bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation between background carrier concentration and x-ray linewidth for InGaAs/InP grown by vapor phase epitaxy
Authors: Macrander A. T. , Chu S. N. G. , Strege K. E. , Bloemeke A. F. , Johnston W. D.
Published: February 2003

The background carrier concentration of nominally undoped InGaAs/InP grown by the hydride process was found to correlate to the x-ray linewidth. A double crystal diffractometer was used to measure the mismatch parallel to the (100) surface as well as the more standard perpendicular mismatch. The epitaxial layers were, in general, found to be tetragonally distorted, and the linewidth was found to correlate to the parallel mismatch. Two regimes for the carrier concentration were identified, one for samples having no parallel mismatch and one for samples with parallel mismatch. In the latter case lattice defects which accommodated the misfit strain such as misfit dislocations are concluded to have been responsible for the carrier concentration.
Optical effective mass of high density carriers in silicon
Authors: van Driel H. M.
Published: February 2003

The optical effective masses of electrons and holes in silicon are calculated for carrier densities up to 2×1021 cm−3 and temperatures up to 3000 K. This evaluation, which is based on the band structure as determined by the local empirical pseudopotential method, indicates that the carrier masses for high density plasmas can be up to two times larger than the corresponding low density values. For electrons, this occurs primarily because of increasing warpage of the (low density) ellipsoidal constant energy surfaces with increasing energy, while for holes the effect is primarily due to nonparabolicity of the valence bands. Carrier-carrier interactions and carrier-lattice screening do not influence the effective masses significantly.
Bulk and transfer doping effects in AlxGa1−xAs layers grown on semi-insulating GaAs substrates
Authors: Nicholas R. J. , Brummell M. A. , Portal J. C. , Gregoris G. , Hersee S. , Duchemin J. P.
Published: February 2003

The observation of both bulk and two-dimensional conduction is reported in GaAlAs layers grown by metalorganic chemical vapor deposition on undoped semi-insulating GaAs substrates. The electron concentrations were determined from Shubnikov–de Haas periodicities in different magnetic field configurations. Bulk conduction is found to dominate at 4.2 K only after illumination with above band-gap light. This is interpreted as due to spatial transfer of some carriers with the GaAlAs layer.
Efficient AlGaAs shallow-homojunction solar cells
Authors: Gale R. P. , Fan John C. C. , Turner G. W. , Chapman R. L. , Pantano J. V.
Published: February 2003

Shallow-homojunction n+/p/p+ solar cells with one-sun, AM1 conversion efficiencies as high as 12.9% have been fabricated in Al0.2Ga0.8As epitaxial layers grown by organometallic chemical vapor deposition on single-crystal GaAs substrates. For these cells, which have n+ layers thinned by anodic oxidation to about 500 Å, the quantum efficiencies in the short-wavelength portion of the spectrum are as high as the best reported for AlGaAs cells with high band-gap window layers.
Selective counting of krypton atoms using resonance ionization spectroscopy
Authors: Chen C. H. , Kramer S. D. , Allman S. L. , Hurst G. S.
Published: February 2003

Resonance ionization spectroscopy (RIS) was used to count 1000 individual 81Kr atoms. In the method, lasers for RIS are used to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. After Z and A selection the krypton ions were counted as they were implanted into a target. Basically, the method works for any isotope whether stable or unstable. However, the detection limit may depend on the isotope because of outgassing of stable atoms from the enclosure walls. For 81Kr, we show that fewer than 1000 atoms can be counted with good accuracy.
Performance of Ta-Ta2O5-Au metal-insulator-metal devices
Authors: O’Clock George D. , Feisel Lyle D.
Published: February 2003

Conduction data for Ta-Ta2O5-Au metal-insulator-metal devices reveal a wide variety of different current-voltage characteristics for Ta2O5 metal-insulator-metal devices including negative resistance and symmetrical and asymmetrical diode characteristics. Devices with large cross-sectional areas tend to exhibit pronounced negative resistance characteristics. Electron emission data obtained with a 127° electron energy spectrometer indicate that the emission current is significantly affected by electron-electron scattering in the Au counterelectrode.
Structural dependence of percolation in germanium films
Authors: Gonzalez-Hernandez J. , Martin D. , Chao S. S. , Tsu R.
Published: February 2003

The critical volume fraction of percolation in conductivity has been determined for di-phasic Ge films. Unlike Si, two values were found, 0.15 and 0.4, corresponding respectively to low and high substrate temperatures. Furthermore, scanning electron microscopy revealed a random spherical growth for the former value as contrast to an essentially columnar growth for the latter. The higher and lower values are consistent with the theoretical limits for two- and three-dimensional percolation.
32×32 planar IR photovoltaic mosaic arrays on sputtered CdxHg1−xTe epilayers
Authors: Roussille R. , Amingual D. , Boch R. , Destefanis G. L. , Tissot J. L.
Published: February 2003

Epitaxial n-type CdxHg1−xTe layers on (111) CdTe substrates have been grown between 250 and 300 °C by sputtering deposition. The standard growth rate was nominally 2  μm/h for a thickness range from 10 to 30  μm. Typical electron concentration in CdxHg1−xTe layers with Cd composition of 0.34 is around of 2×1016 cm−3 with a Hall mobility of 20 000 cm2 V−1 s−1 at 77 K. Films can be converted to  p type after annealing. We report for the first time the characteristics of backside illuminated 32×32 planar photovoltaic mosaic arrays processed on sputtered layers. Hybrid structures have been fabricated and evaluated; the preliminary results indicate the suitability of these mosaics for hybrid focal plane applications.
Nitridization of gallium arsenide surfaces: Effects on diode leakage currents
Authors: Pearton S. J. , Haller E. E. , Elliot A. G.
Published: February 2003

Nitridization of GaAs surfaces by exposure to a nitrogen or nitrogen-hydrogen plasma is known to form a surface coating rich in GaN. We show that pretreatment in a hydrogen plasma at room temperature followed by production of this wider band-gap material by nitrogen plasma treatment at 500 °C for 5 h reduces the reverse leakage current of Au-GaAs (ND−NA =5×1017 cm−3) Schottky diodes by typically an order of magnitude at 300 K.
Picosecond relaxation of hot carriers in highly photoexcited bulk GaAs and GaAs-AlGaAs multiple quantum wells
Authors: Xu Z. Y. , Tang C. L.
Published: February 2003

The relaxation rate of hot carriers following picosecond photoexcitation in GaAs-AlGaAs multiple quantum well structures is found to be significantly slower than the corresponding rate for bulk GaAs under high excitations. This is confirmed by a detailed comparison of the hot-luminescence tails for the two cases using picosecond pulse and cw photoexcitations.
Stripe-geometry AlGaAs-GaAs quantum-well heterostructure lasers defined by impurity-induced layer disordering
Authors: Meehan K. , Brown J. M. , Holonyak N. , Burnham R. D. , Paoli T. L. , Streifer W.
Published: February 2003

Stripe-geometry AlGaAs-GaAs single quantum-well heterostructure lasers are demonstrated in which the region complementary to the stripe (outside of and defining the stripe) is shifted to higher band gap, and lower refractive index, by low-temperature (600 °C) Zn diffusion. Impurity-induced Al-Ga interdiffusion causes the single GaAs quantum well (x=0, Lz≊80 Å) outside of the stripe region to be mixed (‘‘absorbed,’’ x→x′) into the Alx′Ga1−x′As (x′∼0.3, Lz′≊0.18 μm) bulk-layer waveguide of the crystal.
Theoretical explanation of the absorptive optical bistability in semiconductors due to band-gap shrinkage
Authors: Schmidt H. E. , Haug H. , Koch S. W.
Published: February 2003

The creation of an electron-hole plasma in a semiconductor leads to a large band-gap shrinkage which can be used to obtain absorptive optical bistability caused by discontinuous jumps between states of weak band-tail absorption and states of strong band-edge absorption. These effects are described by rate equations for the photons and the free carriers. For CdS the calculated hysteresis phenomena are similar to the experimental results.
Selective excitation luminescence and electronic Raman scattering study of the 78-meV acceptor in GaAs
Authors: Hetzler S. R. , McGill T. C. , Hunter A. T.
Published: February 2003

We observe for the first time two excited states of the 78-meV acceptor in liquid encapsulated Czochralski GaAs with excitation energies of 62.9 and 66.9 meV above the ground state, respectively. These levels were observed in two different samples using selective excitation luminescence and electronic Raman scattering. We conclude that these levels could correspond to transitions from the 1s2 ground state to the split 1s12s1 excited state of a double acceptor.
Transport properties of selectively doped GaAs-(AlGa)As heterostructures grown by molecular beam epitaxy
Authors: Hwang J. C. M. , Kastalsky A. , Störmer H. L. , Keramidas V. G.
Published: February 2003

In selectively doped GaAs-(AlGa)As heterostructures the two-dimensional (2D) electron density is found to be monotonically decreasing with increasing separation (t0) between the mobile carriers and the doped (AlGa)As layer. A quantitative description of this t0 dependence requires the Si dopant to create a deep center in (Al0.3Ga0.7)As. For t0≳60 Å the low-temperature electron mobility, which can be as high as 1.6×106 cm2/Vs, does not show a correlation with t0. Unidentified and as yet uncontrollable impurities in the vicinity of the 2D system are a likely source for the residual electron scattering.
Fluxon threshold properties on a resistively coupled Josephson transmission line
Authors: Nitta J. , Matsuda A. , Kawakami T.
Published: February 2003

Fluxon threshold properties between transmission and nontransmission have been investigated with regard to a resistively coupled Josephson transmission line (RCJ). The RCJ consists of two Josephson transmission lines (JTL’s), which are Nb/Nb-oxide/Pb junctions, interconnected by an Au series resistor. Whether an incident fluxon transmits or not at the coupling resistor depends on the input pulse height and the bias current levels for the two JTL’s.
Thickness dependence of the switching time of the bistable boundary layer liquid crystal display
Authors: Thurston R. N. , Boyd G. D. , Senft Donna Cowell
Published: February 2003

The dc pulse duration TA needed to activate the unfavored state of the bistable boundary layer display has been measured as a function of pel thickness in a cell with a wedge shaped cross section. TA increases with cell thickness d in rough agreement with crude models based on the double layer and ion depletion mechanisms of switching. To achieve faster switching, one should make a thin cell with as little built-in asymmetry as possible, and create an interface with a strong double layer field whose Debye screening length is a signficant fraction of the cell thickness.
Optical properties of transparent and heat-reflecting indium tin oxide films: The role of ionized impurity scattering
Authors: Hamberg I. , Granqvist C. G.
Published: February 2003

The complex dynamical resistivity of high-quality transparent and heat-reflecting indium tin oxide films, prepared by reactive e-beam deposition, was evaluated from spectrophotometric measurements in the 0.25–50-μm wavelength range. These data are explained in detail from a theory encompassing scattering of free electrons by ionized impurities.
Optoelectronic properties of coupled cavity semiconductor lasers
Authors: Ebeling K. J. , Coldren L. A.
Published: February 2003

Differential voltage-current characteristics of coupled cavity semiconductor lasers are studied experimentally. Lasing thresholds of individual cavities, regions of single mode or multimode oscillation, or mode hop locations are easily obtained from the analysis. The optoelectronic properties can be used for monitoring operating states of the lasing system without requiring external optical elements.
Erbium silicide formation using a line-source electron beam
Authors: Knapp J. A. , Picraux S. T. , Wu C. S. , Lau S. S.
Published: February 2003

Rare-earth silicide layers typically are heavily pitted when formed by furnace reaction of thin metal films with a silicon substrate. We show that this phenomenon can be explained by an inhibiting contamination layer which has a high activation energy for dissolution relative to that for silicide growth. Very smooth erbium silicide growth has been demonstrated by reacting the layers at much higher temperatures (1100–1300 K) for 200–500 μs, using electron beam heating. A novel combination of controlled electron beam heating, ion beam analysis, and computational simulation has been used to determine an activation energy for interface barrier dissolution of 3.7±0.3 eV.
Direct measurement of optoacoustic induced ultrasonic waves
Authors: Kuo Chien-Yu , Patel C. K. N.
Published: February 2003

The two-beam optically induced photoacoustic grating and the subsequent low-frequency ultrasonic waves are measured with thin-film transducer in low concentration dye solution. The acoustic power generated is measured for a weakly absorbing medium to be ≊5 W/cm2 indicating high conversion efficiency. Application of this direct detection as a laser beam profiler is also discussed.
Thin organic films produced by ion implantation
Authors: Calcagno L. , Sheng K. L. , Torrisi L. , Foti G.
Published: February 2003

Ion bombardment of frozen benzene produces a polymeric film, the thickness of which can be controlled by changing the energy (30–100 keV) of the incoming helium beam. IR spectra and proton scattering analysis show that basic components of the film are hydrogen and carbon in the elemental ratio of about 3:1.
Hot-electron velocity overshoot in Ga0.47In0.53As
Authors: Ghosal A. , Chattopadhyay D. , Purkait N. N.
Published: February 2003

Velocity overshoot phenomena in Ga0.47In0.53As to the application of uniform electric fields are investigated using recent values of the material parameters. The effects of the ambient temperature and of the doping concentration are studied. The material is found to yield peak drift velocities larger than those in GaAs. The values of the peak velocity are greater for short lengths of the active region, low impurity concentration, and low ambient temperatures.
GaInAsP/InP heterostructure lasers emitting at 1.5 μm and grown by gas source molecular beam epitaxy
Authors: Panish Morton B. , Temkin Henryk
Published: February 2003

Double heterostructure and separate confinement heterostructure lasers of GaxIn1−xAs1−yPy lattice matched to InP and emitting at 1.5 μm have been grown by molecular beam epitaxy utilizing the decomposition of AsH3 and PH3 as a source of As2 and P2 molecules. Broad area lasers fabricated from the gas source molecular beam epitaxy (MBE) wafers had pulsed room-temperature threshold current densities (≊2000 A/cm2) and differential quantum efficiencies (17%–19%) that are comparable to state of the art 1.5-μm broad area lasers grown by other methods. The gas source MBE method appears to yield highly uniform material.
Anomalous laser penetration depths in multilayer planar targets
Authors: Ng A. , Pasini D. , Celliers P.
Published: February 2003

Anomalously large laser penetration depths in multilayer planar targets have been observed. Density dependence of the penetration depth also showed significant deviations from the theoretical scaling for laser-driven ablation. A simple model was proposed in which the ablation process was modified by an edge effect due to the small focal spot.
Observation of optical hysteresis in an all-optical passive ring cavity containing molecular gas
Authors: Harrison R. G. , Firth W. J. , Emshary C. A. , Al-Saidi I. A.
Published: February 2003

Dispersive optical hysteresis in an all optical passive unidirectional ring cavity containing a molecular gas has been observed. Ammonia is used as the nonlinear medium off resonantly excited on the aR(1,1) transition using temporally smooth 100-ns pulses from a transversely, excited, atmospheric pressure CO2 laser. Results are in excellent agreement with the theory of Ikeda recently generalized by the authors to describe period doubling in this system.
Study of the initial stages of growth of CdTe on (001)GaAs
Authors: Mar H. A. , Salansky N. , Chee K. T.
Published: February 2003

The initial stages of growth of CdTe on (001) GaAs have been studied using Auger electron spectroscopy and reflection high-energy electron techniques. At the growth temperature of 225 °C tellurium atoms are observed to be adsorbed to a thickness of one to two monolayers on a thermally cleaned GaAs substrate. However, cadmium atoms are adsorbed only when tellurium atoms are present. An analysis of the Auger electron spectra and the reflection high-energy electron diffraction patterns taken at intervals during the initial growth of CdTe films from a CdTe compound source indicates that growth takes place first by the deposition of one to two monolayers of tellurium. This is followed by the nucleation and growth of CdTe crystallites which increase in size and coalesce to form a single crystal of CdTe with a (111) CdTe ∥ (001) GaAs orientation.
Outdiffusion of Si through gold films: The effects of Si orientation, gold deposition techniques and rates, and annealing ambients
Authors: Chang Chin-An , Ottaviani G.
Published: February 2003

Outdiffusion of Si through thin gold films has been studied for (100) and (111) oriented Si wafers in different ambients. The gold films were deposited either by electron beam evaporation or by sputtering, each with two widely different rates. Using air annealings, higher outdiffusion rates of Si are observed for the Au/(100)Si samples than the corresponding Au/(111)Si ones for both deposition techniques, the difference being much more pronounced in the electron beam deposition case; samples with sputtering of gold all show higher outdiffusion rates of Si than their counterparts using the electron beam technique; higher deposition rates of gold also give rise to higher outdiffusion rates of Si, especially for the sputtering case. Similar effects of the Si orientation and gold deposition parameters have also been observed for the samples annealed in N2-O2 mixtures, but with much lower outdiffusion rates of Si than those annealed in air. Several mechanisms are suggested for the effects observed.
Electrical transport properties of CoSi2 and NiSi2 thin films
Authors: Hensel J. C. , Tung R. T. , Poate J. M. , Unterwald F. C.
Published: February 2003

Transport studies have been performed on thin films of CoSi2 and NiSi2 in the temperature range 1–300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room-temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiessen’s rule is obeyed over a remarkable range of bombardment doses.
Stabilization of n-type silicon photoanodes against photoanodic decomposition with thin films of polyacetylene
Authors: Simon Richard A. , Wrighton Mark S.
Published: February 2003

Photoelectrochemical cells based on polyacetylene coated n-Si photoanodes, n-Si/(CH)x, in 11 M LiCl solutions containing I−3/I− have been investigated. The n-Si/(CH)x photoanodes show a substantial improvement in durability compared to naked n-Si photoanodes. The efficiency of these photoelectrochemical cells appears to be limited by a low observed quantum yield for electron flow due to absorption of light by the electrolyte solution and by the (CH)x film. Overall efficiency of 1.9% of the conversion of 632.8-nm light (21 mW/cm2) can be sustained for >20 h without significant decline in efficiency. The n-Si/(CH)x photoanode immersed in I−3/I− media behaves as a Schottky barrier or metal-insulator-semiconductor structure where the (CH)x can be viewed as having a variable work function depending on the extent of doping. decomposition with thin films of polyacetylene
Monolayer surface doping of GaAs from a plated zinc source
Authors: Dobkin D. M. , Gibbons J. F.
Published: February 2003

We have investigated surface doping and diffusion of Zn in GaAs using rapid thermal processing. The use of an aqueous RuCl3 pretreatment has enabled us to electroplate uniform ≊100-Å-thick Zn layers directly on the GaAs surface. The excess Zn is removed with a 500 °C vacuum ‘‘evaporation,’’ leaving a modified surface layer which may serve as a dopant source for rapid thermal diffusion. Evaporation of A1 onto such surfaces yields Schottky diodes with enhanced barrier heights which have been used to fabricate metal-semiconductor field-effect transistor structures.
Single-longitudinal-mode GaAs/GaAlAs channeled-substrate lasers grown by molecular beam epitaxy
Authors: Wu Yao-Hwa , Werner Michael , Chen Kuo-Liang , Wang Shyh
Published: February 2003

We present here the first simple double-heterostructure channeled-substrate laser with lateral index guiding grown by molecular beam epitaxy. The channel is along [110] direction. The threshold current is 60 mA. Linear light-current relation and stable far-field patterns have been observed over the range of currents tested (from 60 to 160 mA). The lasers operate in single longitudinal mode over a wide range of current. The intensity ratio of the dominant mode and the neighboring mode is greater than 100:1.
Quantum well lasers tunable by long wavelength radiation
Authors: Gerck E. , Miranda L. C. M.
Published: February 2003

It is suggested that the lasing frequency of GaAs-GaAlAs quantum well lasers can be tuned when the quantum well structure is irradiated with a pulsed low-energy long-wavelength laser. This new tuning mechanism is based on the decrease of the electron binding energy, in the well, with increasing intensity of the external laser field. Typically, 0.60 mJ of 10.6-μm radiation in a 1-ns pulse may blue-shift the quantum well laser frequency by approximately 20 nm.
Increased optical damage resistance in lithium niobate
Authors: Bryan D. A. , Gerson Robert , Tomaschke H. E.
Published: February 2003

We have confirmed greatly improved resistance to photorefractive damage in compositions of lithium niobate containing 4.5 at. % MgO or more. Holographic diffraction measurements of photorefraction demonstrated that the improved performance is due to a hundredfold increase in the photoconductivity, rather than a decrease in the Glass current. The diffraction efficiency shows an Arrhenius dependence on temperature, with an activation energy of 0.1 eV for the damage-resistant compositions, compared with 0.5 eV for undoped or low-magnesium compositions. The damage-resistant compositions are distinguished by a 2.83-μm absorption line instead of the usual 2.87-μm line due to the OH-stretch vibration.
Effect of crystal orientation on shock initiation sensitivity of pentaerythritol tetranitrate explosive
Authors: Dick J. J.
Published: February 2003

Pentaerythritol tetranitrate single crystals were shocked in four different orientations with the shock direction parallel to the 〈110〉, 〈001〉, 〈101〉, or 〈100〉 crystallographic directions. Input stresses were 8.6 or 12.4 GPa. At 12.4 GPa detonation occurred in less than 10-mm run distance of the shock for the 〈110〉 and 〈001〉 orientations. For the 〈101〉 and 〈100〉 orientations, denotation was not observed. There is a difference of more than a factor of 2 in run distance to detonation with crystal orientation. The effect can be understood in terms of the available slip systems in the uniaxial strain associated with plane shock compression. In addition, an intermediate velocity transition was observed at 8.6-GPa shock stress for 〈101〉 orientation.
Study of defects in a rapidly degraded InGaAsP/InGaP double-heterostructure laser grown by liquid phase epitaxy
Authors: Ueda Osamu , Wakao Kiyohide , Yamaguchi Akio , Komiya Satoshi , Isozumi Shoji , Nishi Hiroshi , Umebu Itsuo
Published: February 2003

A rapidly degraded InGaAsP/InGaP double-heterostructure laser (λ=810 nm) grown on a (001) oriented GaAs substrate during cw operation at room temperature, is investigated by photoluminescence topography and transmission electron microscopy. Several 〈100〉 dark-line defects and 〈110〉 dark-line defects parallel to the stripe are observed in the photoluminescence image of the active region. The 〈100〉 dark-line defects are associated with classic interstitial type dislocation dipoles with Burgers vectors of the type a/2[101] 45° inclined to the junction plane. The 〈110〉 dark-line defect corresponds to a half-dislocation loop (b̄=a/2〈011〉) with many jogs (due to climb motion). In InGaAsP/InGaP material on GaAs, it is suggested that recombination enhanced defect motion (climb motion) can occur.
Stress in sputtered TaSix films on polycrystalline silicon
Authors: Draper Bruce L.
Published: February 2003

Stress in TaSix/polycrystalline silicon structures has been examined as a function of film composition, annealing conditions, and deposition parameters. It was found that although stress in as-deposited films is a strong function of these variables, annealed films exhibit a large tensile stress nearly independent of the parameters studied.
High resolution structural characterization of the amorphous-crystalline interface in Se+-implanted GaAs
Authors: Sands T. , Sadana D. K. , Gronsky R. , Washburn J.
Published: February 2003

High-resolution transmission electron microscopy is applied to the characterization of the amorphous-crystalline interface in (100) GaAs implanted at room temperature with Se+. The critical density of energy deposited by nuclear stopping is determined to be 11+2 eV per GaAs molecule. This critical energy density is shown to be defined most naturally by a 50% amorphous-50% crystalline criterion. The amorphous-crystalline transition region was found to have a distinct two-phase nature. Both stacking fault nuclei and channeled damage cascades were detected in the as-implanted material.
p-type doping in Si molecular beam epitaxy by coevaporation of boron
Authors: Kubiak R. A. A. , Leong W. Y. , Parker E. H. C.
Published: February 2003

High quality epitaxial (100) Si films prepared by molecular beam epitaxy have been doped p type by coevaporation of elemental boron. The sticking coefficient of B was found to be independent of growth temperature over the range 700–900 °C, and doping levels from 1×1015 to 7×1017 cm−3 have been achieved. Arbitrary doping profiles have been obtained by varying the power into the B furance.
Spectral distributions of photoquenching rate and multimetastable states for midgap electron traps (EL2 family) in GaAs
Authors: Taniguchi M. , Ikoma T.
Published: February 2003

Photocapacitance transients due to photoquenching have been measured to characterize midgap electron traps (the ‘‘EL2 family’’) in different GaAs wafers. The spectral distributions of photoquenching rates in liquid encapsulated Czochralski, vapor phase epitaxial, and oxygen-implanted liquid phase epitaxial GaAs were different to each other and also different from that in horizontal Bridgman-grown GaAs. From these results it is suggested that the EL2 family has multimetastable states and may consist of arsenic-atom aggregates.
Rapid thermal annealing characteristics of As+- and BF+2 -implanted Si
Authors: Kwor R. , Kwong D. L. , Yeo Y. K.
Published: February 2003

The electrical properties and distribution of impurities in As+- and BF+2 -implanted Si activated using rapid thermal annealing (RTA) are discussed. Sheet mobility and activation of the implanted Si 〈100〉 samples (As+: 60 keV, 1×1015 cm−2 and BF+2 : 45 keV, 1×1015 cm−2) as functions of annealing temperature are reported for RTA. Secondary ion mass spectroscopy atomic profiles of samples preannealed at 600 °C in furnace, followed by RTA are presented. Full electrical activation of As occurs at 1100 °C and that for B (BF2) occurs at 950 °C. A 600 °C, 1-h furnace preanneal does not have any noticeable effect on reducing the dopant redistribution during 2-s, 1170 °C RTA for 1×1015 cm−2 As+ implants and during 2-s, 1100 °C RTA for 1×1015 cm−2 BF+2 implants. This lack of ‘‘diffusion difference’’ is attributed to the high RTA temperatures at which mechanisms other than the point defects caused early time enhanced diffusion play a dominant role in impurity redistribution.
Various phase transitions and changes in surface morphology of crystalline silicon induced by 4–260-ps pulses of 1-μm radiation
Authors: Boyd Ian W. , Moss Steven C. , Boggess Thomas F. , Smirl Arthur L.
Published: February 2003

We report the first pulse width study of the various morphological changes and bulk phase transitions of single crystal silicon irradiated by 1-μm pulses of 4–260-ps duration. In particular, we find that amorphous silicon is formed from the melt contrary to published expectations, but only for pulse widths less than 10 ps. We also find that the single shot melting threshold is pulse width dependent. Additionally, we observe the growth of multishot damage and of periodic ripple patterns with pulses as short as 4 ps.
Cd1−xMnxTe-CdTe multilayers grown by molecular beam epitaxy
Authors: Bicknell R. N. , Yanka R. W. , Giles-Taylor N. C. , Blanks D. K. , Buckland E. L. , Schetzina J. F.
Published: February 2003

Single-crystal multilayers of the dilute magnetic semiconductor Cd1−x Mnx Te (x∼0.2) alternating with CdTe have been successfully grown for the first time using the molecular beam epitaxy technique. Four sets of superlattices have been prepared consisting of 14, 60, 90, and 240 double layers of average thickness 460, 140, 75, and 37 Å, respectively. Each set consists of two samples grown simultaneously using 7×15×1-mm thick (0001) sapphire substrates onto which 5.0-μm-thick CdTe buffer layers were first deposited. X-ray diffraction techniques were employed to verify that epitaxy had been achieved and to obtain the average lattice constant of each of the multilayer structures. X-ray diffraction satellites were observed on both sides of the (111) diffraction peak of the superlattices composed of 14 and 60 alternating layers, respectively, which allowed an accurate estimate of the superlattice period, or double-layer thickness, for these samples. Results of UV reflectance studies and photoluminescence experiments at liquid nitrogen temperatures are also presented and discussed.
Enhanced protection of GaAs against thermal surface degradation by encapsulated annealing in an arsine ambient
Authors: Campbell P. M. , Aina O. , Baliga B. J.
Published: February 2003

This letter reports a technique of encapsulated annealing in an arsine ambient which is shown to provide better surface protection for GaAs against thermal degradation than either encapsulation alone or capless annealing in arsine.
Femtosecond studies of intraband relaxation in GaAs, AlGaAs, and GaAs/AlGaAs multiple quantum well structures
Authors: Erskine D. J. , Taylor A. J. , Tang C. L.
Published: February 2003

Femtosecond intraband relaxation dynamics of hot carriers in highly excited states of GaAs, AlGaAs, and AlGaAs/GaAs multiple quantum well (MQW) structures are studied at room temperature using the equal-pulse correlation technique. Initial carrier lifetimes of 35, 60, and 50 fs are measured for GaAs, Al0.32Ga0.68As, and MQW structures for excitation with 2.02-eV photons at low carrier densities, and are in reasonable agreement with calculated scattering rates. The carrier-density dependence of these lifetimes is measured for densities in the range 1.5×1017–5×1019 cm−3.
GaAlAs buried multiquantum well lasers fabricated by diffusion-induced disordering
Authors: Fukuzawa Tadashi , Semura Shigeru , Saito Hiroshi , Ohta Tsuneaki , Uchida Yoko , Nakashima Hisao
Published: February 2003

A new transverse-mode-controlled laser called a buried multiquantum-well (BMQW) laser has been developed. In order to make it possible to bury the MQW laser active region utilizing the diffusion-induced disordering (DID) of GaAs-GaAlAs MQW, zinc was selectively diffused into the MQW structure, resulting in a 3–8-μm-wide stripe region. The threshold current is as low as 33 mA with a 300-μm cavity length and a fundamental transverse mode can be achieved. As a result of studying the relation of the waveguide geometry to the longitudinal and transverse modes it was concluded that this BMQW laser made by a simple DID process acts as an index-guided laser.
Localized plasma-density disturbance propagating along B in the interior of the ZT-40M reversed-field pinch
Authors: Nalesso Gianfranco , Jacobson Abram R.
Published: February 2003

Using a ten-chord interferometer, we have measured a field-aligned (k∥≊2 m−1; k⊥≳25 m−1) plasma-density disturbance propagating along B with a speed in the ion acoustic range. The propagation is purely in the electron drift direction and is observed only when the drift parameter (electron drift speed/electron thermal speed)≳0.1. A novel spatial-filter technique resolves this localized mode, which otherwise would be hidden by more robust global disturbances present along the lines of sight.
Demagnified projection printing by a new x-ray lithographic technique using no thin-film masks
Authors: Matsumura Hideki , Tanaka Takeshi
Published: February 2003

A new x-ray lithographic technique using no thin-film pattern masks is presented. A pattern image is projected by utilizing the total reflection of the x ray from a pattern plate, in which a pattern picture is drawn on a thick and hard substrate. The projected image is geometrically demagnified by the sine of incident angle of the x ray. And we actually succeeded in obtaining the demagnified line and space patterns of 1.9-μm width from the similar patterns of 210 μm by using copper Kα x ray.
Annealing behavior of light-induced defects in hydrogenated amorphous silicon alloys
Authors: Guha S. , Huang C. -Y. , Hudgens S. J.
Published: February 2003

We have studied the annealing behavior of light-induced changes in room-temperature photoconductivity and density of states at the Fermi level of hydrogenated amorphous silicon alloys for light soaking at temperatures between 100 to 400 K. Defects created at higher temperatures are found to be more difficult to anneal out. The results are discussed on the basis of the existing models for light-induced effect.
Crystallization temperature of ultrahigh vacuum deposited silicon films
Authors: Gonzalez-Hernandez J. , Martin D. , Chao S. S. , Tsu R.
Published: February 2003

We have investigated the dependence of the substrate temperature at which the transition from amorphous to polycrystalline state occurs, on the types of substrate, deposition conditions, and impurities. When crystallization is produced by annealing of an amorphous film already formed, the crystallization temperature is 600 °C when annealed under UHV, and higher when exposed to air prior to annealing. The increase is due to the necessity of out diffusion of trapped impurities introduced through the voids during exposure.
Air as an adjustable insulator for C-V and G-V analysis of semiconductor surfaces
Authors: Moreland John , Drucker Jeff , Hansma P. K. , Kotthaus Jörg P. , Adams Arnold , Kvaas R.
Published: February 2003

An adjustable metal-air-semiconductor capacitor was fabricated using a Pb disk suspended 1700–3600 Å above an n-type Si 〈111〉 surface. Experimental differential capacitance versus voltage and differential conductance versus voltage curves are similar to those previously obtained for metal-oxide-semiconductor capacitors.
CO2 laser assisted UV ablative photoetching of Kapton films
Authors: Koren Gad
Published: February 2003

The radiation produced by focusing an intense CO2 laser pulse on a tungsten target under vacuum was used for the direct dry photoetching of Kapton films. Typical etch rates of about 0.5 μm/pulse and surface smoothness with nonuniformities of the order of 1 μm were obtained by the simultaneous focusing of radiation on the Kapton target from the laser produced plasma (∼1.5 J/cm2) and the 10.6-μm scattered laser radiation (∼23 J/cm2). In contrast, no etching whatsoever was observed when the Kapton film was irradiated by each of the two sources separately (by the use of LiF and ZnSe filters) under the same experimental conditions. It is suggested that in the present experiment the extra energy absorbed by the Kapton film from the CO2 laser enables ablation of the UV sensitized layer close to the film’s surface.
Luminescence of carbon and oxygen related complexes in annealed silicon
Authors: Magnea N. , Lazrak A. , Pautrat J. L.
Published: February 2003

Efficient radiative defects are introduced in silicon by annealing at 450 °C. They are associated with very sharp and intense transitions at 0.926 eV (H line) and at 0.767 eV (P line). A close correlation has been established between the intensity of these lines and the oxygen content of the sample. The carbon content correlates also with the line H. It is shown that the radiation induced lines at 0.79 eV (C line) and at 0.97 eV (G line) are similarly influenced by the oxygen and carbon content. Although the detailed nature of the centers responsible for H and P lines is not known it can be put forward that their formation is controlled by Oi migration, and that the center leading to H must be similar to the G center (CSi–Sii−CSi).
Kinetics of the Staebler–Wronski effect in hydrogenated amorphous silicon
Authors: Stutzmann M. , Jackson W. B. , Tsai C. C.
Published: February 2003

We have investigated the time and intensity dependence of the creation process for light-induced metastable defects (Staebler–Wronski effect) in hydrogenated amorphous silicon (a-Si:H). The observed changes in electron spin resonance spin density (dangling bonds) and photoconductivity are consistent with a model which explains the Staebler–Wronski effect as a self-limiting process intrinsic to a-Si:H. A possible microscopic mechanism based on the nonradiative recombination of band tail carriers is discussed.
Observation of one-monolayer size fluctuations in a GaAs/GaAlAs superlattice
Authors: Deveaud B. , Emery J. Y. , Chomette A. , Lambert B. , Baudet M.
Published: February 2003

The observation of one-monolayer well size fluctuations in a superlattice is reported. Luminescence experiments show that several exciton peaks occur, each of them corresponding to a discrete well width differing by one monolayer from the next one. This attribution is confirmed by the intentional introduction of a larger well in the structure. It is also checked by comparison with the x-ray diffraction results that confirm the variations of the superlattice parameters observed in luminescence, and by photoluminescence excitation experiments that also show a splitting.
Light-induced electron spin resonance in a Langmuir–Blodgett film of pure merocyanine dye
Authors: Iwasaki Takashi , Wakabayashi Hisawo , Ishii Toshio , Iriyama Keiji
Published: February 2003

Light-induced electron spin resonance in a Langmuir-Blodgett film of pure merocyanine dye with a long hydrocarbon chain has been observed clearly for the first time. When monochromatic light was irradiated on the dye film, the intensity of the electron spin resonance signal grew twice as compared with the dark one without irradiation. Its lifetime was found to be about 15 min. Also the light-induced signal in a Langmuir-Blodgett film of diluted dye has been detected and its lifetime was about 30 min.
Identification of tellurium precipitates in cadmium telluride layers grown by molecular beam epitaxy
Authors: Chew N. G. , Cullis A. G. , Williams G. M.
Published: February 2003

The low-temperature growth of crystalline layers of CdTe on InSb substrates by molecular beam epitaxy has been investigated using transmission electron microscopy. It has been shown that while layers grown at substrate temperatures of ∼180–200 °C are generally single crystal and of good structural quality, layers grown at temperatures of ∼150 °C, although initially single crystal, rapidly become polycrystalline with increasing layer thickness. The mechanism responsible for this growth breakdown at low temperatures is shown to be the formation of second phase precipitates. These precipitates have been identified using diffraction analysis as the low-pressure, hexagonal phase of elemental Te.
Metalorganic growth of high-purity HgCdTe films
Authors: Hoke W. E. , Lemonias P. J. , Traczewski R.
Published: February 2003

Epitaxial films of HgCdTe have been grown by metalorganic chemical vapor deposition. Diethyltelluride, dimethylcadmium, and elemental mercury were used as the starting reagents. For Hg1−xCdxTe compositions with x≤0.2, the films are n type at 300 and 77 K. From Hall measurements at 77 K a minimum carrier concentration of 1.0×1015 cm−3 and maximum mobility of 590 000 cm2/Vs were measured. Epitaxial films with x≊0.3 were also grown. The films are n type at 300 K but exhibit p-type behavior at 77 K. p-type carrier concentrations less than 5×1015 cm−3 were attained.
Investigation of ionized impurity scattering in GaAs and InP using hydrostatic pressure
Authors: Lancefield D. , Adams A. R. , Gunney B. J.
Published: February 2003

The application of hydrostatic pressure to change the effective mass of conduction electrons has been used to investigate the electron scattering mechanisms in GaAs and InP over a wide range of impurity concentrations. It is observed that the Hall mobility decreases with increasing pressure and that, unexpectedly the effect increases with increasing impurity concentration. Analysis shows that, for pure material, good agreement is obtained between theory and experiment. However, for increased carrier concentrations this agreement is lost, indicating the incomplete nature of the standard theories of ionized impurity scattering. The discrepancy is tentatively associated with scattering from fluctuations in the correlated distribution of the ionized impurities which are taken here to be Gaussian in shape.
Below band-gap photoresponse of In1−xGaxP-GaAs heterojunctions
Authors: Hsieh S. Julie , Patten Elizabeth A. , Wolfe C. M.
Published: February 2003

Below band-gap photovoltaic response with a half-power point at 1.31 eV is observed in p-type In1−xGaxP on n-type GaAs heterojunctions with {111} interfaces. This response is apparently due to photon-assisted tunneling of carriers across the interfacial energy gap, which is smaller than the energy gaps of the constituent materials. The same mechanism can be employed in other heterojunctions with appropriate energy-band lineups to obtain longer wavelength infrared response.
Passivation of the GaAs surface by an amorphous phosphorus overlayer
Authors: Olego D. J. , Schachter R. , Baumann J. A.
Published: February 2003

We have investigated the effects of an amorphous phosphorus (P) overlayer on the intrinsic properties of the surface of n-GaAs by means of Raman and photoluminescence spectroscopy. We report a lowering of the surface barrier from 0.7 to 0.18 eV and a reduction of one order of magnitude in surface recombination velocity. These results indicate that the Fermi level is no longer pinned at midgap, but is moved closer to the conduction band. A model is proposed in which the P atoms at the interface reduce the number of As-missing lattice defects that pin the Fermi level at midgap in n-GaAs.
Optical bistability and hysteresis with a photorefractive self-pumped phase conjugate mirror
Authors: Kwong Sze-Keung , Cronin-Golomb Mark , Yariv Amnon
Published: February 2003

Bistability and hysteresis have been observed in a photorefractive passive phase conjugate mirror. A threshold basis for the effect is presented and the results of an experimental demonstration of the device are given.
Second harmonic generation in reflection from crystalline GaAs under intense picosecond laser irradiation
Authors: Malvezzi A. M. , Liu J. M. , Bloembergen N.
Published: February 2003

The emission of second harmonic radiation in reflection from crystalline GaAs irradiated with 20-ps, 530-nm laser pulses has been measured for incident laser fluences far exceeding the threshold fluence Fth for permanent reflectivity changes. The results are consistent with the occurrence of surface melting during the laser pulse. Detailed analysis of the second harmonic signals reveals an upper limit of 2 ps for the structural transition associated with the melting of the surface.
A new high-power, narrow-beam transverse-mode stabilized semiconductor laser at 1.5 μm: the heteroepitaxial ridge-overgrown laser
Authors: Tsang W. T. , Logan R. A.
Published: February 2003

We proposed and demonstrated the operation of a new laser structure: the heteroepitaxial ridge-overgrown (HRO) laser. The laser growth involves two epitaxial growths with ridge overgrowths through an oxide defined stripe to form the strip loaded waveguide of the laser with automatic alignment of the current confinement through the stripe. Characteristics of the 1.5-μm wavelength GaInAsP HRO lasers include high output powers of ∼50 mW/facet under pulsed operation and narrow beam divergence of ∼12° (half-power full width) operating in the fundamental transverse mode in the junction plane. The light-current characteristic is linear up to ∼30 mW/facet. The current threshold is as low as 70 mA. The external differential quantum efficiencies from both facets are 25%–35%. Because no reverse-biased pn junction was used for current injection confinement, very fast optical pulse response of 160 ps (half-power full width, detection limited) was obtained.
Phase-locked, index-guided multiple-stripe lasers with large refractive index differences
Authors: Suemune I. , Terashige T. , Yamanishi M.
Published: February 2003

Phase-locked operation of multiple-stripe lasers with refractive index differences on the order of 10−2 is reported. The higher order modes of each stripe are suppressed by the coherent coupling among the stripes, and the fundamental modes are selectively excited by the phase-locked operation. The light-current characteristics were linear up to 250-mW light output.
Influence of an electric field on beam-induced adhesion enhancement
Authors: Sai-Halasz G. A. , Gazecki G.
Published: February 2003

A new effect is described in beam-induced adhesion enhancement. The adhesion improvement caused by electron beam exposure of Al films on SiO2 is more pronounced, when, additional to the irradiation, a static electric field of either polarity is applied across the oxide. This effect helps clarify the mechanism of the recently discovered beam-induced adhesion of thin films to substrates. The influence of an electric field on the process provides evidence that the adhesion enhancement is dependent upon the arrival of nonthermal secondary excitations to the interface.