bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface reactions of silane with oxidized InP and their application to the improvement of chemical vapor deposition grown, InP-based metal-insulator-semiconductor devices
Authors: Licoppe C. , Moison J. M. , Nissim Y. I. , Regolini J. L. , Bensahel D.
Published: July 2002

The first stage of chemical vapor deposition of SiO2 from SiH4 and O2 on InP has been investigated. SiH4 is shown to interact only with an oxidized InP surface. It plays the part of an interface deoxidizing agent, restoring the covalent bonding of surface InP atoms. Oxygen originally bonded to InP becomes bonded to the silicon deposit in silica-like bonds. This phenomenon has been used as an in situ surface cleaning step in the processing of metal-insulator-semiconductor InP structures. It leads to a strong decrease of the hysteresis in capacitance-voltage curves, demonstrating improvement of the interface properties.
Temperature and field dependence of the critical current densities of Y-Ba-Cu-O films
Authors: Allen L. H. , Broussard P. R. , Claassen J. H. , Wolf S. A.
Published: July 2002

We have prepared thin films of Y1Ba2Cu3O7−x using a coevaporation technique and measured their critical current densities as a function of both temperature and field using a transport technique. For a stoichiometric composition we find that Jc at 4.2 K in zero field is 1.04×106 A/cm2 and does not drop below 105 A/cm2 until T>60 K. Fitting the data near Tc shows that Jc follows a power law of (1−t), with t being the reduced temperature. In an applied field perpendicular to the film’s surface, Jc also drops slowly, and up to 90 kOe Jc>105 A/cm2 for T=4.2 K. Measurements for an off-stoichiometric film, Y1Ba3Cu2O7−x, give lower Jc values that fall off faster in temperature than for stoichiometric compositions.
Pulsed-ultraviolet laser Raman diagnostics of plasma processing discharges
Authors: Hargis P. J. , Greenberg K. E.
Published: July 2002

Spontaneous Raman spectroscopy with pulsed-ultraviolet laser excitation of the Stokes vibrational Raman lines was used to measure the percent dissociation of nitrogen and sulfur hexafluoride in low-pressure radio refrequency discharges of the type used for processing semiconductor materials. Measurements of the percent dissociation of sulfur hexafluoride, at pressures between 200 and 600 mTorr, show a strong pressure dependence which is consistent with recombination playing an important role in sulfur hexafluoride discharge kinetics.
Thickness and annealing dependence of the superconducting transition temperature of YBa2Cu3O7−x thin films on oxidized silicon and polycrystalline alumina substrates
Authors: Mogro-Campero A. , Turner L. G. , Kendall G.
Published: July 2002

Superconducting thin films of YBa2Cu3O7−x in the thickness range of 0.2–0.9 μm were tested in this study. A zirconia buffer layer was used to minimize interdiffusion on oxidized silicon and polycrystalline alumina substrates. The highest zero resistance transition temperatures (85 K for oxidized silicon and 86 K for polycrystalline alumina) were obtained for the thicker films; these are the highest values reported for thin films of this superconductor on these substrates. The thickness and annealing dependence of the transition temperature suggests that interdiffusion limits the performance of the thinner samples.
Electrochemical method of determination of the valence states of copper in YBaCuO compounds
Authors: Salkalachen S. , Salkalachen E. , John P. K. , Froelich H. R.
Published: July 2002

We describe an electrochemical technique to measure the oxidation states of copper in thin-film YBaCuO compounds. Quantitative information is obtained on Cu+ and Cu++ species.
Ionic species responsible for the plasma anodization of silicon
Authors: Barlow K. J. , Kiermasz A. , Eccleston W. , Moruzzi J. L.
Published: July 2002

Identification of the species that promotes the growth of silicon dioxide on silicon in a microwave oxygen plasma has been investigated. Comparison of ion analysis experiments using quadropole mass spectrometry and oxide growth experiments performed in the same system indicates a strong correlation between the oxide growth and the presence of O− ions in the plasma.
Schottky diode and field-effect transistor on InP
Authors: Loualiche S. , Ginoudi A. , L’Haridon H. , Salvi M. , Le Corre A. , Lecrosnier D. , Favennec P. N.
Published: July 2002

Schottky diode has been realized on InP by a special dry surface treatment. The diode reaches a breakdown voltage of 60 V and the reverse current remains at 0.6 μA under 30 V reverse voltage. The best device shows a reverse current of 0.2 nA at 1 V voltage with an ideality factor of 1.54. The Schottky has been used as a gate in the fabrication of field-effect transistors (FETs) on InP by ion implantation and chemical beam epitaxy. The ion-implanted FET with a channel concentration of 2×1017 cm−3 shows a transconductance of 107 mS/mm at room temperature for a 3 μm gate length.
Self-limiting deposition of Ga on a GaAs surface by thermal decomposition of diethylgalliumchloride observed by x-ray photoelectron spectroscopy
Authors: Ohno H. , Ishii H. , Matsuzaki K. , Hasegawa H.
Published: July 2002

Clean surfaces of molecular beam epitaxially grown GaAs were exposed to diethylgalliumchloride (DEGaCl) and the resultant change was observed by in situ x-ray photoelectron spectroscopy. At a substrate temperature of 300 °C, a self-limiting reaction between DEGaCl and the surface resulted in one monolayer of Ga deposition which is believed to lead to atomic layer epitaxy of GaAs using DEGaCl. No appreciable increase of Cl or C was observed after exposure. Discussion on the mechanism of the self-limiting reaction is also presented.
Temperature dependence of local vibrational mode optical absorption for carbon acceptors in GaAs
Authors: Sargent L. , Blakemore J. S.
Published: July 2002

The local vibrational mode (LVM) absorption band due to CAs in GaAs is reported for three semi-insulating samples at room temperature and for T<77 K. Data obtained by Fourier transform infrared spectroscopy at resolution values from 1.0 to 0.1 cm−1 indicate that the area of the carbon LVM band increases by ∼60% upon cooling from room temperature, a substantially larger increase than some accounts have suggested. Our recommended value for the calibration factor f in going from LVM band area to carbon concentration is fRT≂1.6fLT ≂(13±3)×1015 cm−1.
InGaAs-GaAs strained-layer quantum well buried heterostructure lasers (λ>1 μm) by metalorganic chemical vapor deposition
Authors: York P. K. , Beernink K. J. , Fernández G. E. , Coleman J. J.
Published: July 2002

Data are presented on long-wavelength (λ>1 μm) strained-layer InGaAs-GaAs quantum well buried heterostructure lasers grown by a two-step metalorganic chemical vapor deposition (MOCVD) process. Wet chemical etched mesas with an active region width of 3.5 μm are formed in a step-graded InGaAs-GaAs quantum well structure using an oxide mask. Selective MOCVD regrowth is used to form the buried heterostructure. Data are presented for devices having output powers of greater than 130 mW/facet, pulsed threshold currents of less than 7 mA, and internal quantum efficiencies of greater than 60%, for an emission wavelength of 1.074 μm. The near-field patterns indicate stable index-guided fundamental mode operation to greater than 30Ith.
Optical investigation of atomic steps in ultrathin InGaAs/InP quantum wells grown by vapor levitation epitaxy
Authors: Morais P. C. , Cox H. M. , Bastos P. L. , Hwang D. M. , Worlock J. M. , Yablonovitch E. , Nahory R. E.
Published: July 2002

Ultrathin InGaAs/InP single quantum well structures, grown by chloride transport vapor levitation epitaxy, have been investigated by low-temperature photoluminescence (PL). Well-resolved multiple peaks are observed in the PL spectra, instead of an expected single peak. We attribute this to monolayer (a0/2=2.93 Å) variations in quantum well (QW) thickness. Separate peak positions for QW thicknesses corresponding to 2–6 monolayers have been determined, providing an unambiguous thickness calibration for spectral shifts due to quantum confinement. The PL peak corresponding to two monolayers occurs at 1.314 eV, corresponding to an energy shift of 524 meV. Experimental data agree very well with a simple effective mass theory.
Carbon as a barrier for the outdiffusion of Cu
Authors: Chang Chin-An , Yee D. S. , Petkie R.
Published: July 2002

The effectiveness of carbon as a barrier for the outdiffusion of Cu is studied using C/Cu/substrate and Au/C/Cu/substrate structures. For the C/Cu structure deposited on SiO2 -coated Si with a 700 Å C layer, heating to 700 °C for 72 h and 750 °C for 6 h shows no outdiffusion of Cu to the carbon surface in N2 -H2. Only reaction between Cu and the SiO2 layer underneath is observed. Application of the carbon barrier between Cu and Au in the Au/C/Cu/substrate structure shows that the dilution of the Au layer due to the Cu outdiffusion is similar to but less than that of the Au/Ni/Cu/substrate structure using Ni as a barrier. The stability of the Au/C/Cu/substrate structure is enhanced relative to that of the Au/Ni/Cu/substrate one by more than 150 °C. Both the advantage and concerns using carbon as barriers for the interconnect and contact metallurgies are discussed.
Desorption of triethylgallium during metalorganic molecular beam epitaxial growth of GaAs
Authors: Uneta M. , Watanabe Y. , Ohmachi Y.
Published: July 2002

The desorption of triethylgallium (TEGa) adsorbed on As- and Ga-terminated surfaces during metalorganic molecular beam epitaxial (MOMBE) growth of GaAs is investigated by measuring the As flux dependence of the growth rate. The growth rate decreases with decreasing As flux in the substrate temperature range where the desorption of triethylgallium adsorbed on the growth surface occurs. This indicates that adsorbed TEGa (adTEGa) molecules desorb more rapidly on the Ga-terminated surface than on the As-terminated surface. To investigate the adTEGa desorptions on As- and Ga-terminated surfaces independently, the growth rates in alternating TEGa-As4 supply mode are compared with those in simultaneous supply mode. The growth rates in the alternating supply mode become smaller than those in the simultaneous supply mode as the substrate temperature is raised above 500 °C. This result demonstrates that the adTEGa desorption rate on the Ga-terminated surface is larger than that on the As-terminated surface.
Temperature dependence of the photoinduced EL2*→EL20 recovery process observed by infrared absorption
Authors: Fischer D. W. , Manasreh M. O.
Published: July 2002

The infrared absorption technique is used to measure the photoinduced recovery of the EL2 defect from its metastable state (EL2*) to its normal state (EL20) in semi-insulating GaAs. This recovery is induced by irradiating photoquenched samples with 0.90 or 1.46 eV light for 60 min at various temperatures between 10 and 110 K. The recovery process is found to be highly temperature and sample dependent. It is concluded that the results are related to the presence of other defects and impurities (traps) which interact with EL2 at low temperatures.
Monolithic integrated InGaAsP/InP distributed feedback laser with Y-branching waveguide and a monitoring photodetector grown by metalorganic chemical vapor deposition
Authors: Liou K.-Y. , Koren U. , Chandrasekhar S. , Koch T. L. , Shahar A. , Burrus C. A. , Gnall R. P.
Published: July 2002

We have fabricated an integrated 1.5 μm distributed feedback laser (DFB) with a Y-branching waveguide and a monitoring photodetector, grown entirely by metalorganic chemical vapor deposition. The integrated device is designed to resolve the frontface-backface mistracking problem of the DFB laser and to demonstrate monolithic integration of fundamental building blocks for photonic integrated circuits.
Electro-optic voltage profiling of modulation-doped GaAs/AlGaAs heterostructures
Authors: Hendriks P. , Schnitzeler F. J. M. , Haverkort J. E. M. , Wolter J. H. , de Kort Kees , Weimann G.
Published: July 2002

The electro-optic effect of GaAs is applied to profile the voltage distribution of the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. In our setup we reached a voltage sensitivity of 2 mV. We used this technique to characterize the local resistivity of the 2DEG. The results are consistent with those obtained from scanning electron microscopy voltage contrast measurements.
Double-crystal x-ray diffraction from Si1−xGex/Si superlattices: Quantification of peak broadening effects
Authors: Barnett S. J. , Brown G. T. , Houghton D. C. , Baribeau J.-M.
Published: July 2002

Double-crystal x-ray diffraction has been successfully used to study dimensional and compositional variations in Si1−x Gex /Si superlattices. For most samples studied an adequate agreement between theoretical and experimental diffraction profiles is obtained by using a theoretical model (kinematical) which assumes uniform superlattices with abrupt interfaces. In some samples, however, the superlattice-related diffraction peaks reveal an asymmetric broadening which is shown by comparison with dynamical diffraction simulations to be due to a grading in layer compositions and thicknesses throughout the superlattice stack. Detailed analysis of the diffraction data identified a gradual drift of 1.25% in the Ge flux during molecular beam epitaxy (MBE) growth. The MBE system parameters were modified to compensate for this effect and allow the growth of more structurally perfect strained-layer superlattices.
Diode laser pumped blue-light source at 473 nm using intracavity frequency doubling of a 946 nm Nd:YAG laser
Authors: Risk W. P. , Pon R. , Lenth W.
Published: July 2002

Using intracavity frequency doubling of a diode laser pumped 946 nm Nd:YAG laser, 3.1 mW of blue output power at 473 nm was obtained. Angle-tuned, type-I frequency doubling in potassium niobate was employed, and both the KNbO3 and Nd:YAG crystals were used at room temperature.
Improvement of the photoelectric properties of amorphous SiCx:H by using disilylmethane as a feeding gas
Authors: Beyer W. , Hager R. , Schmidbaur H. , Winterling G.
Published: July 2002

Amorphous (a-) SiCx:H films were deposited in a rf glow discharge of disilylmethane/silane mixtures. At optical gaps larger than 2 eV these films are found to have a higher photoconductivity than films prepared in conventional CH4/SiH4 gas mixtures. Both types of films are compared with respect to their hydrogen content as well as infrared and effusion spectra.
Reactive evaporation of titanium oxide films with controlled Ti/O ratio
Authors: Nozoye H. , Nishimiya N. , Sato H.
Published: July 2002

Oxidation state selected titanium oxide thin films (TinO2n−1; n=1–∞) were deposited by a combination of a pulsed molecular beam source and an electron beam metal source. The oxidation state of titanium was controlled solely by the number of gas pulses and the temperature of a substrate. The conditions for depositing crystalline TinO2n−1 thin films were determined.
Polyiodide-treated n-WSe2/Au Schottky junctions
Authors: Hodes Gary
Published: July 2002

Au/n-WSe2 Schottky junctions usually exhibit linear dark current-voltage characteristics, apparently dominated by structural defects, and low open circuit photovoltages. After treatment of the WSe2 with polyiodide in a liquid junction configuration and subsequent deposition of Au, good diode characteristics and high Voc are obtained which are similar to those exhibited by WSe2/polyiodide liquid junctions. The role of the polyiodide treatment is ascribed to defect passivation. The barrier height of the WSe2/Au junction (∼1.0 eV) is particularly high for a semiconductor of Eg=1.2 eV and supports recent work which claims that MoS2 (similar structure to WSe2) forms Schottky junctions which behave close to the Schottky limit.
Rechargeable E′ centers in sputter-deposited silicon dioxide films
Authors: Zvanut M. E. , Feigl F. J. , Fowler W. B. , Rudra J. K. , Caplan P. J. , Poindexter E. H. , Zook J. D.
Published: July 2002

An electron trapping instability in silicon dioxide films sputtered onto silicon substrates was analyzed by metal-oxide-semiconductor electrical methods and electron paramagnetic resonance (EPR), and was compared with an E′ defect model from molecular orbital cluster calculations. This comparison indicates that an E′ defect may well be responsible for the observed trapping instability, since electrically measured trap filling and emptying was quantitatively correlated with a reversible variation in the EPR signal magnitude. The specific model proposed for this defect is a ‘‘surface-like’’ or hemi-E′ center, O3≡Si−, which upon loss of an electron becomes O3≡Si+ and relaxes towards a planar configuration. The relaxation energy associated with the restoration of the original configuration is manifested as a hysteresis in the electrical trap filling and emptying cycle.
Organometallic chemical vapor deposition routes to high T
c superconducting Tl-Ba-Ca-Cu-O films
Authors: Richeson Darrin S. , Tonge Lauren M. , Zhao Jing , Zhang Jiming , Marcy Henry O. , Marks Tobin J. , Wessels Bruce W. , Kannewurf Carl R.
Published: July 2002

Films of the Tl-Ba-Ca-Cu-O high Tc superconductor can be prepared by either of two organometallic chemical vapor deposition routes. Ba-Ca-Cu-O films are first prepared on yttria-stabilized zirconia using the volatile precursors Ba(heptafluorodimethyloctanedionate)2, Ca(dipivaloylmethanate)2, and Cu(acetylacetonate)2. Deposition is carried out at 5 Torr pressure with argon as the carrier gas and water vapor as the reactant gas. Thallium is next incorporated in these films either by vapor diffusion using bulk Tl-Ba-Ca-Cu-O as the source, or by organometallic chemical vapor deposition using Tl(cyclopentadienide) as the source. The latter deposition is carried out at atmospheric pressure with an argon carrier and water-saturated oxygen reactant, followed by rapid thermal annealing. Both types of films consist primarily of the TlBa2Ca2Cu3Ox phase, have preferential orientation of the CuO planes parallel to the substrate surface, and exhibit onset of superconductivity at ∼120 K with zero resistance by 100 K.
Magnetic anisotropy of Nd15Fe77B8 flakes made by twin-roller quenching
Authors: Kuji Toshiro , O’Handley R. C. , Grant N. J.
Published: July 2002

Rapid solidification by twin-roller quenching of iron-neodymium-boron alloys produces flakes which show a strong (00l) texture normal to their surface by x-ray diffraction. The strong crystal orientation is argued to be due to both directional solidification in a thermal gradient and uniaxial deformation of the solid phase in the twin rollers. Magnetization studies on individual flakes show intrinsic coercivities of 14 kOe and a nearly 50% higher remanance for field normal to the flake surface (Br =9.5 kG) than in the flake plane (Br =6.5 kG). The perpendicular (BH)max is 16 MG Oe.
Bias-controlled intersubband wavelength switching in a GaAs/AlGaAs quantum well laser
Authors: Berthold K. , Levi A. F. J. , Pearton S. J. , Malik R. J. , Jan W. Y. , Cunningham J. E.
Published: July 2002

The light emission characteristic of a GaAs/AlGaAs single quantum well laser with an intracavity monolithic loss modulator has been investigated. Discrete, widely separated, wavelength switching from the first (875 nm) to the second (842 nm) subband is achieved by changing the applied modulator bias. In addition, we show that 2 mW of lasing light power may be modulated with a change in current of 250 μA and a voltage change of 1 V.
Lateral refractive index step in GaAs/AlGaAs multiple quantum well waveguides fabricated by impurity-induced disordering
Authors: Wolf T. , Shieh C.-L. , Engelmann R. , Alavi K. , Mantz J.
Published: July 2002

The lateral refractive index step Δn in GaAs/AlGaAs multiple quantum well waveguides fabricated by impurity-induced disordering is determined. Δn is found to depend on polarization and wavelength, increasing towards the active-layer band gap. The lateral index step can be as large as 4×10−2 for a Zn disordered waveguide device at 875 nm. A strong birefringence of the waveguiding characteristics is observed leading to an antiguiding behavior of TM-polarized light for wavelengths sufficiently below the band gap.
Surface resistance of YBa2Cu3O7 films on SrTiO3 and LaGaO3 substrates
Authors: Cooke D. W. , Gray E. R. , Houlton R. J. , Rusnak B. , Meyer E. A. , Beery J. G. , Brown D. R. , Garzon F. H. , Raistrick I. D. , Rollet A. D. , Bolmaro R.
Published: July 2002

Surface resistance measurements of films of YBa2Cu3O7 deposited onto single-crystal substrates of LaGaO3 and SrTiO3 have been made at a frequency of 22 GHz. The measurements were made in either a copper or niobium cavity by replacing the end wall with the superconducting film. Typical surface resistance at 20 K are 1–2 mΩ for films on LaGaO3 and 6–8 mΩ for films on SrTiO3, as measured in the copper cavity. The LaGaO3 values lie within the sensitivity range of the Cu cavity (∼2 mΩ) and can only be considered upper limits. Similar measurements in a Nb superconducting cavity resulted in a surface resistance value of 0.2±0.1 mΩ at 4 K for the best LaGaO3-based film. This value is more than an order of magnitude lower than Cu, and suggests that LaGaO3-based films may offer immediate advantages in a number of applications.
X-ray rocking curves from (100) and (111) CdTe grown on (100) GaAs by hot wall epitaxy
Authors: Lischka K. , Fantner E. J. , Ryan T. W. , Sitter H.
Published: July 2002

X-ray rocking curves of (100) and (111) oriented CdTe epilayers grown by hot wall epitaxy on (100) GaAs substrates have been measured. Our results indicate that the number of extended defects increases with thickness in (111) CdTe epilayers but decreases with thickness in (100) CdTe epilayers. The distortion of the GaAs surface induced by the CdTe epilayer is determined from comparative measurements of the rocking curve of the covered and uncovered GaAs substrate.
High-power fundamental mode AlGaAs quantum well channeled substrate laser grown by molecular beam epitaxy
Authors: Jaeckel H. , Meier H. P. , Bona G. L. , Walter W. , Webb D. J. , Van Gieson E.
Published: July 2002

We demonstrate a high-power AlGaAs single quantum well graded-index separate confinement heterojunction laser grown by molecular epitaxy over channeled substrates. Fundamental mode operation up to 130 mW for reflection modified devices has been achieved at a high differential quantum front-facet efficiency of 81%. This device structure allows extremely low threshold currents to 6 mA for power lasers due to the incorporation of lateral current blocking pn junction by crystallographic plane-dependent doping of amphoteric dopants. We obtained a very high-power continuous-wave fundamental mode operation of this type of laser at extremely low threshold currents and very high overall efficiency of more than 50%. This laser shows considerable potential for applications in optical storage and printer technology.
Silicon selective epitaxial growth at 800 °C using SiH4/H2 assisted by H2/Ar plasma sputter
Authors: Yew Tri-Rung , Reif Rafael
Published: July 2002

This letter presents the results of silicon selective epitaxial growth at 800 °C by ultralow pressure chemical vapor deposition using SiH4 /H2 assisted by H2 /Ar plasma sputter. By utilizing growth-sputter cycles, selective epitaxial layers can be grown on exposed silicon windows of silicon wafers with oxide patterns to the thickness needed. The growth process was carried out by flowing SiH4 (3.5 mTorr)/H2 (7 mTorr), while the sputter step was performed by using H2 (7 mTorr)/Ar(1.5 mTorr) plasma at a susceptor dc bias from −100 to −300 V. Characterized by cross-sectional transmission electron microscopy, Nomarski optical microscopy, and spreading resistance profiling, the epitaxial films were found of high structural and electrical quality.
Passivation of acceptors in InP resulting from CH4/H2 reactive ion etching
Authors: Hayes T. R. , Dautremont-Smith W. C. , Luftman H. S. , Lee J. W.
Published: July 2002

Reactive ion etching of InP with CH4/H2 mixtures leads to hydrogen passivation of near-surface Zn acceptors but not S donors. Secondary-ion mass spectrometry (SIMS) measurements of CH4/D2 etched samples show deuterium diffuses to a depth of 2000 Å in p-InP (1.5×1018 cm−3) when etching at a rate of 520 Å/min and a temperature of about 80 °C. Acceptor passivation occurs to the same depth. For n-InP, no donor passivation is observed, even though SIMS shows deuterium diffusion to a depth of 7000 Å. Annealing at 350 °C for 1 min restores carrier concentrations to near pre-etched levels.
Aluminum selective area deposition on Si using diethylaluminumchloride
Authors: Sasaoka C. , Mori K. , Kato Y. , Usui A.
Published: July 2002

Aluminum deposition on Si was studied using diethylaluminumchloride (DEAlCl) as a new Al chemical vapor deposition source. Selective area deposition was successfully achieved at substrate temperatures of 313–380 °C. The deposition rate was higher than 370 Å/min. Reflectance and resistivity of the deposited films were comparable to those of the evaporated ones. Decomposition experiments suggest that DEAlCl catalytically decomposes on the Al surface, which would explain the high selectivity observed.
Direct observation of discrete layers of dislocation loops near the projected ion ranges in high-dose P+-implanted (001)Si by cross-sectional transmission electron microscopy
Authors: Hsu S. N. , Chen L. J. , Chao W. Y.
Published: July 2002

The formation of discrete layers of dislocation loops near the projected ion ranges (Rp loops) of 65–80 keV, high-dose (5×1015–2×1016/cm2) P+-implanted (001)Si was observed by cross-sectional transmission electron microscopy (XTEM). Both the energy and dose dependence of the annealing behaviors of Rp loops provided strong evidences that they are related to P clustering. The inactivation of dopants due to precipitation, hence the appearance of Rp loops, is correlated to the sheet resistance data. The retardation of the solid phase epitaxial growth was shown to be related to the formation of Rp loops. Using Rp loops as an indicator of changes in point-defect distribution, a combined XTEM and plan-view TEM study was found to be most appropriate for the study of the precipitation process in high-dose P+-implanted silicon.
Defect-induced Schottky barrier height modification by pulsed laser melting of GaAs
Authors: Zhang T. , Sigmon T. W. , Weiner K. H. , Carey P. G.
Published: July 2002

A pulsed XeCl excimer laser (λ=308 nm) is used to melt n- and p-type GaAs samples. Melt-induced defects shift the surface Fermi level to a new pinning position at 0.58±0.04 eV below the conduction-band minimum for both n- and p-type samples. The Schottky barrier height of Au, deposited on the GaAs after laser irradiation, is increased by 0.38 eV (from 0.43 to 0.81 eV) for p-type, and decreased by 0.30 eV (from 0.84 to 0.54 eV) for n-type samples. In the post-melted GaAs near-surface region, four deep levels are found using deep level transient spectroscopy. The observation of minority-carrier traps in the Schottky diode structures suggests the existence of minority-carrier source. We speculate a compensated region forms near the GaAs surface. A bulk Fermi level stabilization model is used to explain the changes observed in the Schottky barrier heights.
Optically pumped laser oscillation at ≊2.9 μm of a HgCdTe layer grown by metalorganic chemical vapor deposition
Authors: Ravid A. , Zussman A. , Cinader G. , Oron A.
Published: July 2002

Photopumped pulsed stimulated emission at 2.9 μm in a HgCdTe layer grown by metalorganic chemical vapor deposition on a CdTe substrate was studied as a function of temperature. The threshold power of the HgCdTe laser (photoexcited by a GaAs diode laser) increased from 0.04 W at 12 K to 1.58 W at 150 K. Above 50 K, the temperature dependence of the threshold is exponential, yielding a T0 of 31 K. From the observed laser emission wavelength a Cd mole fraction of x=0.422 was determined. The far-field angular full width at e−2 of peak intensity was 5.5° and 9.5° perpendicular and parallel to the film plane, respectively.
Model for diffusion and trapping of hydrogen in crystalline silicon
Authors: Kalejs J. P. , Rajendran S.
Published: July 2002

A simplified analysis is presented to describe diffusion and trapping of atomic hydrogen in crystalline silicon. Predictions of the rate of advancement of the trapped hydrogen front as a function of process and material variables are obtained from a numerical solution of the transport equations. We demonstrate that the solutions are compatible with data on boron passivation at 150 °C only when the diffusivities obtained by extrapolation from the high-temperature results of Van Wieringen and Warmoltz [Physica 22, 849 (1956)] are used to represent atomic hydrogen diffusion in the absence of trapping.
Enhanced magneto-optic Kerr effects in thin magnetic/metallic layered structures
Authors: McGahan William A. , Chen Liang-Yao , Shan Z. S. , Sellmyer D. J. , Woollam John A.
Published: July 2002

Enhanced Kerr rotation spectra are measured in thin magnetic layers on silver. Also, variable angle of incidence spectroscopic ellipsometry is employed to measure the optical dielectric function of both the thin magnetic layer and the underlying thick silver layer. These results are explained quantitatively using the electromagnetic theory for reflection of light from multiple layers of isotropic and gyrotropic materials.
Photothermal deflection spectroscopy of heat-treated GaAs, InP, and InGaAsP alloys
Authors: Kumar A. Shailendra , Narasimhan K. L. , Rajalakshmi R. , Chandvankar S. S. , Arora B. M.
Published: July 2002

Photothermal deflection spectroscopy is used to study the effect of heat treatment in bulk GaAs, InP, and epitaxial InGaAsP grown on InP. We show that increased sub-band-gap absorption is related to damage near the surface. We also show that from a measurement of the phase we can differentiate between purely surface and near-surface damage.
Electrical, crystallographic, and optical properties of ArF laser modified diamond surfaces
Authors: Geis M. W. , Rothschild M. , Kunz R. R. , Aggarwal R. L. , Wall K. F. , Parker C. D. , McIntosh K. A. , Efremow N. N. , Zayhowski J. J. , Ehrlich D. J. , Butler J. E.
Published: July 2002

Pulses of 193 nm radiation from an ArF laser with energies exceeding 0.5 J/cm2 have been shown to modify 40–60 nm thick layers of {100} and {110} oriented diamond surfaces. These layers exhibit highly anisotropic electrical and optical properties which have principal in-plane axes along the 〈110〉 directions. The minimum resistance is (4–10)×10−4 Ω cm, and minimum in the optical transmittance and maximum in the reflectance occur when the electric field vector of the incident polarized light is aligned along the low resistance direction. Transmission electron microscopy indicates that the modified layer primarily consists of unidentified graphite-like carbon phases embedded in diamond. The first-order electron diffraction spots correspond to lattice spacings of 0.123, 0.305, and 0.334 nm. The modified layer is stable at 1800 °C, forms ohmic contacts to type IIb diamond, and supports epitaxial diamond growth.
Time-of-flight measurement for electron velocity in p-AlGaAs/GaAs/AlGaAs at a high field
Authors: Furuta T. , Shigekawa N. , Mizutani T. , Yoshii A.
Published: July 2002

Time-of-flight measurements using a picosecond pulsed laser are made for a p-AlGaAs/GaAs/AlGaAs double heterostructure to successfully obtain the velocity-electric field relationship for photoexcited electrons at room temperature. In the high electric field region, velocity enhancements are observed, which have never been reported until now. Possible mechanisms, which attribute to the velocity enhancement, are also discussed.
Sulfur passivation of GaAs surfaces: A model for reduced surface recombination without band flattening
Authors: Spindt C. J. , Spicer W. E.
Published: July 2002

It has been shown by several workers that the passivation of GaAs surfaces using sulfides results in a large reduction in the surface recombination velocity accompanied by an increase in the band bending on n-type samples. This apparently contradictory pair of results leads to the suggestion that the responsible electronic states are a midgap donor compensated by an acceptor near the valence-band maximum. We explore the consequences of such a model, particularly when the midgap state is assumed to be a double donor. In the double donor case, simple qualitative arguments indicate that the surface recombination velocity can be reduced by a factor much greater than the reduction in surface-state density. The model is consistent with observations made using a variety of experimental techniques. A correlation between the electronic states and surface chemistry is made, and the As and Ga antisite defects are discussed as candidates for the donor and acceptor states.
Superconducting (Bi,Pb)-Ca-Sr-Cu-O thin films prepared i
n s
i
t
u by laser ablation
Authors: Ivanov Z. , Brorsson G.
Published: July 2002

Superconducting Bi-Ca-Sr-Cu-O and Bi-Pb-Ca-Sr-Cu-O films were grown in situ by excimer laser ablation from pressed powder and sintered superconducting targets, respectively. The substrate temperature during deposition was found to be important to obtain a maximum transition temperature. Both 110 and 80 K superconducting phases were obtained in films with a zero resistance at 74 K.
Weak flux pinning at grain boundaries in Ag sheathed Ba2YCu3O6+x tapes
Authors: Osamura K. , Takayama T. , Ochiai S.
Published: July 2002

This letter is concerned with the mechanism controlling the transport critical current measured at 4.2 K. The current densities increased with decreasing the oxide layer thickness of Ag sheathed tapes and reached 1010 A/cm2 at 15 T for the tape with a 15-μm-thick layer. The magnetic field dependence of critical current density in the region between 0.5 and 15 T can be explained in terms of a modified model of the theory by E. J. Kramer [J. Appl. Phys. 44, 1360 (1973)], based on the weak flux pinning along grain boundaries.
Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties
Authors: Wu Dong-Ho , Kennedy W. L. , Zahopoulos C. , Sridhar S.
Published: July 2002

We report the fabrication and high-frequency characterization of single crystals of Y1Ba2Cu3O7 with extremely sharp microwave transitions. The 10 GHz surface resistance Rs is less than 400 μΩ, at temperatures 4 K below the transition temperature. The electrodynamic characteristics of these crystals were examined via several measurements, and we demonstrate that high quality crystals which show very low Rs also possess small penetration depths λ(0)=1600 Å and small magnetic field effects on the penetration depth characterized by k(0)≡(dλ/dB2)T→0=10−3 Å/G2. In polycrystals, and even in poor single crystals, the presence of Josephson junctions of typical effective area ∼4 μm2 leads to poor microwave properties, with electrodynamic parameters orders of magnitude larger.
Nitrogen pair luminescence in GaAs
Authors: Liu Xiao , Pistol M.-E. , Samuelson L. , Schwetlick S. , Seifert W.
Published: July 2002

We report on the first observation of different nitrogen pair complexes in GaAs. These complexes, which have been searched for since the ’60s, are studied under the application of hydrostatic pressure. By carefully tuning the pressure, we make one after the other of the NNi pairs (1≤i≤10) appear in the band gap of GaAs and then become the major exciton recombination channel. We compare our results for nitrogen states in GaAs with the classical case of NNi excitons in GaP.
Preparation of highly coercive Sm-Fe-Ti by rapid quenching
Authors: Katter M. , Wecker J. , Schultz L. , Grössinger R.
Published: July 2002

The magnetic properties of the hard magnetic 20:70:10 (ω) phase in melt-spun Sm20Fe70+xTi10−x (x=−2,0,2) and Sm25Fe65.6Ti9.4 were investigated. The intrinsic coercivity iHc and the magnetization J were measured as a function of both the melt spinning parameters and various heat treatments. The maximum coercivities iHc at room temperature for the compositions Sm20Fe70Ti10 and Sm25Fe65.6Ti9.4 are 44.5 and 58 kOe, respectively. These values are among the highest reported so far for melt-spun materials. The formation of Sm(Fe,Ti)12 nuclei during rapid solidification is revealed by x-ray diffraction, and its influence on the formation of the ω phase is discussed. By investigating the section Smx(Fe0.875Ti0.125)100−x of the ternary phase diagram, using differential thermal analysis and x-ray diffraction, we proved the ω phase to be metastable.
YAG laser direct writing of copper from copper formate films
Authors: Müller Heinrich G.
Published: July 2002

Very thin copper lines for seeding of chemical copper deposition have been deposited by laser direct writing techniques, using water soluble precursor films from copper formate. Writing speeds of up to 50 mm/s could be reached. The deposition process has a strong influence on the substrate surface, thereby achieving a very stable film adhesion.
Carrier capture in intermixed quantum wires with sharp lateral confinement
Authors: Leier H. , Forchel A. , Maile B. E. , Mayer G. , Hommel J. , Weimann G. , Schlapp W.
Published: July 2002

We have fabricated GaAs/GaAlAs quantum wires with widths between 220 and 40 nm by high-dose (2×1014 cm−2) Ga implantation in a locally masked single quantum well structure. The width dependence of the emission energies indicates a steep 1D confinement determined by the lateral straggling of the implanted Ga. The external quantum efficiency of the wires increases strongly with decreasing mask width due to significant carrier capture from the lateral barrier.
Misfit dislocation multiplication processes in Si1−xGex alloys for x<0.15
Authors: Tuppen C. G. , Gibbings C. J. , Hockly M. , Roberts S. G.
Published: July 2002

The density of misfit dislocation sources in strained Si1−xGex layers grown on Si substrates is rarely sufficient to explain the observed extent of relaxation when layer thicknesses are in excess of the metastable critical thickness. This letter describes a process whereby a small, but finite number of misfit dislocation nucleation sources can lead to extensive strain relaxation across a complete wafer. Two novel mechanisms for misfit dislocation multiplication are presented and shown to be compatible with microscopic observations of chemically etched layers.
Material properties of p-type GaAs at large dopings
Authors: Tiwari Sandip , Wright Steven L.
Published: July 2002

We summarize the room-temperature minority-carrier mobility, minority-carrier lifetime, and effective band-gap shrinkage for p-type GaAs at large dopings, as determined from measurements on heterostructure bipolar transistors and published literature. The minority-carrier mobilities are significantly smaller than the majority-carrier mobilities, the lifetime data show a change in dependence on doping at 1×1019 cm−3, and the effective band-gap shrinkage is ≊5% at 1×1019 cm−3. The fits to electrical parameters described here should be of interest in modeling of minority-carrier devices.
Carbon-doped base GaAs/AlGaAs heterojunction bipolar transistor grown by metalorganic chemical vapor deposition using carbon tetrachloride as a dopant source
Authors: Cunningham B. T. , Stillman G. E. , Jackson G. S.
Published: July 2002

Carbon tetrachloride (CCl4) has been used as a carbon doping source for the base region of a GaAs/AlGaAs Npn heterojunction bipolar transistor (HBT) grown by low-pressure metalorganic chemical vapor deposition (MOCVD). Transistors were fabricated and characterized for dc current gain, emitter-base junction ideality factor, base contact resistance, and external base resistance. Microwave characterization by S-parameter measurement was performed to determine the common emitter current gain and maximum available gain as a function of frequency. Transistors with the base contact area self-aligned to a 3×10 μm emitter finger had a dc current gain as high as 50, an emitter-base junction ideality factor of n=1.2, and a current gain cutoff frequency of ft=26 GHz. Transistors of equal emitter area without self-alignment exhibited dc current gain as high as 86, n=1.2, and ft=20 GHz. A base contact resistance of Rc=2.85×10−6 Ω cm2 and an external base sheet resistance of Rs=533.4 Ω/⧠ were measured. These preliminary results indicate that carbon doping from CCl4 may be an attractive substitute for Zn or Mg in GaAs/AlGaAs HBT structures grown by MOCVD.
Electron focusing with multiparallel one-dimensional channels made by focused ion beam
Authors: Nakamura K. , Tsui D. C. , Nihey F. , Toyoshima H. , Itoh T.
Published: July 2002

Electron focusing effect is observed in a two-dimensional electron gas using samples with simple multiparallel one-dimensional channels made by a Be focused ion beam (FIB). Subharmonics and harmonics are resolved; their strengths allow a direct determination of the elastic scattering length le =1.8 μm and the specularity coefficient p=0.35 for electron reflection at the boundary defined by the FIB. The temperature dependence of the focusing effect is much weaker than the Shubnikov–de Haas effect.
Heteroepitaxial growth of layered transition metal dichalcogenides on sulfur-terminated GaAs{111} surfaces
Authors: Ueno Keiji , Shimada Toshihiro , Saiki Koichiro , Koma Atsushi
Published: July 2002

Layered transition metal dichalcogenides (MoSe2, NbSe2) have been heteroepitaxially grown on (NH4)2 Sx (x≂2) treated GaAs(111)Ga, GaAs(∼(111))As surfaces in spite of the large difference in their crystal structures. The in situ observation of reflection high-energy electron diffraction has shown that the grown film has its own lattice constant even from the first layer. The lattice matching condition, which is severely restricting in the usual heteroepitaxial growth case, is greatly relaxed in the present system because only weak van der Waals forces exist between the grown film and the substrate. This results from the fact that sulfur atoms regularly terminate dangling bonds on the GaAs surface after the (NH4)2Sx treatment.
YBaCuO input coils with low T
c and high T
c SQUIDs
Authors: Oh B. , Koch R. H. , Gallagher W. J. , Foglietti V. , Koren G. , Gupta A. , Lee W. Y.
Published: July 2002

We have efficiently coupled single-level YBaCuO (YBCO) input coils to superconducting quantum interference devices (SQUIDs) using coils and SQUIDs made on separate substrates and sandwiched together. At 4.2 K, the coupling efficiency α to a low noise Nb-based SQUID was ∼0.76, with no increase in flux noise. At 77 K, the coupling efficiency of a YBCO coil to a TlBaCaCuO SQUID was ∼0.81. The magnetic field sensitivity of the coupled high Tc SQUID at 77 K was 9 pT/√Hz at 1000 Hz, a five times improvement compared to the bare SQUID.
Precision AlGaAs Bragg reflectors fabricated by phase-locked epitaxy
Authors: Walker J. D. , Malloy K. , Wang S. , Smith J. S.
Published: July 2002

Extremely high quality AlGaAs Bragg reflectors have been fabricated by molecular beam epitaxy using advanced growth techniques including phase-locked epitaxy, short-period superlattices, and growth interruptions. These techniques are used to control the layer periodicity, interface flatness, and producibility of the structures. The experimental reflectance spectrum shows an extremely square stop band and very regular side lobes closely matching the theoretical spectrum. A comparison of experimental to theoretical reflectance spectra is used to show that the layer periodicity is maintained within 1% and the interface flatness controls the optical loss per interface to less than 0.1%. Experimental results show a maximum reflectance of 98.5% for a (AlAs)6(GaAs)3/(AlAs)1(GaAs)4 35.5-period Bragg reflector.
Effect of the critical current criteria on the I
c vs T relation near T
c in polycrystalline Y-Ba-Cu-O thin films
Authors: Lee Sang Young , Kim Y. H. , Park J. H. , Choi S. S.
Published: July 2002

We report on the temperature dependence of the critical current (Ic) near Tc for two Y-Ba-Cu-O thin films having zero-dissipation temperature (Tc) of 81 K and a Y-Ba-Cu-O thin film having Tc of 71 K. At temperatures higher than 0.9Tc, the critical current in a voltage criterion of 1 μV/cm appears proportional to (1−T/Tc)n with n≊2, and n≊1.5 in a 10 μV/cm criterion, exhibiting the dependence of n on the critical current criteria. This observation is in contrast with the report of n=1.5 by Ogale et al. [Phys. Rev. B 36, 7210 (1987)], Yuan et al. [J. Appl. Phys. 64, 4091 (1988)], and Horng et al. [Phys. Rev. B 39, 9628 (1989)], implying that n=2, the value for the superconductor-normal metal-superconductor tunneling junction of BCS superconductors near Tc must be taken into consideration to understand the intergrain tunneling process in polycrystalline high Tc thin films.
Superconductivity in a Ag-doped Bi-Pb-Sr-Ca-Cu-O system
Authors: Dou S. X. , Song K.-H. , Liu H. K. , Sorrell C. C. , Apperley M. H. , Savvides N.
Published: July 2002

For the Bi-Pb-Sr-Ca-Cu-O (BPSCCO) system, a consistent set of data for Tc, x-ray diffraction, and scanning electron microscopy shows that Ag additions strongly react with BPSCCO to destabilize the 110 K superconducting phase, resulting in a strong depression in Tc and lattice parameters when samples are treated in air or pure oxygen. This is in contrast to the behavior for the Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems, which do not show such degradation. However, Ag additions show no effects on Tc and lattice parameters when samples are treated under low oxygen pressure. The formation of a low-melting eutectic liquid with Ag2O-PbO-CuO solid solution affects the composition of the superconducting phase and degrades superconductivity, while the eutectic may be suppressed by reducing the oxygen partial pressure.
Atomic layer by atomic layer growth of DyBaCuO superconducting thin films by molecular beam epitaxy
Authors: Schuhl A. , Cabanel R. , Lequien S. , Ghyselen B. , Tyč S. , Creuzet G. , Siejka J.
Published: July 2002

Superconducting thin films of DyBaCuO have been achieved by molecular beam epitaxy. The films are strongly oriented with the c axis perpendicular to the substrate, and currently reach R=0 between 70 and 80 K. Critical temperatures (R=0) up to 50 K were obtained on 150-Å-thick films deposited atomic layer by atomic layer. These films present a flat surface as observed by high-energy electron diffraction. We show that in this process, a nominal 1:2:3 composition is not sufficient for the obtention of flat superconducting film. A good accuracy in the number of atoms deposited for each atomic layer is required.
Molecular beam epitaxial growth of (100) oriented CdTe on Si (100) using BaF2-CaF2 as a buffer
Authors: Tiwari A. N. , Floeder W. , Blunier S. , Zogg H. , Weibel H.
Published: July 2002

Epitaxial CdTe (100) has been grown on (100) oriented Si by molecular beam epitaxy using BaF2-CaF2 as a buffer. Two-dimensional (2-D) growth of BaF2(100) is obtained using low-temperature thermal cycles during growth. CdTe growth is also 2-D above 270 °C substrate temperature and a 2×1 surface reconstruction indicating a Te-stabilized surface is obtained. The growth is 3-D at lower substrate temperatures. Good structural quality films showing sharp electron channeling patterns and pronounced photoluminescence at 77 K are obtained. The full width at half maximum of the band-edge peak is 12 meV at 77 K.
InAs-AlSb quantum well as superconducting weak link with high critical current density
Authors: Nguyen Chanh , Werking James , Kroemer Herbert , Hu Evelyn L.
Published: July 2002

We have constructed a superconductor-semiconductor weak link using an InAs-AlSb quantum well as the channel between Nb electrodes. The structure draws on (a) the barrier-free nature of the Nb-InAs interfaces and (b) the combination of high electron concentrations and very high electron mobilities in the InAs wells, which yield a large superconducting coherence length (3700 Å) inside the channel. A large (lineal) critical supercurrent density of 32 mA/mm was obtained at 1.4 K, for a channel length of 0.6 μm. After temporary exposure to a magnetic field, the current-voltage characteristic became hysteretic, with an increase in critical current density to 132 mA/mm. The latter value corresponds to an areal current density of 8.8×105 A/cm2.