bluuebunny/crossref_metadata_2025 huggingface dataset:
High-efficiency TEM continuous-wave (Al,Ga)As epitaxial surface-emitting lasers and effect of half-wave periodic gain
Authors: Gourley P. L. , Brennan T. M. , Hammons B. E. , Corzine S. W. , Geels R. S. , Yan R. H. , Scott J. W. , Coldren L. A.
Published: July 2002

We report room-temperature, continuous-wave (cw), photopumped operation of (Al,Ga)As surface-emitting lasers grown by molecular beam epitaxy. These monolithic semiconductor lasers comprise two multilayer semiconductor mirrors surrounding a layered active region. In the active region, GaAs quantum wells are spaced with half-wave periodicity to center on standing-wave maxima of the cavity optical field. By comparing threshold data for different lasers grown with and without half-wave periodicity, we observe the first experimental evidence for reduced cw lasing threshold (as low as 2×104 W/cm2 ) with periodic gain in an epitaxial surface-emitting laser. Up to 50 mW with high efficiency (35% total, 80% differential) and narrow spectral linewidth (2 Å) have been measured. A very high quality beam with low divergence (2.5°) and circular TEM00 profile has been observed. All of these observations represent significant advances for surface-emitting laser technology.
GaAs/GaSb strained-layer heterostructures deposited by metalorganic vapor phase epitaxy
Authors: Chidley E. T. R. , Haywood S. K. , Mallard R. E. , Mason N. J. , Nicholas R. J. , Walker P. J. , Warburton R. J.
Published: July 2002

The growth of strained GaSb/GaAs quantum wells has been attempted for the first time (7% lattice mismatch), with the antimonide layers being constrained to take on the GaAs lattice parameter in the interface plane. The critical thickness for pseudomorphic growth of the strained layer was about 15 Å, with further growth resulting in islands of GaSb crystallites over the wafer surface. Photoluminescence spectra and photoconductivity from both single and double wells showed a strong signal at approximately 1.3 eV, identified as a Γ point transition. This was not consistent with band structure calculations for a GaSb/GaAs well, suggesting an error in the estimation of the band offsets and/or As incorporation in the strained layer.
Nonlinear optical phase conjugation using F+3 centers in LiF crystals
Authors: Gu Hongen , Qi Lan , Wan Liangfeng
Published: July 2002

We report the experimental observation of nonlinear optical phase conjugation using F+3 centers in LiF crystals. Using a pulsed dye laser (460 nm) as pump light, a maximum phase conjugate reflectivity of about 0.1% was obtained.
High-speed and high-gain optical amplifying photodetection in a semiconductor laser amplifier
Authors: Nakajima Hisao
Published: July 2002

A high-speed and high-gain photodetection was experimentally demonstrated in a distributed feedback semiconductor laser amplifier by detecting its forward voltage changes induced by the injection of weak intensity modulated light. Physical phenomenon involved in the photodetection stems from the reduction of quasi-Fermi level separation through the depletion of carrier density by optical amplification. A bandwidth as wide as 500 MHz was measured together with a narrowband spectral selectivity for the amplifier biased just below the lasing threshold. The responsivity and the noise equivalent power were found to be comparable with those of the conventional detection scheme using a similar optical preamplifier and a Ge avalanche photodetector.
Nonlinear Bragg reflector based on saturable absorption
Authors: Kim B. G. , Garmire E. , Hummel Steven G. , Dapkus P. D.
Published: July 2002

The first observation of nonlinear reflection from a Bragg reflector composed of Ga0.8 Al0.2As/AlAs layers due to the band filling effect was measured by the pump probe method. The nonlinearity was primarily due to saturable absorption. Optically induced reflectivity changes of as much as 38% were measured.
Resistance measurements on point-contact diodes
Authors: Riccius H. D. , Jones L. H.
Published: July 2002

Experiments have shown that the conductance of any point-contact diode consisting of a metal whisker in mechanical contact with either a metal, semimetal, or semiconductor is an integral multiple of 4.3×10−6 Ω−1, and depends only on the contact force applied.
Tunnel injection into a Wannier–Stark ladder
Authors: England P. , Helm M. , Hayes J. R. , Harbison J. P. , Colas E. , Florez L. T.
Published: July 2002

We describe tunneling measurements of the electronic states of superlattices in which an electric field has destroyed the miniband structure. The tunneling characteristics reveal that the minibands collapse into localized Wannier–Stark states, which can be resolved in the first two quantum wells of the superlattice. The positions can be accounted for quantitatively by a combination of electrostatic and quantum mechanical effects.
Hydrogen and oxygen content of silicon nitride films prepared by multipolar plasma-enhanced chemical vapor deposition
Authors: Boher Pierre , Renaud Monique , van IJzendoorn L. J. , Hily Yves
Published: July 2002

Very low H content SiN films have been deposited by a multipolar plasma-enhanced deposition system at room temperature. The main plasma parameters which control the hydrogen and oxygen incorporation in the films have also been analyzed and optimized.
Photoionization cross section of In0.49Ga0.51P:Fe
Authors: Takanohashi T. , Nakajima K.
Published: July 2002

We determined spectral dependence of the photoionization cross section of the Fe acceptor in In0.49Ga0.15P by photocapacitance spectroscopy. As a result of the alloy effect we observed the nonexponential photocapacitance transient. We treated it with a model of the energetically broadened defect level. Optical thresholds for 5E and 5T2 of the crystal-field-split Fe acceptor level are 0.78 and 1.15 eV at 77 K. The small difference of 40 meV between the optical and thermal activation energies for the transition from the valence band to 5E reveals the weak coupling between the Fe acceptor level and the lattice vibration of InGaP.
InGaAs/InAsP lasers with output wavelengths of 1.58–2.45 μm
Authors: Martinelli Ramon U. , Zamerowski Thomas J. , Longeway Paul A.
Published: July 2002

We have studied InxGa1−xAs/InAsyP1−y double-heterojunction oxide stripe lasers for 0.53≤x≤0.87 and y=2.13x−1.13. The output wavelengths at 80 K ranged from 1.58 μm for x=0.53 to 2.45 μm for x=0.87. The maximum temperature for pulsed operation extended from 210 K for the 2.45 μm lasers (x=0.87) to 315 K for the 1.58 μm lasers (x=0.53). The exponential increase of the pulsed threshold current with increasing temperature is greatest for the lasers with the longest wavelengths.
X-ray imaging of nanostructure patterns
Authors: Vladimirsky Y. , Kern D. , Meyer-Ilse W. , Attwood D.
Published: July 2002

A Fresnel zone plate lens, with a nominal outer zone width of 400 Å, has been used to image nanostructures with soft x-ray synchrotron radiation at 45 Å wavelength with the Göttingen x-ray microscope at BESSY in Berlin. The structures, consisting of gold lines in thin silicon nitride membranes, were selected for tests of spatial resolution and image forming capabilities. Several patterns associated with deep submicron electronic circuits were also imaged, showing clearly resolved features smaller than 0.1 μm. Images of periodic structures, including 600 Å lines on 2000 Å centers, suggest a spatial resolution approaching the theoretical limit of approximately 500 Å.
Integration of a diode laser and an electronic lens for controlling the beam focus position
Authors: Mukai S. , Watanabe M. , Itoh H. , Yajima H.
Published: July 2002

An electronic lens is developed for controlling the focus position of an optical beam without mechanical movement. The lens utilizes the dependence of the lateral index profile on carrier concentration profile in the waveguide layer. The lens is integrated with a diode laser by the cleave-couple technique, and the control of the focus position of the output beam of this device is demonstrated.
Nanometer scale wire structures fabricated by diffusion-induced selective disordering of a GaAs(AlGaAs) quantum well
Authors: Zarem Hal A. , Sercel Peter C. , Hoenk Michael E. , Lebens John A. , Vahala Kerry J.
Published: July 2002

A shallow zinc diffusion technique is used to selectively disorder a GaAs quantum well creating nanometer scale wire structures. Spectrally resolved cathodoluminescence images of the structures are presented as well as local spectra of cathodoluminescence emission from the structures. Blue shifting of the luminescence from the wire structures is observed.
Optoelectronic measurement of picosecond turn-on delay in InGaAsP laser diodes
Authors: Adomaitis E. , Blixt P. , Krotkus A.
Published: July 2002

A tandem photoconductive switch, producing nearly rectangular electrical pulses with variable duration from 25 ps to 1 ns, was used for accurate turn-on delay measurements of a laser diode. Maximum electrical pulse amplitude was 75 V and both rise and fall times were 15 ps. The shortest delay recorded was 60 ps. The carrier lifetime at the lasing threshold was found to be 3.89 ns.
Photoluminescence from CdTe/Hg1−yCdyTe/Hg1−xCdxTe separate confinement heterostructures
Authors: Mahavadi K. K. , Lange M. D. , Faurie J. P. , Nagle J.
Published: July 2002

We report the first observation of photoluminescence from CdTe/Hg1−yCdyTe/Hg1−xCdxTe (y>x) separate confinement heterostructures grown by molecular beam epitaxy. The spectral shape is determined by the band filling of electrons in the well which is due to a charge transfer effect. There is an appearance of high-energy transitions at high temperatures. The strong photoluminescence from the layer is highly promising for the observation of the laser action.
Properties of Bi(Pb)-Sr-Ca-Cu-O superconducting tapes prepared by the doctor-blade process
Authors: Yanagisawa E. , Morimoto T. , Dietderich D. R. , Kumakura H. , Togano K. , Maeda H.
Published: July 2002

Improved superconducting and mechanical properties were obtained for Bi(Pb)-Sr-Ca-Cu-O tapes, prepared by the combined process of doctor-blade casting, cold rolling, and sintering. The tape has an oriented microstructure with the high Tc plate-like grains having their c axes perpendicular to the rolling surface. The tape is flexible and can be bent without any degradation of Jc to just before fracture (strain larger than ∼0.12%).
Preparation and magnetic properties of Bi-Pb-Sr-Ca-Cu-O superconducting ceramics
Authors: Uzumaki Takuya , Yamanaka Kazunori , Kamehara Nobuo , Niwa Koichi
Published: July 2002

A high Tc phase (Tc ≂110 K) in Bi-Pb-Sr-Ca-Cu-O systems was synthesized by adding Ca2PbOx to the mixture of a low Tc phase (Tc ≂80 K) and a Bi-Sr-Cu-O (Tc ≂10 K). X-ray powder diffraction measurement suggests that the sintered bulk mainly consists of the high Tc phase. The volume fraction of the high Tc phase was 74% from the measurement of magnetization. The lower critical field Hc1 was 10 Oe at 77.3 K. The critical current density Jc of 3.0×102 A/cm2 was obtained for a repressed sample with a highly oriented microstructure.
Far-field characteristics of optically pulsed millimeter wave antennas
Authors: Lutz Charles R. , DeFonzo Alfred P.
Published: July 2002

We describe a novel technique for measuring transient far-field radiation patterns emitted from optically pulsed, broadband, integrated antennas using photoconductive sampling methods. These devices are capable of generating and radiating short electrical pulses which contain frequency components exceeding 80 GHz. The far-field patterns in both the E and H planes are observed to consist of single, forward directed lobes which are shown to have a cosine-squared dependence. In addition, there are no indications of any additional secondary sidelobes in either of the principal planes.
ZnHgTe as a material for ambient temperature 10.6 μm photodetectors
Authors: Piotrowski Jozef , Adamiec Krzysztof , Maciak Andrzej , Nowak Zenon
Published: July 2002

Ambient temperature 10.6 μm ZnHgTe photodetectors are reported. Undoped and Cu-doped bulk Zn0.115Hg0.885Te crystals have been grown by the quench-anneal technique. Homogeneity of ±0.002 mol has been determined by x-ray lattice constant measurement. The absorption coefficient as a function of wavelength, photoconductive lifetime, Hall concentration, and mobility have been measured for both intrinsic and Cu-doped p-type material. Infrared photoconductors have been fabricated and characterized. The relative stability and hardness make the fabrication of the devices easier compared to the HgCdTe, and the ατ/n figure of merit of Hg0.885Zn0.115Te at 10.6 μm, a factor of at least 4 higher compared to HgCdTe, has been found. The detectivity of 108 cm Hz1/2/W seems to be achievable using HgZnTe photoconductors with optimized composition, doping, and geometry.
Correlation between resonantly excited magnetic-field split donor-bound exciton components with their excited state emission analogues in GaAs
Authors: Reynolds D. C. , Bajaj K. K. , Theis W. M. , Yu P. W. , Chand Naresh
Published: July 2002

We relate each resonantly excited spin-split component of the transition involving the first rotator state of the donor bound exciton complex with its analogous emission component in which the donor electron returns to an excited state in the presence of a magnetic field. The allowed and forbidden transitions for resonant excitation and emission of this system for two different chemical donors are observed and are compared with their calculated values.
Bias-induced structure transition in reactively sputtered TiN films
Authors: Hashimoto Keiichi , Onoda Hiroshi
Published: July 2002

The properties of TiN films deposited under large negative bias (up to ‖920‖ V) in dc reactive sputtering have been investigated. A crystallographic structure transition in TiN films was observed with an increase of negative substrate bias in reactive sputtering. The crystal orientation normal to the film surface changed from 〈111〉 to 〈200〉 direction at the negative substrate bias voltage higher than approximately ‖200‖ V. The crystal orientation transition was independent of substrate crystallographic information. The bias sputtered TiN film never absorbed oxygen when it was exposed to air. The porosity of TiN film has been much improved by applying a large negative substrate bias.
Harmonic cross phase modulation in ZnSe
Authors: Ho P. P. , Wang Q. Z. , Ji D. , Jimbo T. , Alfano R. R.
Published: July 2002

The temporal profiles of harmonic cross phase modulation pulses from 500 to 570 nm generated in ZnSe by a 1054 nm picosecond pulse have been observed and theoretically modeled. The pulse shape of these harmonic-modulated pulses is accounted for by the interference and induced phase matching of the harmonic generated waves in ZnSe by cross phase modulation.
Direct pattern replication in plasma deposited silicon nitride films by 193 nm ArF excimer laser-induced suppression of etching
Authors: Donnelly V. M. , Mucha J. A.
Published: July 2002

Exposure of plasma deposited silicon nitride to 193 nm ArF excimer laser radiation suppresses the etch rate in buffered HF solution by as much as a factor of 50. Using a contact mask, 0.23 μm lines and spaces were transferred into silicon nitride by this exposure and etching technique. The mechanism involves transient thermal annealing induced by the 15 ns laser pulses, which reduces the concentration of NH and SiH groups.
Spatially distributed gains in semiconductor lasers
Authors: Le Grand Y. , Le Floch A.
Published: July 2002

A careful analysis of the gain using the amplified spontaneous emission in semiconductor lasers concludes that there is a spatial distribution of the gain. A twofold distribution is observed in the planes parallel and perpendicular to the junction with different decreasing variations from the laser axis to the edge of the radiation lobe. Collecting the entire emitted light beam gives usually too low gain values. Gain measurements restricted to the region around the laser beam axis lead to an improvement of the gain value determination being within 96% of the actual value determined by the laser threshold.
Determination of generation lifetime in intrinsic polycrystalline silicon
Authors: Hurley P. K. , Taylor S. , Eccleston W. , Meakin D.
Published: July 2002

A simple two-terminal method is described for the determination of generation lifetime in intrinsic polycrystalline silicon suitable for thin-film transistor applications using a metal/SiO2 /polycrystalline silicon/n-type silicon test structure. The method consists of monitoring the high-frequency capacitance of the test structure after the application of a voltage pulse of the correct polarity to cause deep depletion in the n-type substrate. Generation lifetimes of 34 ps to 19 ns are obtained for polycrystalline silicon films of varying grain size.
76 W cw monolithic laser diode arrays
Authors: Sakamoto Masamichi , Welch David F. , Endriz John G. , Scifres Donald R. , Streifer William
Published: July 2002

cw output power levels of 76 and 55 W have been obtained from 1 cm monolithic AlGaAs laser diode arrays with an aperture width of 3 and 2 mm at a heatsink temperature of 0 and 23 °C, respectively. One of the diodes has been operated for over 5000 h at varying power levels between 5 and 10 W and at varying temperatures between 20 and 40 °C and operated successfully for over 3000 h at power levels over 7 W.
Study of planarization of cobalt silicide lines and silicon surfaces by scanning force microscopy and scanning electron microscopy
Authors: Robrock K.-H. , Tu K. N. , Abraham D. W. , Clabes J. B.
Published: July 2002

Fine lines of 1.5-μm-wide and 80-nm-thick Co were patterned by a lithographic technique and deposited by electron gun onto (100) Si surfaces. Reacting the Co and Si to form CoSi2 lines was carried out at 600 °C in He atmosphere. The composite surface consisting of alternating silicides and Si as seen by scanning electron microscopy showed qualitatively that the silicide lines have sunk completely into the Si and the entire surface appears planar. Quantitative changes in vertical direction before and after the formation of the silicide lines have been measured by atomic force microscopy.
Identification of oxygen vacancies in YBaCuO superconductors by high-resolution electron microscopy
Authors: Liang Y. H. , Chen J. , Feng D.
Published: July 2002

High-resolution electron microscopy studies as well as computer simulation studies on oxygen vacancies in Y-Ba-Cu-O superconductors show that the existence of oxygen vacancies at {0, 1/2, 0} sites leads to the distortions of structural images. For certain imaging conditions, the spots corresponding to the column of oxygen vacancies can be distorted heavily, so that the indirect image of oxygen vacancies in Y-Ba-Cu-O superconductors may be acquired. The results reveal that even in local area the oxygen vacancies may be distributed regularly.
Hysteretic ac losses in high-temperature superconductors
Authors: Kozlowski G. , Chen X. Y.
Published: July 2002

Theory of ac losses in the type II superconductors in the frame of the critical state model [J. Thompson, M. Maley, and J. R. Clem, J. Appl. Phys. 50, 3531, 3518 (1979)] is applied to high Tc materials (Y-Ba-Cu-O) assuming an exponential drop of the critical current density Jc with both magnetic field and temperature. The dependence of dc magnetic field (H1) at which ac loss minimum occurs on an amplitude of ac magnetic field (h0) and on temperature Tc is calculated numerically. The two maxima of the total ac losses are found: one of them is very close to Tc and second maximum below Tc shifts to lower temperatures with increasing ac or dc magnetic field.
Response to ‘‘Comment on ‘Small field behavior of critical current in Y1Ba2Cu3O7 sintered samples’ ’’
Authors: Paternò G. , Alvani C. , Casadio S. , Gambardella U. , Maritato L.
Published: July 2002

In our response we would like to point out the fitting of the data has done to account for the shift of the maximum magnetic field dependence of the critical current. This shift on the order of 1 Gauss or less is gener ally observed in all our data and is attributable to the residual external field. Since we used a crude junction model, the self−field effects were not included. (AIP)
Optical notch filter using thermotropic liquid crystalline polymers
Authors: Tsai M. L. , Chen S. H. , Jacobs S. D.
Published: July 2002

Poly(γ-benzyl L-glutamate), partially transesterified with 1-dodecanol, and polysiloxane were employed to fabricate a right- and left-handed optical element, respectively. The wavelength of selective reflection was tuned via physical blending or annealing at a proper temperature. An optical notch filter comprising elements with each handedness showed an optical density of 2.0 within the rejection band and 73 to 83% transmission outside the band, suggesting liquid crystalline polymers as promising materials for the construction of environmentally robust optical notch filters.
Misfit accommodation in a lattice-mismatched HgTe-CdTe superlattice/HgCdTe heterostructure grown by molecular beam epitaxy
Authors: Hanlon T. R. , Koestner R. J. , Liu H.-Y.
Published: July 2002

We report an x-ray diffraction study of a HgTe-CdTe superlattice (SL)/HgCdTe heterostructure grown by molecular beam epitaxy (MBE). The diffraction results are used to place an upper bound on the misfit accommodation at the lattice-mismatched SL/HgCdTe interface. The misfit accommodation at the heterointerface is at least an order of magnitude less than that predicted by equilibrium misfit theory. It appears that the low substrate temperature used in MBE HgCdTe growth imposes a kinetic barrier to misfit accommodation.
Calculations of the electric field dependent far-infrared absorption spectra in InAs/AlGaSb quantum wells
Authors: Hong S. , Loehr J. P. , Oh J. E. , Bhattacharya P. K. , Singh J.
Published: July 2002

Excitonic and band-to-band absorption spectra are calculated for vertical incident radiation for the InAs/AlGaSb multiple quantum well structures. Due to the special band lineup of this heterostructure, the absorption spectra can be tailored to respond in far infrared. The electric field dependence of the spectra shows blue shift and enhanced absorption in contrast to the situation in type I quantum wells. Applications to far infrared detectors are discussed.
Charge confinement in heterojunction acoustic charge transport devices
Authors: Peterson G. A. , McCartin B. J. , Tanski W. J. , LaBarre R. E.
Published: July 2002

An equilibrium model is developed for charge confinement in heterojunction acoustic charge transport (HACT) devices. The Poisson–Boltzmann equation is solved for the self-consistent potential and packet charge distribution in a surface acoustic wave (SAW) superimposed on a (Al,Ga)As/GaAs hetrostructure. Numerical results are presented for the charge capacity of a 275 MHz HACT configuration. For a 1 V SAW potential, the charge capacity is limited by the heterojunction well depth rather than by space-charge lowering of the SAW barrier.
Low-energy ion beam effects on the molecular beam epitaxical growth of III-V compound semiconductors: A Monte Carlo simulation study
Authors: Ogale S. B. , Madhukar A.
Published: July 2002

Effects of low-energy ion beam on the growth rate, cluster dynamics, and evolution of surface morphology in molecular beam epitaxical growth of a III-V compound semiconductor are examined via Monte Carlo simulations. It is shown that for beams incident at a shallow angle (<10°), the effects can vary significantly with the azimuthal orientation. It is also demonstrated that use of an ion beam can lead to improved surface morphology in the case of growth of alloys.
A stable n-channel indium phosphide field-effect transistor with an amorphous hydrogenated silicon gate
Authors: Roditi E. , Iliadis A. A. , Christou A.
Published: July 2002

InP field-effect transistors (FETs) with an amorphous hydrogenated Si (a-Si:H) gate resulted in metal-insulator-like FET characteristics with no observable current drift and a transconductance of 30–38 mS/mm. The stability of this gate system is attributed to the hydrogen passivation of the InP surface and the low temperature of a-Si:H deposition, as indicated by Auger and low-energy electron probe analysis.
Relating the chirp parameter to the number of quantum wells in GaAs/AlGaAs waveguide modulators
Authors: Hausken T. , Yan R. H. , Simes R. J. , Coldren L. A.
Published: July 2002

For wavelengths near the quantum well absorption edge it is found that fewer quantum wells favor ideal phase modulation in GaAs/AlGaAs waveguide modulators. This is due to the dominance of the linear electro-optic effect over quantum absorption effects in the separate confinement waveguide. For TE polarization, it is found that the chirp parameter varies from <1 to >10 at −5 V and λ=0.89 μm in actual devices depending on the number of wells. The data fit estimates from theory. For TM polarization no dependence was observed as expected. For an integrated laser/phase modulator (with different absorption edges) a 4-well structure may be near optimum to maximize the modulation efficiency and to still have low laser threshold current.
Transient response of quasiparticle injected superconducting links
Authors: Sprik R. , Gallagher W. J. , Raider S. I. , Bumble B. , Chi C.-C.
Published: July 2002

We have fabricated submicron injection-controlled NbN links with gain and measured their injection-triggered superconducting-to-normal transition to occur in 0.5–2.6 ns at 4 K, governed by condensate dynamics. The transient pulse shape displays a rising-edge kinetic-inductance spike and a strong dependence on the amplitude of the injected quasiparticle current similar to microbridges driven by supercritical currents. A modified dynamic effective-temperature model is used to interpret the transient time and the pulse shape.
Temperature flashes in reentrant superconductors and compounds with metal-insulator transition
Authors: Buzdin A. I. , Moshchalkov V. V. , Simonov A. Y.
Published: July 2002

Local heating in reentrant superconductors and compounds with the metal-insulator transition along the track of the high-energy particle is studied. Numerical calculations of temperature flashes in VO2 are carried out. Possible applications of this phenomenon in the detectors of the particles are discussed.
Experimental study of guided-wave modes in 1.3 μm InGaAsP light-emitting diodes
Authors: Folkes P. A. , Henein G. , Wessel T. , Mantie A. , Hessler J. , Ceruzzi A.
Published: July 2002

We report the results of an experimental study of the far-field characteristics of InGaAsP edge-emitting light-emitting diodes. Our results show that the asymmetric structure in the transverse far-field distribution of the device is caused by modes which are supported by the asymmetric dielectric waveguide. These modes propagate in the InP cladding layer with the higher refractive index at an angle to the fundamental mode. Their relative intensities, compared to the fundamental mode intensity, increase as the active layer thickness decreases below 0.1 μm, accounting for the observed concomitant decrease in the fiber-coupling efficiency of these devices.
Outdiffusion of Cu through Au: Comparison of (100) and (111) Cu films epitaxially deposited on Si, and effects of annealing ambients
Authors: Chang Chin-An
Published: July 2002

Outdiffusion of Cu through thin gold films is studied as functions of Cu orientation and annealing ambients. (100) Cu films were epitaxially deposited on (100) Si, and (111) Cu on (111) Si, with commonly (111) oriented Au films deposited on Cu. Heating was conducted at 170 °C to minimize the Cu silicide formation. Structures with (111) Cu invariably give a higher surface accumulation of Cu than the counterparts of (100) Cu for each ambient, including the as-deposited samples. The accumulation is the highest in air, followed by N2-O2 and N2-H2, in agreement with the ambient effects on many other systems with gold as the overcoating layer. The orientation dependence of the outdiffusion rates of Cu through Au is related to the bonding structures at the Au-Cu interface. The face-centered-cubic structure of Cu makes the Au/Cu (111) interface more favorable for the release of Cu than the Au/Cu (100) interface, in agreement with the observed orientation dependence.
Valley selective tunneling transistor based on valley discontinuities in AlGaAs heterostructures
Authors: Singh Jasprit
Published: July 2002

The conduction-band discontinuities in AlxGa1−xAs/AlyGa1−yAs heterostructure for various valleys (Γ, L, X) are utilized to conceive of a valley selective tunneling transistor. At low temperature, the perpendicular tunneling current is very small because of the large Γ-Γ discontinuity and the small prefactor for Γ to X tunneling. However, if the valley population is altered by applying a lateral bias to the emitter, one can dramatically alter the perpendicular current since the X-X discontinuity is nonexistent and the L-L discontinuity is very small. By choosing proper values of x and y in the heterostructure, a very large current (power) change can be produced in the on and off states.
Electrolyte-free electrochromic device
Authors: Carpenter Michael K. , Conell Robert S.
Published: July 2002

A novel, solid-state electrochromic device is described which utilizes a single film of Prussian blue as the only electrochemically active element. The device can be reversibly bleached by the application of a voltage across the film. Removal of the voltage results in immediate recoloration.
Polarization-independent optical switching of an inhomogeneously pumped laser diode
Authors: Blixt Peter , Öhlander Ulf , Sahlén Olof
Published: July 2002

The polarization dependence of the optical input energy required to switch an inhomogeneously pumped bistable laser diode is studied at various input signal wavelengths. Polarization-independent switching is achieved for input pulse wavelengths 30–40 nm shorter than the lasing wavelength of the bistable laser diode, whereas input pulse wavelengths close to the lasing wavelength result in a strong polarization dependence. A simple theory explains the observed behavior.
Damage-induced high-resistivity regions in Al0.48In0.52As
Authors: Pearton S. J. , Hobson W. S. , Chakrabarti U. K.
Published: July 2002

The sheet resistivity of oxygen-implanted n+-Al0.48In0.52As grown on InP was measured as a function of oxygen ion dose and post-implant annealing temperature. The sheet resistivity is >105 Ω/⧠ after implantation for doses in the range 1012–8×1013 cm−2, and increases to >107 Ω/⧠ after annealing at 500 °C. Temperature-dependent Hall measurements show that the resistivity of this compensated AlInAs has a thermal activation energy of 0.68 eV. Above 600 °C the damage-related compensation is removed and the material is returned to its original resistivity. We find no thermally stable, oxygen-related deep acceptors in AlInAs, in contrast to the results for AlGaAs.
Transient grating dynamics in Cd1−xMnxTe diluted magnetic semiconductor superlattices
Authors: Harwit Alex , Ritter M. B. , Hong J. M. , Awschalom D. D. , Chang L. L.
Published: July 2002

The dynamics of carriers excited from both bulk and superlattice samples of Cd1−xMnxTe have been analyzed using a picosecond transient grating optical technique in a reflection geometry. Two distinct relaxation times were observed from the decays of orientational and carrier density gratings, yielding an upper bound on the ambipolar mobility of 6000 cm2/(V s). Measurements have been performed as functions of sample temperature, photon energy, and grating period.
Theory and experiment of the parasitic-free frequency response measurement technique using facet-pumped optical modulation in semiconductor diode lasers
Authors: Lange C. H. , Su C. B.
Published: July 2002

The letter describes the theory and experiment of the newly developed parasitic-free frequency response measurement technique using facet-pumped optical modulation on diode lasers. It was found that the modulation damping rate depends on the relative position of the pump laser wavelength with respect to the Fabry–Perot resonance wavelength of the laser under study. This effect is fully explained in terms of the carrier-induced index change. For multilongitudinal mode lasers, it is shown experimentally and theoretically that the damping rate and frequency response measured by this technique give the intrinsic frequency response corresponding to direct current modulation only if the cavity lengths of pump and probed lasers are equal, and then only if the pump laser wavelength coincides with the Fabry–Perot transmission maximum or minimum of the probed laser.
Large optical nonlinearities in semiconductor superlattices
Authors: Morrison I. , Jaros M. , Beavis A. W.
Published: July 2002

We show that the nonlinear response of a direct-gap semiconductor superlattice is greatly enhanced when the separation of the lowest two conduction minibands approaches the magnitude of the principal gap. Two structures exhibiting this enhanced nonlinear response are described.
Variation of T
c0 in the 110 K superconductor Bi1.5Pb0.5Ca2Sr2Cu3Ox
Authors: Ganapathi L. , Narayan J. , Kumar Ashok
Published: July 2002

We have systematically investigated resistance of a bismuth cuprate Bi1.5Pb0.5Ca2Sr2Cu3Ox as a function of different annealing treatments. X-ray diffraction and transmission electron microscopy studies were performed on concomitant specimens for correlations between structure and superconducting properties. A sharp 110 K superconducting transition was observed in the sample which was isostructural with the n=2 member of the (Bi,Pb)2(Ca,Sr)n+1CunO2n+4+δ family. The zero resistance transition temperature Tc0 was found to be sensitive to annealing at 673 K with a best result of 100 K for 30 min annealing. It is proposed that Tc0 and transition width in bismuth cuprates are sensitive to oxygen stoichiometry.
Dynamic behavior of negative charge trapping in thin silicon oxide
Authors: Haddad Sameer , Cagnina Sal
Published: July 2002

The trapping of negative charges in thin oxide under bipolar and unipolar dynamic stressing is compared. Bipolar stressing causes significantly less trapping than unipolar stressing. The difference is attributed to the enhanced electron detrapping during the bipolar stress. This detrapping mechanism is strongly dependent on the amount of charge injected through the oxide and, for a fixed amount of injected charge, is a weak function of the stressing current density.
Highly textured thick films by a melt-annealing technique in the Bi-Sr-Ca-Cu-O system
Authors: Xu Ming , Cornelius A. L. , Shi Donglu , Chen J. G. , Dabrowski B. , Miller D.
Published: July 2002

A melt-annealing method has been developed to deposit highly textured superconducting thick films on different substrates in the Bi-Sr-Ca-Cu-O system. As opposed to previous techniques, this method uses powder made from an extremely dense glass sample to yield very uniform and dense thick films. The x-ray diffraction and scanning electron microscopy results indicate that the superconducting phase is strongly oriented along the c axis perpendicular to the substrate and the films are chemically uniform. Electrical transport measurements consistently show a Tc near 80 K for all samples.
Oxygen concentration of Eu1Ba2Cu3O7−x in vacuum: An atom probe study
Authors: Elswijk H. B. , Melmed A. J. , Camus P. P.
Published: July 2002

Atom Probe mass analysis, at 85 K, using a wide-angle instrument was used to measure the oxygen content and metallic stoichiometry of the near-surface region of the superconducting ceramic oxide Eu1Ba2Cu3O7−x (x≂0.1) after vacuum exposure at room temperature. Routine specimen preparation, handling, and field-ion imaging produced a specimen which had already lost oxygen such that its measured surface oxygen content corresponded to x=0.73 and the metallic stoichiometry of the surface was not the expected 1:2:3 but was enhanced in Ba and Eu. The specimen was subsequently exposed to vacuum for up to 80 h at room temperature and no additional loss of oxygen was detected. It was concluded that either (1) a stoichiometric low-oxygen surface also would not have lost oxygen or (2) the nonstoichiometric layer forms a barrier for subsequent oxygen loss.
Structural study of undoped and doped Bi2Sr2CuO6 phases by transmission electron microscopy
Authors: Wen J. G. , Liu Y. , Ren Z. F. , Yan Y. F. , Zhou Y. Q. , Fung K. K.
Published: July 2002

Bi-based superconducting phases have been studied by transmission electron microscopy. The strong one-dimensional modulations in undoped and Ce-doped monoclinic Bi2 Sr2 CuO6 (2201) samples are different from one another. We have found a new 2201 phase containing Pb and Ca with orthorhombic symmetry in nominal (Bi0.90 Pb0.10 )2 Sr2 CaCu2 O8 crystals. Its structure with space group Bbmb and two-dimensional modulation are analogous to those of the Pb-doped higher members of the structural series Bi2 Sr2 Can−1 Cun O2n+4 . Hence, this new orthorhombic rather than the monoclinic 2201 phase should be the first member of the structural series.
Preferential growth of [001] twist boundaries in the Bi-Sr-Ca-Cu-O superconductor
Authors: Takahashi Yutaka , Mori Minoru , Ishida Yoichi
Published: July 2002

High voltage electron microscopy showed that a [001] twist boundary is abundant in the Bi-Sr-Ca-Cu-O superconductor when it is prepared by a solid-state reaction method. It is certain that coincidence orientation boundaries such as ∑=13 and ∑=17 are preferred.
Photorefractive effect in La3Ga5SiO14-Pr3+ piezoelectric crystals
Authors: Fridkin V. M. , Kaminskii A. A. , Lazarev V. G. , Astaf’ev S. B. , Butashin A. V.
Published: July 2002

The pronounced photorefractive effect in La3Ga5SiO14-Pr3+ crystals has been revealed. This is the first observation of the photorefraction caused by the bulk photovoltaic effect in a piezoelectric crystal. In accordance with symmetry features of the bulk photovoltaic effect in trigonal La3Ga5SiO14-Pr3+, a value and a sign of the photorefraction depend on the orientation of an inducing light polarization vector. Experimental photorefraction data are in good agreement with phenomenological description. The discovered phenomenon may lead to interesting peculiarities in photorefractive recording and adaptive optics.
Electrical characteristics of reoxidized-nitrided chemical vapor deposited oxides
Authors: Hwang H. , Ting W. , Kwong D. L. , Lee J. , Buhrow L. , Bowling R. A.
Published: July 2002

This letter presents electrical characteristics of thin (110 Å) metal-oxide-semiconductor gate dielectrics formed by chemical vapor deposited (CVD) SiO2, followed by rapid thermal nitridation and furnace reoxidation. Electrical measurements show that reoxidized-nitrided CVD dielectrics exhibit lower rates of interface-state generation and electron trapping under electrical stress, as compared to as-deposited CVD oxides. Combining with the advantage of lower defect density from CVD oxides (as compared to thermal oxide), these reoxidized-nitrided CVD films may be promising candidates for thin dielectrics applications.
Composition and substrate effects on the structure of thin-film CuGaSe2
Authors: Hallak H. , Albin D. , Noufi R.
Published: July 2002

Two opposite trends in the variation of d spacing (2θ) with composition are observed for the (112) peak position in x-ray diffraction patterns for evaporated CuGaSe2 films on different substrates. The 2θ value tends to increase with increasing molecularity for Al2 O3 and 7059 glass substrates and decreases for Mo-coated Al2 O3 and 7059 glass substrates. The films are composed of CuGaSe2 plus impurity phases, and the ‘‘actual’’ molecularity of the CuGaSe2 does not exceed 0.5.
Early stages of the heteroepitactic growth of hematite on (0001) Al2O3 by transmission electron microscopy
Authors: Tietz Lisa A. , Summerfelt Scott R. , English Gerald R. , Carter C. Barry
Published: July 2002

A new method for studying the early stages of the growth of oxide epilayers by transmission electron microscopy (TEM) is described. The technique uses well-characterized, single-crystal TEM foils as substrates for the deposition process. In the present study, chemical vapor deposition was used to form small islands (50–300 nm) of α-Fe2O3 on (0001) oriented Al2O3 thin-foil substrates. The preferential nucleation of islands at surface steps on the alumina is clearly demonstrated. Selected area diffraction and moiré fringe pattern analysis are used to show the epitactic nature of the growth and to study the island morphology.
Metalorganic molecular beam epitaxy of InP, Ga0.47In0.53As, and GaAs with tertiarybutylarsine and tertiarybutylphosphine
Authors: Ritter D. , Panish M. B. , Hamm R. A. , Gershoni D. , Brener I.
Published: July 2002

Thermally cracked tertiarybutylarsine and tertiarybutylphosphine were used to replace AsH3 and PH3 for the growth of Ga0.47In0.53As and InP by metalorganic molecular beam epitaxy. For both materials, carrier concentrations n=(1–2)×1015 cm−3 were obtained at 300 and 77 K, with 77 K mobilities of 29 000 and 31 000 cm2 V−1 s−1. The GaAs was p-type with p=4×1015 cm−3 at both temperatures and a 77 K mobility of 2200 cm2 V−1 s−1. The lifetimes for carriers in 14–60 Å thick quantum wells were 3±1 ns. The reacting arsenic species for epitaxy were As2 and As4. The reacting phosphorus species were PH2 and possibly PH.
GaInAsP/InP buried-heterostructure surface-emitting diode laser with monolithic integrated bifocal microlens
Authors: Liau Z. L. , Walpole J. N. , Missaggia L. J. , Mull D. E.
Published: July 2002

A new surface-emitting diode laser has been demonstrated, which consists of a buried-heterostructure waveguide gain region on one side of the substrate and a bifocal microlens of 210 μm diameter on the other side. The bifocal microlens is composed of a collimating lens in the center (70 μm diameter) and a spherical mirror in the surrounding region, for output collimation and optical feedback, respectively. Accurate alignment between the gain region and the microlens has been obtained by using the focused light spot produced by the latter. Initial device results show room-temperature pulsed threshold currents around 92 mA (with a low of 70 mA) and far-field patterns with a narrow central lobe of 1.25°.
Fabrication of a two-dimensional phased array of vertical-cavity surface-emitting lasers
Authors: Yoo Hoi-Jun , Scherer A. , Harbison J. P. , Florez L. T. , Paek E. G. , Van der Gaag B. P. , Hayes J. R. , Von Lehmen A. , Kapon E. , Kwon Young-Se
Published: July 2002

We report the successful fabrication of a two-dimensional phase-locked array of vertical-cavity surface-emitting lasers. The array was comprised of more than 160 vertical-cavity surface-emitting lasers of 1.3 μm diameter with a separation of less than 0.1 μm between each lasing element. The array had a 25 μm diameter and each of the elemental lasers was located on a two-dimensional rectangular lattice. The threshold current of the two-dimensional array 45 mA yields a threshold current of 280 μA for an elemental laser. The far-field beam angle of the array was as narrow as 7°, and the spectral purity was found to be good enough to allow for a clear holographic image reconstruction of a holographic memory.
Binary-optics miniature Talbot cavities for laser beam addition
Authors: Leger J. R. , Griswold M. P.
Published: July 2002

A miniature external cavity has been fabricated from a single 4.5 mm substrate for coherent beam addition of a linear AlGaAs laser array. Binary-optics elements are fabricated on the front surface for laser beam collimation and onto the back surface for lateral mode selection. Near-diffraction-limited performance has been observed with up to 80% of the far-field power contained in the central lobe.
Stimulated emission from monolayer-thick AlxGa1−xAs-GaAs single quantum well heterostructures
Authors: Lee J. H. , Hsieh K. Y. , Hwang Y. L. , Kolbas R. M.
Published: July 2002

Stimulated emission from a clearly defined quantum well transition has been observed from single quantum wells as thin as two monolayers (ML, 1 ML=2.83 Å). These results are unexpected since previous experimental and theoretical work has indicated that if the well width Lz is smaller than the scattering path length of electrons or holes, carrier collection becomes inefficient and the quantum well cannot support stimulated emission. Laser thresholds of these separate confinement, single quantum well samples are quite low, despite the fact that these ultrathin quantum wells are undoped and do not have graded band-gap confining layers. These unexpected results can be explained in terms of the spatial extent of the wave function rather than the well thickness.
Effect of optical phonons on femtosecond pulse propagation in coplanar striplines
Authors: Hasnain G. , Goossen K. W. , Knox W. H.
Published: July 2002

A full-wave analysis of the dispersion in coplanar-type transmission lines is made including the effect of material dispersion arising from a frequency-dependent complex dielectric constant such as due to optical phonon resonances in the substrate. The results are used to examine the distortion of femtosecond electrical pulses propagating in coplanar striplines made on ultrathin as well as thick GaAs substrates. A new closed-form dispersion formula for coplanar lines is also reported, valid for complex dielectric constants and all values of frequency and line dimensions.
Doping and hydrogenation by ion implantation of glow discharge deposited amorphous silicon films
Authors: Galloni R. , Tsuo Y. S. , Baker D. W. , Zignani F.
Published: July 2002

We have studied the effects of ion implanting boron into glow discharge deposited hydrogenated amorphous silicon films (a-Si:H). Electrical activity more than two orders of magnitude higher than previously reported1 is measured in our samples. Implantations of Si ions are used to study the effect of post-annealing on the radiation damage. Hydrogen introduced by low-energy implantation and diffusion is found to completely recover electrical and optical characteristics in Si-implanted specimens even at the highest concentrations (1021/cm3), where annealing for 1 h at 260 °C was insufficient. Introduction of H in B-implanted samples was found to deactivate the boron, which can be reactivated by low-temperature annealing.
Copper microcircuit repair of opens using thermally driven exchange plating
Authors: von Gutfeld R. J. , Vigliotti D. R.
Published: July 2002

A two-step method for the repair of circuit board defects consisting of complete opens is described. First, a small copper bridge is grown in unacidified copper sulfate solution by passing a few milliamperes of ac current at a frequency of 2–2000 kHz through the break. Local Joule heating results in copper deposition and bridging of the open via thermally driven exchange plating. For the second step, the cross section of the repair is increased by exchange plating in acid copper, using up to ∼1 A of ac current at a frequency on the order of 60 Hz or greater.
Output saturation characteristics of erbium-doped fiber amplifiers pumped at 975 nm
Authors: Lidgard A. , Simpson J. R. , Becker P. C.
Published: July 2002

We report the signal saturation behavior of an erbium-doped fiber amplifier pumped at 975 nm. We have characterized the output saturation powers as a function of fiber length and observed that the output saturation powers peak at an optimum length close to the optimum length for small signal gain. The output saturation power is found to be higher at a signal wavelength of 1.555 μm than at 1.532 μm.
Molecular beam epitaxy versus chemical vapor deposition of silicon on sapphire
Authors: Richmond Eliezer Dovid , Twigg Mark E. , Qadri Syed , Pellegrino Joseph G. , Duffey Michael T.
Published: July 2002

Molecular beam epitaxy (MBE) of Si on sapphire (SOS) has dramatically different and superior properties compared to chemical vapor deposited (CVD) SOS. The strain in the Si epilayer decreases by 21%. A 40% higher electron Hall mobility occurs at room temperature. At LN2 temperatures the electron mobility increases to a level which is more indicative of bulk Si than of CVD SOS. The microtwin differential volume fraction profile is lower by more than an order of magnitude, and decreases below the detectable limit at 300 nm from the interface. The average Si/sapphire interface charge for MBE SOS is −8.0×1010 cm−2, while the interface charge of CVD SOS is 2×1012 cm−2.