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  • 1
    Electronic Resource
    Electronic Resource
    Optical properties of wurtzite GaN grown by low-pressure metalorganic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3691-3696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of optical studies on the properties of GaN grown by low-pressure metalorganic chemical-vapor deposition, with emphasis on the issues vital to device applications such as stimulated emission and laser action as well as carrier relaxation dynamics. By optical pumping, stimulated emission and lasing were investigated over a wide temperature range up to 420 K. Using a picosecond streak camera, the free and bound exciton emission decay times were examined. In addition, the effects of temperature and pressure on the optical interband transitions and the transitions associated with impurity/defect states were studied using a variety of spectroscopic methods, including photoluminescence and photoreflectance. The fundamental band gap of GaN was mapped out as a function of temperature using the empirical Varshni relation. The pressure coefficient of the gap was determined using diamond-anvil pressure-cell technique. The hydrostatic deformation potential for the direct Γ band gap was also derived from the experimental results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361200
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  • 2
    Electronic Resource
    Electronic Resource
    AlxGa1−xN polarity determination by x-ray diffraction (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1721-1723 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallographic polarities of (0001) oriented AlxGa1−xN epitaxial layers grown on basal plane sapphire were determined using the anomalous dispersion effect of x-ray diffraction. Integrated intensities of three (00l) reflections were measured using the Lγ1 and Lβ2 excitation lines from a tungsten x-ray source. Calculations that included the effects of anomalous dispersion were compared with the measurements to identify the polarity. Each epitaxial layer had a single polarity rather than a mixture of oppositely polarized grains. However, both A- and B-oriented layers were observed. The method also provides a nondestructive estimate of the layer thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102200
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  • 3
    Electronic Resource
    Electronic Resource
    Above room temperature near ultraviolet lasing from an optically pumped GaN film grown on sapphire (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1-3 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optically pumped near ultraviolet lasing from single-crystal GaN grown by metalorganic chemical vapor deposition has been achieved over a temperature range from 10 K to over 375 K by using a side-pumping geometry on small barlike samples. The laser emission threshold was measured as a function of temperature and the threshold was found to show weak temperature dependence: ∼500 kW/cm2 at 10 K and ∼800 kW/cm2 at room temperature (295 K) for one particular sample studied. The longitudinal lasing modes were clearly observed. The characteristics of the temperature dependence of the laser emission threshold suggests that GaN is a suitable material for the development of optoelectronic devices required to operate at high temperatures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114222
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  • 4
    Electronic Resource
    Electronic Resource
    Time-resolved exciton luminescence in GaN grown by metalorganic chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2512-2514 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of time-resolved studies on the exciton radiative decay in single-crystal GaN films grown by metalorganic chemical vapor deposition. Time-resolved photoluminescence (PL) measurements were performed on the samples at various temperatures from 10 to 320 K. The well-resolved near-band-edge luminescence features associated with free excitons and bound excitons in the GaN allow us to unambiguously determine their decay times. We found that the nonradiative recombination processes play an important role and dominate the decay of exciton population. The processes depend on the density of defects and impurities in the GaN samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114442
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure-dependent photoluminescence study of wurtzite GaN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3492-3494 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature photoluminescence (PL) in single-crystal GaN films grown on sapphire substrates by metalorganic chemical vapor deposition has been studied as a function of applied hydrostatic pressure using the diamond-anvil-cell technique. The PL spectra of the GaN at atmospheric pressure were dominated by two sharp, strong, near-band-edge exciton luminescence lines and a broad emission band in the yellow spectral region. The exciton emission lines were found to shift almost linearly toward higher energy with increasing pressure. While the yellow emission band showed a similar blue shift behavior under applied pressure, a relatively strong sublinear pressure dependence was observed. By examining the pressure dependence of the exciton emission structures, the pressure coefficient of the direct Γ band gap in the wurtzite GaN was determined. The value of the hydrostatic deformation potential of the band gap has also been deduced from the experimental results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113774
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature dependence of interband transitions in GaN grown by metalorganic chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 985-987 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interband transitions in single-crystal GaN films grown by metalorganic chemical vapor deposition (MOCVD) have been studied as a function of temperature (15≤T≤300 K) by reflectance and photoluminescence measurements. At low temperatures, well-resolved spectral features corresponding to the GaN band structure were observed. The energies of the excitonic interband ΓV9−ΓC7,ΓV7 (upper band)−ΓC7 and ΓV7(lower band)−ΓC7 transitions are found to be 3.485, 3.493, and 3.518 eV at 15 K, respectively, for the MOCVD GaN. The spectral features are broadened and shift to lower energy as temperature increases. At room temperature (300 K), the ΓV9−ΓC7and ΓV7 (upper band) −ΓC7 transition energies of this wide band-gap material are determined to be 3.420 and 3.428 eV, respectively. The temperature dependence of these two transitions have been determined using the Varshni empirical relation. Our results yield E0(T)=3.486–8.32×10−4 T2/(835.6+T) eV for the ΓV9−ΓC7 transition and E0(T)=3.494–10.9×10−4 T2/(1194.6+T) eV for the ΓV7 (upper band) −ΓC7 transition. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113820
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  • 7
    Electronic Resource
    Electronic Resource
    Picosecond four-wave-mixing in GaN epilayers at 532 nm (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 587-589 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulsed probe degenerate four wave mixing experiments were performed on GaN epilayers using 13 ps pulses at 532 nm. Intensity and time response of the scattering efficiency was studied. Intensity dependence of the observed signal suggests carrier generation by both single and two photon effects. The absolute scattering efficiency was measured and related to pump-induced nonlinear index change. The nonlinear refractive coefficient found was 1×10−3 cm2/GW which is greater than an order of magnitude larger than the expected value. Time response of the signal was found to be dictated by carrier lifetimes. Double-exponential decays to trap levels with lifetimes of 100 ps and 1.1 ns are suggested as the dominant recombination processes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116476
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanisms of band-edge emission in Mg-doped p-type GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1883-1885 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved photoluminescence has been employed to study the mechanisms of band-edge emissions in Mg-doped p-type GaN. Two emission lines at about 290 and 550 meV below the band gap (Eg) have been observed. Their recombination lifetimes, dependencies on excitation intensity, and decay kinetics have demonstrated that the line at 290 meV below Eg is due to the conduction band-to-impurity transition involving shallow Mg impurities, while the line at 550 meV below Eg is due to the conduction band-to-impurity transition involving doping related deep-level centers (or complexes). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116282
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  • 9
    Electronic Resource
    Electronic Resource
    Ueber Atrophie und Hypertrophie der Muskelfasern des Herzens (1886)
    Springer
    Virchows Archiv 103 (1886), S. 88-130 
    Details
    ISSN: 1432-2307
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01878568
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