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  • 1
    Electronic Resource
    Electronic Resource
    Photovoltage generation in bilayer lipid membrane-cadmium sulfide junctions (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 6783-6790 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100195a047
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of an electric field on exciton recombination in three-step asymmetric coupled quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2105-2109 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The radiative transitions of (100)- and (311)A-oriented three-step asymmetric coupled quantum wells in an electric field are studied by photoluminescence. Four distinct transitions are observed in the spectra which exhibit remarkably complex energy shifts with the applied field. It is shown that these transitions originate from the two pairs of spatially direct and indirect heavy-hole excitons in the three-step quantum well and that their electric-field dependence is dominated by the conversion of the direct into the indirect excitons and vice versa. Furthermore, we discuss the effects of the nonconventional crystal orientation and show that substantial modifications of the basic electro-optical properties can be achieved from internal piezoelectric fields incorporated within the structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356315
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of heteroepitaxy on the width and frequency of the E2 (high)-phonon line in GaN studied by Raman spectroscopy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3634-3641 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wurtzite GaN layers are commonly grown heteroepitaxially on 6H–SiC or Al2O3 substrates, because of the lack of lattice-matched substrates. We study the influence of these substrates mainly on the E2(high)-phonon Raman line by temperature dependent Raman spectroscopy. We find that the line broadening with sample heating is predominantly caused by intrinsic phonon–phonon scattering in GaN. The small three-phonon contribution as well as the small intrinsic linewidth at low temperature are due to the rather low two-phonon density of states at the E2(high)-phonon energy. Substrates with large lattice mismatch cause inhomogeneous strain and defects in the layers, which lead to a large, temperature independent, line broadening. We show that the temperature shift of the E2(high)-phonon frequency is dominated by the GaN lattice expansion. The lattice of epilayers is strongly modified by the thermal in-plane expansion of the substrate. The degree of relaxation at the growth temperature is reflected by deviation of the E2(high)-line from the intrinsic phonon frequency. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347406
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Structural and vibrational properties of (InAs)m(GaAs)n strained superlattices grown by molecular beam epitaxy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 786-792 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and vibrational properties of superlattices composed of many periods of highly mismatched InAs and GaAs layers have been studied by means of x-ray diffraction and Raman scattering as a function of the sample geometry. X-ray diffraction measures the average lattice mismatch between the superlattice and the substrate. The long-range order influences the propagative acoustic phonons whereas strain and confinement effects compete in determining the optic vibration frequencies of the InAs layers. The linewidth of the main superlattice peak in the diffraction patterns and the scattering intensities of the acoustic phonons are related to the actual shape of the interfaces. We find that the stability of the structures depends on the total number of periods, in agreement with the predictions of equilibrium elasticity theory. However, the competition between the different relaxation processes is governed by the individual layer thicknesses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347365
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  • 6
    Electronic Resource
    Electronic Resource
    Comparative analysis of the optical quality of single In0.1Ga0.9As/Al0.33Ga0.67As quantum wells grown by molecular beam epitaxy on (100) and (311) GaAs substrates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1885-1887 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the room-temperature photoluminescence of single In0.1Ga0.9As/Al0.33Ga0.67As quantum wells grown simultaneously on (100), (311)A, and (311)B GaAs substrates. The measurements, taken under both steady state and transient conditions, evidence that nonradiative (Shockley-Read-Hall) recombination dominates the emission of both the [100] and [311]B oriented samples at low injection levels, and is still important up to injection levels approaching those in lasers. The emission of the [311]A oriented sample is, in contrast, dominated by radiative recombination already at modest injection levels. The origin of this remarkable feature of the [311]A oriented sample is traced back to the reduced incorporation of deep recombination centers at the (311)A In0.1Ga0.9As/Al0.33Ga0.67As interface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114365
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  • 7
    Electronic Resource
    Electronic Resource
    Optical phonons of hexagonal and cubic GaN studied by infrared transmission and Raman spectroscopy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 733-735 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using infrared transmission and Raman spectroscopy, we have studied the optical phonon modes of GaN layers grown on GaAs(001) substrates by molecular beam epitaxy. The crystal structure of the GaN layers ranges from predominantly wurtzite to predominantly zincblende depending on the growth conditions. The transverse and longitudinal optical phonons in cubic GaN are found to be at 552 and 739 cm−1, respectively. These frequencies are slightly shifted with respect to the corresponding A1 and E1 phonon modes in hexagonal GaN. The frequency shifts, together with Raman scattering selection rules, can be used for identifying the phase composition of GaN. A more distinct fingerprint of the hexagonal phase is provided by the occurrence of the E2 phonon modes that are spectrally separated from optical phonon modes in the cubic phase and thus uniquely related to the hexagonal phase. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115208
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature measurements behind shock waves using a rapid scanning IR-diode laser (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1294-1298 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature measurements behind shock waves are possible by applying optical methods. In the case of a thermally relaxing system it is generally difficult to measure the translational and vibrational temperatures separately and in a direct way. In the present case, a rapid scanning infrared-diode laser has been used to study the relaxation behavior of a shock heated CO/Ar mixture. The vibrational temperature can be measured by rapid scanning over two or three adjacent rotational lines from different vibrational transitions of CO. In addition it is possible to determine the translational temperature of the gas mixture from the thermal broadening of a single highly resolved rotational absorption line. The experimentally determined vibrational and translational temperature are in reasonable agreement with the computed values based on shock speed measurements and vibrational relaxation data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866244
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  • 9
    Electronic Resource
    Electronic Resource
    Structural properties of GaN layers on Si(001) grown by plasma-assisted molecular beam epitaxy (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3800-3806 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth and microstructure of GaN films deposited on Si(001) substrates by plasma-assisted molecular beam epitaxy. GaN films grown directly on Si(001) are found to be phase mixtured, containing both cubic (β) and hexagonal (α) modifications. The origin of this phase mixture is identified to be due to the formation of amorphous SixNy at the GaN/Si interface during the nucleation stage. Therefore, a GaAs buffer layer is employed to prevent the formation of SixNy. GaN films grown on this GaAs/Si(001) structure are in fact predominantly cubic and exhibit the characteristic band-edge photoluminescence (PL) of β-GaN up to room temperature. However, the PL efficiency from these samples is low compared to that of β-GaN layers directly grown on GaAs(001). We explain the lower PL efficiency by the presence of additional structural defects, which are observed in the GaN/GaAs/Si(001) heterostructure by transmission electron microscopy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367144
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  • 10
    Electronic Resource
    Electronic Resource
    Mg diffusion during metalorganic vapor phase epitaxy of InP (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1017-1019 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion mechanism of Mg has been studied during low-pressure metalorganic vapor phase epitaxy of InP. The Mg dopant profiles were measured by secondary-ion mass spectroscopy. The analysis reveals that abrupt Mg dopant profiles are possible; the Mg diffusion, however, strongly depends on the Mg concentration in the crystal lattice. Simultaneous doping with Si leads to a distinct decrease of the Mg diffusion. This behavior is consistent with a model assuming that Mg diffuses as a complex involving a deep donor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101721
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