bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical properties of GaAs selectively grown by electron cyclotron resonance plasma-excited molecular beam epitaxy
Authors: Yamamoto Norio , Kondo Naoto , Nanishi Yasushi
Published: July 2002

Electrical properties of GaAs layers selectively grown by electron cyclotron resonance plasma-excited molecular beam epitaxy (ECR-MBE) have been studied. Exposing a Si3N4 mask to ECR plasma introduces Si from the mask to the selectively grown layer and increases the carrier concentration of the undoped layer. By doping Si into this selectively grown layer, carrier concentrations as high as 5×1018 cm−3 could be obtained. It was also found that the carrier concentration profile did not show any decrease at the interface between the substrate and the grown layer. These results suggest that selective area growth of a heavily doped n-type layer makes ECR-MBE a very promising method to form low-resistance ohmic contacts as a regrowth process.
High-frequency properties of resonant tunneling devices
Authors: Kislov V. , Kamenev A.
Published: July 2002

Results describing the response of resonant tunneling devices to an applied high-frequency harmonic bias are produced. Appropriate coefficients for rectification, linear admittance, and generation of higher harmonics are calculated. We have shown that rectification preserves the low-frequency values up to frequencies of about 1014 Hz. At the same time linear admittance and higher harmonic generation coefficients decrease sharply at frequencies higher than the energy width of resonant level. At high frequencies reactive components of the tunneling current appear to dominate.
Nanocomposites by fractal growth of electrodeposited silver in ion-exchanged oxide glasses
Authors: Roy S. , Chakravorty D.
Published: July 2002

Clusters of metallic silver have been formed by electrodeposition within the surface of an oxide glass which was subjected to an alkali silver ion exchange process. The clusters have a fractal structure with a Hausdorff dimension D around 1.86 over a length scale 10–140 μm. Electron micrograph of the sample indicates the possibility of a crossover to a nonfractal regime at length scales of the order of a few hundred nanometers. The fractal growth within the glass results in the formation of a glass metal nanocomposite with a particle diameter around 12 nm.
Monolayer δ-doped heterojunction bipolar transistor characteristics from 10 to 350 K
Authors: Goossen K. W. , Cunningham J. E. , Kuo T. Y. , Jan W. Y. , Fonstad C. G.
Published: July 2002

Heterojunction bipolar transistors (HBTs) with bases composed of a single monolayer of dopant are found to have exponentially increasing current gain as the temperature is lowered, in contrast to the gains of homogeneously doped HBTs, which have little dependence on temperature. We present GaAs-AlGaAs HBTs with base doping as high as 3×1014 cm−2 with a room-temperature current gain of 14. The sheet resistance of such a layer is 270 Ω/square at room temperature, and the carriers are restricted to a 15 Å layer, implying an extremely short base transit time. AT 77 K the gain increases to 220, while the base resistance decreases to 190 Ω/square. Therefore by operating this HBT at low temperature we have achieved for the first time high gain and low base resistance in a HBT with an infinitesimally thin base.
Polarization selective electro-optic effect in a coupled quantum wire array
Authors: Citrin D. S. , Chang Yia-Chung
Published: July 2002

Arrays of coupled GaAs/AlAs quantum wires grown on vicinal substrates exhibit complicated interplay of one- and two-dimensional behavior. We investigate the electro-optic effect in such structures and discuss possible applications for optical switches. By application of a static electric field normal to the growth planes, the interband optical selection rules are controlled between one and two dimensional. The structure shows strong polarization dependence for the polarizations accessible to devices in the vertical configuration as well as for the polarizations accessible to devices configured for lateral integration. The relative sizes of the slots and quantum well-like portion can be chosen so that the derivatives of the optical matrix elements with respect to field are large at zero bias.
Effects of nonlinear gain on four-wave mixing and asymmetric gain saturation in a semiconductor laser amplifier
Authors: Tiemeijer L. F.
Published: July 2002

Nearly degenerate four-wave mixing (NDFWM) and asymmetric gain saturation were studied in a 1.5 μm InGaAsP semiconductor laser amplifier at highly saturated conditions (Pout ≫ Psat) and frequency separations up to 500 GHz. Apart from modulation of the carrier density the data reveal a new mechanism of NDFWM with a characteristic time of about 650 fs which takes over when the frequency separation exceeds 100 GHz.
Surface skimming buried heterostructure laser with applications to optoelectronic integration
Authors: Thornton Robert L. , Mosby William J. , Chung Harlan F.
Published: July 2002

We demonstrate the ability to fabricate low-threshold current buried heterostructure lasers with the critical active layers in close proximity to the surface of the laser crystal. These structures readily lend themselves to applications involving optical field interactions on the surface of the crystal. We further demonstrate the compatibility of these structures with lateral heterojunction bipolar transistor fabrication.
Responses of InP/Ga0.47In0.53As/InP heterojunction bipolar transistors to 1530 and 620 nm ultrafast optical pulses
Authors: Carruthers T. F. , Duling I. N. , Aina O. , Mattingly M. , Serio M.
Published: July 2002

An npn InP/Ga0.47In0.53As/InP heterojunction bipolar transistor with a unity-gain frequency of 15 GHz was illuminated with ultrafast optical pulses at wavelengths of 620 and 1530 nm. The device responded to the pulses with an emitter current transient having a duration of 12 ps, corresponding to a bandwidth of ∼40 GHz. A slower photocurrent component, with a decay time of ∼100 ps, was a sensitive function of base bias and, because of the photocarrier dynamics and the grounded-collector circuit configuration, could be nulled out.
X-ray photoelectron spectroscopy of (Fe,Co,Ni)-SiO2 granular films
Authors: Shah S. I. , Unruh K. M.
Published: July 2002

Granular films of nominal composition (Fe,Co,Ni)50(SiO2)50 were prepared by rf sputter deposition and characterized by transmission electron microscopy. In each case the films were found to consist of small metal particles, several nanometers in size, embedded in an amorphous silica matrix. The chemical composition of the metal particles was studied, for the first time, by x-ray photoelectron spectroscopy. These measurements detected the presence of the metal oxides Fe3O4, FeO, Fe2O3, CoO, NiO, and Ni2O3 associated with the Fe, Co, and Ni particles, respectively.
Gain-current calculations for bulk GaInP lasers including many-body effects
Authors: Rees P. , Summers H. D. , Blood P.
Published: July 2002

The gain-current characteristics of undoped GaInP (660-nm) bulk lasers have been calculated over a range of temperatures. The calculations use parabolic bands with strict k selection and include band-gap narrowing and lifetime broadening due to carrier-carrier interactions at high densities. The broadening lifetime τ has been implemented as a constant value of 10−13 s and as a carrier-dependent value proportional to n−1/3. Using τ=10−13 s, our calculations for GaInP at room temperature give a value for the differential gain β of 0.026 cm−1 (A cm−2 μm−1)−1 and a value for the transparency current J0 of 4.4 kA cm−2 μm−1. These are in close agreement with experimental results. Results for GaAs at room temperature are also given.
Bulk diffusion length improvement by rapid thermal gettering
Authors: Hartiti B. , Slaoui A. , Loghmarti M. , Muller J. C. , Siffert P.
Published: July 2002

Rapid thermal diffusion of phosphorus into p-type silicon from a spin-coated film containing the dopant has been studied as a function of process temperature and time duration. The electron diffusion length measurements performed by the surface photovoltage method present evidence for a gettering phenomena since the diffusion length values of the diffused silicon samples are found to exceed the initial value reported for the virgin material.
Selective electroless copper metallization of palladium silicide on silicon substrates
Authors: Mak C. Y. , Miller B. , Feldman L. C. , Weir B. E. , Higashi G. S. , Fitzgerald E. A. , Boone T. , Doherty C. J. , van Dover R. B.
Published: July 2002

A scheme for selective electroless copper patterning of Si wafers has been developed with palladium silicide as the catalytic layer initiating copper deposition. Thermal conversion of a palladium layer to silicides on a SiO2 patterned silicon substrate, followed by an acid etching of the unreacted palladium on the SiO2 surfaces, leaves only the silicided regions at the base of the windows for electroless copper deposition. Excellent via-filling down to 0.5-μm dimensions and an aspect ratio of 6 has been demonstrated. The thin copper deposited on the Pd2Si has a resistivity of ∼2.0 μΩ cm. Contactless photocarrier decay measurements indicate virtually no degradation of Si lifetimes by these processing steps.
AsH3 preflow effects on initial stages of GaAs grown on Si by metalorganic chemical vapor deposition
Authors: Fujita Kazuhisa , Asai Koyu
Published: July 2002

The effect of AsH3 preflow on initial stages of GaAs grown on Si was studied by transmission electron microscopy. As the temperature of AsH3 preflow was increased, the surface of the Si substrate became rougher: At 1000 °C, many threading dislocations originating at the rough surface were observed in the GaAs layer. In contrast, at low temperature, 450 °C, the Si surface became smooth and the dislocations were reduced. Furthermore, the Si surface was still smooth after long AsH3 preflow at 450 °C. The roughness of the Si surface is attributed to the supply of As atoms to the Si surface at high temperature.
Low-threshold and high-temperature operation of 1.55-μm self-aligned ridge-waveguide multiple-quantum-well lasers grown by chemical-beam epitaxy
Authors: Liou K.-Y. , Tsang W. T. , Choa F. S. , Burrows E. C. , Raybon G. , Burrus C. A.
Published: July 2002

We describe a low-threshold, low-internal-loss, multiple-quantum-well ridge waveguide laser operating at 1.55-μm wavelength and grown by chemical-beam epitaxy. With a high-reflection coating applied to one facet, it can operate CW to 100 °C. The laser exhibits single transverse-mode output and 6-GHz bandwidth. Processing utilizes a combination of self-aligned reactive-ion etching and wet chemical etching. Nearly 100% threshold and quantum efficiency yield of devices in bar form was obtained as a result of the excellent material uniformity, precision process control, and process uniformity over the wafer. This suggests that the present laser may be a potential candidate for low-cost light source applications.
rf-excited all-metal waveguide CO2 laser
Authors: Xin J. G. , Yan P. , Wei G. H.
Published: July 2002

In this letter, an rf-excited, anodized aluminum structure waveguide CO2 laser is presented, which has the advantages of low cost, better cooling, and ease of manufacture. With this structure, we have obtained 12 W EH11 waveguide mode output power from only a 300 mm gain length.
Electron drift velocities in xenon and xenon-nitrogen gas mixtures
Authors: Patrick E. L. , Andrews M. L. , Garscadden A.
Published: July 2002

The drift velocity of an electron swarm in pure xenon gas (99.995% pure) and xenon gas mixtures, containing 0.1%, 1%, and 10% nitrogen additive, was measured in a pulsed-Townsend drift tube in order to observe the effects of the additives on electron mobility, and to demonstrate negative differential conductivity. The digitized signal was analyzed by a microcomputer to produce swarm drift time measurements. The amount of nitrogen necessary to perturb the electron drift velocity in pure xenon is implied from these measurements.
Ion induced chemical bonding of carbon with Ta as studied by Auger electron spectroscopy and slow electron energy loss spectroscopy
Authors: Sharma J. K. N. , Bera Santanu , Chakraborty B. R.
Published: July 2002

The chemical bonding of contaminants like carbon and oxygen on the surface of Ta and Ta2O5 films due to Ar+ ion bombardment during sputter etching, has been studied using Auger electron spectroscopy and slow electron energy loss spectroscopy. Finger printing of C KLL peak shows that the energy separation between the major positive-going and negative-going excursions, which is 23 eV in the pure graphitic form, reduces to 6 eV indicating the carbide formation after ion bombardment. It is assumed that the chemical reaction is initiated by an increase in π electrons in the graphite due to ion bombardment. The carbide formation is found to be much less effected in Ta2O5 films which has been attributed to the absence of free d electrons of Ta in the oxide.
Use of surface grooves to control ordering in GaAsP
Authors: Chen G. S. , Stringfellow G. B.
Published: July 2002

GaAs1−xPx with 0.4≤x≤0.85 forms the CuPt ordered structure during organometallic vapor phase epitaxy (OMVPE). Only the (1̄11) and (11̄1) variants are observed for growth on (001)-oriented substrates. The mechanism by which ordering occurs is only now being discovered. Total energy calculations, including the effects of surface reconstruction, indicate that the phenomenon can be explained purely on the basis of energy considerations. Indirect evidence indicates that kinetic factors, including processes occurring at steps propagating across the surface in the two-dimensional growth mode, control ordering. In this work, GaAs1−xPx layers have been grown by OMVPE on (001)-oriented GaAs0.6P0.4‘‘substrates.’’ In order to examine the effects of surface kinetic factors, the substrates were first patterned with [110]-oriented grooves 5 μm wide and a fraction of a micron deep. The groove is used to provide a source of steps moving in opposite directions from the two edges. Transmission electron diffraction reveals the formation of large domains of the two variants that meet in the center of the groove. A surprising feature is the presence of a region in the groove with absolutely no ordering. Tracing the surface shape during growth using a superlattice structure indicates that the disordered region is due to growth on {511} facets. The domains formed after the groove is filled are very large, several square microns in cross-sectional area and extending along the entire length of the groove. These results demonstrate that natural ordering in GaAsP, an alloy with mixing on the group V sublattice, can be controlled by regulating the propagation of steps during growth, exactly as for GaInP where mixing is on the group III sublattice.
New method for determination of the peak-velocity in epitaxial semiconductor structures by dc measurements on microbridges
Authors: Strupinski Wlodzimierz , Zirath Herbert , Grönqvist Hans , Rorsman Niklas
Published: July 2002

A simple current-voltage measurement technique using microbridge patterns is described as a fast method for the determination of the effective peak electron velocity in III-V semiconducting materials. The method is tested for GaAs samples. Microbridge patterns with different geometries were investigated and the influence of ‘‘self-heating’’ by power dissipation was examined. Some other potential sources of errors deteriorating the accuracy of measurements were determined.
YBa2Cu3O7 whiskers grown from the gas phase
Authors: Järvinen R. J. O. , Podkletnov E. E. , Mäntylä T. A. , Laurilla J. T. , Lepistö T. K.
Published: July 2002

YBa2Cu3O7 whiskers were grown by the in situ technique using radio frequency magnetron sputtering in Ar–O2 atmosphere at a substrate temperature of 720 °C on (100) single crystal MgO substrate. High sputtering gas pressures were found to promote the formation of whiskers. Whiskers were found to start their growth from certain platelet crystals. The growth conditions for these whiskers are described and their structure is examined by analytical transmission electron microscope. These results seem to exclude the vapor–liquid–solid growth and propose direct condensation from the vapor.
Modified growth kinetics of ion induced yttrium–silicide layers during subsequent thermal annealing
Authors: Alford T. L. , Mayer J. W.
Published: July 2002

Yttrium and amorphous silicon bilayers were irradiated with 600-keV inert ions between −190 and 265 °C. Ion-induced YSi1.7 layers occurred in those samples irradiated above ≥ (R18)205 °C. These ion-mixed samples were thermally annealed at temperatures between 325 and 380 °C. The diffusion-limited growth was observed only in those samples which had an ion-induced YSi1.7 layer present prior to thermal annealing. This type of growth is distinctly different from the interface limited, nonuniform, and irreproducible growth seen during typical thermal annealing of yttrium and silicon bilayers. This type of growth still occurred in those samples annealed after ion irradiations at ≤190 °C.
Effect of annealing ambient on the removal of oxide precipitates in high-dose oxygen implanted silicon
Authors: Seraphin Supapan , Krause Stephen J. , Roitman Peter , Simons David S. , Cordts Bernhard F.
Published: July 2002

The effect of annealing ambient on the precipitate removal processes in high-dose oxygen implanted silicon [separation by implantation of oxygen (SIMOX)] has been studied with transmission electron microscopy, electron energy-loss spectroscopy, and secondary ion mass spectroscopy. The rate of removal of oxide precipitates from the top silicon layer in SIMOX is higher during annealing in argon than in nitrogen. The removal is reduced in nitrogen due to the formation of an oxynitride complex at the precipitate surfaces which inhibits oxygen diffusion across the interfaces. Similar effects have been observed for oxide precipitation during nitrogen ambient annealing in bulk silicon.
Efficient energy extraction from a diode-pumped Q-switched Tm,Ho:YLiF4 laser
Authors: McGuckin B. T. , Menzies R. T. , Hemmati H.
Published: July 2002

The operation of a diode-laser pumped thulium, holmium yttrium–lithium–fluoride laser (Tm,Ho:YLF) in Q-switched mode is reported. Output energies of 220 μJ in pulses of 22 ns duration are recorded at Q-switch frequencies commensurate with an effective upper laser level lifetime of 6 ms. This lifetime is appreciably longer than that observed in other hosts permitting stored energy extraction of 64%, close to the projected maximum performance from these materials.
Optical time-division demultiplexing using second-order-optical nonlinear effects
Authors: Lin Hong , Smith John Stephen
Published: July 2002

A novel scheme using second-order-optical nonlinear effects for optical time-division demultiplexing is proposed. This scheme is all-optical, and has potential bandwidth on the order of tera (1012) Hz. A prototype demultiplexer using this scheme has been demonstrated, achieving bit rate capacity of 100 Gb/s and crosstalk of −20 dB. This scheme could be realized in a compact form with further advances in nonlinear-waveguide devices and high-peak power semiconductor lasers.
Observation of above-barrier quasi-bound states in asymmetric single quantum wells by piezomodulated reflectivity
Authors: Dossa D. , Lew Yan Voon Lok C. , Ram-Mohan L. R. , Parks C. , Alonso R. G. , Ramdas A. K. , Melloch M. R.
Published: July 2002

The piezomodulated reflectivity spectrum of asymmetric GaAs/AlGaAs single quantum well heterostructures display interband excitonic transitions from bound and quasi-bound valence states to bound and quasi-bound states in the conduction band. The quasi-bound states with maximum occupancy in the well region in these compositionally asymmetric quantum wells participate ‘‘resonantly’’ in interband transitions. These spectra are compared with those from symmetric quantum wells with the same well width.
New deep level luminescence bands observed from both a SiGe alloy layer and Si/Ge superlattice structures
Authors: Higgs V. , Lightowlers E. C. , van de Walle G. F. A. , Gravesteijn D. J. , Montie E. A.
Published: July 2002

Photoluminescence measurements have been made on Si/Ge short period superlattice structures grown on a SiGe alloy buffer layer and on a similar SiGe alloy layer without a superlattice. Using an InSb detector with a low energy cutoff at ∼450 meV, the major luminescence features observed were two broad bands with maximum intensities at ∼530 and ∼720 meV. The luminescence intensity was found to vary with the superlattice composition but was substantially stronger for the SiGe alloy layer without a superlattice. We ascribe these luminescence features to defects in the SiGe alloy layers. This is supported by the observation that the introduction of deliberate copper contamination at 600 °C dramatically increases the photoluminescence signal.
Growth of (Pb0.75Cu0.25)Sr2(Y1−yCay)Cu2O7 thin films by laser ablation
Authors: Hughes R. A , Lu Y. , Timusk T. , Prestón J. S.
Published: July 2002

In this letter we investigate the effects of varying the values of x and y in (Pb1−xCux)Sr2(Y1−yCay)Cu2O7 films deposited by laser ablation. The films are grown in situ on (100) LaAlO3 at the relatively low substrate temperature of 620 °C. The films are highly oriented with the c-axis perpendicular to the substrate and exhibit a surface morphology which is unique to the oxide superconductors. By substituting Ca for Y it is possible to systematically vary the superconducting transition temperature from 10 K to a maximum of 86 K. On the other hand, variations in the value of x seem to suggest that the film’s copper concentration in the (PbCu) plane can only exist within the narrow range of approximately x=0.2–0.3 and any extra copper added to the target ends up in an impurity phase.
High-temperature dc superconducting quantum interference device with deep-submicron YBa2Cu3O7 weak links
Authors: Romaine Suzanne E. , Mankiewich Paul M. , Skocpol William J. , Westerwick Eric
Published: July 2002

We have fabricated a YBa2Cu3O7 (YBCO) thin-film dc superconducting quantum interference device (SQUID) with lithographically defined deep-submicron weak links. At 77 K the voltage response to dc flux is sinusoidal and nonhysteretic, with maximum peak-to-peak amplitude of 5 μV. The maximum response is 8 μV at 70 K, where 2LI0/Φ0≊1. At lower temperatures, the maximum response oscillates in the range 4–6 μV. Random telegraph noise was observed near 30–40 K. Well-behaved Shapiro steps were observable at all measured temperatures below Tc.
Application of the synchrotron white beam x-ray topography to the thermoelastic transformation studies
Authors: Jourdan C. , Belkahla S. , Guenin G. , Marzo P. , Gastaldi J. , Grange G.
Published: July 2002

The thermoelastic transformation of the CuZnAl shape memory alloy has been studied in situ and in real time by the synchrotron white beam x-ray topography technique. The evolution of the first martensite lath has been followed during the temperature cycling and its interaction with the crystal structure has been shown.
Monte Carlo particle simulation of radiation-induced heating in GaAs field-effect transistors
Authors: Moglestue C. , Buot F. A. , Anderson W. T.
Published: July 2002

Exposure of GaAs field-effect transistors to α-particle radiation has resulted in burnout paths from under the gate to both the source and the drain. Monte Carlo calculations show that the current response from an α-particle penetrating the center of the gate electrode at normal incidence lasts for 60 ps, about five times longer than predicted by previous hydrodynamic modeling. The thermalization of the induced electrons causes a maximum subsurface heating of the epilayer near the source and the drain when both are held at ground with a negative bias on the gate. A possible melting of the semiconductor will take place at these locations. We present here for the first time a more accurate simulation of the actual lattice heating rates obtained from electron-phonon exchanges inside the device. Although the qualitative results support the previous hydrodynamic analysis, some important quantitative differences are noted.
1.5 μm wavelength InGaAs/InGaAsP distributed feedback multi-quantum-well lasers grown by chemical beam epitaxy
Authors: Tsang W. T. , Choa F. S. , Wu M. C. , Chen Y. K. , Logan R. A. , Tanbun-Ek T. , Chu S. N. G. , Tai K. , Sergent A. M. , Wecht K. W.
Published: July 2002

We demonstrated the first successful growth of 1.5 μm strained-layer InGaAs/InGaAsP multi-quantum-well (MQW) distributed feedback (DFB) lasers by chemical beam epitaxy (CBE). In these DFB wafers, a quaternary grating is placed at the bottom of the MQW stack with an InP spacer layer. Studies by transmission electron microscopy show that defect-free InP regrowth was achieved with no mass transport needed over the grating corrugations before regrowth. With CBE regrowth the shapes of the gratings were well preserved. The InP overlayer also very effectively smoothed out the quaternary surface corrugations resulting in very flat MQW structures. Buried-heterostructure 6-QW DFB lasers (250 μm long and as-cleaved) operated at 1.55 μm with cw threshold currents 10–15 mA and slope efficiencies up to 0.35 mW/mA (both facets). Side-mode suppression ratios (SMSR) as high as 49 dB was obtained. The laser operated in the same DFB mode with SMSR staying above 40 dB from threshold and throughout the entire current range even at high temperatures (70 °C checked).
Narrow linewidth, continuously tunable semiconductor lasers based on quantum well gain lever
Authors: Lau Kam Y.
Published: July 2002

The tradeoff between linewidth and tuning range for multisection distribution Bragg reflector lasers is studied. It is shown that the quantum well gain-lever effect can be utilized in removing some of the tradeoff constraints, thereby making possible a broadly and continuously tunable semiconductor laser which can maintain a narrow linewidth over its tuning range.
Method for predicting microsegregation-free solidification with application to Ag-Cu alloys
Authors: Yankov E. Y. , Yankova M. I. , Copley S. M. , Todd J. A.
Published: July 2002

Melting the surface of Ag-Cu specimens with a laser or electron beam produces a variety of microstructures, the most interesting being a banded structure. In this letter we present a method, based on the interface response functions for solidification developed by Aziz and Kaplan [Acta Metall. 36, 2335 (1988)], for calculating the scanning velocity of the beam needed to bypass the banded structure and solidify the alloy in a microsegregation-free manner. When this velocity has been determined experimentally, as in the present Ag-Cu system, the width of the solid-liquid interface can be estimated.
Optical detection of light- and heavy-hole resonant tunneling in p-type resonant tunneling structures
Authors: Van Hoof C. , Borghs G. , Goovaerts E.
Published: July 2002

Photoluminescence of operational AlAs-GaAs-AlAs double-barrier resonant tunneling structures with p-type contact layers reveals the charging and subsequent discharging of the hole subbands in the quantum well by sequential resonant tunneling throughout the region of the first three hole resonances. The linewidth of the quantum well luminescence shows free-carrier broadening at each of the resonances. Accumulation and tunneling of photocreated electrons are also prominent.
Copper indium diselenide based thin-film transistors
Authors: Lai J. , Cai L. , Morel D. L.
Published: July 2002

Thin-film transistors have been fabricated with the compound semiconductor CuInSe2. The fabrication process uses soda-lime glass substrates and deposition conditions for CuInSe2 which result in near-intrinsic material. The devices are of the insulated-gate field-effect transistor configuration and operate in both p- and n-channel modes. Effective mobilities of 3.4 and 13 cm2/V s were measured for holes and electrons, respectively, indicating high potential for use of the technology in display applications.
Vibrational modes of carbon-aluminum complexes in AlxGa1−xAs grown by metalorganic molecular beam epitaxy
Authors: Ono Haruhiko , Furuhata Naoki
Published: July 2002

We investigated the effect of Al atoms on the localized vibrational mode (LVM) due to C in heavily C-doped AlGaAs grown by metalorganic molecular beam epitaxy (MOMBE). Several satellite peaks were observed in the range between 550 and 650 cm−1, instead of the C LVM at 583 cm−1, which has fine structure caused by Ga isotopes. We conclude these satellite peaks are due to C atoms perturbed by the surrounding Al atoms. Also, the C fine structure was not observed in heavily C-doped GaAs grown by MOMBE. We further conclude that the C fine structure cannot be observed in heavily C-doped AlGaAs because of strong perturbation from the surrounding Al and C atoms.
Anomalous electrical behavior related to the formation of TeAsV−Ga defect complexes in laser mixed Au/Te/Au/GaAs structures
Authors: Wuyts K. , Watté J. , Silverans R. E. , Van Hove M. , Van Rossum M.
Published: July 2002

The ohmic contact formation mechanism in pulsed laser beam mixed Au/Te/Au/GaAs structures has been investigated by 129I Mössbauer spectroscopy. Low-resistance, ohmic contact structures, on both n- and p-type GaAs, were found to be correlated to the formation of a high density of defect complexes consisting of tellurium atoms quasi-substitutional on arsenic sites with a gallium vacancy in the first neighbor shell. Correspondingly, the ohmic conduction is suggested to occur according to the amorphous heterojunction model, i.e., by a multi-step recombination-tunneling process.
Flexible and superconducting properties of sintered Bi-Pb-Sr-Ca-Cu-O tapes
Authors: Chen K. , Horng L. , Koo H. S. , Shei C. Y. , Wang L. P. , Chiang C. , Yang T. J. , Lee W. H. , Wu P. T.
Published: July 2002

Flexible Bi1.81Pb0.43Sr1.71Ca2.14Cu3Ox superconducting tapes have been fabricated by the powder-in-silver tubing technique followed by appropriate sintering. The sintered tape, Jc≳104 A/cm2 at 77 K, can be bent into an arc with a 0.9-cm radius of curvature without deteriorating the transport properties at liquid nitrogen temperature. This indicates that the superconducting a-b plane of the Bi-based tape has a strain of 0.05%–0.1%.
Optical modulation characteristics of a twin-guide laser by an electric field
Authors: Yamamoto E. , Hamada M. , Suda K. , Nogiwa S. , Oki T.
Published: July 2002

The characteristics for a twin-guide (TG) laser modulated by a reverse bias are studied for the first time. The extinction ratio and the wavelength shift are 20 dB with only 1 V bias and −0.4 nm, respectively. Further, the characteristics of a TG modulator itself (that has the same structure as the TG laser) are measured under a driving current lower than the threshold. The possibility of integrating a TG modulator with a tunable twin-guide (TTG) laser is presented.
Flexoelectrically controlled surface bistable switching in nematic liquid crystals
Authors: Barberi R. , Giocondo M. , Durand G.
Published: July 2002

A new bistable surface switching device using nematic liquid crystals in bookshelflike geometry is presented. The surface bistability is controlled by an external pulsed electric field of defined polarity, which breaks the surface anchoring and selects the final state from dielectric and flexoelectric couplings. A writing time of 32 μs and an optical response time of 300 μs are achieved, for a field of 18 V across a 1 μm thick cell. This simple nematic optical device presents properties directly comparable with those of ferroelectric liquid crystals displays: bistability, sharp threshold, fast address time.
Broadly tunable InGaAsP/InP buried rib waveguide vertical coupler filter
Authors: Alferness R. C. , Buhl L. L. , Koren U. , Miller B. I. , Young M. G. , Koch T. L. , Burrus C. A. , Raybon G.
Published: July 2002

We report the first demonstration of broadly electrically tunable (215 Å), narrow-band (∼20 Å full width at half maximum), wavelength selective, grating-assisted coupling between vertically stacked buried rib InGaAsP/InP channel waveguides. This current injection tuned device is suitable for integration in a variety of photonic devices and integrated circuits including broadly tunable extended cavity lasers, amplifier/filter, and demultiplexer/detector circuits.
New crucible made of Y2O3 for preparing yttrium based high T
c superconducting films by molecular beam epitaxy
Authors: Wang H. S. , Eissler D. , Kershaw Y. , Dietsche W. , Fischer A. , Ploog K. , Brunner D.
Published: July 2002

A new kind of crucible made of Y2O3 has been used for the first time to evaporate yttrium for the preparation of YBa2Cu3O7−y films by MBE. Problems related to the purity and thermal stability of the crucible and the evaporating stability of yttrium were investigated. The results imply that this crucible can be used for yttrium evaporation. Purity was high and the evaporating stability was good in spite of some interdiffusion and reaction between Y and Y2O3. YBa2Cu3O7−y films with Tcon of 77 K and Tco of 52 K have been obtained in situ using this crucible.
Growth of strained InAs/InP quantum wells by molecular beam epitaxy
Authors: Hopkinson M. , David J. P. R. , Claxton P. A. , Kightley P.
Published: July 2002

InAs/InP compressively strained quantum well structures with well thicknesses (LZ) 5 to 53 Å have been grown by solid source molecular beam epitaxy. Relatively sharp, intense, photoluminescence (PL) is observed over the wavelength range 1.1–2.05 μm at 10 K, with linewidths as narrow as 14 meV for a 30 Å well. Quantum confinement results in a shift of PL peak position of 130–710 meV with respect to the band gap of bulk strained InAs. The shifts are consistent with a conduction band offset (ΔEc) of 40%. At 300 K the wavelength range is extended to 2.23 μm, a value which to our knowledge is the longest wavelength reported for InAs/InP quantum wells. The high quality of pseudomorphic structures with well thicknesses exceeding estimates of critical layer thickness is demonstrated by transmission electron microscopy studies.
Direct measurement of the transparency current and valence band effective masses in tensile and compressively strained InGaAs/InP multiple quantum-well laser amplifiers
Authors: Tiemeijer L. F. , Thijs P. J. A. , Binsma J. J. M. , Dongen T. V.
Published: July 2002

Transparency current densities of 250 and 160 A/cm2 per well at the bandgap wavelength are reported for compressively and tensile strained multi quantum-well laser amplifiers. A strong wavelength dependence of the transparency current is found, due to level broadening, which shows that the threshold current of a quantum-well laser is inherently loss limited, rather than transparency limited. The spectral and polarizational dependence of the gain is measured and analyzed. From this it is concluded that the compressively (1.8%) and tensile (1.6%) strained quantum-well laser amplifiers exhibit valence band effective masses of 0.07 m0 and 0.1 m0, respectively, which shows that they both have a nearly symmetric band structure.
Evidence for an As4 sticking coefficient ≳0.5 in the molecular beam epitaxy of GaAs
Authors: Webb C. , Liu D. , Eckstein J. N.
Published: July 2002

Since the early work of Foxon and Joyce [Surf. Sci. 50, 434 (1975)] it has been accepted that the maximum sticking coefficient for As4 on GaAs in MBE growth is 0.5. Our results, based upon dc photoemission behavior and oscillations both in RHEED and photoemission, call into question this assumption and suggest that it is possible to observe near unity sticking coefficients provided the nucleation of Ga droplets has not occurred.
Plasma soft x-ray source generated by 4-ns excimer laser pulses
Authors: Morsell A. L. , Powers M. , Shields H.
Published: July 2002

A XeCl excimer laser system is described which generates short-duration (4 ns) pulses of up to 980 mJ in energy. Pulses of 800 mJ have been focused to an intensity of ∼2×1012 W cm−2 on an iron target to produce soft x rays. Measurements of x rays in the 0.8–1.4-keV range have demonstrated 44 mJ energy per pulse into 2π sr, and a pulse width of 5.3 ns (FWHM). The estimated laser to x-ray energy conversion efficiency was ∼5.5%.
Heavy arsenic doping of silicon grown by atmospheric-pressure chemical vapor deposition at low temperatures
Authors: Agnello P. D. , Sedgwick T. O. , Goorsky M. S. , Cotte J.
Published: July 2002

Arsenic doping of epitaxial grown Si over the temperature range from 850 °C to 550 °C was investigated in an ultraclean atmospheric-pressure chemical vapor deposition reactor. Growth was carried out from dichlorosilane (DCS) in H2 carrier gas. Arsenic could be incorporated into single crystal silicon at levels approaching 10 at. %. Carrier concentrations exceeding 1×1020/cm3 were obtained for the as-grown films. The material remained single-crystalline, as measured by ion channeling and cross-section transmission electron microscopy, and exhibited excellent surface morphology with no Hillock formation observed. AsH3 dramatically enhanced the growth rate of Si at lower temperatures.
Pulse fluctuation statistics of an actively mode-locked external-cavity semiconductor laser
Authors: Hsu Kevin , Verber Carl M. , Roy Rajarshi
Published: July 2002

The pulse amplitude fluctuation statistics of the picosecond pulses generated by active mode locking of an external-cavity semiconductor laser are measured experimentally. A comparison is made with predictions from a stochastic mode-locking model, which includes the effects of the spontaneous emission noise and carrier shot noise. Reasonable agreement is obtained for the dependence of the average peak pulse power and the standard deviation of pulse amplitude fluctuations on the bias current.
Selection of solutes for improving electromigration resistance of metals: A new insight
Authors: Small M. B. , Smith D. A.
Published: July 2002

There has long been as much art as science for choosing solute elements to improve the resistance to electromigration of metals such as aluminum. Alloying additions have been selected with the intention of maximizing the degree of segregation to the grain boundaries, exploiting differences in atom size to limit the grain-boundary excess volume, and forming grain-boundary precipitates which potentially can act as reservoirs of solute or as internal diffusion barriers. We show, using published data concerning the performance of a number of Al alloys measured under similar conditions, that the above strategies do not provide a direct correlation with lifetime. A further necessary condition for an addition which forms a precipitate in a eutectic system is its ability to dissolve into the grain boundary to replenish material driven away by electromigration. In peritectic systems, significant supersaturation can exist in the grains, and the grain boundaries. Equilibration of such systems decreases their effectiveness. In such systems, grains rather than precipitates can act as reservoirs.
Maskless growth of InP stripes on patterned Si (001): Defect reduction and improvement of optical properties
Authors: Grundmann M. , Krost A. , Bimberg D. , Ehrmann O. , Cerva H.
Published: July 2002

Metalorganic vapor phase epitaxy of InP stripes on narrow Si (001) stripes of widths down to 0.6 μm, oriented along 〈110〉, bound by V-grooves with {111}-sidewalls is studied. If the InP-stripe width is smaller than ≊4.5 μm, a complete suppression of APDs occurs. In addition, stacking faults are found not to terminate at the (001) InP surface but on {111} side planes. A smoother surface morphology and an increase of quantum efficiency by a factor 1.5–2 result. The thermal strain is observed to be partly relieved with decreasing stripe width. Lateral strain and band-gap homogeneity is directly imaged using cathodoluminescence. Si incorporation into the InP-layers is low and of the order of 1016 cm−3.
Pressure dependence of energy gap for Cd0.7Hg0.3Te
Authors: Jiang S. , Shen S. C. , Li D. , Ju Y. Q. , Zhu Haorong , Schilz J.
Published: July 2002

The absorption edge of CdxHg1−xTe with x=0.7 has been measured in the range of 0–36 kbar. A least-square fitting to the experimental data gives a pressure coefficient of a=8.7×10−3 eV/kbar, which is in good agreement with the result of dielectric theory of chemical bond. The second-order pressure coefficient of the energy gap is also obtained experimentally to be b=−6.3×10−5 eV/kbar2, which is anomalously large and difficult to understand. In addition, a structural phase transition has been observed under 34–36 kbar.
Second quantized state oscillation and wavelength switching in strained-layer multiquantum-well lasers
Authors: Chen T. R. , Zhuang Yuhua , Xu Y. J. , Zhao B. , Yariv A. , Ungar J. , Oh Se
Published: July 2002

The dependence of lasing wavelength on cavity length has been systemically studied in strained-layer single, double, and triple quantum-well InGaAs lasers. Lasing from the second quantized state has been observed for the first time in double and triple quantum-well lasers. A wide range (∼500 Å) wavelength switching between the first and second quantized states has been demonstrated by controlling the injection current and/or the operation temperature.
Improvement of the probe profiling method for InP/GaInAsP structures using Kr+ ion bombardment
Authors: Walachová J.
Published: July 2002

An improvement of the resolution of the probe profiling method based on low energy Kr+ ion bombardment of a beveled sample is demonstrated for two multiwell-barrier structures. The materials used are InP, GaInAsP (λ=1.3 μm) and GaInAsP (λ=1.1 μm). The limit of resolution of the method is discussed.
Enhanced nucleation and growth of diamond on SiC by plasma enhanced chemical vapor deposition using thin metal films
Authors: Yehoda J. E. , Fuentes R. I. , Tsang J. C. , Whitehair S. J. , Guarnieri C. R. , Cuomo J. J.
Published: July 2002

Presented is a method for growing crystalline diamond films by plasma enhanced chemical vapor deposition without the need for seeding with diamond particles. Instead, diamond nucleation and growth is ‘‘catalyzed’’ by a thin metal film which has been either abraded or deposited onto a SiC coated substrate. In the first experiment Fe, Cu, Ti, Nb, Mo, and Ni were abraded onto a SiC surface resulting in varying degrees of diamond nucleation and growth. In the second experiment, Fe films with thickness varying from 5 to 80 Å were evaporated onto the SiC. Although the 5 Å Fe film did not influence the initial nucleation and growth rate, greater thicknesses did. Preliminary studies of Fe on Si have not shown this effect.
Electron drift mobility measurements on annealed and light-soaked hydrogenated amorphous silicon
Authors: Wang Qi , Antoniadis Homer , Schiff E. A.
Published: July 2002

We measured the effects of light soaking on the electron drift mobility for three specimens of hydrogenated amorphous silicon (a-Si:H) from different laboratories. The temperature range 130–300 K was studied. The measurements in all cases reveal two temporal regimes: an early time regime associated with bandtail transport, and a later-time regime associated with deep trapping of the electrons. We found no evidence for effects of light soaking on the bandtail regime within a reproducibility error of 20%. Deep trapping was significantly affected by light soaking, in agreement with extensive prior measurements.
Synthesis of CuO films using mass-separated, low-energy O+ ion beams
Authors: Kita R. , Hase T. , Itti R. , Sasaki M. , Morishita T. , Tanaka S.
Published: July 2002

For the first time, CuO thin films have been synthesized by means of low-energy and high-density O+-ion beams, mass separated from an oxygen plasma. A 50-eV, 47-μA/cm2 O+-ion beam has successfully produced CuO at a growth rate of 0.04 Å/s by simultaneous deposition of Cu metal on MgO(100). O+ beams have greater potential for oxidation than O2 gas from the viewpoint of the flux necessary to form CuO.
Increased modulation depth of submicron gratings produced by photoelectrochemical etching of GaAs
Authors: Twyford E. J. , Kohl P. A. , Jokerst N. M. , Hartman N. F.
Published: July 2002

Submicron optical diffraction gratings with improved modulation depth were photoelectrochemically etched on n-GaAs. This etching technique uses an elevated etchant temperature to exceed the spatial resolution limits imposed by etching at room temperature, and provides a method of photoelectrochemical etching of gratings whose period is shorter than those of previously reported photoelectrochemically etched gratings. The improved grating modulation depth, the result of an increase in electrolyte temperature, was experimentally measured by etching 0.28 μm period gratings at five different temperatures. These results are compared with theoretical predictions based on analytical expressions for the reaction rate at the etched surface. Experimentally, a 25 °C increase in the etching temperature improved the grating amplitude by a factor of 1.7, which is in agreement with the theoretical predictions.
X-ray diffraction study of annealed ZnSe/GaAs superlattices
Authors: Zhang S. , Kobayashi N.
Published: July 2002

We investigate the effect of annealing on the structural properties of ZnSe/GaAs superlattices by the x-ray double-crystal rocking-curve technique. A 6-period ZnSe/GaAs superlattice with 61-nm thick ZnSe layers and 6-nm thick GaAs layers is grown by a combination of migration-enhanced epitaxy and solid-phase epitaxy. X-ray diffraction is measured for the ZnSe/GaAs superlattice samples annealed at different temperatures for several annealing periods in flowing H2 gas. From the change in the (004) and (115) rocking-curve profiles with increasing annealing temperature and annealing period, it was found that about 25% of the parallel strain in the ZnSe layers is relieved by misfit dislocations after annealing at 520 °C for 20 min. The interface properties of the annealed ZnSe/GaAs superlattices are also examined by computer simulation of kinematical diffraction.
Diamond growth by a new method based upon sequential exposure to atomic carbon and hydrogen
Authors: Kelly Michael A. , Olson Darin S. , Kapoor Sanjiv , Hagstrom Stig B.
Published: July 2002

We report growing high-quality diamond films by alternately exposing a substrate to a source of sputtered carbon atoms and one emitting atomic hydrogen in a new type of chemical vapor deposition reactor. The reactor is described, and two examples of films grown in it are shown. The implications of being able to grow diamond by a sequential process, and from the simple constituents of atomic carbon and hydrogen, are discussed.
Superconducting ceramics of Bi2Sr2Ca1Cu2Ox prepared by heating in a vacuum-sealed vessel
Authors: Abe Yoshihiro , Hosono Hideo , Lee Won-Hyuk , Kasuga Toshihiro
Published: July 2002

Superconducting ceramics in the Bi-Sr-Ca-Cu-O system have so far been prepared by heating in air or oxygen-containing atmosphere, but not in oxygen-free atmosphere such as vacuum or inert gas atmosphere. No one has reported converting the precursor (nonsuperconducting) ceramics sealed in an evacuated metal or glass pipe into superconducting ceramics. Metal or glass coated high Tc superconducting ceramics are in a great and strong demand for industrial uses; the coating is essential for protecting the ceramics for mechanical and chemical damage. We have found that as-cast specimens of the Ag2O-doped Bi2Sr2Ca1Cu2Ox melt prepared in air exhibit superconductivity (Tc≊85 K) after heat treatment in an evacuated and sealed silica glass tube. This finding indicates we are able to fabricate a desired shape of superconducting Bi2Sr2Ca1Cu2Ox ceramic sealed in glasses.