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  • American Institute of Physics (AIP)  (3)
  • 1995-1999  (3)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Structural transformations and strain relaxation mechanisms of In0.6Ga0.4As islands grown by molecular beam epitaxy on GaAs(001) substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3824-3832 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shape transformations and the mechanism of misfit strain relaxation of In0.6Ga0.4As islands grown at different temperatures on GaAs(001) substrates have been investigated. Layers with a constant nominal thickness of 12 monolayers were deposited by molecular beam epitaxy on nominal singular and on vicinal substrates. The specimens were characterized by scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. It is shown that an increase of the growth temperature yields a shape transition from rounded islands to elongated cigar-like structures. The lattice-parameter mismatch in the circular islands is relaxed by misfit dislocations at lower growth temperatures. Indium desorption effectively reduces the mismatch at higher growth temperatures and therefore yields the nucleation of coherent islands. In spite of this structural transformation an Arrhenius-like behaviour of the island densities is observed with an activation energy which depends on the substrate tilt. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359897
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of composition fluctuations on an atomic scale in Al0.25Ga0.75N by high-resolution transmission electron microscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 930-932 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Composition fluctuations in the Al0.25Ga0.75N layer of an AlGaN/GaN transistor structure grown by plasma induced molecular beam epitaxy on Al2O3(0001) at a growth temperature of 870 °C were studied by digital analysis of lattice images (DALI) of high-resolution transmission electron microscopy (HRTEM) cross-section images. DALI exploits the linear dependence of the lattice parameters on the Al content by applying Vegard's law. Detecting the distances between intensity maxima positions in the micrograph which can be considered as a fingerprint of the local lattice parameters quantitatively derives composition profiles on an atomic scale. In the HRTEM cross-section image different areas were observed in the Al0.25Ga0.75N layer with either homogeneous or "striped" contrast. In the striped areas the analyses indicate a strong periodic decomposition with a period of 1 nm consisting of 1 ML Al0.8Ga0.2N and about 3 ML Al0.07Ga0.93N. The regions with homogeneous contrast do not exhibit significant composition fluctuations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122041
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  • 3
    Electronic Resource
    Electronic Resource
    Composition evaluation of InxGa1−xAs Stranski-Krastanow-island structures by strain state analysis (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3868-3870 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The compositional analyses of InxGa1−x/GaAs (001) island structures grown by molecular beam epitaxy at a substrate temperature of 560 °C with nominal In contents of x=60% and 100% are presented on the basis of high resolution transmission electron microscopy micrographs. The linear dependence of the lattice parameter on the In content (Vegard's law) is exploited to quantitatively derive composition profiles on an atomic scale by measuring local lattice parameters and displacements. The relaxation of the thin transmission electron microscopy specimen is taken into account by the accurate thickness determination using the quantitative analysis of the information from transmission electron micrographs procedure. The final evaluation step consists of finite element modeling with the appropriate sample geometry, where the In distribution is chosen to obtain the best fit between experimental and simulated displacements. The observed In content is significantly smaller than the nominal In concentration which is due to segregation of In and diffusion of Ga from the GaAs buffer into the island during the growth. The measured mean In concentration of the islands with a nominal In content of 60% (100%) is 24% (45%). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120528
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