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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3691-3696 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 736-738 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report pressure-dependent photoluminescence (PL) measurements on ZnSe single crystals grown by the seeded physical vapor phase transport technique. Two kinds of ZnSe samples, the as-grown and Zn-extracted single crystals were used in this study. The Id1 line is the predominant spectral feature for the as-grown samples and shifts with pressure at a rate of 7.3 meV/kbar. The I3 emission dominates the PL spectra of the Zn-extracted samples and has a pressure coefficient of 6.6 meV/kbar, which is inconsistent with the assumption of the I3 line originating from the recombination of the excitons bound to ionized donors.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1-3 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1071-1073 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied laser action of ZnSe and ZnS0.05Se0.95 samples grown by seeded physical vapor phase transport (SPVT) technique in the near resonant two-photon absorption regime. The two-photon pumped lasing was observed using a tunable near-infrared nanosecond laser (830–890 nm). Blue lasing could be observed up to 200 K and the two-photon pumped lasing threshold was measured to be ∼7 MW/cm2 at 10 K. This work demonstrates the applicability of using near-infrared diode lasers as pumping sources to excite the ZnSe-based materials. By comparing the energy position of two-photon pumped lasing with that of the one-photon pumped lasing and examining the red shift of the energy position, we suggest that the free-exciton free-exciton scattering and resultant band filling are the dominant processes involved in the lasing action of ZnSe and ZnSSe alloy crystals at low temperature.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 926-928 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photopumped lasing of ZnS0.05Se0.95 alloys grown by seeded physical vapor-phase transport technique is observed at room temperature for the first time. This is achieved with the excitation photon energy tuned close to the band gap. The longitudinal lasing modes are well resolved. This work demonstrates that ZnSxSe1−x alloys can be used as an alternative to ZnSe in blue light-emitting device fabrications.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1681-1683 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optically pumped lasing of (111) oriented bulk ZnSe grown by seeded physical vapor phase transport (SPVT) technique has been achieved at room temperature under near resonant pumping with the excitation photon energy very close to the fundamental band gap. Laser emission can be seen at a pumping intensity as low as 7 kW/cm2. The lasing mode spacings resulting from the dispersion of the index of refraction for ZnSe in a Fabry–Perot resonator-like cavity have been observed as well. Our experimental results demonstrate that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 985-987 
    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
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong near-ultraviolet stimulated emission was observed at room temperature in GaN/AlGaN separate confinement heterostructures (SCH) grown by molecular beam epitaxy (MBE) on sapphire substrates. The MBE grown GaN/AlGaN SCH samples exhibited stimulated emission threshold pumping powers as low as 90 kW/cm2 at room temperature under the excitation of a frequency-tunable nanosecond laser system with a side-pumping configuration. This represents an order of magnitude reduction over bulklike GaN. Our results suggest that the carrier confinement and waveguiding effects of the SCH samples result in a substantial decrease in the stimulated emission threshold. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cryobiology 26 (1989), S. 573 
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cryobiology 26 (1989), S. 572-573 
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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