jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

15 Dec 1987

Volume 62, Issue 12, pp. 4653-4946

Page 1 of 3 Pages Next Page | Jump to Page

Generation of GW VHF power pulses with a magnetically swept e beam and inverse e beam diodes

D. J. Johnson, T. R. Lockner, and J. W. Poukey

J. Appl. Phys. 62, 4653 (1987); http://dx.doi.org/10.1063/1.339014 (9 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
The concept of converting a multi‐kA relativistic e beam into an ultrahigh‐power rf pulse with a magnetically swept e‐beam switch is studied. Two short VHF pulses are created by rapidly switching a 60‐ns, 900‐keV, 15‐kA e beam between a pair of inverse e‐beam diodes. The switching is done by a transverse 500‐G, sinusoidal B field, oscillating at 50 MHz. The e‐beam pulses are transported 1.6–4.6 cm in vacuum and ballistically or magnetically focused onto the collectors of the inverse diodes. The inverse diodes extract electrical energy from the deflected e‐beam pulses and transport the energy to resistive loads that varied between 30 and 130 Ω. Numerical simulations of the e‐beam transport with self‐electric and magnetic fields are performed that show the sources of electrical inefficiency. These occur because the e beam is near the space‐charge limit during transport. Peak unipolar powers of 2.0 and 0.5 GW are coupled to the resistive loads for the ballistically and magnetically transported e‐beam geometries, respectively.
Show PACS
41.75.Ht Relativistic electron and positron beams
52.59.Mv High-voltage diodes
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.32.Dd Connectors, relays, and switches

Competition between second harmonic generation and one‐ and two‐photon absorption in the anthracene/9,10‐dihydroanthracene mixed crystal

A. Bree, A. Leyderman, and C. Taliani

J. Appl. Phys. 62, 4662 (1987); http://dx.doi.org/10.1063/1.339015 (6 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Second harmonic generation (SHG) in single crystals of 9,10‐dihydroanthracene (DHA) is reported. If the axes of the optical indicatrix are labeled X, Y, and Z (with X the fast ray) then Y‐polarized SHG is observed at room temperature using Z‐polarized laser excitation at 687.9 nm; in this YZ section both the incoming and outgoing rays behave ordinarily (no walk‐off problem). There was some anthracene impurity present in all samples, and since anthracene absorbs near 340 nm, SH production could be followed by observing the resulting anthracene fluorescence; anthracene bands were observed as peaks or dips in the fluorescence response curve. These observations can be accounted for using a simple model in which SHG is purely a property of DHA, the presence of anthracene acting only to attenuate the conversion efficiency, which was always held <1% to avoid crystal damage.
Show PACS
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.-e Optical properties of bulk materials and thin films
78.40.Ha Other nonmetallic inorganics

Observational strategies for three‐dimensional synchrotron microtomography

Brian P. Flannery and W. G. Roberge

J. Appl. Phys. 62, 4668 (1987); http://dx.doi.org/10.1063/1.339016 (7 pages) | Cited 15 times

Full Text: | Download PDF

Show Abstract
We describe essential features of a data set of projection measurements suitable for tomographic imaging with given accuracy and resolution, and apply the results to analyze the use of synchrotron radiation to perform three‐dimensional microtomography. Previously, Grodzins [Nucl. Instrum. Methods 206, 541 (1983)] showed that the number of photons needed to generate an image could be minimized by adjusting the observational energy such that the target’s optical depth FD=2. We correct and extend his results to consider also the spectral distribution of the source. Observational time is minimized at a (typically) lower observational energy where the source flux is larger, even though FD≥2. The results demonstrate that, in principle, synchrotron sources provide sufficient brightness to image small samples with ≂1‐μm resolution.
Show PACS
07.85.-m X- and γ-ray instruments
78.70.Dm X-ray absorption spectra
42.30.Wb Image reconstruction; tomography
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Digital optical processing with photorefractive materials: Applications of a parallel half‐adder circuit to algorithmic state machines

H. Rajbenbach

J. Appl. Phys. 62, 4675 (1987); http://dx.doi.org/10.1063/1.339017 (7 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Theoretical and experimental results are presented for a real‐time parallel half‐adder circuit with the use of nonlinear interactions in photorefractive media. The two‐valued intensity input bit planes contain 256 bits in a 16×16 format. They are processed in parallel by three photorefractive BaTiO3 crystals operating in a two‐wave mixing configuration. Sequential algorithms for binary arithmetic can be implemented by providing the processor with a feedback loop. A prototype photorefractive algorithmic state machine that performs multibit operations between two arrays of numbers is proposed. The addition of two sequences of 5‐bit numbers is experimentally demonstrated, and improved performances are expected with the use of phase conjugation techniques.
Show PACS
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
78.20.Jq Electro-optical effects

Strain and pore pressure propagation in a water‐saturated porous medium

Jos G. M. van der Grinten, Marinus E. H. van Dongen, and Hans van der Kogel

J. Appl. Phys. 62, 4682 (1987); http://dx.doi.org/10.1063/1.339018 (6 pages) | Cited 17 times

Full Text: | Download PDF

Show Abstract
Wave propagation in a water‐saturated porous column consisting of fixed sand particles is studied by means of a shock tube technique. Pore pressures and axial strains are recorded simultaneously. The measurements show a coincident compression of pore fluid and porous column during the passage of the first wave. Due to the second wave the pore fluid is compressed while the porous material expands. This observed behavior is in agreement with theoretical predictions. The introduction of a frequency‐dependent permeability and an effective pore radius based on a cylindrical duct model yields an improved description of the damping of the second wave.
Show PACS
47.56.+r Flows through porous media
62.30.+d Mechanical and elastic waves; vibrations
62.50.-p High-pressure effects in solids and liquids
43.20.-f General linear acoustics

Impedance characteristics of an rf parallel plate discharge and the validity of a simple circuit model

P. Bletzinger and Mark J. Flemming

J. Appl. Phys. 62, 4688 (1987); http://dx.doi.org/10.1063/1.339019 (8 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
Measurements of the electrical characteristics of a parallel plate rf discharge at pressures from 0.1 to 10 Torr in argon and at frequencies from 7.1 to 20 MHz are reported. The discharge impedance reaches a minimum for all frequencies at a pressure of about 1 Torr and the impedance decreases with increasing frequencies. The phase variation over the pressure range is as high as 40°. With added attaching gas, the impedance increases and the minimum occurs at lower pressures. A simple equivalent circuit with a capacitance representing the electrode sheaths can model the measured impedance behavior at pressures up to 1 Torr when the capacitance is made proportional to pressure, analogous to the sheath characteristics. At higher pressures, a good fit can be achieved by making the resistance, which represents the power losses in the discharge volume, a function of pressure. Derived sheath dimensions correlate with observed variations versus pressure and frequency. The fact that at the lower pressures the resistive part of the impedance is independent of pressure and that the resistance no longer properly represents the voltage drop across the discharge volume indicates that collisional losses in the volume no longer dominate the power deposition. The ‘‘wave‐riding’’ mechanism is suggested as the dominant process in this pressure range. Its frequency characteristic correlates well with the frequency characteristic of the measured impedance.
Show PACS
52.80.Pi High-frequency and RF discharges
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Ds Electric and magnetic measurements

Two‐dimensional studies of streamers in gases

S. K. Dhali and P. F. Williams

J. Appl. Phys. 62, 4696 (1987); http://dx.doi.org/10.1063/1.339020 (12 pages) | Cited 135 times

Full Text: | Download PDF

Show Abstract
We present the results of two‐dimensional computer simulations of streamer initiation and propagation in atmospheric pressure N2. The simulation algorithm makes use of flux‐corrected transport techniques and was used as a tool to study the solutions of the transport equations under conditions suitable for streamers, for which realistic analytic solutions are not known. We present and discuss conclusions about streamer transport based on the results of these studies. Finally, we present a novel method of checking on the numerical accuracy with which the algorithm solves the transport equations.
Show PACS
52.25.Kn Thermodynamics of plasmas
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.25.Fi Transport properties

Magnetic stabilization of a rotating glow discharge

J. E. Harry and D. R. Evans

J. Appl. Phys. 62, 4708 (1987); http://dx.doi.org/10.1063/1.339021 (4 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
A series of measurements have been made on a magnetically rotated glow discharge over a range of pressure of 24–53 mbars. An increase in the current at which the glow‐to‐arc transition occurred from 550 mA for a stationary discharge to 2.5 A at a magnetic flux density of 0.025 T for a rotating discharge, with a corresponding power increase at the glow‐to‐arc transition from 250 to 1540 W was measured. At magnetic flux densities of about 0.017 T a discontinuity in the discharge voltage was observed which was caused by the discharge rotating in its own wake. Results from other sources have indicated that a glow discharge can be maintained up to discharge currents of 10 A, however, the results obtained here under identical conditions indicate that the discharge was not a glow but an arc. The results have important implications to power limited glow‐discharge processes such as CO2 lasers, ozone generation, and low‐pressure chemical synthesis.
Show PACS
52.80.Hc Glow; corona
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Spectroscopic studies of plasma during cw laser gas heating in flowing argon

J. Mazumder, T. J. Rockstroh, and H. Krier

J. Appl. Phys. 62, 4712 (1987); http://dx.doi.org/10.1063/1.339022 (7 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
cw laser gas heating in flowing argon was studied using emission spectroscopy. The local electron temperature was calculated from the 415.8‐nm Ari line spectra ratio to the adjacent continuum emission. The two‐dimensional temperature fields were utilized in the calculation of laser power absorption, beam refraction, radiative losses, and net thermal energy retained by the gas. The experiments were performed over a range of laser powers from 2.5 to 6.4 kW and flow velocities between 15 and 120 cm/s. The plasmas were determined to absorb as much as 78% of the incident laser energy at high powers and low flowrates. The calculations indicate that thermal energy retained by the gas is in excess of 35% of the incident energy at intermediate power levels and high flowrates. The results compare favorably with independent calorimetric and thermometric measurements as well as a numerical model. The primary conclusion is that laser propulsion appears feasible in that the earlier dynamic concerns have been shown to be nonexistent or circumventable.
Show PACS
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
84.60.-h Direct energy conversion and storage
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.75.Di Ion and plasma propulsion

Electric field and electrode potential drops of arcs and glow discharges in air

J. P. Novak

J. Appl. Phys. 62, 4719 (1987); http://dx.doi.org/10.1063/1.339023 (6 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
A simple experimental arrangement consisting of two arcs burning in series has been devised for measurement of the voltage gradient in the discharge column. The method is based on reciprocal variation of the length of the discharges so that the total length during the measurement is constant. Experiments have been performed in the current range between 20 mA and 4 A in dry air at pressures between 20 and 150 kPa. In the arc mode the current dependence of the field can be approximated by the power function E∝Iα, where the exponent α for pressures between 60 and 150 kPa is −0.54 and slightly higher at lower pressures. The pressure dependence (at constant current) can be expressed in similar form E∝pm with the exponent m equal to 0.15 and 0.24 for currents of 1 and 4 A, respectively, and for pressures above 40 kPa. Average values of the zero‐length voltage were obtained in the arc and glow discharge modes, namely, 14.5 V in the case of the arc and 367, 346, 331, and 331 V for the glow discharge at pressures of 20, 60 100, and 150 kPa, respectively.
Show PACS
52.80.Hc Glow; corona
52.70.Ds Electric and magnetic measurements
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Filamentation instability in an inhomogeneous laser‐produced plasma

A. K. Sharma and G. Mishra

J. Appl. Phys. 62, 4725 (1987); http://dx.doi.org/10.1063/1.339024 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
A laser beam propagating along the density gradient in a laser‐produced plasma is unstable to a transverse density perturbation. When ambient density scale length is comparable to growth length, spatial growth is faster than the exponential. For a linear density profile the amplitude of the filament varies with z as an Airy’s function, whereas for an exponential profile it goes as a Bessel function of imaginary order and argument. In both cases the growth rate increases with the transverse wave vector of the perturbation.
Show PACS
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Magnetomechanical sensing of laser‐generated ultrasound to assess structural change in metallic amorphous ribbons

R. D. Greenough, R. J. Dewhurst, and C. Edwards

J. Appl. Phys. 62, 4728 (1987); http://dx.doi.org/10.1063/1.339025 (4 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
A new noncontacting technique is described for monitoring the structural changes in metallic amorphous ribbons. Laser‐generated ultrasound is propagated from a line source, and a magnetomechanical sensing coil is used to monitor the waveform at some distance away from the source. The quality of the ribbon is assessed by either changes in velocity or amplitude of the magnetomechanical signals from the coil, which itself depends on the strength of the applied magnetic field. Metglas 2605 SC has been studied in this way, showing that velocities change from 4940 to 5830 ms−1 as the material becomes progressively less amorphous, while corresponding maximum amplitudes of the sensing coil signal reduce some 18‐fold.
Show PACS
81.70.-q Methods of materials testing and analysis
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
75.50.Kj Amorphous and quasicrystalline magnetic materials

Thermomechanical properties of amorphous silicon and nonstoichiometric silicon oxide films

F. Jansen, M. A. Machonkin, N. Palmieri, and D. Kuhman

J. Appl. Phys. 62, 4732 (1987); http://dx.doi.org/10.1063/1.339026 (5 pages) | Cited 15 times

Full Text: | Download PDF

Show Abstract
The thermomechanical properties of glow‐discharge‐deposited silicon and silicon oxide films were measured between room temperature and 100 °C as a function of composition and substrate temperature during deposition. A cantilevered beam measurement technique, allowing the simultaneous measurement of the linear thermal expansion coefficient of thin films and their mechanical compliance, was used and verified. Hydrogenated amorphous silicon films, deposited at 250 °C with a density of 2.0 g/cm3 and 20 at. % of hydrogen, exhibit a linear thermal expansion coefficient of about 4.4×10−6/°C and a biaxial elastic modulus of 150 GPa. The expansion coefficient of silicon oxide films deposited at 250 °C shows a systematic dependence on the fabrication conditions and ranges from about 10−5/°C to negative values. Strong correlations between the hydrogen concentration of the films, the film density, and thermal expansion coefficient were observed and are discussed. The biaxial elastic modulus of the oxide films is not strongly dependent on the gas ratio and is about 40 GPa, substantially smaller than the values obtained for thermally grown oxides. These differences are attributed to the effect of network terminations by hydrogen and –OH groups. Films of fixed composition (nitrous oxide/silane=12), deposited at substrate temperatures below 200 °C, exhibit an apparent negative coefficient of thermal expansion when first heated. However, this contraction has been determined to be due to the expulsion of water vapor, causing these films to densify. The true thermal expansion coefficients, measured after annealing at 100 °C for extended periods, are positive and do not change within experimental error for this fixed composition over the range of deposition temperatures.
Show PACS
65.40.De Thermal expansion; thermomechanical effects
68.60.Wm Other nonelectronic physical properties
62.20.D- Elasticity

Dose rate dependence and time constant of the ion‐beam‐induced crystallization mechanism in silicon

J. Linnros and G. Holmén

J. Appl. Phys. 62, 4737 (1987); http://dx.doi.org/10.1063/1.339027 (8 pages) | Cited 22 times

Full Text: | Download PDF

Show Abstract
The influence of dose rate on the ion‐beam‐induced crystallization of amorphous layers in silicon has been investigated. The amorphous layers were produced by self‐ion implantation both in bulk silicon and in silicon on sapphire. Subsequent recrystallization was induced at 200 to 400 °C by Ne, Si, Ar, and Kr ion beams of 300 keV energy passing through the amorphous layers. Rutherford backscattering/channeling measurements showed that the regrowth rate decreased with increasing dose rate. This behavior was more pronounced for heavy ions where high dose rates and/or low temperatures could reverse the recrystallization and induce further amorphous growth of the layer. In this new solid‐phase growth regime, the amorphous/crystalline interface moved inwards into the crystal in a manner similar to an epitaxial process. An intermittent beam experiment yielded a time constant for the ion beam induced crystallization mechanism of the order of 0.3 s. The time constant and a scaling law for different ions support a model where the planar growth is caused by the accumulation of divacancies in the interface region.
Show PACS
61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Dv Composition, segregation; defects and impurities

A study of silicon interstitial kinetics using silicon membranes: Applications to 2D dopant diffusion

S. T. Ahn, P. B. Griffin, J. D. Shott, J. D. Plummer, and W. A. Tiller

J. Appl. Phys. 62, 4745 (1987); http://dx.doi.org/10.1063/1.339028 (11 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
The kinetics of silicon interstitial generation, recombination, and diffusion in floatzone (FZ) and Czochralski (CZ) silicon were studied during oxidation at 1100 °C using thin silicon membranes as test structures. One side of the membrane was oxidized to inject interstitials and the other side was covered with films of pad‐oxide and silicon nitride. The interstitial concentration was monitored at both sides of the membrane simultaneously to determine the interface and transport kinetics of interstitials. The interstitial supersaturation at the oxidizing side was found to be insensitive to both the thickness variation and to the interface condition of the other side of the membrane. A model for this effect is proposed. At the interface opposite the oxidizing side, a delayed buildup of interstitials was observed. Using these results for FZ Si and assuming that there was no bulk recombination, an effective interstitial diffusivity of 9×10−10 cm2/s and an effective interface recombination rate of 3×10−7 cm/s for a silicon/pad‐oxide interface were obtained. Interstitial transport across the CZ Si membranes during oxidation was slower than that across FZ membranes. The parameters extracted from these studies have been used to successfully model 2D dopant diffusion.
Show PACS
61.72.Bb Theories and models of crystal defects
61.72.jd Vacancies
61.72.jj Interstitials
66.30.-h Diffusion in solids
81.65.-b Surface treatments

Growth of undoped ZnSe on (100) GaAs by molecular‐beam epitaxy: An investigation of the effects of growth temperature and beam pressure ratio

J. M. DePuydt, H. Cheng, J. E. Potts, T. L. Smith, and S. K. Mohapatra

J. Appl. Phys. 62, 4756 (1987); http://dx.doi.org/10.1063/1.339029 (7 pages) | Cited 53 times

Full Text: | Download PDF

Show Abstract
Thin (1.5–2.5 μm thick) ZnSe films have been grown on (100) GaAs substrates by molecular‐beam epitaxy to investigate the effects of growth conditions on film properties. A ‘‘growth matrix’’ was generated by systematically adjusting the growth temperature (TG) through 250, 300, 350 and 400 °C while setting the Zn‐to‐Se beam pressure ratio at 1/4:1, 1/2:1, 1:1, and 2:1. Reflection high‐energy electron diffraction (RHEED) patterns monitored during growth showed surface reconstructions which were characteristic of either Zn‐ or Se‐stabilized growth. In addition to the transition between the two surface reconstructions, a transition from streaky to spotty RHEED patterns was discovered. Both transition lines were mapped onto growth parameter space and their intersection provides a unique reference point in growth space. Low‐temperature photoluminescence, optical microscopy and Hall measurements were used to characterize the samples in this growth matrix study and these results were found to be related to the RHEED transitions. One narrow region of growth space was found to produce samples with intense, narrow near‐band‐edge peaks and small deep‐level intensity. Although it was still n type, one of the samples with growth conditions in this region was measured to have a carrier concentration less than 5.6×1015 cm−3 and a peak mobility greater than 7150 cm2/V s.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Et II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

A phenomenological model for surface deposition kinetics during plasma and sputter deposition of amorphous hydrogenated silicon

Mark J. Kushner

J. Appl. Phys. 62, 4763 (1987); http://dx.doi.org/10.1063/1.339030 (10 pages) | Cited 18 times

Full Text: | Download PDF

Show Abstract
The surface processes during the plasma‐enhanced chemical vapor deposition and reactive sputter deposition of amorphous hydrogenated silicon (a‐Si:H) are investigated by use of a phenomenological model. The model consists of an accounting, in rate equation form, of adsorption of radicals from the plasma onto the surface, surface diffusion, incorporation into the lattice, interconnection of bonds in the lattice, and burial of species on the surface, thereby constituting film growth. By accounting for the coordination partners of Si atoms in the film, the atomic fraction of hydrogen in the film is computed for the lattice and for hydrogen in polymeric or isolated configurations. Results from the model are discussed while parametrizing the probability for hydrogen elimination during incorporation and the probability for saturation of dangling bonds by gas phase species. We find that the mode of hydrogen elimination during incorporation distinguishes films grown dominantly from SiH2 or SiH3 radicals. Characteristics of films grown by sputter deposition are investigated as a function of the composition of the radical flux. We find that films grown from hydrogen‐rich fluxes are composed dominantly of dihydride (Si HH) configurations, whereas hydrogen‐lean mixtures are composed of dominantly hydride ( 3/4 Si–H) configurations.
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Cd Deposition by sputtering
52.40.Hf Plasma-material interactions; boundary layer effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Thermal emission and capture rates of holes at the gold donor level in silicon

Luke Su Lu, Toshikazu Nishida, and Chih‐Tang Sah

J. Appl. Phys. 62, 4773 (1987); http://dx.doi.org/10.1063/1.339031 (8 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Thermal emission rate and capture cross section of holes at the gold donor level are measured in silicon n+/p junctions with boron acceptor concentrations of 1.5×1012 cm−3 to 2.8×1015 cm−3, showing no boron concentration dependencies. The emission rate is independent of electric field in the range of 102 to 2×104 V/cm. However, the emission rate varies with the voltage applied to the insulated‐gate guard ring, requiring re‐evaluation of previously published data. The thermal capture cross section agrees with most of the published work. The magnitude of the capture cross section and its temperature independence support a neutral potential model for hole capture at the gold donor level.
Show PACS
71.55.Ht Other nonmetals
79.40.+z Thermionic emission
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

An antimony‐related electronic level in isovalently doped bulk GaAs

W. C. Mitchel and P. W. Yu

J. Appl. Phys. 62, 4781 (1987); http://dx.doi.org/10.1063/1.339032 (5 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
Temperature‐dependent Hall‐effect and photoluminescence measurements have been performed on a series of antimony‐doped bulk GaAs samples that were otherwise undoped. A new donor level located 0.48 eV below the conduction‐band edge has been detected by both experiments in all antimony‐doped samples studied. This level reduces the resistivity of antimony‐doped material below the semi‐insulating limit. Comparison with known intrinsic levels in undoped material have been made and it is shown that the 0.48‐eV donor is distinct from any of these. It is concluded that the defect responsible for the 0.48‐eV donor involves an impurity antisite SbGa either isolated or in a complex with intrinsic defects.
Show PACS
71.55.Eq III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
78.55.Cr III-V semiconductors

The capture barrier of the DX center in Si‐doped AlxGa1−xAs

P. M. Mooney, N. S. Caswell, and S. L. Wright

J. Appl. Phys. 62, 4786 (1987); http://dx.doi.org/10.1063/1.338981 (12 pages) | Cited 106 times

Full Text: | Download PDF

Show Abstract
We report measurements of the capture barrier for the DX center in Si‐doped AlxGa1−xAs as a function of the alloy composition. A model of the capture process which requires a distribution of capture barrier heights has been fit to the data for samples with x=0.35. A simple technique is used to extract the average capture barrier height from data for samples with AlAs mole fraction ranging from x=0.27 to x=0.55. The barrier height varies strongly with the composition and has a minimum at x=0.35. The implications of these results are discussed.
Show PACS
71.55.Eq III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Efficiency of photoconductive switches

Benjamin Senitzky, Ronald D. Schrimpf, and William J. Kerwin

J. Appl. Phys. 62, 4798 (1987); http://dx.doi.org/10.1063/1.338982 (8 pages)

Full Text: | Download PDF

Show Abstract
Theoretical expressions which relate the terminal characteristics of photoconductive switches to the incident light are derived. The integral of the product of the total current density (conduction and displacement) and the electric field in the absence of light is shown to be equal to the vi product at the terminals. Theoretical predictions based on these relations are compared to experimental measurements with continuous and pulsed light sources on a 2000‐Ω cm silicon switch embedded in a microstrip geometry. When n+ contacts are used, the device exhibits a photoconductive gain of 3.6 at the anode and almost no photosensitivity at the cathode. Its behavior is consistent with the space‐charge neutrality condition. When p+ contacts are used the photosensitivity is localized in the cathode region. In both cases the enhanced carrier recombination at the surface strongly affects the terminal characteristics. The pulsed light measurements are compared to the continuous illumination results.
Show PACS
84.32.Dd Connectors, relays, and switches
72.40.+w Photoconduction and photovoltaic effects
85.60.Dw Photodiodes; phototransistors; photoresistors
73.25.+i Surface conductivity and carrier phenomena

Method of determining capture cross section including a slow capture of carriers in the depletion edge region

H. Tomokage, T. Miyamoto, H. Okushi, and Y. Tokumaru

J. Appl. Phys. 62, 4806 (1987); http://dx.doi.org/10.1063/1.338983 (6 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
The capture process of carriers in the pulse‐filling measurements is analyzed by including the slow capture on the edge of a depletion layer. An analytical expression is derived to determine the capture cross section of majority carriers from the initial slope of the semilogarithmic plot of capacitance versus capture time in the case of low trap concentration. A method is proposed to determine the fast capture rate in the bulk region from a slow capture process in the edge region when the trap concentration is not negligible compared with the concentration of the shallow dopant. The edge effect is intentionally enhanced to observe the capacitance variation with the capture time. Pulse‐filling measurements on Au‐doped Si p+n and undoped liquid‐encapsulated Czochralski n‐GaAs Schottky diodes are made to verify the method.
Show PACS
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Effect of interface states on the electrical properties of W, WSix, and WAlx Schottky contacts on GaAs

A. Callegari, D. Ralph, N. Braslau, E. Latta, and G. D. Spiers

J. Appl. Phys. 62, 4812 (1987); http://dx.doi.org/10.1063/1.338984 (9 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
Barrier heights of refractory W, WSix, and WAlx Schottky contacts deposited on n‐GaAs with different surface treatments have been electrically characterized by current‐voltage, capacitance‐voltage, and internal photoemission measurements. Internal photoemission measurements indicate that the Fermi level pins approximately at midgap (Φn ≂0.7–0.8 eV). The current‐voltage barrier heights were consistent with internal photoemission for diodes with little oxide at the GaAs/metal interface. For an oxide layer of about 2.5 nm, current‐voltage barrier heights as high as 0.9 eV were observed. Capacitance‐voltage barrier heights were found to be 0.9–1 eV with a weak dependence on interface oxide. A theoretical model was developed to explain these results. A large density of states (5×1013–1014/cm2) at the GaAs/metal interface which exchanges charge mainly with the metal appears to explain well our experimental capacitance‐voltage and current‐voltage data.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Evidence for weak link and anisotropy limitations on the transport critical current in bulk polycrystalline Y1Ba2Cu3Ox

J. W. Ekin, A. I. Braginski, A. J. Panson, M. A. Janocko, D. W. Capone, N. J. Zaluzec, B. Flandermeyer, O. F. de Lima, M. Hong, J. Kwo, and S. H. Liou

J. Appl. Phys. 62, 4821 (1987); http://dx.doi.org/10.1063/1.338985 (8 pages) | Cited 144 times

Full Text: | Download PDF

Show Abstract
Measurements of the transport critical‐current density (Jc), magnetization Jc, and magnetoresistance in a number of bulk sintered samples of Y1Ba2Cu3Ox from several different laboratories indicate that the transport Jc is limited by weak‐link regions between high Jc regions. The weak‐link Jc has a Josephson character, decreasing by two orders of magnitude as the magnetic field is increased from 0.1 to 10 mT at 77 K. An examination of the grain‐boundary region in Y1Ba2Cu3Ox shows no observable impurities or second phases to the scale of the [001] lattice planes (∼12 Å). The effect of intrinsic conduction anisotropy is discussed. A current‐transfer model is proposed in which weak conduction along the c axis plays a role in limiting Jc at grain boundaries. Orienting the grains in the powder state during processing may result in enhanced transport Jc in bulk conductors.
Show PACS
74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates
61.72.Mm Grain and twin boundaries
72.20.My Galvanomagnetic and other magnetotransport effects

Effect of transverse compressive stress on the critical current and upper critical field of Nb3Sn

J. W. Ekin

J. Appl. Phys. 62, 4829 (1987); http://dx.doi.org/10.1063/1.338986 (6 pages) | Cited 32 times

Full Text: | Download PDF

Show Abstract
A large reversible degradation of the critical current of multifilamentary Nb3Sn superconductors has been observed when uniaxial compressive stress is applied transverse to the conductor axis at 4 K. In bronze‐process multifilamentary Nb3Sn, the onset of significant degradation occurs at about 50 MPa. In an applied field of 10 T, the magnitude of the effect is about seven times larger for transverse stress than for stress applied along the conductor axis. The transverse stress effect increases with magnetic field and is associated with a reversible degradation of the upper critical field. The intrinsic effect of transverse stress on the upper critical field is about ten times greater than for axial stress. Although axial stresses on the Nb3Sn filaments are greater than transverse stresses in most applications, the transverse stress effect will need to be considered in the internal design of large magnets because of the greater sensitivity of Nb3Sn to transverse stress. It is shown that the transverse stress from the Lorentz force on the conductor is proportional to conductor thickness. This will place limits on conductor dimensions and the spacing between distributed reinforcement in large magnets. The effect may be particularly significant in cabled conductors where large transverse stress concentrations can occur at strand crossover points.
Show PACS
74.25.Sv Critical currents
81.40.Rs Electrical and magnetic properties related to treatment conditions
74.25.Op Mixed states, critical fields, and surface sheaths
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close