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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4175-4181 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A transmission electron microscopy study of the reduction mechanisms for defect densities in epitaxial lateral overgrown (ELO) GaN films is presented. In the standard one step ELO, the propagation of defects under the mask is blocked, whereas the defects in the window regions thread up to the surface. We propose an alternative two step ELO method. In a first step, dislocations close to the edge of the (0001) top facet bend at 90°, thereby producing a drastic reduction in the density of defects above the window. After the coalescence, induced by lateral growth in a second step, dislocations are mainly observed in the coalescence boundaries. The density of defects is decreased to 2×10−7 cm−2 over the entire surface and areas nearly 5 μm wide with 5×106 cm−2 dislocations between the center of the windows and the coalescence boundaries are obtained. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 577-583 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of GaN on 6H–SiC is three dimensional (3D) and results in the formation of large islands presenting hexagonal truncated shape with {1–101} lateral facets and a top {0001} facet. In this work, we present a three steps growth process that enables us to grow high quality mirrorlike GaN layers without using AlN buffer layers. During a first step, a thin 3D GaN layer is deposited at high temperature. This layer is smoothed under ammonia flow for several minutes when the growth is interrupted. The subsequent growth of GaN is two dimensional. 600 nm thick GaN films were grown. They were analyzed by high resolution x-ray diffraction, reflectivity, and photoluminescence. All the layers are under strong tensile biaxial strain. The correlation between residual tensile strain in GaN layers and their optical properties is reported for biaxial deformations cursive-epsilonxx ranging up to 0.37%. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3186-3193 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs and GaAlAs layers doped with different group VI donors (S, Se, Te) have been exposed to hydrogen plasma. By secondary ion mass spectroscopy, it is shown that, as in Si-doped materials, the hydrogen diffusion strongly depends on the AlAs content. Electronic transport measurements indicate that after hydrogen diffusion the electron concentration systematically decreases and their mobility increases, demonstrating clearly the passivation of the group VI donors by hydrogen. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 921-923 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atmospheric pressure metalorganic vapor phase epitaxy is used to perform selective regrowth of GaN on a silicon nitride patterned mask, capping a GaN epitaxial layer deposited on (0001) sapphire substrate. The basic pattern is constituted by a 15 μm period hexagonal array of hexagonal openings in the mask, these openings being circumscribed into 10 μm diam circles. We investigate the effect of Mg incorporation on the growth anisotropy of the localized GaN islands by varying the ratio [Mg]/[Ga] of bis-methylcyclopentadienyl-magnesium and trimethylgallium partial pressures. Both undoped and Mg-doped GaN hexagonal pyramids, delimited by C (0001) and R (1 1¯01) facets, are achieved with a good selectivity. It is found that the GaN growth rates VR and VC, measured in the R〈11¯01〉 and C 〈0001〉 directions respectively, are drastically affected by the Mg incorporation. By adjusting the Mg partial pressure in the growth chamber, the VR/VC ratio can be increased so that the delimiting top C facet does not vanish as usually observed in undoped GaN localized growth, but by contrast expands. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1121-1123 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlxGa1−xAs 0.2〈x〈0.4 epilayers were grown by metalorganic vapor phase epitaxy in the temperature range of 850–950 °C. It has been experimentally shown that epitaxial growth at high temperatures enhances the free-carrier concentration and causes unusual behavior of deep centers for Sn-doped AlxGa1−xAs. From the temperature dependence of the Hall carrier density, and assuming multivalley conduction, an activation energy of the donor of 10 meV was deduced. Furthermore, these samples did not exhibit persistent photoconductivity. Besides, when all parameters of the epitaxy were kept constant, the aluminum fraction in the epitaxial layers slightly increases as the growth temperature increases.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3721-3728 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work discusses the temperature behavior of the various photoluminescence (PL) transitions observed in undoped, n- and p-doped GaN in the 9–300 K range. Samples grown using different techniques have been assessed. When possible, simple rate equations are used to describe the quenching of the transitions observed, in order to get a better insight on the mechanism involved. In undoped GaN, the temperature dependence of band edge excitonic lines is well described by assuming that the A exciton population is the leading term in the 50–300 K range. The activation energy for free exciton luminescence quenching is of the order of the A rydberg, suggesting that free hole release leads to nonradiative recombination. In slightly p-doped samples, the luminescence is dominated by acceptor related transitions, whose intensity is shown to be governed by free hole release. For high Mg doping, the luminescence at room temperature is dominated by blue PL in the 2.8–2.9 eV range, whose quenching activation energy is in the 60–80 meV range. We also discuss the temperature dependence of PL transitions near 3.4 eV, related to extended structural defects. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4518-4523 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic properties of Sn, a well-known group IV n-type dopant in GaAs, were studied in Ga1−xAlxAs alloys for the whole compositional range. These Sn-doped Ga1−xAlxAs epitaxial layers were grown by metalorganic vapor-phase epitaxy; Hall measurements were carried out for values ranging from x=0 to 1, Hall data for 0〈x〈0.4 were interpreted assuming a shallow donor bound to the Γ band, and a deep donor with an ionization energy of about 100 meV. Photoluminescence spectra of selectivity excited donor acceptor pairs show the existence of a deep donor at 100 meV below the Γ minimum for x〉0.2.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2103-2106 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs tunnel p-n junctions with peak current densities up to 45 A cm−2 were grown by metallorganic vapor-phase epitaxy. These tunnel diodes are suitable for intercell ohmic contacts between the case of integrated tandem photovoltaic subcells in solar cells based on GaAs. The peak current is high enough for concentration up to C=1000.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1739-1744 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs epitaxial layers, doped with 119Sn-enriched tin, have been grown by metalorganic vapor-phase epitaxy (MOVPE). 119Sn Mössbauer spectroscopy and Hall measurements have been used to characterize the layers. Three tin species are observed in the as-grown material. One of these is identified as the SnGa shallow donor site and another is associated with electrically inactive Sn sites that may be SnGaSnAs pairs or Sn3As2-like clusters or microprecipitates. The free carrier concentrations (Nd−Na) obtained from the Hall data agree quantitatively with the concentrations of SnGa sites from the Mössbauer data for samples prepared with MOVPE Sn/Ga ratios up to 0.02 and Nd−Na 〈6×1018 cm−3, thereby showing no evidence for compensation up to this doping level. Annealing under arsine creates an acceptor species which is identified as SnGaVGa. High-energy electron irradiation may also produce this compensating acceptor species.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3481-3484 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first direct effective mass measurements of electrons in metalorganic vapor phase epitaxy (MOVPE) Sn-doped Ga1−xAlxAs (x〈0.33) epilayers from Shubnikov–de Haas (SdH) oscillations are reported. The m@B|eΓ values of the conduction band were obtained up to x=0.3. These data, corrected for nonparabolicity, were compared to values calculated by the k ⋅ p model, taking into account the disorder bowing.
    Type of Medium: Electronic Resource
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