bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep levels in GaAs grown on Si during rapid thermal annealing
Authors: Cho Hoon Young , Kim Eun Kyu , Kim Yong , Min Suk-Ki , Yoon Ju Hoon , Choh Sung Ho
Published: July 2002

Deep levels in GaAs on Si substrates grown by metalorganic chemical vapor deposition (MOCVD) were studied during infrared rapid thermal annealing. For GaAs layers on Si after annealing at 850 °C for 20 s, three electron deep levels at 0.36, 0.27, and 0.20 eV below the conduction band were created as the dominant deep levels. Especially, the 0.36 eV level was found to increase up to 40% of the donor concentration as the thickness of Si substrates increased. These results indicate that rapid thermal annealing of GaAs on Si may induce high-density deep levels due to a biaxial tensile stress caused by the difference in thermal expansion coefficients.
Yb-doped InP grown by metalorganic vapor phase epitaxy using a beta-diketonate precursor
Authors: Williams D. M. , Wessels B. W.
Published: July 2002

Yb-doped InP has been prepared by metalorganic vapor phase epitaxy using a Yb fluorinated beta-diketonate. The doped layers were n type with carrier concentrations ranging from 0.6 to 17×1015 cm−3. The doped layers exhibited the characteristic Yb+3-4f photoluminescent emission at 1.23 eV. The low-temperature photoluminescence indicates the association of Yb with other centers to form complexes.
Integrated external cavity quantum well laser array using single epitaxial growth on a patterned substrate
Authors: Chang-Hasnain C. J. , Kapon E. , Harbison J. P. , Florez L. T.
Published: July 2002

We report the monolithic integration of a quantum well laser array and a transparent waveguide with higher band-gap material using a single step of molecular beam epitaxy on a patterned, nonplanar substrate. The substrate has a periodically corrugated patterned section longitudinally adjacent to an unpatterned, planar section. The laser heterostructure on the corrugated section of the substrate has a thicker quantum well and, thus, lower effective band gap than that of the one grown on the planar section. Hence, a waveguide transparent at the laser array emission wavelength is formed on the planar section. We demonstrate phase locking of the otherwise uncoupled laser array using diffraction coupling through the transparent waveguide section. Emission wavelength tuning of ∼80 Å is also obtained using carrier injection into the waveguide section.
Measurement of the electrically induced refractive index change in silicon for wavelength λ=1.3 μm using a Schottky diode
Authors: Evans A. F. , Hall D. G.
Published: July 2002

We report the results of measurements of the electrically induced refractive index change caused by the free-carrier effect in a silicon Schottky diode. We find that for the wavelength λ=1.3 μm, the real part of the refractive index changes by as much as ‖Δn‖∼0.01 for current densities less than 1 A/cm2. This refractive index change produced changes in the input-coupling efficiency as large as 75% in our sample geometry.
Transconductance degradation in silicon field-effect transistors resulting from inversion layer degeneracy
Authors: Kim Dae M. , Qian Feng , Tang Yuan , Blakemore John S.
Published: July 2002

The process parameters used for fabricating a metal-oxide-silicon field-effect transistor (MOSFET) with submicron channel length are shown to lead to a degenerate channel inversion. The Fermi–Dirac statistics inherent in a dense electron gas are incorporated into the MOSFET model and compared with measured transconductance data. Only those electrons within a few kT of the Fermi level contribute to the current, while the Pauli exclusion principle prevents other electrons from participating in conduction. This distinction between conducting and nonconducting electrons in a degenerate gas can bridge in part a large discrepancy existing between observed transconductance and conventional MOSFET theories.
Subpicosecond cooling of photoexcited hot carriers studied by one-beam excite-and-probe Raman scattering
Authors: Kim Dai-sik , Yu Peter Y.
Published: July 2002

A technique using a single picosecond laser beam to excite and probe photoexcited hot electron and hole plasma by inelastic light scattering is proposed. The cooling rate of the hot electrons is determined by varying the pulse width of the laser beam. The technique is illustrated by measuring the subpicosecond cooling of hot carriers in GaAs and InGaAs. The advantages and limitations of the technique are discussed.
Asymmetric strain distributions resulting from deliberately induced misfit dislocations
Authors: Tuppen C. G. , Gibbings C. J. , Hockly M. , Halliwell M. A. G.
Published: July 2002

Misfit dislocations oriented in a specific 〈110〉 direction have been produced in strained Si1−xGex epitaxial layers deposited on Si(001), using sites of localized crystallographic damage as dislocation sources. During a high-temperature anneal, misfit dislocation propagation from a series of parallel saw lines oriented along a particular 〈110〉 direction led to asymmetrically strained material demonstrating an orthorhombic symmetry. Processing conditions required to maximize [110]/[11̄0] asymmetry in the strain distribution are discussed. The distance of a dislocation front emanating from the sites of crystallographic damage during a high-temperature anneal has been used to measure the misfit dislocation glide velocity.
Photosensitization of diamond thin films
Authors: Mort J. , Okumura K.
Published: July 2002

Photosensitization of diamond thin films, prepared by the hot-filament technique, has been achieved with thin overcoatings of hydrogenated amorphous silicon. It is observed that injection of electrons, photogenerated in the amorphous silicon, proceeds with efficiencies approaching unity. To reconcile this with the reported electron energy structures of these two materials, the presence of localized, acceptor-like states 2 eV above the valence band of diamond must be invoked. In addition their density must be sufficiently high to account for the inferred lower limit of 10−8 cm2 /V for the electron range.
Aerosol jet etching of Hg1−xCdxTe
Authors: Jurcik B. J. , Brock J. R. , Trachtenberg I.
Published: July 2002

Aerosol jet etching of Hg1−xCdxTe is reported using a Br2-CH3OH aerosol. The method demonstrates good anisotropy and the etching process induces no change in the electrical properties of the Hg1−xCdxTe.
Study of cooling of hot carriers and intervalley scattering in In0.53Ga0.47As by subpicosecond Raman scattering
Authors: Kim D. S. , Yu P. Y.
Published: July 2002

Subpicosecond laser pulses have been used to excite and probe photoexcited hot-electron plasma in In0.53 Ga0.47 As by Raman scattering. Hot-electron temperatures have been measured as a function of the length of subpicosecond pulses. Cooling of the hot electrons is compared with a model calculation in which the cooling mechanism is dominated by intervalley scattering. The Γ to L intervalley deformation potential in In0.53 Ga0.47 As was determined to be around 3.5×108 eV/cm.
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u epitaxial growth of the GdBa2Cu3O7 superconducting thin films on (100) ZrO2 by magnetron sputtering
Authors: Yi Huai-ren , Wang Rui-lan , Li Hong-cheng , Chen Yaun , Yin Bo , Ron Xi-sheng , Li Lin
Published: July 2002

High-temperature superconductor GdBa2Cu3O7 thin films were epitaxially grown in situ on (100) oriented ytrrium-stabilized zirconia single-crystal substrates by dc magnetron sputtering using a single planar target. All samples prepared in continual 12 runs have zero-resistance transition temperature Tc0 more than 90 K and a transition width 1–2 K. The best films have a Tc0 of 92.5 K, a transition width of 0.7 K, and a critical current density of 1.4×106 A/cm2 at 77 K. The reproducibility is very good. X-ray diffraction spectra analysis in different geometries showed epitaxial growth with the c axis normal to the film surface.
Polymer microstructure waveguides on alumina and beryllium oxide substrates for optical inteconnection
Authors: Chen Ray T. , Wang Michael R. , Jannson Tomasz
Published: July 2002

We report the first high quality optical waveguides (loss <1 dB/cm) on alumina and beryllium oxide substrates. The tunability of the polymer guiding layer refractive index is provided through a recently developed wet processing technique. This procedure changes the waveguide propagation loss from larger than 40 dB/cm to less than 1 dB/cm. Since alumina (Al2O3) and beryllium oxide (BeO) are the major substrates for hybrid mode microwave integrated circuits (HMMICs), realization of such waveguides is useful for optical interconnection and signal processing for HMMIC.
Electrical and structural properties of Si/CrSi2/Si heterostructures fabricated using ion implantation
Authors: White Alice E. , Short K. T. , Eaglesham D. J.
Published: July 2002

Using high dose implantation of Cr+ into (111)-oriented Si, followed by annealing, we have created continuous, buried layers of CrSi2 in Si. The layers are stoichiometric and epitaxially aligned along one of the substrate 〈111〉 directions. Results of temperature-dependent resistivity and Hall measurements on the early layers show that they are p-type degenerate semiconductors consistent with data for bulk samples. More recent layers appear to be single crystal with [0001] parallel to [111] and are n type with lower carrier density.
Self-pumped and double phase conjugation in GaAs with applied dc electric field
Authors: Chua P. L. , Liu D. T. H. , Cheng L. J.
Published: July 2002

Self-pumped and double phase conjugation are first demonstrated in undoped GaAs with applied dc electric field at 1.06 μm wavelength. Phase-conjugate reflectivities of up to 3% and 0.5% respectively, are obtained and other dependences are reported. Reported values of the self-pumped phase-conjugate reflectivity are compared with those of InP.
Time-resolved luminescence of GaAs/AlGaAs heterostructures grown by molecular beam epitaxy on misoriented substrates
Authors: Colocci M. , Gurioli M. , Vinattieri A. , Deparis C. , Massies J. , Neu G.
Published: July 2002

The effects of GaAs substrate misorientation from the (001) plane on the photoluminescence spectra of GaAs/AlGaAs quantum well structures grown by molecular beam epitaxy have been investigated using time-resolved spectroscopy. It is shown, by comparison with a (001) heterostructure having a high impurity content, that the broadening of photoluminescence spectra, observed when the substrate misorientation is towards the (111)As plane, is very unlikely due to a preferential impurity incorporation but is rather originated from the growth mechanism on this type of surface.
Mobility modulation on a modulation-doped structure with an AlAs/GaAs fractional layer superlattice
Authors: Tsubaki K. , Tokura Y. , Susa N.
Published: July 2002

The mobility modulation effect of AlAs/GaAs fractional layer superlattices in an AlGaAs/GaAs modulation-doped structure, which is used for quantum wire and electron wave interference transistors, is investigated by measuring their sheet electron concentration (ns). The ns obtained by the Shubnikov–de Haas oscillation is the number of high-mobility electrons. On the other hand, the ns calculated from structural parameters is the total number of the high- and low-mobility electrons. The relationship between the electron mobility and ns is found to be μ∝(ns − nc)γ, where γ=1 and nc=5.9×1011 cm−2. The mobility modulation part in the transconductance exceeds the electron concentration modulation part by a factor of 3.
Growth dynamics of photosensitive gratings in optical fibers
Authors: LaRochelle S. , Mizrahi V. , Stegeman G. I. , Sipe J. E.
Published: July 2002

We study the growth dynamics of photosensitive fiber gratings assuming a local bleaching model, and demonstrate that sustained grating growth is possible. Good agreement with our experimental results is obtained after including fiber heating effects.
Selective-area electroless copper plating on polyimide employing laser patterning of a catalytic film
Authors: Hirsch T. J. , Miracky R. F. , Lin C.
Published: July 2002

A scanned, focused argon ion laser beam is used to locally heat a thin polymer/palladium film applied to a polyimide-coated substrate, thereby reducing chemically bound palladium to palladium metal. The metallic palladium is resistant to a caustic etchant that removes the unirradiated film; the residual patterned palladium then acts as a catalyst for conventional electroless plating. As an alternate patterning method a laser may be used to selectively deposit the thin polymer film on the substrate from a surrounding liquid solution.
Atmospheric pressure organometallic vapor phase epitaxy growth of high-mobility GaAs using trimethylgallium and arsine
Authors: Hanna M. C. , Lu Z. H. , Oh E. G. , Mao E. , Majerfeld A.
Published: July 2002

Epitaxial layers of GaAs with peak mobilities as high as 200 000 cm2/V s at 50 K have been grown in an atmospheric pressure organometallic vapor phase epitaxy reactor using trimethylgallium (TMG) and arsine. The growth conditions which lead to high-mobility GaAs are described in this letter. Low-temperature photoluminescence and temperature-dependent Hall measurements are used to study the dependence of the incorporation of residual impurities on the growth temperature and arsine partial pressure. Carbon acceptor densities <1014 cm−3 were measured in the highest purity samples.
High peak power picosecond pulse generation from AlGaAs external cavity mode-locked semiconductor laser and traveling-wave amplifier
Authors: Delfyett P. J. , Lee C.-H. , Alphonse G. A. , Connolly J. C.
Published: July 2002

Thin active region single stripe aluminum gallium arsenide traveling-wave amplifiers have been used to generate and amplify 15 ps optical pulses to nearly 50 mW average powers and to peak powers in excess of 3 W. No appreciable temporal pulse distortion is observed after amplification. These peak power levels should prove to be sufficient to induce nonlinear optical effects in fibers.
Picosecond photoconductive response of polycrystalline silicon thin films
Authors: Shu C. , Hu B. B. , Zhang X.-C. , Mei P. , Yang E. S.
Published: July 2002

Using autocorrelation measurement, we have studied the picosecond photoconductivity of as-deposited, fine-grain polycrystalline silicon thin films. A strong correlation between photoconductive decay time and polycrystalline silicon deposition temperature has been observed. The fastest autocorrelated photoconductive response is 9 ps full width at half maximum, and is obtained from a polycrystalline silicon sample deposited at 590 °C. We estimated the carrier mobility from the peak autocorrelated current, as well as from the average photocurrent of a single gap. These two values show a large difference for samples deposited at relatively high temperatures, which can be explained by imperfect metal-semiconductor ohmic contacts.
Infrared erasure of self-organized χ(2) gratings in high germania content optical fibers
Authors: Hibino Yoshinori , Mizrahi Victor , Stegeman George I. , Sudo Shoichi
Published: July 2002

We demonstrate that the self-organized χ(2) grating in a high germania content optical fiber can be erased by prolonged exposure to 1.064 μm radiation only. The decay rate, which is proportional to the fourth power of the 1064 nm intensity, is attributed to two-photon absorption of the second-harmonic light generated in the fiber.
Molecular beam epitaxy grown PbEuSeTe buried-heterostructure lasers with continuous wave operation at 195 K
Authors: Feit Z. , Kostyk D. , Woods R. J. , Mak P.
Published: July 2002

Lattice-matched buried-heterostructure (BH) PbEuSeTe lasers were fabricated using a two-stage molecular beam epitaxy growth procedure. Lasers with 4-μm-wide and 0.6-μm-thick buried PbTe and Pb0.9976Eu0.0024Se0.0034Te0.9966 active layers were grown. Record continuous wave (cw) operating temperatures of 195 and 183 K were measured for BH diode lasers with binary PbTe active layer, and quaternary PbEuSeTe (0.22 at. % Eu) active layer compositions, respectively. For PbTe active layer BH lasers, threshold currents of 3.2 mA (80 K) and 36.2 mA (140 K) were measured in cw operation mode. For Pb0.9976Eu0.0024Se0.0034Te0.9966 BH active layer lasers, threshold currents of 2.9 mA (80 K) and 23.4 mA (140 K) were measured in cw operation mode.
Investigation of carrier transport in graded gap superlattices by time correlated single photon counting
Authors: Lacaita Andrea , Ralph Stephen E. , Capasso Federico , Malik Roger J.
Published: July 2002

Carrier transport in asymmetric superlattice structures is investigated by a photoluminescence technique based on single photon counting. Hole drift times as short as 40 ps have been measured at room temperature in a compositionally graded AlGaAs superlattice with a 540 Å period. Our studies also reveal the complex dynamics of the carriers in these structures and particularly the role of quasi-electric fields, photoinduced fields, and traps. Excellent agreement with previous measurements of charge transport optical nonlinearities based on electro-optic sampling is found.
Enhancement of group III atom interdiffusion by nondopant oxygen implants in In0.53Ga0.47As-In0.52Al0.48As multiquantum wells
Authors: Rao E. V. K. , Ossart P. , Thibierge H. , Quillec M. , Krauz P.
Published: July 2002

We show here that the implants of oxygen, a basically nondopant impurity, after adequate high-temperature annealings (for example, 750 °C, 1 h furnace anneal) lead to a significant interdiffusion of group III atoms in molecular beam epitaxy grown In0.53Ga0.47As-In0.52Al0.48As multiquantum wells (MQWs). Both photoluminescence and Auger electron spectroscopy measurements (coupled to Ar+ ion etching) have been employed to monitor disordering in MQWs implanted with oxygen (5×1013 to 5×1014 ions cm−2) and subsequently annealed using either rapid thermal anneals or long duration furnace anneals. The role of oxygen to enhance group III atom (Al, Ga, and In) interdiffusion is unambiguously established and a tentative explanation based on a possible migration of oxygen in these MQWs is proposed and dissussed.
Density of states of an AlAs/GaAs fractional superlattice in a modulation− doped structure
Authors: Tsubaki K. , Tokura Y. , Susa N.
Published: July 2002

The AlAs/GaAs fractional superlattice in an AlGaAs/GaAs modulation-doped structure, which is used for quantum wire transistors and electron wave interference transistors, is investigated from the viewpoint of the electronic state. A threshold voltage (Vth) difference of 0.27 V between the quantum wire and electron wave interference transistor indicates a periodic potential amplitude of 10 meV. Vth of both these transistors and the flatband voltage (Vfb) calculated from the gate capacitance are obtained at various temperatures between 4.2 and 100 K. The density of states (DOS) is determined from the temperature dependence for Vth of both transistors and Vfb. A DOS below the bottom of the well in the periodic potential is one dimensional, but a DOS between the bottom of the well and the top of the barrier in the periodic potential is two dimensional.
Excitonic effects in gain and index in GaAlAs quantum well lasers
Authors: Kesler Morris P. , Harder Christoph
Published: July 2002

Spontaneous emission and gain measurements in GaAlAs single quantum well lasers are presented. The gain is derived from the spontaneous emission detected through an opening in the top metallic contact of the lasers. Excitonic effects are seen in the gain (absorption) spectra for low carrier densities, and the step-like nature of the two-dimensional density of states is evident. From the gain spectra, refractive index changes are derived via a Kramers–Kronig transformation, and this is used to evaluate the linewidth enhancement factor as a function of photon energy.
Chemical beam epitaxial growth of strained carbon-doped GaAs
Authors: Chiu T. H. , Cunningham J. E. , Ditzenberger J. A. , Jan W. Y.
Published: July 2002

We report an investigation of the growth characteristics of GaAs by chemical beam epitaxy using trimethyl-Ga and arsine. The growth rate behaviors as a function of temperature, As overpressure, and alkyl arrival rate are qualitatively similar to those using triethyl-Ga with differences that can be explained by differences in the alkyl-Ga bond strength. A unified description of the growth kinetics assuming a unimolecular reaction mechanism is possible. Lattice parameter is found to decrease with increasing carbon concentration. A high quality GaAs/GaAs:C doping superlattice has been prepared. Although the composition modulation is too small for x-ray diffraction measurement, the structural deformation gives rise to satellite peaks with order n up to ±7 observed for the first time. X-ray analysis of the superlattice after annealing has been employed to study the carbon diffusion in GaAs.
InP/InGaAs double heterojunction bipolar transistors grown by metalorganic vapor phase epitaxy with sulfur delta doping in the collector region
Authors: Tokumitsu E. , Dentai A. G. , Joyner C. H. , Chandrasekhar S.
Published: July 2002

Sulfur δ doping in InP by metalorganic vapor phase epitaxy is reported. A peak carrier concentration of 7×1017 cm−3 with a full width at half maximum of 30 nm has been measured by the electrochemical capacitance-voltage technique. It is shown that by inserting the δ-doping spike in the collector region of InP/InGaAs double heterojunction transistors, the effective barrier height at the base-collector interface can be reduced without increasing the base-collector capacitance and excellent transistor characteristics can be realized.
Digital chemical vapor deposition of SiO2
Authors: Nakano M. , Sakaue H. , Kawamoto H. , Nagata A. , Hirose M. , Horiike Y.
Published: July 2002

The repetitive cycles of a few monolayers hydrogenated silicon deposition and its oxidation has been employed for the growth of SiO2. The surface reaction is promoted by an alternate irradiation of silicon hydride radical beam produced by the upstream pulsed microwave discharge of SiH4 and discharged oxygen beam. The deposition rate is controlled by the flow velocity of silane gas jet and substrate temperature. It is shown that the deposition species ejected with supersonic velocity into a high vacuum reactor conformably fills the SiO2 film into a deep Si trench.
Three-terminal quantum box resonant tunneling Josephson field-effect switch
Authors: van Houten H.
Published: July 2002

A new type of three-terminal hybrid superconductor-semiconductor switch is proposed, based on the combination of an electrostatically tunable quantum resonant or ballistic device with superconducting source and drain contacts. The current-voltage characteristics of the quantum box version of such a device are obtained from an equivalent circuit model.
Refractive index changes in a GaAs multiple quantum well structure produced by impurity-induced disordering using boron and fluorine
Authors: Hansen S. I. , Marsh J. H. , Roberts J. S. , Gwilliam R.
Published: July 2002

The effect of boron and fluorine impurity-induced disordering on the refractive index of AlxGa1−xAs multiple quantum well waveguides has been studied experimentally using a grating coupler formed in low-index material. Substantial changes ≳1% in the refractive index, were obtained in partially disordered material over the measured wavelength range. Fluorine was found to produce larger changes than boron for similar annealing conditions.
Optical and electrical properties of GaAs light-emitting diodes grown on Si substrates by a hybrid method of molecular beam and liquid phase epitaxies
Authors: Yazawa Y. , Minemura T. , Asano J. , Unno T.
Published: July 2002

Light-emitting diodes (LEDs) have been fabricated on GaAs-on-Si substrates grown by a hybrid method which combines molecular beam epitaxy (MBE) and liquid phase epitaxy. The LEDs had a low reverse leakage current and high stability of light intensity for an aging operation compared with MBE-grown LEDs. These results are attributed to a higher crystallinity in the hybrid-grown GaAs layers on Si substrates.
Direct detection of microdefects in beta barium metaborate bulk crystals by light scattering tomograph
Authors: Hou Jianguo , Tan Qiguang , Zhao Qinnan , Wu Baichang , Chen Chuangtian
Published: July 2002

A second-harmonic generation of a Q-switched Nd:YAG laser at λ=530 nm was focused into the polished beta barium metaborate crystals, and the scattering light was collected by a motor-driven camera at 90° direction. This arrangement allows direct and nondestructive detection of microdefects in bulk crystals. Dislocation lines decorated by impurity atoms could be seen by a laser beam illuminating with the power intensity of about 0.5 MW/cm2, while microinclusions of about 1–5 μm in size could be observed with much lower laser intensity.
In-based p ohmic contacts to the base layer of AlGaAs/GaAs heterojunction bipolar transistor
Authors: Ren F. , Pearton S. J. , Hobson W. S. , Fullowan T. R. , Emerson A. B. , Schleich D. M.
Published: July 2002

A reliable p ohmic contact for AlGaAs/GaAs heterojunction bipolar transistor (HBT) using AuBe-In/Ag/Au is presented. Excellent morphology after annealing at 400 °C for 20 s was observed and a transfer resistance of 0.095 Ω mm obtained on p+-GaAs (1×1019 cm−3). Silver acts as a diffusion barrier to prevent Au spikes which will degrade the performance of the thin base layer HBT. The indium layer is highly desirable to reduce the contact resistance by forming the InGaAs phase at metal-GaAs interfaces. Beryllium is the p-type dopant and a top gold layer is used to lower the sheet resistance of the contact metals. The mode of current transport is dominant by tunneling through the barrier due to field emission in the heavily doped materials.
Superconducting Bi-Sr-Ca-Cu-O films formed by diffusion of metallic bismuth on Sr2Ca2Cu4Oy substrates
Authors: Lee Kiejin , Park Gwangseo
Published: July 2002

The superconducting low Tc Bi2Sr2CaCu2Oy films of 1 μm in thickness have been prepared on Sr2Ca2Cu4Oy substrates by thermal evaporation of metallic Bi layer and heat treatment at 830 ° C for a few minutes in air. The transition behavior and morphology of the films were studied by resistivity measurements and scanning electron microscopy. The zero resistance temperature Tcz and critical current density Jc at 70 K were observed to be 78 K and 103 A/cm2, respectively. It is found that the superconducting films are formed by the reaction between liquid phase (Bi2O3) and solid phase (substrate), and that the dendrite structure is produced in the cross section of the films as it is generally observed in the liquid phase sintering.
High-power tunable operation of AlGaAs/GaAs quantum well lasers in an external grating cavity
Authors: Gavrilovic P. , Smirnitskii V. B. , Bisberg J. , O’Neill M.
Published: July 2002

Data are presented on operation of 100 μm aperture gain-guided single quantum well laser diodes in an external grating cavity. A maximum power of 550 mW is coupled out of the cavity with an efficiency of 0.51 W/A. The laser emission has a linewidth of ≲1 Å and is tunable from 7950 to 8450 Å for the specific laser diodes used in this study. The output beam is collimated in the direction perpendicular to the p-n junction, and exhibits a divergence of 0.4° parallel to the p-n junction.
Modification of magnetic property in Mn-Zn ferrite by MeV ion implantation
Authors: Lu Yong-Feng , Takai Mikio , Namba Susumu , Sanda Hiroyuki , Chayahara Akiyoshi , Satou Mamoru
Published: July 2002

The magnetic property of Mn-Zn ferrite has been modified by Si+ and Au+ implantation at 3 MeV to doses of 1×1016 and 1×1017 cm−2, respectively. The magnetization of the implanted surface layer decreased to zero when the ion implantation induced vacancy number was high enough. The decrease in magnetization is found to be related to the vacancy number in the implanted layer. The surface magnetization of the implanted layer can be completely recovered by thermal annealing at 850 °C for 30 min.
Generation of 170 GHz optical sidebands of a single-mode semiconductor laser by nonlinear intracavity interaction
Authors: Nietzke R. , Elsässer W. , Baranov A. N. , Wünstel K.
Published: July 2002

We demonstrate the generation of optical sidebands with a frequency separation of 170 GHz by nonlinear optical intracavity interaction of light from a 1.3 μm distributed feedback laser with the population pulsations caused by the longitudinal mode beating of a broad-area laser and demonstrate a cavity-enhanced response by approximately 45 dB.
ArF excimer laser induced photolytic growth of Si homoepitaxial films from Si2H6 at 330 °C
Authors: Lian S. , Fowler B. , Bullock D. , Banerjee S.
Published: July 2002

This letter discusses low-temperature Si homoepitaxy on Si(100) substrates by the photolytic decomposition of Si2H6 by the 193 nm emission of an ArF excimer laser. The chemical vapor deposition process at growth rates from 0.5–4 Å/min is performed in an ultrahigh vacuum chamber which, along with an ex situ HF dip and a novel in situ hydrogen clean using laser excitation, results in minimization of oxygen and carbon contamination which inhibits Si epitaxy. The growth involves photolytic decomposition of Si2H6 and the generation and adsorption of SiH2 precursors on the hydrogenated Si surface, which is the rate limiting step. Very low defect density films in terms of stacking faults and dislocation loops (less than 106 cm−2), and excellent crystallinity have been grown at 330 °C and 0.5 W laser power, as confirmed by Schimmel etching and Nomarski microscopy, transmission electron microscopy, electron diffraction and in situ reflection high-energy electron diffraction.
Optimal GaAs(100) substrate terminations for heteroepitaxy
Authors: Farrell H. H. , Tamargo M. C. , de Miguel J. L.
Published: July 2002

The quality of heteroepitaxial growth of II-VI materials on III-V substrates, such as ZnSe on GaAs(100), depends strongly on the atomic structure and stoichiometry of the substrate. We define and describe those structures that optimize heteroepitaxial interface growth on GaAs(100) and related surfaces, and propose specific models for the c(6×4), ‘‘3×1’’, (4×6), an As-lean version of the (2×4), and Se substitutional such as the (4×3). It is proposed that a good heteroepitaxial interface, with no extraneous fields and no charge imbalance, is achieved with substrate structures which lead directly to the appropriate interface stoichiometry.
Silicon epitaxial growth on Si-TaSi2 eutectic composite substrates
Authors: Levinson M. , Tabasky M. , Sung C. , Hamill G. , Matthiesen D. H. , Ostreicher K. , Ditchek B. M.
Published: July 2002

Epitaxial layers of Si were grown by atmospheric chemical vapor deposition on two-phase, Si-TaSi2 eutectic composite substrates. Characterization by scanning electron microscopy, transmission electron microscopy, and x-ray double-crystal rocking curve analysis showed very good crystallographic and microstructural quality. Epilayer areas lying over the TaSi2 regions of the substrate in most cases showed no defect structures. In some cases, pores or dislocations originating at the Si-TaSi2 interface were observed. Epilayers such as these should enable the integration of conventional silicon devices with the novel ones made possible by these unique composite structures.
Wavelength-dependent amplification characteristics of femtosecond erbium-doped optical fiber amplifiers
Authors: Kurokawa Kenji , Nakazawa Masataka
Published: July 2002

Amplification characteristics of erbium-doped optical fiber amplifier have been investigated using femtosecond soliton pulses with various wavelengths. Soliton trapping is not observed for 210 fs input pulses at 1.535 μm but the soliton self-frequency shift occurs along with the pulse-width narrowing. When the input pulse width is 470 fs, the soliton pulse is amplified by the optical gain at 1.535 μm, where the gain bandwidth is broader than the bandwidth of the input pulse. Amplification characteristics at other nonresonant wavelengths are also investigated using a femtosecond soliton pulse.
Electronic Raman scattering from acceptors and correlation with transport properties in Li-doped ZnSe layers
Authors: Olego D. J. , Marshall T. , Cammack D. , Shahzad K. , Petruzzello J.
Published: July 2002

Electronic Raman scattering (ERS) from holes bound to Li acceptors was studied in ZnSe layers and correlated with the net acceptor concentration NA−ND determined by capacitance versus voltage measurements. The layers were grown by molecular beam epitaxy on GaAs substrates and were doped in situ to NA−ND concentrations ranging from high 1015’s to low 1017’s cm−3. The ERS spectra reveal several transitions between the ground 1S and shallower S and P bound states of the Li acceptors as well as transitions to a continuum of delocalized valence-band states. Values of excitation energies for the bound hydrogenic states and the ionization energy of the acceptors were measured. The strength of the ERS signal normalized to the phonon scattering depends linearly on NA−ND. This relationship can be exploited in contactless characterization of p-type ZnSe.
In situ stress measurements of ion-assisted MgF2 and SiOx thin films
Authors: Martin P. J. , Netterfield R. P. , Kinder T. J. , Stambouli V.
Published: July 2002

An in situ stress measuring interferometer and in situ ellipsometer have been used to study the stress evolution and optical properties of MgF2 and SiOx optical thin films prepared by electron beam evaporation and 100 eV O+2 ion-assisted deposition (IAD). The maximum stress observed in thermal evaporation of MgF2 was found to be 240 MPa. The tensile stress in evaporated MgF2 could be modified by IAD to compressive stress. The optical properties and stress of SiOx were modified by IAD and also by the presence of a partial pressure of oxygen. The combination of stress interferometry and ellipsometry is shown to be a powerful method of monitoring and controlling the properties of optical materials deposited by IAD.
Al-Ga monolayer lateral growth observed in situ by scanning electron microscopy
Authors: Kanisawa Kiyoshi , Osaka Jiro , Hirono Shigeru , Inoue Naohisa
Published: July 2002

The characteristics of an Al-Ga top layer on AlGaAs and GaAs surfaces during alternate supply molecular beam epitaxy (MBE) growth are studied by in situ observation using a MBE scanning electron microscope (SEM) hybrid system. It is found that an Al-Ga alloy top layer has a pseudo-self-limiting nature. It is also found that the migration distance of Al-Ga atoms on an Al-Ga alloy top layer is as large as 10 μm. By utilizing these characteristics, a μm-scale Al-Ga monolayer lateral growth process is realized, and the lateral growth rate, about 1 μm/s, is observed. Comparison of this growth with migration-enhanced epitaxy is discussed.
Nondisruptive oxide overlayer growth on GaAs(110)
Authors: Kroll G. H. , Ohno T. R. , Weaver J. H.
Published: July 2002

Three different ways of forming oxide overlayers on GaAs(110) have been examined with x-ray photoemission. First, Cr atoms were deposited onto cleaved GaAs(110) at 300 K, producing a disrupted region over which Cr metal grew. Subsequent exposure to O2 resulted in an inhomogeneous overlayer with areas of thick Cr2O3-like oxides in addition to As and Ga oxides. GaAs oxidation was enhanced by Cr-induced surface disruption, but there was no evidence of a catalytic process. Second, metallic clusters of Cr containing hundreds of atoms were condensed onto GaAs(110). In this case, no substrate disruption was observed at low temperature. O2 exposure resulted in Cr2O3 formation with small amounts of Ga2O3 and no detectable As2O3. Third, Cr atoms and O2 molecules were condensed onto a Xe buffer layer on GaAs(110) to produce Cr2O3-like species out of contact with the semiconductor. Buffer layer desorption brought these Cr2O3 aggregates into contact with the substrate. The overlayer produced in this manner was abrupt, and there was no evidence of GaAs oxidation.
Transmission electron microscopy characterization of the initial stage of epitaxial growth of GaP on Si by low-pressure metalorganic chemical vapor deposition
Authors: Soga T. , George T. , Suzuki T. , Jimbo T. , Umeno M. , Weber E. R.
Published: July 2002

The initial stage of epitaxial growth of GaP on Si by low-pressure metalorganic chemical vapor deposition was characterized by transmission electron microscopy. The growth mode changes from three-dimensional to two-dimensional with increasing V/III ratio. GaP on Si grown at a low V/III ratio of 800 contains many dislocations, stacking faults, and microtwins; however, a significant reduction in the density of these defects is observed in GaP grown at high V/III ratio of 3200.
Improvement of the carrier confinement by double-barrier GaAs/AlAs/(Al,Ga)As quantum well structures
Authors: Neu G. , Chen Y. , Deparis C. , Massies J.
Published: July 2002

The insertion of few AlAs monolayers at the interfaces between a GaAs quantum well and (Al,Ga)As barriers gives rise to a new type of structure which is well described as a double-barrier quantum well. It is shown that only one or two AlAs monolayers are sufficient to significantly increase the confinement energies. Our results are discussed in the light of low-temperature photoluminescence experiments and are well described in the framework of numerical calculations based on the envelope function formalism.
Quantitative determination of high-temperature oxygen microprecipitates in Czochralski silicon by micro-Fourier transform infrared spectroscopy
Authors: Borghesi A. , Geddo M. , Pivac B. , Sassella A. , Stella A.
Published: July 2002

Oxygen content in the bulk of Czochralski silicon was analyzed by using micro-Fourier transform infrared spectroscopy in a transversal wafer cross-section configuration. This technique locally distinguishes between interstitial oxygen and oxygen precipitates in wafers used as substrates for epitaxial layer growth. Systematic measurements performed in the 5000–700 cm−1 wavenumber range clearly indicate the presence of oxygen microprecipitates in the bulk of the processed silicon wafers. Quantitative determination of oxygen precipitate density is reported and compared with the measured interstitial oxygen concentration.
Layer-by-layer epitaxial growth of a Bi2Sr2CuO6 thin film on a Bi2Sr2CaCu2O8 single crystal
Authors: Matsumoto Takuya , Kawai Tomoji , Kitahama Katsuki , Kawai Shichio , Shigaki Ichiro , Kawate Yoshio
Published: July 2002

The epitaxial growth of a Bi2Sr2CuO6 (2201) thin film on a Bi2Sr2CaCu2O8 (2212) single crystal has been performed using computer-controlled laser molecular beam epitaxy. The surface of the 2212 single crystal used as the substrate is smooth and invariant under the growth condition at 640 °C in NO2 pressure of 1×10−5 mbar. The growth process of the 2201 film has been observed by in situ reflection high-energy electron diffraction (RHEED), and the layer-by-layer growth of the 2201 phase is confirmed by the oscillation of RHEED intensities. During the growth, a modulated surface structure which is characteristic of the Bi cuprate crystals is always present.
130 ps recovery of all-optical switching in a GaAs multiquantum well directional coupler
Authors: LiKamWa P. , Miller A. , Roberts J. S. , Robson P. N.
Published: July 2002

A significantly improved recovery time of 130 ps has been achieved in an all-optical zero-gap directional coupler containing multiple quantum wells. The mechanism for the all-optical switching is due to free-carrier induced refractive nonlinearities at near-band-gap resonant frequencies. The large reduction in the switch recovery time was obtained by the application of an external dc bias which sweeps out the carriers from the quantum wells. From our experimental results on the laser pulse width limited switch-up time of 2 ps, we deduce that the contribution of self-electro-optic effect nonlinearity is negligible in this case.
Low Au content thermally stable NiGe(Au)W ohmic contacts to n-type GaAs
Authors: Lustig Naftali , Murakami Masanori , Norcott Maurice , McGann Kevin
Published: July 2002

Thermally stable low-resistance ohmic contacts to n-type GaAs incorporating a very thin layer of Au in conjunction with a layered Ni/Ge/W structure are reported. A minimum contact resistance of 0.16 Ω mm was obtained for contacts annealed at ∼650 °C. The contact resistance was ∼0.3 Ω mn after thermal stressing at 400 °C for 20 h. Cross-sectional transmission electron microscopy reveals a uniformly reacted layer only ∼34 nm deep, making these contacts significantly shallower and more homogeneous than eutectic-based AuGeNi contacts. X-ray diffraction shows the presence of NiGe, β-AuGa, and W phases in the reacted contacts. The volume fraction of the low melting point β-AuGa phase is considerably reduced from that reported for eutectic-based AuGeNi contacts. This, along with the presence of the high melting point NiGe compound, explains in part the improved thermal stability and morphology of the low Au content ohmic contacts.
Infrared absorption in boron-doped diamond thin films
Authors: Mort J. , Machonkin M. A. , Okumura K.
Published: July 2002

Detailed studies of infrared absorption in nominally undoped and boron-doped, free-standing diamond thin films are reported. Difference measurements reveal absorption at 1300 cm−1 (0.16 eV) due to boron-induced single phonon, vibronic excitations. A relatively sharp peak at about 2420 cm−1 (0.30 eV), a stronger, broader band centered at 3060 cm−1 (0.38 eV), and a weak, broad peak at 4200 cm−1 (0.52 eV), are identified as electronic transitions, with or without phonon assistance, of the boron acceptor. These results provide important confirmation of the hitherto presumed substitutional nature of boron doping and recent suggestions concerning electronic transport mechanisms in diamond thin films.
Wavelength switching of picosecond pulse (<10 ps) in a quantum well laser and its all-optical logic gating operations
Authors: Sogawa T. , Arakawa Y.
Published: July 2002

We developed a novel technique to switch the lasing wavelength of picosecond pulses in an optically pumped quantum well laser by utilizing spatially localized and homogeneous excitation. The applications of these phenomena to ultrafast logic gating operations are successfully demonstrated.
Degenerate four-wave mixing in rhodamine doped epoxy waveguides
Authors: Rossi B. , Byrne H. J. , Blau W.
Published: July 2002

Self-diffraction from laser-induced gratings is observed in a 13 μm-thick film of rhodamine B doped epoxy. The decay of the grating is measured to be 2.05 ns. Degenerate forward four-wave mixing in a guided geometry is observed by coupling out all beams after propagation over 1 mm. At 595 nm the third-order nonlinear susceptibility of the film is measured to be 1.5×10−19 m2 V−2.
Removal of the sulfur passivation overlayer on a (NH4)2Sx-treated GaAs surface by vacuum-ultraviolet irradiation
Authors: Takakuwa Yuji , Niwano Michio , Fujita Shinya , Takeda Yuki , Miyamoto Nobuo
Published: July 2002

Effects of photon irradiation on the chemical state of a (NH4)2Sx-treated GaAs surface have been investigated using photoemission and photon-stimulated desorption (PSD) spectroscopic techniques with synchrotron radiation (SR). It is shown that a sulfur-passivation overlayer on the (NH4)2Sx-treated GaAs surface is readily removed by irradiating SR in the vacuum-ultraviolet (VUV) region onto the surface, suggesting the possibility of cleaning the sulfur-passivated GaAs surface by VUV irradiation. The dominant PSD ion product that desorbs from the sulfur-passivated GaAs surface during VUV irradiation is found to be H+. No desorption of sulfur ions is observed, which suggests that sulfur adatoms desorb as neutral species.
Effect of scattering by native defects on electron mobility in modulation-doped heterostructures
Authors: Walukiewicz W. , Haller E. E.
Published: July 2002

The effect of scattering by native defects on carrier mobility in modulation-doped heterostructures is calculated. The concentration of the defects is determined using the amphoteric native defect model. It is shown that the Fermi level induced reduction of the defect formation energy leads to an increased incorporation of native defects and reduced mobility in AlGaAs/GaAs inverted modulation-doped heterostructures. This new mechanism explains the experimentally observed difference in the values of electron mobilities in normal and inverted modulation-doped heterostructures. The effects of native defects on the carrier mobilities in heterostructures based on other semiconductor systems are also discussed.
Bloch states of electrons in a corrugated quantum channel in a magnetic field
Authors: Lent Craig S. , Leng Manhua
Published: July 2002

We calculate the band structure of a long ballistic channel whose width is modulated periodically in the presence of a perpendicular magnetic field. The channel is narrowed on one side only, the other wall remaining straight. At zero magnetic field, the periodic modulation of the width produces miniband gaps. As the magnetic field is increased, the gaps disappear. The band structure at high fields consists of free-electron-like bands associated with magnetic edge states, and flatbands associated with localized Landau levels. The asymmetry in the walls causes electrons moving through the channel in one direction to have a different effective mass from electrons moving in the opposite direction.
The effect of oxygen on the thermal stability of Si1−xGex strained layers
Authors: Noble D. B. , Hoyt J. L. , Nix W. D. , Gibbons J. F. , Laderman S. S. , Turner J. E. , Scott M. P.
Published: July 2002

The thermal stability of Si1−xGex strained layers containing 2×1020 oxygen atoms/cm3 is compared with that of similar layers (same Ge fraction and film thickness) containing more than two orders of magnitude less oxygen. For the layers with high oxygen levels, no misfit dislocations were found in films as thick as two times the theoretical equilibrium critical thickness, after annealing at 850 °C for 4 min. In contrast, dislocations were found in the layers with low oxygen levels at thicknesses very near the equilibrium critical thickness after the same anneal. X-ray measurements of lattice constants in high and low oxygen films of similar Ge content indicate that oxygen does not substantially change the amount of strain in the layers. Oxygen appears to impede the kinetics of dislocation formation.
New magnesium doping source for metalorganic chemical vapor deposition: Octamethyldialuminummonomagnesium
Authors: Hatano Ako , Izumiya Toshihide , Ohba Yasuo
Published: July 2002

Octamethyldialuminummonomagnesium (an adduct of trimethylaluminum and dimethylmagnesium) is proposed as an alternative candidate for an Mg doping source in metalorganic chemical vapor deposition. Water cooling for the reactor wall was important to prevent predecomposition of the adduct. Almost flat doping profiles were obtained independent of Mg concentration. Long doping tails were not observed. The doping efficiency was independent of substrate temperature between 600 and 700 °C, indicating a lower decomposition temperature for this Mg source. It was suggested that carrier concentration control can be improved by removing Si containing impurities from this Mg source.
Investigation of lateral straggling of Hg ions in Si3N4 by normal and glancing angle Rutherford backscattering
Authors: Wang Ke-Ming , Zao Qing-Tai , Shi Bo-Rong , Wang Zhong-Lie , Liu Xiang-Dong , Liu Ji-Tian
Published: July 2002

200 keV Hg ions were implanted in Si3N4 at different angles of 0°, 45°, and 75°. The lateral straggling of Hg ions in Si3N4 was studied by glancing angle and normal Rutherford backscattering of 2.1 MeV He ions. The obtained result is compared with the Monte Carlo code trim ’89. The lateral straggling is found to be in good agreement with the prediction.