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  • 1
    Electronic Resource
    Electronic Resource
    Photothermal luminescence spectroscopy of GaAs/AlxGa1−xAs quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4555-4559 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel luminescence technique named photothermal luminescence has been developed. For the photothermal luminescence spectroscopy, the emission signal is caused by electronic transitions via the absorption of photons, followed by thermal excitation via electron-phonon interactions, and is monitored as a function of the excitation photon energy, in which the excitation photon energy is less than that of the emission signal. This new technique has been applied to the study of electronic transitions in GaAs/AlxGa1−xAs quantum wells. In addition to the observation of the n=1 electron-heavy-hole 1s and 2s exciton recombinations, a previously unreported fine structure in the n=1 electron-heavy-hole 1s exciton spectrum has also been observed. By measuring the temperature dependence of the spectra on different quantum wells, we suggest that the fine structure is due to the formation of the standing waves of acoustic vibrations in GaAs/AlxGa1−xAs quantum wells. We emphasize that due to the underlying mechanism of the technique, the photothermal luminescence provides a powerful tool to investigate the processes of electron-phonon interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352770
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  • 2
    Electronic Resource
    Electronic Resource
    Photoluminescence studies of hydrogen passivation of GaAs grown on InP substrates by molecular-beam epitaxy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3360-3362 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen passivation of GaAs grown on InP substrates by molecular-beam epitaxy has been performed. Photoluminescence studies show that two peaks at 1.503 and 1.462 eV, which have the luminescence intensities in heteroepitaxial GaAs stronger than that in homoepitaxial GaAs, are effectively passivated by atomic hydrogen. The copper-arsenic vacancy complex associated recombination is also eliminated after hydrogenation. However, hydrogenation can enhance the intensity of donor to C(As) acceptor transition. In addition, we show that the damaged surface during hydrogenation using rf glow-discharge method can be passivated by the hydrogenation using photochemical vapor deposition system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348533
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  • 3
    Electronic Resource
    Electronic Resource
    Optical study of high density two-dimensional electron gas in GaAs/Al0.3Ga0.7As modulation-doped quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 647-650 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the optical properties of high density electron gas in GaAs/Al0.3Ga0.7As modulation doped quantum wells by using the photoluminescence measurements with the pumping photon energies above and below the band gap of the barrier and the resonant Raman scattering. We point out that the previous assignment of the transition between the second conduction subband and the ground-state heavy-hole subband in the photoluminescence spectra may be flawed. Thus, there is no large breakdown of the parity selection rule of the optical matrix element in quantum wells even if the carrier concentration is as high as 1012 cm−2. Our results are consistent with the theoretical investigation. We have also estimated the band gap shrinkages due to many-body interactions, which are comparable with the previous calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351847
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of hydrogenation on deep-level traps in InP on GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 509-511 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep levels in the heteroepitaxial undoped InP layers grown directly on GaAs substrates by organometallic vapor-phase epitaxy have been investigated by deep-level transient spectroscopy. Two electron traps have been observed with activation energies of 0.4 and 0.57 eV in the temperature range between 150 and 310 K. The trap concentrations of these levels are in the order of 1015 cm−3 for samples with a carrier concentration of 1016 cm−3. Incorporation of atomic hydrogen into the InP layer by a photochemical vapor deposition system produces substantial decreases of the trap concentrations to 1014 cm−3 and of the carrier concentration to 1015 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350687
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  • 5
    Electronic Resource
    Electronic Resource
    Above-barrier states in GaAs–AlGaAs superlattices studied by photoconductivity and photoreflectance (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1460-1462 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that the quasibound states at the above-barrier region in AlGaAs–GaAs superlattices can be clearly observed at room temperature by photoconductivity as well as photoreflectance measurements. We provide concrete evidence to confirm that free-carrier confinement at barrier layer does exist. It is also found that the barrier-width dependence of the above-barrier transition energies can be described quite well by the modified Messiah's calculation. However, the simple calculation using the constructive interference condition can only explain the transitions at lower energies, and fails with increasing transition energy. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370965
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  • 6
    Electronic Resource
    Electronic Resource
    AlxGa1−xN/GaN band offsets determined by deep-level emission (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1887-1890 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present studies of the compositional dependence of the optical properties of AlxGa1−xN(0〈x〈0.22) alloys by modulation spectroscopy and photoluminescence. The yellow luminescence, which is well known in GaN and is generally assigned to shallow donor–deep acceptor pair recombination has also been observed in AlxGa1−xN. As aluminum concentration increases, the color of the band changes from yellow (2.2 eV) to blue (2.6 eV). The shift was less than that of the band gap. Together with previously published studies, it implies that the deep acceptor level is pinned to a common reference level to both materials, thus the deep level responsible for the yellow emission is used as a common reference level to determine the band alignment in AlxGa1−xN/GaN heterojunctions. Combining with the near-band-edge modulation spectra, the estimated ratio of conduction-to-valence band discontinuity is 65:35. Our results are close to the values obtained from PL measurements on Al0.14Ga0.86N/GaN quantum wells and those calculated by linear muffin-tin orbital method and linearized augmented plane wave method. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383259
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  • 7
    Electronic Resource
    Electronic Resource
    Dielectric studies of Zn1−xMnxSe epilayers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1630-1633 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the dielectric properties of Zn1−xMnxSe(0≤x≤0.78) epilayers, by capacitance and dissipation factor measurements at temperature 5 K〈T〈475 K and frequency 20 Hz〈f〈100 kHz. A Debye-like relaxational contribution to the dielectric response is observed, which requires the presence of charge redistribution. The relaxation is found to be a thermally activated process, and the activation energies obtained from the dissipation factor and capacitance are in good agreement. The capacitance is found to increase with a decrease in test frequency. From our results it is established that the dielectric response is caused by carrier hopping among structural defects. A monotonic variation is found in the relationship between the activation energy and the Mn concentration. This monotonic variation is interpreted in terms of the four-center model, in which the number of Mn atoms appearing in the nearest-neighbor sites of the defect can have four possible configurations. The measured defect behavior reflects the overall average of all energy levels involved in the center, and the result is weighted by the relative concentrations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370938
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlinear behaviors of valence-band splitting and deformation potential in dilute GaNxAs1−x alloys (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1446-1449 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance and piezoreflectance investigations have been performed on a series of GaNAs layers grown by low-pressure metal-organic chemical vapor deposition on Si-doped GaAs substrate. In addition to the observation of the fundamental band-gap and spin-orbit splitting, the valence-band splitting in thin GaNxAs1−x epilayers strained coherently by the GaAs substrate is observed in these modulation spectra. Comparing photoreflectance with piezoreflectance spectra, we clearly establish the transitions involving the heavy-hole and light-hole bands. We find that the valence-band splitting increases with increasing nitrogen composition, and it decreases with increasing temperature. We point out that the underlying origin of our observation can be attributed to the effect of lattice mismatch between GaNAs film and GaAs substrate. We also find that the deformation potential of GaNxAs1−x does not follow the linear interpolation of those for GaAs and GaN. It shows a strong composition dependence with a bowing in the small composition. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1488240
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  • 9
    Electronic Resource
    Electronic Resource
    Dielectric studies of Cd1−x−yZnxMnyTe crystals (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4476-4479 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the dielectric properties of Cd1−x−yZnxMnyTe alloys studied by capacitance and dissipation factor measurements at temperature 5 K〈T〈475 K and frequency 20 Hz〈f〈1 MHz. A Debye-like relaxation of dielectric behavior has been observed, which is found to be a thermally activated process. The activation energies obtained from the capacitance and dissipation factor measurements are in excellent agreement. By means of our measurements, it is believed that the dielectric character of the carrier hopping among structural defects is responsible for the observed Debye relaxation. The relationship between the activation energy and Zn concentration has been established. The results are described by the four-center model, in which the number of Zn atoms appearing in the nearest-neighbor sites of a defect can have four possible configurations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351006
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  • 10
    Electronic Resource
    Electronic Resource
    Optoelectronic properties of ZnSe/ZnMgSSe multiple quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3725-3729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optoelectronic properties of undoped ZnSe/ZnMgSSe multiple quantum wells (MQWs) grown by molecular beam epitaxy on (001) GaAs substrates have been investigated by photoluminescence, photoconductivity, and persistent photoconductivity (PPC) measurements. The features related to the band-to-band excitonic and impurity-related transitions of ZnSe/ZnMgSSe MQWs are observed and discussed. In addition, the parameters that describe the temperature dependence of the interband transition energy and broadening function of the excitonic feature are evaluated. PPC has been observed in undoped ZnSe/ZnMgSSe MQWs. The decay kinetics of the PPC effect can be described by a stretched-exponential function, Ippc(t)=Ippc(0)exp[−(t/τ)β], (0〈β〈1). Through the study of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different ZnSe well width, we identify that the carrier excitation from the defect level in ZnMgSSe barrier layer into the ZnSe well layer is the origin of the PPC effect in ZnSe/ZnMgSSe MQWs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350416
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