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  • 1
    Electronic Resource
    Electronic Resource
    Excitonic properties of isolated nanometer-sized InAs islands in a GaAs matrix (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1980-1983 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Isolated nanometer-sized InAs islands formed in a GaAs matrix by direct epitaxial growth are studied by optical spectroscopy to get information about the energy relaxation processes of the photoexcited system. Two different relaxation mechanisms that depend upon excitation density are identified: At higher density photoluminescence excitation exhibits a strong oscillatory behavior due to separate carrier relaxation, whereas at lower density direct photogeneration of excitons is dominant. Both results ensue from the strong electron–LO-phonon interaction in the system. The study of these well-characterized samples with isolated InAs islands gives insight into the optical properties of quantum dot systems made of this materials system. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360171
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial pulsed laser crystallization of amorphous germanium on GaAs (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2575-2581 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the crystallization of amorphous germanium films on GaAs crystals using nanosecond laser pulses. The structure and composition of the crystallized layers is dominated by nonequilibrium effects induced by the fast cooling process following laser irradiation. Perfect epitaxial films are obtained for fluencies that completely melt the Ge film, but not the substrate. For higher fluencies, partial melting of the substrate leads to the formation of a (GaAs)1−xGe2x epitaxial alloy with a graded composition profile at the interface with the substrate. Since Ge and GaAs are thermodynamically immiscible in the solid phase, the formation of the alloy is attributed to the suppression of phase separation during the fast cooling process. Lower laser fluencies lead to polycrystalline layers with a patterned surface structure. The latter is attributed to the freeze-in of instabilities in the melt during the fast solidification process. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1390312
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  • 4
    Electronic Resource
    Electronic Resource
    Novel plastic strain-relaxation mode in highly mismatched III-V layers induced by two-dimensional epitaxial growth (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2265-2267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using cross-section and plan-view transmission electron microscopy we demonstrate that the initial plastic relaxation of highly mismatched layers grown along [100] is governed by the growth mode. During MBE growth of InAs on GaAs in the Stranski-Krastanov (SK) mode, 60o -type dislocations are generated at the island edges and then glide to the interface to relieve the strain. The resulting interfacial microstructure consists of an inefficient arrangement of misfit dislocations. On the other hand, when InAs is forced to grow in a two-dimensional (2D) mode, only pure edge-type dislocations are generated and they are located exactly at the epilayer/substrate interfacial plane. These results are explained by a different dislocation nucleation mechanism imposed by the planar morphology of the highly strained film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113187
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  • 5
    Electronic Resource
    Electronic Resource
    Green photoluminescence from cubic In0.4Ga0.6N grown by radio frequency plasma-assisted molecular beam epitaxy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1230-1232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the structural and optical properties of a cubic (In, Ga)N/GaN/(Al, Ga)N heterostructure containing a 185 nm thick In0.4Ga0.6N layer which dominates the optical properties of the sample. The phase purity of the structure is verified by means of transmission electron microscopy while the In content is measured by x-ray diffraction and secondary ion mass spectrometry. The room-temperature band gap of the In0.4Ga0.6N layer is determined by transmission and reflectance measurements to be 2.46±0.03 eV. This value agrees with the spectral position of the dominating green photoluminescence at 300 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122136
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of AlN nucleation layers on growth mode and strain relief of GaN grown on 6H–SiC(0001) (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3660-3662 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the growth mode and strain state of GaN layers grown either directly on 6H–SiC(0001) or on thin (5 nm), coherently strained AlN nucleation layers. Using a combination of structural, optical, and vibrational characterization methods, we show that the 3.4% compressive lattice mismatch strain is fully relieved in the former case, whereas in the latter case a significant amount (0.3%) remains even after 1 μm of growth. This finding is clarified by in situ reflection high-energy electron diffraction and transmission electron microscopy. We demonstrate that the strain state of the GaN layer is determined by its growth mode, which in turn is governed by the degree of wetting of the underlayer rather than by lattice mismatch. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123214
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  • 7
    Electronic Resource
    Electronic Resource
    Structural characterization of thin GaN epilayers directly grown on on-axis 6H–SiC(0001) by plasma-assisted molecular beam epitaxy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3869-3871 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural properties of a series of thin (0.2–0.6 μm) GaN epilayers directly grown on 6H–SiC(0001) by plasma-assisted molecular beam epitaxy are studied. X-ray reciprocal space maps of the GaN(0002) reflection reveal negligible inhomogeneous strain within the layer but a comparatively large orientational spread of the GaN c axis. X-ray rocking curve measurements show, however, that this mosaicity steadily decreases with film thickness. In fact, the density of threading defects detected by transmission electron microscopy is found to decrease drastically with the distance away from the GaN/SiC interface, finally reaching a value of less than 5×109 cm−2 at a layer thickness of 0.5 μm. The formation mechanisms of the threading dislocations in the GaN films are discussed in consideration of the specific GaN/SiC interface structure. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122920
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  • 8
    Electronic Resource
    Electronic Resource
    Direct observation of the initial nucleation and epitaxial growth of metastable cubic GaN on (001) GaAs (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 583-585 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the direct observation of the initial nucleation and the resulting microstructure of GaN deposited on GaAs(001) by plasma-assisted molecular beam epitaxy. Using high-resolution transmission electron microscopy, we demonstrate that, despite the extreme lattice mismatch between these two materials, GaN nucleates in the metastable cubic phase with a well-defined orientation relationship to the substrate and a sharp heteroboundary. The preference of the metastable phase in the initial stage of growth is discussed in connection with a coincidence lattice for the epitaxy-induced interface structure of the initial GaN nuclei. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118281
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  • 9
    Electronic Resource
    Electronic Resource
    Critical issues for the growth of high-quality (Al,Ga)N/GaN and GaN/(In,Ga)N heterostructures on SiC(0001) by molecular-beam epitaxy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 4019-4021 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We identify and discuss the essential strategies for the growth of (Al,Ga)N/GaN and GaN/(In,Ga)N heterostructures on SiC(0001) by both plasma-assisted and reactive molecular-beam epitaxy. Substrate preparation, nucleation, and growth conditions are optimized for simultaneously satisfying the requirements of high structural, morphological, optical, and electrical quality. The results demonstrate that molecular-beam epitaxy is a competitive technique for the growth of group-III nitrides. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125524
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  • 10
    Electronic Resource
    Electronic Resource
    Phase-transition-induced residual strain in ferromagnetic MnAs films epitaxially grown on GaAs(001) (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2461-2463 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the atomic interface structure and the residual strain state of ferromagnetic α (hexagonal) MnAs layers on cubic GaAs(001) by means of high-resolution transmission electron microscopy and electron diffraction. Despite the different symmetries of the adjacent planes at the heterointerface and the large and orientation-dependent lattice mismatch, the hexagonal MnAs grows epitaxially on GaAs(001) with the (11¯.0) prism plane parallel to the cubic substrate. The atomic arrangement at the interface, which is defined by the accommodation of the large lattice mismatch, explains this extreme case of heteroepitaxial alignment. The anisotropic residual strain distribution is discussed with respect to the particular process of lattice misfit relaxation in the presence of the ferromagnetic phase transition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1367302
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