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  • American Institute of Physics (AIP)
  • American Meteorological Society
  • 2015-2019  (32)
  • 1985-1989  (11)
  • 2018  (7)
  • 2016  (25)
  • 1987  (11)
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  • 2015-2019  (32)
  • 1985-1989  (11)
Year
  • 1
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    High-speed modulation from the fast mode extraction of a photonic crystal light-emitting diode (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-01-07
    Description: Using light-emitting diodes (LEDs) for visible light communication has become an alternative choice of radio source due to channel crowding of the radio-frequency (RF) signal. The modulation bandwidth of LEDs is usually limited by the spontaneous carrier lifetime in multiple quantum wells. Here, sub-GHz modulation of GaN-based LED employing photonic crystal (PhC) nanostructure is demonstrated. The guided photonic modes of the LEDs are modulated by the RF signal. Both carrier lifetime of lower- and higher-order modes are studied in time-resolved photoluminescence (TRPL) at room temperature. The f - 3 dB - J curve of the PhC LED exhibits a higher bandwidth than the typical LED structure. At 11.41 kA/cm 2 , the optical −3-dB bandwidth ( f - 3 dB ) up to 234 MHz of the PhC LED (PhCLED) is achieved. Our studies on TRPL at different wavelengths and frequency response at different injection current densities conclude that the higher operation speed is attributed to faster radiative carrier recombination of extracted guided modes from the PhC nanostructure.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
    Electronic Resource
    Electronic Resource
    Hg incorporation in CdTe during the growth of HgTe-CdTe superlattices by molecular beam epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1545-1547 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98630
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  • 3
    Electronic Resource
    Electronic Resource
    AlGaAs/GaAs quantum wells with high carrier confinement and luminescence efficiencies by organometallic chemical vapor deposition (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 120-125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single and multiple quantum wells with well widths ranging from 10 to 135 A(ring) were grown by atmospheric pressure organometallic chemical vapor deposition and characterized by photoluminescence (PL) and electrical measurements. Compared with single layers of high-purity GaAs and AlGaAs which have high intensity near band-edge excitonic transitions, the quantum well (QW) structures exhibit very strong luminescence of the discrete QW eigenstates. The intense QW signals indicate that the carrier confinement efficiency of the wells is very high, which is also supported by significant mobility enhancement in the samples. The sharp PL lines suggest high quality and smoothness of the well interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339170
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence characteristics of selectively grown GaAs and AlGaAs/GaAs quantum wells (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2466-2469 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs and AlGaAs/GaAs multiple quantum wells (MQW) were selectively deposited on GaAs substrates patterned with native oxide, and photoluminescence (PL) characteristics of both the single crystal grown in open windows and the polycrystalline material deposited on the oxide masks were studied. Well-resolved distinct quantum-well (QW) transition peaks indicate no degradation of the epitaxial material quality in the small single-crystal areas. The PL of polycrystalline GaAs is very weak and the peak is centered around the near-band-edge transition energy of GaAs. Polycrystalline MQW structures exhibit much stronger PL signals, and the peak position shifts corresponding to the widths of the QWs grown. These results suggest that the quantum size effect is preserved in the polycrystalline material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339455
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of ultrasound velocity in the spin-glass CuMn (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2074-2077 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrasound velocity measurements may be used to study the dynamics of the spin-glass phase. Near the transition temperature, the sound speed deviates slightly from that of the pure nonmagnetic host. We measured the velocity anomaly in a 1-at. % CuMn sample near the transition temperature (12 K) as a function of frequency from 5 to 100 MHz and found its size to be frequency independent. We also found changes in the anomaly when the sample was field cooled in transverse 4.7- and 14.2- kG fields. These results are discussed in light of previously published theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338947
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  • 6
    Electronic Resource
    Electronic Resource
    Damage induced by CHF3+C2F6 plasma etching on Si-implanted GaAs(100) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1729-1733 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage induced by CHF3+C2F6 plasma etching on GaAs(100) was studied. We exposed GaAs(100) surfaces to various etching conditions and monitored sheet resistance, carrier concentration, and Hall mobility. Significant losses of Hall mobility and carrier concentration, and an increase in sheet resistance were observed only when CHF3 was introduced into the plasma. After annealing at 400 °C for 55 min, sheet resistance was restored nearly to the value obtained before the plasma exposure. We believe that the damage was produced by hydrogen atoms or ions dissociated from CHF3 in the plasma. In contrast to the general belief that plasma etching induces the least damage among dry etching techniques [such as reactive ion etching (RIE) and reactive ion beam etching (RIBE)], our plasma etching damage was comparable to previously reported RIE or RIBE damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339601
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  • 7
    Electronic Resource
    Electronic Resource
    The tokamak equilibrium profile (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1221-1224 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fully relaxed magnetohydrodynamic (MHD) equilibrium is obtained by imposing nonideal MHD perturbations constrained by the total plasma current. The minimum energy state governed by Δ*ψ+CF exp(ψ/λ)+CpR2 exp(5ψ/4λ) =0 reveals properties of profile consistency, bifurcated solutions, and a loss of equilibrium condition. It predicts the transport coefficient peaked at the plasma edge and a unique current profile for given q0 and ql.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866273
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  • 8
    Electronic Resource
    Electronic Resource
    Hamiltonian four-field model for nonlinear tokamak dynamics (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3204-3211 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hamiltonian four-field model is a simplified description of nonlinear tokamak dynamics that allows for finite ion Larmor radius physics, as well as other effects related to compressibility and electron adiabaticity. Much simpler than some previous descriptions of the same physics, it still preserves essential features of the underlying exact dynamics. In particular, because it is a Hamiltonian dynamical system it conserves the appropriate Casimir invariants, as well as avoiding implicit, unphysical dissipation. Here the model is derived and interpreted, its Hamiltonian nature is demonstrated, and its constants of motion are extracted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866527
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  • 9
    Electronic Resource
    Electronic Resource
    Nonperturbative theory of temperature-dependent optical dephasing in crystals. IV. Microscopic model for pseudolocal phonons (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 54-59 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We continue our study of the optical dephasing of impurities by phonons. The pure dephasing contribution to the homogeneous linewidth is calculated to all orders in the excitation–phonon interaction. We introduce a microscopic model for the pseudolocal phonon spectral density when the impurity is in the ground electronic state. This microscopic model improves upon our previous phenomenological model. The model is applied to several experimental systems—in all cases, the theoretical results provide a reasonably accurate description of the temperature-dependent linewidth with no adjustable parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453603
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  • 10
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    Influence of Cloud Microphysics and Radiation on Tropical Cyclone Structure and Motion (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-05-01
    Description: The authors survey a series of modeling studies that have examined the influences that cloud microphysical processes can have on tropical cyclone (TC) motion, the strength and breadth of the wind field, inner-core diabatic heating asymmetries, outer-core convective activity, and the characteristics of the TC anvil cloud. These characteristics are sensitive to the microphysical parameterization (MP) in large part owing to the cloud-radiative forcing (CRF), the interaction of hydrometeors with radiation. The most influential component of CRF is that due to absorption and emission of longwave radiation in the anvil, which via gentle lifting directly encourages the more extensive convective activity that then leads to a radial expansion of the TC wind field. On a curved Earth, the magnitude of the outer winds helps determine the speed and direction of TC motion via the beta drift. CRF also influences TC motion by determining how convective asymmetries develop in the TC inner core. Further improvements in TC forecasting may require improved understanding and representation of cloud-radiative processes in operational models, and more comprehensive comparisons with observations are clearly needed.
    Print ISSN: 0065-9401
    Electronic ISSN: 1943-3646
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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