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  • 1
    Electronic Resource
    Electronic Resource
    Application of "critical compositional difference'' concept to the growth of low dislocation density (〈104/cm2) InxGa1−xAs (x≤0.5) on GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1752-1757 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayer epitaxial structures consisting of InxGa1−xAs layers of various compositions were grown on GaAs substrates by the molecular beam epitaxy technique. Dislocation evolution and residual strain in these heterostructures were studied using cross-sectional transmission electron microscopy (XTEM) and high-resolution x-ray diffraction analyses, respectively. The multilayer heterostructures were designed such that the compositional difference between two adjacent InxGa1−xAs layers in the stack was less than a critical compositional difference of Δx=0.18, taking partial lattice-relaxation into account. XTEM studies of the stacked structures indicated dislocation evolution to be confined to the GaAs substrate and the InxGa1−xAs layers underlying the top InxGa1−xAs layer in the stack, the top InxGa1−xAs layer being essentially dislocation-free. This phenomenon is attributed to a monotonic increase in the yield strength of InxGa1−xAs at the appropriate growth temperatures with increasing values of x. Such behavior appears to persist up to an InxGa1−xAs composition of approximately x=0.5, whereupon a further increase in composition results in dislocation evolution in the top layer of the stack. It is postulated that the yield strength of InxGa1−xAs decreases with increasing values of x beyond x=0.5. Extremely low dislocation density InxGa1−xAs material was grown on GaAs using the stacked structure approach as evidenced by etch pit analysis. For example, dislocation densities of 1–2×103/cm2 and 5–6×103/cm2 were recorded from In0.35Ga0.65As and In0.48Ga0.52As top layers, respectively. Such InxGa1−xAs alloys would be potentially suitable for the fabrication of photonic devices operating at 1.3 μm (x=0.35) and 1.55 μm (x=0.48).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351699
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  • 2
    Electronic Resource
    Electronic Resource
    Growth by molecular beam epitaxy and electrical characterization of Si-doped zinc blende GaN films deposited on β-SiC coated (001) Si substrates (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 91-93 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the electrical characteristics of heavily Si-doped zinc blende GaN epilayers deposited on β-SiC coated (001) Si substrates. The β-GaN films were grown by molecular beam epitaxy using a rf plasma discharge, nitrogen free-radical source, and the doping concentration in the films was controlled over the range 1.5×1018–3.0×1020 cm−3 by suitably adjusting the temperature of a Si effusion cell. We have found that Si incorporation in β-GaN results in a relatively deep donor level (∼62 meV below the conduction band edge at a carrier concentration at room temperature of 1018 cm−3). Also, we present evidence of simultaneous high mobility conduction band conduction (dominant at high temperatures) and low mobility impurity band conduction (dominant at temperatures 〈70 K) in heavily doped (nRT(approximately-greater-than)1019 cm−3) material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113085
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  • 3
    Electronic Resource
    Electronic Resource
    Growth of zinc blende-GaN on β-SiC coated (001) Si by molecular beam epitaxy using a radio frequency plasma discharge, nitrogen free-radical source (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6124-6127 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth of zinc blende-GaN epitaxial films on β-SiC coated (001) Si substrates using a molecular beam epitaxy approach in which the reactive nitrogen species are generated in a remote 13.56 MHz rf plasma discharge, nitrogen free-radical source. We postulate, based on optical emission spectroscopy studies of the remote plasma, that, in our study, nitrogen atoms are the species primarily responsible for efficient nitridation. The zinc blende nature of the GaN films was confirmed by in situ reflection high-energy electron diffraction, ex situ x-ray diffraction, and ex situ low-temperature photoluminescence analyses. Our zinc blende-GaN film growth rates (∼0.3 μm/h) are higher than those reported to date that involve the use of electron cyclotron resonance type reactive nitrogen sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355176
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  • 4
    Electronic Resource
    Electronic Resource
    GaAs substrate cleaning for epitaxy using a remotely generated atomic hydrogen beam (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4610-4613 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ GaAs surface cleaning prior to molecular beam epitaxy using a combined thermal/H-atom treatment, the H-atom flux being derived from a rf (13.56 MHz) plasma discharge, hydrogen free-radical source, has been compared and contrasted to conventional thermal treatment of GaAs surfaces. Surface quality, i.e, morphology, was monitored in situ in real time using conventional reflection high-energy electron diffraction and a diffuse optical reflectivity technique employed simultaneously. GaAs surfaces were found to clean readily at temperatures below 400 °C using the combined thermal/H-atom treatment as opposed to the conventional thermal treatment, which requires temperatures in the vicinity of 600 °C. The atomically clean GaAs surfaces were also found to be specular when prepared using the combined thermal/H- atom treatment in contrast to conventional thermally treated GaAs surfaces, which are considerably rough on the atomic scale, surface roughening in the conventional case being associated with the oxide desorption process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352753
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  • 5
    Electronic Resource
    Electronic Resource
    Dislocations in lattice-mismatched wide-gap II-VI/GaAs heterostructures as laser light scatterers: Experiment and theory (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1203-1209 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is considered in this work that the dislocations that form upon attainment of the critical thickness in lattice-mismatched wide-gap II-VI/GaAs heterostructures can act as laser light scatterers. Experimentally, a near-normal-incidence HeNe laser probe has been employed during epitaxial growth, which generates both a specularly reflected laser light signal as well as a nonspecularly reflected, or scattered, light signal for epilayer thicknesses beyond the critical thickness. It has been determined that the scattered light originates within the bulk of the II-VI epilayer, as opposed to the free surface, based on observation of a π-phase shift between the specular and nonspecular reflections which were monitored simultaneously. A strong correlation has also been observed between the dislocation density as determined postgrowth by transmission electron microscopy analysis of ZnSe/GaAs heterostructures and the optical data (scattered light intensity) recorded in situ during the growth of such heterostructures as a function of epilayer thickness. Theoretically the refractive index perturbations necessary for such scattering have been considered to be the result of strong microelectric fields which surround the dislocations evolving during plastic deformation. Specifically, the field distribution around a dislocation is considered with regard to three different potentials, namely, the deformation potential, the charged dislocation potential, and the piezoelectric potential. The magnitudes of these fields are considered with reference to ZnSe and subsequently the electro-optic effect is evoked in order to argue that a refractive index perturbation (approximately 10−5–10−4) sufficient in magnitude to scatter light could result in the ZnSe/GaAs system as a consequence of such fields. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360358
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  • 6
    Electronic Resource
    Electronic Resource
    Doping of ZnSe during molecular beam epitaxial growth using an atomic phosphorus source (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 490-497 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zinc selenide films were doped with phosphorus during molecular beam epitaxial (MBE) growth by employing a novel, valved, three-zone solid-source radio frequency (rf)-cracker unit manufactured by Oxford Applied Research (OAR). Optical emission spectroscopy analysis of the plasmas produced in the rf chamber of the unit showed that the apparatus was capable of generating a flux of atomic phosphorus. By suitably adjusting the operating conditions of the unit, phosphorus concentrations in ZnSe epilayers were varied over the range of 1×1016 cm−3 to high-1018 cm−3, in a highly controlled and reproducible fashion. Phosphorus atoms, in contrast to P4 molecules, were found to be highly chemically reactive at the growing ZnSe surface at a normal growth temperature (around 300 °C), and the OAR unit was found to be eminently suitable for the provision of atomic P for MBE growth. Doping using atomic P was found, at least in lightly to moderately doped ZnSe, to provide an acceptor state that gave rise to a neutral-acceptor bound exciton emission located at 2.7919 eV, in keeping with that of other substitutional acceptors in ZnSe. Also, compensation in atomic P doped ZnSe appears to occur by virtue of the formation of shallow donor states rather than via the production of deep level states, which dominate in the case of most of the previously reported phosphorus-doped ZnSe studies. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369477
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  • 7
    Electronic Resource
    Electronic Resource
    On epilayer tilt in ZnSe/Ge heterostructures prepared by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1201-1205 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnSe/Ge heterostructures prepared by molecular-beam epitaxy were characterized by "full-rotation'' double-crystal rocking curve x-ray analyses with particular emphasis placed on the measurement of tilt between the (400) planes of ZnSe and Ge. It was found that the value of the tilt angle between such planes depends on both the epilayer thickness and the orientation of the substrate plane. A simple model is proposed in the paper of tilt formation and its development. Steps on the substrate surface are shown to be responsible for a redistribution of the bond lengths between the atoms of the substrate and the epilayer in the interface region leading to the formation of tilt between the planes in the epilayer and the substrate. Particular types of stress in the epilayer are shown to affect the final value of the tilt. It was also found that the structural and optical properties of ZnSe/Ge layers appear to be optimized for Ge substrate surface orientations around 2° off (100)→[110].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341885
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  • 8
    Electronic Resource
    Electronic Resource
    Antimony-doped ZnSe grown by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2851-2853 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Antimony-doped ZnSe layers were grown by molecular-beam epitaxy (MBE) on (100) GaAs substrates using a variety of antimony oven temperatures in the range of 550–800 °C and substrate temperatures in the range of 250–330 °C. Sb concentrations as high as mid-1019 cm−3 were measured in the ZnSe layers by the secondary ion mass spectrometry technique, although an Sb concentration limit of ≤1019 cm−3 was established in this work for the growth of single-crystal Sb-doped material. The Sb incorporation coefficient in ZnSe was found to depend strongly on substrate temperature, increasing from ∼10−2 at 330 °C to ∼1 at 250 °C. In addition, a strong dependence was found of the ZnSe lattice parameters measured normal to the heterointerface on Sb concentration in the layers, the lattice parameter increasing monotonically with increasing Sb concentration. Acceptor bound excitonic emission was not detected from the Sb-doped ZnSe layers by 4.2-K photoluminescence analysis, indicating that Sb incorporation under the MBE growth conditions did not produce a shallow acceptor level in the ZnSe band gap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340937
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the onset of plastic deformation in ZnSe layers grown on (100) GaAs by molecular-beam epitaxy (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2067-2069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnSe layers were grown by molecular-beam epitaxy on (100) GaAs substrates to various layer thicknesses in the range 0.1–2.0 μm. The ZnSe lattice parameter normal to the heterointerface and the ZnSe and GaAs lattice parameters parallel to the heterointerface were measured by the single-crystal x-ray diffractometry technique using the high angle reflections obtained from the (006) and (444) planes. In addition, the heterointerfaces were examined by cross-sectional transmission electron microscopy. It was found that thin ZnSe layers (t〈0.5 μm) grown on GaAs substrates are tetragonally distorted. The layers appear to be elastically strained up to a layer thickness in the range 0.15–0.2 μm whereupon a gradual strain-relief process occurs for layers in the thickness range 0.2≤t≤0.5 μm via the formation of misfit dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338007
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  • 10
    Electronic Resource
    Electronic Resource
    Observation of strain effects and evidence of gallium autodoping in molecular-beam-epitaxial ZnSe on (100)GaAs (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1229-1232 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analysis of the two-electron satellites of the dominant donor-bound exciton line in photoluminescence of ZnSe layers grown on (100)GaAs by molecular-beam epitaxy indicates that the donor impurity is likely gallium. Strain in the ZnSe epitaxial layers as evidenced by a shift in the positions of the excitonic lines is shown to depend on the growth temperature and is a minimum at about 365 °C. At growth temperatures different from 365 °C the IGa20 line is observed shifted by as much as 3 meV. The relatively small shift of ∼0.4 meV in our layers grown at 365 °C may be due to a strain-relief inelastic process; it is suggested that one possibility might be the formation of a misfit dislocation network at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337375
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