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  • 2000-2004  (31)
  • 1985-1989  (84)
  • 1950-1954  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Band parameters for III–V compound semiconductors and their alloys (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5815-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1368156
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  • 2
    Electronic Resource
    Electronic Resource
    Synchronizable Q-switched, mode-locked, and cavity-dumped ruby laser for plasma diagnostics (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4892-4896 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the design and operation of an optimized version of a Q-switched, mode-locked, and cavity-dumped ruby-laser oscillator. The modulator window is much narrower than that assumed in conventional active mode-lock theory, and is shown to yield much shorter pulses than the latter in cases where the number of round trips is restricted. To allow a high-power pulse (≈1 GW) to evolve in the oscillator, and to allow simple synchronization to a (∼100 ns fixed delay) CO2 laser, a limit of 23 round trips was chosen, but similar limits may be imposed by lasers having short-gain duration as in an excimer laser. Details are given on the single spark gap switching element and Pockels cells, with an analysis of their expected switching speeds, in order to establish the effectiveness of the modulator, as compared to conventional sinusoidally driven active mode lockers. Single pulses of 50–70 mJ are reliably cavity-dumped after only 100-ns delay (23 round trips) with pulse length adjustable from 50–100 ps with ±5-ps stability. Relative timing between the main (CO2) and probe (ruby) pulses allows a measurement accuracy of ±50 ps to be attained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335311
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  • 3
    Electronic Resource
    Electronic Resource
    Photo-Hall analysis for inhomogeneously excited semiconductors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4638-4644 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A more rigorous numerical method for determining bulk semiconductor transport properties from photo-Hall data is presented and is used to determine compensation densities in narrow-gap HgCdTe. Previous studies have treated carrier density inhomogeneities by means of a two-layer approach, assuming a photoexcitation layer of constant thickness associated with either the absorption depth or the ambipolar diffusion length. Here, we show that this approximation can lead to significant error. For arbitrary optical intensities a more detailed integration over depth is required, properly accounting for the variation in the optical and transport of the material with carrier density and optical intensity. In the present technique, the spatial profile of the carrier density, n(z), is calculated as a function of optical intensity Φ0. The electron mobility μ is expanded in known functions of the carrier density. By using this n(Φ0,z) and μ(n), integral expressions for the net conductivity and Hall coefficient are then evaluated. The unknown coefficients in the mobility expansion are varied parametrically to obtain the best fits to the measured Hall coefficient and conductivity as a function of optical flux. From this fit, the electron mobility is determined as a function of carrier density. Detailed sample calculations are performed for the case of narrow-gap, n-type Hg1−xCdxTe at low temperatures assuming 10.6 μm CO2 laser excitation. Analysis of the photo-Hall data using the improved method leads to a reliable determination of compensation densities in this material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335374
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  • 4
    Electronic Resource
    Electronic Resource
    Changes in soil chemistry and aggregate stability induced by fertilizer applications, burning and trash retention on a long-term sugarcane experiment in South Africa (2002)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Throughout the world there is a trend towards retaining crop residues rather than burning them. For this reason, changes in soil chemistry and aggregation in a Vertisol induced by 59 years of burning or green cane harvesting with or without annual fertilizer applications were investigated. Crop residues were either burnt prior to harvest with the harvest residues raked off (R1), burnt prior to harvest with the harvest residues left on the soil surface (R2), or left unburnt with all the trash left on the soil surface (R3). Concentrations of organic C in the surface 10 cm of soil increased with fertilizer applications and with increasing amounts of crop residue returned in the order R1 〈 R2 〈 R3. Fertilizer applications caused an accumulation of residual P in both inorganic (Pi) and organic (Po) forms. A sequential P fractionation showed that fertilizer P accumulated in both labile and recalcitrant Pi and Po forms, and trash retention caused an accumulation of recalcitrant Po. Concentrations of K decreased in the unfertilized R1 and R2 treatments because K reserves were depleted. By contrast, there was an increase in the concentrations of K in the fertilized R3 treatment. The soil became more acid on the fertilized and, to a lesser extent, trash retention plots. We attribute this to nitrification and subsequent nitrate leaching. Acidification resulted in a loss of exchangeable Ca and Mg, a decrease in ECEC, and an increase in the concentrations of total and monomeric Al in soil solution, in exchangeable Al3+ and in the buffering reserve of non-exchangeable Al associated with organic matter. Aggregate stability was increased by increasing crop residues but decreased by fertilizer applications. The decrease was attributed to an increase in the proportion of exchangeable cations present in monovalent form due to applications of fertilizer K and leaching of Ca and Mg. We conclude that trash retention and annual fertilizer applications have substantial long-term effects on both organic matter status and soil pH and therefore on other soil chemical and physical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2002.00472.x
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  • 5
    Electronic Resource
    Electronic Resource
    Far-field characteristics of mid-infrared angled-grating distributed feedback lasers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6997-7005 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The far-field emission characteristics of mid-infrared angled-grating distributed-feedback (α-DFB) lasers with W active regions are calculated using a self-consistent beam-propagation formalism that is more general than previous analyses. The theoretical projections are compared with the results of an experimental study of optically pumped α-DFB devices. Near-diffraction-limited beam quality is obtained both theoretically and experimentally for pump stripes ≤50 μm wide. While simulations employing the theoretical linewidth enhancement factor of 1.7 for the homogeneously-broadened W-laser gain spectrum predict that the good beam quality should be retained for stripes as wide as (approximate)200 μm, the data indicate a much more rapid degradation. That finding can be reproduced only by assuming that inhomogeneous broadening increases the structure's linewidth enhancement factor to (approximate)5. The experiments and theory also yield a steering of the output beam to off-normal angles as large as 6° when temperature tuning shifts the gain peak away from the grating resonance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326858
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  • 6
    Electronic Resource
    Electronic Resource
    Inherent peculiarities in nuclear reaction analysis (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1557-1559 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed description of the kinematics governing a nuclear reaction analysis is presented for exothermic reactions. In particular, the peculiar behavior demonstrated when the emitted particle energy decreases with increasing bombarding energy is emphasized. The method is applied to 16O(d,p)17O and D(d,p)T reactions from SiO2 and D2O targets, respectively. Moreover, an algorithm was written to compute reaction cross sections as a function of energy or concentration as a function of depth from the measured reaction yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341834
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  • 7
    Electronic Resource
    Electronic Resource
    Photo-Hall determination of acceptor densities in n-type HgCdTe (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1047-1054 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive photo-Hall investigation of compensation densities in n-type Hg1−xCdxTe (0.224〈x〈0.235) is reported. The technique consists of measuring the low-temperature electron mobility as a function of optically excited carrier density. Pulses of 25-μs duration from a CO2 laser yield excess electron-hole plasma densities of between 1013 and 1016 cm−3. At low excitation levels the mobility increases due to the neutralization of ionized acceptors by photoexcited holes, while at higher excitation levels the mobility slowly decreases due to electron-hole scattering. By comparing to a detailed theory for electron transport in photoexcited narrow-gap semiconductors, the density of compensating acceptors NA can be accurately determined. The theory is generalized to account for multi-ion scattering, carrier heating, surface conduction, and inhomogeneous excitation. Experimental refinements significantly extending the range of narrow-gap n-type samples for which compensation densities may be determined are discussed. The present study demonstrates the broad applicability of the technique by determining NA for samples with compensation ratios between 0.09 and 0.96 and with both single and double acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338196
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  • 8
    Electronic Resource
    Electronic Resource
    Synchronizable, injection-locked, Q-switched, mode-locked, and cavity-dumped ten-atmosphere CO2 laser (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 843-851 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel, active, mode-locking scheme for producing single, line-tunable, high-power ultrashort CO2-laser pulses is described. Using an auxiliary grating-tuned cw CO2 laser for injection locking on the 9R(16) line, the Q-switched, mode-locked, and cavity-dumped 10-atm CO2 laser produces single, detection-limited (〈500 ps) pulses of 5-mJ energy at λ=9.29 μm. Details are given on the traveling-wave GaAs Pockels cells, both of which are controlled by a single, ultraviolet (UV) triggered spark gap. The time-locked output pulse is delayed by precisely 300.7 ns with 〈±50 ps jitter against the UV triggered spark gap, so the laser pulse is synchronizable to an external event to 〈±250 ps. To drive the transverse-electric (TE) 10-atm amplifier section, instead of the conventional Marx bank or inductance-capacitance (LC) generator, a new type of circuit is used. The automatically preionized, double-sided LC inversion circuit uses only one spark gap, and a detailed description with operating characteristics is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338133
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  • 9
    Electronic Resource
    Electronic Resource
    High gain, multiatmosphere CO2 laser amplifier (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 261-264 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel TE discharge, 15-mm aperture, multiatmosphere, CO2 laser amplifier is described, with measured electrical characteristics and gain measurements on the 9.294-μm, 9R(16) line. The electrical circuit used in this amplifier is a realistic alternative to the Marx bank or conventional LC inversion circuit and, similarly, it would be useful for excitation of other gas lasers as well. This automatically preionized, double-sided, fourfold LC inversion circuit uses only one spark gap, and it is shown to provide small-signal gains of 5.7% cm−1, at 120 J l−1 atm−1 and 10 atm. The generalization to an n–stage device, which would be suitable for higher pressures, and larger apertures, is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139318
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  • 10
    Electronic Resource
    Electronic Resource
    Continuous-wave operation of λ=3.25 μm broadened-waveguide W quantum-well diode lasers up to T=195 K (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 256-258 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II "W" quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125739
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