bluuebunny/crossref_metadata_2025 huggingface dataset:
Dye lasers generating two wavelengths simultaneously with a large wavelength separation
Authors: Ishikawa Kazuhito , Muto Shinzo , Matsuzawa Hidenori
Published: July 2002

A new type of dye laser which was pumped with N2 lasers and which generated two wavelengths simultaneously with separation in wavelength as much as 170 nm was shown experimentally. The laser cavity consisted of an output mirror, a grating, two dye cells containing different dye solutions, and a liquid prism having a small top angle (5° or 10°). Farther separation in wavelength is achievable when combinations of dyes and a prism of a larger top angle are chosen.
Broadband (6 GHz) GaAs/AlGaAs electro-optic modulator with low drive power
Authors: Walker R. G.
Published: July 2002

A GaAs/AlGaAs Mach–Zehnder modulator using a push-pull drive configuration is reported. The bandwidth/drive-voltage figure of merit is approximately double that of an equivalent single-sided device and is the highest reported for any non-traveling-wave structure. Vπ is 9 V at 1150 nm. Using unterminated drive a bandwidth of 6.25 GHz is achieved.
Application of position sensitive atom probe to the study of the microchemistry and morphology of quantum well interfaces
Authors: Liddle J. A. , Norman A. G. , Cerezo A. , Grovenor C. R. M.
Published: July 2002

The morphology and microchemistry of interfaces in GaInAs/InP quantum well structures have been studied with extremely high resolution by the new technique of position sensitive atom probe microanalysis. This letter presents some preliminary results demonstrating the power of the technique in determining the structure and chemistry of individual interfaces in multilayer epitaxial semiconductor samples.
Defect structures in laser-fused Si-SiO2 wafers
Authors: Geyselaers M. L. , Haisma J. , Widdershoven F. P. , Michielsen Th. M. , Reader A. H.
Published: July 2002

A silicon-on-silicon dioxide structure (silicon-on-insulator) produced by combined ‘‘van der Waals’’ bonding and laser fusing has been studied by cross-sectional transmission electron microscopy. Areas in the silicon corresponding to the regions which are locally melted by the laser beam were found to contain a high density of dislocations after fusing. The radius and depth of these defect areas, as observed in the microscope, are compared with a simple analytical model of the laser-induced melting process.
Scaling size distribution of oxide defects, trema-fractal oxide layer, and breakdown statistics of metal-oxide-semiconductor devices
Authors: Yadava R. D. S.
Published: July 2002

The extreme value distribution, characteristic of the defect-related dielectric breakdown in thin SiO2 films, is derived by assuming that (i) the defects are Poisson distributed in space with their mean densities scaling with their sizes as D(a)∼a−γ, where D(a) is the total density of defects having sizes more than a and γ is a constant, and (ii) the dielectric strengths of weak spots associated with the defects are logarithmically related to their sizes as E∝−ln a. It is argued that γ<1. This implies that the defect-free region of the oxide film is a non-self-similar random fractal with fractal dimension df =2 and topological dimension dt =1.
Effects of amorphous silicon capping layer on arsenic redistribution during TiSi2 formation
Authors: Kang S. W. , Chun John S. , Park S. C.
Published: July 2002

During titanium silicide (TiSi2) formation by rapid thermal annealing (RTA), the redistribution of implanted arsenic was investigated by means of Auger electron spectroscopy (AES) and secondary-ion mass spectroscopy (SIMS). By using 30 nm amorphous silicon (a-Si) film deposited sequentially on 50 nm titanium film without breaking the vacuum, the As dopant redistribution is suppressed due to the reduction of consumption of silicon substrate (Si-sub) during TiSi2 formation. The AES shows that the silicon, which is required for TiSi2 formation, is supplied from the a-Si film more rapidly than from the Si-sub. Also, the conversion of deposited Ti film into TiSi2 is complete because the a-Si film on Ti film prevents the infiltration of oxygen impurity into the Ti film during the exposure to air before annealing.
Transport critical current density in Bi2Sr2CaCu2Ox single crystals
Authors: Shi Donglu , Tang Ming , Chang Y. C. , Jiang P. Z. , Vandervoort K. , Malecki B. , Lam D. J.
Published: July 2002

The transport crystal current density Jc has been measured in Bi2Sr2CaCu2Ox single crystals. With a voltage criterion of 1.0 μV/cm, current density measurements yield Jc values ranging from 300 to 1000 A/cm2 at 77 K and zero field, depending upon crystal quality. The crystals are grown by using a flux method and have a typical size of approximately 10×4×1.5 mm. X-ray diffraction, scanning electron microscopy, electrical resistivity, and magnetization shielding data are reported.
Initial stages of heteroepitaxial growth of InAs on Si (100)
Authors: Oostra Doeke J. , Smilgys Russell V. , Leone Stephen R.
Published: July 2002

Adsorption and desorption of In on partially and fully As-terminated Si(100) are investigated by laser-induced fluorescence detection and Auger electron spectroscopy using the methods of temperature programmed desorption and isothermal desorption. Desorption measurements show that As is bound to the surface more strongly than In. For In, a 2/3 order kinetic desorption mechanism is observed. This and Si Auger intensity attenuation measurements indicate a strong tendency for In to form three-dimensional islands on the As-terminated surface. The activation energy for In diffusion from the islands ranges from 1.5 to 1.9 eV, depending on the As coverage. The results have important implications for growth of InAs on Si(100).
Kinetics of pressure-dependent gradual degradation of semiconductor lasers and light-emitting diodes
Authors: Khait Yu. L. , Salzman J. , Beserman R.
Published: July 2002

A statistical kinetic model for gradual degradation of semiconductor lasers and light-emitting diodes under the influence of pressure is presented. Within the framework of this model, the rate coefficient for disordering atom jumps, K, and the operating lifetime of the device, τ, are explicitly given in terms of temperature, pressure, material parameters, and free-carrier concentration. We find that a compressive pressure reduces the effective activation energy of the rate process and therefore accelerates degradation in GaAs- and InP-based devices.
Low-threshold PbEuSeTe double-heterostructure lasers grown by molecular beam epitaxy
Authors: Feit Z. , Woods R. , Kostyk D. , Jalenak W.
Published: July 2002

Lattice-matched double-heterostructure (DH) PbEuSeTe lasers were grown by molecular beam epitaxy (MBE) on (100) oriented PbTe substrates. Grooved mesa structures with 17–25 μm wide stripes and 0.75 μm thick Pb1−xEuxSeyTe1−y active layers with 0≤x≤0.031 were fabricated. DH diode lasers with a PbTe active layer reached a maximum cw operation temperature of 175 K which equals the highest operation temperature achieved so far by a side optical cavity (SOC) single quantum well (SQW) PbTe/PbEuSeTe laser. The threshold current density of 3.9 A/cm2 measured for this laser at 15 K is, to our knowledge, the lowest ever published for lead salt lasers. Comparison of MBE-grown DH lasers which utilize the lattice-matched PbTe/PbEuSeTe system to those utilizing the nonlattice-matched PbSe/PbEuSe system shows higher operation temperatures and by far lower threshold currents for the lattice-matched system.
Low-threshold grating-coupled surface-emitting lasers
Authors: Welch D. F. , Parke R. , Hardy A. , Streifer W. , Scifres D. R.
Published: July 2002

The high threshold current densities of single quantum well separate confinement heterostructure grating-coupled surface-emitting lasers are shown to result from a combination of inadequate gain in the lowest quantum state and the wavelength selective properties of the grating reflectors. The situation is aggravated by the saturable absorption loss in the grating sections and sizeable scattering losses at the etch step between gain and grating regions. Grating-coupled surface-emitting lasers with 50-μm-wide broad-area double quantum well active regions are reported with threshold currents reduced by a factor of 3 and with improved differential efficiency. Measurements of gain saturation of single quantum wells are presented.
Reproducible growth of low-threshold single and multiple quantum well InGaAs/InP lasers by a novel interlayer growth technique
Authors: Tanbun-Ek T. , Temkin H. , Chu S. N. G. , Logan R. A.
Published: July 2002

High quality single (SQW) and multiple (MQW) quantum well InGaAs/InP lasers have been realized for the first time utilizing a newly developed interlayer growth technique. The technique utilizes separate confinement SQW and MQW lasers grown by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE) having 10–20 nm InGaAs well(s) cladded by 50-nm-thick InGaAsP (λg=1.46 μm) waveguide layers. Carrier confinement and interfacial layer perfection are improved by growth of a few monolayers (∼1 nm) of InP at the QW-barrier interface and by using a novel flushing technique between growth of layers of different compositions. Both SQW and MQW lasers exhibit threshold current density of ∼2 kA/cm2. Buried-heterostructure lasers grown entirely by MOVPE in a two-growth step show threshold current of 18–40 mA and quantum efficiency as high as 21% facet with good linearity up to 15 mW.
Incident wavelength dependence of photocurrent bistability by external bias voltage control in a quantum well p-i-n diode
Authors: Tokuda Yasunori , Kanamoto Kyozo , Tsukada Noriaki
Published: July 2002

From external electric field dependence of photocurrent spectra of a quantum well p-i-n photodiode connected to a series resistive load, it is predicted and directly demonstrated that photocurrent bistability is obtained with respect to the variation of the external bias voltage when the device is illuminated by an incident ray in a certain wavelength region. Furthermore, additional self-consistent interpretation is given with empirical data taken for the system with no series resistor.
Tunable active chirped-corrugation waveguide filters
Authors: Schrans Thomas , Mittelstein Michael , Yariv Amnon
Published: July 2002

A novel tunable semiconductor waveguide reflection filter is proposed and analyzed. The filter is based on spatially selective gain pumping of a chirped-corrugation waveguide. This active chirped-corrugation waveguide filter (ACF) is considered for monolithic broadband tuning of semiconductor lasers.
Pseudomorphic ZnTe/AlSb/GaSb heterostructures by molecular beam epitaxy
Authors: Mathine D. L. , Durbin S. M. , Gunshor R. L. , Kobayashi M. , Menke D. R. , Pei Z. , Gonsalves J. , Otsuka N. , Fu Q. , Hagerott M. , Nurmikko A. V.
Published: July 2002

A series of pseudomorphic ZnTe/AlSb/GaSb epilayer/epilayer heterostructures, aimed at the realization of novel wide band-gap light-emitting devices, was grown by molecular beam epitaxy. The structures were evaluated by several techniques including transmission electron microscopy (TEM), x-ray rocking curves, photoluminescence (PL), and Raman spectroscopy. Reflection high-energy electron diffraction intensity oscillations were observed during nucleation of ZnTe. The presence of dislocation-free pseudomorphic structures was confirmed by TEM. The PL spectra of ZnTe epilayers showed dominant near-band-edge features composed of free and shallow impurity bound excitons.
Comparison of quantum-confined Stark effect in interdiffused and abrupt GaAs/AlGaAs quantum wells
Authors: Ribot H. , Laruelle F. , Coldren L. A.
Published: July 2002

Photocurrent measurements at room temperature have been carried out on thermally interdiffused GaAs/AlGaAs multiple quantum well structures. Although quite comparable, the Stark shift (quantum-confined Stark effect) in the disordered well is smaller than in the as-grown well. These measurements are consistent with calculations of the electron–heavy hole displacement versus electric field for infinite and square well models for the as-grown well, as well as parabolic and error function well models for the disordered well. We observe that this displacement increases faster for the wells with graded barriers which fit the experimental disordered well. Consequently, the exciton binding energy is smaller, which is consistent with the reduction of the Stark shift revealed by the photocurrent measurements.
GaAs p-i-n photodiodes made by metalorganic chemical vapor deposition using tertiarybutylarsine and arsine
Authors: Serreze H. B. , Baumann J. A. , Bunz L. , Schachter R. , Esman R. D.
Published: July 2002

High-speed, 80-μm-diam, GaAs/Alx Ga1−x As p-i-n photodiodes having frequency response in excess of 7 GHz and internal quantum efficiency approaching 100% were fabricated by low-pressure metalorganic chemical vapor deposition (MOCVD) using both tertiarybutylarsine (TBA) and arsine. These are the highest performance MOCVD GaAs devices achieved with nonarsine sources and comparable to the best reported p-i-n photodiodes of similar size. Net carrier concentration of the undoped TBA GaAs was determined by capacitance-voltage analysis to be less than 5×1014 cm−3 . Photoluminescence measurements indicate that undoped TBA-grown Alx Ga1−x As (x=0.25) is also of excellent quality (FWHM=12 meV). Growth conditions leading to optimized devices were found to be similar for the two sources.
Evaluation of AlOx barrier thickness in Nb Josephson junctions using anodization profiles
Authors: Imamura Takeshi , Hasuo Shinya
Published: July 2002

Using anodization profiles, we have analyzed the thin AlOxAl tunneling barrier in a Nb/AlOxAl/Nb Josephson junction. We measured the voltage width at the AlOxAl barrier in the profiles and found that it is closely related to the AlOxAl thickness. We proposed a way to evaluate this thickness from the voltage width. The anodization profile is useful in diagnosing the 4.2 K critical current density of Josephson junctions even at room temperature.
Acceptor-defect complexes in GaAs studied by perturbed angular correlation spectroscopy
Authors: Baurichter A. , Deicher M. , Deubler S. , Forkel D. , Plank H. , Wolf H. , Witthuhn W.
Published: July 2002

Acceptor-defect and acceptor-impurity complexes in GaAs have been studied by perturbed angular correlation spectroscopy. In n-type GaAs close Cd-S pairs were formed; the temperature dependence of the related electric field gradient indicates an electrically inactive Cd-S complex. After a hydrogen plasma exposure of GaAs a distinct Cd-defect complex has been observed. Similarly, plasma-induced configurations were also formed in InP and GaP.
Subpicosecond pulse generation from an all solid-state laser
Authors: Keen S. J. , Ferguson A. I.
Published: July 2002

We describe an all solid-state (holosteric) laser source which produces subpicosecond pulses at 1.4 μm. The system consists of a diode laser pumped Nd:YAG laser which is frequency modulated (FM) mode locked and Q switched at 1.32 μm. In continuous wave operation the laser produces pulses of 19 ps while simultaneous Q switching and mode locking result in 30 ps pulses being contained in a Q-switched envelope of energy 2.1 μJ. The output of the laser, when passed through a 1 km single-mode optical fiber, produces a spectrally broad Raman signal with its peak at 1.4 μm and the overall conversion efficiency at 12%. The pulse duration at 1.4 μm has been measured to be 280 fs. We believe this is the first time that subpicosecond light pulses have been generated by an all solid-state laser system.
High doping of phosphorus in Si using gas source molecular beam epitaxy
Authors: Hirayama Hiroyuki , Tatsumi Toru
Published: July 2002

Phosphorus doping using PH3 in gas source Si molecular beam epitaxy was studied. High phosphorus doping up to 2×1020 cm−3 was successfully achieved. The phosphorus concentration in the epitaxial layer was proportional to the PH3 flow rate. Moreover, selective growth of the phosphorus-doped layer was possible. The p-n diode, which consisted of a selectively grown phosphorus-doped layer, a p−-Si (100) substrate, and a SiO2 sidewall, showed a normal I-V characteristic.
Magnetoreflectivity study of excitons in (Zn,Co)Se epilayers
Authors: Liu X. , Petrou A. , Jonker B. T. , Prinz G. A. , Krebs J. J. , Warnock J.
Published: July 2002

The reflectivity spectra from single-crystal epilayers of the diluted magnetic semiconductor Zn1−x Cox Se(x=0.0076, x=0.0104) have been studied as functions of magnetic field and temperature. The excitonic spin splitting in these crystals saturates for magnetic fields B>5 T, indicating that (Zn,Co)Se is a Brillouin paramagnet, in agreement with magnetization and electron-paramagnetic-resonance studies on the same samples. The magnetoreflectivity data yield a value for the exchange parameter difference N0 (α−β)=2420±40 meV, significantly larger than the values obtained for either Fe- or Mn-based diluted magnetic semiconductors studied to date.
Effect of Pb and Sb substitutions on superconducting Bi-Sr-Ca-Cu-O prepared by oxidation of liquid-quenched precursor alloys
Authors: Luo J. S. , Michel D. , Chevalier J-P.
Published: July 2002

We have produced a series of precursor alloys (Bi1−xPbx)2 Sr2Ca2Cu3 (0≤x≤0.5) by planar flow casting. After oxidation and annealing in air, essentially 2212 and 2223 phases are present. The proportion of the 2223 phase increases as x increases from 0 to 0.3, at which composition mainly the 2223 phase is obtained with Tc (ρ=0) =105 K, and Jc(100 K) ≊200 mA/cm2 . More Pb addition reduces the amount of the 2223 phase and yields Ca2 PbO4. With Sb addition, a higher T(onset) ) near 125 K is obtained for (Bi0.85Pb0.10Sb0.05)2 Sr2Ca2Cu3Oy, corresponding to a multiphase material. A semiconducting behavior is observed when Sb≥10%.
Interface atomic structure of Si/SiO2/Si formed by molecular beam deposition
Authors: Sakai Akira , Tatsumi Toru , Niino Taeko , Hirayama Hiroyuki , Ishida Koichi
Published: July 2002

The interface structures of SiOx/Si and Si/SiOx/Si (x≂2) formed by molecular beam deposition (MBD) were examined by high-resolution transmission electron microscopy. The MBD SiO2/Si buffer layer interface was atomically flat in both samples. On the other hand, the Si overlayer/MBD SiO2 layer interface had a rough configuration. In the Si/SiO2/Si sample with a 7.5-Å-thick SiO2 buried layer, the polycrystalline Si overlayer was separated from the Si buffer layer by the thin SiO2 layer. A 2.5 Å reduction of the SiO2 buried layer thickness to 5.0 Å led to the epitaxial growth of the Si overlayer. In this sample, the SiO2 layer formed island morphology and epitaxial information was given to the overlayer through the exposed surface of the buffer layer. The epitaxial growth mechanism of the Si overlayer was also discussed.
Laser photochemical deposition of germanium-silicon alloy thin films
Authors: Burke Hubert H. , Herman Irving P. , Tavitian Viken , Eden J. Gary
Published: July 2002

Thin films of Ge-Si alloys were deposited by 193 nm photolysis of GeH4/Si2H6 gas mixtures using an ArF laser. For substrate temperatures below 350 °C, deposition occurred only with the laser present, while for temperatures above 400 °C, film growth was little influenced by laser photolysis and resembled conventional chemical vapor deposition (CVD). The Si/Ge ratio in the films was about three times the PSi2H6/PGeH4 ratio of reactant partial pressures for deposition in either the laser photolysis or the CVD regime. This result indicates that there is strong cross chemistry between silicon and germanium-bearing species in the gas phase. Film stoichiometry was measured by Auger analysis and Raman spectroscopy, with both methods leading to the same film composition.
Transfer of patterns from the backside of a silicon wafer coated with Si3N4 to its front surface during wet oxidation
Authors: Rogers W. Boyd , Massoud Hisham Z.
Published: July 2002

Patterns on the backside of silicon wafers coated with Si3N4 films have been observed on their front surfaces after wet oxidation. This pattern transfer phenomenon is the result of a reduction in the oxidation rate of the front-surface nitride film over areas where the backside films have been removed. This reduction has been attributed to the influence of the stress in the nitride film on its oxidation rate. In areas where the backside nitride has been removed, localized sample bowing results in stress relief in the front-surface film and a lower oxidation rate of the nitride film.
Electromagnetic acoustic head waves in piezoelectric media
Authors: Liu Yuan , Wang Cheng-hao , Ying C. F.
Published: July 2002

A transient line source, either mechanical or electrical, on the surface of a piezoelectric medium will excite electromagnetic acoustic (EMAC) head waves between quasi-electromagnetic surface disturbances and quasi-acoustic waves. EMAC head waves are acoustic in nature, with plane fronts practically parallel to the surface and traveling at acoustic speeds. One such plane wave front is observed experimentally in a thick lead titanate-zirconate plate in accordance with theory.
Wave front reversal in acoustic phase conjugation by nonlinear electroacoustic interaction in LiNbO3
Authors: Ohno Masahiro
Published: July 2002

Acoustic phase conjugate waves were generated at a frequency of 50 MHz by nonlinear electroacoustic interaction in LiNbO3 and their wave front reversal property was experimentally examined. The wave front of the incident acoustic wave was deformed by inserting a phase object in the beam path, but the phase conjugate wave after retracing the path showed little influence of deformation.
Zone-melting recrystallization with enhanced radiative heating for preparation of subboundary-free silicon-on-insulator thin films
Authors: Chen C. K. , Im J. S.
Published: July 2002

A new zone-melting-recrystallization (ZMR) configuration with enhanced radiative heating has been developed for preparing silicon-on-insulator (SOI) films. With this configuration, in which the sample is positioned above the movable heater with the SOI film facing downward, subboundary-free 0.5-μm-thick SOI films are obtained over a much wider range of experimental parameters than with the conventional ZMR configuration. The characterization of these films by defect etching, optical microscopy, and transmission electron microscopy shows that the principal defects are isolated threading dislocations with a density of ∼106 cm−2. It should be possible to improve the material quality still further by optimizing experimental conditions for the new configuration.
InGaAs/InP graded-index quantum well lasers with nearly ideal static characteristics
Authors: Temkin H. , Tanbun-Ek T. , Logan R. A. , Lewis J. A. , Dutta N. K.
Published: July 2002

We have examined static properties of step and continuously graded single and multiple quantum well InGaAs/InP lasers grown by atmospheric pressure metalorganic vapor phase epitaxy. Systematic changes in the band gap of InGaAsP waveguide layers have resulted in lasers with low threshold current (<10 mA), high quantum efficiency (26% per facet) and power output (∼70 mW), and the effective loss of 2–5 cm−1. We show that the changes in threshold current in short lasers can be explained by a switch from the n=1 to n=2 level. The level switching results in a very flat and wide (>1000 Å) gain profile.
Low-temperature (10 K) photoluminescence of Ga1−xInxPyAs1−y quantum wells grown by metalorganic chemical vapor deposition
Authors: Ludowise M. J. , Biswas D. , Bhattacharya P. K.
Published: July 2002

Ga1−x Inx As1−y Py /InP (x=0.72, y=0.39) lattice-matched quantum wells (QWs) are grown by low-pressure metalorganic chemical vapor deposition on (100) and 3° misoriented substrates, using different variations of growth technique. Low-temperature (10 K) photoluminescence is used to characterize the QWs. We find that substrates oriented closely to (100) (no intentional misorientation) produce QWs of consistently higher quality as judged by the width of the n=1 photoluminescence peak. The use of growth interruptions at the well interfaces severely degrades the QW quality. The narrowest peak observed is 5.8 meV wide from a 70-Å-wide well.
Organometallic chemical vapor deposition of InP/InGaAsP on nonplanar InP substrates: Application to multiple quantum well lasers
Authors: Bhat R. , Kapon E. , Werner J. , Hwang D. M. , Stoffel N. G. , Koza M. A.
Published: July 2002

We report the growth of InGaAs and InGaAsP quantum well heterostructures on InP substrates with [011̄] oriented grooves. We have shown that growth of these materials on non-planar substrates can result in lattice-mismatched layers on orientations other than (100) which in some cases gives rise to dislocations. In addition, the lateral patterning of quantum wells and quantum wire-like structures has been demonstrated in this material system. Finally, a quantum well laser, wherein lateral patterning of the well thickness was achieved by growing in a flat-bottomed groove, was fabricated. Without any additional growth steps these lasers exhibit a single stable spatial mode due to the waveguide formed at the groove.
Range of slow positrons in metal overlayers on Al
Authors: Nielsen Bent , Lynn K. G. , Leung T. C. , Van der Kolk G. J. , Van Ijzendoorn L. J.
Published: July 2002

Polycrystalline Pd and amorphous PdTa films on Al substrates were studied by a variable energy positron beam and by Rutherford backscattering. Since positron diffusion in the overlayers is limited, the range follows directly from the Doppler broadening as a function of incident positron energy. To observe possible effects of positron backscattering, a sandwich of Al/Pd/Al was studied as well. It was found that the mean penetration depth is not described well by z̄(E)=A(μg/cm2)×En(E), if A and n are assumed to be material and energy independent.
Gain nonlinearities in semiconductor lasers and amplifiers
Authors: DeFonzo Alfred P. , Gomatam B.
Published: July 2002

A concise and fundamentally straightforward physical model that accounts for the nonlinear gain in both semiconductor amplifiers and lasers is presented. Calculations based on this model yield results that agree very well with observed transient gain recovery dynamics in semiconductor laser amplifiers. The value of the symmetric steady-state gain suppression factor is found to be β=1.67×10−23 m3 in good agreement with experiment. The model accounts for a wavelength dependence of the asymmetric part of the nonlinear gain observed in direct mixing experiments observed in semiconductor lasers.
Buried-ridge striped planar GaAlAs/GaAs lasers with a wide range of effective index steps
Authors: Lee Song Jae , Ramaswamy Ramu V. , Zory Peter S. , Figueroa Luis
Published: July 2002

A novel self-aligned buried-ridge striped planar (BRSP) GaAlAs/GaAs diode laser structure is presented. The structure was grown by two-step liquid phase epitaxy using preferential growth and melt etch. A Ga1−y Aly As layer with a wide range of Al concentration (y>0.05) is selectively grown outside the ridge and can be an effective melt-etching mask. As a result, the BRSP structure can incorporate virtually all effective index steps, i.e., the positive, negative, and complex index steps. The threshold current of the BRSP structure is between 70 and 100 mA. The BRSP structure may prove to be of importance in the realization of linear array lasers.
Polarization-independent acoustically tunable optical filter
Authors: Smith D. A. , Baran J. E. , Cheung K. W. , Johnson J. J.
Published: July 2002

A polarization-independent acoustically tunable optical filter is described, with 1.3 nm bandwidth and 145 nm tuning range demonstrated about a center wavelength of 1525 nm. Filtered and unfiltered beams exit from different ports of this 2×2 integrated-optic structure fabricated on a LiNbO3 substrate. The filter conversion efficiency was 97% for unpolarized light, limited by imperfect splitting of the directional-coupler polarizing beamsplitters. Using an unpolarized, 105-nm-wide light-emitting diode as the optical source, 16 dB isolation of the filtered port was achieved, both with respect to the nearest nulls and the remote background spectrum.
Observation of silicon wafer emissivity in rapid thermal processing chambers for pyrometric temperature monitoring
Authors: Nulman J. , Antonio S. , Blonigan W.
Published: July 2002

The emissivity of silicon wafers in a rapid thermal processing chamber has been measured as a function of the wafer temperature. Wafers with different surface roughness and layers have been studied. For transparent wafers, both sides of the wafer affect the emissivity. This emissivity is not only affected by surface roughness, but also by the layers deposited on the wafer. It has also been observed that while the emissivity increases rapidly as the temperature increases from its room value to 600 °C, the emissivity decreases with a slope of −8.89×10−5 °C−1 for temperatures larger than 600 °C.
Anomalous capacitance-voltage behavior due to dopant segregation and carrier trapping in As-implanted polycrystalline silicon and silicided polycrystalline silicon gates
Authors: Park K. , Batra S. , Lin J. , Yoganathan S. , Banerjee S. , Lee J. , Sun S. , Yeargain J. , Lux G.
Published: July 2002

This letter discusses the anomalous capacitance-voltage characteristics of As-implanted polycrystalline silicon and amorphous Si gate metal-oxide-semiconductor (MOS) structures fabricated with and without a TiSi2 layer. The effects of gate bias and process parameters such as annealing temperature, process details of silicide formation, and polycrystalline silicon grain microstructure on the capacitance-voltage (C-V) characteristics have also been studied. It is shown that insufficient As redistribution at 800 °C, coupled with carrier trapping at polycrystalline silicon grain boundaries and dopant segregation in TiSi2, causes depletion effects in the polycrystalline silicon gate and in turn, the anomalous C-V behavior. The depletion tends to increase the ‘‘effective’’ gate oxide thickness and thereby degrade MOS device performance. Higher temperature anneals (≥900 °C) are sufficient to achieve degenerate doping in the polycrystalline silicon gates and avoid the depletion effects.
Material-enhanced spatially dependent etch rate of SiO2 in CF4 reactive ion etching
Authors: Porkolab G. A. , Wolf E. D.
Published: July 2002

We report on the spatially dependent enhanced etch rate of SiO2 in a CF4 planar reactive ion etcher due to the presence of the compounds GaAs or InP, or the single elements Ti, V, Nb, Ta, Cr, Mo, W, Ni, Pd, Pt, Cu, Ag, Au, Al, Ga, In, or Ge. The etch rate enhancement is maximum immediately adjacent to the source of the material and decreases nonlinearly with increasing distance away from the source of the material. Of the materials studied, the largest local etch rate increase was due to the element Ni (65% increase), followed closely by the elements In (57%) and Ga (43%) and the compounds InP (55%) and GaAs (40%). The lateral range of the effect extends 5 to 30 mm away from the material depending on the element or compound. Material interaction, possibly a catalized reaction, with the CF4 plasma reactants and lateral transport to provide an increased local concentration of fluorine at the SiO2 surface is a preliminary suggestion for the observed etch rate increase.
Gain characteristics of erbium-doped single-mode fiber amplifiers operated at liquid-nitrogen temperature
Authors: Shimizu Makoto , Yamada Makoto , Horiguchi Masaharu , Sugita Etsuji
Published: July 2002

Gain characteristics of Er-doped silica single-mode fiber amplifiers are investigated at liquid-nitrogen temperature (LNT). Liquid-crystal-polyester coated Er-doped fibers are used to prevent an increase in microbending loss of LNT. The maximum net gain and the transmission loss for a 1.535 μm wavelength are increased at LNT. This increase is explained by a three-level rate equation taking into account the loss increase. On the other hand, gain characteristics and the transmission loss at 1.552 μm suggest the change in the amplification mechanism at LNT from a three-level system to a quasi-four-level system.
Optical bistability in nonlocally nonlinear periodic structures
Authors: Assanto Gaetano , Stegeman George I.
Published: July 2002

The transmission and reflection of electromagnetic guided waves by a periodic structure with a delocalized intensity-dependent nonlinearity was studied using a semianalytical approach. We show that such a nonlocal nonlinear distributed feedback grating can exhibit bistable and switching behaviors depending upon the input intensity and the detuning.
High-efficiency intracavity frequency doubling of Ti:Al2O3 lasers with KNbO3 crystals
Authors: Wu L. S. , Looser H. , Günter P.
Published: July 2002

A tunable coherent blue light source with a tuning range of 430–470 nm has been built. Tunable blue radiation was obtained by intracavity frequency doubling of a Ti:Al2O3 laser in KNbO3 crystals. The titanium sapphire laser was operated in a pulsed mode pumped by the second harmonic of a Q-switched Nd:YAG laser. An infrared to blue conversion of 45% and a total conversion efficiency (532 nm to tunable blue) of 2% were reached.
Long-lived dry-etched AlGaAs/GaAs ridge waveguide laser diodes
Authors: Harding C. M. , Waters R. G.
Published: July 2002

Chemically assisted ion beam etching has been utilized to fabricate ridge waveguide GaAs/AlGaAs lasers which are as reliable, if not more so, than their oxide stripe counterparts. Results on 60- and 5-μm-wide ridge waveguide lasers with 600 μm cavity lengths as compared to oxide stripe lasers with the same configuration are reviewed and multikilohour lifetimes are demonstrated.
Analysis of thin rod flexural acoustic wave gravimetric sensors
Authors: Jen C. K. , Oliveira J. E. B. , Yu J. C. H. , Dai J. D. , Bussiere J. F.
Published: July 2002

An analysis of thin rod flexural acoustic wave gravimetric sensors is presented. The diameter of the thin rod is much less than a wavelength. The lowest order flexural acoustics mode, F11, is of interest. For small added masses, the calculated mass sensitivity is −1/(2ρa), where ρ is the density and a is the radius of the thin rod. Measurements of velocity dispersion of the F11 mode in 21-μm-diam gold wires are shown to agree well with the theoretical calculation. Devices based on thin rods are shown to potentially have the same advantages as plate-mode gravimetric sensors.
Formation of InxGa1−xAs/GaAs heteroepitaxial layers using a pulsed laser driven rapid melt-solidification process
Authors: Chang Y. , Chou S. Y. , Sigmon T. W. , Marshall A. F. , Weiner K. H.
Published: July 2002

Heteroepitaxial InxGa1−xAs/GaAs structures have been formed for the first time by pulsed laser induced mixing of molecular beam epitaxy deposited In films (∼200 Å) on GaAs (100) substrates. The process occurs by a melt-induced, rapid-mixing and solidification process driven by a XeCl pulsed excimer laser. The laser has a 27 ns full width at half maximum pulse width at 308 nm with its energy density of 0.28–0.61 J cm−2 homogenized into a 4×4 mm square area which is stepped across the wafer. InxGa1−xAs layers with x values, as determined by both x-ray diffraction and Rutherford backscattering spectrometry simulation ranging from x=0.21–0.26 and thicknesses of 77–94 nm, have been formed. The formation of single-crystal layers has been verified by 4He ion channeling and cross-section transmission electron microscopy.
Continuous-wave operation and mirror loss of a U-shaped GaAs/AlGaAs laser diode with two totally reflecting mirrors
Authors: Shimokawa Fusao , Tanaka Hidenao , Sawada Renshi , Hara Shigeji
Published: July 2002

A U-shaped GaAs/AlGaAs laser diode (LD) with totally reflecting mirrors is fabricated. Reactive fast atom beam etching technique with Cl2 gas is applied to fabricate the totally reflecting mirrors. Continuous-wave operation of the U-shaped LD with two totally reflecting mirrors is achieved using a graded-index separate-confinement-heterostructure single quantum well laser wafer. A threshold current of 75 mA and a light output power of over 5 mW are obtained with a 40-μm-wide and 300-μm-long mesa stripe structure. Totally reflecting mirror loss is estimated from measurements of the threshold current density for different cavity lengths. The loss of the totally reflecting mirror is about 0.95 dB per reflection.
High-reliability silicon microchannel submount for high average power laser diode arrays
Authors: Beach R. , Mundinger D. , Benett W. , Sperry V. , Comaskey B. , Solarz R.
Published: July 2002

A simple and highly reliable package consisting of a 1-cm-long AlGaAs laser diode array mounted directly on a silicon microchannel cooler has been demonstrated. 3.4×109 shots were logged on this device at an average optical output of 8.75 W with only a 6% increase in current required to hold the light output constant. This extrapolates to a current doubling lifetime of 1.6×1011 shots. The thermal impedance was also measured to be 0.014 °C/(W/cm2).
Ti silicide formation on thin-film silicon on insulator
Authors: Lin Chenglu , Zhou Wei , Zou Shichang , Hemment P. L. F.
Published: July 2002

In this letter the formation of Ti silicide on thin-film silicon on insulator has been investigated. The experimental results indicated that uniform TiSi2 layers with a low sheet resistance of 4.0–4.5 Ω/⧠ can be formed on thin-film silicon on insulator with a high carrier concentration of 2×1020/cm3. So a structure of Ti/n+-Si/SiO2/Si can be obtained. Secondary-ion mass spectrometer profiles of the As showed that a relatively homogeneous redistribution of the As in the TiSi2 layer is revealed and the As pileup at Si/SiO2 interface is noticeable when the thickness of the silicon overlayer after the TiSi2 formation is less than 520 Å.
Depth profiling of a silicon nitride layer by 20 keV N+2 ion implantation through an oxide layer as seen by x-ray photoelectron spectroscopy
Authors: Ermolieff A. , Molle P. , Marthon S.
Published: July 2002

The chemical composition profile of a nitride layer obtained by 20 keV N+2 ion implantation through an oxide layer was determined by x-ray photoelectron spectroscopy at two different analysis angles. The nitrogen concentration shows a plateau followed by a slow decrease. Oxygen, presumably due to a recoil implantation, is always present in the nitride layer in exponentially decreasing amounts. The film is composed of elemental silicon, silicon oxynitride, and diffused oxygen. The respective concentrations of the two silicon components are nearly constant and the diffused oxygen decreases. In the interface region, the oxynitride loses its oxygen progressively; at the very end of the interface, nitrogen seems to be partially chemisorbed. In a sample which has undergone a double annealing, the oxygen diffuses deeper in the bulk of the substrate.
Crystallization of amorphous Bi cuprate fibers to superconducting Bi2Sr2Ca1Cu2O8
Authors: Miller T. A. , Sanders S. C. , Ostenson J. E. , Finnemore D. K. , LeBeau S. E. , Righi J.
Published: July 2002

The conversion of long slender filaments of Bi-based high-temperature superconductors from the amorphous to the crystalline phase has been studied in order to determine the suitability of these fibers for use in a multifilamentary magnet conductor. For very fine filaments, coarsening may be a problem, so special emphasis was placed on the optimum values of time and temperature used for recrystallization. Amorphous fibers approximately 1 μm in diameter can be crystallized to form granular filaments about 0.2 μm thick (in the c direction) and 3 to 4 μm wide. The c axis generally grows perpendicular to the long axis of the fiber.
Cathodoluminescence study of the damage induced by low-energy boron implantation using a chemical bevel
Authors: Papadopoulo A. C. , Dubon-Chevallier C. , Pougnet A. M. , Krauz P.
Published: July 2002

Boron implantation is used in AlGaAs/GaAs heterojunction bipolar transistor fabrication technology in order to eliminate the lateral diode between the n+-GaAs emitter contact layer and the p+-GaAs implanted well. The cathodoluminescence intensities measured on a bevel before and after the implantation have been investigated to evaluate the amount of damage induced by low-energy implantation in the underlying AlGaAs emitter layer.
Elastic accommodation of heteroepitaxial InSb films on GaAs
Authors: Rajan K. , Gong R. , Webb J.
Published: July 2002

Heteroepitaxial films of InSb on GaAs (100) grown by metalorganic magnetron sputtering have been studied by transmission electron microscopy. The elastic strain in the InSb films has been measured using Moiré fringe analysis. Dilational lattice strain was found to decrease with increasing film thickness. The measured strains are in general agreement with a simple strain energy criterion for elastic accommodation. The application of a coincidence site lattice model for heteroepitaxy is also discussed.
Tl2Ca1Ba2Cu2O8+x high Tc superconductors processed by the sol-gel technique
Authors: Kordas G. , Teepe M. R.
Published: July 2002

Tl2Ca1Ba2Cu2O8+x high Tc superconductors were developed using a new alkoxide sol-gel system. Barium-, calcium-, thallium-methoxyethoxide and Cu(II) ethoxide precursors were used for the formation of homogeneous sols. Solubility of the Cu(II) ethoxide was aided by using a 2-methoxyethanol/methyl ethylketone/toluene solvent system. The sols were characterized by small-angle x-ray scattering and transmission electron microscopy. The average particle size was 50 nm and the fractal dimension of these particles was 1.8. Powders were produced by rotary evaporation followed by thermal treatment in a closed container with excess thallium at 900 °C for various calcination times. Powders were characterized by x-ray diffraction, resistivity, and magnetic susceptibility measurements, and chemical analysis. Samples exhibited transition temperatures between 100 and 110 K depending upon the processing conditions.
Integrated-optic polarization controller with unlimited transformation range
Authors: Heismann F. , Divino M. D. , Buhl L. L.
Published: July 2002

We demonstrate a novel waveguide polarization controller that allows endless transformations from any varying general input polarization state into any varying general output state. The electro-optic controller is implemented in lithium niobate and produces adjustable elliptical birefringence of constant total phase retardation via three independent drive voltages. We show that it allows fast and reset-free automatic polarization control using an entirely analog feedback circuit that derives its error signal from the intensity in the prescribed output polarization.
Stable single mode operation of grating-surface-emitting laser arrays under frequency-modulated operation
Authors: Carlson N. W. , Bour D. P. , Evans G. A. , Amantea R. , Liew S. K.
Published: July 2002

Direct frequency-modulated operation of ridge-guided linear grating-surface-emitting laser arrays is reported. Simultaneous far-field and spectral measurements of these devices at 1 GHz modulation rates show that both single longitudinal mode and single spatial mode operation are maintained.
High-reflectivity self-pumped phase conjugator using total internal reflection in KNbNO3:Fe
Authors: Zhang He-Yi , He Xue Hua , Chen Erli , Liu Yue , Tang Sing Hai , Shen De-Zheng , Jiang Da-Ya
Published: July 2002

A self-pumped phase conjugate reflectivity of 74.8% is obtained with a suitably cut KNbO3:Fe crystal in a polygonal shape. The design and operation of this self-pumped phase conjugator is described. The build-up time is observed to be dependent on the input power. The phase conjugate nature of the retroreflected beam has been further confirmed by a significant decrease in the specular reflectivity of the input surface of the crystal.
Monolithic InGaAs p-i-n InP metal-insulator-semiconductor field-effect transistor receiver for long-wavelength optical communications
Authors: Mattera V. D. , Antreasyan A. , Garbinski P. A. , Temkin H. , Olsson N. A. , Filipe J.
Published: July 2002

We have fabricated a monolithically integrated p-i-n field-effect transistor (FET) receiver consisting of an InGaAs/InP p-i-n detector and a high-speed InP metal-insulator-semiconductor field-effect transistor. The receiver sensitivity of the p-i-n FET is −18.2 dBm at a bit rate of 2.4 Gb/s and a wavelength of 1.55 μm.
Monte Carlo simulation of mode-locked semiconductor diode lasers
Authors: Werner J. , Lee T. P.
Published: July 2002

We report on results of a Monte Carlo simulation that uses traveling-wave equations for the optical field of mode-locked diode lasers. The model includes effects of the spontaneous emission, the linewidth enhancement factor, and nonlinear gain. The results of the simulation agree with experimental observations such as the sublinear power versus current characteristics. According to this model the reduced power is a result of combined large-signal effects. We propose to incorporate a frequency shifter into the cavity to improve the pulse energy and the use of available bandwidth.
Half-ring geometry quantum well GaAlAs lasers
Authors: Bar-Chaim Nadav , Lau Kam Y. , Mazed M. A. , Mittelstein Michael , Oh Se , Ungar Jeffrey E. , Ury Israel
Published: July 2002

Half-ring geometry single quantum well GaAlAs lasers have been fabricated. These lasers rely on a single cleave to obtain both resonator end reflectors. Using a buried-heterostructure waveguide for lateral confinement and a high reflectivity facet coating, threshold currents as low as 14.5 mA and a frequency response extending to 6.5 GHz have been achieved.
GaAs multiple quantum well waveguide modulators on silicon substrates
Authors: Treyz G. V. , May P. G. , LaTulipe D. , Basu S. , Wang W. I.
Published: July 2002

We demonstrate modulation for GaAs multiple quantum well (MQW) waveguide modulators on silicon substrates. The modulators, which were fabricated by molecular beam epitaxy, were operated at wavelengths of 890–910 nm, with greater than 20 dB modulation obtained at λ=900 nm for a reverse bias of 2.5 V. Photocurrent measurements were performed on GaAs MQWs grown on Si and compared with results obtained for GaAs MQWs grown on GaAs. The structures were integrated with GaAs/AlGaAs waveguides and are suitable for integration with silicon-based electronics.
Heavily carbon-doped GaAlAs grown by vacuum chemical epitaxy
Authors: de Carvalho M. M. G. , Barreto C. L. , Cotta M. A. , Ito K. M.
Published: July 2002

Heavily p-doped GaAlAs layers have been grown on GaAs substrates by vacuum chemical epitaxy (VCE), using trimethylaluminum (TMA) as an aluminum source. Triethylgallium (TEG) and arsine were used as gallium and arsenic sources, respectively. Net carrier concentrations in the range 5×1019–2×1020 cm−3 and mobilities of ≂30–40 cm2/V s have been achieved. GaAlAs layers grown with triisobutylaluminum (TIBAl) as aluminum source have shown residual concentrations almost three orders of magnitude smaller, thus indicating a greater carbon incorporation associated to the use of TMA. The residual dopant concentration can be reduced by using a higher AsH3 flow or introducing H2 in a VCE reactor during growth, due to the easier methyl removal in these conditions.
Pulsed laser heating measurement of relaxation-induced melting point increase in amorphous Si
Authors: Grimaldi M. G. , Baeri P.
Published: July 2002

The difference in the melting temperature of unrelaxed and relaxed amorphous silicon has been determined by measuring the energy density threshold for surface melting during nanosecond laser irradiation (λ=347 nm). The melting onset was detected by time-resolved reflectivity technique. Using particular samples in which a surface unrelaxed layer was generated by reimplanting a 400-nm-thick relaxed amorphous Si (a-Si) the difference in the melting temperature has been determined independently of the thermal properties of the a-Si. The melting temperature of relaxed a-Si resulted to be only 3.9% higher than that of unrelaxed a-Si, while on the basis of calorimetric data an ∼14% difference was expected. The reasons for this discrepancy are discussed. In addition a 24% increase in the product of thermal conductivity and specific heat of a-Si upon relaxation has been found.