bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleation and growth mechanism of hemispherical grain polycrystalline silicon
Authors: Matsuo N. , Ogawa H. , Kouzaki T. , Okada S.
Published: July 2002

The formation of the nucleus [Watanabe et al., Extended Abstracts of the 22nd Conference on Solid State Devices and Materials (1990), p. 873] is performed at low O2 partial pressure during annealing and the density of HSG nuclei increases as the annealing time becomes longer. HSGs grow upward from the amorphous silicon surface, and twin formations are generated in almost all the HSGs. For approximately 50% of whole HSGs, polycrystalline silicon grows downward from the bottom of the HSG. A common heterogeneous material both for the nucleus formation of HSG and for that of polycrystalline silicon growing downward is thought to be formed at the interface between HSG and polycrystalline silicon.
Effect of free carriers on the linewidth enhancement factor of InGaAs/InP (strained-layer) multiple quantum well lasers
Authors: Tiemeijer L. F. , Thijs P. J. A. , Binsma J. J. M. , Dongen T. v.
Published: July 2002

In this letter the linewidth enhancement factor measured from a tensile strained, a compressively strained, and a lattice matched InGaAs/InP multiple quantum well laser is analyzed taking free- carrier effects into account. We find that the free carriers in the wells of compressively strained and lattice matched structures degrade the linewidth enhancement factor by about 40% due to the plasma effect. In tensile strained TM polarized lasers however, carrier movement parallel to the E vector is inhibited due to the quantum confinement, allowing a linewidth enhancement factor as low as 1.6 at the peak wavelength. Heterobarrier carrier leakage must be prevented using sufficiently large band-gap barrier and separate confinement layers, otherwise the free carriers in these layers result in an additional degradation of the linewidth enhancement factor.
Growth of YBa2Cu3O7−δ in pure ozone irradiated with ultraviolet light
Authors: Siegrist T. , Mixon D. A. , Coleman E. , Tiefel T. H.
Published: July 2002

Pure ozone has been successfully used as the source of reactive oxygen for in situ molecular beam epitaxy (MBE) growth of cuprate superconductor thin films. The thermally driven ozone-oxidation process is relatively inefficient, however, requiring high ozone partial pressures and leading in some cases to film nonuniformities. We show that pure ozone-oxidation during film deposition can be significantly enhanced by the additional use of ultraviolet (UV) irradiation. The UV energy produces excited-state O and O2 species from ozone via a chain-type mechanism, thereby increasing the ozone activity at least tenfold. In comparison to the film growth process relying solely on thermal ozone decomposition, it is possible to lower the ozone pressure by an order of magnitude while improving the quality of the superconducting films.
Giant nonlinear phase shift at exciton resonance in ZnSe
Authors: Saiki T. , Takeuchi K. , Kuwata-Gonokami M. , Mitsuyu T. , Ohkawa K.
Published: July 2002

We study the optical nonlinearity just at the exciton resonance in ZnSe at 8 K. A sample with thickness of 2.4 μm is grown by molecular-beam epitaxy on a GaAs substrate. Using reflection-type polarization spectroscopy with weak picosecond optical pulses, we observe nonlinear phase shift, being free from incoherent processes caused by the accumulation of excitons. A huge nonlinear phase shift, 0.15 deg cm2/kW, whose effective χ(3) is over 10−2 esu, with a response time shorter than 20 ps is obtained.
Two-dimensional quantum size effect on the internal photoemission
Authors: Lin Benjamin S. M. , Hwang J.
Published: July 2002

A two-dimensional (2D) quantum size concept is introduced here for interpreting internal photoemission phenomena. Theoretical results correspond well with published photoyield data for platinum silicide/p-type silicon Schottky barrier diodes. The difference between the optical barrier height and the thermal barrier height can be physically determined by momentum conservation when photoexcited carriers transport over a Schottky barrier. Finite yield at low photon energies and roll-off at high photon energies are well characterized by the 2D quantum model.
Pressure study of proximity effect induced scaling magnetoresistance in GaAs
Authors: Ghenim L. , Mani R. G.
Published: July 2002

A proximity effect induced scaling magnetoresistance observed in n-GaAs, n∼1019 cm−3, has been studied versus hydrostatic pressure, P, to 7 kbars. The scaling magnetoresistance is shown to be a homogeneous function of the magnetic field, B, and the pressure-dependent reduced temperature, τ(P)=[Tc(P)−T]/Tc(P), as ΔR/R‖s (T,B,P)=A0[τ(P)] f{B/[τ(P)]}, where Tc(P)=3.5 K−(0.06 K/kbar) P, and A0 is pressure independent. These results suggest that the pressure induced occupation of DX centers does not suppress the proximity effect in GaAs.
Quantitative determination of the remanent magnetization in ceramic YBa2Cu3O7 by detection of the second harmonic susceptibility−a new memory effect
Authors: Ritzi Th. , Heinzel Ch. , Neumann Ch. , Ziemann P.
Published: July 2002

A new ac technique based on the nonlinear magnetic response of sintered YBaCuO material is introduced to determine quantitatively the zero-field-cooled and field-cooled remanent magnetization of this high Tc superconductor. It is demonstrated that by applying a dc-compensation field Hcomp, the signal of the second harmonic susceptibility of this material can be minimized. Comparison to the results obtained by dc-magnetization measurements (SQUID magnetometer) on identical samples show, that Hcomp is proportional to the corresponding dc remanence. Thus, Hcomp provides a measure to exploit this ‘‘memory’’ effect of the second harmonic.
Microstructural investigations of light-emitting porous Si layers
Authors: George T. , Anderson M. S. , Pike W. T. , Lin T. L. , Fathauer R. W. , Jung K. H. , Kwong D. L.
Published: July 2002

The structural and morphological characteristics of visible-light-emitting porous Si layers produced by anodic and stain etching of single-crystal Si substrates are compared using transmission electron microscopy and atomic force microscopy (AFM). AFM of conventionally anodized, laterally anodized and stain-etched Si layers show that the layers have a fractal-type surface morphology. The anodized layers are rougher than the stain-etched films. At higher magnification 10 nm sized hillocks are visible on the surface. Transmission electron diffraction patterns indicate an amorphous structure with no evidence for the presence of crystalline Si in the near-surface regions of the porous Si layers.
Tracer diffusion of 110Ag in Bi2Sr2CaCu2Ox
Authors: Fang Y. , Danyluk S. , Goretta K. C. , Chen Nan , Runde M. , Rothman S. J. , Routbort J. L.
Published: July 2002

Tracer diffusion of 110Ag in dense polycrystalline Bi2Sr2CaCu2Ox has been measured at temperatures from 600 to 800 °C at an oxygen pressure of 105 Pa, and in oxygen partial pressures from 103 to 105 Pa at 700 °C. The diffusivity of Ag in Bi2Sr2CaCu2Ox is given by D=(8.9−4.2+7.9)exp[−(181.4±4.8 kJ/mol)/RT] cm2/s, and is not a sensitive function of oxygen partial pressure.
Influence of oxide charge on minority-carrier lifetime in metal-oxide-semiconductor capacitors
Authors: Meinertzhagen A. , Rharbi S. El , Jourdain M.
Published: July 2002

Oxide charge produces some well-known effects on the capacitance versus voltage and on the oxide current versus voltage measurements of metal-oxide-semiconductor capacitors. We report here a shift of the C(ω) and G(ω)/ω curves [G(ω) and C(ω) being respectively the conductance and capacitance] to the lower frequencies which could be related to an increase of the minority-carrier lifetime.
Fabrication of modified lead iron niobate films
Authors: Vasant Kumar C. V. R. , Sayer M. , Pascual R.
Published: July 2002

The fabrication of new ferroelectric modified lead iron niobate films having an approximate composition Pb[(Fe0.7Cr0.2Ni0.1)0.5Nb0.5]O3 is reported. A magnetron sputtering technique was used for the deposition of the films and a post-deposition annealing at 800 °C for 5 s in a rapid thermal processing furnace crystallizes the films principally into a perovskite-type structure. Ferroelectricity in these films was confirmed by the presence of hysteresis loops, with a remanent polarization of 15 μC/cm2, and coercive field of 100 kV/cm. The room-temperature dielectric constant measured at 1 kHz was 640 and the dissipation factor was 0.1.
Raman spectra of individual Si thin layers with 4–40 atomic layer thicknesses buried in GaAs (001)
Authors: Tanino H. , Kawanami H. , Matsuhata H.
Published: July 2002

We present a Raman scattering study of 4–40 layer thick Si films grown epitaxially on GaAs (001) and covered by GaAs. The peak shift and the broadening of the optical phonon modes of Si are discussed in terms of the planar biaxially tensile strains in the Si thin layers, the partial lattice relaxation, and the phonon confinement effect in the layers. The extraordinarily broad peaks of the Si phonon modes of the 4–8 layer thick films are not sufficiently explained by the above effects. We propose the three-dimensional confinement effect into the quantum well disks as a candidate of the origin of the peak energy shift and the broadening of the phonons.
Oxygen assisted ohmic contact formation mechanism to n-type GaAs
Authors: Lustig Naftali , Schad R. G.
Published: July 2002

The presence of oxygen in the top W layer of NiGe(Au)W ohmic contacts to n-type GaAs is found to play a critical role in reducing their contact resistance. Contacts with sputtered W containing less than 1 at. % oxygen and formed by rapid thermal annealing (RTA) yield a contact resistance (RC) greater than 0.45 Ω mm. Contacts with a reactively sputtered or electron-beam evaporated metallic W oxide top layer, containing ∼25 at. % oxygen, yield RC’s of less than 0.15 Ω mm. Auger depth profiles of the reacted contacts show a significant outdiffusion of Ga from the GaAs substrate in the presence of the oxygenated W but not in the oxygen-free contacts. A contact formation mechanism based on the gettering of Ga atoms by oxygen is proposed.
Boundary layer elasto-optic switching in ferroelectric liquid crystals
Authors: Parmar D. S.
Published: July 2002

Utilizing a simple new configuration, one rigid surface and the other exposed directly to the gas flow, elasto-optic switching in thin (∼2 μm) ferroelectric liquid crystal films is observed when a gas flow is impingement in the plane of smectic layers. The elasto-optic response caused by the shear stress is large, fast, and reversible.
Linewidth dependence of notchlike void generation in fine aluminum conductors
Authors: Yamaji Tetsuo , Igarashi Yasushi , Nishikawa Satoshi
Published: July 2002

In a silicon integrated circuit, stress-induced void generation in fine Al conductor lines degrades device reliability. Optically observable void (often called ‘‘notchlike void’’) generated during the manufacturing process was investigated. It was experimentally observed that void generation decreases with decreasing linewidth in the width range narrower than about 1.8 μm. The reduction was attributed to the decreasing gradient of tensile stress in the line. The stress gradient was obtained by stress analysis using a numerical simulator. It was proposed from the determined activation energy of Al diffusion that lattice diffusion of Al atoms is the rate limiting process for notchlike void generation.
Enhanced modulation bandwidth of strained multiple quantum well lasers
Authors: Morton P. A. , Temkin H. , Coblentz D. L. , Logan R. A. , Tanbun-Ek T.
Published: July 2002

We compare the dynamic properties of bulk, lattice-matched, and strained multiple quantum well (MQW) 1.3 μm Fabry–Perot lasers up to high-bias levels. We show for the first time that long wavelength strained MQW lasers can have a higher intrinsic bandwidth than bulk active and lattice-matched MQW lasers, and that a −3 dB bandwidth of over 30 GHz can be expected from devices with a thin separate confinement heterostructure if a low parasitic device structure is used. The K factor used to determine maximum bandwidth in bulk active laser diodes is shown to be unsuitable for strained MQW devices, where a linear relationship of damping/(resonance frequency)2 is not observed at high power levels.
Diffusion in Ni/Cu bilayer films
Authors: Bai P. , Gittleman B. D. , Sun B. -X. , McDonald J. F. , Lu T. -M. , Costa M. J.
Published: July 2002

It is shown that the diffusion of Cu into the Ni layer of a Ni/Cu bilayer film after thermal annealing is significantly reduced when the deposition temperature of the Ni layer is raised from approximately 50 to 200 °C. The effect of the deposition temperature on the physical structure of the Ni layer and the possible connection between the Ni layer physical structure and the diffusion reduction are investigated. The effect of the diffusion on the resistivity of the Cu layer is also studied.
Preparation of superconductive Y-Ba-Cu-O layers formed by aggregates of released particles using laser deposition in air
Authors: Wild Jan , Engst Pavel , Civiš Svatopluk , Pochylý Jiří , Prachařová Jarmila
Published: July 2002

Superconductive Y-Ba-Cu-O layers formed by aggregates of released particles were prepared by laser deposition using a nontraditional method without a vacuum apparatus, in air, at atmospheric pressure. The layers were deposited on a single-crystal MgO (001) substrate at a temperature of 973 K. A zero-resistance critical temperature of 69 K was attained after annealing in an oxygen stream at 1173 K. The deposited layers were analyzed by x-ray powder diffraction, scanning electron microscopy, and energy-dispersive x-ray analysis.
Short-range order effects on copper L3,2 transitions in Cu-Pd alloys
Authors: Krishnan Kannan M. , Menon E. S. K. , Huang P. , Singh Prabhakar P. , de Fontaine D.
Published: July 2002

The unoccupied d-electron density of states of a range of Cu1−xPdx (x=0–0.35) alloys, based on measurements of copper L3,2 transitions in electron energy-loss spectroscopy, is shown to be critically dependent on short-range order. This finding is supported by band structure calculations where the d-hole count at the Cu site for disordered alloys is found to be independent of the composition. Based on the above, a linear correlation between the degree of short-range order, as defined by the splitting of the diffuse maxima in the diffraction patterns, and the d-band occupancy has been established.
Thermally curable second-order nonlinear-optical polymer
Authors: Yu Luping , Chan Waikin , Dikshit Srivatsan , Bao Zhenan , Shi Yongqiang , Steier William H.
Published: July 2002

A thermally cross-linkable, second-order nonlinear optical (NLO) polymer containing ethynyl groups has been synthesized. The ethynyl groups in the polymer backbone can undergo thermal intramolecular or intermolecular reactions with amide groups to form heterocyclic structures or cross linkages. The thermal curing of the polymer can be simultaneously effected during electric poling and second-harmonic generation measurements indicated that the cured polymers indeed showed high stability in dipole orientation; no obvious decay at room temperature for more than 1000 h. Long-term stability of second-harmonic coefficients was observed even at 90 °C, at least for 500 h.
Electron cyclotron resonance plasma-enhanced filament-assisted diamond growth
Authors: Tsai W. , Reynolds G. J. , Hikido S. , Cooper C. B.
Published: July 2002

A novel technique was developed to grow high-purity polycrystalline diamond films at 850 °C and 50 mTorr with 10% CH4, 2% O2, and balance H2 using a filament-assisted chemical vapor deposition technique in combination with an electron cyclotron resonance (ECR) plasma. Using Raman spectroscopy and in situ plasma diagnostics, we have shown that the hydrogen plasma selectively etched nondiamond components during deposition. Experiments with ECR plasma and the filament-assisted technique from 10−6 Torr to 50 mTorr and 500–1000 °C indicated that low-energy electrons are a key factor in growth of diamond thin films.
Intersubband absorption line shape in tunneling superlattices
Authors: Zal/użny M.
Published: July 2002

The influence of the depolarization effect on the intersubband absorption spectrum of the weakly tunneling superlattices is discussed within a tight-binding approximation. The calculations are performed in the framework based on the density-functional formulation. Obtained results show that the intersubband excitations in tunneling superlattices are not only shifted in energy as compared to the one electron levels; the depolarization effect also manifests itself in a substantial modification of the absorption line shape.
Gas-exposure enhanced Na* emission from Na-rich surfaces
Authors: Xu Jun , Albridge Royal , Barnes Alan , Yang Xinxing , Tolk Norman
Published: July 2002

The optical emission attributed to electronically desorbed excited sodium atoms from NaCl and Na-evaporated surfaces is shown to be enhanced by exposure of the surface to gaseous CO2 and N2. This is the first observation of enhancement of electron-stimulated desorption of substrate atoms caused by the exposure of surfaces to gaseous molecules which do not contain the desorbed atoms. The large amount of excited-sodium yield at 60 K provides evidence for nonexistence of the secondary-electron excitation of thermally desorbed ground sodium.
Temperature-tuned noncritically phase-matched picosecond LiB3O5 optical parameter oscillator
Authors: Ebrahimzadeh M. , Hall G. J. , Ferguson A. I.
Published: July 2002

Efficient picosecond optical parametric oscillation in LiB3O5 is demonstrated using ∼55 ps pump pulses at 523.5 nm, obtained from a frequency-doubled, mode-locked, Q-switched, diode-laser-pumped Nd:YLF laser. By exploiting temperature tuning under noncritical type I phase matching, continuously tunable radiation over the range 0.909–1.235 μm has been generated at external power conversion efficiencies approaching 50%. The oscillator has a pump power threshold of 4.5 mW, corresponding to a Q-switched pulse energy of 9 μJ, and can provide a total average output power of 8 mW at 500 Hz, in pulses of ∼33 ps duration. At five times above threshold, the internal pump depletion of the oscillator was 54%.
Refractive index determination of SiGe using reactive ion etching/ellipsometry: Application of the depth profiling of the GE concentration
Authors: Kroesen G. M. W. , Oehrlein G. S. , de Frésart E. , Scilla G. J.
Published: July 2002

The complex refractive index at a wavelength of 632.8 nm of strained epitaxial SiGe layers on silicon substrates has been determined as a function of the germanium content using in situ ellipsometry during reactive ion etching. The germanium concentration was obtained from Rutherford backscattering. These index values are used to invert the ellipsometry equations. Using this principle, the Ge concentration depth profile of an unknown SiGe structure can be determined from an in situ ellipsometry measurement sequence that is taken while the unknown sample is being etched
High speed operation of very low threshold strained InGaAs/GaAs double quantum well lasers
Authors: Zhao B. , Chen T. R. , Zhuang Y. H. , Yariv A. , Ungar J. E. , Oh S.
Published: July 2002

Very low threshold current strained In0.2Ga0.8As/GaAs double quantum well buried-heterostructure lasers have been fabricated by a hybrid metalorganic chemical vapor phase deposition and liquid phase epitaxy regrowth technique. The modulation bandwidths were compared in lasers of different active strip widths, cavity lengths, and facet reflectivities in order to achieve modest high-modulation bandwidth at low operating current. A 5 GHz 3 dB modulation bandwidth is demonstrated at a current of 2.1 mA in a laser with a threshold current of 0.5 mA.
Hydrogen coverage during Si growth from SiH4 and Si2H6
Authors: Gates S. M. , Kulkarni S. K.
Published: July 2002

Time-of-flight direct recoiling (DR) measurements of surface hydrogen coverage (θH) are made in situ during chemical beam epitaxy growth of Si from Si2H6 on Si(100) as a function of temperature and disilane flux. Temperatures (T) of 300–900 °C and fluxes from 1015 to 1017 molecules cm−2 s−1 are used. Limited data for SiH4 are also presented. Predictions of θH from a steady state kinetic model are compared with the measurements, enabling the reactive sticking probability (S) of Si2H6 to be estimated at T≳500 °C.
Origin of the nonlinear index saturation in the band tail absorption region of GaAs/AlGaAs multiple quantum wells
Authors: Sfez B. G. , Oudar J. L. , Kuszelewicz R. , Pellat D.
Published: July 2002

The saturation behavior of the nonlinear index δnNL in the band tail of GaAs/AlGaAs multiple quantum wells is experimentally studied in quasi-steady state and in a low absorption region (below 300 cm−1), where dispersive optical bistability is observed. Measurements at different detunings from the exciton resonance allow us to study the absorption dependence of the saturation parameters. The saturation intensity IS is found inversely proportional to the linear absorption coefficient, while the saturating nonlinear index δnS is approximately constant. This evidences that the nonlinear index saturation is due to a saturation of the carrier density versus light intensity, due to the saturation of the band tail absorption itself.
High temperature thermally stable implant isolation for GaAs via void formation
Authors: Ko Kei-Yu , Chen Samuel , Lee S.-Tong , Braunstein G.
Published: July 2002

A new method of forming thermally stable high-resistivity regions is developed for device isolation in GaAs. For Al+-implanted epitaxial-layer structures, the sheet resistivity increases by about six orders of magnitude from the as-grown values, after annealing in the 700–900 °C range. This increase in resistivity is shown to correlate with the formation of voids. The creation of high resistivity via void formation is different from the conventional damage-induced isolation by H or O implantation. This type of isolation becomes ineffective once the lattice is annealed at high temperatures due to the annealing out of lattice damage between 400 and 700 °C. In contrast, voids are stable at high temperatures. The potential advantages of using such defects for device isolation will be discussed.
Fluorine ion induced enhancement of oxide removal prior to silicon epitaxial growth
Authors: Lou Jen-Chung , Oldham William G. , Kawayoshi Harry , Ling Peiching
Published: July 2002

Low-temperature epitaxial growth of Si using a dichlorosilane-hydrogen mixture in a hot-wall reactor has been studied with respect to in situ predeposition oxide removal. With BF2+ or F+ ion implantation prior to the final substrate cleaning step, ‘‘native’’ or ‘‘chemical’’ surface oxide layers are completely removed in a short 900 °C prebake. For 850 °C epitaxial deposition following the prebake, BF2+ or F+ implanted regions are defect free whereas unimplanted regions on the same wafer show a textured surface and contain large numbers of interfacial inclusions. The enhancement in the surface oxide removal in implanted areas is attributed to a high density of initiation sites for the Si-SiO2 oxide decomposiiton reaction.
Contrast formation mechanism for the surface defects imaged by x-ray topography under the condition of simultaneous specular and Bragg reflections
Authors: Kitano T. , Kimura S , Ishikawa T.
Published: July 2002

X-ray topography using extremely asymmetric diffraction under the specular reflection condition is effective for imaging a short-range strain field near the surface. This experimental condition is easily realized by utilizing the tunability of synchrotron radiation. The surface defect images are clearly observed as a result of the reduction of background due to dynamical diffraction from the highly perfect bulk crystal.
Tl-Ca-Ba-Cu-O step-edge Josephson junctions
Authors: Martens J. S. , Zipperian T. E. , Vawter G. A. , Ginley D. S. , Hietala V. M. , Tigges C. P.
Published: July 2002

There has been considerable progress in the development of nonhysteretic Josephson junction microelectronic technologies for YBaCuO. Such a technology for Tl-Ca-Ba-Cu-O junctions would be interesting because of the higher operating temperatures and the very different grain boundary structures in the different cuprate superconductors. We have successfully made step-edge junctions with TlCaBaCuO grown on ion-milled LaAlO3. Nonhysteretic grain boundary-based junctions have been demonstrated with critical current-normal state resistance products exceeding 5 mV at 77 K, critical current densities ranging from 500 to 25 000 A/cm2, and critical current versus field profiles suggesting very uniform junctions. Yield has exceeded 70% on over 250 junctions tested and operation has been demonstrated to 100 K.
Picosecond transient photoluminescence spectra of ZnSe-ZnS strained-layer superlattices grown on GaAs(001) by molecular beam epitaxy
Authors: Cui Jie , Wang Hai-Long , Gan Fu-Xi , Huang Xu-Guang , Cai Zhi-Gang , Li Qing-Xing , Yu Zhen-Xin
Published: July 2002

Picosecond transient photoluminescence spectra were carried out on ZnSe-ZnS strained-layer superlattices at 77 K. The typical exciton formation time and exciton lifetime are 40 and 100 ps, respectively. The relationship between exciton lifetime and the well width is also given.
Anomalous splitting in the photoreflectance response of semi-insulating GaAs and correlation with EL2
Authors: Durbin C. , Estrera J. P. , Glosser R. , Duncan Walter , Henry R. L. , Nordquist P. , Bottka N. , Gaskill D. K.
Published: July 2002

Anomalous splitting has been observed in the photoreflectance (PR) response of SI:GaAs in the vicinity of the exciton at 78 K. Photoluminescence (PL) measurements suggest the splitting is correlated with the EL2 content of the samples. Separation between the two peaks in PR measurements range from about 2 to 4 meV. A striking effect is that each peak is maximized by a different phase setting of the lock-in. The splitting is sample dependent and is also affected by several other factors including surface conditions, temperature, pump beam intensity, and modulation frequency.
Novel approach to CuInSe2-based thin-film photovoltaic cells
Authors: Menezes Shalini
Published: July 2002

A new n-CuInSe2-based cell has been constructed with a concerted effort at the synthesis of n-CuInSe2 thin-film absorber and the electrochemical conversion of the CuInSe2 surface to a semi-insulating, lattice-matched CuInxSeyIz transition layer and a semiconducting p-CuISe3 window. The CuISe3 layer can be anodically formed on n-type or p-type CuInSe2; it forms a rectifying p-n junction with n-CuInSe2 and an ohmic contact with p-CuInSe2. This cell obviates some of the prevailing concerns with the p-CuInSe2/n-CdS cell while retaining the thin-film attributes of the radiation-tolerant CuInSe2.
Theory of phonon-limited mobility in a delta-doped quantum well
Authors: Ahn Doyeol
Published: July 2002

The electron mobility at room temperature due to phonon scatterings in a delta-doped quantum well is calculated theoretically. A many-body formalism is used to obtain self-energy terms for electron-phonon interactions. It is predicted that the electron mobility is reduced significantly by several factors with increasing delta-doping in a quantum well.
High power and high efficiency vertical cavity surface emitting GaAs laser
Authors: Sun D. C. , Friberg S. R. , Watanabe K. , Machida S. , Horikoshi Y. , Yamamoto Y.
Published: July 2002

We report high power and high efficiency operation of a vertical cavity surface emitting GaAs laser in an external cavity. The maximum cw output power from the fundamental TEM00 mode was 700 mW at a temperature of 77 K when pumped by a cw krypton-ion laser with 1.8 W pump power. We obtained an absolute quantum efficiency (pump photons to lasing photons) of 44%, and a differential efficiency above threshold of 58%.
Bilayer reflection-high-energy-electron-diffraction intensity oscillations observed during growth on double-domain Si(001) surfaces
Authors: Ohtani N. , Mokler S. M. , Zhang J. , Joyce B. A.
Published: July 2002

Bilayer reflection-high-energy-electron diffraction (RHEED) intensity oscillations were observed during growth on a double-domain Si(001) substrate during silicon gas-source molecular beam epitaxy (Si-GSMBE) using disilane. A transition from monolayer- to bilayer-mode oscillation behavior was observed in the [110] azimuth during growth. Oscillations began with an asymmetric monolayer waveform which transformed into an apparent bilayer mode following several oscillation periods. Simultaneous measurement of RHEED intensity oscillations of the specular beam and (1×2) and (2×1) reconstruction related beams in the [010] azimuth showed that the bilayer oscillations resulted from alternating surface reconstructions. The origin of these bilayer oscillations is discussed on the basis of the anisotropic growth kinetics on Si(001) surfaces.
In situ Hall measurement of two-dimensional electron gas at Al0.3Ga0.7As/GaAs interface irradiated with 10-keV Ar ions
Authors: Kanayama Toshihiko , Takeuchi Yukihiro , Sugiyama Yoshinobu , Tacano Munecazu
Published: July 2002

In situ Hall measurements reveal that the mobility of two-dimensional electron gas 80-nm-deep from the surface decreases simultaneously with 10-keV Ar-ion irradiation at 90 K. This demonstrates that penetration of irradiation defects far beyond the ion range (projected range =8.8 nm) is due to the channeling effect. Annealing of the irradiated sample was also performed. Partial recovery in the mobility observed indicates that the defects become thermally mobile at above 200 K.
Luminescence cycling and defect density measurements in porous silicon: Evidence for hydride based model
Authors: Prokes S. M. , Carlos W. E. , Bermudez V. M.
Published: July 2002

Changes in dangling bond densities in porous silicon were measured and results indicate a relatively low dangling bond density (roughly 3×1016 bonds/cm3) in as-prepared samples, which increases by a factor of 6–7 upon quenching of the photoluminescence (PL). The electron spin resonance (ESR) data suggest the presence of significant disorder in the as-prepared 1 Ω cm porous silicon samples, which may correlate with an enhanced PL intensity. The results of heat cycling and HF dipping experiments suggest that a continuous decrease in particle size does not result in a continuous PL blue shift, as would be expected in the quantum confinement model. These results will be discussed in terms of a hydride/polysilane luminescence mechanism.
Infrared Raman study of the phonon linewidth and the nondiamond carbon phase in 〈110〉 and 〈100〉 textured polycrystalline diamond films
Authors: Wagner J. , Wild C. , Müller-Sebert W. , Koidl P.
Published: July 2002

Raman spectroscopy has been used to study the width of the 1332 cm−1 phonon line and the relative intensity of scattering from nondiamond carbon in 〈110〉 and 〈100〉 textured diamond films prepared by low pressure chemical vapor deposition. Infrared excitation at 1.16 eV has been used to give a high sensitivity to amorphous graphitelike carbon inclusions in diamond films. For 〈110〉 textured films a narrowing of the phonon linewidth is observed with decreasing intensity of scattering from amorphous carbon. Films with vanishing Raman scattering from nondiamond carbon, even under infrared excitation, exhibit the narrowest phonon linewidth of about 4 cm−1. For 〈100〉 textured films also a comparatively narrow phonon linewidth is observed in spite of the strong Raman signal from nondiamond carbon. This can be explained by defective growth sectors terminated by {111} facets which surround the almost perfect 〈100〉 columns.
Rapid thermal oxidation of thin nitride dielectrics deposited on rapid thermal nitrided polycrystalline silicon
Authors: Itoh S. , Lo G. Q. , Kwong D. L. , Mathews V. K. , Fazan P. C.
Published: July 2002

This letter compares the effects of two different oxidation techniques, i.e., rapid thermal and conventional wet (steam) oxidations, on the dielectric breakdown and charge trapping characteristics of thin Si3N4 films deposited on rapid thermally nitrided polycrystalline silicon. Results show that, in addition to the low thermal budget, rapid-thermal-oxidized Si3N4 shows superior time-dependent dielectric breakdown characteristics in terms of reduced defect densities and improved film intrinsic properties. Compared to wet-oxidized dielectrics, suppressed charge trapping is observed for rapid-thermal-oxidized Si3N4 stacked dielectrics.
Fast turn-off of two-terminal double-heterojunction optical thyristors
Authors: Heremans P. L. , Kuijk M. , Borghs G. , Suda D. A. , Hayes R. E. , Vounckx R.
Published: July 2002

A double-heterojunction optical thyristor is presented, that can be turned off in a few nanoseconds simply by using the anode to a negative voltage exceeding a certain threshold. Previously, nanosecond-range turn-off could only be achieved by carrier extraction via contacts to either or both of the center two thyristor layers. Our turn-off method uses a PnpN layer structure for which punch-through of the n-layer under reverse bias of the P-n diode can be reached before this diode breaks down. We thus achieve an improvement in turn-off time by about 3 orders of magnitude over traditional two-terminal thyristors.
Confocal photoluminescence: A direct measurement of semiconductor carrier transport parameters
Authors: Fong Yu-Chue , Brueck S. R. J.
Published: July 2002

Using confocal microscopy a direct measurement of the minority carrier diffusion length of 5 μm is obtained for a 3-nm thick AlGaAs/GaAs graded-index separate confinement heterostructure. A photoluminescence spatial resolution of <1 μm is obtained by translating the collection aperture of the confocal microscopy arrangement. This technique provides a method for obtaining spatial resolution in photoluminescence from semiconductor structures that is limited only by the optics rather than by carrier transport effects. This resolution is illustrated by monitoring enhanced carrier transport for a transversely graded thickness quantum well formed by metalorganic chemical vapor deposition growth over a cleaved sample edge.
Reactive epitaxy of [001] europium on [001] CdTe
Authors: Gros P. , Chami A. C. , Daudin B. , Ligeon E.
Published: July 2002

Europium has been epitaxially grown on [001] CdTe by molecular beam epitaxy. It has been shown that an intermediate layer, likely EuTe with a NaCl-type structure, was formed prior to the growth of pure europium. It was demonstrated by ion channeling experiments and reflection high energy electron diffraction observations that the [001] bcc europium axis was parallel to [001] of CdTe and that the [110] europium direction was parallel to the [100] one in CdTe. The observed relationship corresponds to an extremely low mismatch. Further growth of a [001] CdTe overlayer onto europium was also demonstrated.
Order-of-magnitude method for estimating the fluence that optimizes the critical current in particle-irradiated cuprate superconductors
Authors: Weaver B. D. , Summers G. P.
Published: July 2002

The particle fluence that maximizes the critical current enhancement in cuprate superconductors is shown to be closely related to the nonionizing energy loss (displacement damage) of a given particle. In many cases, only the incident particle type and energy need to be known in order to allow an order-of-magnitude prediction of the optimal fluence for enhancing the critical current.
Observation of a new ordered structure in GeSi/Si strained layer superlattice
Authors: Zhong Peixin , Zheng Youdou , Zhang Rong , Hu Liqun
Published: July 2002

We report a new kind of ordered structure in the GeSi sublayer of GeSi/Si superlattice. X-ray diffraction of GeSi/Si superlattice exhibits extraordinary peaks of 1/2(111), 3/2(111), (222) on (111) sample, and (200) on (100) sample. This shows that the germanium and silicon atoms in the GeSi sublayer are ordered due to the strain rather than randomly distributed in bulk GeSi alloy. Two coexisting models of order have been suggested for the (111) sample. The atoms in the ordered structure are aligned as Ge-Si-Ge-Si and Ge-Si-Si-Si along the (111) axis. The relative ratio of the two models has been calculated for the experimental result. The ordered structure may have significant effect on the band structure and optical properties.
Selective growth of InGaAs/InP heterojunction bipolar transistors with a buried subcollector
Authors: Frei M. R. , Hayes J. R. , Song J.-I. , Cox H. M. , Caneau C.
Published: July 2002

We demonstrate the fabrication of an InGaAs/InP heterojunction bipolar transistor (HBT) with a reduced base-collector overlap area using selective epitaxy techniques. The process uses planarizing growth by chloride-transport vapor-phase epitaxy (VPE) to create a buried subcollector layer, followed by selective regrowth by organometallic VPE. The quality of the regrowth over the planarized substrates is evident from the dc characteristics of the HBT which show an ideality factor η=1.05 for the base-emitter junction.
Photoelectric properties in microscopic p-n junctions of organic semiconductors
Authors: Saito Kazuhiro , Sugi Michio
Published: July 2002

Photodiodes containing microscopic p-n junctions of organic dyes were fabricated using the Langmuir–Blodgett technique. Their action as p-n junctions was confirmed by measurement of transient photoinduced voltage responses to impulsive laser light irradiation. The signal is characterized by a rapid rise followed by a slow decay, which are assignable to the photoinduced electron transfer from n-type dye to p-type dye and the reverse transfer through the junction, respectively. The decay process shows a long-time tail and cannot be described by a single exponential function.
Preparation of high J
c Ba2YCu3O7−y-Ag composite films on SrTiO3 (100) substrates by the dipping-pyrolysis process
Authors: Kumagai T. , Manabe T. , Kondo W. , Mizuta S. , Arai K.
Published: July 2002

Superconducting Ba2YCu3O7−y (BYCO)-Ag composite films with an (Ag/BYCO) molar ratio of 0.2 were prepared on SrTiO3(100) substrates by the dipping-pyrolysis process through heat treatments at 700–800 °C under a low-oxygen partial pressure (=2×10−4 atm) followed by O2 annealing. The product films were highly c-axis oriented and gave sharp rocking curves. High superconducting transition temperature Tc, zero(r) of 89 K and high critical current density Jc (77 K, 0 T) of 1.1×106 A/cm2 were obtained for a 0.9-μm-thick composite film heat treated at 770 °C.
Superconducting epitaxial Tl2Ba2CaCu2O8 films on sapphire with cerium oxide buffer layers
Authors: Holstein W. L. , Parisi L. A. , Face D. W. , Wu X. D. , Foltyn S. R. , Muenchausen R. E.
Published: July 2002

Epitaxial Tl2Ba2CaCu2O8 films were prepared on (11̄02)Al2O3 with (100) CeO2 buffer layers. The Tl2Ba2CaCu2O8 was epitaxially oriented with its c axis perpendicular to the substrate surface and [100] Tl2Ba2CaCu2O8 aligned with [100] CeO2 and [22̄01] Al2O3. The films exhibited Tc of 97–98 K as measured both inductively and by ac magnetic susceptibility. Direct transport critical current density Jc at 75 K was 2.8×105 A/cm2.
Elimination of the kink effect in GaAs metal semiconductor field-effect transistors by utilizing a low-temperature-grown buffer layer
Authors: Haruyama Junzi , Goto Norio , Negishi Hitoshi
Published: July 2002

GaAs metal semiconductor field-effect-transistors (MESFETs) utilizing a nondoped GaAs buffer layer grown by molecular beam epitaxy at 300 °C do not show the kink effect which is observed in GaAs MESFETs utilizing a nondoped GaAs buffer layer grown at 600 °C. However, in both types of FETs, almost the same photoemissions caused by drain avalanche multiplication, are observed between the gate and the drain. A deep level transient spectroscopy (DLTS) spectrum shows that the low-temperature buffer (LTB) layer contains a deep level similar to the EL-2 level with high density. The kink effect may be eliminated because the deep level works as a large recombination center for holes generated by drain avalanche multiplication.
Shubnikov–de Haas oscillations in n-CuInSe2
Authors: Arushanov E. , Essaleh L. , Galibert J. , Leotin J. , Arsene M. A. , Peyrade J. P. , Askenazy S.
Published: July 2002

The results of the Shubnikov–de Haas oscillations measurements on CuInSe2 crystals are presented for the first time. The measurements were performed in the temperature range from 1.9 to 40 K in pulsed magnetic field up to 40 T. It was found that the Fermi surface of electrons consisted of one sphere. The values of cyclotron effective masses, the effective mass at the bottom of the conduction band, the interband momentum matrix element and g*-factor were calculated.
Characterization of a GaAs/AlGaAs modulation-doped dynamic random access memory cell
Authors: Kleine J. S. , Cooper J. A. , Melloch M. R.
Published: July 2002

We report the electrical properties of a GaAs dynamic random access memory (DRAM) cell in which the storage capacitor is a modulation-doped heterojunction and the access transistor is a modulation-doped field-effect transistor. Experimental waveforms illustrating both reading and writing are exhibited. Isolated storage capacitors have 1/e storage times as long as 4.3 h at room temperature. The complete DRAM cell exhibits a room temperature storage time of about 3 min, limited by gate leakage in the access transistor.
Nanometer patterning of InP using aerosol and plasma etching techniques
Authors: Wiedensohler Alfred , Hansson Hans-Christen , Maximov Ivan , Samuelson Lars
Published: July 2002

By the application of aerosol techniques for the deposition of well-defined particles of silver in combination with methane-based electron cyclotron resonance plasma etching, we have been able to fabricate nanometer sized columns of InP. Silver particles are produced via homogeneous nucleation out of silver vapor saturated nitrogen gas from a tube furnace at around 1100 °C and, after size selection, deposited on the surface of InP. Scanning electron microscope images show that equally sized particles of silver, with an effective diameter in the range 20–40 nm, can be generated and deposited on the semiconductor. In a dry etching process applied subsequently we transfer vertically the feature of the particles into the InP material underneath producing free-standing columns of InP with diameters as small as 50 nm.
Subsaturation ferromagnetic resonance in yttrium iron garnet spheres
Authors: Bryant P. H. , Carroll T. L. , Pecora L. M. , Rachford F. J.
Published: July 2002

Experimental data is presented for ferromagnetic resonance in an yttrium iron garnet sphere slightly below the threshold field for saturation. It is found that significantly different behavior occurs depending on whether the dc field is aligned with the [111], [100], or [110] axes of the crystal. Explanations are proposed to account for the observed behavior, which in the [100] and [110] cases involve the formation of macroscopic magnetization patterns. These two cases also exhibit frequency reversal below threshold, in which the frequency is observed to increase as the field is decreased.
Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp
Authors: Ruyten Wilhelmus M. , Keefer Dennis
Published: July 2002

We have studied the use of optogalvanic measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser induced fluorescence signals from an arcjet plume. By using a narrowband, frequency stabilized dye laser, a 5 MHz absolute accuracy was achieved, even using lines with widths in excess of 1 GHz. However, with the laser beam aligned along the axis of the hollow cathode lamp, the optogalvanic signal was shifted 10–35 MHz from line center, due to an apparent drift of neutral atoms along the lamp axis.
High-power coherent surface-emitting antiguided diode laser arrays
Authors: Ou S. S. , Botez D. , Mawst L. J. , Jansen M. , Sergant M. , Roth T. J. , Yang J. J.
Published: July 2002

High-power coherent GaAs/GaAlAs surface-emitting antiguided laser arrays with dry etched micromirrors have been demonstrated for the first time. Both the deflecting 45° and 90° micromirrors were fabricated by ion beam etching. Twice diffraction-limited far-field beam profiles were obtained to pulsed output powers as high as 550 mW, with 220 mW in the central lobe.
1-kW, capacitively coupled radio frequency discharge excited CO laser with a closed-cycle fast axial flow
Authors: Sato Shunichi , Taniwaki Manabu
Published: July 2002

A capacitively coupled transverse radio frequency discharge has been successfully applied to excite a CO laser with a closed-cycle fast axial flow. The discharge and laser characteristics are described and the role of the O2 added to CO/N2/He mixtures is discussed. For a mixture of CO/N2/He/O2=7.5/12.5/80/0.8 an output of about 1 kW has been obtained at an entrance gas temperature of 160 K. Stable output with good beam quality has been demonstrated.
Room temperature damage removal from InP by optical pumping
Authors: Nakanishi Hideo , Kanada Mitsuka , Wada Kazumi
Published: July 2002

Removal of ion-implantation-induced damage in InP is observed to a considerable extent by optical pumping using argon ion laser irradiation at room temperature. The damage takes the form of recombination, scattering, and compensation centers, which were generated by Be implantation with dose of 1010–1012/cm2. We find that minority carrier injection by optical pumping is an attractive alternative to technologies based on a thermal annealing approach for the removal of these centers.
Photoassisted metalorganic molecular beam epitaxy of ZnSe
Authors: Coronado C. A. , Ho E. , Kolodziejski L. A. , Huber C. A.
Published: July 2002

Photoassisted heteroepitaxy of ZnSe on GaAs by metalorganic molecular beam epitaxy has been performed using sources of diethylselenium and diethylzinc. Illuminating the substrate during growth with an Ar ion laser has been observed to significantly enhance the growth rate. Growth rate enhancement was found to be a function of substrate temperature, VI/II gas flow ratio, and laser wavelength and intensity. Photons having energies sufficient to generate electron/hole pairs in the growing ZnSe film resulted in growth rate enhancement. The photoassisted growth has application for (i) increasing the anomalously low growth rate which is observed, (ii) assisting in tuning the surface stoichiometry, and (iii) providing for selective area epitaxy.
Injection mechanism at contacts in a quantum-well intersubband infrared detector
Authors: Rosencher E. , Luc F. , Bois Ph. , Delaitre S.
Published: July 2002

The role of the contact electrodes on the detection mechanisms in quantum-well photoconductors is usually overlooked. We show that these contacts may be blocking in a large temperature range. Upon illumination, the electric field is enhanced at the cathode electrode so that the injected current meets the quantum-well requirement. This mechanism is demonstrated in a single quantum-well photoconductor by the detailed study of the photocurrent over dark current ratios and by photocapacitance measurements.
Point source heating effects in multiple quantum well modulators
Authors: Sizer T. , LaMarche R. E. , Woodward T. K.
Published: July 2002

Multiple quantum well modulators have been proposed for use in photonic switching and optical interconnection systems. When used with the smallest devices and at competitive data rates, heating of the devices results. The heat is generated in a small volume coincident with the active optical area and alters the device parameters. In this letter we detail point source heating effects theoretically and experimentally in AlGaAs/GaAs and InGaAs/GaAs multiple quantum well modulators. These results indicate that when using small devices with small optical spots detrimental effects occur at average optical powers of less than 500 μW which limits the maximum data rate of optical systems.