bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid isothermal annealing of As-, P-, and B-implanted silicon
Authors: Wilson S. R. , Paulson W. M. , Gregory R. B. , Hamdi A. H. , McDaniel F. D.
Published: February 2003

Single-crystal silicon wafers have been implanted with As, P, and B to doses of 1×1013–1×1016/cm2 and given a transient anneal using a Varian IA-200 Rapid Isothermal Annealer. The system uses infrared radiation to heat the wafers to temperatures in excess of 1000 °C for times on the order of 10 sec. Sheet resistance and Hall measurements have been used to determine the effect of the anneal on the electrical properties of the wafers. Rutherford backscattering and secondary ion mass spectroscopy have been used to measure lattice damage and dopant profiles before and after annealing. As and P are lost during the anneal unless the wafer is capped. Complete activation can be achieved with very little dopant diffusion. Residual damage is minimal in (100) oriented wafers that had been implanted with As. However, for (111) wafers damage is less in (111) wafers implanted to doses ≥5.0×1015/cm2, than in (111) wafers implanted to doses ≤5.0×1015/cm2. The diffusion of As during this transient anneal has been modeled using a concentration enhanced diffusion coefficient and the wafer temperature profile obtained from an optical pyrometer.
High spectral response and photoluminescence of AlxGa1−xAs solar cell structures grown by metalorganic chemical vapor deposition (0.28≤x≤0.53)
Authors: Ludowise M. J. , Dietze W. T.
Published: February 2003

Internal quantum efficiency (spectral response) data are presented for metalorganic chemical vapor deposition-grown AlxGa1−xAs (0.28≤x≤0.53) solar cell structures. Quantum efficiencies as high as 90% are obtained for x=0.28, falling to ∼45% for x=0.53. Electron diffusion lengths are derived from these data by fitting to theoretical predictions. Photoluminescence data on the samples are also presented showing strong intensity (comparable to GaAs) for 0.28≤x≤0.35. Degradation in performance above x=0.38 is attributed to increased deep level densities and direct-indirect band-edge crossover effects.
Magnetic cooling near Curie temperatures above 300 K
Authors: Oesterreicher H. , Parker F. T.
Published: February 2003

Selection of materials and expected magnetocaloric effects are discussed for magnetic cooling applications at elevated temperatures (400–800 K). Various considerations result in the selection of rare earth-transition metal compounds such as Sm2Fe17−xCox for this task. These materials offer a wide range of suitable magnetic ordering temperatures as a function of x. They also show relatively high effective magnetic moments per volume. Molecular field models are developed for analytically predicting entropy changes at and above the ordering temperature. Concomitant adiabatic cooling ΔT is accordingly computed for these compounds near the ordering temperatures. It is found that for a family of compounds ΔT values increase somewhat with increasing ordering temperatures due to the decreasing influence of the lattice heat capacity at higher temperatures. Adiabatic cooling of ΔT=−7.5 K at 70 kOe to ΔT=−9.2 K at 70 kOe is predicted for materials Y2Fe17−xCox near their Curie points of 300 and 600 K, respectively (corresponding to materials with x∼0.1 to x∼0.3). This compares with similar predictions for Gd of ΔT=−12.6 K at 70 kOe near 300 K. However, on a per volume basis, the isothermal heat pumping capacities TΔS at Ti=Tc for initial fields of 70 kOe are 7.5, 12.1, and 15.2 cal cm−3 for Gd (Ti =300 K), Y2Fe17−xCox, and Sm2Fe17−xCox (both at Ti =600 K), respectively. These intermetallics are, therefore, on a per volume basis, predicted to work over a range of temperatures with efficiencies higher than the efficiency of Gd near room temperature.
Photoluminescence in Si-implanted InP
Authors: Bhattacharya Pallab K. , Goodman William H. , Rao Mulpuri V.
Published: February 2003

Photoluminescence measurements at various temperatures and excitation intensities have been performed with Si-implanted InP (Fe) suitable for device applications. The implantation dose and energy of 28Si+ varied in the range (0.5–1.0)×1013 cm−3 and 100–200 keV, respectively. Post-implantation annealing was done at 670 and 700 °C with a proximity cap. The superior optical quality of the samples were evidenced by the strength of the bound exciton doublet centered at 1.414 eV in all samples and the appearance of the free-excitron-polaritron transition at 1.418 eV in the spectra of some samples at low temperatures. The dominant transition centered at 1.375 eV is ascribed to Zn impurities in the starting material. Analysis of temperature-dependent data yields an activation energy of 49.0 meV. The origin of a transition at 1.379 eV appearing in the unimplanted heat-treated samples is not clear. A new transition, whose emission intensity increases with the implant dose, appears in the implanted samples at 1.35 eV with an activation energy of 70.0 meV. We believe this is due to a complex defect involving Si. The 1−LO (longitudinal optical) phonon replica of the 1.375 eV transition is consistently seen in the spectra. The LO phonon energy obtained from our data is 44.0 meV. Luminescence is generally stronger for a post-implant anneal at 700 than at 670 °C. Bands ascribed to transitions involving Fe and Mn, or complexes involving these impurities, have been observed at 1.13 and 1.18 eV, respectively.
Electron-beam induced current characterization of back-surface field solar cells using a chopped scanning electron microscope beam
Authors: Luke Keung L. , Cheng Li-Jen
Published: February 2003

A chopped electron beam induced current (EBIC) technique for the characterization of back-surface field (BSF) solar cells is presented. It is shown that the effective recombination velocity of the low-high junction forming the back-surface field of BSF cells, in addition to the diffusion length and the surface recombination velocity of the surface perpendicular to both the p-n and low-high junctions, can be determined from the data provided by a single EBIC scan. The method for doing so is described and illustrated. Certain experimental considerations taken to enhance the quality of the EBIC data are also discussed.
Determination of trapped charge emission rates from nonexponential capacitance transients due to high trap densities in semiconductors
Authors: Wang Alex C. , Sah C. T.
Published: February 2003

Simple analytical expressions are derived to determine the trapped charge emission rates from the initial or final decay of capacitance transients in a semiconductor junction containing shallow dopants and traps of arbitrary profiles, even though the whole decay is nonexponential due to high trap densities. Two special cases of density profiles are then examined. ‘‘Nonexponentiality’’ is quantitatively defined and simple expressions are presented. We show that charging traps in part of the depletion layer may increase or reduce nonexponentiality, depending on the trap density in the region dynamically swept through during the transient. Measurements on a gold-doped diode give good agreeement with our analysis.
A comparison of gettering techniques for very large scale integration
Authors: Cerofolini G. F. , Polignano M. L.
Published: February 2003

Two techniques developed for metal-oxide-semiconductor (MOS) processing, internal gettering (IG) and silicon gettering by segregation, are compared. The test vehicles are n+/p junction diodes and are tested for their reverse current and defect density. The forward characteristic of these diodes is ideal over about six orders of magnitude with slope 60 mV/decade. No generation-recombination current affects the characteristic. Some diodes, though with an ideal forward characteristic, behave for reverse bias as I=I0+V/R, where I0 is the current extrapolated at V=0 and R is an apparent resistance. Taking into account that the width of the depletion layer is of the order of 1–3 μm, the ‘‘resistivity’’ responsible for the ‘‘resistance’’ R is of the order of 1011–1014 Ω cm, depending on the particular diode. The parameters I0 and R are correlated over about four orders of magnitude by the relationship 1/R∝I0−Idiff, where Idiff is the diffusion current determined by the forward characteristic. The ‘‘resistance’’ R depends to a slight extent on the thermal history of the diode, but mainly on the final anneal temperature. Ideal diodes are particular diodes with I0=Idiff.
The semiconductor-electrolyte junction: Physical parameters determination by photocurrent measurement throughout the Cd1−xZnxTe alloy series
Authors: Lemasson Philippe , Forveille-Boutry Annick , Triboulet Robert
Published: February 2003

p-type Cd1−xZnxTe alloys with 0<x≤1 are studied by photoelectrochemical technique. An electron diffusion length in the range 2–4 μm is measured which changes with x. This information together with the large and constant value of the Urbach’s slope of the absorption tail (∼125 eV−1) leads to the conclusion that the disorder in the alloys is slight in the whole composition range.
Discussion of the validity of Kuno’s relation to determine the base lifetime from a reverse recovery experiment
Authors: Jain Suresh C. , Van Overstraeten Roger J.
Published: February 2003

It is shown that Kuno’s modified relation ts/τeff =ln[1+(JF/JR)]+B, is valid for all diodes irrespective of whether or not heavy doping effects are important and whether the emitter and base thickness are small or large provided ts is large or JR/JF is small). The slope of the ts vs ln[1+(JF/JR)] straight line plot gives τeff. For a large base thickness, τeff≂τB. For a short base, 1/τeff=1/τB+1/t1, where t1 depends on the base thickness, the emitter properties, and the surface recombination velocity at the base contact. For small ts/τB, B is not constant anymore, and the ts vs ln[1+(JF/JR)] plot becomes curved in all cases. The effects of photoexcitation and of drift field in the quasineutral regions are also considered.
Unannealed and annealed depth distributions of mercury implanted into silicon
Authors: Wilson R. G. , Jamba D. M. , Hopkins C. G. , Norberg J. C.
Published: February 2003

We report unannealed and annealed depth distributions for Hg implanted into Si at energies of 300–900 keV and fluences from 1014 to 1016 cm−2. Range parameters and Pearson IV moments are determined; projected range and range straggle are about 40% greater than Lindhard, Scharff, and Schio/tt calculations. Significant redistribution of Hg atoms occurs with annealing, especially at 550 °C, and the nature of the redistribution varies with ion fluence, and appears to be related to amorphization and regrowth of the damaged layer.
Diffusion of arsenic in bilayer polycrystalline silicon films
Authors: Arienzo M. , Komem Y. , Michel A. E.
Published: February 2003

The diffusion of arsenic in polycrystalline silicon films is studied using a novel bilayer structure consisting of a polycrystalline silicon layer, in situ doped with arsenic, deposited on top of an undoped polycrystalline silicon layer. This technique avoids the complication of structural changes resulting from the ion implantation doping that has been employed in other investigations. The diffusivity is measured for the relatively low temperature range 700–850 °C and is described by the relation D=10 exp (−3.36/kT)cm2/s. The average deviation from this relation of the measurements from samples prepared in two different deposition systems is less than 20%. The values are about three orders of magnitude greater than the intrinsic diffusivity of arsenic in the silicon lattice. It is proposed that the diffusion takes place along grain boundaries and that certain background impurities in the grain boundaries are responsible for the large variation in the values that are reported in the literature.
Metal clusters in plasma polymerized matrices: Gold
Authors: Kay Eric , Hecq M.
Published: February 2003

This paper describes how plasma processes can control the metal content, metal cluster dispersion, and metal cluster crystallography embedded in dielectric fluorocarbon film matrices. We will show that the metal volume fraction can be controlled over a wide range by superimposing varying degrees of physical sputtering onto the chemical plasma etching/polymerization process which inevitably takes place simultaneously in certain halocarbon plasmas using a capacitively coupled rf diode discharge system. The critical metal volume fraction Vc at which the metal cluster containing polymer suddenly becomes conducting is 0.4. Evidence is given to show that the crystallographic features of the Au clusters (particle size, nonuniform strain, unit cell dimensions) have quite a different functional behavior vis-a-vis the overall film conductivity at different metal volume fractions depending on the deposition temperature in the range −15 to 60 °C. Furthermore, crystallographic features of the clusters are independent of the metal volume fraction in the film but depend on surface migration during film growth in the Teflon-like matrix.
Electron beam induced explosive crystallization of unsupported amorphous germanium thin films
Authors: Sharma R. K. , Bansal S. K. , Nath R. , Mehra R. M. , Bahadur Kanwar , Mall R. P. , Chaudhary K. L. , Garg C. L.
Published: February 2003

Explosive crystallization has been observed in thin, unsupported (free) films of amorphous germanium irradiated with a focussed, moderately intense electron beam. Transmission electron microscopic examination of the crystallized films show radial dendritic growth followed by annularly arranged periodic surface features. Analysis of our results confirm that the heat released during the amorphous to crystalline (a→c) transformation of the irradiated area (∼10 μm) abruptly crystallizes the surrounding area up to ∼120 μm in diameter. Origin of the dendritic growth is consistent with the ‘‘duplex-melting’’ model and confirms that the crystallization mechanism is self-sustaining and proceeds via an intermediate melting step. Periodic morphology in the outer crystalline area is characteristic of the present experiment on unsupported, amorphous films and is analyzed in terms of one-dimensional heat flow. A qualitative model is presented. The observed periodic surface features consisting of alternate large grain (∼1 μm wide) single crystalline and small grain (∼0.2 μm wide) polycrystalline regions in the outer crystallized area are understood in terms of melting and rapid solidification occurring in succession along the direction of propagation of the amorphous to crystalline transformation process. The presence of gaseous bubbles in the single crystalline area supports the existence of the melting step.
Degradation of native oxide passivated silicon photodiodes by repeated oxide bias
Authors: Verdebout J. , Booker R. L.
Published: February 2003

A thin, native oxide p-n photodiode was repeatedly subjected to combinations of negative and positive oxide bias in order to document on a larger scale the degradation noticed on a thicker-oxide photodiode used in a self-calibration procedure. The photodiode’s quantum efficiency (QE) decreased considerably during the course of the measurements but could be partially restored by exposure to steam or hydrogen. These and other results are discussed in terms of a simple model of the front p+ region that distinguishes the influences of interface recombination velocity and the induced surface electric field on the QE. According to the model, the observed decrease in QE implies an increase of several orders of magnitude in the recombination velocity at the oxide-silicon interface. Some experimental observations indicate that a change also occurs in the charge density at the Si-SiO2 interface.
A thermophonic investigation of threshold and memory switching phenomena in thick amorphous chalcogenide films
Authors: Kotz J. , Shaw M. P.
Published: February 2003

The behavior of amorphous chalcogenide switching and memory devices is examined for the first time in an experiment which measures the acoustic response of a thermophonic cell enclosing an electrically pulsed device. The experiments employ coplanar samples made of memory-type material. The cell response under single square-pulse excitation is measured and the results are analyzed using techniques developed by Aamodt and Murphy. In general, under all bias conditions, analysis of our results indicates that the sample cools immediately after the switching event occurs. Under low ON-state power conditions, a large jump in microphone signal occurs at the switching transition. This is attributed to the current discharge driven by the large external circuit capacitance. There is a gradual reduction in the mirroring of the capacitive discharge as the ON-state power level is increased, suggesting that the discharge energy is used as a heat of transformation for melting formed (crystalline) regions, as well as for heating the conducting path. For a memory event to occur it is necessary that the ON-state power be large enough to promote crystallization of the filament yet be low enough to avoid melting the conducting filament at the end of the pulse. In order to model the microphone signal and the temperature of the sample during switching, the analysis of Aamodt and Murphy is modified to allow for changes in the thermal conductivities of the sample and substrate. The post-switching volume is estimated using scanning electron microscopy, thereby allowing an estimation of the power density. The agreement between the experimental and computed curves is good.
Charge injection into SiO2 during field effect and photo-field-effect measurements in hydrogenated amorphous silicon
Authors: Vaid J. , Fritzsche H.
Published: February 2003

It is shown that electron and hole trapping in vitreous quartz occurs when fields larger than 105 V/cm are applied across the insulator of glow-discharge deposited amorphous silicon (a-Si:H) field effect devices. The trapping of charges of both polarities is enhanced by light having energy less than 2 eV. The charge trapping reduces the field effect and the photo-field-effect of a-Si:H at large gate voltages. It is found that strong illumination does not eliminate the effect of accumulation layers on the photoconductivity.
Conductivity of Si-ZnO p-n and n-n heterojunctions
Authors: Tansley T. L. , Owen S. J. T.
Published: February 2003

Heterojunctions have been prepared by the reactive rf, sputter deposition of n-ZnO on sputter-etched n- and p-type silicon substrates. Measurements of conductance show typical low-reverse breakdown at 18–25 V and forward currents of 2–10 mA at 3 V, both n-n and p-n diodes rectify. At low forward bias, 0–0.3 V, both types of diode have characteristics of the form I=I0[exp(qVA/βkT)−1] with large ideality factors β close to 5 for n-n and 7 for p-n junctions. In the range 0–100 °C β varies by only 15% in each case. Film series resistance predominates above 0.5 V with resistivities close to those measured transversely for films on insulating substrates. A model of highly doped ZnO crystallites with macroscopic mobility controlled by intergranular barriers is coupled with an interface state dominated junction band profile to account for these results.
Effect of uniaxial stress on optical gain in semiconductors
Authors: Dutta N. K.
Published: February 2003

It has been previously shown that the optical gain for impurity-band transitions is altered by stress and the results of that analysis have been used to explain the ‘‘anomalous’’ polarization characteristics of semiconductor lasers. However, in semiconductor lasers with undoped active layer the stimulated emission is observed at band-to-band transitions. The effect of uniaxial stress on optical gain for band-to-band transitions in direct gap semiconductors is calculated in this paper. The optical gain for linearly polarized light with electric vector along the stress is found to be larger than that for light polarized normal to the stress even in the absence of impurities. This arises from the stress-induced anisotropy of the band-edge effective masses. The result shows that in semiconductor injection lasers, the optical gain for the TM mode (E normal to the junction) is larger than that of the TE mode (E along the junction) in the presence of a sufficient compressive stress normal to the junction. The stimulated emission from injection lasers is usually polarized in the TE mode, which has higher facet reflectivity than that of the TM mode. Thus the observation of stimulated TM emission implies higher TM gain and hence suggests the presence of compressive stress.
Relationship of the structure of the pseudobinary Laves phase compounds Sm-Er-Fe to their intrinsic magnetostriction
Authors: Tai Li-Chi
Published: February 2003

A series of pseudo-binary Laves phase compounds Sm1−xErxFe2 (x=0.1, 0.2...0.85) have been prepared and investigated. Using the method of x-ray diffractometry, the samples are step scanned with monochromatic Cu radiation at Bragg angle 2θ ranging from 50° to 110°. A detailed report is presented here on the broadening and splitting of the line profiles in some specimens at higher Bragg angles, like the cubic (533), (622), (642), and (731) reflections. The results are discussed in connection with the intrinsic magnetostriction of the material. The Curie temperatures and the room temperature saturation magnetization of the compounds have also been studied.
Nonlinear optical reorientation in hybrid aligned nematics
Authors: Barbero G. , Simoni F. , Aiello P.
Published: February 2003

We give the complete theory of optically induced molecular reorientation in hybrid aligned nematic liquid crystals in which all the approximations usually adopted can be dropped. Applying a very general variational method of calculation and taking into account the anchoring energies on the boundaries of the liquid crystal cell we obtain a phase diagram (thickness versus optical field) exhibiting the possibility of ordered phase transitions from homeotropic to hybrid to planar configurations. Then we get the field dependent dielectric constant 〈δε〉 for any field strength and work out, as well, some numerical examples. In particular we show the previously assumed quadratic dependence on the field is true only at very low fields while a saturation occurs increasing the field. For larger sample thicknesses the saturation occurs at fields much lower than those necessary for the transition to a planar order. Finally we show that our analysis can be applied to the study of optical Fredericksz transitions in nematics and we work out a more general expression for the Fredericksz threshold.
Lateral charge spreading-induced effects within a shallow junction bipolar technology
Authors: Hemmert R. S. , Pan L. S. , Altieri J. , Walsh J. P.
Published: February 2003

Time-dependent lateral charge separation along a dielectric interface can induce parasitic Field-Effect Transistor (FET) leakage within integrated circuits. For the bipolar technology investigated, physical analysis techniques revealed that lateral charge separation occurred along the silicon nitride-to-sputtered quartz interface. The induced parasitic-FET leakage in the silicon was observed using electron beam-induced current techniques. The parasitic-FET leakage can be prevented by either a field shield or a guardring. The lateral charge separation that occurred along the thermal oxide-to-silicon nitride interface did not induce parasitic-FET leakage but lead to an increase in the common-emitter current gain of the lateral-PNP transistor. This instability was eliminated by depositing a phosphosilicate glass layer on top of the thermal oxide. Evidence that eliminated hot carrier injection as the origin of the parasitic-FET leakage is presented. Process and layout effects on the parasitic-FET leakage were also investigated.
Electrical resistivity of AuIn2 thin films at 4.2 K
Authors: Hasumi Yuji , Arai Kunihiro , Waho Takao , Yanagawa Fumihiko
Published: February 2003

Electrical resistivity and grain size of AuIn2 thin films, which are used as resistors in Pb-alloy Josephson integrated circuits, were investigated as a function of film thickness, substrate temperature, and pressure during deposition and annealing time. The effect of grain boundary on film resistivity was estimated and the dominant scattering mechanism was determined. The resistivity at 4.2 K is 2–15 μΩ cm for 40–100-nm film thickness and 30–190-nm grain size. Based on the Mayadas–Shatzkes grain boundary scattering theory, the resistivity is calculated from the observed grain size. The calculated resistivity agrees well with the experimentally determined resistivity, showing that grain boundary scattering is the dominant scattering mechanism. It was also concluded that either the grain boundary reflection coefficient of AuIn2 film is notably high (≳0.5) or the carrier concentration would be about ×10−1 small, compared with other metals.
Comment on ‘‘Current limits in linear accelerators’’
Authors: Winterberg F.
Published: February 2003

The paper by Reiser [J. Appl. Phys. 52, 555 (1981)], generalizing existing formulas for the current limitations in linear accelerators by inclusion of longitudinal motion within the bunch, omits magnetic forces acting in the longitudinal direction which can become larger than the electrostatic forces. These magnetic forces result from the Lorentz-transformed externally applied radial electric fields to the frame of the bunch.
Aging characteristics of 1.65-μm InGaAs/InP buried heterostructure lasers grown by molecular-beam and liquid phase epitaxy
Authors: Asahi H. , Fukuda M. , Kawamura Y. , Noguchi Y. , Nagai H. , Takahei K.
Published: February 2003

Room temperature aging tests have been carried out on molecular beam epitaxially grown InGaAs/InP BH (buried heterostructure) lasers with LPE (liquid phase epitaxy) InP burying layers and LPE-grown InGaAs/InP BH lasers. Both types of lasers have operated continuously at room temperature in air for more than 8000 h at 4–8 mW/facet, and are still operating stably. Except for slight changes in the threshold currents at an early stage of the aging test, these lasers did not show noticeable change in the longitudinal mode, far field pattern, and light output response under pulsed operation before and after aging.
Spectral measurements and analysis of beam-gas emissions
Authors: Chong Y. P. , Yu S. S. , Fessenden T. J. , Masamitsu J. A. , Frank A. M. , Prono D. S.
Published: February 2003

Spectral emissions of the Experimental Test Accelerator beam in 500-Torr synthetic air have been measured in the wavelength range 250–700 nm for beam currents of 4.5 and 8 kA. Intense emissions are identified as radiation from nitrogen. Relative intensities agree well with Franck–Condon factors. Wet air results in a dramatic decrease (by a factor of 2–3) in intensity over the scanned range. This effect is presently attributed to increased hose motion. Near 700 nm, emissions that are not observed in dry air, are identified as emanating from water vapor, nitric oxide, and oxygen. The pressure dependence of emitted intensities at 337.1 and 391.4 nm were measured from 80 μ to 500 Torr of nitrogen as well as dry synthetic air. Results obtained for an 8-kA beam are not explained by a time-dependent Boltzmann air chemistry code which predicted very well previous measurements for a 1–kA beam.
On penetration of electromagnetic fields into nonlinear conducting ferromagnetic media
Authors: Mayergoyz I. D. , Abdel-Kader F. M. , Emad F. P.
Published: February 2003

The penetration of plane electromagnetic waves into a ferromagnetic conducting half-space is analytically investigated. The model used for the permeability is based on a ‘‘nth root approximation’’ for magnetization curve (B=KH1/n,n>1) and does not include hysteresis. In the case of circular polarization of electromagnetic waves, the exact analytical solutions of the nonlinear differential equations are given. Here an interesting effect appears: the solutions are marked by the absence of higher-order harmonics everywhere within the medium, despite its nonlinear magnetic properties. The case of noncircular polarization of electromagnetic waves is treated as a perturbation of circular polarization. Linear equations for perturbations are then derived and their analytical solutions are found for the cases of elliptical polarizations of magnetic and electric fields, respectively. The results of calculations of surface impedances and third order harmonics of electromagnetic fields are presented. The accuracy of the perturbation technique is tested by the application of this technique to the case of circular polarization for which exact analytical solutions are available.
Variational finite element solution of electromagnetic wave propagation in a one-dimensional inhomogeneous anisotropic medium
Authors: Jeng Shyh-Kang , Chen Chun Hsiung
Published: February 2003

The variational finite element method is applied to tackle the electromagnetic wave propagation problem in the presence of anisotropy and one-dimensional inhomogeneity. The problem is first formulated to a variational equation through a new approach based on the induction theorem, reactions, and reciprocity. The obtained variational equation is then solved via the finite element method. Numerical results for the problem of wave normally incident upon a stratified magnetoplasma are also included.
One-dimensional numerical simulation of a free electron laser-storage ring system
Authors: Luccio A. , Pellegrini C.
Published: February 2003

A numerical simulation of a free electron laser oscillator-storage ring system is presented. The model describes the evolution of the system toward a steady state and gives information on the changes of the laser power and of the electron and photon pulse shape during the transient. The steady-state laser power output and electron beam properties are compared with the existing theoretical model.
Effect of lateral energy transport on ion expansion energy scaling in laser-produced plasmas
Authors: Pant H. C. , Sharma S. , Shirsat T.
Published: February 2003

Polythene targets have been irradiated at a maximum flux of 1014 W/cm2 with a focused Nd:glass laser. Spatial extent of the lateral energy transport as a function of the incident laser intensity has been determined using pinhole camera imaging with 12-μm spatial resolution. The effect of lateral energy transport on the plasma expansion energy scaling has been investigated. The scaling is significantly affected at higher intensities for a smaller irradiation spot.
Effect of recombination on ion expansion velocity in laser-produced plasmas
Authors: Gupta P. D. , Naik P. A. , Pant H. C.
Published: February 2003

A study of the ion expansion characteristics in plasmas created from carbon, copper, and gold targets using a 1-GW, 5-ns neodymium glass laser is presented. The ion expansion velocity is found to vary with the distance of the probe from the target and the variation is observed to be different for low and high atomic number (Z) targets. Analysis shows that the strikingly different variation for low and high Z targets is a manifestation of their different recombination characteristics during plasma expansion.
Measurement of anode falls and anode heat transfer in atmospheric pressure high intensity arcs
Authors: Sanders N. A. , Pfender E.
Published: February 2003

Electric probe measurements have been performed at and close to a plane, water-cooled anode surface in atmospheric pressure, high intensity argon arcs for different arc configurations which in turn, result in two distinctly different anode arc roots (diffuse and constricted). An adjustable fine wire probe penetrating through a small hole in the center of a flat anode allows for potential and electron temperature measurements in the anode boundary layer. For the parameter range covered by this investigation (100 A≤I≤250 A) the results reveal negative anode falls ranging from approximately −2.1 to −1.4 V. Electron temperatures at the anode surface range from 8800 to 9800 K. Calorimetric energy balances from which the contributions of the various modes of heat transfer to the anode may be derived, indicate the importance of convective heat transfer to the anode. The results of the calorimetric studies as well as of the anode fall measurements are consistent with a revised anode heat transfer model which takes negative anode falls into account.
Evaporative antimony doping of silicon during molecular beam epitaxial growth
Authors: Metzger R. A. , Allen F. G.
Published: February 2003

At T>700 °C Sb desorbs from the Si(111) surface at a rate KDNDS and incorporates in the growing surface (1.15 Å/sec) at a rate KINDS where KD =1.5×109 exp(−2.46/kT), KI =7.45×10−5 exp(−0.41/kT), and NDS is the Sb surface concentration cm−2. The sticking coefficient for Sb S=KI/KD =4.9×10−14 exp(2.05/kT), ranging from 10−3 at 700 °C to 3×10−5 at 850 °C. Transient time τ=K−1D ranges from 10 sec at 980 °C to 105 sec at 600 °C. Sharp, well-controlled doping profiles result for T>750 °C and bulk mobility is achieved up to ND ∼3×1018 cm−3.ND levels >1017 cm−3 require multimonolayer equivalent Sb coverage, but Si surface area appears to increase to provide Si-Sb bonding for all Sb atoms. For T<650 °C KI increases and S∼unity at 600 °C.
Identification of donors in vapor grown indium phosphide
Authors: Dean P. J. , Skolnick M. S. , Taylor L. L.
Published: February 2003

We report well resolved substructure in the ‘‘two electron’’ satellite (TES) near band-gap photoluminescence (PL) of excitons bound to shallow donors in InP, observable in high magnetic fields above ∼3 T. This substructure arises from differences in the central cell corrections to the binding energies of different donor species, resolved here for the first time in PL spectra for InP. Six different donor species are differentiated in undoped vapor phase epitaxial (VPE) layers. The two most persistent contaminants are identified with S and Si from back-doped crystals which yield useful data for uncompensated donor concentrations up to ∼5×1015 cm−3 at ∼9.5 T. The most important donor contaminant in refined halide transport VPE InP is S, but Si is dominant in layers grown with metalorganic sources of In. The TES identifications are supported by similar substructure with appropriately reduced splittings in the ionized donor BE PL. A profile of the Si/S donor concentration ratio as a function of layer thickness is presented, and the ‘‘mole-fraction’’ technique is shown to control the relative proportion of Si donors.
A heuristic approach to steady-state semiconductor filament theory, with applications
Authors: Chen Yueh-Hsin , Lindholm Fredrik A.
Published: February 2003

We present a heuristic approach for solving the current-voltage characteristic of a semiconductor filament in the steady state excited by a time-independent and space-independent carrier density injected at the front surface. The treatment assumes a model having infinite surface recombination velocity (zero excess carrier density) on the lateral surfaces, a model used by previous workers for both transient and steady-state conditions. For the steady state, we demonstrate that the exact solution for total current crossing the injecting face diverges. Use of partial sums derived from truncating the Fourier or Bessel-function series of the periodic extension in space of the constant carrier density on the injecting face yields closed-form analytic solutions for the current-voltage characteristic. From these solutions, a definition of the effective filament lifetime emerges. Its dependence on lateral dimensions nearly agrees with the dependence of the transient filament lifetime defined by Shockley. The approach advanced here enables treatment of several semiconductor devices containing grain boundaries, including one in which the model employing infinite surface recombination velocity admits use of the superposition principle to build a total solution by summing more elementary solutions. A partial justification for the heuristic approach taken here derives from regarding the partial-sum approximation as a means of moving the model in the direction toward a physically realizable system. Brief discussion appears of electrostatic and thermal analogs of the semiconductor boundary-value problem treated.
Inversion layer solar cells on chemically vapor-deposited polycrystalline silicon thin films
Authors: Burte E. P. , Hezel R.
Published: February 2003

It is demonstrated that the metal-insulator-semiconductor (MIS) inversion layer (IL) process is also suited to fabricating solar cells on fine-grained polycrystalline silicon thin films prepared by low-pressure chemical-vapor deposition (LPCVD). Plasma enhanced silicon nitride was used as dielectric to create a highly conductive inversion layer at the silicon surface. As revealed by high frequency and quasistatic C-V measurements, the insulator/semiconductor interface for fine-grained LPCVD polycrystalline silicon is similar to that for the coarse-grained Wacker Silso material. An excellent external quantum efficiency in the short wavelength region was obtained for solar cells on both materials. For the 1-cm2 solar cell on 2-Ω cm p-doped LPCVD silicon an active area efficiency of ηa=1.8% was obtained. Ways of improving these cells are suggested. A total area AM1 efficiency of 13% was achieved for coprocessed 4-cm2 MIS-IL solar cells on Wacker Silso.
Redistribution of current in flat conductors using magnetic bars
Authors: Hussein A. M. , Biringer P. P.
Published: February 2003

Current carrying conductors, partially covered with magnetic materials, exhibit interesting properties and have a number of possible applications. This paper investigates the very noticeable change in the current distribution in flat conductors when using rectangular magnetic bars close to their surfaces. The current tends to concentrate at the air gaps between the magnetic bars. The theoretical solution is obtained by separation of variables. The effect of different parameters on the current distribution and conductor impedance is determined. Different approximations are compared with the exact solution.
Influence of illumination on the grain boundary recombination velocity in silicon
Authors: Oualid J. , Singal C. M. , Dugas J. , Crest J. P. , Amzil H.
Published: February 2003

The variation with illumination of the grain boundary (GB) barrier height EB and of the effective recombination velocity Seff is calculated by means of a self-consistent procedure which takes into account the bending of the minority carrier quasi-Fermi level in the GB space-charge region and in the GB quasi-neutral region. The GB interface states have been assumed to be uniformly distributed in a half-filled band whose width and position in the band gap can vary. Seff is nearly proportional to exp(EB/kT), only when EB is sufficiently low. For high EB, Seff is limited by the thermal velocity. The influence of the density of interface states and the grain doping concentration has been studied. The experimental results obtained with Silso–Wacker polycrystalline silicon show that the grain boundaries present different behaviors.
The diffusion of phosphorus in silicon from high surface concentrations
Authors: Schaake H. F.
Published: February 2003

The anomalous diffusion of phosphorus into silicon from high surface concentrations is quantitatively considered in a model in which, as phosphorus diffuses into the solid, silicon diffuses out to make way for the substitutional phosphorus. As a result, a high concentration of interstitials is established in the bulk, resulting in the emitter dip effect and enhanced diffusion of the phosphorus in the bulk. The gradient of interstitials created near the surface by this process leads to a retardation in the diffusion process near the surface. Predictions of this model are compared with experimental diffusion profiles, and found to be in good agreement.
Hydrogenation of gold-related levels in silicon by electrolytic doping
Authors: Pearton S. J. , Hansen W. L. , Haller E. E. , Kahn J. M.
Published: February 2003

The deep gold-related donor and acceptor levels in silicon have been neutralized to several  μm depth by introducing atomic hydrogen using an electrolytic method. Using phosphoric or sulfuric acid as the electrolyte, it is possible to dope the crystalline silicon with hydrogen at elevated temperatures (200–280 °C) allowing direct comparison with other means of introduction, such as hydrogen plasma exposure. We find the electrolytic method is not as efficient as plasma treatment for the same conditions, possibly due to oxide formation during the immersion in the acid.
Analytical approximate model of the potential distributions in semiconductor samples having a nondegenerate surface accumulation layer
Authors: Ruan Ying-Chao , Tang Jing-Qing
Published: February 2003

A satisfactory analytical approximate model of the potential distribution (u) in a semiconductor sample having a nondegenerate surface accumulation layer possessing an arbitrary surface potential and a constant impurity concentration N≳5×101 ni has been obtained by means of joining the two different approximate expansions of the electrical field in terms of ue−u for large values of u and in terms of u for small values of u. The approximation deviates from the numerical solution by less than 1% through the whole sample.
Low temperature pyroelectric properties of α-LiIO3 single crystals
Authors: Bhalla A. S.
Published: February 2003

Pyroelectric properties of α-LiIO3 in the temperature range between 320 and 120 K are measured. It is found that α-LiIO3 has low dielectric constant, low tan δ, and useful pyroelectric properties at low temperature about 125 K. The primary and secondary pyroelectric contributions at 253 K are estimated.
Direct photochemical deposition of SiO2 from the Si2H6+O2 system
Authors: Mishima Y. , Hirose M. , Osaka Y. , Ashida Y.
Published: February 2003

Silicon dioxide films have been prepared by the direct photolysis of disilane with oxygen at temperatures as low as 150 °C. The photochemical deposition rate at temperatures below 300 °C has an activation energy of 0.53 eV, which is appreciably lower than the activation energy of 0.96 eV obtained for the thermal chemical vapor deposition (CVD). The infrared absorption peaks due to the SiH and SiOSi stretching modes in the photo-CVD SiO2 matrix always appear at higher wave numbers than those in thermal CVD films. This is interpreted in terms of the densification of the SiO2 network through photochemical reactions.
Effect of ion bombardment on the efficiency of amorphous hydrogenated silicon solar cells
Authors: Premachandran V. , Bapat D. R. , Narasimhan K. L.
Published: February 2003

The effect of low energy ion bombardment on the series resistance, open circuit voltage, and short circuit current is investigated for hydrogen, helium, and nitrogen ions. In addition to mechanical damage, hydrogen and nitrogen also create damage due to chemical effects.
Domain-wall tension allows bistability in imperfect laminar cholesteric twist cells
Authors: Berreman Dwight W.
Published: February 2003

Tension in domain walls between adjacent regions of opposite state in bistable laminar cholesteric twist cells can prevent growth of very small domains. This fact makes permanent bistability possible even when dust particles are available to nucleate the unwanted state. A crude model of a wall yields an approximate relation between allowable variation of cell thickness or of holding voltage and the maximum allowable size of dust particles or similar imperfections. If imperfections are smaller than this maximum a picture element can remain in either state indefinitely.
The influence of growth conditions on selenium incorporation in GaAs grown by molecular beam epitaxy
Authors: Andrews D. A. , Kong M. Y. , Heckingbottom R. , Davies G. J.
Published: February 2003

An electrochemical cell Pt/Ag/AgI/Ag2Se/Pt has been used as a highly controllable source of Se2 for n-type doping of GaAs grown by molecular beam epitaxy (MBE). Se is incorporated with 100% efficiency under all normal MBE conditions up to growth temperatures of 620 °C. Above this temperature doping is still possible but with reduced efficiency. The general behavior is similar to that already reported for sulfur doping, with the added advantage that doping can be extended to temperatures some 30 °C higher in the case of Se. Chemical analysis has confirmed that when doping efficiency is reduced, it is due to actual loss of Se. Thermodynamic analysis indicates that loss as Ga2Se is to be expected under all conditions studied, so successful doping is due to kinetic barriers to this loss reaction. Excess As4 is shown to hinder the loss of Ga2Se even further.
Effects of keV electron irradiation on optical generation of hole traps in thermal oxide on silicon
Authors: Tzou Joseph Jengtao , Sun Jack Yuan-Chen , Sah Chih-Tang
Published: February 2003

Experimental results are presented which show the generation of several neutral oxide hole traps by keV electron irradiation. The density of the existing hole trap increases by about a factor of 2 after 4-keV electron irradiation. The added traps appear to be associated with broken silicon-oxygen bonds by the keV electrons. A new oxide hole trap of cross section of 1.4×10−15 cm2 is also observed in dry oxides with post-oxidation anneal in argon and post-metallization anneal in forming gas. This new hole trap may be related to an oxygen deficient or hydrogen-bond center. Heating at 370 °C anneals out the new hole trap but it does not restore the broken bonds.
Stress relaxation in unirradiated and in helium ion bombarded glass plates: Dimensional stability
Authors: Primak William
Published: February 2003

The deformation of thin glass plates during bombardment with 140-keV He+ ions was measured with an external capacitor. The contour of the plates was determined interferometrically before irradiation, after irradiation, and after aging for several years. These results showed that the calibration of the capacitor equipment by dead-weight loading a silica plate was faulty. The deflection of a vitreous silica free cantilever on dead-weight loading was measured interferometrically, and the results showed that deformation occurred within the clamp. It was confirmed that placing a ground shield about the electrode of the capacitor increases the calculated deflections. Data for the permanent deformation of a stressed plate of vitreous silica are analyzed, and it is concluded that stress relaxation by a bulk viscoelastic deformation cannot be detected by a change in plate contour because the maximum precision for such a determination could not detect apparent viscosities greater than ∼1029 P. The stress relaxation of the irradiated vitreous silica plates was about 10% in three years corresponding to an apparent post-irradiation viscosity of ∼1020 P. The stress relaxations observed for the other glasses, Pyrex, BK7, and LF2 were much greater, and it is uncertain to what extent they were a viscoelastic effect or an annealing effect. The behavior of a sample of a facsimile radioactive waste storage glass, 76–68 indicated it was not a uniform product; the contour became irregular; hence, these techniques were not appropriate for it.
A low-temperature process for annealing extremely shallow As+-implanted n+/p junctions in silicon
Authors: Singh Ranbir , Fonash S. J. , Rohatgi A. , Choudhury P. Rai , Gigante J.
Published: February 2003

A new low-temperature process that anneals out ion-implantation damage and activates the dopant in extremely shallow, implanted n+/p structures is presented. This technique employs low-energy (0.4 keV) H+ ion implantation following arsenic ion implantation and then a subsequent low-temperature (500–600 °C) furnace anneal. Very little dopant redistribution takes place with this new process and the device characteristics are comparable to other processes employing short-time, higher-temperature anneals.
Channeling studies of deuterium: Defect interactions in vanadium
Authors: Danielou R. , Fontenille J. , Ligeon E. , Fukai Yuh
Published: February 2003

The lattice location of deuterium absorbed (VD0.008) or implanted in vanadium has been studied by channeling experiments. Deuterium is found in the tetrahedral sites for thermally doped specimens and in displaced tetrahedral sites (0.36 Å towards the octahedral sites) for implantation doped specimens. The difference in the lattice location is explained by the presence of trapping centers after deuterium implantation.