bluuebunny/crossref_metadata_2025 huggingface dataset:
Cr-Si-O film with a high chromium concentration for strain gauge
Authors: Yamadera H. , Taga Y.
Published: July 2002

We prepared a Cr-Si-O film by co-sputter deposition and evaluated the properties with a view to applying to a strain gauge. It was found that the maximum gauge factor of 8.7 was obtained in the 200-nm-thick film at the composition of Cr-1 at. % Si-19 at. % O. In addition, the temperature coefficient of resistance of the film was 8 ppm/°C in the temperature range of 25–120 °C and the fractional change in resistance after annealing was less than ±0.1% up to 400 °C.
Thermomechanical fracture instability and stick-slip crack propagation
Authors: Maksimov I. L.
Published: July 2002

A self-consistent approach is proposed for the first time to describe the fracture in viscous plastic media taking into account the energy dissipation near the crack tip. The conditions are found under which slow heat- and stress-stimulated crack propagation occurs. It is found that cracks of small size are unstable with respect to thermal and mechanical disturbances. It is shown that stick-slip fracture instability due to the energy exchange between mechanical and thermal modes can take place at a certain stage of crack propagation. An estimation is obtained for the number of slips in the course of discontinuous fracture.
Multiwafer growth of CdTe on GaAs by metalorganic chemical vapor deposition in a vertical, high-speed, rotating disk reactor
Authors: Tompa G. S. , Nelson C. R. , Saracino M. A. , Colter P. C. , Anderson P. L. , Wright W. H. , Schmit J. L.
Published: July 2002

Growth of CdTe (111) layers on GaAs (100) and GaAs (111) substrates by metalorganic chemical vapor deposition (MOCVD) has been investigated using a commercial, vertical, high-speed, rotating disk reactor. Dimethylcadmium (DMCd) and diisopropyltelluride (DIPTe) were used as the growth precursors. The growth rate was measured over the temperature range from 308 to 402 °C. DMCd molar growth efficiencies greater than 50% are obtained for growth temperatures greater than 368 °C. X-ray rocking curves for the (422) and (333) reflection planes of CdTe (111)<90 arcsec full width at half maximum were obtained at 380 °C for films on the (111) substrates. Scanning electron microscopy on cleaved wafers and infrared interference spectroscopy show edge-to-edge thickness uniformity to be 1.3%. The far-infrared reflectivity was measured using a Fourier transform infrared spectrometer to obtain the TO phonon spectra. These data indicate that the thickness and dielectric constant of the CdTe is extremely uniform. Overall, the films obtained in this study are more uniform and of higher quality than the best films produced in a horizontal reactor using similar growth procedures.
Damage profile of ion-implanted GaAs by x-ray photoelectron spectroscopy
Authors: Lu Z. H. , Azelmad A. , Trudeau Y. , Yelon A.
Published: July 2002

We report on the use of x-ray photoelectron spectroscopy for the investigation of radiation damage in GaAs. The technique has been used to profile the damage induced by 7 MeV Si+ ions. Arsenic displaced by the ions is found in an interstitial elementary state. Using chemical etching, we are able to trace the distribution of As displacement. The results are in good agreement with trim calculations of radiation damage. The potential applications of this technique to the study of the nature and distribution of radiation damage are discussed.
First observation of a titanium midgap donor level in In0.53Ga0.47As p-n diodes
Authors: Chen Z. , Korb W. , Bauer R. K. , Bimberg D.
Published: July 2002

Growth of Ti-doped In0.53Ga0.47As using liquid phase epitaxy is reported. The energy position of the Ti4+/Ti3+ deep donor level in In0.53Ga0.47As p-n diodes is precisely identified for the first time by deep level transient spectroscopy. The near midgap location of this level at EC−ET =0.37 eV and the potential of InGaAs:Ti of superior thermal stability make it a promising dopant for growing semi-insulating In0.53Ga0.47As. A recent model suggesting the energy positions of transition metals not to vary across heterojunctions is tested and found to be at least qualitatively valid for this low spin transition metal.
Hydrogenation of molecular beam epitaxial Ge0.36Si0.64 on Si
Authors: Xie Y. H. , Luftman H. S. , Lopata J. , Bean J. C.
Published: July 2002

Passivation of threading dislocations in an incommensurate Ge0.36Si0.64/Si structure is studied using hydrogen plasma anneal. The reverse current of pn junction diodes made of the above structure is reduced by more than 30 times after hydrogenation. Associated improvements in the current-voltage (I-V) characteristics is also observed. Capacitance-voltage (C-V) measurements reveal that the shallow dopants neutralized by hydrogenation reactivate at lower temperatures than the passivated deep level defects. Secondary-ion mass spectroscopy (SIMS) analysis established the depth of diffusion of hydrogen under the experimental conditions. Work in this direction could eventually lead to the integration of infrared detectors with Si very large scale integration (VLSI).
Carbon incorporation in ZnSe grown by metalorganic chemical vapor deposition
Authors: Giapis Konstantinos P. , Jensen Klavs F. , Potts J. E. , Pachuta Steven J.
Published: July 2002

Carbon incorporation in ZnSe films grown by metalorganic chemical vapor deposition is reported. Secondary-ion mass spectrometry measurements in ZnSe films grown from methylallylselenide and dimethylzinc show an enhanced carbon accumulation at the interface between ZnSe and GaAs. The carbon incorporation in the bulk ZnSe increases with the VI/II ratio and for a value of VI/II=3–4, the amount of incorporated carbon abruptly jumps to concentrations of 1021 cm−3, whereupon the films become polycrystalline. A new shallow peak IC at 2.7920 eV dominates the near-band-edge low-temperature photoluminescence spectra of all carbon-contaminated ZnSe films. The intensity and linewidth of IC increase with the VI/II ratio in a similar manner to the carbon concentration. This peak is proposed to be due to the radiative decay of excitons bound to a complex defect, which is associated with the presence of carbon in the films.
Wave function sweeping in AlxGa1−xAs-GaAs quantum wells
Authors: Ensslin K. , Heitmann D. , Ploog K.
Published: July 2002

Specially tailored gated AlxGa1−xAs-GaAs quantum well (QW) structures have been prepared, where it is possible to sweep the maximum of the electron wave function and, thus, the electron density via the gate voltage very effectively from the substrate side of the QW to the front side. In our structure this sweeping is so pronounced that it leads to a unique influence on the actual band structure and cyclotron resonance mass.
Far-infrared magneto-optical study of Hg1−xCdxTe superlattices with graded composition
Authors: Yang Z. , Dobrowolska M. , Luo H. , Furdyna J. K. , Cheung J. T. , Otsuka N.
Published: July 2002

Far-infrared magnetotransmission experiments were carried out on two Hg1−xCdxTe superlattices with graded composition grown by laser molecular beam epitaxy. A superlattice k⋅p model was used to calculate the subband structures of the superlattices. Good agreement is found between the experimental results and the theory if the valence-band offset is assumed to be small.
Magnetization and critical current density of the Bi-(Pb)-Sr-Ca-Cu-O tapes in magnetic fields
Authors: Sekine H. , Itoh K. , Inoue K. , Maeda H. , Numata K.
Published: July 2002

The Bi-(Pb)-Sr-Ca-Cu-O superconductor was fabricated into tapes with a Cu sheath. Measurements of magnetization and critical current density Jc in magnetic fields up to 23 T were made for them. The magnetization measurement revealed that, at 4.2 K, these tape specimens had excellent Jc -H(magnetic field) characteristics, while at 77 K, the flux pinning force in them was reduced to zero above 0.3 T due to the flux creep. In the resistive Jc measurement at 4.2 K, these tape specimens showed Jc of ∼7000 A/cm2 at 23. The Jc -H curve showed a slight peak effect, indicating the peak over 30 T.
Connection between linewidth saturation and power increase of transverse magnetic mode in ridge distributed feedback lasers
Authors: Sapia Adalberto , Spano Paolo , Mecozzi Antonio
Published: July 2002

We present some experimental results of ridge distributed feedback semiconductor lasers showing a linewidth broadening at high emission power which is due to the growth of transverse magnetic polarized radiation. We also show how the linewidth saturation can be ascribed to an increase in the low-frequency content of the phase noise spectrum. This increase at low frequency is also linked to a deformation in the probability distribution of the instantaneous optical emission frequency.
Breit–Wigner description of resonant tunneling
Authors: Coon D. D. , Bandara K. M. S. V. , Zhao H.
Published: July 2002

Analytic properties of scattering amplitudes are used to develop Breit–Wigner parametrizations of resonant tunneling currents in heterostructures. The analysis reveals a problem in using conventional Breit–Wigner resonance expressions to describe the important regions of peak current and negative differential resistance which occur when resonances are near the emitter threshold. Commonly used Breit–Wigner expressions (a) do not incorporate the correct threshold branch points, (b) do not possess the correct limit at threshold, and (c) do not satisfy unitarity both above and below threshold. Expressions which avoid such difficulties are deduced and used to parametrize tunneling current formulas.
Widely tunable semiconductor optical fiber ring laser
Authors: Oshiba Saeko , Nagai Kiyoshi , Kawahara Masato , Watanabe Akira , Kawai Yoshio
Published: July 2002

A wide tunable optical fiber ring laser with a diffraction grating as a tuning element is demonstrated. A wide tuning range over 100 nm is achieved using a high performance traveling-wave amplifier (TWA) as a gain medium. The TWA with a V-grooved inner stripe structure on a p substrate (VIPS structure) has a high peak gain over 30 dB and a broad gain width of 100 nm at 16 dB. The effects of the gain of TWA and the total loss of the external ring cavity on the tuning range are also discussed.
Infrared absorption and Raman scattering by plasmons in thin layers of GaAs grown by molecular beam epitaxy
Authors: Kirillov D. , Liu D. , Weng Shang-Lin
Published: July 2002

Infrared absorption at oblique incidence and Raman scattering were used to measure plasmon spectra in highly doped n-type GaAs layers grown by molecular beam epitaxy. Plasmon frequency was lower in infrared absorption spectra compared to Raman spectra of the same samples due to the wave vector dependence of the plasmon frequency. The linewidth of plasmon lines was quite similar in infrared absorption and Raman scattering spectra, indicating the small role of Landau damping for the studied range of wave vectors. Infrared plasmon absorption was strongly reduced for films thicker than the wavelength of plasmons, and the wave vector dependence was reduced for very thin films when the electron gas started to acquire quasi-two-dimensional character.
New-type xerographic multiduplication using organopolysilane-based memory photoreceptor drawn by ultraviolet image exposure
Authors: Yokoyama Kenji , Yokoyama Masaaki
Published: July 2002

Persistent image storage has been successfully performed in organopolysilane-based xerographic photoreceptors by ultraviolet image exposure, which converts organopolysilane into intrinsically insulating material with no charge carrier transporting ability due to photodecomposition. The stored image can be read out repeatedly as a negative toner image by the usual xerographic process with uniform visible light illumination, suggesting an application of the present photoreceptor to the xerographic printing master.
Tight-binding analysis on exciton binding energy in field-induced Stark-localized superlattices
Authors: Yan R. H. , Laruelle F. , Coldren L. A.
Published: July 2002

We use a variational calculation to study the excitonic behavior in a multiwell system. With several approximations, the exciton binding energy problem is reduced to a simple form, and the exciton binding energy is found to vary quadratically with the electron wave function confinement factor in the well with localized holes. This simple model is applied to explain quantitatively the localized exciton binding energy in a Stark-localized superlattice. It is found that a 50% electron wave function confinement factor is necessary to provide a strong excitonic effect in a multiwell system.
Photoluminescence of GaAs grown dilutely doped with Si by molecular beam epitaxy with modulated source supplies
Authors: Kamijoh T. , Sugiyama N. , Katayama Y.
Published: July 2002

GaAs layers grown dilutely doped with Si by molecular beam epitaxy (MBE) with modulated-source supplies have been characterized using low-temperature photoluminescence. Free- and bound-exciton emissions were observed in the near-band-edge region of photoluminescence spectra. A change in the spectral features of impurity-related emissions was induced by varying the modulation of the Si molecular beam in the MBE growth. It is found that the Si atoms are incorporated as either donors or acceptors, according to the timing of the Si supply during the As-source supply in MBE growth. We achieved Si doping on addressed sites by varying the timing of the Si supply.
Electron capture by D
X centers in AlGaAs and related compounds
Authors: Izpura I. , Muñoz E.
Published: July 2002

n-type dopants in Alx Ga1−x As, GaAs1−x Px, and related compounds create deep donors that control the free-electron concentration for x>0.2. The electron capture by the deep donors shows a very nonexponential dependence with filling time. In this letter the electron capture kinetics is modeled, and the influence of the donor ionization factor, sample degeneracy, and size effects, are introduced. Capture barrier energy determination is discussed, and a comparison with experimental capture data is made.
Barrier tuning by means of a quantum, interface-induced dipole in a doping layer
Authors: Müller G. , Zrenner A. , Koch F. , Ploog K.
Published: July 2002

We consider a sharply defined doping layer near the interface of a heterostructure on the narrow-gap side. It is shown that an interface-induced dipole moment results, whose magnitude depends on the quantum spread of the electronic charge. The result of thermionic emission measurement of the barrier height is compared with a self-consistent, nonparabolic subband calculation.
Offset criterion for determining superconductor critical current
Authors: Ekin J. W.
Published: July 2002

Critical-current criteria based on electric field or resistivity can present a number of problems in defining critical current, especially for high Tc superconductors in the vicinity of the critical temperature or upper critical field. The resulting critical-current density Jc can be quite arbitrary, since it depends strongly on criterion level at high fields and temperatures. These Jc definitions also create problems in distinguishing between superconductors and high-conductivity normal metals such as copper. They can also bias Jc data when superconductors are compared that have different values of normal-state resistivity. To minimize these problems, an intrinsic Jc criterion is proposed, which effectively separates superconducting and normal-state properties. Based on the long-standing concept of a flux-flow resistivity, Jc is defined as the current where the tangent to the E-J curve at a given electric field level extrapolates to zero electric field. This determines an offset Jc that minimizes the above problems. The criterion is particularly useful near Tc or near the effective upper critical field where the E-J characteristic starts to approach ohmic behavior.
Effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen
Authors: Engstrom J. R. , Bonser D. J. , Engel Thomas
Published: July 2002

The effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen has been examined under ultrahigh vacuum conditions by employing molecular beam techniques and x-ray photoelectron spectroscopy. Ion bombardment leads to a significant enhancement in the rate of oxidation. By modulating both the oxygen and ion (Ar+ ) fluxes several possible mechanisms for the enhanced rate can be eliminated. Of the remaining possibilities, a mechanism involving competition between ion-induced oxygen incorporation and sputtering appears most likely.
Synthesis of Bi-Pb-Sr-Ca-Cu oxide/Ag superconductors by melt dipping and oxidation of metallic precursor alloys
Authors: Gao W. , Li S-C. , Rudman D. A. , Yurek G. J. , Vander Sande J. B.
Published: July 2002

Bi-Pb-Sr-Ca-Cu-Ag alloy coatings were made by vacuum induction melting followed by melt dipping on substrates of MgO, SrTiO3, and Al2O3. The metallic precursor layers were then subjected to a controlled atmosphere oxidation and annealing to produce oxide superconductors. Superconducting coatings with onset temperatures of 112 K and zero resistance temperatures of 80 K were obtained in this way. The addition of Ag aided in the alloy melting and dipping processes, and produced a superconducting oxide/noble metal composite after oxidation. The resulting superconducting phases were analyzed by x-ray powder diffraction. The influence of the substrate, dipping processes, oxidation, and annealing conditions on the superconducting properties are discussed.
Shock-wave synthesis of a thallium-based superconductor with a novel defect microstructure
Authors: Iqbal Z. , Thadhani N. N. , Chawla N. , Ramakrishna B. L. , Sharma R. , Rao K. V. , Skumryev S. , Reidinger F. , Eckhardt H.
Published: July 2002

We report the shock-wave synthesis at a yield ≳80% by volume of the single copper layer thallium superconductor of composition Tl2Ba2CuO6. The as-synthesized material displays zero resistance near 55 K and a diamagnetic onset to bulk superconductivity at 70 K. Lattice imaging indicates that the superconducting microcrystals consist of a novel defect microstructure involving an intergrowth of two copper-oxygen layers probably interleaved by partial thallium and barium occupancy.
Bistable behavior of interface states in InP-anodic oxide-Al2O3-metal structures
Authors: Vuillaume D. , Zencirci N. , Garrigues M. , Viktorovitch P.
Published: July 2002

We report that part of the InP-anodic oxide interface states consists of bistable defects under two charge state configurations. Deep level transient spectroscopy measurements after positive, negative, or zero bias cooling of the samples from room temperature to 80 K are used. Slow states induced by defects in the anodic oxide layer are also characterized with a concentration in the range 1017–1018 cm−3. The effect of the slow states on the bistable behavior is analyzed. This bistable behavior is related to the modification of the Fermi level pinning after some bias stresses.
Protective films prepared by the electron cyclotron resonance plasma chemical vapor deposition technique for phase-change-type optical disks
Authors: Sugiyama Yasuyuki , Fujimori Susumu , Yamazaki Hiroki , Hatakeyama Iwao
Published: July 2002

Hydrogenated amorphous silicon carbide (a-SiC:H) films are prepared by the electron cyclotron resonance plasma chemical vapor deposition (ECR PCVD) technique. The films are, for the first time, applied as protective layers for phase-change-type optical disks. Three kinds of films with different hydrogen contents are investigated to improve writing sensitivity. The writing laser power required to obtain a sufficient carrier-to-noise ratio is 11 mW at a 10 m/s linear velocity, which corresponds to a 30% power reduction compared to conventional rf-sputtered ZnS protective layers. This is attributed to the decreased thermal conductivity of these protective layers. The hydrogen in the films is confirmed to be thermally stable.
Injection and drift of a positively charged hydrogen species in p-type GaAs
Authors: Tavendale A. J. , Pearton S. J. , Williams A. A. , Alexiev D.
Published: July 2002

Transport of the acceptor-passivating hydrogen species in p-type GaAs has been observed in reverse bias annealed Al Schottky diode samples. The motion of the positively charged hydrogen across the depletion region of these diodes is confirmed both by changes in the electrically active acceptor profiles with time, and by direct measurement of the migration using secondary-ion mass spectrometry on deuterated samples. Acceptor passivation is unstable under minority-carrier injection by illumination at 25 °C. Hydrogen injection into p-type GaAs during boiling in water or etching in H2SO4:H2O2:H2O has also been demonstrated.
Double-heterostructure optoelectronic switch as a single quantum well laser
Authors: Taylor G. W. , Cooke P.
Published: July 2002

The double-heterostructure optoelectronic switch (DOES) is demonstrated as an N-channel, single quantum well, graded index laser. As a broad-area device, the DOES exhibits excellent electrical switching characteristics of 12 V and 0.04 A cm−2 at the switching condition and 1.8 V and 3.3 A cm−2 at the holding condition with 8.4×10−4 Ω cm2 on state resistance. As a laser, threshold current densities down to 580 A/cm2, loss of 11 cm−1, slope efficiency of 0.35 mA/mW, and total power conversion efficiency of 45% were obtained.
Channeling scanning transmission ion microscopy
Authors: Cholewa M. , Bench G. , Legge G. J. F. , Saint A.
Published: July 2002

Scanning transmission ion microscopy (STIM) has been used, in conjunction with channeling, to explore transmission channeling in 50-μm-thick epitaxially grown n-type silicon with 3.9 MeV H+ beam currents of 0.1 fA focused to spot sizes of less than 200 nm. The technique is extremely efficient, causes negligible damage, and is capable of very high resolution. High-resolution images of crystal damage were obtained with this first demonstration of channeling contrast in STIM.
Molecular beam epitaxy of Zn1−xCdxSe epilayers and ZnSe/Zn1−xCdxSe superlattices
Authors: Samarth N. , Luo H. , Furdyna J. K. , Alonso R. G. , Lee Y. R. , Ramdas A. K. , Qadri S. B. , Otsuka N.
Published: July 2002

We have investigated the epitaxial growth of Zn1−x CdxSe epilayers and ZnSe/Zn1−x CdxSe superlattices (0≤x≤1) on (100)GaAs. Although thick epilayers of Zn1−x CdxSe are prone to defect formation with increasing Cd content, the structural and optical characteristics improve remarkably when Zn1−x CdxSe is  in the  form of  thin layers  within ZnSe/Zn1−x CdxSe  superlattices. High  quality superlattices  can be grown for x≤0.35. The characterization of these systems using transmission electron microscopy, x-ray diffraction, reflectivity, and photoluminescence is reported.
Correlation of modulated optical reflectance with silicon carrier lifetime and impurity concentration
Authors: Rozgonyi G. A. , Radzimski Z. J. , Kola R. R. , Smith W. L. , Bivas A.
Published: July 2002

Modulated optical reflectance imaging using a scanning dual laser apparatus is a new, nondestructive tool for the characterization of semiconductor surfaces. One can expect that semiconductor material parameters such as doping concentration, impurity and damage level, which influence the minority-carrier lifetime and diffusion length, may also influence the magnitude of the modulated reflectance signal. A semi-quantitative correlation is presented for multilayer epitaxially grown structures with germanium and boron-induced dislocations, as well as on their Czochralski silicon substrates, which contain a denuded zone.
Binary phase wave fronts reconstructed from internal reflection metal on glass holograms
Authors: Taghizadeh M. R. , Turunen J. , Vasara A.
Published: July 2002

We introduce a novel method for generating an arbitrary binary phase wave front with a metal on glass binary amplitude computer-generated hologram. Use is made of the phase delays that occur in total internal reflection and in reflection from a glass-metal interface. The experimental verification is presented by applying the method to reconstruction of a Dammann grating [H. Dammann and K. Görtler, Opt. Commun. 3, 312 (1971)] array generator.
Atomic layer epitaxy of planar-doped structures for nonalloyed contacts and field-effect transistor
Authors: Hashemi M. , Ramdani J. , McDermott B. T. , Reid K. , Bedair S. M.
Published: July 2002

Atomic layer epitaxy has been used for the low-temperature deposition of planar-doped structures using organometallic sources AsH3 and H2Se. Carrier concentration in the 1019/cm3 range was achieved, with a sharp concentration profile comparable to the best reported for equivalent structures by molecular beam epitaxy. A set of planar-doped Se sheets, separated by 50 Å of GaAs, was used for nonalloyed contacting layers to n-GaAs films with contact resistivity in the low 10−6 Ω cm2 range. Finally, a planar-doped field-effect transistor (FET) was fabricated with planar-doped sidewall source and drain contacting layers, giving a performance comparable to that of reported planar-doped structures by other techniques. This is considered to be the first demonstration of a planar-doped FET using organometallic sources.
Improvement in critical current density of Bi2Sr2Ca1Cu2Ox tapes synthesized by doctor-blade casting and melt growth
Authors: Kase J. , Irisawa N. , Morimoto T. , Togano K. , Kumakura H. , Dietderich D. R. , Maeda H.
Published: July 2002

Bi2Sr2Ca1Cu2Ox superconducting tape with an excellent Jc at 4.2 K has been synthesized by a modified doctor-blade process. A green tape prepared by doctor-blade casting is laid on a silver foil and heat treated at various temperatures below and above its partial melting temperature. The Jc of the tape increases dramatically when heat treated in a narrow temperature range just above the melting temperature. A highly oriented layer structure with c-axis alignment is obtained by the growth of aligned Bi2Sr2Ca1Cu2Ox grains in the partially melted state. This oriented microstructure produces an exceptional increase in Jc . Typical Jc ’s of the tape at 4.2 K are 50 000 A/cm2 at 0 T, 22 000 A/cm2 at 10 T, and 17 000 A/cm2 at 23 T. Note the small magnetic field dependence in Jc above 10 T.
Electrical and optical characterization of back-to-back Schottky (Al,Ga)As/NiAl/(Al,Ga)As molecular beam epitaxially grown double-heterostructure diodes
Authors: Cheeks T. L. , Sands T. , Nahory R. E. , Harbison J. , Tabatabaie N. , Gilchrist H. L. , Wilkens B. J. , Keramidas V. G.
Published: July 2002

Current-voltage, capacitance-voltage, and internal photoemission measurements of back-to-back Schottky diodes of buried metal (Al,Ga)As/NiAl/(Al,Ga)As double heterostructures grown by molecular beam epitaxy are reported. By using a selective etch process to access the buried layers and fabricate three-terminal devices, independent measurements of the barrier height on both sides of the buried metal double heterostructure were performed. Schottky diode behavior was observed for both upper and lower diodes and the barrier height was measured to be 1.1 eV for both diodes using internal photoemission. Electrical measurements showed a lower effective barrier height for the upper metal-semiconductor interface as compared to the lower interface in agreement with the different defect densities in these heterostructures.
Observation of large oscillator strengths for both 1→2 and 1→3 intersubband transitions of step quantum wells
Authors: Mii Y. J. , Wang K. L. , Karunasiri R. P. G. , Yuh P. F.
Published: July 2002

Both 1→2 and 1→3 intersubband transitions have been observed in a step quantum well structure consisting of 60 Å GaAs wells, 90 Å Al0.18Ga0.82As steps, and 280 Å Al0.44 Ga0.56As barriers. The transition energy and oscillator strength are 112 meV and 0.23 for the 1→2 transition and 150 meV and 0.15 for the 1→3 transition, respectively. The asymmetric property of a step quantum well allows the normally forbidden 1→3 transition to occur. The relaxation of the selection rule suggests a possibility of using optical pumping for infrared laser applications.
cw passive mode locking of a Ti:sapphire laser
Authors: Sarukura Nobuhiko , Ishida Yuzo , Nakano Hidetoshi , Yamamoto Yoshihisa
Published: July 2002

cw passive mode locking of a Ti:sapphire laser is achieved with 1,1′-dietyl-2,2′-dicarbocyanine iodide as the saturable absorber dye, using a 5 μm thin dye jet flow. The pulse width is 4.0 ps, which is almost the transform-limited pulse for the observed spectrum width. The output power is ∼50 mW, when it is pumped by a 5 W cw Ar laser, while the tuning range is 745–755 nm.
Research on resonant tunneling by fast neutron irradiation
Authors: Mao J. M. , Zhou J. M. , Zhang R. L. , Jin W. M. , Bao C. L. , Huang Y.
Published: July 2002

Resonant tunneling by fast neutron irradiation with doses from 1×1012 to 1×1016 n/cm2 was studied. We observed that peak and valley positions shifted to higher voltages, and peak-to-valley ratios decreased with higher doses in static current-voltage characteristics. Several models which take into account ionized impurities were used to give consistent explanation to such phenomena.
Demonstration of optical bistability with a nonlinear frustrated-total-reflection filter
Authors: Haelterman M. , Waelbroeck C.
Published: July 2002

The nonlinear frustrated-total-reflection filter is proposed as a remarkably simple all-optical computing element. Potential advantages of this device over nonlinear prism couplers and nonlinear thin films are presented. Optical bistability is experimentally demonstrated by using a liquid crystal as an optically nonlinear material.
Influence of background doping and implant damage on the diffusion of implanted silicon in GaAs
Authors: Murray J. J. , Deal M. D. , Stevenson D. A.
Published: July 2002

Diffusion of Si in GaAs is studied using implanted Si in undoped GaAs, implanted Si in Se-, Si-, and Zn-doped GaAs, and grown-in Si in epitaxial layer structures. No diffusion is observed in the undoped and Zn-doped GaAs cases, a moderate level is observed in the Si-doped case, and a significant amount is found for the Se-doped and nonimplanted Si-doped epitaxy cases. These results indicate that the diffusion is controlled by a Fermi level mechanism (probably via ionized gallium vacancies) and that implant damage inhibits diffusion by keeping the electron concentration and/or the ionized gallium vacancy concentration low.
X-ray moiré pattern in dislocation-free silicon-on-insulator wafers prepared by oxygen ion implantation
Authors: Jiang B. L. , Shimura F. , Rozgonyi G. A.
Published: July 2002

A moiré pattern formed by the two superimposed lattices of a host silicon substrate and the top ‘‘superficial’’ silicon layer formed in a separation by implanted oxygen (SIMOX) process has been observed with Lang transmission x-ray topography. The moiré patterns clearly show a characteristic fingerprint related to a nonuniformity in the ion implantation apparatus. It is shown that moiré patterns obtained with x-ray topography are a uniquely powerful tool for the characterization of highly ordered SIMOX wafers which have essentially no extended dislocations. Moiré patterns not only image the dilatational strain or lattice rotation between the two superimposed lattices, but also indicate the level of crystallographic perfection of the entire width and depth of the substrate/superficial layer system.
Characterization of pulsed laser deposited boron nitride thin films on InP
Authors: Paul T. K. , Bhattacharya P. , Bose D. N.
Published: July 2002

A new technique for deposition of thin-film boron nitride (BN) from BN wafers has been demonstrated using a Q-switched ruby laser. The deposition rate was found to be∼7 Å/pulse at an energy density of 2.5 J cm−2. X-ray photoelectron spectroscopy was used to confirm the film composition. Infrared absorption peaks were observed at 802, 1370, and 1614 cm−1 characteristic of B—N bonds. The films were found to have an indirect band gap of 4.1 eV with resistivity in excess of 1011 Ω cm and breakdown fields between 3.0×105—1.0×106 V cm−1. The dielectric constant of the films was in the range 3.19–3.28. The minimum interface state density on InP as obtained from C-V (1 MHz) analysis was typically 6.2×1010 cm−2 eV−1, which increased to 4.1×1011 cm−2 eV−1 after annealing at 200 °C in argon. Scanning electron microscopy studies showed that this resulted in the development of micropores in the film.
Avalanche enhancement of optical nonlinearities in semiconductor junctions
Authors: Horbatuck S. M. , Prelewitz D. F. , Brown T. G.
Published: July 2002

We examine the effects of avalanche processes on several classes of nonlinear optical interactions in semiconductor junctions. A silicon avalanche photodiode (APD) geometry is predicted to provide large enhancements of both the electronic nonlinearity (free-carrier plasma interaction) as well as the thermal nonlinearity. The thermal nonlinearity at a wavelength λ=1.06 μm in an APD is examined under normal operating conditions and a nonlinear interaction more than 5000 times that of the unbiased diode is observed.
Blue light generation by nonlinear mixing of Nd:YAG and GaAlAs laser emission in a KNbO3 resonant cavity
Authors: Goldberg L. , Chun M. K. , Duling I. N. , Carruthers T. F.
Published: July 2002

A monolithic KNbO3 resonant cavity was used to generate 455 nm radiation by sum frequency mixing of a 1064 nm Nd:YAG laser with resonantly enhanced 795 nm emission of a diffraction-limited externally injection-locked GaAlAs broad-stripe laser diode. Blue output of 154 mW was measured with 4.5 W of 1064 nm and 240 mW of 795 nm radiation in quasi-cw operation.
X-ray analysis of GaAs surface reconstructions in H2 and N2 atmospheres
Authors: Kisker D. W. , Fuoss P. H. , Tokuda K. L. , Renaud G. , Brennan S. , Kahn J. L.
Published: July 2002

In this work, we demonstrate the first in situ study of GaAs using grazing incidence x-ray scattering during processing at 100 Torr prior to epitaxial film growth. Our results indicate that the native oxide is removed and a well-ordered surface reconstruction is established at temperatures as low as 500 °C in hydrogen. In contrast, no surface reconstruction is observed when the substrate is heated in nitrogen at temperatures as high as 585 °C while comparable heating in hydrogen causes surface degradation in the form of liquid Ga droplets. These results suggest that a chemically induced surface transformation occurs rather than oxide evaporation during thermal treatment.
Single mode optical waveguides and phase shifters using InGaAlAs on InP grown by molecular beam epitaxy
Authors: Pamulapati Jagadeesh , Bhattacharya Pallab K.
Published: July 2002

We have investigated the characteristics of molecular beam epitaxial In0.53 (Gax Al1−x )0.47 As/InP waveguides and phase modulators in the 1.15–1.3 μm wavelength range. Loss at 1.15 μm has been measured and is ∼5 dB/cm. The measured phase shift due to the electro-optic effect results in an electro-optic coefficient r63 ∼0.6×10−12 m/V. Preliminary results at 1.3 μm show that the loss is reduced and is ∼3.4 dB/cm.
Doping superlattices based on InSb for mid-infrared detector applications
Authors: Phillips C. C.
Published: July 2002

The suitability of doping (‘‘nipi’’) superlattices based on InSb for 10 μm detector applications is studied and 77 K D* values of 8.1×1010 cm√Hz/W are found in optimized structures. The mode of nipi operation results in ‘‘self-passivating’’ devices which are compatible with III-V processing technology, and sensitivity uniformity figures superior to CdHgTe devices for large-area integrated detector arrays are predicted.
Intrinsic bistability in an optically pumped quantum well structure
Authors: Zrenner A. , Worlock J. M. , Florez L. T. , Harbison J. P. , Lyon S. A.
Published: July 2002

We describe a new semiconductor heterostructure, configured into a bistable device that can be switched either optically or electrically. The two states between which switching occurs involve very different levels of charge accumulation in a quantum well channel, affecting both the photoluminescence spectrum and the vertical photocurrent. The agents in the switching mechanism appear to be hot carriers.
Solid phase epitaxial growth of GaAs on Si (111)
Authors: Takano Y. , Kanaya Y. , Kawai T. , Torihata T. , Pak K. , Yonezu H.
Published: July 2002

A continuous GaAs film was successfully grown on Si(111) at the initial stage (20 Å growth thickness) by solid phase epitaxial growth. This growth suppressed the island formation observed with direct growth of GaAs on Si. The GaAs(111)A was obtained for the first time on Si(111) with an As prelayer deposited at 20 °C and 350 °C. The GaAs(111)B was also grown on Si(111) with an As prelayer deposited at 580 °C and 700 °C. The polarity of the (111) GaAs epitaxial film depends on the substrate temperature at which the As prelayer is deposited on Si.
Pump wavelength dependence of the gain factor in 1.48 μm pumped Er3+-doped fiber amplifiers
Authors: Kimura Yasuo , Suzuki Kazunori , Nakazawa Masataka
Published: July 2002

Gain characteristics of Er3+ -doped fibers for different pump wavelengths between 1.455 and 1.510 μm are investigated to obtain the optimum pump wavelength. It is found that the efficient pump wavelengths are located in the 1.460–1.475 μm range for Er3+ -doped Al2 O3 -GeO2 -SiO2 and Er3+ -doped GeO2 -SiO2 fibers, where a maximum gain of about 27 dB was obtained with an absorbed pump power of 31 mW.
Measurement of cw HF laser resonant degenerate four-wave mixing in an absorbing HF gas
Authors: Coffer J. G. , Chodzko R. A. , Bernard J. M. , Mirels H.
Published: July 2002

Continuous wave (cw) phase conjugation of a HF laser beam has been observed using resonant degenerate four-wave mixing in a HF gas absorption cell. A HF laser was operated in the P1(8) transition to provide total (forward plus backward) pump beam and probe beam intensities of about 400 and 30 W/cm2, respectively, in the cell. Conjugate reflectivities were measured as a function of HF pressure and frequency detuning from line center. Reflectivities of the order of 10−4 were measured at HF gas pressures of the order of 2 Torr when the laser frequency was tuned near line center.
Low-loss AlGaAs optical rectangular waveguides at 830 nm
Authors: Hibbs-Brenner M. K. , Sullivan C. T.
Published: July 2002

Optical channel waveguides with rectangular cross section and losses less than 0.1 dB/cm at 830 nm have been fabricated in AlGaAs heterostructures grown by organometallic vapor phase epitaxy. The modal attenuation correlates with surface morphology for all waveguide widths and with sidewall roughness for narrow channels. Surface morphology and modal attenuation improve when a superlattice buffer layer is incorporated into the structure. The loss is also reduced when the arsenic source (arsine) is purified in-line.
Light-activated two-level resistance switching: An extremely sensitive GaAs/AlGaAs solid-state photon counter
Authors: Snow E. S. , Campbell P. M. , Glembocki O. J. , Moore W. J. , Kirchoefer S. W.
Published: July 2002

Data are presented on a new type of extremely quiet and sensitive GaAs/AlGaAs photodetector. The photoresponse of the device is controlled by a hole trap in a tunnel barrier. Capture of a single photoinjected hole by the trap gates the device and produces an easily measured current pulse which can be counted by a conventional pulse-counting apparatus. There is only one detectable trap in a photoactive area of ≂400 μm2. However, due to electric field channeling effects the trap collects photoinjected holes with a 1% efficiency in the active region. The absence of measurable dark counts in a 25 h period at 77 K establishes a minimum detectable photon flux <0.001 photons/s at 8200 Å.
Proximity effect for scrolling spatial light modulator applications of surface-stabilized ferroelectric liquid-crystal switching
Authors: Brooks Robert E. , Clark Noel A. , Handschy Mark A. , Rieker Thomas P.
Published: July 2002

We demonstrate a ‘‘proximity effect’’ in a linear pixel array of bistable electro-optic surface-stabilized ferroelectric liquid-crystal (SSFLC) light valves, in which the switching threshold for a given pixel depends on the states of neighboring pixels. This effect should allow operation of SSFLC spatial light modulators as electro-optic shift registers.
Effect of substrates and film thickness on the structural, optical, and electrical properties of hydrogenated amorphous silicon films
Authors: Hishikawa Yoshihiro , Tsuge Sadaji , Nakamura Noboru , Tsuda Shinya , Nakano Shoichi , Kuwano Yukinori
Published: July 2002

Hydrogenated amorphous silicon (a-Si:H) films have been deposited on different substrates by a plasma chemical vapor deposition method. Raman spectra of the a-Si:H films are significantly dependent on the material of the substrate (glass, crystalline silicon, and stainless steel). The spectra are also dependent on the thickness of the films. The experimental results indicate that the silicon network structure of a-Si:H films is dependent on the material of the substrate. The dependence of the optical absorption coefficient and electric conductivities on the thickness is also reported.
B doping effect on reflection high-energy electron diffraction intensity oscillation during gas source silicon molecular beam epitaxial growth
Authors: Hirayama Hiroyuki , Koyama Kazuhisa , Hiroi Masayuki , Tatsumi Toru
Published: July 2002

B doping effect on reflection high-energy electron diffraction (RHEED) intensity oscillation was studied during gas source Si molecular beam epitaxial growth. During high doping of B above 1020 cm−3, no RHEED oscillation was observed on Si (100) surfaces. This is caused by surface B atoms which disturb surface migration of disilane (Si2H6) molecules. On the other hand, RHEED oscillation was observed on Si (111) √3×√3 B surfaces. At √3×√3 B surfaces, B exists in a subsurface substitutional site, directly underneath a Si adatom. This is the reason why surface migration was not disturbed by surface B atoms on Si (111) √3×√3 B surfaces.
Fabrication of ultrafine gratings on GaAs by electron beam lithography and two-step wet chemical etching
Authors: Katoh T. , Nagamune Y. , Li G. P. , Fukatsu S. , Shiraki Y. , Ito R.
Published: July 2002

50 nm period gratings were produced on thick GaAs substrates by using electron beam lithography and two-step wet chemical etching. The size was very close to the theoretical limit of the electron beam lithography. For transferring such a fine grating onto GaAs, a two-step wet chemical etching method was developed, where a H2SO4-H2O2-H2O system is first used to roughly etch the oxygen and carbon-contaminated GaAs surface, followed by surface planarization with a Br-CH3OH system.
Annealing behavior of GaAs implanted with Si+ and SiF+ and rapid thermally annealed with plasma-enhanced chemical vapor deposited silicon nitride cap
Authors: de Souza J. P. , Sadana D. K. , Baratte H. , Cardone F.
Published: July 2002

It is demonstrated using rapid thermal annealing that the electrical activation of Si+-implanted GaAs capped with a plasma-enhanced chemical vapor deposited (PECVD) silicon nitride (SixNy) layer requires longer annealing times compared to capless annealing. The SIMS profiles of 2H from the GaAs samples onto which SixNy caps were deposited using deuterated ammonia showed that deuterium atoms diffuse readily into the implanted region during PECVD. The improvement in the electrical activation of the capped samples with annealing time correlates directly with decreasing concentration of the 2H in the GaAs. It is postulated that the H atoms diffusing into GaAs during PECVD are trapped by the implantation-induced damage and the delay in electrical activation corresponds to the time required for the release of the trapped H.
Measurement of giant magnetic anisotropy in a uranium compound
Authors: Lander G. H. , Brooks M. S. S. , Lebech B. , Brown P. J. , Vogt O. , Mattenberger K.
Published: July 2002

We report the measurement of an anisotropy constant ‖K1‖∼1010 ergs/cm3 in the cubic uranium compound US at 0 K. This is over an order of magnitude greater than that in TbFe2, which has the largest known K1 of a cubic material. A novel method using the scattering of thermal neutrons has been used to determine K1. This measurement, together with our increased understanding of the interactions of 5f  electron materials, has some practical implications for magnetic devices.
Transient nonlinear optical properties of δ-doped asymmetric superlattices measured by picosecond electro-optic sampling
Authors: Ralph Stephen E. , Capasso Federico , Malik Roger J.
Published: July 2002

We have performed the first picosecond time-resolved measurements of the photorefractive and nonlinear absorptive properties of asymmetric GaAs doping superlattices. The lack of inversion symmetry in these structures results in a net photoinduced electric field and, therefore, photorefractive phenomena via the χ(2) of the material. Using the electro-optic sampling technique, the temporal behavior of the photorefractive, and nonlinear absorption effects are uniquely determined. We have observed peak refractive index changes of 3.8×10−4 at an energy density of 40 fJ/μm2.
High quality hydrogenated amorphous silicon films by windowless hydrogen discharge
Authors: Yoshida Akira , Inoue Katsushi , Ohashi Haruhiko , Saito Yoji
Published: July 2002

Hydrogenated amorphous silicon films were deposited by the direct photolysis of disilane using windowless hydrogen discharge. Electrical and optical properties of the films have been investigated. The photosensitivity (σph/σd) is about 107 in the films prepared at 250 °C, better than that of films obtained by conventional rf plasma chemical vapor deposition.
Reconfigurable optical interconnection using a two-dimensional vertical to surface transmission electrophotonic device array
Authors: Ogura Ichiro , Tashiro Yoshiharu , Kawai Shigeru , Yamada Keiji , Sugimoto Mitsunori , Kubota Keiichi , Kasahara Kenichi
Published: July 2002

A dynamic reconfiguration of optical interconnections for enhanced flexibility in photonic switching systems is realized using a two-dimensional vertical to surface transmission electrophotonic (VSTEP) device array. A matrix operational scheme for the VSTEP array is proposed and demonstrated. Through this operation, functions for light emission and for electrically programmable spatial light modulation are obtained in a single chip of the VSTEP array and a high-speed electronic addressing of 1 ns per one line for the matrix is also confirmed.
Photoluminescence study of sulfide layers on p-type InP
Authors: Leonelli R. , Sundararaman C. S. , Currie J. F.
Published: July 2002

The emission spectra from sulfurized p-InP annealed at temperatures below 300 °C are compared with those from untreated samples annealed under the same conditions. The unsulfurized samples show a VP related emission band at 1.14 eV whose intensity increases linearly with annealing temperature. The sulfurized samples exhibit an emission band at 0.94 eV attributed to a SP deep level. Both bands disappear when a layer of 20 Å is chemically removed. This shows that both VP and SP formation is limited to a few atomic surface layers.
Meander coupler, a novel wavelength division multiplexer/demultiplexer
Authors: Bornholdt C. , Kappe F. , Müller R. , Nolting H.-P. , Reier F. , Stenzel R. , Venghaus H. , Weinert C. M.
Published: July 2002

We have realized a novel wavelength division multiplexer/demultiplexer based on rib waveguides in GaInAsP/InP. The device is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant and has sinc2-type characteristics. Our devices have center wavelengths around 1.3 μm, filter half-widths 10–15 nm, and far end isolation down to −17 dB. The structure is suited for integration into optoelectronic integrated circuits for applications in bidirectional optical communication systems.