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  • 1
    Electronic Resource
    Electronic Resource
    Virtual-surfactant-induced wetting in strained-layer heteroepitaxy (1993)
    Springer
    Applied physics 56 (1993), S. 91-94 
    Details
    ISSN: 1432-0630
    Keywords: 68.55.−a ; 61.14.Hg ; 82.65.Dp ; 61.50.Cj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We show that surface stoichiometry and growth mode are intimately related for heteroepitaxy of InAs on GaO0.47In0.53As. Under As-stable conditions during molecular beam epitaxy, the high strain of the InAs film induces a morphological phase-transition from layer-by-layer to island nucleation. In contrast, under In-stable conditions without direct As4 flux, islanding is inhibited. The In-stabilized surface imposes limitations to the migration of both As and In adatoms and forces layer-by-layer nucleation, thus acting as a virtual surfactant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351909
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Influence of exciton localization on the quantum efficiency of GaN/(In,Ga)N multiple quantum wells grown by molecular-beam epitaxy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 673-675 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using cathodoluminescence spectroscopy, we investigate the dependence of the transition energy and quantum efficiency of a GaN/(In,Ga)N multiple quantum-well structure on both the temperature and excitation density. A coupled rate-equation model is introduced to explain the experimental results. Polarization field screening has been incorporated in a realistic manner by solving these coupled rate equations self-consistently along with the Schrödinger and Poisson equations. Our study suggests that exciton localization increases the internal quantum efficiency significantly. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493237
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  • 4
    Electronic Resource
    Electronic Resource
    Programmable computing with a single magnetoresistive element (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 425 (2003), S. 485-487 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The development of transistor-based integrated circuits for modern computing is a story of great success. However, the proved concept for enhancing computational power by continuous miniaturization is approaching its fundamental limits. Alternative approaches consider logic elements that are ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02014
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  • 5
    Electronic Resource
    Electronic Resource
    Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 406 (2000), S. 865-868 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Compact solid-state lamps based on light-emitting diodes (LEDs) are of current technological interest as an alternative to conventional light bulbs. The brightest LEDs available so far emit red light and exhibit higher luminous efficiency than fluorescent lamps. If this luminous efficiency ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35022529
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum transmission in narrow ballistic wires containing a superconductor island (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 205-207 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the transmission properties in quantum wires with a superconducting island placed in the center of the channel. The conductance quantization is destroyed, unless the Fermi energies in the quantum wire and the superconductor are identical as a consequence of the single-particle reflection from the normal-conductor–superconductor interface. The conductance exhibits fluctuations due to the quantum interference effect in the island. The fluctuation amplitude is found to depend strongly on the pair potential amplitude in the superconductor. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121756
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  • 7
    Electronic Resource
    Electronic Resource
    Defect-induced Raman scattering in resonance with yellow luminescence transitions in hexagonal GaN on a sapphire substrate (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 365-367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong defect-specific low-frequency peaks are detected in low-temperature Raman spectra of hexagonal GaN grown by molecular beam epitaxy on sapphire substrate. The intensity of these peaks is found to be enhanced by excitation in resonance with yellow luminescence transitions. The validity of the assignment to electronic Raman scattering (ERS), as proposed before for their counterparts in cubic GaN on GaAs [M. Ramsteiner, J. Menniger, O. Brandt, H. Yang, and K. H. Ploog, Appl. Phys. Lett. 69, 1276 (1996)], is confirmed. Our results imply that the observed ERS peaks are related to shallow donors which are not necessarily hydrogenic. One Raman peak at very low frequency (11.7 meV) is alternatively explained by a pseudo-localized vibrational mode. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120738
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  • 8
    Electronic Resource
    Electronic Resource
    A Raman spectroscopic study of the Si, Be, and C incorporation in InxGa1−xAs relaxed layers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4690-4695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The incorporation of high concentrations ((approximately-greater-than)1019 cm−3) of Si, Be, and C in InxGa1−xAs relaxed layers has been studied as a function of In content (x≤0.16) by Raman spectroscopy of local vibrational modes (LVM). The frequencies of the Raman peaks resulting from the convolution of several split modes shift to lower values as the In content is increased, the carbon acceptor (CAs) local mode frequency showing the strongest dependency on x. Features attributed exclusively to the influence of In on second-neighbor sites are identified only in the Si-doped samples. The transverse and longitudinal modes expected from the splitting of a LVM of CAs with one In first neighbor are not observed in layers with x up to 0.085. A new calibration for the BeGa, CAs, and Si-related LVM leads to the conclusion that In increases the total electrical activation of Si and favors its incorporation on group-III sublattice sites. In contrast, no influence of In on the Be or C doping activation has been detected. The analysis of the CAs LVM spectra supports the view that in InxGa1−xAs CAs is preferably surrounded by Ga instead of In atoms for x≤0.085. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359816
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  • 9
    Electronic Resource
    Electronic Resource
    In situ technique for measuring Ga segregation and interface roughness at GaAs/AlGaAs interfaces (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1993-2001 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a method, based on electron diffraction, for measuring the Ga segregation and roughness at GaAs/AlGaAs interfaces. By monitoring the phase of reflection high energy electron diffraction intensity oscillations, we can deduce changes of alloy composition in real time. In particular, we can relate the phase to the extent of As coverage and thereby explain the "forbidden range'' for growth of GaAlAs. We have determined that segregation only occurs at the normal (AlAs on GaAs) interface and have detected Ga persisting on a nominal AlAs surface even after 20 monolayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356324
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon incorporation in GaAs and AlxGa1−xAs layers grown by molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 77-81 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs:C and AlxGa1−xAs:C films, grown by solid-source molecular-beam epitaxy with doping levels beyond 1019 cm−3, have been studied by high-resolution double-crystal x-ray diffraction, Hall-effect measurements, and secondary-ion-mass spectroscopy (SIMS). Comparison between x-ray diffraction and Hall-effect data indicate that carbon is preferentially incorporated as acceptor on As lattice sites both in the GaAs:C and in the AlxGa1−xAs:C films. It was found that the higher the AlAs mole fraction the higher is the concentration of carbon incorporated on As sites (CAs). Moreover, SIMS results showed that the total amount of carbon in the host lattices largely exceeds CAs. Our findings are explained by supposing that carbon atoms are incorporated on As sites and on interstitial sites. Furthermore, it is shown that the carbon interstitial concentration can be reduced growing at higher arsenic flux and higher substrate temperature in GaAs:C as well as in AlxGa1−xAs:C layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355200
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