gratings. We present experimental data on prototype devices, and demonstrate that this device’s response time is limited neither by the carrier lifetime nor by the saturation-velocity transit time.
Room-temperature operation of hot-electron transistors
Authors: Levi A. F. J. , Chiu T. H.
Published: July 2002

We demonstrate the first room-temperature operation of a double heterojunction unipolar hot-electron transistor. Our test structure has a current gain greater than 10 and a measured current drive capability in excess of 1200 A cm−2. The device uses an indirect, wide-band-gap AlSb0.92As0.08 emitter and the transistor base is a 100-Å-wide InAs layer.
Effect of Ne and Ar on the performance of a high-pressure ArF* laser pumped by a small coaxial electron beam
Authors: Peters P. J. M. , Fierkens I. H. T. , Witteman W. J.
Published: July 2002

Optimizations of the F2/Ar/Ne gas composition and the optical cavity configuration were performed for an ArF* laser in the pressure range from 1 to 14 bar. The excitation source was a coaxial electron beam with a pulse length of 40 ns. From an active volume of 16 cm3 a maximum output energy of 130 mJ at a total gas pressure of 14 bar was obtained when Ne was used as the buffer gas.
Low-threshold disorder-defined buried-heterostructure AlGaAs diode lasers by anisotropic diffusion of laser-incorporated Si
Authors: Epler J. E. , Burnham R. D. , Thornton R. L. , Paoli T. L.
Published: July 2002

In laser-assisted disordering of AlGaAs heterostructures, the Si impurity is locally incorporated with a scanned laser beam. A subsequent thermal diffusion disorders the crystal layer structure by impurity-induced disordering. Data are presented indicating that under certain conditions the Si diffusion is anisotropic and proceeds most rapidly along the plane of the active region. The shape of the anisotropic disordering front is well suited to fabricating low-threshold buried-heterostructure (BH) lasers. Data describing the characteristics of the first BH lasers fabricated using the anisotropic diffusion are presented. The minimum cw threshold current is 10 mA and the maximum power output is 75 mW.
Total internal diffraction of plasmon surface polaritons
Authors: Rothenhäusler Benno , Knoll Wolfgang
Published: July 2002

Total internal diffraction of plasmon surface polariton fields by a dielectric phase grating is described. The grating was fabricated by partly desorbing thin organic multilayers deposited on top of the plasmon-carrying Ag-air interface through the regularly spaced holes of an electron microscope grid. The diffraction pattern shows for various angles of incidence a characteristic intensity distribution which can be understood taking into account a grating wave vector mediated coupling of the two plasmons corresponding to the two different layer structures.
Be incorporation in heavily doped molecular beam epitaxy grown GaAs: Evidence of nonradiative behavior by cathodoluminescence and electron acoustic measurements
Authors: Bresse J. F. , Papadopoulo A. C.
Published: July 2002

Cathodoluminescence and electroacoustic detection have been used for the characterization of Be-doped GaAs epilayers grown by molecular beam epitaxy for the doping levels greater than 6.5×1017 at. cm−3. The Be concentration dependence of cathodoluminescence intensity as well as electron acoustic intensity shows the presence of nonradiative centers for concentrations greater than 1018 at. cm−3. Besides, extended defects and doping striations are revealed by electron acoustic images for heavily Be-doped GaAs (1020 at. cm−3).
Effects of interface reactions on electrical characteristics of metal-GaAs contacts
Authors: Yu K. M. , Walukiewicz W. , Jaklevic J. M. , Haller E. E. , Sands T.
Published: July 2002

Solid-state interface reactions between metal thin films and (100) GaAs substrates at elevated temperatures are studied by conventional and heavy-ion Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Metals investigated in this study include Pt, Pd, Ni, Co, Rh, and W. Electrical properties of the metal/n-GaAs diodes undergoing annealing treatments at various temperatures were also measured with the current-voltage dependence. Optimum diodes with maximum barrier heights as well as minimum leakage currents are obtained for diodes annealed at temperatures at which a uniform thin layer of reacted phase is observable at the interface. The barrier heights of the optimum diodes show a linear dependence on the work functions of the various metals. The range of these barrier heights is limited by nonstoichiometry related defects as suggested by a recently proposed amphoteric native defect model.
Sputter deposition of YBa2Cu3O7−y thin films
Authors: Silver R. M. , Talvacchio J. , de Lozanne A. L.
Published: July 2002

Thin films of YBa2Cu3O7−y were prepared by magnetron sputtering. The films were characterized by x-ray diffraction, in situ x-ray photoelectron spectroscopy to determine the as-deposited oxygen content for various substrate temperatures, and scanning electron microscopy to analyze the microstructure. The orthorhombic phase was observed after an ex situ 700 °C anneal. We have obtained films which were completely superconducting at 82 K with 6 K transition widths.
Initial stages of the ion beam mixing process
Authors: Traverse A. , Le Boité M. G. , Névot L. , Pardo B. , Corno J.
Published: July 2002

The grazing x-ray reflectometry technique, performed on irradiated periodic multilayers, was used to study the early stages of the ion beam mixing process. We present our first results, obtained on NiAu samples irradiated with He ions. The experimental fluence dependence of the effective diffusion coefficient is in good agreement with a calculation based on a purely ballistic process.
Electronic optical bistability in a GaAs/AlGaAs strip-loaded waveguide
Authors: Warren M. , Gibbons W. , Komatsu K. , Sarid D. , Hendricks D. , Gibbs H. M. , Sugimoto M.
Published: July 2002

Optical bistability of electronic origin has been observed in strip-loaded waveguides in a GaAs/AlGaAs multiple quantum well structure. Single-mode waveguides were fabricated by reactive ion etching of an epitaxial AlGaAs layer above the quantum wells. The waveguides were operated as nonlinear Fabry–Perot étalons with 30% reflectors provided by the cleaved ends. Phase shifts of 2π were observed in some devices.
Dislocation bundle formation during liquid encapsulated Czochralski growth of GaAs crystals
Authors: Ono Haruhiko , Matsui Junji
Published: July 2002

Residual dislocations in a P-alloyed and an undoped GaAs crystal grown by the liquid encapsulated Czochralski method were investigated by transmission electron microscopy. In the undoped GaAs, dislocation bundles constructing cell walls and/or lineages consist of at least three different Burgers vectors. In the P-alloyed GaAs with low dislocation density, individual dislocation reactions were observed. Sessile dislocations were found to be formed by an interaction between two kinds of dislocations. The sessile dislocation formation may be a first step for the complicated dislocation structure in the undoped crystal.
Control of residual impurities in very high purity GaAs grown by organometallic vapor phase epitaxy
Authors: Shastry S. K. , Zemon S. , Kenneson D. G. , Lambert G.
Published: July 2002

Very high purity GaAs layers with 77 K electron mobility values as high as 210 000 cm2/V s and a compensation ratio as low as ≊0.05 (NA+ND≊1014 cm−3) have been grown by organometallic vapor phase epitaxy. 4.2 K photoluminescence and magnetophotoluminescence spectra of these layers confirm their high purity. The degree of material purity and the compensation are found to be controllably dependent on the growth conditions, the optimum growth temperature being about 650 °C at a V:III ratio of 17.5.
Microscopic spatial fluctuations of the EL2 defect in semi-insulating GaAs: Influence on bulk resistivity and correlation with implant activation
Authors: Alt H. Ch. , Schink H.
Published: July 2002

High-resolution EL2 topography has been compared with the electrical characteristics of the bulk material and Si-implanted layers by using resistivity and capacitance mapping. The typical cellular features are revealed in one-to-one correspondence. Microscopic variations of the bulk resistivity in the range 107<ρ<108 Ω cm can be explained quantitatively by fluctuations of the EL2 defect density and a constant carbon-acceptor concentration. A higher activation of Si is observed in regions with a higher EL2 density, leading to an estimated influence on threshold voltages of −28 mV/1015 cm−3 EL2 variation.
Photoluminescence from InGaAs-GaAs strained-layer superlattices grown by flow-rate modulation epitaxy
Authors: Sato Michio , Horikoshi Yoshiji
Published: July 2002

In0.063Ga0.937As-GaAs strained-layer superlattices are grown by alternately supplying organometals and arsine. This method is called flow-rate modulation epitaxy. These superlattices display low-temperature (2 K) photoluminescence with a very narrow linewidth that is less than 1 meV. Three sharp lines are clearly resolved in the photoluminescence spectra. Model calculation confirms that these lines are not caused by a fluctuation of well thickness. These lines result from electronic transitions through different exciton states, which are free and bound excitons. Flow-rate modulation epitaxy enables the growth of atomically flat InGaAs-GaAs interfaces which make the excitonic emission lines very sharp. Thus, free-exciton and impurity-bound exciton lines are well resolved.
Phthalocyanine photoelectrochemical cell prepared by a micelle disruption method
Authors: Harima Yutaka , Yamashita Kazuo , Saji Tetsuo
Published: July 2002

Photoelectrochemical characteristics of a metal-free phthalocyanine electrode prepared by a micelle disruption method are described. The novel technique is found to provide more photoactive phthalocyanine layers on indium tin oxide (ITO), compared with a vacuum sublimation technique. A short-circuit photocurrent of 0.1 mA cm−2 is obtained for the ITO/H2 Pc(MD)/I−3 -I−/Pt cell under the white light illumination of 6 mW cm−2, together with an open-circuit photovoltage of 70 mV and a fill factor of 0.42. These data lead to a value of 0.06% for the energy conversion efficiency.
Quantum interference effects in GaAs/GaAlAs bulk potential barriers
Authors: Hayes J. R. , England P. , Harbison J. P.
Published: July 2002

We have observed a large number of oscillations (10) in the current/voltage characteristic of GaAs/GaAlAs triangular potential barriers due to quantum interference effects. When an exact number of periods of a standing wave is present in the barrier there is a minimum in the transmission coefficient for electrons. As the bias is changed the electron wavelength is changed and there will once again be a minimum when the next complete period of the standing wave is incorporated. The observation of this quantum interference effect enables us to conclude that the scattering rate for hot electrons, high in the energy band of GaAs, is much less than previously assumed.
Comparative studies of ion-induced mixing of GaAs-AlAs superlattices
Authors: Mei P. , Venkatesan T. , Schwarz S. A. , Stoffel N. G. , Harbison J. P. , Hart D. L. , Florez L. A.
Published: July 2002

The species dependence of ion-induced superlattice mixing has been examined in AlAs-GaAs superlattice samples grown by molecular beam epitaxy. The interdiffusion of the superlattices induced by ion implantation with comparable ranges, doses, and subsequent thermal anneals were measured with secondary ion mass spectrometry. The effects of elements of comparable mass (Ga, As, and Ge) and comparable valence (Si and Ge) were studied. The experimental results show that Ga and As implantation cause primarily collision-induced mixing, while Ge implantation results in collision-induced mixing with additional impurity-induced mixing beyond the implant range. In comparison with Ge, Si-induced mixing is similar in nature though there is significant difference in the depth and extent of the mixing. The extent of mixing is found to depend on the local Ge or Si concentration.
Disordering of InGaAs-InP quantum wells by Si implantation
Authors: Tell B. , Johnson B. C. , Zyskind J. L. , Brown J. M. , Sulhoff J. W. , Brown-Goebeler K. F. , Miller B. I. , Koren U.
Published: July 2002

Selective disordering of In0.53Ga0.47As-InP multiple quantum well structures by ion implantation is demonstrated for the first time. As grown, annealed, and Si implanted and annealed samples were studied by transmission electron microscopy, optical absorption, and photoluminescence. A shift of the photoluminescence and absorption edge to higher energy was observed in implanted and annealed samples with respect to annealed only samples. This shift is attributed to a combination of disordering and Burstein–Moss effect.
Effects of deposition temperature of insulator films on the electrical characteristics of InP metal-insulator-semiconductor field-effect transistors
Authors: Iwase Y. , Arai F. , Sugano T.
Published: July 2002

Techniques of vapor etching of InP substrates and in situ deposition of phosphorus nitride film were applied to fabricate accumulation-mode InP metal-insulator-semiconductor field-effect transistors, where the temperature of vapor etching and deposition ranged from 250 to 500 °C. It has been found that the effective mobility of electrons in the surface layer of InP substrates decreases with the increase of the deposition temperature, and 450 °C as the substrate temperature during the etching and deposition was found to result in the smallest drain current drift, which was less than 2% of the initial value of drift.
Losses in Y-junction semiconductor laser arrays
Authors: Streifer William , Welch David F. , Berger Josef , Cross Peter S. , Scifres Don R.
Published: July 2002

Losses in Y-junction semiconductor laser arrays are shown to affect not only the thresholds and differential efficiencies, but also the array near-field mode patterns, threshold discrimination, and radiation patterns.
Electrical properties of a CdTe/InSb hetero metal-insulator-semiconductor structure
Authors: Shiina K. , Tanaka Y. , Sugiura O. , Oda S. , Matsumura M.
Published: July 2002

Electrical properties of a metal/CdTe/InSb metal-insulator-semiconductor structure have been investigated by capacitance-voltage and conductance-voltage measurements for the first time at 77 K. Interfaces of both p- and n-type InSb substrates can be controlled from accumulation states to inversion states. Distribution of interface state density evaluated by the Terman method is U shaped with the minimum value of 1012 cm−2 eV−1.
Low-threshold GaAs/AlGaAs lasers grown on Si by organometallic vapor phase epitaxy
Authors: Choi H. K. , Lee J. W. , Salerno J. P. , Connors M. K. , Tsaur B-Y. , Fan J. C. C.
Published: July 2002

Low-threshold double-heterostructure ridge-waveguide lasers have been fabricated in GaAs/AlGaAs layers grown on Si by organometallic vapor phase epitaxy. The pulsed threshold current of the best ridge-waveguide laser is 50 mA, with differential quantum efficiency of about 9% per facet. Broad-area lasers fabricated on the same wafer have pulsed threshold current densities as low as 300 A/cm2 .
Photoluminescence broadening mechanisms in high quality GaInAs-AlInAs quantum well structures
Authors: Brown A. S. , Henige J. A. , Delaney M. J.
Published: July 2002

GaInAs-AlInAs quantum well structures have been analyzed by low-temperature photoluminescence. The photoluminescence linewidth (full width at half-maximum) of thicker quantum wells (>10 nm) grown directly on AlInAs buffer layers shows that an inverse relationship exists between interface quality and AlInAs alloy quality in agreement with the theoretical analysis of J. Singh, S. Dudley, B. Davies, and K. K. Bajaj [J. Appl. Phys. 60, 3167 (1986)]. Thinner wells show much improved luminescence properties due to a growth of previous wells.
Kinematical simulation of high-resolution x-ray diffraction curves of GexSi1−x/Si strained-layer superlattices: A structural assessment
Authors: Vandenberg J. M. , Bean J. C. , Hamm R. A. , Hull R.
Published: July 2002

High-resolution x-ray diffraction (HRXRD) measurements of GexSi1−x/Si strained-layer superlattices are carried out using a four-crystal monochromator. A wide asymmetric range of extremely sharp higher order x-ray satellite peaks is observed indicating a well-defined strained-layer superlattice with abrupt interfaces. This is further confirmed by cross-section transmission electron microscopy. Using a kinematical diffraction step model which assumes ideally sharp interfaces, the thickness, strain, and composition of the GexSi1−x well could be extracted. Excellent agreement between measured and simulated x-ray satellite patterns is achieved. These results show that HRXRD together with kinematical simulation provides a powerful tool to evaluate the structural perfection of GexSi1−x/Si strained-layer superlattices.
Electric properties of the YBa2Cu3O7−δ/Au interface
Authors: Mizushima K. , Sagoi M. , Miura T. , Yoshida J.
Published: July 2002

The electric properties of YBa2Cu3O7−δ/Au interfaces were investigated. An electric contact better than 108 Ω−1/cm2 was obtained at 4.2 K for the interface. There existed, however, a normal layer between the superconducting bulk and the gold electrode, preventing the observation of the proximity effect and the quasiparticle tunneling for this material.
Rugged low-resistance contacts to YBa2Cu3Ox
Authors: Caton R. , Selim R. , Buoncristiani A. M. , Byvik C. E.
Published: July 2002

We have made rugged low-resistance contacts to the high Tc superconductor YBa2Cu3Ox by melting gold beads onto the surface of the material. After retreating the samples in oxygen, we have measured contact resistance <50 μΩ. This allowed a direct current of ≊5 A to pass through the contacts without heating while the sample remained in the superconducting state at 20 K. In this letter we present results of scanning electron microscopy, and measurements of contact resistance, critical current, and shear strength on these contacts. Such contacts will be of practical use in high current carrying applications of the new high Tc superconductors.
GaAs/(In,Ga)As, p-channel, multiple strained quantum well field-effect transistors with high transconductance and high peak saturated drain current
Authors: Zipperian T. E. , Dawson L. R. , Drummond T. J. , Schirber J. E. , Fritz I. J.
Published: July 2002

GaAs/In0.2 Ga0.8 As structures with two paralleled 10 nm quantum wells, modulation doped from the top, bottom, and middle with Be, have been fabricated into multiple strained quantum well field-effect transistors (MQWFET’s) with 1×150 μm2 Ti/Au gates and examined both illuminated and in the dark at 300 and 77 K. Measurements on van der Pauw structures fabricated simultaneously with the transistors showed hole mobilities and sheet carrier densities to be 200, 3100, and 8040 cm2/V s, and 5.7×1012, 1.8×1012, and 1.5×1012 cm−2 , at 300, 77, and 4 K, respectively. Shubnikov–de Haas measurements made below 4 K verified the existence of a double-channel two-dimensional hole gas with a strain-shifted light-hole ground state in the quantum wells with an effective hole mass of 0.15 me . A representative p-channel MQWFET showed well-saturated common-source output characteristics, both illuminated and unilluminated, at all measurement temperatures. Measured peak extrinsic transconductances and peak saturated drain currents for the unilluminated 1 μm device were 31 and 60 mS/mm and 27 and 67 mA/mm, at 300 and 77 K, respectively.
Dependence of critical thickness on growth temperature in GexSi1−x/Si superlattices
Authors: Miles R. H. , McGill T. C. , Chow P. P. , Johnson D. C. , Hauenstein R. J. , Nieh C. W. , Strathman M. D.
Published: July 2002

We present direct evidence for the dependence of critical thickness on growth temperature in a lattice-mismatched epitaxial system. Ge0.5Si0.5/Si strained-layer superlattices have been grown by molecular beam epitaxy on (100) Si substrates at temperatures between 330 and 530 °C. The extent to which lattice mismatch is accommodated by elastic strain has been determined through x-ray diffraction, channeled Rutherford backscattering spectroscopy, and transmission electron microscopy. Lattice mismatch is found to be accommodated purely elastically in a structure grown at 365 °C. Samples grown at higher temperatures are seen to display increasingly high densities of misfit-accommodating dislocations. This growth-temperature dependence may account for apparent inconsistencies in critical thickness data reported in the literature. Our results clearly demonstrate the need to account adequately for the kinetics of defect formation in the prediction of critical thicknesses.
Effects of silver and gold on the YBaCuO superconducting thin films with the use of Ag/Cu/BaO/Y2O3 and Au/Cu/BaO/Y2O3 structures
Authors: Chang Chin-An
Published: July 2002

Superconducting YBaCuO films have been fabricated from the Ag/Cu/BaO/Y2O3 and Au/Cu/BaO/Y2O3 layer structures on MgO substrates. Compared to those using only the Cu/BaO/Y2O3 structure, the addition of a silver layer to the starting structures improves the film resistances, especially at reduced annealing temperatures, allowing the study of the dependence of the superconducting transition on the annealing temperatures between 900 and 750 °C. Zero resistance is observed at 80 K for the Ag/Cu/BaO/Y2O3 structure annealed at 900 °C. The use of a gold layer, on the other hand, reduces the temperature for zero resistance to 75 K for a similarly annealed film. All the superconducting films are composed of the YBa2Cu3O7 and the Y2BaCuO7 phases, with starting compositions off that of the former. Structural and morphological analysis of the films is performed to explore the roles of silver and gold in the films formed.
Superconducting Au-YBa2Cu3O7 composites
Authors: Streitz F. H. , Cieplak M. Z. , Xiao Gang , Gavrin A. , Bakhshai A. , Chien C. L.
Published: July 2002

Superconducting Au-YBa2Cu3O7 composites have been fabricated over a Au volume fraction range of 0–100%. Microstructure measurement indicates that Au and YBa2Cu3O7 form well-separated phases. The superconducting transition temperature Tc was found unaffected by the presence of Au. The composites exhibit low normal state resistivity and much improved ductility. The results suggest that Au is an excellent metal host for making ultrafine YBa2Cu3O7 granular solids.
Silicon dioxide deposition at 100 °C using vacuum ultraviolet light
Authors: Marks Jeffrey , Robertson Ruby E.
Published: July 2002

A new photochemical reaction for low-temperature deposition of silicon dioxide has been developed. In this process silane is reacted with nitrogen dioxide in the presence of vacuum ultraviolet radiation. The electrical and mechanical properties of films grown at 100 °C are reported. Capacitance voltage measurements on metal-oxide-semiconductor structures on silicon indicate an interface state density <5×1011/cm2. Several possible reaction mechanisms are discussed, and evidence is presented indicating surface photochemistry may be important.
Buried heterostructure AlxGa1−xAs-GaAs quantum well lasers by Ge diffusion from the vapor
Authors: Deppe D. G. , Plano W. E. , Dallesasse J. M. , Hall D. C. , Guido L. J. , Holonyak N.
Published: July 2002

Data are presented on a method to diffuse Ge into quantum well AlxGa1−xAs-GaAs crystals from a vapor source, thus effecting impurity-induced layer disordering, and shift from lower to higher gap. The Ge diffusion is characterized on undoped GaAs by using secondary ion mass spectroscopy and capacitance-voltage electrochemical profiling. The layer disordering with Ge is used to fabricate 5-μm-wide buried heterostructure quantum well lasers (250 μm long) with continuous wave thresholds as low as 7 mA and output powers of greater than 90 mW (both facets).