bluuebunny/crossref_metadata_2025 huggingface dataset:
On-axis far-field emission from two-dimensional phase-locked vertical cavity surface-emitting laser arrays with an integrated phase-corrector
Authors: Warren M. E. , Gourley P. L. , Hadley G. R. , Vawter G. A. , Brennan T. M. , Hammons B. E. , Lear K. L.
Published: July 2002

We have fabricated large, two-dimensional (2D) arrays of optically pumped, phase-locked vertical cavity surface-emitting lasers that emit more than 50% of their light in a central on-axis lobe. The emission of the arrays was modified from the usual four-lobed far-field of 2D coupled arrays by incorporation of a binary phase-shift mask on the surface of the array. The array consists of Fabry–Perot resonators comprising GaAs/AlGaAs quantum wells surrounded by AlAs/AlGaAs quarterwave mirrors with a multiple order AlGaAs phase-delay layer on the top mirror stack. The phase-shift layer was etched away on alternating elements of the array. The resulting on-axis emission had an angular width of 2° for an array of approximately 100 elements.
High-power spatially coherent operation of unstable resonator semiconductor lasers with regrown lens trains
Authors: Srinivasan Swaminathan T. , Schaus Christian F. , Sun Shang-Zhu , Armour Eric A. , Hersee Stephen D. , McInerney John G. , Paxton Alan H. , Gallant David J.
Published: July 2002

We have obtained high-power spatially coherent operation in wide-stripe InGaAs/GaAs/AlGaAs semiconductor lasers using a monolithic unstable resonator [consisting of diverging lens elements incorporated above an asymmetric graded-index separate confinement heterostructure (AGRIN-SCH)]. The fabrication involves MOCVD regrowth after wet-chemical etching of lens-like patterns in a GaAs layer above the active region. Pulsed output powers of 175 and 490 mW have been obtained in 170- and 100-μm-wide lasers, respectively, with spatial coherence in the near field exceeding 60%. We observe good lateral mode discrimination up to 3.5 times threshold in the 100-μm stripes with a round-trip magnification of 6.4.
Post-growth annealing of low temperature-grown Sb-doped Si molecular beam epitaxial films
Authors: Hobart K. D. , Godbey D. J. , Thompson P. E.
Published: July 2002

Sb-doped Si films have been grown on (100) Si substrates at low temperature (∼350 °C) by molecular beam epitaxy. Through coevaporation with Sb, very high doping efficiencies were achieved over a carrier concentration range of 1×1017 to 1×1020 cm−3. Through calibration of the beam flux we found that the incorporation of Sb was very near unity up to a concentration of ∼5×1019 cm−3. As-grown films are of good quality. However, furnace annealing was shown to improve the mobility and completely activate the Sb. Temperature dependent Hall measurements were used to further characterize the films.
High-power coherently coupled 8×8 vertical cavity surface emitting laser array
Authors: Morgan R. A. , Kojima K. , Mullally T. , Guth G. D. , Focht M. W. , Leibenguth R. E. , Asom M.
Published: July 2002

We demonstrate record high pulsed output power exceeding 530 mW from an electrically pumped phase-coupled 8×8 vertical cavity surface emitting laser array (SELA) at room temperature. Three array types are compared: an 8×8 pixellated SELA(PSELA), an 8×8 grid contact SELA(CSELA), and a 78 μm×78 μm single broad area SEL(BSEL) emitter. The CSELA operating in a phase-coupled supermode exhibits the lowest threshold current (100 mA) and voltage (1.6 V), highest damage threshold and a smooth L-I characteristic with differential quantum efficiency ηd≳27%, the BSEL has the largest output power≳580 mW and a large ηd≳48%, the PSELA exhibited a large voltage with the largest ηd≳80%.
High transconductance in-plane-gated transistors
Authors: Wieck A. D. , Ploog K.
Published: July 2002

Focused-ion-beam written one-dimensional field-effect transistors are fabricated and characterized at room temperature. By writing these in-plane-gated channels with geometrical widths of 0.2–1.1 μm in heterostructures, we obtain one-dimensional transconductances of up to 170 μS for two channels in parallel. We determine the effective width of the channels, which ranges between 790 nm and zero, being still reproducibly tunable at a few nanometers. The reproducibility in fabrication already of the prototypes presented here is sufficient for integration applications. We observe current densities, which can only be explained by a strong velocity overshoot of the electrons and promises excellent high-frequency behavior of the device. The in-plane-gate transistor does not need any alignment and can easily be interconnected and integrated with a writing speed exceeding 106 devices per s.
Fluorine-enhanced oxidation of polycrystalline silicon and application to thin-film transistor fabrication
Authors: Kouvatsos Dimitrios N. , Hatalis Miltiadis K. , Jaccodine Ralph J.
Published: July 2002

The kinetics of the fluorinated oxidation of polycrystalline silicon thin films has been investigated and compared to the (100) single-crystal silicon case. The growth of silicon dioxide was performed at oxidation temperatures down to 650 °C in dry ambients, which was made possible by fluorine-induced oxidation enhancement; growth rates in the presence of fluorine additions approach those of wet oxidation. Silicon dioxide films grown on polycrystalline silicon were found to be thicker by about 10%–20% compared to films grown on (100) single-crystal silicon oxidized under the same conditions. The application of fluorinated gate oxides in the fabrication of n-channel polycrystalline silicon thin-film transistors was found to improve the effective electron mobility.
Raman spectroscopy of CySi1−y alloys grown by molecular beam epitaxy
Authors: Tsang J. C. , Eberl K. , Zollner S. , Iyer S. S.
Published: July 2002

Raman spectroscopy has been used to observe the C local mode in epitaxial CySi1−y layers grown by molecular beam epitaxy. The scattering cross section per C atom is independent of alloy concentration for y<2%. Lattice relaxation about substitutional C sites induces an extra peak near 475 cm−1.
Strained InAs single quantum wells embedded in a Ga0.47In0.53As matrix
Authors: Tournié Eric , Schönherr Hans-Peter , Ploog Klaus , Giannini Cinzia , Tapfer Leander
Published: July 2002

Strained InAs single quantum wells (SQWs) embedded in a Ga0.47In0.53As matrix are grown on InP substrates by a modified solid-source molecular beam epitaxy. The series of samples with well between 2 and 11 monolayers (ML) is characterized by high-resolution double crystal x-ray diffraction and photoluminescence (PL) spectroscopy. The excellent agreement obtained between simulated and experimental x-ray rocking curves demonstrates the coherence of the samples. A PL linewidth as narrow as 7 meV is measured at 6 K for the SQW with a thickness of 5 ML. This is the best result reported so far for InAs QWs grown on InP. In addition, luminescence is observed up to room temperature for all samples.
Transport critical currents in spray pyrolyzed films of TlBa2Ca2Cu3Oz on polycrystalline zirconia substrates
Authors: Tkaczyk J. E. , DeLuca J. A. , Karas P. L. , Bednarczyk P. J. , Garbauskas M. F. , Arendt R. H. , Lay K. W. , Moodera J. S.
Published: July 2002

Large critical currents with a relatively weak magnetic field dependence are obtained in thick films of TlBa2Ca2Cu3Oz. Transport measurements indicate Jc ≳105 A/cm2 at 77 K, zero field, and Jc≳104 at 60 K in a 2 T field applied along the c-axis. The observed behavior is attributed to a large degree of uniaxial alignment of platelike grains, and to superior intragranular flux pinning. These results are consistent with recent theories concerning the nature of vortices in highly anisotropic (layered) superconductors and ‘‘brick wall’’models of intergranular current transport.
In situ electron beam patterning for GaAs using electron-cyclotron-resonance plasma-formed oxide mask and Cl2 gas etching
Authors: Kohmoto S. , Takado N. , Sugimoto Y. , Ozaki M. , Sugimoto M. , Asakawa K.
Published: July 2002

A new in situ fabrication process for GaAs is developed. In this process, electron- cyclotron-resonance oxygen plasma is used for the first time to form an oxide mask for Cl2 gas etching. Using this technique, the time and oxygen gas pressure required for the oxidation are drastically reduced, compared to other oxidation methods. Line patterns with submicron width are successfully fabricated by partial modification of the oxide mask by electron beam irradiation and subsequent Cl2 gas etching.
Thermally activated reversible threshold shifts in YBa2Cu3O7−δ/ yttria-stabilized zirconia/Si capacitors
Authors: Qiao Jianmin , Ajimine Eric M. , Patel Paresh P. , Giese Geoffrey L. , Yang Cary Y. , Fork D. K.
Published: July 2002

YBa2Cu3O7−δ /yttria-stabilized zirconia (YSZ)/silicon superconductor–insulator–semiconductor capacitors are characterized with capacitance-voltage (C-V) measurements at different gate-voltage sweep rates and under bias-temperature cycling. It is shown that ionic conduction in YSZ causes both hysteresis and stretch-out in room-temperature C-V curves. A thermally activated process with an activation energy of about 39 meV in YSZ and/or at YSZ/Si interface is attributed to trapping/detrapping mechanisms in the SiOx interfacial layer between YSZ and Si. The negative mobile ions in YSZ can be moved by an applied electric field at room temperature and then ‘‘frozen’’ with decreasing temperature, giving rise to adjustable threshold voltages at low temperatures.
Photoelectrochemical etching of high aspect ratio submillimeter waveguide filters from n+ GaAs wafers
Authors: Khare R. , Hu E. L. , Reynolds D. , Allen S. J.
Published: July 2002

A 200 μm high-pass filter has been fabricated using the photoelectrochemical (PEC) etch process to form a series of waveguides through a Si-doped n+ GaAs (1×1018 cm−3) substrate. A metal mask on the sample surface with 100 μm square openings and 41 μm spaces was used to locally prevent PEC etching. The sample was etched in a (4:1:50) HCl:HNO3:H2O electrolyte for 1.5 h using an argon ion laser (514 nm) at an intensity of 0.7 W/cm2, and an applied bias of 0.35 V. The result was a series of highly anisotropic waveguides with a (3:1) aspect ratio. The transmittance curve had a cutoff of 45 cm−1 and a transmittance of 20% just above the cutoff.
Structure and thermal stability of Cu-In precipitates and their role in the semi-insulating behavior of InP:Cu
Authors: Leon R. P. , Werner P. , Eder C. , Weber E. R.
Published: July 2002

InP was found to be semi-insulating after Cu diffusion. This conversion of both n-InP and p-InP was ascribed to the presence of Cu-In precipitates that act as buried Schottky barriers. The thermal stability of both the precipitates and the electrical properties of InP:Cu were studied after high temperature annealing treatments. Atomic resolution microscopy was used to determine the structure of these precipitates. Diffraction studies of some of these inclusions show that they have the structure of the metallic hexagonal compound Cu16In9. The concentration of Cu-In precipitates was found to be comparable with what our calculations show would achieve intrinsic behavior due to the effect of the metallic inclusions.
Bright blue electroluminescence from hole transporting polycarbonate
Authors: Hosokawa Chishio , Kawasaki Nobuo , Sakamoto Shuji , Kusumoto Tadashi
Published: July 2002

Bright blue electroluminescence (EL) was observed for the EL cell with a nonconjugated polymer as an emitting layer. The emitting layer was composed of a hole transporting polycarbonate containing styrylamine as a functional repeating unit (SA-PC). SA-PC was soluble in many solvents. It was very easy to form a smooth and dense thin film at a thickness less than 100 nm without any recrystallization. For the EL cell with ITO/SA-PC/an oxadiazole derivative/Mg:Ag structure, we achieved bright luminance of 130 cd/m2 at a current of 80 mA/cm2 with an applied voltage of 11 V.
1.3 μm InAsyP1−y/InP strained-layer quantum well laser diodes grown by metalorganic chemical vapor deposition
Authors: Imajo Y. , Kasukawa A. , Namegaya T. , Kikuta T.
Published: July 2002

We report on the metalorganic chemical vapor deposition (MOCVD) growth of InAsyPl1−y/InP strained layer quantum wells and the successful lasing of novel InAsyP1−y/InP strained layer quantum well laser diodes at 1.3 μm for the first time. Full width at half maximum of room temperature photoluminescence was as narrow as 30.1 meV with a peak wavelength of 1.29 μm. A very low threshold current density of 0.45 kA/cm2 was obtained on broad contact lasers with a cavity length of 900 μm.
Visible electroluminescent subwavelength point source of light
Authors: Kuck Nily , Lieberman Klony , Lewis Aaron , Vecht Aron
Published: July 2002

A structure has been devised to generate a visible point source of electroluminescently produced light with subwavelength dimensions. This submicron (0.3 μm) spot of light is created by the combination of a standard dc electroluminescent powder, ZnS:MnCu, that is introduced into the tip of a glass micropipette coated with a transparent coating of conducting indium oxide as the anode and an appropriate electrode placed inside the pipette as the cathode.
Free electron laser induced two-photon absorption in Hg1−xCdxTe
Authors: Burghoorn J. , Anderegg V. F. , Klaassen T. O. , Wenckebach W. Th. , Bakker R. J. , van der Meer A. F. G. , Oepts D. , van Amersfoort P. W.
Published: July 2002

The powerful output of FELIX, the recently built Rijnhuizen free-electron laser, is used for the first frequency dependent study of nonlinear optical excitation of Hg1−xCdxTe in the far-infrared spectral region. Two-photon interband absorption has been investigated as a function of power and wavelength from 20 to 40 μm. This nonlinear optical absorption is used to perform autocorrelation experiments yielding the length of the micropulses of the free-electron laser on a femtosecond time scale. The predicted dependence of the micropulse length on the synchronization between optical and electron pulses in the laser cavity is observed.
Organic–inorganic multilayers: A new concept of optoelectronic material
Authors: Takada J. , Awaji H. , Koshioka M. , Nakajima A. , Nevin W. A.
Published: July 2002

By utilizing copper phthalocyanine (CuPc) and TiOx, we report the fabrication of organic–inorganic heteromultilayer structures as a new concept of optoelectronic material. These are based on an anticipated model where charge carrier photogeneration occurs in the CuPc layers, while the TiOx layers have the role of transportation of electrons in-plane after charge separation at the interfaces. Atomic force microscopy has confirmed the formation of layered structures for samples with an artificial period of more than 50 Å. The multilayers are found to exhibit 40 times higher photoconductivity than a CuPc single layer.
1.5 μm diode laser-based nonlinear frequency conversions by using potassium titanyl phosphate
Authors: Wang Weizhi , Nakagawa Ken’ichi , Toda Yasunori , Ohtsu Motoichi
Published: July 2002

Both second harmonic and sum-frequency generations by using 1.5 μm diode lasers in a type II phase matched potassium titanyl phosphate are demonstrated for the first time. A maximum second harmonic output power of 1.0 μW is obtained with the use of an external builtup cavity, and a 0.23 μW sum-frequency output power at 0.54 μm is obtained by using 1.5 and 0.82 μm diode lasers.
Optical study of surface dimers on sulfur-passivated (001)GaAs
Authors: Berkovits V. L. , Paget D.
Published: July 2002

Reflectance anisotropy (RA) spectrosocpy has been used to study at 300 K the intrinsic optical transitions on sulfur-passivated surfaces. The spectra allow to follow the modification of surface dimers after annealing at a temperature Ta. For Ta≊440 °C, the S-treated surface is covered by arsenic and sulfur dimers oriented along the [11̄0] direction. Upon subsequent heating, sulfur is desorbed and there appear gallium dimers oriented along [110]. Sulfur passivation has allowed to obtain stable surface structures, with a strongly reduced band bending, which are consistent with the known (2×1) and (4×6) reconstructions.
High pressure optical investigation of porous silicon
Authors: Zhou Weimin , Shen H. , Harvey J. F. , Lux R. A. , Dutta M. , Lu F. , Perry C. H. , Tsu R. , Kalkhoran N. M. , Namavar F.
Published: July 2002

We have performed the first photoluminescence (PL) measurements under hydrostatic pressure up to 37 kbar at room temperature on several porous silicon (Si) samples fabricated under different etching conditions. A blue shift of the PL peak energy was observed in all samples from 0 to ∼20 kbar. Above ∼20 kbar, the PL peak energy appears to be constant or even to exhibit a small red shift with pressure in some samples. This pressure dependence of the PL peak energy of porous Si is different from the pressure induced red shift in the PL from the indirect band gap of the bulk Si crystal, or the red shift in the PL from amorphous Si. The intensity of the PL peaks showed a decrease with increasing pressure. We have also observed a red shift with time when a blue laser continuously illuminated the sample. These results on the pressure dependence of porous Si provide critical information for modeling and determining the electronic structure of porous silicon.
Antiresonant reflecting optical waveguide-type, single-mode diode lasers
Authors: Mawst L. J. , Botez D. , Zmudzinski C. , Tu C.
Published: July 2002

Antiresonant reflecting optical waveguide (ARROW)-type diode lasers have been demonstrated for the first time. The ARROW structure is made in the lateral direction (i.e., the plane of the junction) by two-step metalorganic chemical vapor deposition. Stable, diffraction-limited beam operation is achieved to 0.6 W peak pulsed power and 20× threshold. The power contained within the diffraction-limited beam pattern is 420 mW with 60% of the energy residing in the central, diffraction-limited lobe. Modal calculations for ARROW lasers confirm very strong intermodal discrimination. Theoretical calculations and preliminary experimental data show that up to 90% of the energy can be obtained in the central lobe (475 mW diffraction-limited power).
Carrier heating and spectral hole burning in strained-layer quantum-well laser amplifiers at 1.5 μm
Authors: Hall K. L. , Lenz G. , Ippen E. P. , Koren U. , Raybon G.
Published: July 2002

We present the first polarization studies of femtosecond gain dynamics in strained-layer multiple-quantum-well laser amplifiers. We observe a response consistent with spectral hole burning when the diode is biased in the absorbing regime. In the gain regime, we show that the carriers are heated by free-carrier absorption and that there is a measurable delay (∼200 fs) in the thermalization of the hot-carrier distribution. Subsequent cooling to the lattice temperature follows with a time constant of ∼1 ps.
Ellipsometric study of Si0.5Ge0.5/Si strained-layer superlattices
Authors: Sieg R. M. , Alterovitz S. A. , Croke E. T. , Harrell M. J.
Published: July 2002

We present an ellipsometric study of two Si0.5Ge0.5/Si strained-layer superlattices grown by MBE at low temperature (500 °C), and compare our results with x-ray diffraction (XRD) estimates. Excellent agreement is obtained between target values, XRD, and ellipsometry when one of two available SixGe1−x databases is used. We show that ellipsometry can be used to nondestructively determine the number of superlattice periods, layer thicknesses, SixGe1−x composition, and oxide thickness without resorting to additional sources of information. We also note that we do not observe any strain effect on the E1 critical point.
Effect of oxygen concentration on the kinetics of thermal donor formation in silicon at temperatures between 350 and 500 °C
Authors: Londos C. A. , Binns M. J. , Brown A. R. , McQuaid S. A. , Newman R. C.
Published: July 2002

Early measurements of the initial rate of thermal donor formation in Czochralski silicon at 450 °C revealed a dependency on the fourth power of the oxygen concentration. This result has led to the view that the core of the defects contained four oxygen atoms. We now show that this dependency is observed only for anneals close to 450 °C. Our results indicate that oxygen dimerization controls the thermal donor formation kinetics but that the dimers become increasingly unstable above 400 °C.
Direct measurement of linewidth enhancement factors in quantum well lasers of different quantum well barrier heights
Authors: Zhao B. , Chen T. R. , Wu S. , Zhuang Y. H. , Yamada Y. , Yariv A.
Published: July 2002

The wavelength dependence of the linewidth enhancement factor (amplitude-phase coupling factor) α in quantum well lasers of different quantum well barrier heights have been determined from the spontaneous emission spectra and the Fabry–Perot mode wavelength shifts. It is found that the α parameter at lasing wavelength in GaAs/Al0.15Ga0.85As lasers is about twice as large as that in GaAs/Al0.30Ga0.70As lasers. The observation is consistent with the previously observed spectral linewidth behavior in these lasers, which were attributed to the different state filling effects.
Model for oxide damage from gate charging during magnetron etching
Authors: Fang Sychyi , McVittie James P.
Published: July 2002

Charge damage is a consequence of plasma nonuniformity which leads to a local imbalance of ion and electron currents to the wafer surface. Damage during etching is found to occur near endpoint and to scale with gate electrode edge length. A model is proposed in which surface currents prevent charging during most of the time the gate is etching. Near endpoint, these currents are terminated while a temporary conductive halo still remains around the gate. During a brief period before it disappears, the halo can collect enough current to charge the thin oxide to the point of conduction and subsequent damage. This model is supported by plasma measurements, etching damage results, and simulations via the Simulation Program with Integrated Circuits Emphasis.
On the lack of correlation between film properties and solar cell performance of amorphous silicon-germanium alloys
Authors: Xu X. , Yang J. , Guha S.
Published: July 2002

We have studied the performance of amorphous silicon-germanium alloy single-junction solar cells both before and after light soaking. The intrinsic layers of the cells have different germanium contents. Films were grown on glass with parameters nominally identical to those for the intrinsic layer of the cells and the defect density was measured using the constant photocurrent method. We do not find good correlation between cell performance and the measured defect density for these high quality materials.
Atomic layer epitaxy of AlAs using trimethylamine-alane and amino-As
Authors: Fujii Kazuyuki , Suemune Ikuo , Yamanishi Masamichi
Published: July 2002

Atomic layer epitaxy (ALE) of AlAs using trimethylamine-alane (TMAAl) and tris-dimethylamino-arsenic {As[N(CH3)2]3} was studied. One- and two-monolayer self-limiting growths of AlAs were observed depending on the TMAAl pressure. The self-limiting mechanism of the ALE in the two growth modes was studied with a transient quadrupole mass spectrometry and with a temperature programmed desorption. The main factor that gives the different self-limiting growths was discussed considering the properties of the Al surfaces revealed by these measurements.
Millimeter-wave response and linewidth of Josephson oscillations in YBa2Cu3O7 step-edge junctions
Authors: Divin Yu. Ya. , Andreev A. V. , Fischer G. M. , Mygind J. , Pedersen N. F. , Herrmann K. , Glyantsev V. N. , Siegel M. , Braginski A. I.
Published: July 2002

We have studied the response of YBa2Cu3O7 step-edge junctions to low-intensity millimeter-wave radiation in the temperature range from 4 to 80 K. The linewidth of the Josephson oscillations derived from the resonant part of the response at voltages V≂(h/2e)f is shown to be determined by thermal fluctuations at liquid nitrogen temperatures. At lower temperatures the observed linewidth increases indicating that low-frequency fluctuations become dominant in the junction as the temperature is reduced. Due to an inhomogeneous spatial distribution of the current the step-edge junction might be considered as a multijunction multiloop interferometer and the excess noise can be discussed in terms of spontaneous transitions between the different states of these interferometers.
In situ growth of epitaxial YBa2Cu3O7 thin films by on-axis unbalanced direct current magnetron sputtering
Authors: Savvides N. , Katsaros A.
Published: July 2002

Superconducting YBa2Cu3O7−x thin films are prepared in situ by on-axis dc magnetron sputtering from a single stoichiometric target. The magnetron uses an unbalanced magnetic field configuration to eliminate resputtering effects, and high quality thin films on MgO (100) substrates are realized with excellent reproducibility. The target is sputtered in Ar/O2 mixture at a fixed partial pressure ratio pAr/pO2= 15:1. We report on the growth and properties of films deposited (a) as a function of the total sputtering pressure pt (1–100 Pa) at fixed substrate heater temperature Ts=740 °C, and (b) as a function of Ts (600–860 °C) at fixed pt=42 Pa. Epitaxial c-axis thin films are obtained over a wide range of deposition conditions (Ts≥700 °C, pt≥30 Pa). These films have superconducting transition temperatures Tc=86–90 K, critical current densities Jc77≥106 A cm−2, and resistance ratios R300/R100=2.0–3.1.
Moire fringe images of twin boundaries in chemical vapor deposited diamond
Authors: Shechtman Dan , Feldman Albert , Vaudin Mark D. , Hutchison John L.
Published: July 2002

Features in lattice image micrographs of chemical vapor deposited diamond can be interpreted as Moire fringes that occur when viewing twin boundaries that are inclined to the electron beam. The periodicities in images of inclined twin boundaries with Σ=3 and Σ=9 misorientations have been modeled by computer graphic simulation.
Low-threshold operation of hemispherical microcavity single-quantum-well lasers at 4 K
Authors: Matinaga F. M. , Karlsson A. , Machida S. , Yamamoto Y. , Suzuki T. , Kadota Y. , Ikeda M.
Published: July 2002

We demonstrate low-threshold lasing at 4 K in optically pumped hemispherical In0.2Ga0.8As single-quantum-well microcavities. The incident threshold pump power density is 11 kW/cm2 corresponding to an absorbed power density of about 320 W/cm2, and the measured spontaneous emission factor β is about 0.01.
Bistable opto-optical switches with high optical gain based on n-i-p-i doping superlattices
Authors: Kiesel P. , Gulden K. H. , Höfler A. , Knüpfer B. , Kneissl M. , Riel P. , Döhler G. H. , Wu X. , Smith J. S.
Published: July 2002

We report on optical logic gates and bistable opto-optical switches with high gain operating at very low threshold power. These devices are ‘‘smart pixels’’ composed of n-i-p-i threshold switches and modulators. Very high values of 3×105 for the opto-optical gain (‘‘fan-out’’) and extremely low switching powers of less than 500 pW in combination with a broad hysteresis width of 200 pW are obtained. The switching power, the width of the hysteresis, and the opto-optical gain are all externally adjustable. The observed contrast ratio of 4.6 for the output signal corresponds to an optically induced voltage swing of 2.5 V.
Electrical quenching of photoluminescence from porous silicon
Authors: Koyama Hideki , Oguro Tsuyoshi , Koshida Nobuyoshi
Published: July 2002

We have studied the visible photoluminescence (PL) of porous silicon (PS) under the condition that a bias voltage is applied in the direction of the PS layer thickness. It is shown, for the first time, that the PL intensity is sharply decreased when increasing the voltage. This electrical PL quenching was completely reversible. This phenomenon is interpreted as to arise from field-enhanced tunneling of carriers between silicon crystallites. The result presented here strongly suggests that the visible luminescence of PS is not based on electronic transitions in some molecular substance, but on the radiative recombination in Si nanocrystallites.
High resolution x-ray diffraction of periodic surface gratings
Authors: van der Sluis P. , Binsma J. J. M. , van Dongen T.
Published: July 2002

We show that very clear satellite peaks (up to the 22nd order) from periodic surface gratings in InP can be obtained in a rocking curve provided that the appropriate diffraction geometry is chosen. For (001) oriented Si, InP, or GaAs substrates with corrugations in the [110] direction, measured with CuKα1, the optimal geometry is best approximated by the 113 reflection measured with a high angle of incidence. Due to beam compression, caused by the asymmetry of the reflection, this reflection is also suited to obtain two-dimensional reciprocal space maps. A simple slit can be used to obtain adequate detector resolution. The maps reveal in detail the shape of the grating. They are compared with model calculations based on Fourier transformation of the shape of the grating-crystal assembly.
Imaging-plate plane-wave x-ray topography of local lattice distribution due to growth striations in silicon crystals
Authors: Maekawa I. , Kudo Y. , Kojima S. , Kawado S. , Ishikawa T.
Published: July 2002

A newly developed imaging-plate plane-wave x-ray topography (IPPWT) method has been successfully applied to the quantitative analysis of local lattice distortion due to growth striations in magnetic-field-applied Czochralski silicon single crystals. IPPWT was found to possess sufficient spatial resolution to accurately measure variations of growth-induced local lattice distortions (Δd/d and Δα). The advantageous features of IPPWT, in comparison with conventional photographic-plate plane-wave x-ray topography, are a wide latitude in x-ray exposure conditions, better x-ray intensity linearity for performing quantitative analysis, and convenience in image processing and data handling.
Luminescence efficiency of near-surface quantum wells before and after ion-gun hydrogenation
Authors: Chang Ying-Lan , Tan I-Hsing , Zhang Yong-Hang , Merz James , Hu Evelyn , Frova A. , Emiliani V.
Published: July 2002

We have studied the effects of the proximity of a bare Al0.3Ga0.7As surface on the luminescence of an underlying GaAs quantum well (QW) before and after hydrogenation. The mechanism which is affected by H is tunneling to surface states through the surface barrier. Its thickness was varied by wet etching from 60 to 350 Å. Our experiments reveal that the degradation of luminescence efficiency from the QW is dependent on the surface barrier thickness and the excitation energy used in the photoluminescence measurements. A complete recovery or even further enhancement of luminescence efficiency was observed in the near-surface QW after low-energy ion-beam hydrogenation, even at room temperature.
Efficient modal dispersion phase-matched frequency doubling in poled polymer waveguides
Authors: Rikken G. L. J. A. , Seppen C. J. E. , Staring E. G. J. , Venhuizen A. H. J.
Published: July 2002

We report the design, manufacture, and characterization of poled polymer multilayer waveguides for frequency doubling. Phase matching is obtained by using modal dispersion between the zeroth-order fundamental lightwave and the first-order second-harmonic wave. By incorporating a very thin high refractive index satellite layer, the phase-match condition can be fulfilled with concomitant large overlap between the two waves, resulting in efficient doubling.
Effect of interface layer on the microstructure and electromigration resistance of Al-Si-Cu alloy on TiN/Ti substrates
Authors: Olowolafe J. O. , Kawasaki H. , Lee C. C. , Klein J. , Pintchovski F. , Jawarani D.
Published: July 2002

Al-Si-Cu alloy films sputter-deposited on reactively ion-sputtered TiN/Ti/SiO2 substrates were characterized and evaluated for interconnect reliability. Using x-ray diffraction techniques, both TiN and Al microstructures were analyzed and the (111) intensities of the latter correlated with the electromigration median time to fail (MTTF). The values of the MTTF increased with the Al(111) intensities for the TiN/Ti/SiO2 substrates annealed below 400 °C. A progressive decrease in both the Al(111) texture and MTTF was observed for substrates annealed above this temperature. While the improved Al(111) texture has been attributed to an improved TiN barrier textured in the (111) crystal plane (anneals below 400 °C), a TiO2 layer over the TiN barrier has been found responsible for the degradation of the Al(111) texture and the MTTF for barrier anneals above 400 °C.
Damping of the relaxation resonance in multiple-quantum-well lasers by slow interwell transport
Authors: Hangleiter A. , Grabmaier A. , Fuchs G.
Published: July 2002

We present a model for quantum-well lasers which for the first time provides an explanation for the increased damping of the relaxation resonance observed in these lasers. Slow transport of holes between the individual wells is shown to lead to a strongly inhomogeneous carrier distribution and to increased damping as well as to RC-like contributions to the modulation response. The model quantitatively explains the differences observed between lasers of varying structure and lasers made from different material systems.
Silicon atomic layer growth controlled by flash heating in chemical vapor deposition using SiH4 gas
Authors: Murota Junichi , Sakuraba Masao , Ono Shoichi
Published: July 2002

The separation between surface adsorption and reaction of SiH4 on a Si substrate has been investigated by heating the surface with a Xe flash lamp in an ultraclean low-pressure environment. About 0.4 atomic-layer epitaxy per flash-lamp light shot was observed on Si(100) at a substrate temperature of 385 °C and at SiH4 partial pressure of 500 Pa. The dependencies of SiH4 surface coverage on the SiH4 partial pressure and shot-to-shot time interval are expressed by the Langmuir adsorption type equation, assuming that the total adsorption site density is equal to the surface atom density.
Ge0.2Si0.8/Si Bragg-reflector mirrors for optoelectronic device applications
Authors: Kuchibhotla Ravi , Campbell Joe C. , Bean John C. , Peticolas Larry , Hull Robert
Published: July 2002

Previous work has shown that III-V semiconductor multilayer films can be designed to serve as Bragg reflector mirrors in optoelectronic devices. In this letter we extend that work to the fabrication of high reflectivity GexSi1−x/Si mirrors. Column IV designs are constrained both by the small refractive index between Si and GexSi1−x alloys and the limitations of strained layer epitaxy that can produce misfit dislocations in thick mirror stacks. Despite these limitations, we report on mirrors with reflectivities of over 50% at 1.5 μm. Furthermore, certain mirrors were overgrown with p-i-n diodes to demonstrate the feasibility of operation in a vertically illuminated, resonant cavity mode.
Low threshold voltage continuous wave vertical-cavity surface-emitting lasers
Authors: Rogers T. J. , Lei C. , Deppe D. G. , Streetman B. G.
Published: July 2002

Data are presented demonstrating a design and fabrication process for the realization of low-threshold, high-output vertical-cavity surface-emitting laser diodes with low series resistance. Lateral current confinement is achieved in the laser structures through the use of molecular-beam epitaxial regrowth over a 1000-Å-thick patterned layer of low growth temperature AlGaAs incorporated into the p-type top mirror. A maximum cw output power in excess of 5.7 mW, at 300 K is demonstrated for 15-μm-diam devices. With increased top mirror reflectivity (through the addition of dielectric layers), the low series resistance of the design results in a bias voltage of only 1.8 V at a threshold current of 1.9 mA for 10-μm-diam devices.
Room-temperature measurements of strong electroabsorption effect in GexSi1−x/Si multiple quantum wells grown by remote plasma-enhanced chemical vapor deposition
Authors: Murtaza S. S. , Qian R. , Kinosky D. , Mayer R. , Tasch A. F. , Banerjee S. , Campbell J. C.
Published: July 2002

We have used photocurrent measurements to demonstrate a strong electroabsorption effect in GexSi1−x/Si multiple quantum wells grown by remote plasma-enhanced chemical vapor deposition. Large voltage-induced shifts in absorption are observed at room temperature in the wavelength range from 1.2 to 1.58 μm. We anticipate that the results can be extended to fabricate GexSi1−x optoelectronic devices operating at room temperature.
Photoluminescence study of anodized porous Si after HF vapor phase etching
Authors: Shih S. , Jung K. H. , Kwong D. L. , Kovar M. , White J. M.
Published: July 2002

We have studied the mechanism of photoluminescence (PL) shift by hydrofluoric (HF) vapor phase etching in oxygen ambient. Vapor phase etching offers greater efficiency and flexibility, along with reduced damage and contamination for luminescence studies of porous Si. An initial blue shift followed by a red shift was observed in most cases. Transmission Fourier-transform infrared spectroscopy showed identical bonding environment before and after vapor phase etching, suggesting that the role of surface passivation is irrelevant to the observed PL shift.
Wide temperature scaling law of the secondary peak observed in magnetization curves of single crystals (La,Sr)2CuO4
Authors: Kobayashi T. , Nakayama Y. , Kishio K. , Kimura T. , Kitazawa K. , Yamafuji K.
Published: July 2002

Magnetization curves of single crystals (La1−xSrx)2CuO4 with various Sr contents were measured. A distinct increase of magnetization with increasing applied field was observed in Sr overdoped compositions, when the magnetic field was applied perpendicular to the CuO2 plane. The field, Bpk , where magnetization showed a maximum value, was strongly dependent on temperature. Its dependence was expressed by a universal relation √Bpk = c(x)[1−T/Tc(x)] over a wide temperature range; between 4.2 K and Tc. Possible mechanisms which give rise to the observed distinct secondary peak effect are discussed.
Observation of resonant and stimulated Raman scattering in ZnSe/CdSe quantum wells grown by atomic layer epitaxy
Authors: Chung H. Y. A. , Uhle N. , Tschudi T.
Published: July 2002

This letter reports the successful growth of short period (ZnSe)4/CdSe4 strained layer superlattices on (100) GaAs surface by atomic layer epitaxy. The superlattice was characterized by x-ray diffraction and Raman scattering. Superlattice period was calculated from the satellite peaks and was in good agreement with the expected value. 2LO Raman scattering in resonance with the E1h exciton level was observed. Experimental exciton energy was compared with the one calculated in a finite-square-well model. A Raman line due to stimulated Raman scattering was also observed.
Sb surface segregation and doping in Si(100) grown at reduced temperature by molecular beam epitaxy
Authors: Hobart K. D. , Godbey D. J. , Thompson P. E. , Simons D. S.
Published: July 2002

X-ray photoelectron spectroscopy, depth profiling with secondary ion mass spectrometry, and conductivity measurements have been performed on Sb-doped Si(100) films grown at low temperature (350 °C) by molecular beam epitaxy. The measurements reveal two important effects: (1) a significant increase in the surface segregation of Sb as the dopant concentration approaches 1×1020 cm−3, and (2) a decrease in surface segregation as the surface concentration of Sb reaches one monolayer. We believe that the presence of this monolayer of Sb is responsible for the surface segregation becoming self-limited and the associated bulk concentration exceeding 1×1020 cm−3.
Femtosecond gain dynamics in InGaAs/AlGaAs strained-layer single-quantum-well diode lasers
Authors: Sun C.-K. , Choi H. K. , Wang C. A. , Fujimoto J. G.
Published: July 2002

We report the first investigation of femtosecond gain dynamics in InGaAs/AlGaAs strained-layer single-quantum-well diode lasers using a multiple-wavelength pump probe technique. Studies demonstrate that carrier temperature changes from free-carrier absorption and stimulated transitions strongly govern transient gain dynamics. The energy of the pump wavelength relative to the transparency point determines which processes dominate the transient response. Stimulated carrier cooling is observed for the first time in these materials.
Characterization of arsenic doping profile across the polycrystalline Si/Si interface in polycrystalline Si emitter bipolar transistors
Authors: Macaulay J. M. , Hull R. , Jalali B. , Magee C.
Published: July 2002

The combination of Z-contrast scanning transmission electron microscopy, transmission electron microscopy, and secondary ion mass spectroscopy allows the most accurate determination, to date, of the As doping profile across the polycrystalline Si/Si interface of an npn polycrystalline Si emitter bipolar transistor. We measure a peak in the As doping profile which is coincident with the polycrystalline Si/Si crystallographic interface and is approximately 40 Å full width at half-maximum. There is a uniform As dopant level in the polycrystalline Si emitter of 2×1020 cm−3 and an estimated maximum As concentration of 5×1020 cm−3 in the peak at the interface.
Electrical and optical properties of PbTiO3 thin films on p-Si grown by metalorganic chemical vapor deposition at low temperature
Authors: Yoon Y. S. , Kang W. N. , Yom S. S. , Kim T. W. , Jung M. , Kim H. J. , Park T. H. , Na H. K.
Published: July 2002

Metalorganic chemical vapor deposition of PbTiO3 using Pb (tmhd)2, Ti(OC3H7)4, and N2O via thermal pyrolysis at relatively low temperature (∼500 °C) was performed in order to produce PbTiO3 insulator gates with high quality PbTiO3/p-Si interfaces. Raman spectroscopy showed the several optical phonon modes of the PbTiO3/p-Si structure. The stoichiometry of the PbTiO3 films was observed by Auger electron spectroscopy. Room-temperature current-voltage and capacitance-voltage measurements clearly revealed metal-insulator-semiconductor behavior for the samples with a PbTiO3 insulator gate, and the interface state densities at the PbTiO3/p-Si were approximately 1011 eV−1 cm−2 at the middle of the Si energy gap.
Large observed exciton shifts with electric field in InGaAs/InGaAsP stepped quantum wells
Authors: Tütken T. , Hawdon B. J. , Zimmermann M. , Hangleiter A. , Härle V. , Scholz F.
Published: July 2002

We report the experimental realization of asymmetric stepped InGaAs/InGaAsP quantum wells. The structure was designed to optimize the quantum-confined Stark shift. We have observed a shift of 30 meV in the heavy hole exciton absorption peak over an electric field change of 50 kV/cm. This shift is double that observed for the same structure without the stepped wells.
Directional isothermal growth of highly textured Bi2Sr2CaCu2Oy
Authors: Holesinger T. G. , Miller D. J. , Viswanathan H. K. , Dennis K. W. , Chumbley L. S. , Winandy P. W. , Youngdahl A. C.
Published: July 2002

For Bi2Sr2CaCu2Oy (2212), it is shown that an oxygen gradient, as opposed to a temperature gradient, can be used to produce large bulk forms of the 2212 superconductor with highly textured microstructures from an oxygen-deficient melt held at a constant temperature. Material produced in this manner was found to have transition temperatures between 85 and 92 K, high critical current densities below 20 K, and modest critical current densities at 77 K.
Fabrication and Raman scattering studies of one-dimensional nanometer structures in (110) silicon
Authors: Chu An-Shyang , Zaidi Saleem H. , Brueck S. R. J.
Published: July 2002

A simple technique for fabricating large fields of uniform nm scale Si structures is reported. This technique makes use of the highly anisotropic etching rates of KOH:H2O solution (40 wt. %) in Si (400:200:1=〈110〉:〈100〉:〈111〉). A large field of uniform sub-μm thick walls, along the 〈112〉 direction, is generated on a (110) Si sample coated with Si3N4 and photoresist films, by standard interferometric lithography techniques. The developed photoresist grating pattern is transferred into the Si3N4 layer by isotropic CF4 plasma etching. Finally, the nitride layer serves as an etch mask for the anisotropic chemical etch. Arrays of Si walls with pitch of 0.34 μm, sharp (110)–{111} corners, depths of 2.0 μm, and wall widths below SEM resolution limits are reported. The Raman scattering spectra of these structures shows shifted, asymmetrical line shapes; simple model calculations based on size-effect-induced relaxation of the usual Δk=0 momentum selection rule provide estimated wallwidths≤10 nm.
Nanosecond magneto-optic study of a new instability in thin YBa2Cu3O7−x films
Authors: Bujok V. , Brüll P. , Boneberg J. , Herminghaus S. , Leiderer P.
Published: July 2002

We have investigated the dynamics of flux penetration into thin superconducting YBa2Cu3O7−x films using a magneto-optic technique with nanosecond time resolution. For films carrying large shielding currents an instability in the magnetic flux distribution is discovered, which can be triggered by a local perturbation, e.g., by a focused laser pulse. The instability develops in the form of fine ramified flux structures, with a propagation speed of the flux front on the order of 5×104 m/s.
Strain effect on the optical nonlinearity in an InGaAs/GaAs asymmetric Fabry–Perot modulator
Authors: Moloney M. H. , Heffernan J. F. , Hegarty J. , Grey R. , Woodhead J.
Published: July 2002

The effect of strain on the optical nonlinearities and operation of an all-optical asymmetric Fabry–Perot étalon is investigated. A high reflectivity modulation of 60% is reported with a contrast ratio of 12.2:1 and insertion loss of 1.87 dB. High contrast is achieved through absorption matching requiring a thick active layer. The effect of a thick structure on the strain reduced saturation carrier density is measured. The saturation density is calculated to be a factor of 2.5 less than in a similar GaAs modulator, showing thicker strained devices still display the advantages of thinner structures.
‘‘Fast’’ and ‘‘slow’’ metastable defects in hydrogenated amorphous silicon
Authors: Yang L. , Chen L.
Published: July 2002

A two-step light soaking experiment at high and low intensities provided convincing evidence that defect generation and annealing in a-Si:H are controlled by defect states of different characteristics. We point out that the total defect by itself cannot uniquely determine the state of material or be described by a single rate equation, even though it might be the only quantity that is experimentally measurable. A system of rate equations for all defect components, therefore, must be established in order to accurately describe the defect kinetics. A simple two-component model in which defects are categorized as fast or slow is shown to be adequate to explain a variety of experimental results in a consistent fashion.
Metalorganic molecular beam epitaxial growth of high-quality Cd1−xZnxTe (0≤x≤0.27) films
Authors: Rajavel D. , Zinck J. J.
Published: July 2002

High-quality (001) Cd1−xZnxTe (0≤x≤0.27) films were grown by metalorganic molecular beam epitaxy on (001) GaAs substrates using thermally precracked dimethylcadmium, diethylzinc, and diethyltelluride. Cd1−xZnxTe/GaAs (0≤x≤0.05) films of 6–9 μm thickness exhibited x-ray rocking curve full widths at half-maximum of 200–240 arcsec, and 290–350 arcsec was measured for Cd1−xZnxTe/GaAs (0.09≤x≤0.17). The crystalline quality for the range of x values (0≤x≤0.27) reported here surpasses that previously published in the literature. The 5 K photoluminescence spectra of the Cd1−xZnxTe layers were dominated by strong and sharp bound excitonic transitions. In addition, the free excitonic transition was observed in Cd1−xZnxTe layers with 0≤x≤0.06. Secondary ion mass spectrometry measurements showed that the films were free of O and C contamination.