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  • 1
    Electronic Resource
    Electronic Resource
    Photoreflectance line shape of excitonic transitions analyzed with a redefined set of fitting parameters (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 500-502 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze experimental and simulated photoreflectance spectra of excitonic transitions in semiconductors with a redefined set of fitting parameters in Aspnes' line shape function. The redefinition, based on a comparison with the first derivative of a Gaussian, allows one to directly relate these parameters to the observed experimental spectrum, making them independent of the exponent m. None of the original information, including the underlying physics involved as determined by m, is lost in this process. The physical significance of the fitting parameters is explained. Their usefulness lie in making line shape fitting easier and the possibility of comparing different sets of samples exhibiting inhomogeneities with regard to their broadening, oscillator strengths, and hence, quality. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1379051
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  • 2
    Electronic Resource
    Electronic Resource
    Fundamental relationship of excitonic photoluminescence intensity with excitation density in semiconductor quantum well structures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4075-4078 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fundamental relationship between excitonic photoluminescence (PL) intensity and excitation intensity in semiconductor quantum well structures is developed. This relationship is further simplified in the regime of low excitation, and used for a fit function of the Arrhenius plot of time-integrated PL intensity. The proposed four fit parameters are definitely correlated to the distinct characteristic quantities of the sample material, which are the binding energy of excitons, the activation energy, the scattering time, and the background concentration in the well. The validity of the model has been confirmed using our experiments. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290708
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  • 3
    Electronic Resource
    Electronic Resource
    Unpinned behavior of the surface Fermi level of GaN detected by photoreflectance spectroscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4315-4318 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoreflectance signal from GaN films is sensitive to the ambient medium. A large decrease in the photoreflectance amplitude is observed, when the ambient medium is changed from air to vacuum. This effect is attributed to ultraviolet-light-induced desorption of oxygen from the sample surface leading to a reduction of the surface barrier height. The effect is absent, when a thin Ti layer is deposited on top of the GaN film. A simple model is used to demonstrate that the surface photovoltage can be strongly reduced with a decrease of the surface barrier height. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373071
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of exciton diffusion and localization on cathodoluminescence imaging of quantum well structures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1211-1216 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of exciton diffusion and localization on the cathodoluminescence (CL) intensity distribution using a scanning electron microscope has been investigated in a single quantum well and a multiple quantum well structure prepared by growth interrupted molecular beam epitaxy. Although of different origin, lateral variations of the exciton confinement energy occur in both samples on a length scale much larger than the exciton Bohr radius. The spectral and spatial CL intensity distribution is substantially influenced by diffusion of excitons to quantum well regions with low exciton confinement energy. The CL micrographs from both quantum well structures exhibit a similar bright/dark pattern with a typical length scale, which is determined by the exciton diffusion length in this material. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358988
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  • 5
    Electronic Resource
    Electronic Resource
    Pseudo-negative photocurrent spectroscopy in GaAs-AlAs superlattices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4197-4202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudo-negative photocurrent spectra, i.e., the appearance of a minimum in photocurrent at an absorption maximum, are experimentally studied at different temperatures and excitation intensities in GaAs-AlAs superlattices on GaAs substrates. Superlattice and substrate are isolated by a thick Al0.3Ga0.7As barrier, but electrically connected through penetrating contacts. A simple model is proposed for the analysis of the conditions which can lead to pseudo-negative photocurrent in this sample configuration. The radiative recombination of the carriers in the superlattice was found to be the main process determining the sign of the photocurrent at an absorption maximum. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361877
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  • 6
    Electronic Resource
    Electronic Resource
    Wannier–Stark localization in asymmetric double-well superlattices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8106-8108 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Wannier–Stark localization of miniband states has been investigated in an asymmetric double-well superlattice. The period consists of 3.4 and 2.0 nm GaAs quantum wells separated by 1.4 nm Al0.15Ga0.85As barriers. Photocurrent spectra at 6 K reveal that the lowest excitonic peak near flat band splits up into eight peaks at moderate electric fields. At very high fields only one peak remains. The observed transitions are attributed to the Stark ladder splitting of the wide-well miniband only. This type of superlattice introduces a new degree of freedom for the tailoring of electro-optic devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362367
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  • 7
    Electronic Resource
    Electronic Resource
    Cathodoluminescence studies of exciton localization in GaAs-AlGaAs single quantum wells (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 396-398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the spectrally resolved cathodoluminescence intensity from a 3.5- nm-thick GaAs-AlGaAs single quantum well prepared by growth interrupted molecular beam epitaxy has been investigated between 5 and 120 K. As the temperature increases, we observe thermally activated carrier transfer from wider quantum well regions to narrower ones. This observation indicates that there is exciton localization within the wider quantum well regions, one or two monolayers larger in width, at low temperatures. The contrast in spectrally resolved cathodoluminescence images of the quantum well is significantly influenced by this exciton localization and therefore does not necessarily reflect the lateral island distribution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359336
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  • 8
    Electronic Resource
    Electronic Resource
    Controllable bistabilities and bifurcations in a photoexcited GaAs/AlAs superlattice (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3845-3847 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-sustained photocurrent oscillations and bifurcation processes have been experimentally investigated in an undoped, photoexcited GaAs/AlAs superlattice by varying the laser intensity. Within a certain range of laser intensities, a bistability of the photocurrent can be observed in the photocurrent versus voltage characteristics. The width of the bistability region can be controlled by varying the laser intensity. In the bistable regime, the photocurrent oscillations disappear via a subcritical Hopf bifurcation with increasing applied voltage. Outside this regime, the transition from oscillations to a static state is a supercritical Hopf bifurcation for lower laser intensities, while at higher laser intensities a homoclinic connection is observed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124199
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  • 9
    Electronic Resource
    Electronic Resource
    Time-resolved electroluminescence spectroscopy of resonant tunneling in GaAs-AlAs superlattices (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2921-2923 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier transport through a resonantly coupled GaAs-AlAs superlattice is investigated by time-resolved electroluminescence. Ultrashort current pulses are used to electrically inject electrons and holes into an externally biased superlattice. The time evolution of the emitted light is recorded, which allows us to directly monitor the temporal development of the carrier transport and the associated dynamics of the electric field. At resonance a strong reduction of the initial rise time of the electroluminescence signal is observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116375
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  • 10
    Electronic Resource
    Electronic Resource
    Sound velocity and index of refraction of AlAs measured by picosecond ultrasonics (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2023-2024 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use picosecond optics techniques to generate and detect acoustic pulses in an epitaxially grown film of AlAs. From the round trip time of the acoustic pulse we find a sound velocity in the [100] direction of 6.4×105 cm s−1. We also show how measurements of this type can be used to determine the refractive index.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100309
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