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  • 11
    Electronic Resource
    Electronic Resource
    Well-width dependence of the ground level emission of GaN/AlGaN quantum wells (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2289-2292 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed a systematic investigation of GaN/AlGaN quantum wells grown on different buffer layers (either GaN or AlGaN) in order to clarify the role of strain, structural parameters, and built-in field in determining the well-width dependence of the ground level emission energy. We find that identical quantum wells grown on different buffer layers exhibit strong variation of the ground level energy but similar well-width dependence. The data are quantitatively explained by an analytic model based on the envelope function formalism which accounts for screening and built-in field, and by a full self-consistent tight binding model. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372175
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  • 12
    Electronic Resource
    Electronic Resource
    Optical and structural properties of ternary alloy AlxGa1−xAs/AlAs multiple-quantum-well structures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1512-1520 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear and nonlinear optical properties of a series of ternary alloy AlxGa1−xAs/AlAs multiple-quantum-well structures have been investigated and related to the multilayer configuration. The direct energy gap was found to scale with the AlAs mole fraction as predicted by Lee and Yuravel [Phys. Rev. B 21, 659 (1980)] and the band offset ratio to depend on the alloy composition. Exciton absorption bleaching was observed at room temperature and the nonlinear absorption cross sections were estimated for the first two confined excitonic states. Finally, the possibility of achieving optical gain for the type-II band alignment along the growth direction as well as in the layer plane is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351718
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  • 13
    Electronic Resource
    Electronic Resource
    Radiative transitions in quaternary In0.52Ga0.18Al0.30As layers grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 898-904 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and optical properties of molecular beam epitaxy-grown In0.52Ga0.18Al0.30As layers (E300 Kg(approximately-equal-to)1.18 eV), suitable for waveguide applications, have been studied by means of high-resolution x-ray diffraction, absorption, photoluminescence, photoreflectance, and high-excitation intensity photoluminescence spectroscopy. The combination of these techniques allowed us to study the free-exciton states, the impurity related transitions, and the formation of a dense electron-hole plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353302
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  • 14
    Electronic Resource
    Electronic Resource
    Room-temperature stimulated emission in optically pumped narrow ZnSe/ZnSxSe1−x multiple-quantum-well structures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4969-4971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature stimulated emission in ZnSe/ZnS0.18Se0.82 multiple-quantum-well structure is reported. An optical excitation threshold around 300 kW/cm2 at 300 K and 8.4 kW/cm2 at 10 K was measured. An unsaturated optical gain coefficient of the order of 5×102 cm−1 has been measured at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352068
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  • 15
    Electronic Resource
    Electronic Resource
    Correlation between the structural and optical properties of polydispersed II–VI quantum dots in glass matrix (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6898-6901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a systematic investigation of the structural and optical properties of polydispersed semiconductor microcrystals in glass. Transmission electron microscope experiments reveal the existence of microcrystals of different radii and size dispersion around the average radius. A simple method is proposed to extract the structural parameters by the Gaussian deconvolution of the size histogram. The presence of a polydispersed dot distribution accounts very well for the observed absorption spectra which exhibit different excitonic features corresponding to the estimated microcrystal sizes. The linewidth of the low temperature photoluminescence spectra is satisfactorily explained by a simple emission-broadening model based on the effective mass approximation which takes into account the dispersion of the quantum dot radius obtained by the transmission electron microscope experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349814
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  • 16
    Electronic Resource
    Electronic Resource
    Free-carrier plasma and optical amplification in undoped and modulation-doped Ga0.47In0.53As/Al0.48In0.52As multiple-quantum-well structures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3821-3828 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a systematic investigation of radiative recombination processes of the free-carrier plasma confined in Ga0.47In0.53As/Al0.48In0.52As multiple-quantum-well structures on InP substrate, either undoped or modulation doped. Photoluminescence under low- and high-excitation intensity, luminescence excitation, and optical gain measurements have been used to study the electronic transitions and the optical amplification in the temperature range 10–300 K. Space-resolved luminescence has also been adopted to distinguish between the spontaneous and the stimulated spectral contributions to the observed luminescence collected along different directions with respect to the [001] growth axis of the heterostructures. Optical gain up to 300 K has been observed in the undoped samples under photoexcitation quasiresonant with the confined states in the quantum wells. The theoretical analysis of the optical gain spectra furnishes quantitative data on the electron-hole plasma ground level. In the n-type modulation-doped samples the application of intense optical pumping allows us to observe the transition from the one-component electron plasma to a two-component electron-hole plasma through the rising of a sharp stimulated emission in the optical spectra. Also in this case we observe optical gain up to room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349186
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  • 17
    Electronic Resource
    Electronic Resource
    Fermi edge singularity in the luminescence of modulation-doped Ga0.47In0.53As/Al0.48In0.52As single heterojunctions (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2195-2197 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Modulation-doped Ga0.47In0.53As/Al0.48In0.52As single heterojunctions have been investigated by means of optical spectroscopy and magnetotransport measurements. Strong radiative recombination of the two-dimensional electron gas (2DEG) with photogenerated holes has been observed. The recombination is not k conserving, since the holes are weakly localized at the heterointerface opposite to the 2DEG region. At low temperature strong Fermi edge enhancement occurs in the luminescence of single heterojunctions with, for example, a dense electron sheet concentration of 2.5×1012 cm−2. The results show clear evidence for the influence of carrier concentration and temperature on the Fermi edge singularity. The linewidths of the luminescence spectra agree well with those estimated from the electron sheet carrier concentrations, which were determined from the Shubnikov–de Haas oscillations, using an ideal 2DEG model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102965
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  • 18
    Electronic Resource
    Electronic Resource
    Nature of the band gap (direct versus indirect) of short-period (GaAs)n/(AlAs)n superlattices grown along the [111] confinement direction (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1233-1235 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on spectroscopic experimental evidence of type II band alignment in a (GaAs)6/(AlAs)6 superlattice grown by molecular beam epitaxy along the (111) direction. This result is in contrast to recent theoretical calculations predicting that the (GaAs)n/(AlAs)n superlattices grown along the (111) direction should be direct for all n's.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103333
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  • 19
    Electronic Resource
    Electronic Resource
    Free versus localized exciton in GaAs V-shaped quantum wires (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 302-305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a systematic investigation of continuous wave and transient photoluminescence in GaAs V-shaped quantum wires as a function of temperature, aimed to the understanding of the radiative recombination mechanism of the ground level (localized versus free-exciton recombination). Exciton localization is observed at low temperatures. Free-exciton polariton transitions are monitored at intermediate temperatures through the square root temperature dependence of the decay time. Exciton localization energy, density of localization centers and exciton intrinsic lifetime have been determined from the theoretical analysis of the transient photoluminescence, thus providing a simple quantitative method for the assessment of sample quality. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366683
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  • 20
    Electronic Resource
    Electronic Resource
    White light emission from blends of blue-emitting organic molecules: A general route to the white organic light-emitting diode? (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 560-562 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that all possible binary combinations of molecules from four different families of organics—a diamine derivative, N,N′-bis(3methylphenyl)-N,N′-diphenylbenzidine, an oxidiazole derivative, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, a substituted thiophene dioxide, 2,5-bis(trimethylsilyl thiophene)-1,1-dioxide, and poly(9-vinylcarbazole)—produce white or near-white emission. We suggest that this is due to exciplex formation, and that this is likely to be a general phenomenon for blends of blue-emitting aromatic organics. This implies that films of spin-coated blends of blue-emitting organics represent a general, simple, and cheap route to white-emitting organic light-emitting diodes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388875
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