bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast ion imaging with a pinhole camera in laser-produced plasmas
Authors: Decoste R. , Kieffer J. C. , Pascale D. , Pepin H.
Published: February 2003

Fast ion imaging with a pinhole camera is shown to be quite reliable provided the camera parameters are correctly chosen. Space-charge expansion of the ion beam beyond the pinhole can be minimized by adjusting the ion energy filtration, the camera magnification, and the target-to-pinhole distance. Scaling of space-charge effects with the camera dimensions is discussed. Two experimental technqiues are also demonstrated to verify in situ the spatial resolution at the image plane.
Observation of lines above 2000 Å in O VIII and C VI in the Princeton Large Torus due to charge-exchange processes: Diagnostic applications
Authors: Suckewer S. , Skinner C. H. , Stratton B. , Bell R. , Cavallo A. , Hosea J. , Hwang D. , Schilling G.
Published: February 2003

Hydrogenlike oxygen and carbon lines from transitions (Δn=1) between levels of high principal quantum number n, with wavelengths above 2000 Å have been observed. Observations of such transitions were possible due to charge-exchange processes during neutral beam injection of hydrogen atoms into the Princeton Large Torus tokamak. The lines are O VIII 2976 Å (8–7 transitions), C VI 3434 Å (7–6), and C VI 5291 Å (8–7). Application of these lines for ion temperature measurements and initial observations of neutral beam vertical distributions in the plasma are presented.
Ultrafast laser-induced oxidation of silicon: A new approach towards high quality, low-temperature, patterned SiO2 formation
Authors: Orlowski T. E. , Richter H.
Published: February 2003

A new low-temperature method of rapidly forming (>100 Å/s) high quality patterned silicon dioxide (SiO2) layers on silicon substrates is presented. Ultraviolet pulsed laser excitation in an oxygen environment is utilized. Infrared absorption measurements indicate that the laser grown oxide is stoichiometric but with a higher degree of disorder than thermally grown oxide. From capacitance-voltage measurements we deduce a fixed oxide charge near the Si-SiO2 interface of 6×1010/cm2 for oxides that have been thermally annealed following the laser induced growth making this material a candidate for applications in semiconductor devices.
Fundamental considerations of the efficiency of amorphous solar cells
Authors: Hack M. , Guha S.
Published: February 2003

Using a computer simulation, we have calculated the dependence of efficiency of both single junction and tandem amorphous solar cells on the band gap of the active layers. We have also developed a simple expression to relate the open-circuit voltage of an amorphous solar cell to the ratio of the photoconductivity to dark conductivity of the intrinsic layer. This provides a powerful diagnostic tool for the evaluation of low band-gap amorphous materials.
Method for determining emitter recombination in Si solar cells using open-circuit voltage decay
Authors: Rose B. H. , Weaver H. T.
Published: February 2003

A method for determining the emitter recombination current and thereby partitioning the total carrier recombination current into the different sections of a silicon solar cell is demonstrated. The method is destructive, requiring that a set of measurements is made on a cell before and after mechanically roughening the back of the cell. The data include short-circuit current (Jsc), open-circuit voltage (Voc), and asymptotic decay rates for Jsc and Voc. High open-circuit voltage (650 mV) silicon cells are studied using the technique. It is shown that the emitter recombination current is large (1.5×10−13 A/cm2), which is consistent with a band-gap narrowing mechanism. Furthermore, the high voltages are shown to result from unusually long base lifetimes (>300 μs) in 0.3-Ω cm silicon.
Fabrication and characterization of GaAs Schottky barrier photodetectors for microwave fiber optic links
Authors: Blauvelt H. , Thurmond G. , Parsons J. , Lewis D. , Yen H.
Published: February 2003

High-Speed GaAs Schottky barrier photodiodes have been fabricated and characterized. These detectors have 3-dB bandwidths of 20 GHz and quantum efficiencies as high as 70%. The response of the detectors to light modulated at 1–18 GHz has been directly measured. Microwave modulated optical signals were obtained by using a LiNbO3 traveling wave modulator and by heterodyning two laser diodes.
Substrate effects on the threshold voltage of GaAs field-effect transistors
Authors: Winston H. V. , Hunter A. T. , Olsen H. M. , Bryan R. P. , Lee R. E.
Published: February 2003

An array of field-effect transistors fabricated by direct ion implantation on a liquid-encapsulated-Czochralski (LEC) In0.003Ga0.997As wafer exhibits greater uniformity of threshold voltage than arrays on similarly processed conventional LEC GaAs wafers. However, there is no correlation between a transistor’s threshold voltage and its proximity to a dislocation for either In-alloyed or conventional LEC GaAs substrates. An observed correlation of threshold voltage with local dislocation density for GaAs substrates can lead to the erroneous inference that threshold voltage is affected by dislocation proximity.
Optoelectrical properties of amorphous-crystalline silicon heterojunctions
Authors: Mimura Hidenori , Hatanaka Yoshinori
Published: February 2003

Optoelectrical properties of a heterojunction consisting of p-type hydrogenated amorphous silicon (a-Si:H) on n-type crystalline silicon (c-Si) have been investigated by measuring current–voltage and capacitance–voltage characteristics and the temperature dependence of the dark current. It was found that the hole injection from n-type c-Si into p-type a-Si:H depended mainly on control of the impurity concentration in a-Si:H doped with boron at the junction interface. The results obtained for the dark current and photocurrent (with 100 1×illumination) were 7.3 nA cm−2 and 41 μA cm−2, respectively, at an applied voltage of 5 V. These results hold promise for applications to a silicon vidicon target without a diode array.
Polar semiconductor quantum wells on nonpolar substrates: (Al,Ga)As/GaAs on (100)Ge
Authors: Masselink W. T. , Fischer R. , Klem J. , Henderson T. , Pearah P. , Morkoç H.
Published: February 2003

Optical properties of GaAs bulk layers and (Al,Ga)As/GaAs quantum wells with well sizes of 80, 100, and 200 Å have been studied. The structures were grown on (100) oriented Ga doped Ge substrates using molecular beam epitaxy. In contrast to earlier less successful attempts to grow polar semiconductors on nonpolar (100) substrates, the structures prepared in this study had good surface morphologies across the entire substrate and seemed relatively free of nonradiative traps. In bulk and quantum well structures, bound excition and donor-acceptor transitions were observed. The luminescent intensity at 2 K was comparable to that of similar structures grown on GaAs substrates and dominated by donor-acceptor (Ge0Ga-Ge0As) transitions. The ability to successfully grow polar semiconductors on (100) nonpolar semiconductors should provide many opportunities in hybrid and heterojunction device applications.
Change of the surface density of the midgap level (EL2 or EL0) in bulk GaAs by heat treatments with various capping
Authors: Hasegawa Fumio , Yamamoto Norio , Nannichi Yasuo
Published: February 2003

Change of the surface density of the midgap level (EL2 or EL0) in bulk GaAs by heat treatment was studied on horizontal Bridgman (HB) and liquid encapsulated Czochralski (LEC) grown GaAs by changing the capping materials (Si3N4, SiO2, GaAs) and the ambient (H2, vaccum). Decrease of the surface density of the midgap level was prevented on HB GaAs by capping with Si3N4, SiO2 or GaAs, whereas it could not on LEC GaAs when it is capped with Si3N4 or SiO2. Emission rates of the midgap level in LEC GaAs changed by the heat treatment but it did not for HB GaAs. These results support that the midgap levels in HB and LEC GaAs are due to different point defects (EL2 or EL0).
Fast diffusion of As in polycrystalline silicon during rapid thermal annealing
Authors: Wilson S. R. , Paulson W. M. , Gregory R. B. , Gressett J. D. , Hamdi A. H. , McDaniel F. D.
Published: February 2003

The diffusion of As in polycrystalline silicon films subjected to rapid thermal annealing has been studied using sheet resistance and Rutherford backscattering. The polycrystalline Si films were deposited on oxidized silicon wafers, implanted with As, and annealed with a Varian IA-200 isothermal annealer. Infrared radiation from a resistively heated sheet of graphite heats the wafer, in a vacuum, to temperatures >1000 °C for times on the order of a few seconds. The rate of diffusion and rate of loss of As from the polycrystalline Si is much faster than the diffusion rate and loss rate in single crystal Si annealed with identical conditions. Diffusion prior to grain growth agrees with previously reported results for As in polycrystalline Si. However, grain growth appears to enhance As diffusion.
Photon-assisted dry etching of GaAs
Authors: Brewer Peter , Halle Scott , Osgood R. M.
Published: February 2003

UV radiation from an ArF laser has been used to perform large-area etching of single-crystal GaAs. The process is based on photochemical production of methyl or trifluoromethyl, and bromine radicals. The etching is anisotropic and features <1 μm have been made.
Temperature-compensated bulk shear microwave resonators in LiTaO3
Authors: Krishnaswamy S. V. , McAvoy B. R.
Published: February 2003

Previous work on high overtone bulk longitudinal mode resonators in yittrium aluminum garnet has demonstrated loaded Q values in excess of 50 000 at frequencies near 2 GHz. These resonators are excited by sputtered ZnO thin-film transducers disposed on the substrate to provide a response in transmission. Herein we report the development of ZnO film shear mode transducers and their use in the excitation of temperature stable cuts of LiTaO3.
Excitation of the plasma waves in the laser beat wave accelerator
Authors: Tang C. M. , Sprangle P. , Sudan R. N.
Published: February 2003

The excitation of plasma waves by two laser beams, whose frequency difference is approximately the plasma frequency, is analyzed. Our nonlinear analysis is fully relativistic and includes mismatching of the laser beat frequency to the plasma frequency, time dependent laser amplitudes, and an applied transverse magnetic field (surfatron). For a given beat frequency, laser power, and plasma density, we find the peak accelerating electric field and its phase velocity. The transverse magnetic field is found to increase the effective plasma frequency, but has little effect on the plasma dynamics.
Weak-field measurements in crystals with low symmetry
Authors: Kyriakos D. S.
Published: February 2003

This letter concerns a generalization of the method presented in recent papers for the determination of the galvanomagnetic coefficients, especially those of magnetoresistance, for the case of crystals with low symmetry. The central idea is the search of one of the principal directions of the zero-field resistivity and the application of the Wasscher method for anisotropic materials in a circular flat sample containing the other two principal directions. The determination of the magnetoresistance coefficients is obtained by the peculiar influence of the magnetic field on the resistivity anisotropy leading to the magnetoresistance skewness effect.
Structural integrity of ion-implanted In0.2Ga0.8As/GaAs strained-layer superlattice
Authors: Arnold G. W. , Picraux S. T. , Peercy P. S. , Myers D. R. , Dawson L. R.
Published: February 2003

The strain and lattice disorder introduced by room temperature implantation (N, Si, Zn) into strained-layer superlattices (SLS) of In0.2Ga0.8As/ GaAs have been measured by cantilever-beam techniques and by channeled and random Rutherford backscattering spectrometry. These measurements indicate that a maximum lateral compressive stress of ∼5×109 dyn/cm2 is induced for all the ions at fluences corresponding to deposited energy densities of about 1020 keV/cm3 into collisional processes. The compositional modulation of the SLS is maintained at fluences which exceed the yield stress value even in the presence of additional implantation-induced stress and significant numbers of atomic displacements.
Non-registered silicon produced at a metal–silicon interface by 14 MeV oxygen ions
Authors: Headrick R. L. , Seiberling L. E.
Published: February 2003

Thin 〈110〉 silicon crystals were bombarded with 14 MeV oxygen ions in a transmission channeling geometry. The ions exited the crystals through a thin layer of Au or Ag, and scattered ions were detected at a glancing exit angle. Spectra were collected for each consecutive dose and analyzed to determine the number of disordered silicon atoms produced per dose. Disorder at the metal–silicon interface was observed that increased linearly with dose from 5×1015 to 5×1016 oxygen ions/cm2. Beam heating, and nuclear and electronic stopping power are discussed as possible sources of the disorder.
Carrier energy relaxation in In0.53Ga0.47As determined from picosecond luminescence studies
Authors: Kash Kathleen , Shah Jagdeep
Published: February 2003

We have measured the first infrared luminescence spectra of In0.53Ga0.47As with 10-ps time resolution. From the spectra we have obtained the carrier distribution functions at various delays for two different initial plasma densities. Our results provide a direct measurement of the carrier energy loss rate to the lattice, which we find to be about an order of magnitude slower than predicted from a simple model. We also find that the energy loss rate is surprisingly insensitive to carrier density at high densities.
Comparison of trapping levels in GaAsP strained-layer superlattice structures and in their buffer layers
Authors: Barnes C. E. , Biefeld R. M. , Zipperian T. E. , Osbourn G. C.
Published: February 2003

Deep level transient spectroscopy measurements have been performed on pn jucntions in a strained-layer superlattice (SLS) wafer composed of 240-Å-thick alternating layers of GaP and GaAs0.3P0.7 grown by metalorganic chemical vapor deposition. Comparison of these results with data taken on a standard alloy buffer layer of nearly the same average composition (18% As) reveals that in the SLS there are fewer types of traps, the trap concentrations are usually lower, the sample to sample variations across the wafer are much less, and the trap depth profiles are more uniform. Consequently, this comparison suggests that the SLS material is of better quality than the buffer which is mismatched to the underlying GaP substrate.
Fabrication of 20-nm structures in GaAs
Authors: Stern M. B. , Craighead H. G. , Liao P. F. , Mankiewich P. M.
Published: February 2003

Structures as small as 20 nm have been fabricated in GaAs by high-resolution electron beam lithography and reactive ion etching. NiCr patterns were formed on the semiconductor surface by liftoff of a single-layer electron beam resist. This metal mask pattern was transferred into the III-V material by etching in a SiCl4 plasma
630-mV open circuit voltage, 12% efficient n-Si liquid junction
Authors: Rosenbluth Mary L. , Lieber Charles M. , Lewis Nathan S.
Published: February 2003

We report the first experimental observation of a semiconductor/liquid junction whose open circuit voltage Voc is controlled by bulk diffusion/recombination processes. Variation in temperature, minority-carrier diffusion length, and/or in majority-carrier concentration produces changes in the Voc of the n-Si/CH3OH interface in accord with bulk recombination/diffusion theory. Under AM2 irradiation conditions, the extrapolated intercept at 0 K of Voc vs T plots yields activation energies for the dominant recombination process of 1.1–1.2 eV, in accord with the 1.12-eV band gap of Si. A crucial factor in achieving optimum performance of the n-Si/CH3OH interface is assigned to photoelectrochemical oxide formation, which passivates surface recombination sites at the n-Si/CH3OH interface and minimizes deleterious effects of pinning of the Fermi level at the Si/CH3OH junction. Controlled Si oxide growth, combined with optimization of bulk crystal parameters in accord with diffusion theory, is found to yield improved photoelectrode output parameters, with 12.0±1.5% AM2 efficiencies and AM1 Voc values of 632–640 mV for 0.2-Ω cm Si materials.
Photochemical etching of laser-induced defects in (Al,Ga)As heterostructures
Authors: Zysset B. , Salathé R. P.
Published: February 2003

Photochemical etching of laser-produced defect centers in n- and p-type Al(Ga,As) heterostructures has been investigated. In n-type (Al,Ga)As a decrease of etch rate in the processed zone is observed leading to etch hillocks whereas in p-type (Al,Ga)As a mesalike structure is formed: the center of the processed zone, 0.5 μm wide, shows the same etch rate as the unprocessed material whereas the adjacent regions, 10 μm wide, etch faster. From this etching behavior the following conclusions are made. (1) The laser processing introduces two different defects. Defect A is located in the center of the processed zone, defect B in the adjacent regions. (2) Type A defect is inactive in etching of p-type material. (3) Combined with luminescence data we assign for this center an energy level 100 meV above the valence band. (4) Defect B is a deep level located in the midgap region.
Metal-semiconductor junctions and amorphous-crystalline heterojunctions using B-doped hydrogenated amorphous silicon
Authors: Matsuura Hideharu , Matsuda Akihisa , Okushi Hideyo , Okuno Tetsuhiro , Tanaka Kazunobu
Published: February 2003

Investigated are the current-voltage characteristics of metal (Au, Mg)/B-doped hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (n+, p+) diodes for various doping levels of B in a-Si:H. From junction studies we determine the conduction type of B-doped a-Si:H on the basis of ‘‘dominant’’ carrier concentration, and find that the p-n transition occurs at B2H6/SiH4∼10−6 although the conductivity minimum appears at B2H6/SiH4∼10−4.
Application of ion implantation for doping of polyacetylene films
Authors: Koshida Nobuyoshi , Wachi Yoshio
Published: February 2003

Ion implantation for n-type doping of high-density (CH)x films was studied experimentally. Apparent doping effects were observed in those films implanted with relatively low-energy (12 keV) sodium ions. Current-voltage characteristics of a p-n junction produced between the implanted and original (p-type) regions in a film exhibited a rectifying behavior for over 37 days. The improved stability in air was also observed. Doping by ion implantation is potentially useful to increase the life span of (CH)x devices up to the point of practical use.
Localized density of states in amorphous silicon determined by electrophotography
Authors: Imagawa O. , Akiyama T. , Shimakawa K.
Published: February 2003

We report that the distribution of localized density of states g(E) for hydrogenated amorphous silicon can be estimated by the electrophotographic (xerographic) method. The density of states near midgap can be evaluated to be about 1×1016 cm−3 eV−1 for undoped films. The general trend and the shape of g(E) are similar to those obtained by the deep level transient spectroscopy and the photothermal deflection spectroscopy.
Photocapacitance spectroscopy of surface states on indium phosphide photoelectrodes
Authors: Goodman C. E. , Wessels B. W. , Ang P. G. P.
Published: February 2003

Indium phosphide photoelectrodes have been studied in situ using electrochemical photocapacitance spectroscopy. The observed photocapacitance spectra were a strong function of electrode surface conditions. The photoionization energies of the chemically induced surface states correlated well with previously reported values determined by surface photovoltage spectroscopy. The chemical treatment of the InP electrode surface with Co and Pt reduced the concentration of deep level interface states near the valence band and introduced a new state at Ev+1.2 eV.
Sputter deposited titanium disilicide at high substrate temperatures
Authors: Tanielian M. , Blackstone S. , Lajos R.
Published: February 2003

Titanium disilicide films were sputter deposited from a composite TiSi2.1 target on 〈111〉 bare silicon wafers both at room temperature and at 600 °C. The room temperature as-deposited films require a 900 °C sintering step to reduce their resistivity. On the other hand, the as-deposited 600 °C films are fully reacted, polycrystalline, have no oxygen contamination, large grain sizes, and are oxidation resistant. Further annealing of these films at 900 °C produces no changes in their crystal structure, composition, resistivity, or grain size.
16–21-μm line-tunable NH3 laser produced by two-step optical pumping
Authors: Morrison H. D. , Reid J. , Garside B. K.
Published: February 2003

A novel two-step optical pumping technique is described for creating line-tunable laser emission in the 2ν2–ν2 band of NH3. Two TE CO2 lasers operating on the R(30) and P(24) 9-μm transitions are used to pump the sR(5,0) and 2sR(4,3) NH3 transitions respectively, and lasing is observed on 11 different NH3 lines having wavelengths from 16 to 21 μm. This pumping technique relies on rapid rotational thermalization in the vibrational levels to enhance the pump absorptions and distribute the population inversion. The possibility of producing cw line-tunable operation on these transitions is discussed.
High-power, low-threshold, single-mode GaInAsP/InP laser by low-temperature, single-step liquid phase epitaxy
Authors: Horikawa H. , Imanaka K. , Matoba A. , Kawai Y. , Sakuta M.
Published: February 2003

A GaInAsP/InP laser (λg=1.3 μm) on grooved substrate with a lens-shaped active layer, in which the current blocking junction is grown exclusively outside of the groove, has been fabricated by single-step liquid phase epitaxy. This technique is based on the preferential growth effects of InP and GaInAsP on the (100) oriented substrate with [011̄] directed grooves. Under cw operation, low threshold current (38 mA), high output power (40 mW/facet), and high external differential quantum efficiency (56%) are accomplished; fundamental transverse mode operation up to an output of 30 mW/facet is verified. These successful characteristics are realized by the introduction of the inner current confining layer.
High-gain soft-x-ray-pumped photoionization laser in zinc vapor
Authors: Lundberg H. , Macklin J. J. , Silfvast W. T. , Wood O. R.
Published: February 2003

Large inversion densities in Zn+ have been produced by photoionizing inner-shell d electrons with the broadband soft-x-ray flux from a 1.06-μm laser-produced plasma. This pumping scheme is an effective technique for rapidly producing large population densities (5×1013 cm−3) in the 3d9 4s2 2D5/2 upper laser level. These large densities (a) produced laser action on a two-electron transition from the d-electron manifold to the outer-electron manifold at 7478 Å, (b) allowed the isotope shifts on this relatively weak transition to be measured, and (c) may eventually be transferred to other high lying states in Zn+ to produce vacuum ultraviolet lasers.
Effect of active layer placement on the threshold current of 1.3-μm InGaAsP etched mesa buried heterostructure lasers
Authors: Dutta N. K. , Nelson R. J. , Wilson R. B. , Maher D. M. , Wright P. D. , Sheng T. T. , Lin P. S. D. , Marcus R. B.
Published: February 2003

The threshold current of InGaAsP etched mesa buried heterostructure (EMBH) lasers is strongly influenced by the position of the active layer in the etched mesa. Transmission electron microscopy results are presented which show the presence of a thin planar disorder along the etched 111A interface. Nonradiative recombination of carriers is believed to be responsible for the increased threshold current of EMBH lasers whose active region is bounded by 111A interface. Lasers with threshold current as low as 14 mA at 30 °C have been fabricated by proper placement of the active layer and by optimizing layer thicknesses and doping levels.
Threshold analysis of cleaved-coupled-cavity lasers
Authors: Streifer William , Yevick David , Burnham Robert D. , Paoli Thomas L.
Published: February 2003

We present results of a cleaved-coupled-cavity laser analysis which, in contrast to previous studies, incorporates all the following: (1) a model of the gain variation with pumping current and photon energy; (2) the refractive index dependence on the active region injection current; and (3) traveling wave equations for each laser segment. Based on this realistic formulation, we solve for the precise current required by one segment to attain threshold when the current in the other segment is specified for various gap spacings between the segments, and show that device behavior is very sensitive to that dimension. In addition, we calculate quantitatively the spectral tuning and previously unreported jumps from one extreme of the gain spectrum to the opposite extreme in particular current ranges.
Passive mode locking of a XeCl laser
Authors: Efthimiopoulos T.
Published: February 2003

Passive mode locking of a 20-ns pulse duration XeCl laser was achieved. A modulation of 90% and less than 2-ns pulses are reported using Coumarin 1 and Auramine-0 dyes as saturable absorbers.
Enhancement of the specific output energy of an electron-beam pumped KrF laser by using Ne as the main buffer gas
Authors: Gerber T. , Peters P. J. M. , Bastiaens H. M. J. , Witteman W. J.
Published: February 2003

Optimization of a Ne/Ar/Kr/F2 gas mixture with respect to maximum KrF laser output has been performed. As an excitation source a transverse electron beam with a pulse length of 10 ns was used. The laser output obtained with a typical Ne/Ar/Kr/F2 mixture containing mainly Ne was found to increase linearly with Ne partial pressure. At a pressure of 14 bar the laser output energy exceeds the one achieved with an optimized Ar/Kr/F2 mixture by a factor of 4.5.
Theoretical evaluation of electron-beam-excited KrF lasers using argon-free mixtures of one atmosphere
Authors: Kannari Fumihiko , Suda Akira , Obara Minoru , Fujioka Tomoo
Published: February 2003

The output performance of the electron-beam-excited KrF laser operating at one atmosphere is theoretically analyzed because the KrF laser at one atmosphere can greatly reduce the design constraints on the large laser windows and the electron-beam pressure foils in a huge laser system as the inertial confinement fusion energy driver. The KrF laser using the atmospheric pressure, argon-free laser mixture is found to operate with an intrinsic laser efficiency as high as that of high-pressure, aregon-diluted mixtures. This is because three-body collisional quenching is not a detrimental energy-loss channel for the atmospheric pressure operation. By using higher excitation rate and shorter excitation pulse width pumping, higher intrinsic laser efficiency than conventional, argon-diluted, high-pressure mixtures is found to be attainable. Moreover, the specific laser energy (28 J/l, for 1-atm Kr/F2 mixtures pumped by an electron beam of 100 ns, 600 keV, and 150 A/cm2) is comparable to that of two-atm, argon-rich laser gas mixtures under the same excitation condition.
AlGaAs double-heterostructure diode lasers fabricated on a monolithic GaAs/Si substrate
Authors: Windhorn T. H. , Metze G. M. , Tsaur B-Y. , Fan John C. C.
Published: February 2003

AlGaAs double-heterostructure diode lasers have been fabricated for the first time on a monolithic GaAs/Si substrate. The heterostructure was prepared by growth of a series of GaAs and AlGaAs layers on a Ge-coated Si wafer. For pulsed operation at 77 K the lowest threshold current was 260 mA, the highest power output was 1.8 mW per facet, and the highest differential quantum efficiency was 1.2%.
Niobium films for superconducting accelerating cavities
Authors: Benvenuti C. , Circelli N. , Hauer M.
Published: February 2003

Superconducting accelerating cavities made of Nb-coated copper were produced. Niobium films of a thickness ranging from 1.4 to 4 μm were deposited onto the inside of 3-GHz cavities and 500-MHz frequency by bias diode sputtering. A maximum accelerating field of 8.6 MV m−1 was reached without quench which is attributed to the large thermal conductivity of copper at liquid helium temperatures.
Observation of magnetic domains with spin-polarized secondary electrons
Authors: Koike K. , Hayakawa K.
Published: February 2003

Magnetic domain structure on a silicon iron (001) surface has been observed using a new scanning electron microscope (SEM), in which image contrast was obtained by using spin polarization of secondary electrons. From this image and an absorption current image of the same area, it has been confirmed that the domain structure image is not influenced by surface morphology. This represents an improvement over conventional domain structure observation methods. This new SEM will be greatly improved also as for the resolving power compared to conventional reflection methods, when used in conjunction with a proper field emission gun.
AlF3—A new very high resolution electron beam resist
Authors: Muray A. , Isaacson M. , Adesida I.
Published: February 2003

Using dose resolved energy loss and energy filtered imaging, the mechanism of a new high resolution resist, AlF3, is examined. It is found that exposure induces mass loss including the displacement of Al ions. From the energy filtered images, it is observed that the Al coats the walls of the exposed area. Further, it is demonstrated that high resolution patterns exposed in AlF3 can be replicated into Si3N4 substrates.
Pulsed-laser generation of ultrashort acoustic pulses: Application for thin-film ultrasonic measurements
Authors: Tam A. C.
Published: February 2003

We demonstrate nondestructive optoacoustic generation and detection of acoustic pulses of 1-ns duration in condensed matter. Such optoacoustic pulses are at least one order of magnitude shorter than those previously reported. These narrow acoustic pulses find new application for thin-film pulse measurements, which are not possible with conventional transducer techniques. Round trip echo times are measured to 1% accuracy for stainless steel films of 12-μm thickness. This provides a new high accuracy thickness measurement in a pulsed mode. Ultrasonic attenuation for the narrow acoustic pulses is very large and is also measured.
Formation of titanium silicides by fast radiative processing
Authors: Wei C. S. , Van der Spiegel J. , Santiago J. J. , Seiberling L. E.
Published: February 2003

Titanium silicide films were grown under roughing vacuum on single crystal silicon wafers using high power quartz-halogen tungsten lamps to provide the thermal driving force. After processing for various time intervals, ranging from 5 to 25 s, the samples were characterized by measuring their sheet resistance. Major phases were detected with x-ray diffractometry. Elemental composition and film thickness were measured using Rutherford backscattering and Auger electron spectroscopy. These techniques consistently indicated that silicide formation was completed after 10–12 seconds processing time. The quality of these films and its potential usefulness are evidenced by their low resistivity of 21 μΩ cm.
Influence of high-temperature annealing on performance of edge-defined film-fed growth silicon ribbon solar cells
Authors: Kalejs J. P. , Ladd L. A.
Published: February 2003

Silicon ribbon with varying oxygen concentrations grown by the edge-defined film-fed growth technique has been annealed for periods of up to 1 h at 1200 °C prior to fabrication into solar cells. Low (<1×1016 atom/cc interstitial) oxygen content ribbon cell performance, which is characteristically depressed with respect to higher (∼5×1016 atom/cc interstitial) oxygen content ribbon, is improved by the anneal to levels approaching those observed in unannealed ribbon with the higher oxygen concentrations. The latter are essentially unaffected by the anneal. An explanation for ribbon cell property responses is proposed that is based on consideration of recombination effects associated with carbon microdefects.
Origin of hydrogen in amorphous silicon produced by glow discharge in Si2H6+D2 and Si2D6+H2
Authors: Kuboi Osamu , Hashimoto Masanori , Yatsurugi Yoshifumi , Nagai Hisao , Aratani Michi , Yanokura Minoru , Hayashi Shigeki , Kohno Isao , Nozaki Tadashi
Published: February 2003

Hydrogenated amorphous silicon was grown from disilane by rf glow discharge. Deuterium (D) was used as a tracer gas in this investigation, in which two gas mixtures (Si2H6+D2 and Si2D6+H2) were employed. Amorphous silicon so produced was analyzed for 1H and D by Rutherford recoil measurement to determine whether these elements came from disilane or dilution gas. When the rf power is low, a much larger proportion of hydrogen atoms in disilane (1H in case of Si2H6, D in case of Si2D6) than in the dilution gas is found in the amorphous silicon. The exact reverse is true as the rf power becomes large.
Up conversion of luminescence via deep centers in high purity GaAs and GaAlAs epitaxial layers
Authors: Quagliano Lucia G. , Nather Heinz
Published: February 2003

Up-converted band to band luminescence generated by photons with energy lower than the band gap has been observed in high purity GaAs and GaAlAs epitaxial layers as well as in undoped melt-grown GaAs. This is explained by assuming a two-step excitation process involving a deep center as intermediate state. Since ecah crystal investigated has shown this effect, we conclude that intrinsic defects in pure GaAs and GaAlAs crystals provide the deep levels necessary for the up conversion.
Interface state density measurements with a modified C-V technique
Authors: Gildenblat G. , Pimbley J. M. , Cote M. F.
Published: February 2003

Interface states in the metal-oxide-semiconductor (MOS) system have a great influence on the electrical properties of MOS capacitors and field-effect transistors. Several methods for measuring the density of these interface states within the forbidden band gap of silicon employ differential capacitance versus gate bias (C-V) measurement on MOS capacitors. We present here a C-V measurement technique utilizing the MOS transistor that extends the energy range of the high-low frequency method to that of the low-frequency technique.
Electro-optic hysteresis in polyvinylidene fluoride
Authors: Gookin D. , Morris R.
Published: February 2003

Electro-optic data for uniaxially drawn polyvinylidene fluoride are presented. Measurements at successively increasing fields show a hysteresis effect. The observed electro-optic hysteresis is compared with theoretical predictions of hysteresis in ferroelectric ceramics.
Graphoepitaxy of Ge on SiO2 by solid-state surface-energy-driven grain growth
Authors: Yonehara T. , Smith Henry I. , Thompson C. V. , Palmer J. E.
Published: February 2003

Solid-state surface-energy-driven grain growth in 30-nm-thick Ge films on SiO2, encapsulated with SiO2, produces a predominance of (110) crystallographic texture in secondary grains several micrometers in diameter. If the SiO2 substrate is patterned with a 0.2-μm period relief grating, ∼10 nm deep, with approximately square-wave profile, many of the secondary grains that form have (100) texture. These grains show a graphoepitaxial orientation with 〈100〉 directions preferentially parallel to the grating axis.
High mobility hole gas and valence-band offset in modulation-doped p-AlGaAs/GaAs heterojunctions
Authors: Wang W. I. , Mendez E. E. , Stern Frank
Published: February 2003

Modulation-doped p-AlGaAs/GaAs heterojunctions have been grown by molecular beam epitaxy. The effects of undoped AlGaAs spacer thickness on sheet carrier density and on Hall mobility have been investigated. A mobility of 97 000 cm2 V−1 s−1 has been obtained at 4.2 K for a sheet density of 1.7×1011 cm−2. This is the highest mobility reported for holes in III-V compound semiconductors. A valence-band offset of 210±30 meV was deduced for Al0.5Ga0.5As /GaAs heterojunctions.
Time-resolved and space-resolved Si lattice-temperature measurements during cw laser annealing of Si on sapphire
Authors: Murakami Kouichi , Tohmiya Yoshinori , Takita Kôki , Masuda Kohzoh
Published: February 2003

We have developed an optical technique for in situ measurement of temporal change and spacial profile of Si lattice temperature during cw laser annealing. This technique utilizes time-dependent optical interference in Si films on insulator. By using a microscope for focusing a laser probe beam to 2.0 μm, time-resolved and space-resolved Si lattice-temperatures were measured below the melting point (1412 °C) on a time scale of 10−4–100 s during cw laser annealing of Si on sapphire.
Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures
Authors: Wei H. P. , Tsui D. C. , Razeghi M.
Published: February 2003

A persistent photoconductivity is observed in the transport of the high mobility two-dimensional electron gas in In0.53Ga0.47 As/InP heterostructures. Low field Hall measurements from 300 to 4.2 K and the quantized Hall effect in the high field limit are studied with radiation from visible and infrared light-emitting diodes. Our results demonstrate conclusively that the effect is due to photogeneration of electron-hole pairs in the heterostructure and trapping of holes in the In0.53Ga0.47 As.
A universal trend in the binding energies of deep impurities in semiconductors
Authors: Caldas M. J. , Fazzio A. , Zunger Alex
Published: February 2003

Whereas the conventional practice of referring binding energies of deep donors and acceptors to the band edges of the host semiconductor does not produce transparent chemical trends when the same impurity is compared in different crystals, referring them to the vacuum level through the use of the photothreshold reveals a remarkable material invariance of the levels in III-V and II-VI semiconductors. It is shown that this is a consequence of the antibonding nature of the deep gap level with respect to the impurity atom-host orbital combinations.
Titanium disilicide formation by sputtering of titanium on heated silicon substrate
Authors: Tanielian M. , Blackstone S.
Published: February 2003

We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated
Time-resolved thermionic and photoemission from nanosecond, pulsed laser excited germanium and silicon
Authors: Leung T. L. F. , van Driel H. M.
Published: February 2003

We report electron emission from (111) surfaces of intrinsic crystalline Ge and Si using 25-ns laser pulses at λ=1.06, 0.53, 0.35, and 0.26 μm. For 0.26 and 0.35 μm, two-photon photoemission is observed, while for 0.53 and 1.06 μm only thermionic emission is obtained. In all cases the emission current follows the temporal profile of the laser pulse up to the melting point. Analysis of the thermionic data, taking account of the nonequilibrium carrier density, indicates that the electron temperature follows, but can be up to several hundred degrees higher than, the lattice temperature, during the laser pulse.
Raman study of polish-induced surface strain in 〈100〉 GaAs and InP
Authors: Shen H. , Pollak Fred H.
Published: February 2003

We report measurements of the first-order Raman spectra of the longitudinal optic phonon from 〈100〉 surfaces of GaAs and InP which have been polished by various procedures. Nondestructive depth profiling was accomplished by using the various excitation lines of an Ar+ laser. The resultant line shape changes have been quantitatively accounted for by a model based on the convolution of the penetration depth of the light and the skin depth of the polish-induced surface strain. We find the polish-induced surface strain to be compressive and about 4% in GaAs and 5% in InP, relatively independent of particle size. The strain skin depth is substantially less than the particle size although it does increase with increasing size and polishing time.
A criterion for the determination of upper critical fields in highly disordered thin-film superconductors
Authors: Paalanen M. A. , Hebard A. F.
Published: February 2003

A procedure is described by which the temperature-dependent upper critical field Hc2(T) in highly disordered thin-film superconductors with broad resistive transitions is determined. Resistance versus perpendicular magnetic field isotherms are used in conjunction with the mean field transition temperature Tc 0, derived from Aslamazov–Larkin fits to the zero-field resistive transition, to determine Hc2(T). The sensitivity of the slope parameter (dHc2/dT)‖Tc 0 with respect to the details of the procedure is discussed and the conditions under which meaningful comparisons with theory can be made are elaborated.
Threshold effect in Mg-doped lithium niobate
Authors: Sweeney K. L. , Halliburton L. E. , Bryan D. A. , Rice R. R. , Gerson Robert , Tomaschke H. E.
Published: February 2003

Optical absorption spectra were obtained after reducing (i.e., vacuum annealing) a series of LiNbO3 crystals grown from melts having various Mg concentrations and Li/Nb ratios. A band peaking at 500 nm, and assigned to oxygen vacancies containing two electrons, was the only absorption present in one set of crystals following reduction. In contrast, two overlapping bands peaking near 1200 and 760 nm were present in the other set of crystals immediately after the reduction. The 1200-nm band is assigned to a previously unreported electron trap and the 760-nm band to oxygen vacancies containing only one electron. These data are interpreted in terms of a threshold level for Mg doping; however, the threshold Mg doping level is not a constant but depends on the ratio of Mg ions to Li vacancies.
Picosecond luminescence measurements on fast GaAs Schottky diodes under changing circuit conditions
Authors: Von Lehmen A. , Ballantyne J. M.
Published: February 2003

Time-resolved luminescence measurements on a GaAs Schottky diode with a transit dimension of 0.3 μm yield pulse width limited decay times reflecting fast carrier sweepout. In addition, using the same all-optical technique, we have directly observed for the first time a slowing effect on transport in the device when monolithic inductors are introduced into the biasing circuit.
Single contact tailored gain phased array of semiconductor lasers
Authors: Lindsey C. P. , Kapon E. , Katz J. , Margalit S. , Yariv A.
Published: February 2003

We demonstrate a single contact tailored gain-guided array in which the gain profile across the array is made strongly asymmetric by varying the width of the contact stripes. A proton isolated array of six (GaAl)As lasers with 5-μm separations and widths varying linearly between 3 and 8 μm had a single lobed far field 2° wide, close to the diffraction limit for a single supermode. Fabrication of this device is simple, and suited to large-scale processing techniques. We also show that in such an asymmetric gain-guided array the fundamental mode is favored over higher order modes, and that higher order modes can have single lobed far-field patterns differing only slightly from that of the fundamental.
Vacuum ultraviolet light transmission through hollow-core quartz-glass cladding optical fibers
Authors: Watanabe M. , Hidaka T. , Tanino H. , Hoh K. , Mitsuhashi Y.
Published: February 2003

This letter presents the first demonstration of vacuum ultraviolet light transmission using a flexible fiber. Synchrotron radiation having a peak wavelength of about 30 Å successfully traversed the fiber and exposed electron beam resist films of polytrifluoroethyl α-chloroacrylate and polymethyl methacrylate.
Single-longitudinal-mode stabilized graded-index-rod external coupled-cavity laser
Authors: Liou K-Y. , Burrus C. A. , Linke R. A. , Kaminow I. P. , Granlund S. W. , Swan C. B. , Besomi P.
Published: February 2003

An active-passive coupled-cavity semiconductor laser using a slightly shorter than 1/4 pitch graded-index-rod lens reflector as the external cavity has been demonstrated. The graded-index lens is prepared from an optical fiber waveguide. We report (1) stable single-longitudinal-mode operation of the graded-index-rod external coupled-cavity (GRECC) lasers with 2-Gbits/s modulation and (2) digital transmission at 1 Gbits/s over 99 km of fiber using a 1.55-μm GRECC laser.
Effects of carrier confinement in graded AlGaAs/GaAs heterojunctions
Authors: Yuan Y. R. , Mohammed K. , Pudensi M. A. A. , Merz James L.
Published: February 2003

An unusual new line has been observed in the 1.4-K photoluminescence spectrum of GaAs/AlGaAs epilayers grown by liquid phase epitaxy. A very strong, broad, and asymmetric line is seen, with peak energy ranging from the bound exciton to the shallowest acceptor, increasing roughly linearly with the logarithm of the excitation power. By employing a novel step-etching technique, this transition is shown to originate from the GaAs/AlGaAs heterojunction. A qualitative model is proposed to explain the observed data.
n-CuInSe2 based photoelectrochemical cells: Improved, stable performance in aqueous polyiodide through rational surface and solution modifications
Authors: Cahen David , Chen Yih-Wen
Published: February 2003

Surface optimization of n-CuInSe2 crystals by chemical etching in Br2/MeOH and subsequent thermal oxidation results in >10% efficient photanodes in neutral aqueous polyiodide. The etchant removes a near-stoichiometric surface layer and thermal oxidation leads to In–O bond formation. We find from (photo) electrochemical studies in acetonitrile and in the iodide electrolyte that, upon semiconductor decomposition, Cu ions are released into the solution, consistent with solid state chemical studies that show the existence of the chalcopyrite phase also towards Cu-poor compositions. Addition of Cu ions, as also reported by S. Menezes, H. J. Lewerenz, and K. J. Bachmann [Nature (London) 305, 615 (1983)] or Cu and In ions to the iodide solution drastically decreases photoanode decomposition. Covering the electrode with an extra film of oxidized indium results in true stabilization, at up to 11.7% conversion efficiency under 120-mW/cm2 tungsten-halogen illumination. Because, in the presence of Cu ions and under illumination, iodide solutions are not completely stable towards oxidation by O2, especially if the solution is acidic, an air-free electrolyte needs to be used.
High power coupled ridge waveguide semiconductor laser arrays
Authors: Twu Yihjye , Dienes A. , Wang Shyh , Whinnery J. R.
Published: February 2003

Using index-guided ridge waveguide structures, we have obtained single-lobe far-field pattern from coupled multiple-stripe semiconductor laser arrays. A stable far-field pattern has been observed up to 250-mW peak pulsed power. This desired performance of a semiconductor laser array is achieved by intentional pumping of a laser array at coupling regions, which is possible in ridge waveguide structures.
Real-time optical waveform convolver/cross correlator
Authors: Bai Y. S. , Babbitt W. R. , Carlson N. W. , Mossberg T. W.
Published: February 2003

We show that an inhomogeneously broadened sample, excited by a series of three resonant optical pulses, emits an optical signal whose electric field envelope closely approximates the convolution or cross correlation of the field envelopes belonging to two of the three excitation pulses. The convolution (cross correlation) function is obtained when the first (second) pulse in the excitation sequence is short compared to the temporal structure of the other two excitation pulses.