bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable transmission electrochromic windows utilizing tin-doped indium oxide counterelectrodes
Authors: Steele B. C. H. , Golden S. J.
Published: July 2002

The optical performance of Li-based variable transmission electrochromic windows incorporating tin-doped indium oxide thin-film counterelectrodes have been measured. The electrolyte used was 1M LiClO4 dissolved in dry propylene carbonate, the active device area was approximately 10 cm2 and the devices were driven galvanostatically with a current density of 100 or 200 μA/cm2. Significant and reversible transmission modulation could be achieved in these devices. The characteristics of the WO3 electrochromic electrode and the tin-doped indium oxide counterelectrode used were found to have a marked effect on the optical response of the device. The plasma wavelength of the tin-doped indium oxide counterelectrode was found to be a critical parameter.
Linewidth enhancement factor for GaInSbAs/GaSb lasers
Authors: Baranov A. N.
Published: July 2002

The linewidth enhancement factor α has been determined in GaInSbAs/GaSb lasers emitting near 1.8 μm (2 μm at RT) from the spontaneous emission spectra below threshold. For type-I lasers, where a p-n junction was located at the GaAlSbAs/GaSb heteroboundary, the measured α is 3.1 at the lasing wavelength at 82 K. In type-II lasers with the p-GaSb/GaInSbAs heterojunction α was estimated to be at least 2 times lower, that can be attributed to the formation of a quantum well structure at this heteroboundary under lasing conditions.
High-concentration Ce doping at n- and p-type Al/GaAs Schottky barrier interfaces
Authors: Foxman E. B. , Ikarashi N. , Hirose K.
Published: July 2002

Al/GaAs Schottky barriers are fabricated with 2.5–20-Å thick doping layers of Ce of concentrations 1020 cm−3 and 1021 cm−3 situated below the GaAs surface. Schottky barrier heights (SBHs) are determined from current- and capacitance-voltage measurements. n-type SBHs decrease with increasing Ce doping layer thickness, while p-type SBHs increase, but to a lesser degree. A cross-sectional image taken by high-resolution transmission electron microscopy shows that Ce is located in the substitutional sites of the doping layers. The changes in the SBHs are attributed to strain induced by Ce atoms in the substitutional sites. The difference in the magnitudes of change observed for n- and p-type SBHs is discussed in relation to the inhomogeneity observed in the density of Ce atoms at the interface regions.
Raman scattering of slab-mode phonons in InGaAsP/InP multiple quantum wells
Authors: Lazzouni M. , Nelson D. F. , Logan R. A. , Tanbun-Ek T.
Published: July 2002

Raman light scattering experiments in lattice-matched InGaAsP/InP multiple quantum wells are reported. Use of laser light below the InP band gap permitted study of right-angle scattering with the scattered light emerging parallel to the layers. Scattering by the binary InP longitudinal optic (LO) and transverse optic (TO) phonons dominated the spectra. The polarization selection rules for the TO and LO scattering were found to differ strongly compared to those operative in bulk InP. This is interpreted as arising from the interchange of the LO and TO phonon frequencies as expected in a dielectric continuum slab whose thickness is small compared to the wavelength of the incident radiation. In addition weak Raman scattering by a mixture of InGaAs and InP vibrations in the quaternary well material is reported.
Reduced lattice temperature high-speed operation of pseudomorphic InGaAs/GaAs field-effect transistors
Authors: Laskar J. , Maranowski S. , Caracci S. , Feng M. , Kolodzey J.
Published: July 2002

This letter presents a detailed study of the temperature dependence of submicron pseudomorphic InGaAs on GaAs substrate modulation doped field-effect transistors (MODFETs), doped-channel metal insulator field effect transistors (MISFETs), and metal semiconductor field-effect transistors (MESFETs). We determine similar variation in the measured extrinsic current gain cutoff frequency, FT, and similar dependencies of the effective electron velocity, veff, with reduced lattice temperature for the different field-effect transistors. The veff∼T−b where 0.15<b<0.20 over the temperature range of 300 to 110 K. These results provide direct experimental evidence that the saturated velocity of electrons is the most important parameter for high-speed operation and with proper design these different pseudomorphic InGaAs/GaAs field-effect transistors provide similar potential for high-speed operation.
Si and GaAs dry etching utilizing showered electron-beam assisted etching through Cl2 gas
Authors: Matsui S. , Watanabe H.
Published: July 2002

Electron-beam (EB) dry etching for Si and GaAs has been studied by utilizing showered electron-beam assisted etching in the presence of Cl2 gas. Anisotropic etching has been demonstrated for both Si and GaAs EB dry etching. Si and GaAs patterns with 0.6 and 0.3 μm linewidths have been obtained at a dose of 2×10−2 C/cm2 and 1×10−3 C/cm2. It was confirmed, through measuring photoluminescence, that damage induced by EB dry etching is nearly the same as that caused by gas etching and less than damage induced by reactive ion-beam etching and ion-beam etching.
Intrinsic acceptor antisite defects in GaAs under hydrostatic pressure
Authors: Kangarlu A. , Guarriello H. , Berney R. , Yu P. W.
Published: July 2002

Photoluminescence is used to study the behavior of CAs-related and GaAs cation antisite defect centers in GaAs under hydrostatic pressure at 10 K. The pressure coefficients, α, for these transitions were determined. We found α(CAs) to be about 12 meV/kbar which is very close to the band edge pressure dependence. The GaAs center demonstrated only slightly smaller coefficient. This makes the binding energy of CAs and GaAs, at 26 and 77 meV, respectively, almost independent of pressure. At pressures above 30 kbar relatively strong transitions were observed that displayed very small pressure dependence. The deepening of the ΓX-mixed donor levels interacting with these acceptor levels are primarily responsible for small pressure coefficients of the transitions above 30 kbar. A deepening of ∼160 meV is observed for the donors.
Growth and structural analysis of GdBa2Cu3O7 superconducting thin films on MgO single-crystal substrates
Authors: Yi H. R. , Li H. C. , Wang R. L. , Li J. W. , Wang C. A. , Li L. , Jia Y. B. , Zhao Z. X.
Published: July 2002

Thin films of GdBa2Cu3O7 superconductor were grown in situ on MgO single-crystal substrates under different substrate temperatures (Ts). When Ts=800 °C, the films were epitaxially grown with the c axis perpendicular to the film surface. The growth quality was very good, but the zero resistance critical temperature (Tc0) was only 85 K and the transition width (ΔTc) was 1.5 K. When Ts=670 °C, some of the films were epitaxially grown with the c axis perpendicular to the film surface. Some were mainly c axis oriented with a small amount of (110) and a-axis orientation. The growth quality was relatively poor, but they had Tc0 of 89–91 K and ΔTc of 0.6–1 K.
Effect of laser irradiation on carbon implanted copper substrates
Authors: Singh Rajiv K.
Published: July 2002

We have analyzed the nonequilibrium thermal effects of pulsed nanosecond lasers on carbon implanted copper substrates. The thermal effects of pulsed nanosecond lasers on carbon doped copper substrates were simulated by numerically solving the one-dimensional heat flow equation and taking into account the phase changes which occur at the surface, and temperature and time dependent thermal and optical properties of the irradiated solid. Intense pulsed laser irradiation induces rapid heating at the near-surface resulting in melting, followed by rapid quenching of the melt phase. The effect of laser variables (energy density, pulse duration) on the maximum melt depth, melt-in and solidification velocities and transient temperature profiles have been computed. The melting threshold was found to be approximately 1.40 J/cm2 for 15-ns laser pulses, and increased to approximately 2.5 J/cm2 for 50-ns laser pulses. Maximum melt depths and the surface temperatures were found to increase approximately in a linear manner with pulse energy density. Extremely high average solidification velocities (20–45 m/s) were calculated which may give rise to solute trapping and other nonequilibrium segregation effects.
Writing electronically active nanometer-scale structures with a scanning tunneling microscope
Authors: Hartmann E. , Behm R. J. , Krötz G. , Müller G. , Koch F.
Published: July 2002

A scanning tunneling microscope (STM) is used to locally modify p-n junctions on a scale of a few tens of nanometers. The p-n junction is composed of a phosphorus-doped, hydrogenated amorphous Si [a-Si:H(P)] layer deposited on heavily doped p-type crystalline Si(111). Under conditions of high current densities, with the p-n junction biased in forward direction, the a-Si:H layer is structurally changed leading to a decrease of the junction barrier height. The resulting exponential increase of hole injection into the modified amorphous layer leads to electronically active structures. They are detected by STM owing to their differing electronic properties.
Formation of a stable shell of YBa2Cu4O8 upon oxygen outdiffusion from superconducting YBa2Cu3O7−δ oxides
Authors: Shi L. T. , Tu K. N.
Published: July 2002

A stable shell of YBa2Cu4O8 (124) forms in powder and sintered bulk YBa2Cu3O7−δ (123) superconducting oxides upon oxygen outdiffusion from the latter and serves as a diffusion barrier to retard further oxygen outdiffusion. The 124 phase formation has been investigated by thermogravimetric analysis and x-ray diffraction. The better thermal stability of the 124 phase can be explained by the stronger bonding configuration of O(1) atoms in a double-chain structure.
Tunable narrow-band Nd3+ fiber laser
Authors: Sabert Hendrik
Published: July 2002

In a linear Nd3+ fiber laser, spatial hole burning is eliminated by frequency shifters at the ends of the cavity. They introduce a frequency difference of 160 MHz between the two counterpropagating waves. The laser operates spontaneously and stable on a single longitudinal mode with ≊12 kHz bandwidth near 1088 nm. Tuning over 16.5 nm is achieved by two piezoelectrically driven etalons.
Step dynamics on vicinal Si(001) during epitaxial growth
Authors: Myers-Beaghton Andrea K. , D. Vvedensky Dimitri
Published: July 2002

Adatom migration and attachment kinetics of vicinal Si(001) surfaces are described within a nonlinear continuum framework for epitaxial growth. The transient and steady-state terrace widths during growth are evaluated as a function of the growth conditions. Island formation is shown to be crucial in balancing the different capture rates of the two types of step edges to allow for a steady state of monatomic steps. We also find a greater tendency to form biatomic steps with increasing substrate temperature, decreasing beam flux, and increasing misorientation, in qualitative agreement with experimental measurements.
Nonlinear switching in coupled antiresonant reflecting optical waveguides
Authors: Trutschel U. , Mann M. , Lederer F. , Wächter C. , Boardman A. D.
Published: July 2002

We show that nonlinear mode coupling in a double-antiresonant reflecting optical waveguide structure leads to the power-dependent switching of an optical signal between remote channels.
Tunneling and subband levels in GaAs quantum well with direct and indirect AlxGa1−xAs barriers
Authors: Sankaran Vasu , Singh Jasprit
Published: July 2002

We present a study of coherent tunneling lifetimes for quasibound electrons confined in a GaAs quantum well by Al0.3Ga0.7As (direct band gap) and AlAs (indirect band gap) barriers, using the tight-binding representation for the electronic states in an eight-element (sp3) basis, and solving the time-dependent Schrödinger equation using a unitary approximation of the evolution operator. The dependence of the lifetime on barrier thickness is found to fit a WKB-type expression very well. Although simple effective mass theory is not applicable, the barrier thickness coefficient in the WKB exponent is determined by the Γ-point band extrema even for indirect AlAs barriers with X-point conduction-band minimum. The dependence of the subband energies and their in-plane dispersion on the mole fraction x of Al in the AlxGa1−xAs barrier is also presented, for x in the range 0.2–1.
Metalorganic molecular beam epitaxy of 1.3 μm quaternary layers and heterostructure lasers
Authors: Hamm R. A. , Ritter D. , Temkin H. , Panish M. B. , Vandenberg J. M. , Yadvish R. D.
Published: July 2002

Metalorganic molecular beam epitaxy of InGaAsP quaternary layers with the composition corresponding to the band gap at 1.3 μm has been investigated for growth temperatures ranging from 485 °C to 530 °C. From the x-ray diffraction and room temperature photoluminescence measurements Ga incorporation was found to be extremely growth temperature dependent. Photoluminescence linewidths increased rapidly for a negative lattice mismatch exceeding the critical value, whereas for positive mismatch no such broadening was observed. For lattice matched layers linewidths were broader for the higher growth temperatures. Threshold current densities ranging from 0.7 to 2.0 kA/cm2 were measured for conventional and multi-quantum-well broad area lasers with the active layers based on the 1.3 μm quaternary.
Femtosecond soliton collapse and coherent pulse train generation in erbium-doped fiber amplifiers
Authors: Gabitov I. R. , Romagnoli M. , Wabnitz S.
Published: July 2002

The study of the interplay of coherent and Raman effects on femtosecond soliton collapse and pulse train generation in erbium-doped fiber amplifiers is examined.
Thermionic emission of Γ and L electrons in the GaSb/InAs hot-electron transistors
Authors: Funato K. , Taira K. , Nakamura F. , Kawai H.
Published: July 2002

We have fabricated GaSb/InAs hot-electron transistors with base widths of 30 to 200 Å. The barrier height of thermionic emission was evaluated with two techniques; deducing from values of collector current density itself, and from its temperature dependence. The difference between the two results reveals that electrons are emitted from both Γ and L valleys of the GaSb conduction band. From the measured barrier height, the energy of the ground quantum level formed in InAs base was also deduced. Its dependence on the base width was compared with simple calculation where nonparabolicity of the InAs conduction band was considered. It indicates electron density in the InAs base is enhanced due to electron’s transfer from GaSb to InAs.
Identification of nonambipolar transport in the application of a photocarrier grating to hydrogenated amorphous silicon
Authors: Balberg I. , Weisz S. Z.
Published: July 2002

Thus far the many reports concerning the utilization of the photocarrier grating (PCG) method have assumed that ambipolar transport takes place in such a PCG when it is imposed on hydrogenated amorphous silicon (a-Si:H). This assumption, which is decisive in the interpretation of the experimental results in terms of the ambipolar diffusion length, has not been tested thus far. In this letter a corresponding testing criterion is proposed, and it is demonstrated that whenever ambipolarity is lost, the PCG-derived diffusion lengths may be wrong. The finding that ambipolarity is maintained in device quality a-Si:H is shown to confirm the theoretical suggestion that, whenever observed, the ambipolarity in a-Si:H is due to shallow trapping effects.
Resonance effects in Raman scattering by dopant-induced local vibrational modes in III-V semiconductors
Authors: Wagner J. , Koidl P. , Newman R. C.
Published: July 2002

Resonant Raman scattering work is reported on local vibrational modes (LVM) of Si and Be in highly doped III-V semiconductors, such as GaAs, InAs, and InSb. Raman scattering by the LVM of Si donors on group-III lattice sites is found to be strongly enhanced for incident photon energies matching the E1 band-gap energy of the host semiconductor indicating a rather narrow resonance in the scattering cross section. Raman scattering by LVM produced by acceptors, by contrast, is observed for a much wider range of photon energies, which corresponds to a much broader resonance. Possible explanations for this difference in resonance behavior are discussed including resonant donor energy levels derived from the L-point conduction-band minima. The present observations demonstrate, further, that attention must be paid to the appropriate choice of incident photon energies in order to achieve maximum sensitivity in a LVM Raman experiment.
Study of Γ, L, and X donor states in Si-doped AlGaAs by pressure dependent Hall measurements
Authors: Goutiers B. , Dmowski L. , Ranz E. , Portal J. C. , Chand N.
Published: July 2002

Using variable pressure for tuning the band structure and variable infrared light pulse intensity for tuning the number of Si-related shallow donor metastable states, we have demonstrated that these states are effective mass-like states linked to each of the conduction band Γ, L, and X minimum. The evolution of their binding energies with their increasing density is shown to decrease and the Mott transition for the Γ-like states has been also observed.
Optically pumped lasing of ZnSe at room temperature
Authors: Yang X. H. , Hays J. , Shan W. , Song J. J. , Cantwell E. , Aldridge J.
Published: July 2002

Optically pumped lasing of (111) oriented bulk ZnSe grown by seeded physical vapor phase transport (SPVT) technique has been achieved at room temperature under near resonant pumping with the excitation photon energy very close to the fundamental band gap. Laser emission can be seen at a pumping intensity as low as 7 kW/cm2. The lasing mode spacings resulting from the dispersion of the index of refraction for ZnSe in a Fabry–Perot resonator-like cavity have been observed as well. Our experimental results demonstrate that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.
High electron mobility in modulation-doped n-AlInAs/InP heterostructures grown by low pressure organometallic vapor phase epitaxy
Authors: Nakajima Shigeru , Murata Michio , Shiga Nobuo , Hayashi Hideki , Inoue Masataka
Published: July 2002

We report high electron mobility in modulation-doped n-AlInAs/InP heterostructures. The electron mobility in these heterostructures was observed to be 48 500 cm2/V s with electron concentration of 8.1×1011/cm2 at 50 K. Shubnikov–de Hass measurement clearly shows the existence of two dimensional electron gas in this heterostructure. We also observed small light sensitivity and no persistent photoconductivity in this heterostructure, both of which are due to an AlInAs layer which is free of DX centers in an AlInAs and high quality heterointerface grown by low pressure organometallic vapor phase epitaxy.
Measurement of nonlinear gain suppression and four-wave mixing in quantum well lasers
Authors: Chinn S. R.
Published: July 2002

We have applied a new heterodyne measurement of spontaneous emission modes of a cw, unmodulated quantum well laser operating above threshold, to observe spectrally asymmetric nonlinear gain suppression and intrinsic four-wave mixing up to 675 GHz from the lasing frequency.
Epitaxial growth of GaAs by solid-phase transport
Authors: Chen J. S. , Kolawa E. , Garland C. M. , Nicolet M-A.
Published: July 2002

(100) GaAs substrates with an Ag film about 45 nm thick were first annealed at 550 °C for 30 min in an Ar-flowing furnace (preannealing). A 110-nm-thick GaAs layer was then deposited on top of the preannealed 〈GaAs〉/Ag samples, followed by an amorphous Ta-Si-N film that was deposited over the GaAs layer to serve as a cap layer to minimize the loss of As during the following annealing process. The completed structures were then annealed again at 550 °C for 30 min in flowing Ar. The transport of Ga and As through the Ag layer and an epitaxial growth of GaAs on top of the (100) GaAs substrate are observed by cross-sectional transmission electron microscopy and MeV 4He backscattering spectrometry. No GaAs epitaxial growth is observed in samples that are not preannealed. Our results demonstrate that epigrowth through a solid transport medium is possible for a III-V semiconductor as it is for Si and Ge.
New method to suppress encroachment by plasma-deposited β-phase tungsten nitride thin films
Authors: Kim Yong Tae , Min Suk-Ki
Published: July 2002

Tungsten nitride thin films are prepared with the WF6-NH3-H2 system by the plasma-enhanced chemical vapor deposition method. X-ray diffraction and Auger spectroscopy show that the crystal structure and the composition of tungsten nitride thin films grown at the WF6/NH3 ratio of 1 are β-phase W2N. The resistivity of W2N is about 190–210 μΩ cm and it is demonstrated that severe encroachment and SiO2 etching during the low-pressure chemical vapor deposition of tungsten is remarkably suppressed by the predeposition of W2N.
Indium-Hg vacancy interactions in Hg1−xCdxTe measured by perturbed angular correlation
Authors: Hughes W. C. , Swanson M. L. , Austin J. C.
Published: July 2002

The interaction of mercury vacancies with dopant indium atoms in Hg0.79Cd0.21Te was studied using the perturbed γγ angular correlation (PAC) technique. Two dominant PAC signals, characterized by quadrupole interaction strengths νQ1=83 MHz and νQ2= 91 MHz and asymmetry parameters η1=η2=0.08, were observed and attributed to one or more In-VHg complexes. The complexes appeared after annealing doped samples at T≥350 °C in vacuum and quenching. The fraction of In atoms associated with vacancies was increased further by annealing at 80 °C for ≳10 h. The In-vacancy complexes vanished on annealing in a Hg-saturated atmosphere.
Optical measurement of ion implantation damage depth in multiple-quantum-well mesa structures
Authors: Lynch M. , Hegarty J. , Ginty A. , Kelly W. M. , Tsang W. T.
Published: July 2002

We have determined the depth of ion implant damage in semiconductor materials by nonlinear optical measurements. The carrier lifetime in ion-implanted mesas was measured by the pump-probe technique, and the carrier diffusion coefficient in unetched material was measured by degenerate four-wave mixing. An effective depth of damage within which the carriers experience fast recombination is then determined by modeling of the carrier dynamics in the mesa structure.
Complex multistable responses of serially connected optical bistable devices
Authors: Tokuda Yasunori , Abe Yuji , Kanamoto Kyozo , Tsukada Noriaki
Published: July 2002

We investigated the response characteristics of two bistable elements optically connected in series, i.e., vertically integrated self-electro-optic effect devices. The experimental results demonstrated that a variety of the multistable responses are obtained by controlling the electrical parameters. The composite characteristics of the two-tier system can be clearly predicted and interpreted in terms of the overlap of three bistable regions.
A novel quantum-well optoelectronic switching device with stimulated emission
Authors: Ou S. S.
Published: July 2002

A novel GaAs/GaAlAs quantum well optoelectronic switching device which exhibits an s-type negative differential resistance at room temperature and emits a high performance stimulated emission was demonstrated. The device structure is similar to the conventional separate confinement heterojunction quantum-well laser and thus can be easily integrated with the optoelectronic integrated circuits. The devices can be switched optically and/or electrically. Threshold current densities of 1.2 kA/cm2, differential quantum efficiencies as high as 67% (0.5 W/A slope efficiency per facet) and output power in excess of 50 mW per facet were obtained. To date, this is one of the best overall performances in terms of output power, differential quantum efficiency and threshold current density for the optoelectronic switching devices exhibiting stimulated emission capability.
Stress relaxation and stability of sputtered carbon thin films
Authors: Raman V. , Coffey K. R.
Published: July 2002

Stress measurements were performed on sputtered carbon films deposited on Si substrates in the temperature range from room temperature to 350 °C. Both hydrogenated and nonhydrogenated carbon films, ∼100 nm in thickness, were investigated. The stress relaxation kinetics were investigated for films tested in air and in the presence of an inert environment. The experimental data show distinct differences for tests performed in these two environments. Microscopic examination revealed that films tested in air show local loss of carbon following a thermal cycle whereas the films tested in argon show good stability and remain well adhered to the substrate
Electric-field-enhanced photoscission of the Si backbone in organopolysilane films
Authors: Shimakawa K. , Okada T. , Imagawa O.
Published: July 2002

A reversible photochemical process has been investigated in Si-backbone poly(methylphenylsilane) films. Prolonged irradiation by ultraviolet light induces a blue shift in the optical absorption and a decrease of photoconductivity in these films. The changes are enhanced by an electric field and are removed by annealing near the melting temperature. It is pointed out that the dissociation of photocreated excitons into free carriersand the subsequent nonradiative recombination cause the photoscission of the Si backbones.
Space-charge distribution and trapping kinetics in amorphous silicon solar cells
Authors: Könenkamp R. , Muramatsu S. , Matsubara S. , Shimada T.
Published: July 2002

Using electron time-of-flight experiments we have determined the electric field profile and the electron transport efficiency in amorphous silicon solar cells. In optimized devices we find a correlation between the space-charge distribution and the trapping behavior at the p-i junction, indicating that charged defects in the space-charge region determine both, the electric field distribution and the trapping kinetics. From their capture cross section the charged states are identified as positively charged dangling bonds.
Room-temperature continuous wave operation of a visible AlGaAs/InGaP transverse junction stripe laser grown by liquid phase epitaxy
Authors: Chang L. B. , Shia L. Z.
Published: July 2002

Continuous wave operation of an AlGaAs/InGaP/AlGaAs transverse junction stripe (TJS) laser diode (LD) has been achieved at room temperature for the first time. It was grown on a (100) GaAs semi-insulating (SI) substrate by liquid phase epitaxy (LPE). This device, with 100-μm-wide and 500-μm long Zn diffused stripe geometry, exhibits a room-temperature threshold current of 420 mA. The corresponding threshold current density is as low as 0.85 kA/cm2, which is the lowest value for those electroluminescent devices with an AlGaAs/InGaP/AlGaAs heterostructure. An emission peak wavelength of 615 nm and a light output power of 300 μW/facet were also reported.
Direct experimental evidence for diffusion of dopants via pairs with intrinsic point defects
Authors: Pichler P. , Schork R. , Klauser T. , Ryssel H.
Published: July 2002

Boron was implanted into silicon at a wafer temperature of 950 °C. The resulting boron profile showed a marked uphill diffusion at the surface and a very high diffusion enhancement. Initially homogeneously distributed antimony atoms showed remarkable redistribution effects after the implantation. These experiments allow the validation of diffusion theories, including the effects of point defect gradients on the migration of dopants. It will be shown that the experimental results agree well with the predictions of pair diffusion theories.
High-quality eutectic-metal-bonded AlGaAs-GaAs thin films on Si substrates
Authors: Venkatasubramanian R. , Timmons M. L. , Humphreys T. P. , Keyes B. M. , Ahrenkiel R. K.
Published: July 2002

Device quality GaAs-AlGaAs thin films have been obtained on Si substrates, using a novel approach called eutectic-metal-bonding (EMB). This involves the lattice-matched growth of GaAs-AlGaAs thin films on Ge substrates, followed by bonding onto a Si wafer. The Ge substrates are selectively removed by a CF4/O2 plasma etch, leaving high-quality GaAs-AlGaAs thin films on Si substrates. We have obtained a minority-carrier lifetime of 103 ns in a EMB GaAs-AlGaAs double heterostructure on Si, which is nearly forty times higher than the state-of-the-art lifetime for heteroepitaxial GaAs on Si, and represents the largest reported minority-carrier lifetime for a freestanding GaAs thin film. In addition, a negligible residual elastic strain in the EMB GaAs-AlGaAs films has been determined from Raman spectroscopy measurements.
Optically detected electron paramagnetic resonance of arsenic antisites in low-temperature GaAs layers
Authors: Sun H.-J. , Watkins G. D. , Rong F. C. , Fotiadis L. , Poindexter E. H.
Published: July 2002

Arsenic antisites in GaAs layers grown by molecular-beam epitaxy at low substrate temperatures (∼200 °C) were observed using electron paramagnetic resonance (EPR), magnetic circular dichroism in absorption (MCDA), and MCDA-detected EPR. This observation confirms that there is a MCDA band directly associated with arsenic antisites in the GaAs layers.
Spectral dependence of nonbolometric far-infrared detection with thin-film Bi2Sr2CaCu2O8
Authors: Schneider Gi. , Huggard P. G. , O’Brien T. , Lemoine P. , Blau W. , Prettl W.
Published: July 2002

The photoresponse of granular current biased thin-film Bi2Sr2CaCu2O8 superconductor to short pulse far infrared radiation has been measured for 16 laser lines, with frequencies between 10 and 1000 cm−1. A strong dependence of the signal on the frequency ω, approximately proportional to ω−2.3, is observed. It is shown, by calculations based on the resistively shunted junction model, that this photosignal can be understood to arise from the ac Josephson effect at grain boundary weak links.
Resonant self-aligned-stripe antiguided diode laser array
Authors: Mawst L. J. , Botez D. , Zmudzinski C. , Jansen M. , Tu C. , Roth T. J. , Yun J.
Published: July 2002

Resonant-optical-waveguide (ROW) arrays with a self-aligned-stripe (SAS) geometry have been realized for the first time. Resonance is achieved by holding the array element/interelement widths constant and varying the aluminum composition of the passive guide layer. External differential quantum efficiencies as high as 47% have been achieved from longitudinally uniform 20-element 1000 μm-long devices. Diffraction-limited-beam operation is obtained up to 13×threshold, and 2.1 W output power level from devices with Talbot-type spatial filters. The front-facet emitted coherent uniphase power is 1.6 W, with 1.15 W in the central lobe.
Observation of deep contact holes and conductive components underlying insulator in a memory cell by tunneling acoustic microscopy
Authors: Takata Keiji , Kure Tokuo , Okawa Takehiro
Published: July 2002

We have observed memory cells using tunneling acoustic microscopy (TAM). Ground-connected conductive components underlying an insulator are visible with electrostatic force imaging of TAM. Simultaneously, the contours of the memory cells with contact holes ∼2-μm-deep and ∼0.3 μm in diameter at the bottom are clearly imaged with a commonly used tip.
Spontaneous emission and optical gain in a Fabry–Perot microcavity
Authors: Deppe D. G. , Lei C.
Published: July 2002

The Fabry–Perot microcavity is analyzed in terms of its modification of the spontaneous emission and stimulated emission from a thin gain medium, which is contained between distributed Bragg reflectors. The structures correspond to the vertical-cavity surface-emitting semiconductor laser. Gain enhancement due to the cavity is calculated and compared to the case of a large Fabry–Perot cavity. The critical parameters in determining the degree of gain enhancement are the (large cavity) coherence length of the spontaneously emitted wave packet, and reflector design.
Femtosecond time division interferometry technique for measuring the tensor components of χ(3)
Authors: Chamon C. de C. , Sun C. K. , Haus H. A. , Fujimoto J. G.
Published: July 2002

We describe a new femtosecond time division interferometry technique for characterizing nonlinear index changes from different components of the χ(3) tensor. Pump probe interferometric measurements of nonlinear phase are performed using a time division multiplexed reference pulse. The n2∥ and n2⊥ components of the nonlinear index are measured by permuting the polarizations of the pulses and using a novel differential detection and modulation scheme. Measurements are demonstrated in an optical fiber.
Bloch-function analysis of resonant arrays of antiguided diode lasers
Authors: Botez D. , Holcomb T.
Published: July 2002

Bloch-function analysis of antiguided laser arrays provides closed-form expressions for key parameters in array design, and allows new insights in device behavior. For resonant and near-resonant devices it is found that as the gain is preferentially placed in the low-index regions (i.e., antiguide cores) the array mode favored to lase is the resonant leaky mode: in-phase or out-of-phase type. The intermodal discrimination is found to be strongly asymmetrical with respect to resonance: the resonant mode is preferred to lase over a much wider range in index step, Δn, variation on the high-Δn side of resonance than on the low-Δn side of resonance. Devices with Talbot-type spatial filters invariably operate in-phase except for Δn values well below resonance, when out-of-phase-like modes take over.
High contrast ratio self-electro-optic effect devices based on inverted InGaAs/GaAs asymmetric Fabry–Perot modulator
Authors: Chen Li , Hu Kezhong , Kapre R. M. , Madhukar A.
Published: July 2002

We demonstrate a new class of ‘‘normally off’’ high contrast ratio asymmetric Fabry–Perot (ASFP) reflection modulators based on a blue-shift of the Fabry–Perot mode under bias. The negative differential resistance (NDR) exhibited by the photocurrent-bias behavior was exploited to implement self-electro-optic devices (SEED) using as the load (a) a photodiode (D-SEED), and (b) a phototransistor (T-SEED). In the D-SEED scheme, a contrast ratio of ∼50:1 with ∼20% throughput was realized. The T-SEED configuration was found to offer nearly as high contrast ratio but with a ∼200:1 gain from the control light beam. Moreover, the ASFP modulators used belong to the inverted configuration which offers considerable convenience in device integration and optical interconnections.
Fully planar method for creating adjacent ‘‘self-isolating’’ silicon-on-insulator and epitaxial layers by epitaxial lateral overgrowth
Authors: Glenn J. L. , Neudeck G. W. , Subramanian C. K. , Denton J. P.
Published: July 2002

A novel and simple process is demonstrated for creating isolated silicon-on-insulator (SOI) tubs adjacent to selective epitaxial substrate layers. The process results in a fully planar wafer surface which is uniquely suited for mixed bipolar/complementary metal-oxide-semiconductor device fabrication. Low-temperature epitaxial lateral overgrowth (ELO) using SiH2Cl2/HCl/H2 is carried out in a reduced-pressure chemical vapor deposition reactor to create SOI islands in thermally grown SiO2 valleys. SOI islands and epitaxial seed regions are ‘‘self-isolated’’ by chemical-mechanical planarization. The as-grown ELO is single-crystal material with well-defined facets. Planarized SOI and epilayer regions have planar, featureless surfaces. Defect etching for the nonoptimized SOI layers indicates about 5×104 stacking faults/cm2.
Optical bistability in ceramic ferroelectrics due to thermal focusing
Authors: Chen T. , Scott J. F. , Sheih S.-J. , Bhalla A. S.
Published: July 2002

At modest laser powers (∼1 kW/cm2) ceramic Pb(Mg0.3Nb0.6Ti0.09)O3 exhibits optical bistability. The mechanism is shown to be thermal focusing. At power densities ∼1 kW/cm2 the oscillations between metastable states become nearly periodic (∼8 Hz), in analogy with the behavior exhibited in thermotropic liquid films [M. V. Vasnetsov, JETP Lett. 50, 480 (1990)]. At lower power levels (0.5 kW/cm2) aperiodic switching events are observed with one event per 45 mW (35 W/cm2) of increased laser power, with the Nth switching event occurring at time tN=AN(P−PN)−1, where P is the incident laser power and AN and PN are constants independent of P. The switching events depend also strongly on specimen temperature and its surrounding air pressure.
Broadly tunable LiB3O5 optical parametric oscillator
Authors: Robertson Gordon , Henderson Angus , Dunn Malcolm H.
Published: July 2002

We report, what is to our knowledge, the first XeCl excimer pumped optical parametric oscillator using critical phase matched LiB3O5 (LBO), to generate broadly tunable coherent radiation with high optical to optical efficiency. Tuning ranges of 355–497 nm in the ultraviolet/blue spectral region, and 809–2.34 μm in the near-infrared have been obtained, with pump depletions as high as 28%. Oscillation thresholds, external efficiencies, effects of intracavity losses, effects of pump beam size and inherent linewidths (∼0.3 nm) are also reported.
High current back lighted thyratron switch
Authors: Kirkman-Amemiya G. , Gundersen M. A.
Published: July 2002

High current operation of the back lighted thyratron, an optically triggered, low pressure diffuse discharge closing switch that operates with a self heated, super-emissive cathode, is reported. Repetitive operation at 5 Hz, 17.5 kV, 60 kA, with 500 ns pulse length has been achieved. The switch exhibits no high current limit up to 82 kA. High dI/dt≳1011 A/s and <45 ns rise times have been obtained. The high current and short rise time capabilities make this switch a possible replacement for spark gaps and multiple parallel thyratron switches in accelerator and laser applications.
Tip for scanning tunneling microscopy made of monocrystalline, semiconducting, chemical vapor deposited diamond
Authors: Visser Eric P. , Gerritsen Jan W. , van Enckevort Willem J. P. , van Kempen Herman
Published: July 2002

A tip for scanning tunneling microscopy (STM) was fabricated from semiconducting, chemical vapor deposited (CVD) diamond, epitaxially grown on a natural diamond substrate. Extremely high, p-type conductivity was realized by heavy boron doping. A sharp tip was obtained by conventional diamond polishing in such a way that the ultimate tip (radius<12 nm) is situated in the electrically conductive CVD layer. Atomic resolution on graphite surfaces could easily be obtained under normal operating conditions for STM in air. The feasibility of using the diamond tip to create nanostructures on surfaces was also investigated.
Doping of the layered compound SnS2 by phosphorus ion-implantation
Authors: Amir O. , Lifshitz E. , Richter V. , Uzan-Saguy C. , Kalish R.
Published: July 2002

Electrical activation of P implants in the layered semiconductor SnS2 is reported. Low-temperature annealing (300 °C) is shown to remove all implantation related lattice damage, but does not lead to any significant change in the electrical conductivity. Following higher annealing temperatures (up to 500 °C) the conductivity increases by over 5 orders of magnitude. Hall measurements show this conductivity to be n-type. The possibility that the observed electrical behavior is not due to phosphorus donor activity but is related to the implantation damage or to the annealing procedure is eliminated by Ar implantation control experiments which do not show any increased conductivity.
Low-temperature chemical vapor deposition of boron-nitride films using hydrogen azide
Authors: Ishihara Ryoichi , Sugiura Osamu , Matsumura Masakiyo
Published: July 2002

Stoichiometric boron-nitride films have been successfully deposited at temperatures as low as 400 °C by chemical vapor deposition using diborane (B2H6) and hydrogen azide (HN3). The film deposited on the silicon substrate at 475 °C was amorphous and contained hydrogen atoms with a density of 1.3×1022 cm−3. The breakdown field strength and the low-field resistivity were 2.8 MV/cm and 1015 Ω cm, respectively. The optical and low-frequency dielectric constants were 3.6 and 4.0, respectively. Metal-insulator-metal device equipped with this film showed steep current-voltage characteristics.
Transport properties of closely separated two-dimensional electron gases in a channel-doped back gated high electron mobility transistor
Authors: Kurobe A. , Frost J. E. F. , Ritchie D. A. , Jones G. A. C. , Pepper M.
Published: July 2002

We have investigated electron transport in two, closely separated, two-dimensional electron gases in a wide GaAs quantum well controlled both by front and back gates. The electron mobility in the back channel was considerably reduced by impurity doping. Magnetotransport measurements suggest the existence of a low mobility state associated with a high mobility front gas state. The results have a bearing on the proposed velocity modulation transistor, as the existence of two electron channels localized at their respective interfaces, without mutual interaction, can be difficult to achieve.
Low 1/f noise single-layer YBa2Cu3Ox dc SQUID at 77 K
Authors: Friedl G. , Vildić M. , Roas B. , Uhl D. , Bömmel F. , Römheld M. , Hillenbrand B. , Stritzker B. , Daalmans G.
Published: July 2002

Autonomous single-layer dc superconducting quantum interference devices (SQUIDs) have been prepared from epitaxial, laser-deposited YBa2Cu3Ox films on step edge SrTiO3 and LaAlO3 substrates. For device patterning, a SiOx inhibit technique as well as conventional ethylenediaminetetraacetic wet etch was used. The Josephson junctions are of grain boundary type. Their widths are 5 μm. The SQUID hole is a square of about 5 μm; the SQUID inductance is estimated to be about 20 pH. We obtained a very regular, nonhysteretic flux to voltage modulation over more than 100 flux quanta (Φ0). The maximum voltage signal is of the order of 15 μV peak to peak and the maximum transfer function dV/dΦ at the appropriate flux bias is 50 μV/Φ0 at 77 K. The best value of the equivalent flux noise as measured in the flux locked loop mode is 1.4×10−5 Φ0/Hz1/2 at 1 Hz and 1×10−5 Φ0/Hz1/2 in the white noise region for f≳5 Hz. This results in an energy resolution εn,w(f≳5 Hz)=1×10−29 J/Hz in the white noise region and 2×10−29 J/Hz at 1 Hz.
Plasma nitridation of Nb wiring sidewalls to improve annealing stability
Authors: Shiota Tetsuyoshi , Imamura Takeshi , Hasuo Shinya
Published: July 2002

The superconductivity of Nb wiring used in Josephson circuits deteriorates after annealing due to oxygen diffusion from the surface oxide. We previously reported that plasma nitridation of the Nb film surface improves the annealing stability of wiring. To further improve the annealing stability, we developed a new method that includes nitridation of Nb wiring sidewalls. We compared critical currents of the Nb wiring before and after annealing. The critical current with nitridation on both the sidewalls and the top surface did not decrease after annealing at 300 °C, while the critical current with nitridation on the top surface only dropped to less than 70% of its preannealing value. This indicates that the nitridation on the sidewalls is a very effective way to maintain the superconductivity of Nb wiring during annealing in the case of a small linewidth.
New 100 K TlSr2(Ca,Cr)Cu2O7 superconducting films
Authors: Tang Y. Q. , Sheng Z. Z. , Chen Z. Y. , Li Y. F. , Pederson D. O.
Published: July 2002

New TlSr2(Ca,Cr)Cu2O7 superconducting films on MgO(100) substrates have been prepared and characterized. The superconducting films were fabricated via a two-step process. Precursor SrCaCrCuO films were first deposited by spray pyrolysis at temperature of 350–400 °C, and thallium was then incorporated by heating the precursor films between unfired TlSrCaCrCuO bulk pellets at 880–900 °C in an oxygen atmosphere. The films were then cooled down to room temperature in an oxygen or argon atmosphere. The superconducting films were single 1212 phase with c-axis perpendicular to the surface of the MgO(100) substrates. Onset temperatures up to 110 K and zero-resistance temperatures up to 100 K were achieved. The critical transport currents (Jc) of the films were about 7×103 A/cm2 at 77 K.
First-order phase transition in a laser threshold
Authors: Deppe D. G. , Huffaker D. L. , Rogers T. J. , Lei C. , Huang Z. , Streetman B. G.
Published: July 2002

A mechanism for achieving a first-order phase transition in the threshold characteristics of a laser is discussed, and data demonstrating the effect are presented. It is suggested that a first-order phase transition can be realized through the design of a laser active region if the gain medium is localized to a spatial region with longitudinal dimensions much less than the wavelength of the resulting laser light. Evidence of the first-order phase transition is presented in the spontaneous emission characteristics of a microcavity semiconductor laser, which shows a decrease in the separation energy of the quasi-Fermi levels at threshold, along with hysteresis in the light versus current characteristics.
Co-lasing in an electrically tunable erbium-doped fiber laser
Authors: Dawson Jay W. , Park Namkyoo , Vahala Kerry J.
Published: July 2002

We demonstrate simultaneous wavelength operation (co-lasing) of an erbium-doped fiber ring laser with independent tunability of each wavelength over 35 nm between 1528 and 1563 nm. We study two different configurations and also investigate use of aluminum versus germanium codoped gain modules in the ring. We find that the aluminum codoped gain module has superior tunability.
Measurement of temporal coherence of light with copolarized and cross-polarized beams using cw laser-induced gratings
Authors: Rao K. Divakara , Gurjar Rajan S. , Bihari Bipin , Kumar G. Ravindra , Sharma K. K.
Published: July 2002

The temporal coherence of a cw laser has been measured using self-diffraction from a thin film of a rhodamine 6G-doped boric-acid glass. This and other similar glasses cover a wide spectral range over which such measurements can be made. The input power requirements for this technique to work in these glasses are rather nominal. These glasses can be used to obtain mutual coherence function of beams even when they are cross polarized. The results of an interferometric measurement are given for comparison.
Highly stable self-mode locking and the longitudinal mode structure in CuBr laser
Authors: Geng Jihong , Zhang Guiyan , Song Xiudong , Lin Fucheng
Published: July 2002

Highly stable and complete modulation self-mode locking pulses at 510.6 and 578.2 nm have been achieved simultaneously by suppressing the high-order transverse modes in a longitudinal discharge CuBr laser. The separated longitudinal modes of the laser line are reported for the first time. The different output features of the self-mode locking pulses have been discussed for various cavity lengths.
Effects of nonuniform current injection in GaInAsP/InP vertical- cavity lasers
Authors: Wada Hiroshi , Babić Dubravko I. , Ishikawa Masayuki , Bowers John E.
Published: July 2002

We systematically measured the active-area dependence of the threshold current density of GaInAsP/InP vertical-cavity lasers at various temperatures. The threshold current density was found to increase monotonically with increasing active area, with the effect becoming more pronounced at higher temperature. This phenomenon is due to nonuniform current injection into the active region.
Monolithic integration of normally-on and normally-off asymmetric Fabry–Perot modulators by selective antireflection coating
Authors: Goossen K. W. , Cunningham J. E. , Jan W. Y.
Published: July 2002

We present asymmetric Fabry–Perot quantum-well modulators which are overbalanced, so that at zero bias at the exciton wavelength reflectivity is high. As bias is applied and the quantum-well absorption decreases, the optical cavity balances, nulling reflection. By partially antireflection coating, at zero bias the optical cavity is balanced, so that the reflectivity is near zero, and increases with bias. Therefore, we can integrate normally-on and normally-off high-contrast modulators by selective AR coating. With 10 V bias, we obtain 11:1 contrast ratio for the normally-on devices and 8:1 for the normally-off devices.