bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution electron microscopy of the GaAs/AlGaAs heterointerface with (200) and transmitted beams
Authors: Ikarashi Nobuyuki , Sakai Akira , Baba Toshio , Ishida Koichi
Published: July 2002

In 〈100〉 cross-sectional high-resolution electron microscopy of the GaAs/AlAs heterointerface, images were formed only with chemically sensitive (200) and transmitted beams. The atomic configuration of the GaAs/AlAs interface can be characterized by the variation of (200) fringes at atomic resolutions. The large difference in the (200) fringe intensity between GaAs and AlAs layers greatly improves the visibility at the interface and relaxed the restriction on sample thickness. It is also shown that this technique is effective in observing the heterointerface of close compositions such as GaAs/AlGaAs.
Ion-milled lenses and lens arrays in yttrium iron garnet-gadolinium gallium garnet waveguides
Authors: Vu T. Q. , Tsai C. S. , Young D. , Wang C. L.
Published: July 2002

Waveguide lenses have been formed for the first time in yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides by using ion milling. Hybrid-type single lenses, lens arrays, and collimation-Fourier-transform lens pairs fabricated have shown good efficiency and near-diffraction-limited focal spot sizes. These waveguide lenses should facilitate realization of magnetostatic wave based integrated magneto-optic device modules for applications in communications and signal processing.
Reduction of specific contact resistance on GaInAsP by rapid thermal process anneal
Authors: Kanack B. , Carter R. L. , Appelbaum A. , Wolf D.
Published: July 2002

An order of magnitude improvement in the specific contact resistance of gold-based ohmic contacts to p-type GaInAsP (Eg=1.13 eV) is reported. A novel technique using a silicon susceptor has been employed in a rapid thermal processor. A direct comparison between gold-based contacts annealed in a conventional furnace and the rapid thermal processor indicated a specific contact resistance of 4.2×10−5 and 4.1×10−6 Ω cm2, respectively. Auger electron spectroscopy, in depth profile mode, revealed two different metallurgical profiles for the conventional furnace and the rapid thermal processor. The rapid thermal processor was successfully implemented in a p-i-n optical detector process resulting in a reduction in the device series resistance and improved performance.
Wide-range wavelength tuning of an asymmetric dual quantum well laser with inhomogeneous current injection
Authors: Ikeda Sotomitsu , Shimizu Akira , Sekiguchi Yoshinobu , Hasegawa Mitsutoshi , Kaneko Kumiko , Hara Toshitami
Published: July 2002

A new asymmetric dual quantum well laser diode with a segmented contact is proposed. With inhomogeneous current injection, the lasing wavelength can be changed quasi-continuously over 22 nm, which is much wider than any tuning range previously reported. To achieve such wide-range tuning, it is found to be essential that the length of the cavity and each segment (and the mirror reflectivity) of the laser diode should be within an optimized range. In the asymmetric dual quantum well laser diode structure used in the present experiment, in particular, the cavity length should be such that light of a shorter wavelength lases under homogeneous excitation.
Giant optical nonlinearity due to biexcitons in CuCl
Authors: Nagasawa N. , Kuwata M. , Hanamura E. , Itoh T. , Mysyrowicz A.
Published: July 2002

A lower limit for the value of χ(3) associated with the two-photon resonance of the Γ1 biexcitons in CuCl at 1.6 K is found to be 5.4×10−5 esu. The upper bound of the two-photon resonance width is ΔE=0.02 meV. Broadening of the resonance occurs for light intensities I0>103 W/cm2.
Observation of nonlinear optical transmission and switching phenomena in polydiacetylene-based directional couplers
Authors: Townsend Paul D. , Jackel J. L. , Baker Gregory L. , Shelburne J. A. , Etemad S.
Published: July 2002

Nonlinear optical transmission and switching phenomena have been observed in directional coupler devices fabricated from soluble polydiacetylenes. Effects due to both slow thermal nonlinearities and ultrafast (picosecond) electronic nonlinearities were identified. At the operating wavelength of 1.06 μm used here, the ultrafast electronic nonlinear phenomena originated from intensity-dependent changes in the imaginary part of the refractive index due to two-photon absorption effects.
Reduction of secondary defect formation in MeV B+ ion-implanted Si (100)
Authors: Lu W. X. , Qian Y. H. , Tian R. H. , Wang Z. L. , Schreutelkamp R. J. , Liefting J. R. , Saris F. W.
Published: July 2002

MeV ion implantation in Si above a dose of 1014/cm2 leads to secondary defect formation in a buried layer, which is rather stable. Annealing of Si(100) implanted with 2.0 MeV B+ ions to a dose of 2.2×1014/cm2 has been investigated by means of cross-sectional transmission electron microscopy. After annealing at 900 °C for 15 min, dislocation loops elongated along [110] were found. A remarkable decrease in secondary defect formation has been observed if, in addition, 140 keV Si+ was implanted prior to annealing.
Plan-view transmission electron diffraction measurement of roughness at buried Si/SiO2 interfaces
Authors: Gibson J. M. , Lanzerotti M. Y. , Elser V.
Published: July 2002

We have developed a novel technique for determining interfacial roughness from plan-view transmission electron diffraction. Certain bulk forbidden Bragg reflections can occur due to crystal termination at surfaces and are very sensitive to steps on crystal boundaries. We demonstrate the technique in the study of Si/SiO2 interfaces and observe that interfaces appear to be significantly flatter than previously found, especially after post-oxidation annealing. The technique is simply quantified and is more reliable than those which require stripping of the oxide to expose the interface.
Temperature dependence of acceptor-hole recombination in germanium
Authors: Darken L. S. , Jellison G. E.
Published: July 2002

The recombination kinetics of several centers (Zn−, Cu−, B−, CuH−2, CuH−x, Zn=, Cu=, and CuH=x ) in high-purity Ge have been measured as a function of temperature from 8 to 160 K by transient capacitance techniques and are significantly faster than expected from cascade theory. The cascade theory also gives the wrong temperature dependence, and the wrong z dependence. Instead, the data are generally fit by the expression Nv/4pτc≂kT/h (p and τc are, respectively, the free-hole concentration in the sample and the experimental mean capture time for a center).
Laser zone-melted Bi-Sr-Ca-Cu-O thick films
Authors: Levinson M. , Shah S. S. P. , Wang D. Y.
Published: July 2002

Directionally solidified superconducting Bi-Sr-Ca-Cu-O thick films have been fabricated by laser zone melting. Highly aligned grain structures were obtained. Films with no post-processing anneal showed Tc(R=0)=82 K and transport critical current densities Jc as high as 450 A/cm2 at 77 K and 5400 A/cm2 at 60 K. After annealing for 65 h at 850 °C, Tc increased to 85 K, and the best sample showed Jc =2200 A/cm2 at 77 K and 11 200 A/cm2 at 60 K.
Enhanced corrosion resistance in noble metal containing amorphous chromium alloys
Authors: Tenhover M. , Shreve G. A. , Henderson R. S. , Lukco D. B.
Published: July 2002

The addition of noble metals to Cr-based amorphous alloys can dramatically improve their corrosion resistance. The results of x-ray photoemission spectroscopy and cathodic polarization measurements show that the noble metals concentrate on the surface of the alloys and affect both the cathodic and anodic reaction kinetics. The amorphous Cr alloys require far less noble metal content to provide corrosion resistance in HCl compared to the corresponding crystalline Cr alloys. This allows the development of amorphous Cr alloys that are extremely stable in both reducing and oxidizing acids at high temperatures.
Radiation effects in ultrathin nitrided oxides prepared by rapid thermal processing
Authors: Lo G. Q. , Shih D. K. , Ting W. C. , Kwong D. L.
Published: July 2002

The radiation hardness of metal-oxide semiconductor capacitors with nitrided oxides prepared by rapid thermal nitridation (RTN) has been studied. The radiation was performed by exposing devices to 50 keV x ray to a dose of 0.5 Mrad (Si). Compared to conventional thermal oxides, the rapid thermal nitrided oxide devices exhibit much less increase in the interface state density (Dit). In addition, it is found that higher RTN temperatures and/or longer durations produce smaller ΔDit. The significant reduction of the interface state generation has been attributed to the strain relief effect due to the incorporation of nitrogen at the Si/SixNyOz interface. The bond strain related models have been discussed to explain the results.
Stacking fault induced relative dipole at type A/B NiSi2/Si (111) interfaces and its correlation to the Si (111) 7×7 subunit cell structures
Authors: Yeh J.-J.
Published: July 2002

The change in electronic structure from a type A to a type B NiSi2/Si(111) interface is sufficient to explain the previously observed difference in the Schottky barrier heights of these two interfaces. This is supported by the observation by scanning tunneling microscopy of different contrast on the faulted triangle in a Si(111) 7×7 unit cell relative to the unfaulted one. The crystallographic differences in the two types of NiSi2/Si(111) interfaces are identical to those in two types of triangles inside a Si(111) 7×7 unit cell. A simple model with an interface dipole induced by the stacking fault is proposed to be responsible for the 0.13 eV difference in the Schottky barriers at type B NiSi2/Si(111) interfaces relative to type A interfaces. The estimated dipole change is about 0.004e− per interface bond, in good agreement with a theoretical estimation at the stacking fault of bulk Si.
Electrical properties of hydrogenated diamond
Authors: Albin Sacharia , Watkins Linwood
Published: July 2002

Hydrogen passivation of deep traps in diamond is demonstrated. Current-voltage (I-V) characteristics of polycrystalline thin film and bulk diamond were studied before and after hydrogenation. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I-V characteristics of the samples. The concentration of uncompensated traps was varied systematically by hydrogenation. The concentration of electrically active hydrogen was determined from the I-V data. It is shown that hydrogenation is an alternative to deep-level transient spectroscopy, suitable for characterization of traps in a wide-band-gap material like diamond.
Quantum well superluminescent diode with very wide emission spectrum
Authors: Chen T. R. , Eng L. , Zhuang Y. H. , Yariv A. , Kwong N. S. , Chen P. C.
Published: July 2002

Superluminescent diodes (SLDs) employing single and multiple quantum wells were investigated. The diode structure includes a monolithic window and a gain and absorber section. Spectral widths 2–3 times that of conventional SLDs were demonstrated.
Kinetics of HgX (B-X) formation due to collisions of Ar+2 ions with CH3HgX (X=Cl, Br, I) molecules related to blue-green laser emission
Authors: Mahmood M. F.
Published: July 2002

Collisional behavior of HgX (B state) (X=Cl, Br, I) has been studied during collisions of Ar+2 ions with CH3HgX (X=Cl, Br, I) molecules in the kinetic energy (lab.) range 100–1000 eV. By using the integrated intensity of the most intense band of the (B, v′=0−X, v″=22) transitions in HgCl, HgBr, and HgI at 558, 502, and 443 nm, respectively, emission cross sections were measured at various kinetic energies of the projectile ions. The maximum values of these cross sections for dissociative excitation were found to be 3.8×10−19, 5.7×10−19, and 6.1×10−19 cm2 for HgCl (B), HgBr (B), and HgI (B), respectively.
Atomic layer epitaxy of GaInP ordered alloy
Authors: McDermott B. T. , Reid K. G. , El-Masry N. A. , Bedair S. M. , Duncan W. M. , Yin X. , Pollak Fred H.
Published: July 2002

We report on the successful growth of ordered GaInP by atomic layer epitaxy on a GaAs substrate. The growth was achieved by alternate exposures to TEI, PH3, TMGa, and PH3 fluxes, and epilayers were found to closely match the GaAs substrate irrespective of the growth conditions. Room-temperature photoreflectance results indicate a band gap of 1.78 eV, the lowest value yet reported for such ordered alloys. Photoluminescence shows an anomalous temperature dependence behavior and transmission electron microscopy studies indicate that ordering takes place preferentially on (111) alternating planes.
Characteristics of a Ta photocathode for the generation of picosecond x-ray pulses
Authors: Van Wonterghem B. , Rentzepis P. M.
Published: July 2002

The properties of laser-driven tantalum photocathodes as an electron emitter for the creation of ultrashort electron bunches and x-ray pulses are discussed. Despite the smaller quantum efficiency of metals, their inertness, damage threshold, and lifetime compare favorably with semiconductor photocathodes. Using the fourth harmonic of a Nd:YAG laser, currents of over 3 nC per pulse have been achieved which produced x-ray pulses with a brightness of 6.2×106 Cu Kα x-ray photons cm−2 sr−1 and a duration of 70 ps, as determined by an x-ray streak camera.
Magnetoresistance measurements of doping symmetry and strain effects in GaSb-AlSb quantum wells
Authors: Hansen W. , Smith T. P. , Piao J. , Beresford R. , Wang W. I.
Published: July 2002

We have made the first magnetotransport measurements of two-dimensional holes confined to GaSb in modulation-doped AlSb/GaSb heterostructures. The Shubnikov–de Haas oscillations in GaSb-AlSb heterostructures reflect the influence of strain as well as the symmetry of the confinement potential on the hole levels. We have also observed the quantized Hall effect in asymmetric single quantum wells.
Diode array side-pumped neodymium-doped gadolinium scandium gallium garnet rod and slab lasers
Authors: Caffey David P. , Utano Richard A. , Allik Toomas H.
Published: July 2002

Gadolinium scandium gallium garnet (GSGG) was studied as a high average power laser host material utilizing diode array side pumping. Maximum optical slope efficiencies of 41.5% for Nd:GSGG in the rod geometry and 32.5% for a Nd:Cr:GSGG zig-zag slab were obtained at 1.06 μm. Nd:GSGG and Nd:YAG have similar fluorescence lifetimes while Nd:GSGG has better energy storage capabilities due to its smaller stimulated-emission cross section.
Hemispherical resonator study for surface-emitting InGaAsP/InP lasers
Authors: Jing X. L. , Ho J. C. , Yu P. K. L.
Published: July 2002

For making surface-emitting lasers such as InGaAsP/InP double-heterostructure lasers, it is important to select and study the resonator properly. The authors have compared the relative light output power of two different structures, the plane-parallel and the hemispherical resonators. The InGaAsP/InP double-heterostructure was grown by liquid phase epitaxy. The different resonators on the same wafer were fabricated using chemical etching, lithography, evaporation, and other integrated circuit process techniques. Output optical power of the devices with the hemispherical resonator is a factor of 2 larger than those with the plane-parallel resonator. This is because the hemispherical resonator structure has a smaller diffraction loss than the plane-parallel structure.
HgCdTe all-epitaxial semiconductor/semimetal Schottky photodiode
Authors: Sulhoff J. W. , Zyskind J. L. , Burrus C. A. , Feldman R. D. , Austin R. F.
Published: July 2002

We propose and demonstrate an all-epitaxial semiconductor/semimetal Schottky (S3) photodiode based on an n-type Hg0.56Cd0.46 Te/HgTe isotype heterojunction. The structure, grown using molecular beam epitaxy, was fabricated into back-illuminated mesa diodes. A 40-μm-diam photodiode shows room-temperature rectification and high efficiency photoresponse, with a long-wavelength cutoff of 2.43 μm and a peak quantum efficiency of 44% at 2.0 μm for 250 mV of reverse bias. The dark current at this bias is 100 μA.
Noncontact, highly sensitive, optical substrate temperature measurement technique
Authors: Sankur H. , Gunning W.
Published: July 2002

A novel and sensitive technique to measure the temperature of parallel-faced optical substrates is presented. The technique is based on the interference of a laser beam within the cavity formed by the flat faces of a substrate. Temperature-induced changes in the thickness and refractive index of the substrate alter the interference conditions, resulting in a large modulation of the reflected intensity of the laser beam. Advantages and disadvantages of this technique, calibration data, and potential applications are discussed.
Deep levels in edge-defined, film-fed grown silicon solar cells
Authors: Yang Y. , Mil’shtein S. , Borenstein J. T. , Hanoka J. I.
Published: July 2002

Deep level transient spectroscopoy (DLTS) was used for studies of defects in edge-defined film-fed grown solar cells. For the first time, specific electronic traps were observed and identified in this polycrystalline silicon material. The DLTS spectra were taken in the extended temperature range 80–450 K, and a number of deep centers were detected. Several dislocation- and impurity-related states were identified at low concentrations in the processed solar cells. Variations in crystal growth conditions were shown to produce a novel high-temperature peak which exhibited a strong correlation to the bulk lifetime of the solar cell.
Single-ended output GaAs/AlGaAs single quantum well laser with a dry-etched corner reflector
Authors: Hagberg M. , Larsson A. , Eng S. T.
Published: July 2002

GaAs/AlGaAs single quantum well lasers with integrated corner reflectors have been fabricated using chemically assisted ion beam etching. The air-GaAs interface is internally totally reflecting, and no coherent radiation is transmitted through the corner reflector. The corner reflector laser was compared with a conventional Fabry–Perot laser cleaved from the same wafer. An 11% reduction in threshold current and a reduction of the far-field angle from 4.4° to 0.7° was measured.
Oriented hydrocarbons transferred from a high performance lubricative amorphous C:H:Si film during sliding in a vacuum
Authors: Sugimoto Iwao , Miyake Shojiro
Published: July 2002

Amorphous C:H containing silicon film shows an extremely low friction coefficient of 0.007 when the film is rubbed with a steel ball in a vacuum. This film is deposited on steel with an electron cyclotron resonance plasma of ethylene and silane. Polarized microinfrared spectroscopy reveals that high lubrication performance is attributed to hydrocarbons transferred from the rubbed film to the ball surface and oriented along the sliding direction.
Trajectory domains in a wide-well double-barrier tunneling structure in crossed electric and magnetic fields
Authors: Martin K. P. , Ben Amor S. , Rascol J. J. L. , Higgins R. J. , Potter R. C. , Hier H.
Published: July 2002

We report a study of transport in crossed electric and magnetic (B) fields in a double-barrier tunneling structure with a wide (600 Å) well at T=1.5 K and 0<B<23 T. At B=0 we observe 21 resonances, 11 of which correspond to extended-state resonances for biases >0.85 V. Under a transverse magnetic field, the bound resonances evolve into magnetoelectric states and are shifted to higher biases. In the low bias range, for high magnetic fields, additional resonances from barrier-bound skipping states are observed. A semiclassical model for ballistic motion in crossed fields is used to determine boundaries between the different trajectory regimes (i.e., traversing, skipping, bulk-like) in the magnetic field-bias voltage space of the resonances. The model shows excellent quantitative agreement with experiment when nonparabolic corrections to the effective mass are included. In addition, the B-induced shift in the transition from bound to extended-state tunneling resonances is explained with this simple description.
Identification of silicon nitride/InGaAs interface states
Authors: Piccirillo A. , Gobbi A. L. , Ferraris M. , Giannetti R. , Bagnoli P. E.
Published: July 2002

Electrical characterization of the SiNx/InGaAs and SiNx/Si interfaces was carried out by high-frequency capacitance-voltage (C-V) measurements (1 MHz). Two impurity levels, regardless of substrate nature, have been identified and attributed to silicon dangling bond defects, such as 3/4 Si0 and 3/4 Si−. Electron spin resonance measurements, carried out both at room temperature and at 77 K, confirmed the presence of defects such as 3/4 Si0 surrounded by Si bonds.
Effect of Lorentz force on thermally activated processes of flux lines in a Bi-Sr-Ca-Cu-O film
Authors: Takamura S. , Hoshiya T. , Aruga T.
Published: July 2002

The temperature dependence of electric voltage in a Bi-Sr-Ca-Cu-O film is measured for various electric currents and magnetic fields perpendicular and parallel to the film plane, in which the direction of the electric current is both perpendicular and parallel to the magnetic field. The thermally activated flux motion is deduced from the logarithmic dependence of voltage against l/T and the relation between the transition temperature and the Lorentz force. The relation between the activation energy, the transition temperature, the Lorentz force, and the volume to hop over energy barrier is discussed.
Properties of closely spaced independently addressable lasers fabricated by impurity-induced disordering
Authors: Thornton Robert L. , Mosby William J. , Donaldson Rose M. , Paoli Thomas L.
Published: July 2002

We describe the fabrication and characteristics of closely spaced (10 μm) dual-beam laser sources by the process of impurity-induced disordering. We present data demonstrating that these devices are capable of high efficiency and reliable operation when operated in a p-side up configuration. We also show that these devices can be placed in close proximity with a minimal amount of thermal and electrical interaction between devices. These features have significant implications for the realization of high-density arrays of independently addressable lasers for optical interconnection of integrated circuits and optical imaging systems.
Dynamic optoelectronic read/write memory
Authors: Nottenburg R. N. , Levi A. F. J. , Tanbun-Ek T. , Logan R. A.
Published: July 2002

We have used multielectrode laser diodes to demonstrate a dynamic digital optoelectronic memory with read and write capability. Pulses 5 ns wide are recirculated in the system every 50 ns. Bits may be modified by applying positive or negative voltage control pulses to an intracavity absorber in the device.
Control of internal stress and Young’s modulus of Si3N4 and polycrystalline silicon thin films using the ion implantation technique
Authors: Tabata Osamu , Sugiyama Susumu , Takigawa Mitsuharu
Published: July 2002

Boron and phosphorus ions are implanted in order to control the internal stress and Young’s modulus of 200-nm-thick silicon nitride and polycrystalline silicon films prepared by low-pressure chemical vapor deposition. These ions are implanted into the middle layer of the films at doses of 1×1014 and 1×1015/cm2, then the films are annealed at 900 °C. The internal stress and Young’s modulus of these films are measured by a rectangular membrane load deflection technique [Tech. Digest, IEEE Micro Electromechanical Systems Workshop, IEEE, Salt Lake City, UT, 1989, p. 152]. Both internal stress and Young’s modulus of the silicon nitride film decrease with dose, while those of the polycrystalline silicon film do not necessarily decrease.
Flux creep in Bi2Sr2CaCu2O8 epitaxial films
Authors: Zeldov E. , Amer N. M. , Koren G. , Gupta A.
Published: July 2002

We incorporate the experimentally deduced flux line potential well structure into the flux creep model. Application of this approach to the resistive transition in Bi2Sr2CaCu2O8 epitaxial films explains the power law voltage-current characteristics and the nonlinear current dependence of the activation energy. The results cannot be accounted for by a transition into a superconducting vortex-glass phase.
Reaction and stability of metal/silicide interfaces: Ti/MoSi2 (001)
Authors: Sullivan J. P. , Hirano Toshiyuki , Komeda T. , Meyer H. M. , Trafas B. M. , Waddill G. D. , Weaver J. H.
Published: July 2002

Metal/single-crystal-silicide interface evolution has been examined for Ti/MoSi2 (001) using high-resolution synchrotron radiation and x-ray photoemission. Reaction between Ti and Si was observed for temperatures 300≤T≤873 K. At 300 K, it was limited to Ti interaction with the single Si layer terminating the cleaved MoSi2 (001) surface. Analysis of the Si 2p core level line shape showed two different interfacial reaction products with bonding characteristics of TiSi and a disordered solution of Si in Ti. Interfacial development was dominated by Si outdiffusion at higher temperatures with Si enrichment of the overlayer but not conversion to a silicide.
Effect of impurities on the thermal oxidation process in InP
Authors: Beserman R. , Cytermann C. , Brener R. , Laborde J. , Salzman I. , Weyers M. , Brauers A. , Balk P.
Published: July 2002

Sulfur (n-type) and zinc (p-type) doped and undoped InP have been thermally oxidized in the temperature range 400 °C≤T≤600 °C. The Raman scattering and Auger electron spectroscopy techniques show that the doping enhances the formation of the crystalline InPO4 phase and favors the growth of crystalline phosphorus at the oxide/InP interface.
Effect of high unintentional doping in AlGaAs barriers on scattering times in accumulation layers
Authors: Laikhtman B. , Heiblum M. , Meirav U.
Published: July 2002

Analyzing possible relaxation mechanisms in two-dimensional electron gas in GaAs-AlGaAs inverted structures we show that the existence of unintentional acceptor doping in the AlGaAs barriers, with concentration as high as 1017 cm−3, provides the only explanation for the observed transport and single particle relaxation times.
Spontaneous recombination current in InGaAs/GaAs quantum well lasers
Authors: Blood P. , Fletcher E. D. , Woodbridge K. , Vening M.
Published: July 2002

We have studied the intrinsic factors which determine the threshold current and its temperature dependence in 160-Å-wide In0.2Ga0.8As single well quantum lasers with GaAs barriers, grown by molecular beam epitaxy on GaAs substrates. By measuring the relative temperature dependence of the spontaneous emission intensity at threshold we show that radiative transitions between higher order (n=2,3) electron and heavy hole subbands make a significant contribution to the threshold current and its temperature sensitivity, even in devices where the laser transitions are between n=1 subbands. These higher transitions will also influence the dependence of threshold current and its temperature sensitivity on well width.
Tight-binding analysis of the conduction-band structure in quantum wires
Authors: Yamauchi T. , Arakawa Y. , Schulman J. N.
Published: July 2002

The tight-binding method is applied, for the first time, to the analysis of the conduction-band structure of GaAs-Al0.4Ga0.6As quantum wires which are parallel to the [110] orientation. The results indicate that the effective mass of electrons parallel to the quantum wires is about 1.45 times as large as that of bulk GaAs. This increased effective mass reduces the electron mobility of the quantum wire at low temperature compared to the value which has been expected.
Hyperconductivity in chilled beryllium metal
Authors: Mueller F. M. , Johnson K. A. , Medina W. J. , Lewis H. D. , Phillips D. S. , Hundley M. F. , Thompson J. D. , Fisk Z. , Jacobson L. A. , Maggiore C. J. , Smith J. F. , Honig E. M. , Gordon W. L. , Schirber J. E. , Kossowsky R.
Published: July 2002

It is shown that in the vicinity of 77 K beryllium has a superior specific conductance compared with the nominally excellent metallic conductors aluminum and copper. It is concluded that beryllium should be considered for some conduction applications, despite its well known toxicity problems.
High power output 1.48–1.51 μm continuously graded index separate confinement strained quantum well lasers
Authors: Tanbun-Ek T. , Logan R. A. , Olsson N. A. , Temkin H. , Sergent A. M. , Wecht K. W.
Published: July 2002

A record high power output strained-layer InGaAs/InP quantum well laser emitting at 1.48 to 1.51 μm is demonstrated. Maximum cw output as high as 206 mW is obtained from a sample with a cavity length of 890 μm and a facet reflectivity of ∼5 and 85% for the front and the rear facets, respectively. The laser has a threshold of 30 mA and a slope efficiency as high as 0.4 mW/mA.
Growth kinetics simulation of the Al-Ga self-organization on (100) GaAs vicinal surfaces
Authors: Lu Yan-Ten , Petroff Pierre , Metiu Horia
Published: July 2002

We present results of a stochastic kinetic simulation of the segregation of Al and Ga during the mobility-enhanced epitaxial deposition on the As face of a stepped (100) GaAs surface.
Lasing phase diagram for semiconductor surface-emitting lasers
Authors: Gourley P. L.
Published: July 2002

A new tool, a lasing phase diagram, for understanding semiconductor surface-emitting injection lasers has been synthesized. The diagram shows how to design laser resonators which have the lowest possible threshold currents and highest operating efficiencies. To create this diagram, the rate equations describing the photon and electron-hole densities in the laser are solved for the steady-state conditions. The solutions are compactly summarized on a single lasing phase diagram which shows the lasing threshold current and power efficiency contours as functions of two structural parameters (mirror loss and number of quantum wells) in a two-dimensional plane. The plane is separated into three regions corresponding to lasing, marginal lasing, and nonlasing structures. The diagram predicts that, in the high reflectance limit, the threshold current is independent of mirror loss and scales directly with the number of quantum wells in the active region. The phase diagram has been successfully used to understand the lasing characteristics of many different laser structures recently reported.
High-power AlGaAs/GaAs single quantum well surface-emitting lasers with integrated 45° beam deflectors
Authors: Kim Jae-Hoon , Lang Robert J. , Larsson Anders , Lee Luke P. , Narayanan Authi A.
Published: July 2002

We report on high-power AlGaAs/GaAs graded-index single quantum well surface-emitting lasers (SELs), with etched vertical mirrors and integrated 45° beam deflectors fabricated by a tilted ion beam etching technique. 100-μm-wide, 500-μm-long, broad-area SELs exhibited a threshold current of 300 mA, a peak power of more than 380 mW, and an external differential quantum efficiency of 17% without facet coating. The SELs showed stable operation up to 7th. These results show the highest power and external differential quantum efficiency reported to date for 45° beam deflecting SELs. The full widths at half maximum of the surface-emitting far-field pattern parallel and perpendicular to the laser axis were 8.5° and 14°, respectively.
Effect of composition on the rates of photodarkening and silver photodoping in amorphous P-Se films
Authors: Kawashima Koichi , Hosono Hideo , Abe Yoshihiro
Published: July 2002

Rates of photodarkening and photodoping of silver were examined in binary PxSe1−x amorphous films over a wide range from x=1 to 0.4. No monotonic change with x was observed for either of the rates. The photodarkening rate remained almost constant in the ranges of x<0.85, was reduced drastically by two orders of magnitude around x≊0.9, and became constant again in 0.95<x. A similar composition dependence was observed also for the photodoping rate. These results suggest that the presence of the critical composition in both rates is due to the change in the nature of uppermost orbitals of the valence band.
Frequency stabilization of a 612 nm He-Ne laser in a transverse magnetic field
Authors: Eom Cheon Il , Eom Tae Bong , Chung Myung Sai
Published: July 2002

A simple and versatile frequency stabilization of a 612 nm He-Ne laser in a transverse magnetic field by the beat frequency stabilization method has been presented. The characteristic magnetic field was 250 G and the width of the single-mode region was approximately 220 MHz. The obtained frequency stability (Δf/f ) was 5×10−9 over a 1 h period.
Conservation and filling of neutral hole traps in SiO2 during ionizing radiation exposure
Authors: Lipkin L. , Reisman A. , Williams C. K.
Published: July 2002

The question of whether ionizing radiation creates fixed positive charge and/or neutral hole traps, or simply fills existing neutral hole traps has been examined by equating the density of intrinsic neutral hole traps, present before irradiation, with the sum of fixed positive charge and the remaining neutral hole traps present after x-ray irradiation. The total number of positive Coulombic and neutral hole traps was found to remain constant, regardless of the level of radiation the device receives. This indicates strongly that fixed positive charge represents filled intrinsic hole traps and that additional hole trapping defects, except for a small amount of fixed negative charge, are not generated by ionizing radiation in the photon energy range studied.
Reduction reaction of native oxide at the initial stage of GeH4 chemical vapor deposition on (100) Si
Authors: Takahasi Yasuo , Ishii Hiromu , Fujinaga Kiyohisa
Published: July 2002

The existence of offset time t0 for the Ge deposition is found at the initial stage of Ge epitaxial growth on the Si(100) surface. The t0 is measured for various GeH4 pressures and Si surface conditions. From this investigation, it was determined that the t0 corresponded to the period for the reduction reaction of surface native Si oxide. It was concluded that the two surface SixO molecules were reduced by one GeH4 molecule.
Native oxidation of the Si(001) surface: Evidence for an interfacial phase
Authors: Renaud G. , Fuoss P. H. , Ourmazd A. , Bevk J. , Freer B. S. , Hahn P. O.
Published: July 2002

We have used grazing incidence x-ray scattering techniques to investigate the structure of the Si-SiO2 interface, obtained by native oxidation of a Si(001) surface. The x-ray diffraction patterns reveal a twofold symmetric interfacial phase, of 2×1 periodicity. This interfacial phase, which is coherent with the silicon substrate, extends over very large lateral distances (up to 5000 Å) and is less than 5 Å thick. This phase is very disordered at the atomic scale. Its extent and perfection strongly depend on the flatness of the initial silicon substrate.
Rastered, uniformly separated wavelengths emitted from a two-dimensional vertical-cavity surface-emitting laser array
Authors: Chang-Hasnain C. J. , Wullert J. R. , Harbison J. P. , Florez L. T. , Stoffel N. G. , Maeda M. W.
Published: July 2002

We report the first two-dimensional vertical-cavity surface-emitting laser (VCSEL) array with each laser emitting a unique, nonredundant wavelength. This was achieved by implementing spatially chirped layers in the VCSEL structure and obliquely aligning the array axes to the direction of the thickness chirp. We obtained 77 wavelengths from a 7×11 VCSEL array with all the lasers emitting single mode. Uniform wavelength separation between neighboring lasers is achieved with the direction of increasing wavelength rastering through the array. All the lasers exhibit nearly the same optical and electrical properties, in spite of the intentionally implemented difference in the emission wavelengths.
Raman characterization of single defect layers embedded in finite superlattices
Authors: Schwartz G. P. , Gualtieri G. J. , Sunder W. A.
Published: July 2002

Single defect layers embedded in finite, nominally periodic superlattices have been examined using Raman scattering. The spectrum of zone-folded acoustic phonons exhibits defect-associated peaks due to the broken symmetry of the lattice. The frequencies and intensities of these additional modes can be qualitatively estimated using a simple photoelastic coupling model. Shifts in the defect mode frequencies are observed when the spatial location of the defect layer is moved from the substrate to the air interface.
Dependence of lasing characteristics of quantum well lasers on substrate orientation: Tight-binding theory
Authors: Takahashi T. , Schulman J. N. , Arakawa Y.
Published: July 2002

Band-structure analysis using the tight-binding method indicates that there is a significant dependence of lasing properties of GaAs/AlGaAs quantum well lasers on substrate orientation, which suggests the importance of choosing the substrate orientation carefully for improving lasing properties. These results are mainly due to changes in the in-plane effective mass of the heavy hole.
Hydrogen passivation in Cd1−xZnxTe studied by photoluminescence
Authors: Chen Y. F. , Tsai C. S. , Chang Y. H. , Chang Y. M. , Chen T. K. , Pang Y. M.
Published: July 2002

It is shown for the first time that deep defects in single-crystal CdZnTe can be passivated by atomic hydrogen. This treatment can result in a strong enhancement in the photoluminescence intensity of all excitonic transitions. In addition, it is shown that after hydrogenation, the higher-order emission of free exciton in CdZnTe alloys is observed for the first time; the mixed bands can be separated; the LO phonon energy, the binding energy of free exciton, and the concentration of Zn content are also determined. From the experimental results it is inferred that hydrogenation not only improves the sample quality but also provides an excellent opportunity to probe the physical properties of a material.
Optical anisotropy in mismatched InGaAs/InP heterostructures
Authors: Bennett Brian R. , del Alamo Jesús A.
Published: July 2002

Epitaxial layers of InxGa1−xAs (0.35<x<0.85) were grown on (001)InP and characterized by double-crystal x-ray diffraction (DCXRD) and a new technique, variable azimuthal angle ellipsometry (VAAE), in which ellipsometric measurements are taken in various crystallographic directions on the wafer. VAAE reveals significant optical anisotropy in many samples. The degree of this anisotropy is shown to be a function of lattice mismatch and relaxation as measured by DCXRD. The VAAE results exhibit a consistent cosine-shape pattern with respect to the [110] and [11̄0] directions. We explain these observations by the presence of misfit dislocations which form in an asymmetric network. Ellipsometry emerges as a potentially powerful tool for the characterization of mismatched zinc-blende heterostructures.
Reactive ion etching of polycrystalline silicon using SiCl4
Authors: Tang Y. S. , Wilkinson C. D. W.
Published: July 2002

Reactive ion etching of polycrystalline silicon using SiCl4 was used to etch 70-nm-wide structures. The etching mechanism of the process was investigated by using emission spectroscopy. It was found that the principal etchant for polycrystalline silicon is Cl+2.
Femtosecond passive mode locking of a solid-state laser by a dispersively balanced nonlinear interferometer
Authors: Spielmann Ch. , Krausz F. , Brabec T. , Wintner E. , Schmidt A. J.
Published: July 2002

A Michelson interferometer containing a nonlinear fiber in one arm and dispersion control in the other arm has been used for passive mode locking of a continuous wave Nd:glass laser. We discuss scaling issues and demonstrate the usefulness of this technique by generating ≊300 fs pulses with only Pf≊15 mW of average power in the fiber and ≊100 fs pulses with a self-starting threshold of Pf≊100 mW.
Spatial hole burning in Nd3+-fiber lasers suppressed by push-pull phase modulation
Authors: Sabert H. , Ulrich R.
Published: July 2002

Spatial hole burning causes rapid mode jumping and spectral broadening in free-running long linear Nd3+-fiber lasers. Phase modulators at either end of the resonator, operating in antiphase, provide active spatial averaging and permit stable single-mode operation with a short-term linewidth of ≊5 kHz at 1088 nm wavelength.
Monolithic integration of a resonant tunneling diode and a quantum well semiconductor laser
Authors: Gravé I. , Kan S. C. , Griffel G. , Wu S. W. , Sa’ar A. , Yariv A.
Published: July 2002

A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two-state optical memory is demonstrated.
Prevention of In evaporation and preservation of smooth surface in thermal annealing and mass transport of InP
Authors: Liau Z. L.
Published: July 2002

Slow evaporation of In from InP wafers has been investigated and identified as a major cause of surface roughness in thermal annealing and mass transport under sufficient phosphorus vapor protection. An analysis shows that In evaporation can be prevented by covering the wafer during the annealing process. However, the commonly used graphite cover by itself is inadequate protection because In vapor is able to permeate the graphite. On the other hand, InP covers alone result in problems caused by the mass transport that occurs between the InP wafer and cover. A covering scheme has been developed that uses InP covers and a quartz enclosure in addition to the graphite cover. This arrangement provides effective wafer protection permitting smooth wafer surfaces to be obtained reproducibly.
Optical properties of a single strained InGaAs/GaAs quantum well grown on vicinal GaAs surfaces
Authors: Droopad R. , Puechner R. A. , Shiralagi K. T. , Choi K. Y. , Maracas G. N.
Published: July 2002

We have studied the optical properties of single strained InxGa1−xAs/GaAs quantum wells (QWs) grown on GaAs substrates oriented off the (100) surface. Photoluminescence measurements indicate that QW structures grown on GaAs(100)5° toward (111)A possess superior interfaces as evidenced by the linewidth. There appears to be a decrease in the density of optically inactive traps as the angle of misorientation is increased, resulting in an enhanced optical efficiency at 77 K. However, these traps freeze out at 2 K and consequently, the optical efficiency of the various layers become independent of substrate orientation.
Laser selective area epitaxy of GaAs metal-semiconductor-field-effect transistor
Authors: Liu H. , Roberts J. C. , Ramdani J. , Bedair S. M.
Published: July 2002

We report for the first time the successful selective deposition and fabrication of a silicon-doped GaAs metal-semiconductor-field-effect transistor by laser-assisted chemical vapor deposition. No measurable growth or conductance outside the laser-irradiated area was observed, indicating complete selectivity was achieved. The Schottky gate contact showed an ideality factor of 1.15 and the reverse breakdown voltage is about 38 V at a leakage current density of 1 μA/(μm)2. The current saturation beyond pinch-off is fairly flat, indicating a good buffer layer and interfaces.
Enhanced silicon etching in nitrogen-containing SF6-O2 plasma
Authors: Premachandran V.
Published: July 2002

The effect of addition of small amounts of nitrogen into SF6-O2 plasma has been studied in terms of atomic fluorine concentration and the silicon etch rate. A factor of seven increase in the atomic fluorine concentration is observed when O2 along with 1% N2 is introduced into the SF6 plasma. With oxygen alone in the feed, the increase was less than a factor of 3. Consequently, an enhanced silicon etch rate is achieved in a SF6-O2-N2 plasma.
X-ray scattering study of lattice relaxation in ErAs epitaxial layers on GaAs
Authors: Miceli P. F. , Palmstro/m C. J. , Moyers K. W.
Published: July 2002

We present the results of a high-resolution x-ray scattering study of the lattice relaxation in [001]ErAs epitaxial layers grown on [001]GaAs. Three thickness regimes are found. ErAs is pseudomorphic on GaAs for thicknesses below 70 Å and between 70 and 300 Å lattice relaxation is observed concomitant with an increase of the in-plane mosaic due to the formation of misfit dislocations. Above 300 Å, the out-of-plane transverse scattering from the ErAs lattice planes is no longer specular and further relaxation appears to be related to the out-of-plane mosaic. The ratio of elastic constants, C12/C11, is measured to be 0.126. Thin-film interference oscillations are observed and modeled, finding that for 140 Å of ErAs the interface fluctuations are ∼2.5 monolayers. ErAs/GaAs is an ideal system for x-ray scattering studies of lattice relaxation and structure in epitaxial layers.
Very dense 102-laser arrays with extremely low threshold current
Authors: Hirata Shoji , Narui Hironobu , Mori Yoshifumi
Published: July 2002

102-laser arrays with a period of 4.5 μm were fabricated using single-step metalorganic chemical vapor deposition and were operated uniformly with a threshold current of 1.8 mA per laser and a total output power of 850 mW/facet under continuous wave conditions at room temperature. The active layer of each laser, which was grown on a periodic-ridge-shaped GaAs substrate and was of a multi quantum well structure, was separated from the active layer of adjacent lasers by a current blocking layer, so each laser operated in a stable fundamental lateral mode.
Ultrafast gain dynamics in 1.5 μm multiple quantum well optical amplifiers
Authors: Eisenstein G. , Wiesenfeld J. M. , Wegener M. , Sucha G. , Chemla D. S. , Weiss S. , Raybon G. , Koren U.
Published: July 2002

Following gain saturation by a short pulse, the gain recovery process in multiple quantum well optical amplifiers includes contributions from carriers occupying states with energies above the depleted states within the well, from carriers stored in the barrier layers, which serve as carrier reservoirs, and from conventional Auger recombination. Gain recovery caused by carriers from the reservoirs is rapid (7 ps) and can be made to dominate the slower (Auger) recovery process.
Novel phased array optical scanning device implemented using GaAs/AlGaAs technology
Authors: Wight D. R. , Heaton J. M. , Hughes B. T. , Birbeck J. C. H. , Hilton K. P. , Taylor D. J.
Published: July 2002

A novel type of optical beam scanning device based on the same principle as a phased array radar has been made and demonstrated. This phased array optical scanning device consisted of a uniformly illuminated array of ten closely spaced, single mode GaAs/AlGaAs electrooptic waveguides, each of which was individually addressed to give more than 2π radians of optical phase control. This gave a line of ten point sources of light on a 3 μm pitch at the output face of the array. By independently phase shifting these light sources the output wavefront was controlled to scan a 2° wide beam through 20° in the far field.
Modulated beam epitaxial growth of high quality GaAs single quantum wells at low temperature
Authors: Longenbach K. F. , Xin S. , Schwartz C. , Jiang Y. , Wang W. I.
Published: July 2002

High quality AlGaAs/GaAs quantum wells and low-threshold current density lasers (<1 kA/cm2) have been successfully grown at low temperatures (500 °C) by a modulated beam epitaxy process in which the group III flux is held constant while the As flux is periodically shut off to produce a metal-rich surface. The improved quality of these low-temperature-grown quantum structures is attributed to both a smoothing of the growth front and a reduction of excess As during the modulated beam epitaxy process. The high growth rates and less frequent shutter operation of this technique make it more practical than migration-enhanced epitaxy or atomic layer epitaxy for low-temperature growth.