bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray photoemission and Raman scattering spectroscopic study of surface modifications of silicon induced by electron cyclotron resonance etching
Authors: Yapsir A. S. , Oehrlein G. S. , Fortuño-Wiltshire G. , Tsang J. C.
Published: July 2002

Surface modifications of silicon induced by electron cyclotron resonance (ECR) etching with CF4 is studied using x-ray photoemission spectroscopy and Raman scattering techniques. It is shown that a silicon sample etched by ECR exhibits a thinner surface residual layer compared to those exposed to reactive ion etching (RIE) or hybrid ECR/RIE. Evidence of plasma-induced structural disorder in the silicon surface was only observed in the RIE-etched sample.
Excellent uniformity of threshold voltage of Si planar-doped AlInAs/GaInAs heterointerface field-effect transistors grown by metalorganic chemical vapor deposition
Authors: Ishikawa H. , Shibata H. , Kamada M.
Published: July 2002

Si planar-doped AlInAs layers grown by metalorganic chemical vapor deposition (MOCVD) showed an excellent uniformity in doping concentration. It was caused by the saturation of the doping concentration in the high doping region. Applying this planar doping to the AlInAs/GaInAs heterointerface field-effect transistor (HIFET), the variation of the threshold voltage (Vth) due to unevenness of distribution of doping concentration was reduced to values below 50 mV over a 2-in.-diam wafer.
Nucleation enhancement of diamond synthesized by combustion flame techniques
Authors: Ravi K. V. , Koch C. A.
Published: July 2002

The nucleation density and the morphology of diamond crystals and films, synthesized by the combustion flame technique, are shown to be strongly influenced by the nucleation processes at work. Nucleation of diamond on a mechanically abraded molybdenum surface results in well-formed cubo octahedrons with a relatively low nucleation density. Nucleation on an initially formed, diamond-like carbon layer markedly increases the nucleation density and alters the morphology of the diamond crystals and film. The enhancement of nucleation by diamond-like carbon layers is postulated to be a result of the high surface defect density and the high hydrogen concentration of these materials.
In situ monitoring of a laser-induced etched grating on InP: Thin-film cell configuration
Authors: Grebel H. , Iskandar B. , Pien P. , Sheppard K.
Published: July 2002

On-line, first-order light diffraction from a laser-induced etched grating in a thin-film cell configuration is investigated. It is suggested that a layer of dissolved reaction products interferes with the in situ light scattering measurements.
Characterization of diamond-like films using electron probe microanalysis
Authors: Pivin J. C. , Spirckel M. , Allouard M. , Rautureau G.
Published: July 2002

Amorphous carbon films were deposited onto Si, SiC, and Ti alloys by implanting low-energy C+ ions, laser ablation, or double ion beam sputtering (DIBS). Their soft x-ray emission spectra were recorded by means of an electron probe microanalyzer (EPMA). Comparison of the energy position of peaks with characteristic spectra of various standards has shown that the short range order in films formed by 2 keV C+ implantation or laser ablation was about the same as in diamond. On the contrary, DIBS films and implantation films formed at lower energies were rather graphite-like. The former were constituted of true diamond-like carbon, since other analysis indicated that they were free of H and O contamination and that a carbide of the substrate species did not grow. It is concluded that EPMA is a valuable method for characterizing the bonding in carbon films.
Trench Pd/Si metal-oxide-semiconductor Schottky barrier diode for a high sensitivity hydrogen gas sensor
Authors: Fang Y. K. , Hwang S. B. , Lin C. Y. , Lee C. C.
Published: July 2002

The structure and hydrogen gas sensing properties of a trench Pd-thin oxide-Si Schottky diode are studied and compared with a planar one. The trench diode possesses additional vertical surface area and a large number of interface traps induced by injected hydrogen ions. The additional vertical surface area enlarges the entrance of H2 molecules, and the generated middle traps enhance the carrier tunneling. Also, the generated shallow traps can catch the carrier to form a thin surface charge layer and lower the barrier. The sensitivity of the trench diode is thus higher than that of the planar diode under room-temperature operation.
Observation of an ordered structure in the initial stage of Ge/Si heteroepitaxial growth
Authors: Ohshima N. , Koide Y. , Itoh K. , Zaima S. , Yasuda Y.
Published: July 2002

An ordered structure with the double periodicity in a 〈111〉 direction has been found by in situ reflection high-energy electron diffraction observation in the initial stage of Ge films grown on (100)Si and (811)Si substrate surfaces by GeH4 gas source molecular beam epitaxy. The ordered structure is formed on {111} planes parallel to the side planes of 〈011〉 steps on {811} facets of Ge growing islands on both substrates. The formation is observed at substrate temperatures of 300–700 °C and is considered to result from solid phase reactions at the interfaces during growth.
XeCl excimer laser ablation of a polyethersulfone film: Dependence of periodic microstructures on a polarized beam
Authors: Niino Hiroyuki , Shimoyama Masashi , Yabe Akira
Published: July 2002

Highly periodic stable microstructures appeared on the surface of polyethersulfone (PES) by XeCl excimer laser ablation with a single polarized beam in ambient air. Its formation mechanism was investigated using the time-resolved light scattering technique with the pulsed light of an XeF excimer laser. In addition to the polarization of the ablating beam, thermal processes on the etched surface play a significant role in microstructure formation.
Formation mechanism study of REBa2Cu4O8+δ (RE=Y and Dy) accelerated by nitric acid
Authors: Hurng W.-M. , Wu S. F. , Shei C. Y. , Huang Y. T. , Lee W. H.
Published: July 2002

An accelerated formation of REBa2Cu4O8+δ (RE=Y and Dy) was observed as a suitable amount of nitric acid was added. This provides an excellent route for preparing high- purity REBa2Cu4O8+δ in ∼ 30 h. X-ray diffraction and thermal analyses (TGA/DTA) were conducted to reveal the formation mechanism. The addition of nitric acid did not change the reaction routes but formed more Ba2Cu3O5 which might play an important role for the formation of REBa2Cu4O8+δ. Magnetization data confirmed the Tc’s of 80 and 75 K for as-prepared Y-124 and Dy-124, respectively.
Scanning tunneling microscopy of the Abrikosov flux lattice with ferromagnetic probes
Authors: Berthe R. , Hartmann U. , Heiden C.
Published: July 2002

Using a low-temperature scanning tunneling microscope spatial variations of the current-voltage characteristics have been investigated on NbSe2 single crystals employing PtIr and ferromagnetic Ni tips. At 4.2 K a clear superconducting energy gap is visible even when tunneling through the Ni tip. After field-induced transfer of the sample into the superconducting mixed state a complete Abrikosov flux lattice is imaged for both types of probes by recording the tunneling current at a fixed voltage within the superconducting gap. Comparison of the images obtained by the two probe materials clearly shows that no distortion of the flux lattice is produced by magnetostatic interactions between the ferromagnetic tip and the individual vortices. This provides the basis for future investigations of flux distributions in superconductors by magnetic force microscopy.
Optical characterization of silicon-on-insulator material obtained by sequential implantation and annealing
Authors: Pérez A. , Samitier J. , Cornet A. , Morante J. R. , Hemment P. L. F. , Homewood K. P.
Published: July 2002

The optical characterization of silicon-on-insulator structures formed by sequential implantation and annealing (SIA) has been carried out. The infrared transmission spectra show peaks characteristic of a thermal oxide, and confirm the high quality of the buried oxide. Moreover, the spectra obtained from these SIA samples, in comparison to those obtained from equivalent samples made with a single implant, show a shift of the main absorption peak to higher wave numbers, which can be attributed to excess oxygen. The higher concentration of oxygen in the SIA samples is corroborated by photoluminescence measurements which show the presence of dislocation-related bands broadened by the presence of oxygen.
Epitaxial Tl2CaBa2Cu2O8 thin films with low 9.6 GHz surface resistance at high power and above 77 K
Authors: Hammond R. B. , Negrete G. V. , Bourne L. C. , Strother D. D. , Cardona A. H. , Eddy M. M.
Published: July 2002

We report measurements of the dc and microwave properties of epitaxial thin films of Tl2CaBa2Cu2O8 on LaAlO3. ac magnetic susceptibility measurements yield critical temperatures at the transition midpoint Tc∼100 K and 10–90% transition widths of ∼1.0 K. We observed a critical current density of 1.06×106 A/cm2 at 77 K measured by dc transport. We measured a low-power surface resistance of Rs=0.2 mΩ at 9.55 GHz and 77 K. This is ∼50 times lower than oxygen-free high-conductivity (OFHC) Cu at the same frequency and temperature. At 90 K, RS rises to 0.4 mΩ, and at 95 K, RS=0.7 mΩ. We measured the microwave power dependence of RS at 77, 90, and 95 K. At high microwave field (≳30 G, 77 K) Rs=0.8 mΩ, more than ten times lower than OFHC Cu.
Silver-covered diffraction gratings as possible high-efficiency laser driven photoemitters
Authors: Sabary F. , Dudek J. C. , Septier A. , Granet G.
Published: July 2002

We propose to use silver-covered optical diffraction gratings as possible laser-driven electron sources. Such structures allow surface plasma waves excitation and consequently an enhancement of the photoemission sensitivity. The latter can easily be tuned with the wavelength of the excitation laser by varying the incidence angle. Using a commercial diffraction grating, we obtained after a cesium activation, a quantum yield higher than 1% at the wavelength of a frequency tripled YAG laser (λ=355 nm) for the incidence angle corresponding to the plasmon resonance.
Native-oxide masked impurity-induced layer disordering of AlxGa1−xAs quantum well heterostructures
Authors: Dallesasse J. M. , Holonyak N. , El-Zein N. , Richard T. A. , Kish F. A. , Sugg A. R. , Burnham R. D. , Smith S. C.
Published: July 2002

Data are presented showing that the native oxide that can be formed on high Al composition AlxGa1−xAs (x≳0.7) confining layers on AlyGa1−yAs-AlzGa1−zAs (y≳z) superlattices or quantum well heterostructures serves as an effective mask against impurity diffusion (Zn or Si), and thus against impurity-induced layer disordering. The high quality native oxide is produced by the conversion of high Al composition AlxGa1−xAs (x≳0.7) confining layers, which can be grown on a variety of heterostructures, via H2O vapor oxidation (≳400 °C) in an N2 carrier gas.
Design parameters of a resonant infrared photoconductor with unity quantum efficiency
Authors: Farhoomand Jam , McMurray Robert E.
Published: July 2002

A new concept for an infrared photoconductor with enhanced characteristics, such as unity quantum efficiency, high photoconductive gain, and very low noise equivalent power is introduced. The idea revolves around establishing a relatively high finesse absorption-cavity internal to the detector element. A theoretical analysis demonstrates this concept and provides some design guidelines. This concept offers many advantages, especially for low-background astronomy, and may prove to be technologically simpler to implement than other concepts such as the impurity-band-conduction approach.
Anomalous photoresponse of metal films
Authors: Johnson Mark , Beasley M. R. , Geballe T. H. , Greenfield S. R. , Stankus John J. , Fayer M. D.
Published: July 2002

Current biased samples are illuminated by short pulses of laser light and voltages are measured for a range of temperature 7 K<T<350 K. Classically, no response is expected for times greater than 10 ps after the pulse arrival. However, transient signals with temperature-independent decay times are observed in Ni and Nb samples, and a similar signal with diminished amplitude is observed in a Au sample.
Solid phase epitaxial growth of amorphized InP
Authors: Ridgway M. C. , Palmer G. R. , Elliman R. G. , Davies J. A. , Williams J. S.
Published: July 2002

Solid phase epitaxial growth of amorphized InP has been investigated at temperatures of 145–335 °C. The epitaxial recrystallization kinetics have been determined for both thermal and ion beam annealing using ion channeling and time-resolved reflectivity measurements and post-anneal, residual disorder has been characterized with transmission electron microscopy. The twin density and size distribution were significantly smaller for ion beam annealed samples, thus clearly demonstrating that ion beam annealing effectively suppresses the onset of highly defective (twinned) regrowth characteristic of thermal annealing. The substantially better crystalline quality of ion beam annealed samples contrasts with observations in GaAs where only a slight difference in post-anneal disorder was apparent for the two annealing regimes.
Lower temperature post-annealing of thin films of YBa2Cu3O7 at lower oxygen partial pressure
Authors: Mogro-Campero A. , Turner L. G.
Published: July 2002

Thin films of YBa2Cu3O7 formed by ambient temperature deposition and furnace post-annealing have been obtained at annealing temperatures around 750 °C and an oxygen partial pressure of 29 Pa. The zero resistance transition temperature of these smooth films on LaAlO3 was 89 K, and a critical current density in excess of 1 MA cm−2 at 77 K was found by transport measurements.
Double solid phase epitaxy of germanium-implanted silicon on sapphire
Authors: Peterström S.
Published: July 2002

The crystalline quality of 0.3-μm-thick silicon on sapphire structures has been improved by double solid phase epitaxy of germanium-implanted material. This regrowth technique increased the mobility with 70–100% in phosphorus- and boron-doped films, respectively. The depth distribution of germanium induced donors was measured by capacitance-voltage profiling on diodes made in preamorphized bulk silicon and the energy distribution in the band gap was investigated with deep level transient spectroscopy. It was shown that the main part of the germanium implantation induced defects could be removed by a high-temperature annealing treatment.
Dependence of polarization, gain, linewidth enhancement factor, and K factor on the sign of the strain of InGaAs/InP strained-layer multiquantum well lasers
Authors: Tiemeijer L. F. , Thijs P. J. A. , de Waard P. J. , Binsma J. J. M. , Dongen T. v.
Published: July 2002

The sign of the strain in a multiquantum well (MQW) active layer of an InGaAs/InP laser determines whether lasing occurs from the electron–heavy hole transition or from the electron-light hole transition. Lasing from the electron-light hole transition is reported to provide a much better performance than predicted by theory. It is concluded that this gives the best device performance, providing a higher differential gain, a lower threshold current, a record low linewidth enhancement factor of 1.5, and a K factor of 0.22 ns, potentially allowing a 3 dB modulation bandwidth of 40 GHz.
Microampere threshold current operation of GaAs and strained InGaAs quantum well lasers at low temperatures (5 K)
Authors: Eng L. E. , Sa’ar A. , Chen T. R. , Gravé I. , Kuze N. , Yariv A.
Published: July 2002

The operation of ultralow threshold current GaAs and InGaAs quantum well lasers at cryogenic temperatures has been studied. In particular the threshold current Ith and lasing wavelength of GaAs and strained InGaAs lasers have been measured as a function of temperature from 300 down to 5 K. Ith can in both lasers be characterized by a linear function of temperature up to 200 K, with a significantly (2.5×) larger dIth/dT for the GaAs laser. We measured a minimum threshold current of 120 μA for the GaAs laser and 165 μA for the InGaAs laser at 5 K. We derive a simple expression for the transparency carrier density as a function of temperature and effective masses to explain our results.
Luminescence characterization of CdTe:In grown by molecular beam epitaxy
Authors: Bassani F. , Tatarenko S. , Saminadayar K. , Bleuse J. , Magnea N. , Pautrat J. L.
Published: July 2002

We report on the incorporation of indium as a shallow donor in CdTe by molecular beam epitaxy. Using proper surface stoichiometry conditions, we demonstrate that it is possible to incorporate and activate up to 1018 cm−3 indium impurities. The doped layers have been characterized by secondary-ion mass spectroscopy, capacitance-voltage and Hall-effect measurements. Photoluminescence (PL) and resonant excitation of the PL clearly identify indium as the chemical dopant, acting as an effective mass donor with an energy of 14 meV. Incorrect stoichiometry conditions lead to a poor dopant activity and to complex centers formation.
Tunnel electron induced charge generation in very thin silicon oxide dielectrics
Authors: Farmer K. R. , Andersson M. O. , Engström O.
Published: July 2002

Positive and negative charging effects are described for small area (0.008–20 μm2), very thin dielectric (∼2.5 nm), metal-oxide-silicon diodes in which electrons can tunnel directly between the electrodes. These effects are similar to those seen in conventional, thicker oxide devices in which electrons are injected into the oxide conduction band. We show that at least in the thin oxides, charge generation is possible at a total electron energy level which is well below those suggested in a number of models for damage in the thicker oxides.
Optically detected microwave-induced impact ionization of ytterbium bound excitons in InP
Authors: Heijmink Liesert B. J. , Godlewski M. , Stapor A. , Gregorkiewicz T. , Ammerlaan C. A. J. , Weber J. , Moser M. , Scholz F.
Published: July 2002

Optically detected microwave-induced impact ionization of excitons and shallow donors is studied in Yb-doped InP grown by metalorganic chemical vapor deposition. The experimental results directly confirm that Yb3+ intrashell emission is induced by nonradiative recombination of Yb bound excitons due to an impurity Auger effect. Yb3+ ions in InP are found to bind excitons with the electron being localized first, followed by subsequent hole capture.
Interactive effects in the reactive ion etching of SiGe alloys
Authors: Oehrlein G. S. , Zhang Y. , Kroesen G. M. W. , de Frésart E. , Bestwick T. D.
Published: July 2002

Reactive ion etching (RIE) of epitaxial, strained Si1−xGex alloys, x≤0.20, in fluorine-, chlorine-, and bromine-based low-pressure plasmas has been investigated. The SiGe etch rates increase for each etchant with Ge concentration, e.g., for fluorine-based RIE (CF4 and SF6) the etch rate of a Si80Ge20 alloy is ≂2x that of elemental Si. Analysis shows that the etch rate increase is not accounted for by the greater rate of gasification of Ge atoms alone but that the presence of Ge atoms in the SiGe alloy increases the rate of Si etch product formation.
Formation of cobalt silicide in Co+ implanted Si(111)
Authors: Hsieh Yong-Fen , Hull Robert , White Alice E. , Short Ken T.
Published: July 2002

The microstructural variation of CoSi2 buried layers formed by 100 keV Co+ implantation at 350 °C into Si (111) is systematically studied. The critical dose dc of Co+ implantation at 100 keV required to form a continuous CoSi2 buried layer after annealing is the same in both Si (111) and (001), ≊1.1×1017 cm−2, corresponding to a threshold peak concentration of 18.5 at. % Co. In addition, we observe continuous buried layers consisting of both A-(fully aligned) and B-(twinned) CoSi2 grains in the (111) samples implanted at doses ≊ dc. The relative fractions of A and B are found to vary with the implanted doses, current densities of the ion beam, and annealing conditions with the B fractions varying from 0% to 100%. Continuous A-type layers are formed only in the samples implanted to doses ≥1.6×1017 cm−2.
Effect of beryllia substitution and addition in a YBa2Cu3O7−δ compound
Authors: Paulose K. V. , Koshy J. , Nair K. Ravindran , Damodaran A. D.
Published: July 2002

The effect of BeO substitution and addition in the superconducting properties of YBa2Cu3O7−δ superconductors has been investigated by temperature resistance measurements and x-ray diffraction studies. The results revealed that the substitution or addition of BeO in YBa2Cu3O7−δ does not have much detrimental effect on the superconducting properties. Because of this nonpoisoning behavior, beryllia is suggested as a suitable substrate material for the production of superconducting thin films.
Optical switching and optical logic in a thermally expanding Si étalon
Authors: Feng S. T. , Irene E. A.
Published: July 2002

Optical switching in a thermally expanding Si étalon has been demonstrated. In this experiment a pulsed CO2 laser beam is used to heat a Si étalon and shift the interference fringe of a 1.5 μm probe beam. It is shown that the switching time can be greatly reduced from ms to μs by choosing a probe beam of shorter wavelength in an external switching configuration. By aligning one étalon at switch-on and another at switch-off, we have demonstrated a write and erase logic system.
Optically induced absorption modulation in a periodically δ-doped InGaAs/GaAs multiple quantum well structure
Authors: Larsson A. , Maserjian J.
Published: July 2002

Strong optically induced absorption modulation has been achieved in a periodically δ-doped InGaAs/GaAs multiple quantum well structure. The use of δ-doping has enabled efficient modulation in short-period structures using a low-power semiconductor laser. With an excitation intensity of 100 mW/cm2 we have measured an absolute quantum well absorption change of more than 9000 cm−1 corresponding to a differential absorption change as high as 58% at the excitonic resonance.
Negative electron affinity (Si-Na2KSb-Cs)-O-Cs photocathode
Authors: Guo Tailiang , Gao Huairong
Published: July 2002

The work function of a silicon substrate will decrease rapidly and a negative electron affinity Si photocathode may be produced when a clean Si(100) substrate is activated by applying cesium and then oxygen, only once. But the work function of thus produced Si(100) photocathode would be increased and its integral photoemission sensitivity would be decreased if the cathode is subsequently treated with Cs and/or O2. In this letter, a new activation technology is adopted, and a reflection mode negative electron affinity (Si-Na2KSb-Cs)-O-Cs photocathode with maximum photoemission sensitivity S=2000 μA/lm is fabricated. The surface layer model and the energy-band structure of the photocathode are also discussed.
Novel reflectance modulator employing an InGaAs/AlGaAs strained-layer superlattice Fabry–Perot cavity with unstrained InGaAs/InAlAs mirrors
Authors: Fritz I. J. , Myers D. R. , Vawter G. A. , Brennan T. M. , Hammons B. E.
Published: July 2002

We present a novel approach to optoelectronic devices by combining mechanically stable strained and unstrained epitaxial multilayers. We illustrate our approach with an optical reflectance modulator based on an asymmetric Fabry–Perot resonator designed to operate near 1.06 μm. The resonator is grown on a mechanically relaxed buffer of In0.11Ga0.89As deposited on a GaAs substrate. For mirrors, quarter-wave stacks of In0.11Ga0.89As and In0.1Al0.9As, lattice matched to the buffer, are used. The Fabry–Perot cavity consists of an In0.23Ga0.77As/Al0.35Ga0.65As strained-layer superlattice whose planar lattice constant also matches the buffer. Our first device operates at 1.04–1.05 μm depending on lateral position across the wafer. The insertion loss at resonance is less than 2 db and a fractional modulation of over 60% has been achieved with a 4 V bias swing.
High-purity InP grown on Si by organometallic vapor phase epitaxy
Authors: Aina O. , Mattingly M. , Bates J. R. , Coggins A. , O’Connor J. , Shastry S. K. , Salerno J. P. , Davis A. , Lorenzo J. P. , Jones K. S.
Published: July 2002

We have grown by organometallic vapor phase epitaxy high-purity InP on Si substrates using a GaAs intermediate layer. The InP layers exhibit residual electron concentration as low as 5×1014 cm−3 and electron mobilities as high as 4000 and 25 000 cm2/V s at 300 and 77 K, respectively. The achieved InP quality is dependent on the GaAs intermediate layer thickness. These excellent electrical properties are due to high crystal qualities as evidenced by x-ray rocking curve half width as low as 215 arcsec and defect densities on the order 108 cm−2. p/n junctions, with ideality factors as low as 1.6 and low leakage currents, confirm the device quality of this material.
Chemically pumped atomic iodine pulse laser
Authors: Endo M. , Shiroki K. , Uchiyama T.
Published: July 2002

A pulsed iodine laser driven by a chemical oxygen generator was developed. The energy deposition on I(2P3/2) was made by a high-pressure pulsed O2(a1Δg) generator. Although this scheme is the same as the conventional chemically pumped oxygen-iodine laser (COIL), it is unique in that the pulsed laser was extracted by the high-energy density pulsed pumping scheme. The pulse energy obtained was 1.34 J, the pulse width was 1.5 ms, and the peak power was 900 W. The specific energy was estimated to be 3.6 J/ℓ.
Crystallinity of a-axis oriented YBa2Cu3O7−δ thin film epitaxially grown on NdGaO3 (110) by 95 MHz magnetron sputtering
Authors: Homma N. , Okayama S. , Takahashi H. , Yoshida I. , Morishita T. , Tanaka S. , Haga T. , Yamaya K.
Published: July 2002

An a-axis oriented 400 Å YBa2Cu3O7−δ film has been epitaxially deposited on a NdGaO3 (110) substrate by rf magnetron sputtering using a single YBa2Cu5Ox target. An excitation frequency of 94.92 MHz, seven times as high as the conventionally used 13.56 MHz, results in a lower self-bias voltage which reduces degradation of films caused by resputtering due to negatively charged oxygen. Sharp streaks corresponding to the c-axis lattice parameter of YBa2Cu3O7−δ have been observed by reflection high-energy electron diffraction, showing that the c-axis is parallel to the surface of the NdGaO3 substrate and the film surface is smooth on an atomic scale. The crystallinity has been characterized by Rutherford backscattering channeling analysis. A minimum yield, χmin of 3.2%, has confirmed excellent crystallinity of the a-axis oriented film.
Extremely-low-threshold and high-temperature operation in a photopumped ZnSe/ZnSSe blue laser
Authors: Nakanishi K. , Suemune I. , Fujii Y. , Kuroda Y. , Yamanishi M.
Published: July 2002

A ZnSe/ZnSSe blue semiconductor laser was demonstrated to show very low threshold by direct photopumping of the ZnSe active layer. The lowest threshold at the excitation wavelength of 445 nm was 10 kW/cm2 at 300 K which is equivalent to the current density of 3.6 kA/cm2. This is the lowest threshold ever reported in II-VI photopumped lasers and is approaching the theoretically calculated threshold. The characteristic temperature of the threshold, which characterizes the temperature dependence of the threshold in the exponential form, was 124 K up to the measured 400 K and was comparable to III-V double-heterostructure lasers. The differential quantum efficiency remained the similar level up to 400 K and its decrease observed at 400 K was within 23% of the efficiency at 300 K.
Ultrafast refractive index dynamics in AlGaAs diode laser amplifiers
Authors: Hultgren C. T. , Ippen E. P.
Published: July 2002

Ultrafast refractive index dynamics in AlGaAs diode laser amplifiers were studied using 440 fs optical pulses. Refractive index changes consistent with a free carrier heating model proposed to explain earlier studies of gain dynamics in diode lasers are exhibited. We also observe an apparently instantaneous refractive index change that corresponds to an n2⊥ of −5×10−12 cm2/W.
Measured pressure broadening and shift rates of the 1.73 μm (5d[3/2]1–6p[5/2]2) transition of xenon
Authors: Hebner G. A. , Hays G. N.
Published: July 2002

Pressure broadening and line center shift rates as a function of helium, neon, and argon pressure have been measured for the 1.73 μm (5d[3/2]1–6p[5/2]2) transition in xenon. The pressure broadening rates are 20.3±6.4, 12.7± 3.5, and 19.7±2.9 MHz/Torr for helium, neon, and argon buffers, respectively.
Si delta-doped field-effect transistors by atmospheric pressure metalorganic chemical vapor deposition
Authors: Pan N. , Carter J. , Jackson G. S. , Hendriks H. , Zheng X. L. , Kim M. H.
Published: July 2002

Si delta-doped GaAs field-effect transistors (FETs) are demonstrated by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) and characterized by Hall-effect, capacitance-voltage (C-V), and Shubnikov de-Haas measurements. The Si delta doping was accomplished by interrupting the growth and flowing silane with controlled timing under an arsenic overpressure. Devices with 0.5 μm gate length (Ns=2.2×1012 cm−2) were fabricated with a maximum extrinsic transconductance of 140 mS/mm and a current gain cutoff frequency of 17 GHz. The transconductance as a function of gate voltage showed a plateau region through a range of 1.5 V further supporting spatial confinement of the electrons.
Stability of a hedgehog nematic configuration in a small closed cylindrical cavity
Authors: Chen Shu-Hsia , Liang B. J.
Published: July 2002

This letter presents a study on the stability of molecular configurations in a small closed nematic liquid-crystal cell. A volume point defect exists at the center of the cell with the molecules anchored perpendicularly to the cavity wall. We show that the transformation of a radial hedgehog to a hyperbolic one should occur when the ratio of splay-to-bend elastic constants becomes larger than a certain value that depends on the cell geometry.
Substrate temperature measurement in a molecular beam epitaxy chamber using in situ GaAs photoluminescence monitoring
Authors: Sandroff C. J. , Turco-Sandroff F. S. , Florez L. T. , Harbison J. P.
Published: July 2002

We use GaAs photoluminescence (PL) obtained in situ in an epitaxial growth chamber to measure substrate temperatures from 25 to 450 °C with an accuracy of ±8 °C. Since temperature is obtained directly from the measured GaAs band gap, the approach is free of the problems associated with thermal contacts and emissivity calibration, which are encountered when using thermocouples and pyrometers. The PL technique can be used for any type of sample mounting, and since absolute temperature is measured, it is unnecessary to track the thermal history of the sample.
Comparative study of the properties of ultrathin Si3N4 films with Auger electron spectroscopy, spectroscopic ellipsometry, and Raman spectroscopy
Authors: Paloura E. C. , Logothetidis S. , Boultadakis S. , Ves S.
Published: July 2002

Ultrathin Si3N4 films are characterized with Auger electron spectroscopy, spectroscopic ellipsometry (SE), and Raman spectroscopy (RS). It is shown that Ar+ sputtering induces preferential nitrogen sputtering which causes problems in the determination of the interface location. Film thickness measurements with the nondestructive SE technique result in film thicknesses systematically larger than those calculated from the Auger sputter profiling, for films thinner than 100 Å. Furthermore, analysis of the SE and RS data shows that the films are dense and stoichiometric while the stress induced by the Si3N4 film on the Si substrate amounts to 2–3 kbar.
Thermal stability of dopant-hydrogen pairs in GaAs
Authors: Pearton S. J. , Abernathy C. R. , Lopata J.
Published: July 2002

The thermal stability of dopant-hydrogen complexes in hydrogenated n- and p-type GaAs(1–2×1017 cm−3) has been determined by examining their reactivation kinetics in reverse-biased Schottky diodes. The reactivation process is first-order for all of the dopants, with thermal dissociation energies (ED) of 1.45±0.10 eV for SiAs acceptors, 1.25±0.05 eV for SiGa donors, 1.20±0.10 eV for SnGa donors, 1.25±0.10 eV for Zn acceptors, 1.35±0.05 eV for CAs acceptors, and 1.15±0.10 eV for Be acceptors. The dissociation frequencies (ν) are thermally activated of the form νD = ν0E−ED/kT, with the ν0 values in the range 1–5×1013 s−1. The results are consistent with much of the H being present as H+ in p-type material, and H− in n-type material.
Fermi-level dependence of defect profiles in H+-bombarded silicon
Authors: Reisinger J. , Palmetshofer L.
Published: July 2002

Defect levels produced by low-dose H+ bombardment of silicon with different phosphorus doping and oxygen content were investigated using transient capacitance spectroscopy. For vacancy-related defects both the peak concentration and the half width of defect profiles depend only on the position of the Fermi energy. All defect profiles were found to be broader than the theoretical vacancy distribution. The broadening which increases with decreasing doping level is explained by a model based on electric-field-enhanced diffusion.
Possible observation of Pb0 and Pb1 centers at irradiated (100)Si/SiO2 interface from electrical measurements
Authors: Haneji Nobuo , Vishnubhotla Lakshmanna , Ma T. P.
Published: July 2002

By the use of ac conductance measurements, we have observed two distinct defects with different capture cross sections at the x-ray irradiated (100)Si/SiO2 interface. The capture cross section for one defect is a strong function of energy, while the other one is basically independent of energy. There is a strong possibility that these two interface defects correspond to the Pb0 and Pb1 centers seen in the electron spin resonance experiments. The fact that we do not observe the same behavior on (111) samples lends support to this hypothesis.
Dynamic thermal expansion under transient laser-pulse heating
Authors: Tang D. W. , Zhou B. L. , Cao H. , He G. H.
Published: July 2002

An infrared radiation pyrometer for transient temperature measurement and a photoelectric installation for micrometric length-change measurement were developed. After being heated by a CO2 laser pulse of 0.1 μs, the transient temperature-rise history and length change of thermal expansion of 20–50 μm Al films during tens of microseconds were recorded. Nonsynchronous change of temperature and thermal expansion under transient heating was observed.
YBa2Cu3O7−x-Y2O3 system and in situ deposition of trilayer heterostructures by coevaporation
Authors: Ying Q. Y. , Hilbert C. , Kumar N. , Eichman D. , Thompson M. , Kroger H. , Hwang D. M.
Published: July 2002

We have deposited YBa2Cu3O7−x-Y2O3-YBa2Cu3O7−x heterostuctures by an in situ electron-beam coevaporation technique. Physical and chemical properties of Y2O3 were studied. The deposition conditions for Y2O3 and YBa2Cu3O7−x are completely compatible. The crystal structure of Y2O3 provides a close lattice match with YBa2Cu3O7−x and allows oxygen diffusion through Y2O3, so that heteroepitaxy and the tetragonal-orthorhombic structural transformations of YBa2Cu3O7−x can be achieved. The heterostructures are therefore of high quality. Both the top and the bottom YBa2Cu3O7−x layers are superconducting above 85 K. Tunneling phenomena on junctions fabricated from these trilayers were observed.
Compositional disordering of strained InGaAs/GaAs quantum wells by Au implantation: Channeling effects
Authors: Jackman T. E. , Charbonneau S. , Allard L. B. , Williams R. L. , Templeton I. M. , Buchanan M. , Vos M. , Mitchell I. V. , Jackman J. A.
Published: July 2002

Compositional disordering of strained InGaAs quantum wells by the implantation of Au ions has been examined as a function of the incident implantation angle. Together, photoluminescence and secondary ion-mass spectrometry demonstrate that mixing at depths significantly greater than the mean-implantation range is due to the creation of point defects by ions which have channeled into the crystal. Compositional disordering effects due to the rapid thermal diffusion of Au ions was negligible.
Initial stages of sputtering on Au(111) as seen by scanning tunneling microscopy
Authors: Lang C. A. , Quate C. F. , Nogami J.
Published: July 2002

We have studied the evolution of the surface topography of neon-bombarded gold films, from the initial stages of sputter damage to the removal of several layers. Energy-dependent sputter yields and crater size distributions are derived from scanning tunneling microscope (STM) images which show the progressing surface erosion. A surprising duality in the behavior of surfaces prepared by deposition of atoms (growth) and ‘‘deposition of vacancies’’ (erosion) is revealed.
Thermal annealing of light−induced metastable defects in hydrogenated amorphous silicon nitride
Authors: Tober E. D. , Kanicki J. , Crowder M. S.
Published: July 2002

Exposure to ultraviolet light induces paramagnetic, metastable defects in hydrogenated amorphous silicon nitride (a-SiN1.6:H) thin films. The thermally induced decay of the light-induced paramagnetic defects follows a stretched exponential dependence on annealing time, exp [−(t/τ)β], and displays a temperature-dependent β and τ. These results indicate that a multiple trapping or a trap-controlled hopping mechanism is involved in the annealing process with an apparent activation energy of 0.43 eV.
Work hardening and strain relaxation in strained-layer buffers
Authors: Willis J. R. , Jain S. C. , Bullough R.
Published: July 2002

The driving force for the introduction of dislocations at the interface between a strained buffer layer and its substrate is considered. An exact assessment is made of the difference in energy between a system in which prestrain is partially relaxed by the presence of a periodic array of dislocations between layer and substrate and one containing a periodic array which is complete except for one vacant site. The difference provides an expression for the driving force, for introducing the ‘‘last’’ dislocation to complete the periodic array, by the motion of a threading dislocation. All of the dislocation stress fields are accounted for exactly. It emerges that, contrary to intuition, the fluctuating part of the dislocation stress field contributes a term which is attractive rather than repulsive, which is the opposite effect to that found in ‘‘Taylor hardening.’’
HgCdTe double heterostructure injection laser grown by molecular beam epitaxy
Authors: Zandian M. , Arias J. M. , Zucca R. , Gil R. V. , Shin S. H.
Published: July 2002

While a variety of light-detecting devices have been made with HgCdTe, little has been done to apply this technology to light-emitting devices. We report here the successful fabrication and operation of the first HgCdTe injection laser. This stripe-geometry double-heterostructure laser was operated under pulsed current at temperatures between 40 and 90 K. At 77 K, the emission wavelength was 2.86 μm with a linewidth of 0.3 meV, and the pulsed threshold current density was 625 A/cm2. The double heterostructure, with a 1.4-μm-thick active layer, was grown and in situ doped by molecular beam epitaxy (MBE). The p+ and n+ confinement layers were doped with arsenic and indium, respectively.
Transition from longitudinal-optical phonon scattering to surface-optical phonon scattering in polar semiconductor superlattices
Authors: Stroscio Michael A. , Iafrate Gerald J. , Kim K. W. , Littlejohn M. A. , Goronkin Herbert , Maracas George N.
Published: July 2002

Dielectric continuum models of optical-phonon modes predict an enhancement in the strength of the surface-optical (SO) modes in double-barrier heterostructures as the heterojunction-to-heterojunction separation is reduced. There is currently no consensus on the nature of the electron-SO-phonon coupling interaction. In this work, the ratio of electron scattering by the SO-phonon modes to that by the confined longitudinal-optical (LO) phonon modes is calculated for a GaAs/AlAs short-period superlattice based on the assumption that the electron-SO-phonon interaction may be described by a scalar potential. The scaling of the ratio of electron-SO-phonon scattering to electron-LO-phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar-potential model.
Influence of hydrogen passivation on the infrared spectra of Hg0.8Cd0.2Te
Authors: Chen Y. F. , Chen W. S.
Published: July 2002

Hydrogen passivation has been investigated in Hg0.8Cd0 2Te using infrared transmission measurements. The ability of atomic hydrogen to passivate the activities of residual impurities or defects is demonstrated by the fact that the absorption edge is moved to the short wave direction and the absorption below the energy gap is reduced after the incorporation of atomic hydrogen using an rf glow discharge system. It is also found that Hg vacancies can be effectively passivated after hydrogenation. Hydrogen injection and passivation of residual impurities or defects are also observed in Hg0.8Cd0.2Te boiled in water.
Subnanosecond photoresponse of a YBaCuO thin film to infrared and visible radiation by quasiparticle induced suppression of superconductivity
Authors: Semenov A. D. , Gol’tsman G. N. , Gogidze I. G. , Sergeev A. V. , Gershenzon E. M. , Lang P. T. , Renk K. F.
Published: July 2002

We observed subnanosecond photoresponse of a structured superconducting YBa2Cu3O7−δ thin film to infrared and visible radiation. We measured the voltage response of a current biased film (thickness 700 Å) in a resistive state to radiation pulses. From our results we conclude a response time of about 90 ps and a responsivity of about 4×1010 Ω/J. We attribute the response to Cooper pair breaking and suppression of the superconducting energy gap induced by nonequilibrium quasiparticles.
Blue/green pn junction electroluminescence from ZnSe-based multiple quantum-well structures
Authors: Xie W. , Grillo D. C. , Gunshor R. L. , Kobayashi M. , Hua G. C. , Otsuka N. , Jeon H. , Ding J. , Nurmikko A. V.
Published: July 2002

The successful p doping of ZnSe by substitutional nitrogen using a plasma cell incorporated into the molecular beam epitaxy chamber has led to the development of electroluminescent devices based on carrier injection at a pn junction. The light emitting diode structures described here are grown on a GaAs substrate using a tetragonally distorted (In,Ga)As buffer layer to provide lattice matching between the substrate and the active II–VI region. The result of the incorporation of the buffer layer is an essentially dislocation-free active region. The letter discusses optical properties as well as the x-ray and transmission electron microscopy characterization of the quantum well device structures.
MgO epitaxial thin films on (100) GaAs as a substrate for the growth of oriented PbTiO3
Authors: Hsu Wei-Yung , Raj Rishi
Published: July 2002

Epitaxial MgO thin films were grown on (100) GaAs substrates by reactive rf magnetron sputtering. Coupled x-ray diffraction, off-axis φ scan, and transmission electron microscopy indicated in-plane alignment of the MgO film with the GaAs substrate such that MgO[100]∥GaAs[100]. PbTiO3 ferroelectric thin films, grown on this MgO surface, were found to be oriented with PbTiO3{100}∥ MgO(001)∥ GaAs(001) and PbTiO3〈100〉∥ MgO[100]∥ GaAs[100].
Effect of hydrogen treatment on electrically active centers in AlGaAsSb
Authors: Polyakov A. Y. , Stam M. , Milnes A. G. , Bochkarev A. E. , Pearton S. J. , Wilson R. G. , Rai-Choudhury P. , Hillard R. J.
Published: July 2002

The effects of hydrogen treatment on the concentration of donors and acceptors in Al0.5Ga0.5As0.05Sb0.95 are studied by capacitance-voltage measurements, two probe spreading resistance profiling, and secondary ion mass spectrometry (SIMS). Strong passivation of both donors and acceptors was observed. SIMS measurements of deuterium profiles in both and that of the donors or acceptors. This behavior is closer to that of the AlxGa1−xAs system than to that of GaSb.
Hydrogen passivation of interface defects in GaAs/AlAs short-period superlattices
Authors: Fischer R. , Peter G. , Göbel E. O. , Capizzi M. , Frova A. , Fischer A. , Ploog K.
Published: July 2002

We have observed an increase of overall luminescence intensity and carrier lifetimes of GaAs/AlAs short-period superlattices after exposure of the samples to low-energy hydrogen ion-gun irradiation. We conclude from our data that interface defects which may become important as nonradiative recombination centers in short-period superlattices with only a few monolayers period can be passivated by hydrogen.
Observation of phase conjugation at 10.6 μm via intersubband third-order nonlinearities in a GaAs/AlGaAs multi-quantum-well structure
Authors: Gravé Ilan , Segev Mordechai , Yariv Amnon
Published: July 2002

We describe the observation of phase conjugation at 10.6 μm in a GaAs/AlGaAs multi-quantum-well-doped structure. The responsible nonlinear susceptibility χ(3) is due to a nearly resonant intersubband transition. The magnitude of χ(3) is 7×10−5 esu and the phase conjugate reflectivity is a few tenths of a percent.
Passivation of (111) Si/SiO2 interface by fluorine
Authors: Wang X. W. , Ma T. P.
Published: July 2002

High quality Si/SiO2 interface and improved oxide reliability have been achieved on (111) Si substrate by introducing NF3 into the oxidation furnace. The interface properties and the radiation hardness of the fluorinated (111) metal oxide semiconductor capacitors have been studied as a function of the amount of NF3 introduced.
Photoluminescence study of interdiffusion in In0.53Ga0.47As/InP surface quantum wells
Authors: Oshinowo J. , Forchel A. , Grützmacher D. , Stollenwerk M. , Heuken M. , Heime K.
Published: July 2002

We have investigated the thermal stability and interdiffusion of In0.53Ga0.47As/InP surface quantum wells. In these structures the optically active InGaAs layer is bounded on one side by vacuum and on the other side by InP. We obtain well-defined photoluminescence emission spectra with high intensity. After rapid thermal annealing at temperatures between 500 and 900 °C (annealing time 1 min) we observe strong emission energy shifts of up to 316 meV. By using a simple model of ion intermixing we estimate large interdiffusion coefficients (e.g., 1.7×10−14 cm2 s−1 for T=900 °C) and an activation energy of 1.3 eV for the surface quantum wells.
Raman spectroscopic assessment of carbon-hydrogen pairs in carbon-doped GaAs layers
Authors: Wagner J. , Maier M. , Lauterbach Th. , Bachem K. H. , Ashwin M. , Newman R. C. , Woodhouse K. , Nicklin R. , Bradley R. R.
Published: July 2002

Raman scattering by local vibrational modes of carbon-hydrogen pairs is reported for heavily carbon-doped epitaxial GaAs layers. Scattering by the longitudinal carbon mode of these pairs at 452 cm−1 shows a strong resonant enhancement for incident photon energies approaching the E1 band-gap energy of GaAs (≂3 eV). A possible mechanism for this resonance behavior is discussed in terms of the displacement of the carbon atom from its normal arsenic lattice site accompanied by a lengthening and weakening of the carbon-gallium bonds when carbon-hydrogen pairs form. The present findings demonstrate that resonant Raman scattering is an attractive tool for the detection of carbon-hydrogen pair formation in thin carbon-doped epitaxial GaAs layers grown from source materials containing hydrogen. The detection limit is estimated to be in the low 1018 cm−3 range.
Enhancement of change in the absorption coefficient in an asymmetric quantum well
Authors: Susa Nobuhiko , Nakahara Tatsushi
Published: July 2002

We propose a three-step asymmetric quantum well to enhance change in the absorption coefficient by applying electric field. Oscillator strength for the n=1 heavy hole exciton is reduced at zero bias and increased at bias voltage. This three-step structure has the advantages of a large change in absorption, low transmission loss, and low operating voltage in absorption-type optical modulators utilizing the quantum confined Stark effect.