bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron spin resonance of separation by implanted oxygen oxides: Evidence for structural change and a deep electron trap
Authors: Conley J. F. , Lenahan P. M. , Roitman P.
Published: July 2002

We present direct evidence for deep electron traps and structural changes in separation by implanted oxygen (SIMOX) buried oxides and evidence that some positively charged E′ centers are compensated by negatively charged centers in SIMOX oxides.
Low-frequency oscillations in semi-insulating InP
Authors: Backhouse C. , Samuilov V. A. , Young L.
Published: July 2002

Goronkin and Maracas (IEDM Conf. Proc., Dec. 1984, p. 182) reported a method of obtaining information on deep levels in GaAs by analyzing the temperature dependence of low-frequency current oscillations observed in semi-insulating material. In the present work, a modified version of their method was applied to Fe compensated InP. Power density spectra showed one main peak and several less well defined. An Arrhenius plot of log(T2/2f) versus 1/T gave an activation energy of 0.47 eV for the main peak, close to the value found by optical transient current spectroscopy (OTCS). The method is complementary to OTCS in that the same equipment is used and information is obtained more easily on levels which exhibit field-enhanced trapping.
Enhancement of flux pinning by H+ and Xe+ irradiation in epitaxial thin films of Ba2YCu3O7−δ
Authors: Siegal M. P. , van Dover R. B. , Phillips Julia M. , Gyorgy E. M. , White A. E. , Marshall J. H.
Published: July 2002

Epitaxial Ba2YCu3O7−δ (BYCO) films grown by the ex situ BaF2 process are comparable to single crystals both in crystalline quality and the value and temperature dependence of the critical current (Jc) in an applied magnetic field in the BYCO (001) direction of Ha=0.9 T. With the appropriate dose of either 2 MeV H+ or 135Xe+, we can enhance Jc by a factor of 2 in Ha=0.9 T with little effect on Tc. This is significantly greater than the ∼25% enhancement previously reported for epitaxial BYCO films grown by in situ techniques [Roas, Hensel, and Saemann-Ischenko, Appl. Phys. Lett. 54, 1051 (1989)]. This provides the opportunity to isolate the induced defects and study their properties.
Crystalline orientations of Tl2Ba2Ca2Cu3Ox grains on MgO, SrTiO3, and LaAlO3 substrates
Authors: Liou S. H. , Wu C. Y.
Published: July 2002

Crystalline orientations of Tl2Ba2Ca2Cu3Ox grains in magnetron sputtered films on MgO (001), SrTiO3 (001), and LaAlO3 (001) substrates were investigated by scanning electron microscopy. In contrast to the nearly single crystalline films on the lattice matched substrates SrTiO3 and LaAlO3, films on the MgO (001) substrate, being polycrystalline in nature, exhibit several preferred in-plane grain orientations. These orientations agree well with a simplified theory of near-coincidence site lattices between Tl2Ba2Ca2Cu3Ox and MgO.
Period-doubling bifurcation in a plasma reactor
Authors: Miller Paul A. , Greenberg K. E.
Published: July 2002

We describe the response of an industrial plasma reactor to excitation at varying power levels. When the reactor is excited at low power, rf voltage and current waveforms contain components at multiples of the drive frequency (13.56 MHz) due to the plasma’s nonlinear impedance. As power is increased, a transition point is reached and the waveforms change. Above the transition power level, signals at the half-harmonic frequency (6.78 MHz) and its multiples are also present, which is indicative of a period-doubling bifurcation. Above and below the bifurcation point, the dc bias and the etch rate behave quite differently.
Effects of nonuniform well width on compressively strained multiple quantum well lasers
Authors: Teng D. , Lo Y. H. , Lin C. H. , Eastman L. F.
Published: July 2002

We theoretically investigate the effects of nonuniform well widths on compressively strained In0.2Ga0.8As/GaAs multiple quantum well lasers using multiband effective mass theory and density matrix formalism. We find that the well width fluctuations do not degrade the transparency current, differential gain, and linewidth broadening factor. Besides, lasers with intentionally designed chirped well width have much broader gain profiles compared to uniform well lasers. This feature is attractive for applications requiring large gain bandwidth such as tunable lasers, mode-locked lasers, and wavelength division multiplexed laser arrays.
Amorphization of Cu0.6Ti0.2Zr0.2 by mechanical alloying
Authors: Zhang Hen , Naugle D. G.
Published: July 2002

An amorphous Cu0.6Ti0.2Zr0.2 alloy was synthesized by mechanical alloying of pure elemental powders of Cu, Ti, and Zr in air using a planetary high-energy ball-milling machine. The structure and thermal behavior of the powders milled for different times were analyzed by x-ray diffraction and differential scanning calorimetry. Results indicate that adding Zr into the Cu-Ti binary system can speed the amorphization. Furthermore, the alloy composition during the milling process may influence the ratio of Zr crystallization products relative to those of Ti.
Possible origin of degradation mechanisms in AlGaAs/GaAs laserlike structures
Authors: Sieber B. , Farvacque J. L. , Wang J. , Steeds J. W.
Published: July 2002

Aluminum fluctuations of AlGaAs epilayers deposited on GaAs are deduced from local scanning transmission electron microscope cathodoluminescence spectra. These fluctuations induce stress variations which are large enough to induce photoplastic glide of dislocations. Even if the lattice mismatch is very low for such epitaxial layers, such composition fluctuations can be seen as one possible origin of degradation mechanisms of optical devices. Furthermore, the order of magnitude of the stress fluctuation allows a rough estimate of the optical energy contribution to the activation energy for dislocation glide. This optical contribution (≂0.9 eV) is much more likely to correspond to electronic transitions at a dislocation reconstruction defect than to transitions related to dislocation intrinsic bands.
All-optical bistability in a type II GaAs/GaAlAs heterostructure
Authors: Teissier R. , Planel R. , Mollot F.
Published: July 2002

We have observed a bistability of low-temperature photoluminescence in a n-i-n type II GaAs/AlGaAs/AlAs quantum heterostructure. The integrated luminescence intensity ratio between the two states may reach 50. In as-grown samples, the bistability range lies between 40 and 250 W/cm2. These threshold values may be reduced on mesa-type samples, using an external load resistor. Spectral analysis and electrical measurements indicate that the two states correspond to hole accumulation in different layers of the structure. The transition occurs with the alignment of electronic Γ and X states due to optical pumping.
High-fluidity chemical vapor deposition of silicon dioxide
Authors: Shin H. , Miyazaki S. , Hirose M.
Published: July 2002

Silicon dioxide has been deposited by the glow discharge decomposition of SiH4 and O2 at substrate temperatures below −80 °C, where the thermal reaction on the surface was basically suppressed. Ion flux onto the growth surface was significantly reduced by employing a triode reactor. Oxide deposition onto surfaces with narrow features proceeds from the bottom of a trench or groove and results in planarization of the topography. Such high-fluidity chemical vapor deposition is inferred to occur through the formation of liquified precursors on the cooled surface.
Electronic stopping power of Si and Ge for MeV-energy Si and P ions
Authors: Keinonen J. , Arstila K. , Tikkanen P.
Published: July 2002

The electronic stopping powers of Si and Ge for 0–30 MeV 29Si and 29P ions are reported. The stopping power was studied by application of a technique of nuclear physics, the inverted analysis of Doppler-shift attenuation data. The measured values at 30 MeV are about 15% lower and at 2 MeV considerably higher than the predictions of the commonly used empirical electronic stopping powers by J. F. Ziegler, J. P. Biersack, and U. Littmark [The Stopping Power and Ranges of Ions in Matter (Pergamon, New York, 1985), Vol. 1]. The experimental nuclear stopping power was taken into account in the deduction of the electronic stopping power.
Effects of Y2O3 precipitates on critical current anisotropy in YBa2Cu3O7−x thin films prepared by plasma-enhanced metalorganic vapor deposition
Authors: Li Y. Q. , Zhao J. , Chern C. S. , Lu P. , Chien T. R. , Gallois B. , Norris P. , Kear B. , Cosandey F.
Published: July 2002

Yttrium-rich YBa2Cu3O7−x thin films containing yttria precipitates with an average size of less than 10 nm and with densities of up to 1024/m3 have been prepared by metalorganic chemical vapor deposition. The field dependence of the critical current density of the yttrium-rich films with the c-axis normal to the surface indicates that the precipitates act as effective pinning centers when the magnetic field is perpendicular to the CuO2 planes while their presence has no effect on the critical current density when the magnetic field is parallel to the CuO2 planes. In this case, intrinsic pinning of the weakly coupled CuO2 planes may be the dominant pinning mechanism in c-axis oriented YBa2Cu3O7−x thin films.
Formation and bleaching of strong ultraviolet absorption bands in germanium implanted synthetic fused silica
Authors: Albert J. , Hill K. O. , Malo B. , Johnson D. C. , Brebner J. L. , Trudeau Y. B. , Kajrys G.
Published: July 2002

Germanium ions have been implanted in fused silica using ion beams having energies of 3 and 5 MeV and doses ranging from 1×1012 to 5×1014 ions/cm2. For wavelengths shorter than 400 nm, the optical absorption increases strongly with two absorption bands appearing at 244 and 212 nm. The ion-induced optical absorption can be bleached almost completely by irradiation with 249 nm excimer laser light. Ion implantation also increases the refractive index of silica near the substrate surface. At 632.8 nm a refractive index increase of more than 10−2 has been measured. This decreases by 4×10−3 upon bleaching with 249 nm light.
On the temperature sensitivity of semiconductor lasers
Authors: O’Gorman J. , Levi A. F. J. , Schmitt-Rink S. , Tanbun-Ek T. , Coblentz D. L. , Logan R. A.
Published: July 2002

The temperature dependence of below-threshold emission from multiple quantum well semiconductor lasers is well characterized by a power law, in excellent agreement with Landau–Ginzburg theory of second-order phase transitions. We thereby show that it is the temperature dependence of net gain and not that of nonradiative recombination which primarily determines temperature sensitivity of threshold in long-wavelength injection lasers.
Transmission electron microscopy characterization of defects resulting from the polycrystalline silicon buffered local oxidation of silicon isolation process
Authors: Dixit G. A. , Hodges R. L. , Staman J. W. , Bryant F. R. , Sundaresan R. , Wei C. C. , Liou F. T.
Published: July 2002

Polybuffered LOCOS is used for isolation of active devices in submicron integrated circuits. Many papers have reported on the defects resulting from this process. We report, for the first time, on the structure and composition of these defects and relate the defects to a phenomenon similar to the traditional Kooi effect [E. Kooi, J. G. van Lierop, and J. A. Apples, J. Electrochem. Soc. 123, 1117 (1976)].
Efficient parametric generation of high-power coherent picosecond pulses in lithium borate tunable from 0.405 to 2.4 μm
Authors: Krause H.-J. , Daum W.
Published: July 2002

We have used lithium borate crystals, pumped by 18 ps laser pulses at 0.355 μm, as efficient optical parametric generator and amplifier of tunable, high-power picosecond pulses in the visible and near-infrared. This angle-tuned parametric device has a remarkably wide tuning range from 0.403 to 2.58 μm with a maximum pump-to-signal conversion of 28% around 0.425 μm. We investigate the influence of the pump intensity on the bandwidth of the tunable output. The duration of signal and idler pulses is 11–12 ps. No bulk or surface damage was observed for pump intensities up to 5 GW/cm2.
Epitaxial surface-emitting laser on a lattice-mismatched substrate
Authors: Gourley P. L. , Fritz I. J. , Brennan T. M. , Hammons B. E. , McDonald A. E. , Myers D. R.
Published: July 2002

We have demonstrated continuous-wave, room-temperature, photopumped operation of a vertical-cavity surface-emitting laser having a 0.8% lattice mismatch with its GaAs substrate. Such mismatch provides flexibility in designing resonators with new lasing wavelengths. The laser resonator comprises lattice-matched In0.12Ga0.88As and In0.10Al0.90As quarter-wave layers for mirrors and a strained-layer superlattice of In0.23Ga0.77As/Al0.35Ga0.65As for an active region. The structure lases in the range 1.05–1.10 μm under continuous-wave photoexcitation in the wavelength range 900–950 nm. The differential power efficiency is as high as 68% and the threshold is 2 kW/cm2 (1.8 kA/cm2 injection current-density equivalent). Dislocation line densities observed by photoluminescence microscopy are about 6×102/cm in both the active region and the uppermost mirror layers. The lines predominate along one 〈110〉 direction along which the laser light is preferentially polarized. These observations suggest a way of polarizing surface-emitting lasers by intentional patterning of grating lines on the wafer surface.
Adatom processes near step-edges and evolution of long range order in semiconductor alloys grown from vapor phase
Authors: Ogale S. B. , Madhukar A.
Published: July 2002

Single and multiple adatom energetics near the [110] and [1̄10] step edges on the As (2×4) reconstructed (missing dimer) GaAs (001) surface are examined to shed light on the issue of the occurrence of long range order in III-III-V alloys. Semiempirical potential functions and the simulated annealing procedure are employed. Step-induced local breaking of symmetry and the adatom-ledge interaction are found to favor the evolution of the 〈111〉 CuPt-B type of ordering.
Observation of stable room-temperature photoconductivity in hydrogenated amorphous silicon following long term light soaking
Authors: Xi J. , Macneil J. , Liu T. , Ghosh M.
Published: July 2002

Intrinsic hydrogenated amorphous silicon exhibiting unchanged room-temperature photoconductivity of 1.5×10−5 (Ω cm)−1 at 100 mW cm−2 after prolonged illumination and a photo-to-dark conductivity ratio over 106 is reported for the first time. Photoconductivity and CPM data in the as-deposited and light-soaked states, supported by dark conductivity and analytical measurements, suggest that the metastable midgap states in this material are significantly lower than levels previously reported.
Investigation of the electronic properties of in situ annealed low-temperature gallium arsenide grown by molecular beam epitaxy
Authors: Yin L.-W. , Ibbetson J. P. , Hashemi M. M. , Gossard A. C. , Mishra U. K. , Hwang Y. , Zhang T. , Kolbas R. M.
Published: July 2002

Current conduction through in situ annealed low-temperature gallium arsenide (LT GaAs) grown by molecular beam epitaxy (MBE) has been studied using Schottky diodes. The dominant transport mechanism in these films was found to be space-charge-limited current conduction in the presence of deep level states. We also examined two LT GaAs films, one with initially 4000 Å thick subsequently etched back to 2000 Å and the other sample with an initial thickness of 2400 Å, and found that the excess arsenic redistribution or clustering, carrier trap levels, and concentration depend strongly on the initial thickness of the LT GaAs film.
Chalcopyrite CuGaxIn1−xSe2 semiconducting thin films produced by radio frequency sputtering
Authors: Hernández-Rojas J. L. , Lucía M. L. , Mártil I. , Santamaría J. , González-Díaz G. , Sánchez-Quesada F.
Published: July 2002

CuGaxIn1−xSe2 thin films have been deposited by rf sputtering from three targets with different (Ga,In) content (x=0.25, x=0.5, and x=0.75). A structural, compositional, optical, and electrical study has been carried out for films grown at substrates temperatures higher than 350 °C. We have successfully obtained chalcopyrite single phase stoichiometric films. Very sharp absorption edges are obtained, with band gaps of 1.12, 1.35, and 1.51 eV for x=0, x=0.5, and x=0.75, respectively.
Wide-band Bragg reflectors made with silica on silicon waveguides
Authors: Adar R. , Henry C. H. , Kistler R. C. , Kazarinov R. F. , Weiner J. S.
Published: July 2002

We report the fabrication of strong Bragg reflectors embedded into fiber matched silica on silicon waveguides. First order gratings are dry etched into the waveguide core and are covered with a thin Si3N4 layer prior to cladding deposition. Reflection bands 225 Å wide for TE and 193 Å wide for TM polarizations are obtained with 200 Å Si3N4 cover layers. The TE and TM spectra are overlapping, resulting in nearly polarization independent Bragg reflectors.
Stimulated emission from p-Ge due to transitions between light-hole Landau levels and excited states of shallow impurities
Authors: Kremser C. , Heiss W. , Unterrainer K. , Gornik E. , Haller E. E. , Hansen W. L.
Published: July 2002

We investigate the far infrared emission spectra obtained from the so-called p-Ge light-heavy-hole laser. The occurrence of a frequency gap between the observed low-frequency and high-frequency range is for the first time explained by self-absorption due to impurity transitions. In the high-frequency range we find evidence of transitions between light-hole Landau levels and excited states of shallow impurities to be responsible for the lasing transitions.
Ultraviolet absorption measurements in single-mode optical glass fibers
Authors: Gallagher M. D. , Österberg U. L.
Published: July 2002

Accurate ultraviolet absorption measurements are reported in telecommunication single-mode optical fibers in the range from 280 to 600 nm (4.4–2.1 eV) using a cutback method. An absorption peak at 325 nm (3.8 eV) and an absorption edge near 290 nm (4.3 eV) are attributed to features seen in preform spectra. We suggest that fiber and preform absorption spectra are generally the same and do not find that there is any dependence in the absorption on the fiber dimensions. The effects of preparation for second harmonic generation on fiber absorption are also discussed.
Efficient keV x-ray generation from 50 mJ KrF laser plasmas
Authors: Broughton J. N. , Fedosejevs R.
Published: July 2002

High efficiency generation of keV x-rays from copper and iron targets has been studied using 50 mJ, 90 ps KrF laser pulses. By use of an aberration corrected 125 mm focal length lens conversion efficiencies of 9% and 10% into 800–1400 eV x-rays have been obtained for copper and iron targets. This is a substantial increase over the 2%–3% previously measured in a similar experiment and is comparable to results obtained with much larger laser energies.
Multistable floating body potentials: The cause of hysteresis in silicon-on-insulator metal-oxide-semiconductor transistors
Authors: Liu Patrick S. , Li G. P.
Published: July 2002

An experimental study of the hysteresis ID-VG characteristics in n-channel silicon-on-insulator metal-oxide-semiconductor transistors is reported. The result shows that the hysteresis is induced by multistable floating body potentials. An analytical model, which is based on the nonlinear feedback of carrier generation via multiplication and carrier discharge through parasitic bipolar action, also reveals that multistable floating body potentials are responsible for the hysteresis in ID-VG characteristics. To alleviate hysteresis effect, it is essential to reduce the parasitic bipolar current gain α and multiplication factor M. The reduction of α and M can be achieved by optimal source/drain design.
Direct observation of band-edge luminescence and alloy luminescence from ultrametastable silicon-germanium alloy layers
Authors: Spitzer J. , Thonke K. , Sauer R. , Kibbel H. , Herzog H.-J. , Kasper E.
Published: July 2002

Ultrametastable silicon-germanium (Si1−xGex) layers with a Ge content x in the range from about 20% to 27% were grown by Si-MBE at temperatures far below 550 °C (325–450 °C). The thicknesses of the layers (up to 500 nm) exceed the equilibrium thickness by a factor of up to 50. We observe in the as-grown samples without any annealing both the excitonic Si1−xGex band-edge luminescence and a broad alloy luminescence of unknown origin. The two peaks have an energy difference of ≊144 meV and shift linearly with the Ge content. The alloy band luminescence disappears when strain relaxation sets on upon annealing at around 600 °C.
Narrow-linewidth frequency stabilized AlxGa1−xAs/GaAs laser
Authors: Lee W. David , Campbell Joe C.
Published: July 2002

Velocity-selective magnetic optical activity in Rb vapor was used to simultaneously narrow the linewidth (500 kHz) and stabilize the frequency of an AlxGa1−xAs/GaAs laser. The frequency stability was determined by heterodyning two similar lasers and measuring their relative stability. The square root of the Allan variance, a standard figure of merit, was σy(τ)=4.9×10−12 for an averaging time of 200 s. This corresponds to a standard deviation of the beat frequency fluctuations of 1.9 kHz.
Optical time-of-flight measurement of carrier transport in GaAs/AlxGa1−xAs and In0.53Ga0.47As/In0.52Al0.48As multiquantum wells
Authors: Gupta S. , Davis L. , Bhattacharya P. K.
Published: July 2002

An all-optical time-of-flight technique is used for measuring perpendicular carrier transport in semiconductor heterostructures and multiquantum wells (MQWs). This technique is based on measuring a change in surface reflectance due to the absorption nonlinearities induced by the carriers, and has a temporal resolution of ∼1 ps. Typical results on a GaAs/AlxGa1−xAs MQW and an In0.53Ga0.47As/In0.52Al0.48As MQW are compared. The observed fast transport times can only be explained by a field-dependent carrier emission out of the quantum well, after which transport through the continuum states can occur. Due to larger barriers in the In0.53Ga0.47As/In0.52Al0.48As system, this intrinsic limit to transport is much larger, and hence these devices are observed to be slower than their GaAs/AlxGa1−xAs counterparts.
Passive stabilization of a synchronously pumped external-cavity surface-emitting InGaAs/InP multiple quantum-well laser by a coherent photon-seeding technique
Authors: Sun Diechi , Yamamoto Yoshihisa
Published: July 2002

A synchronously pumped external-cavity surface-emitting InGaAs/InP multiple quantum-well laser was passively stabilized by a coherent photon-seeding technique using an integrated output-coupling mirror. Both pulse duration and spectral width were reduced significantly and the time-bandwidth product was reduced by a factor of 30 to a near transform-limited value.
Evidence for a hole-controlled photocurrent in hydrogenated amorphous silicon
Authors: Cuniot M. , Lequeux N.
Published: July 2002

Significant differences in the experimental spectral responses and photocurrent-voltage characteristics measured on hydrogenated amorphous silicon films when reversing the polarity or the illuminated side of the film are reported. A model is advanced which accounts for variations of the photocurrent with both photon energy and applied voltage. It provides an accurate determination in steady state of the mobility-lifetime product for holes (μpτp=0.94±0.05×10−8 cm2/V) and predicts negative variations in the electron density upon illumination.
Reduced temperature dependence of threshold current by broadband enhanced feedback: A new approach and demonstration
Authors: Tsang W. T. , Choa F. S. , Logan R. A. , Tanbun-Ek T. , Sergent A. M. , Wecht K. W.
Published: July 2002

A new approach to reduce the rates of threshold current increase and external quantum efficiency decrease with increasing temperature in a semiconductor laser is proposed and demonstrated. This is based on the realization that the total laser cavity loss, which is normally relatively independent of wavelength, can be made to decrease with increasing wavelength. Since the gain peak of the laser shifts towards longer wavelength as temperature is increased, the rate of threshold current increase is thus reduced with increasing temperature. To implement this, we proposed and demonstrated the broadband enhanced feedback (BEF) approach using multilayer coatings, very weak or chirp gratings with peak reflectivity centered at the lasing wavelength corresponding to the maximum operating temperature desired. It was shown that the threshold-temperature coefficient T0 improved from the typical value of ∼45 K in long wavelength InGaAsP lasers (bulk active or MQW) to 85 K in BEF coated lasers. This scheme also simultaneously decreased the rate of quantum efficiency degradation with increasing temperature.
Selective growth of GaAs wire structures by electron beam induced metalorganic chemical vapor deposition
Authors: Takahashi T. , Arakawa Y. , Nishioka M. , Ikoma T.
Published: July 2002

We succeeded in the fabrication of GaAs wires by an electron beam induced selective growth technique, for the first time. In situ irradiation of the electron beam, with simultaneous supply of tri-methyl-gallium (TMG) and cracked AsH3, formed a GaAs quasiquantum wire structure as narrow as 300 nm selectively. Auger analysis and dependence of the growth on source materials and types of substrate suggest that the selective growth results from the decomposition of TMG by the electron beam irradiation.
Thermally activated dopant diffusion in crystalline silicon at 200 °C?
Authors: Pichler P. , Orlowski M.
Published: July 2002

Recently, anomalous, asymmetric diffusion of dopants in silicon during silicidation at temperatures as low as 200 °C has been reported. This observation has not been explained satisfactorily so far and therefore presents, a formidable challenge to present Fickian-type diffusion theories. In this letter, the structure of the asymmetric diffusion is analyzed and it is shown that the anomalous diffusion can be consistently explained by postulating the existence of an inhomogeneous stress field as an external driving force in conjunction with stress relaxation mechanisms due to the silicon self-interstitial diffusion. However, at the same time, it is demonstrated conclusively that the hypothesized diffusion in stress fields cannot be effectuated by thermal activation.
Creation and passivation of electron traps in n-InP treated with hydrogen plasma
Authors: Sugino Takashi , Ninomiya Hideaki , Yamada Takashi , Shirafuji Junji , Matsuda Koichiro
Published: July 2002

Studies on deep electron traps in n-InP treated with hydrogen plasma have been performed using isothermal capacitance transient spectroscopy measurements. Five electron trap levels, E1–E5, with activation energies of 0.21, 0.51, 0.32, 0.54, and 0.63 eV, respectively, below the conduction band are detected. Only E1 traps are observed in as-etched InP. Hydrogen-plasma treatment leads to enhancement of the density of E1 traps and creation of E2 and E5 traps. E1 and E5 traps are annealed out at 300 °C, while E2 traps are annealed out at a temperature as low as 150 °C. On the other hand, densities of E3 and E4 traps are significantly enhanced by annealing at 350 °C. This experimental result suggests that the E3 and E4 traps are generated during hydrogen-plasma exposure and are passivated by hydrogen atoms.
Simple soft x-ray spectrograph with a multilayer mirror for plasma diagnostics
Authors: Yamaguchi Naohiro , Katoh Jungo , Cho Teruji , Miyoshi Syoichi , Aoki Sadao , Nakajima Kunio
Published: July 2002

A simple soft x-ray spectrograph with a multilayer mirror has been constructed and applied for the diagnostics of a magnetically confined large plasma, which combines wavelength dispersion and x-ray imaging. Spectrophotographs of plasma radiation in the wavelength region from about 20 to 100 Å have been obtained with low-wavelength resolution. A comparison between the measured x-ray spectra and a calculation for bremsstrahlung x rays, in which the total reflection component as well as the Bragg reflection from the multilayer is taken into account, demonstrates that the spectrograph can be used to measure the electron temperature of plasmas.
Characterization of ZnSe/GaAs heterostructure using transverse acoustoelectric voltage spectroscopy
Authors: Han K. J. , Abbate A. , Bhat I. B. , Das P.
Published: July 2002

Transverse acoustoelectric voltage (TAV) spectroscopy has been employed to characterize the interface of high-resistivity ZnSe/GaAs heterostructure. Single- and double-beam TAV spectroscopy have been used to study the interface band and impurity transitions of the heterostructure at room temperature. From the TAV spectrum, a conduction band offset of 0.059 eV was found. The spectral behavior of the TAV waveform for single and double-beam cases was different due to the presence of a large number of surface states at the interface. Additional transitions in ZnSe film were also found in the double-beam case when a bias beam of 2.637 eV was used.
Integrated wavelength demultiplexer-receiver on InP
Authors: Bornholdt C. , Trommer D. , Unterbörsch G. , Bach H. G. , Kappe F. , Passenberg W. , Rehbein W. , Reier F. , Schramm C. , Stenzel R. , Umbach A. , Venghaus H. , Weinert C. M.
Published: July 2002

A detector stage comprising a photodiode, a field-effect transistor, and a load resistor, and a wavelength demultiplexer have been monolithically integrated in the GaInAsP/InP material system. Chips were mounted into complete modules and operated in a 1.3 μm/1.55 μm bidirectional transmission link. At 576 Mbit/s and 10−9 bit error rate the sensitivity of the module was −21 dBm, while the intrinsic sensitivity of the receiver was determined to be −28 dBm.
Detwinning and domain removing of KIO3 crystal
Authors: Yin X. , Lü M. K.
Published: July 2002

This letter reports the detwinning and domain removing of KIO3 crystal. As a result, single domain KIO3 crystal with a size of 30×15×15 mm3 has been obtained.
Growth of InAs and (InAs)1(GaAs)5 superlattice by atomic layer epitaxy using dimethylindium chloride
Authors: Mori Kazuo , Sugou Shigeo , Kato Yoshitake , Usui Akira
Published: July 2002

InAs is grown by metalorganic atomic layer epitaxy (MOALE) using dimethylindium chloride (DMInCl) as a new In source material for ALE in a horizontal, low-pressure metalorganic chemical vapor deposition (MOCVD) system. Monolayer-unit growth is obtained over a wide range of growth temperatures from 400 to 475 °C, and of substrate exposure times to DMInCl from 15 to 27 s. With metalorganic chloride source gases, both InAs and GaAs growth are self-limited over a temperature range of 50 °C, from 425 to 475 °C. This is the widest temperature range so far reported. This advantage is applied to ALE growth of (InAs)1(GaAs)5 superlattice.
Chlorine: A new efficient n-type dopant in CdTe layers grown by molecular beam epitaxy
Authors: Hommel D. , Waag A. , Scholl S. , Landwehr G.
Published: July 2002

We report for the first time on successful n-type doping of CdTe epilayers by the use of chlorine. The free-carrier concentration in the layers, grown by molecular beam epitaxy (MBE) and photoassisted MBE, can be varied easily over three orders of magnitude by changing the ZnCl2 oven temperature. Peak mobilities between 4700 cm2/V s (n=1.8×1016 cm−3) and 480 cm2/V s (n=1.6×1018 cm−3) are obtained. The resistivity of highly Cl-doped layers is as low as 8.5×10−3 Ω cm. Compared with In, which is commonly used for obtaining n-type CdTe epilayers, higher free-carrier concentrations and higher peak mobilities are obtained for compatible growth procedures by the use of Cl.
Optical detection of growth oscillations from high vacuum up to low-pressure metalorganic vapor phase epitaxy like conditions
Authors: Deppert K. , Jönsson J. , Samuelson L.
Published: July 2002

We report optical, real-time detection of growth oscillations for pressures up to low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) like conditions. The measurements were performed using the reflectance difference technique during epitaxial growth of GaAs in a vacuum chemical epitaxy (VCE) chamber in which the LP-MOVPE conditions were obtained by adding hydrogen. Growth oscillations could still be obtained over a wide range of V/III ratios at pressures in the mbar range. Under LP-MOVPE conditions we could observe oscillation amplitudes comparable to those found under VCE conditions. Furthermore, the occurrence of oscillations when hydrogen is introduced shows that the layer-by-layer growth is not affected by the presence of hydrogen. These results seem to open the way for the in situ detection of growth oscillations even in conventional MOVPE systems.
Study on channel deformation in the GaAlAs/GaAs V-channeled substrate inner stripe lasers: Contamination and growth profile
Authors: Lee Song Jae , Song Jae-Kyung , Park Joo-Sung , Kim Nam-Heon , Song Woon-Young , Koh Seok-Ki , Kim Joon-Young , Shin Dong-Soo , Lee Jae-Ho , Bang Dong-Soo , Lee See-Hyung , Kim Ki-Hwan , Huh Young W.
Published: July 2002

A study on channel deformation in the GaAlAs/GaAs V-channeled substrate inner stripe (VSIS) laser is presented. The deformation of the chemically etched V-channel is achieved by two independent mechanisms, i.e., the mass transport and melt etch increasing the effective channel width, one of the most important parameters to control device characteristics. However, contrary to widely accepted conception, the melt etch plays a relatively minor role in channel deformation, compared to the mass transport. We have also found that both the mass transport and melt etch depend strongly on hardening of sample surface, which in turn depends on the system condition.
Interferometric ring diode lasers
Authors: Hohimer J. P. , Vawter G. A. , Craft D. C. , Hadley G. R.
Published: July 2002

We report the first demonstration of interferometric ring diode lasers. These devices show a sharply peaked light versus current curve with cw output powers up to 8 mW. The output emission is single-frequency with side-mode-rejection ratios up to 30 dB.
Measurements of film carrier lifetimes in silicon-on-insulator wafers by a contactless dual-beam optical modulation technique
Authors: Yang Ping-Chang , Li Sheng S.
Published: July 2002

A contactless dual-beam optical modulation (DBOM) technique has been applied to measure the film carrier lifetimes in the SIMOX (separation by implantation of oxygen) wafers with different oxygen implant doses, annealing temperatures, and film thicknesses. Film carrier lifetimes ranging from 0.23 to 0.72 μs were observed in these wafers. The DBOM method is based on the modulation of the transmission intensity of an infrared (IR) probe beam by a visible pump beam (hν≥Eg) via free-carrier absorption in the SIMOX wafer. A theoretical model is developed to deduce the excess carrier lifetimes in the SIMOX film by the DBOM technique. Mappings of the film carrier lifetimes in these SIMOX wafers were also carried out.
Silicon heterojunction bipolar power transistor with an amorphous Si:B alloy emitter
Authors: Li X.-H. , Carlsson J. R. A. , Johansson M. , Ekström B. , Gong S. F. , Hentzell H. T. G.
Published: July 2002

A pnp Si heterojunction bipolar power transistor has been fabricated using an amorphous Si0.7B0.3 alloy as a wide band-gap emitter. The amorphous alloy is formed by co-deposition of B and Si: it has a low resistivity of 2.5×10−3 Ω cm at room temperature after annealing at 1000 °C for 30 min and a band gap of 1.70 eV when annealed at 1100 °C for 20 min. In order to make a direct comparison, a conventional transistor with a diffused emitter and a polycrystalline silicon (poly-Si) emitter transistor have also been fabricated. It is shown that an amorphous Si0.7B0.3 alloy emitter transistor can have an electrical current gain 2–5 times higher than a poly-Si emitter transistor and 20 times higher than a conventional transistor.
Time reversal and reciprocity in sound propagation through elastic and porous layers
Authors: Allard Jean F. , Brouard Bruno , Lafarge Denis , Lauriks Walter
Published: July 2002

Transmission of plane sound waves through elastic or porous layers involves longitudinal and transverse waves and can be described by equivalent multiport circuits. Different ports on each face of the layer are related to the normal and the tangential strains and velocities. The form of the impedance matrix of the circuits indicates that the coupling between normal and tangential conjugate variables is antireciprocal. This is due to the fact that the angle of incidence changes sign under time reversal.
Lateral straggling of B and P ions implanted in channeling and random directions of Si single crystals
Authors: Raineri Vito , Privitera Vittorio , Rimini Emanuele
Published: July 2002

Boron and phosphorus ions at energies of 400 keV and 1 MeV were implanted along the [100] axis or in a random direction of silicon wafers covered by a sequence of 10 μm wide and 3 μm thick SiO2 stripes. Two-dimensional isoconcentration contour lines at the substrate doping level were determined by a new technique based on spreading resistance profiling. The lateral distribution under the mask of ions implanted in a random direction is always broader than that of ions implanted along the [100] axis. With increasing the dose of the channeled implants the lateral penetration also increases due to the scattering of channeled ions by the silicon atoms displaced from lattice sites
Improved InP regrowth properties in metalorganic vapor phase epitaxy by addition of CCl4
Authors: Nordell N. , Borglind J.
Published: July 2002

Selective and planar regrowth of InP around stripe mesas up to 5.5 μm height formed with reactive ion etching in InP substrates has been made with metalorganic vapor phase epitaxy by adding CCl4 to the process gases. CCl4 seems to prevent nucleation on the phosphorous-rich {111}B lattice planes and on the silicon-nitride cap at the top of the mesa and hence permits reproducible regrowth with desired morphologies for integration of optoelectronic circuits at mesas oriented along the [110] direction. The addition of CCl4 does not influence dopant capability or the semi-insulating properties of Fe-doped material, for which a resistivity of 1×109 Ω cm has been obtained.
Observation of interface traps in the silicon conduction band at the (100)Si/SiO2 interface at 4.2 K
Authors: Anderson W. R. , Wheeler R. G. , Ma T. P.
Published: July 2002

Measurement of the gate capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor field-effect transistors at 4.2 K has been used to search for Si/SiO2 interface traps above the silicon conduction band edge. A distinct feature emerges in the gate conductance curves after x-ray irradiation providing strong evidence for the formation of conduction-band interface traps. Trap densities and time constants have been extracted using a distributed circuit model. The trap energy level lies about 20 meV above the bottom of the conduction band.
Continuous coherent microwave oscillation in InSb p-n junctions
Authors: Kamakura Katsutoshi
Published: July 2002

Continuous coherent microwave oscillation is observed in InSb p-n junctions under the application of a dc reverse bias voltage in the region of avalanche breakdown and an external high magnetic field at 77 K. The observed oscillation frequency varies with the sample current of the p-n junction and the magnetic field. The oscillation mechanism seems to be different from that of impact-avalanche transit-time (IMPATT) diodes because the external high magnetic field is required to cause the microwave oscillation in the InSb p-n junctions.
Multifilament NbTi with artificial pinning centers: The effect of alloy and pin material on the superconducting properties
Authors: Motowidlo Leszek R. , Zeitlin Bruce A. , Walker Michael S. , Haldar Pradeep
Published: July 2002

Low-temperature superconductors containing artificial pinning centers (APC) have produced record critical current densities in NbTi at magnetic fields below 4 T and promise further improvements at these and higher fields. Peak current densities are achieved when pinning center spacings are matched to spacings of the flux line lattice at the field of operation. The enhancement of Jc through inclusion of artificial pinning materials is accompanied by reduction in Tc and Hc2 through proximity effects. We find that the choice of the superconducting alloy as well as the pin material has marked effect on both the characteristic pinning force Fp and the critical magnetic field Hc2.
Charge injection frequency multiplier
Authors: Mensz Piotr M. , Sivco Deborah L. , Cho Alfred Y.
Published: July 2002

We propose a novel frequency doubler, implemented in three terminal semiconductor heterostructures. This device represents a natural embodiment of the symmetry of hot-electron injection with respect to the polarity of the heating voltage. An efficient frequency doubling, comprising conversion gain with low harmonic distortion of the output signal was demonstrated using InGaAs/InAlGaAs/InGaAs charge injection transistor devices. A natural extension of this idea is the implementation of a higher order frequency multiplier and a frequency mixer.
Observation of Ga antisite defect in electron-irradiated semi-insulating GaAs by photoluminescence
Authors: Kuriyama K. , Yokoyama K. , Tomizawa K. , Takeuchi T. , Takahashi Hirokazu
Published: July 2002

Cation antisite defects produced in semi-insulating GaAs by 30-MeV electron irradiation were studied using a photoluminescence (PL) method. PL emissions associated with a double acceptor GaAs, lying at 78 and 200 meV above the valence band, were observed at 860 and 935 nm in 600 °C annealed samples. The former emission is a prominent spectrum with its phonon replica at 880 nm, whereas the latter is buried in broad emissions consisting of the defect complexes such as the VAs-CAs complex. The electron irradiation-induced GaAs defects are ∼102 times smaller than those produced in neutron irradiated semi-insulating GaAs.
Low 1/f noise in YBa2Cu3O7 dc SQUIDs on (Y)ZrO2 bicrystal substrates
Authors: Olsson H. K. , Nilsson P.-Å. , Ivanov Z. , Koch R. H. , Stepantsov E. A. , Tzalenchuk A. Ya.
Published: July 2002

We report low noise operation of YBa2Cu3O7 SQUIDs superconducting quantum interference devices using Josephson junctions grown on bicrystal substrates of (Y)ZrO2. Energy sensitivities measured at 10 Hz (Sε=4.5×10−29 J/Hz) were to our knowledge lower than previously reported for a YBa2Cu3O7 SQUID with practical loop size (∼40 μm). The 1/f part of the voltage noise reached a maximum at 85 K where the noise spectrum was essentially white. The 1/f noise increased both at lower temperatures due to increased critical current fluctuations (∼Ibias2.2) and at higher temperatures, where the flux noise from the film produces a peak below Tc(=89 K).
X-ray photoemission diffraction as a novel technique for antiphase domain detection in the epitaxial growth of polar compounds on nonpolar substrates
Authors: Olivier J. , Bartenlian B. , Charasse M. N. , Bisaro R. , Wyczisk F. , Chazelas J. , Hirtz J. P.
Published: July 2002

We show that x-ray photoemission diffraction can be used as a means of detection of antiphase domains in the epitaxial growth of polar compounds on nonpolar substrates. An example is given in the case of the GaAs growth on a patterned (001) Si substrate, 4° off towards [110], where antiphase domains have been observed by scanning transmission electron microscopy.
Effect of crystallographic alignment of isolation trenches: A resolved-shear-stress perspective
Authors: Hu S. M. , Chidambarrao D.
Published: July 2002

We have analyzed and compared the resolved shear stresses of all 12 glide systems for the 60° dislocation for 〈110〉-aligned and 〈100〉-aligned isolation trenches. From among the 12 glide systems, we select for each trench alignment the one which exhibits the highest stress level. The results for the two alignments are then compared. We find that the largest resolved shear stress for a 〈110〉-oriented trench is about 30% more than that for a 〈100〉-oriented trench from both the isotropic and the anisotropic analyses. Other factors that may cause a reduction of dislocation density for the 〈100〉-trench alignment are also discussed.
a/c YBa2Cu3O7 boundaries: Preferential sites for the nucleation of epitaxial Y2O3 precipitates
Authors: Catana A. , Schlom D. G. , Mannhart J. , Bednorz J. G.
Published: July 2002

Y2O3 precipitates with typical sizes between 70 and 300 nm2 have been identified by high-resolution electron microscopy and image calculations in mixed a- and c-axis oriented YBa2Cu3O7 sputtered films. The precipitates are densely distributed (1015 cm−3), have tabular shape and grow epitaxially at boundaries between a- and c-axis oriented grains, with the (001) Y2O3 plane parallel to the a, b plane of the a-axis oriented grain and the (110) Y2O3 plane parallel to the a,b plane of the c-axis oriented grain. Their largest interfacial facet lies parallel to the a,b plane of the a-axis oriented regions. Lattice-matching arguments show that energetically this situation is the most favorable one, which explains the nucleation of precipitates at a/c boundaries.
Synchrotron topographic characterization of Fe-doped flux-grown potassium niobate tantalate
Authors: Hu Z. W. , Jiang S. S. , Wang J. Y. , Zhao J. Y. , Jiang J. H. , Feng D.
Published: July 2002

The Fe-doped flux-grown KTa1−xNbxO3 (KTN) with composition on the margin of the cubic phase zone has been characterized by synchrotron topography. It is shown that growth bands in flux-grown KTN are primary planar defects which lie along the [010] growth direction. A set of [100] oriented black-white fringes revealed by anomalous scattering are ascertained to be 180° ferroelectric domains, which are caused by occurrence of the partial transition in the interior of KTN. The origins of occurrence of this partial ferroelectric transition and the growth characteristics in KTN are outlined
Selective area growth of heterostructure bipolar transistors by metalorganic molecular beam epitaxy
Authors: Hamm R. A. , Feygenson A. , Ritter D. , Wang Y. L. , Temkin H. , Yadvish R. D. , Panish M. B.
Published: July 2002

Heterostructure bipolar transistors (HBT) have been grown by selective area epitaxy (SAE) using metalorganic molecular beam epitaxy (MOMBE). dc characteristics, comparable to those for devices grown on unprocessed substrates, were obtained after removal of the edge growth. Data is also presented for devices in which the emitter mesas were regrown by SAE into openings which had been previously defined by photolithography on a structure containing only the collector and base layers. In both cases we use an in situ cleaning process consisting of an Ar ion beam sputtering and Cl2 etching. This step results in significantly improved junction quality.
Fe ions in proton-exchanged LiNbO3 waveguides
Authors: Olivares J. , Diéguez E. , López F. J. , Cabrera J. M.
Published: July 2002

The valence state of Fe in proton-exchanged LiNbO3 optical waveguides is studied by electron paramagnetic resonance (EPR) and loss measurements. Starting from a fully reduced substrate showing no Fe3+ EPR signal, the exchange process induces a strong Fe2+→Fe3+ conversion within the guiding region. A new EPR line is also observed to peak at 1650 G for B perpendicular to C-axis which is attributed to a new Fe3+ center. Losses (at 442 nm) are about forty times lower in the guide than in the reduced substrate.
Generation and measurement of picosecond voltage pulses in YBa2Cu3O7 thin films
Authors: Shi L. , Huang G. L. , Lehane C. , Zheng J. P. , Kwok H. S.
Published: July 2002

An autocorrelation method was proposed and applied to measure the temporal decay of ultrafast voltage pulses in the superconducting state. Using a 40 ps laser, voltage pulses with fast components <40 ps were obtained in a YBCO thin film which was biased within the superconducting state.