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  • 1
    Electronic Resource
    Electronic Resource
    Homoepitaxial growth of GaN using molecular beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2195-2198 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, experimental results are presented for the homoepitaxial deposition of a GaN overlayer onto a bulk single-crystal GaN substrate using molecular beam epitaxy. Transmission electron microscopy shows a superior structural quality of the deposited GaN overlayer when compared to heteroepitaxially grown layers. Photoluminescence shows narrow excitonic emission (3.467 eV) and the very weak yellow luminescence, whereas the bulk substrate luminescence is dominated by this deep level emission. These results show that homoepitaxy of GaN can be used to establish benchmark values for the optoelectronic properties of GaN thin films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363112
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of low-temperature AlxGa1−xAs lattice properties using high resolution x-ray diffraction (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4452-4454 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using high resolution x-ray diffraction techniques, we have studied the lattice parameter behavior of low-temperature (LT) AlxGa1−xAs as a function of annealing temperature and aluminum content. Similar to LT GaAs, the as-grown LT AlxGa1−xAs layers exhibit a dilated lattice constant which, upon annealing, contracts to that of "normal'' material. The onset of this contraction in LT Al0.3Ga0.7As, however, is found to occur at an annealing temperature nearly 100 °C higher than that required for LT GaAs. In addition, the relative lattice expansion in the as-grown LT layer is found to be a decreasing function of Al content, ranging from 0.099% for LT GaAs to 0.059% for LT Al0.3Ga0.7As. This is attributed to lower than expected As incorporation in the LT AlxGa1−xAs during growth. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359473
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  • 3
    Electronic Resource
    Electronic Resource
    Annealing dynamics of arsenic-rich GaAs formed by ion implantation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1470-1475 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the annealing temperature dependence of structural and electrical properties in heavily arsenic implanted GaAs which has a similar amount of excess arsenic to low temperature GaAs (LT-GaAs). The fundamental properties of this material are quite similar to those of LT-GaAs. High resolution x-ray diffraction measurements have revealed that it has an increased lattice constant, which is reduced to the value of bulk GaAs by annealing between 300 and 400 °C. Electrical conduction in this material is dominated by hopping between deep states, which is also reduced by annealing above 350 °C. In samples annealed at temperatures ranging from 600 to 850 °C, the dominant electron trap is EL2; it has been confirmed by resistivity measurements with n-i-n structures that the Fermi level is pinned by EL2. In samples annealed below 500 °C, the dominant electron trap is not EL2 but the U-band, although electron paramagnetic resonance measurements show the existence of a large concentration of the ionized arsenic antisite defect (AsGa+). This supports the notion that the U-band is formed by AsGa defects with slightly modified carrier emission properties compared with EL2. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360235
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  • 4
    Electronic Resource
    Electronic Resource
    Native point defects in low-temperature-grown GaAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 279-281 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present structural and electronic data which indicate that the dominant defects in GaAs grown at low temperatures (LT GaAs) by molecular beam epitaxy (MBE) are As antisites (AsGa) and Ga vacancies (VGa), with negligible amounts of As interstitials (Asi). We show that the change of lattice parameter correlates with the concentration of AsGa, and that AsGa alone can account for the lattice expansion. We also show that the total concentration of AsGa has a characteristic second power dependence on the concentration of AsGa in the positive charge state for the material grown at different temperatures. This can be understood provided that VGa defects are the acceptors responsible for the carrier compensation. Our results are consistent with most experimental results and the theoretical expectation from the calculation of defect formation energies. We find that the conclusion may also be true in As-rich bulk GaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114782
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical and structural transformation of sapphire (Al2O3) surface by plasma source nitridation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7909-7913 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The chemical, morphological, and structural characteristics of nitrogen plasma treated c-plane sapphire substrate surfaces were studied by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The plasma treatment was carried out by exposing sapphire substrates (Ts=700 °C) to a flow of 35 sccm of activated nitrogen species generated by a constricted-plasma source for 5–60 min. The emergence of the N 1s peak in XPS indicates nitrogen incorporation in sapphire as soon as after 5 min of nitridation. AFM images show that the sapphire contained a high density of islands after 1 h of nitridation. A thin polycrystalline AlN layer was observed on the nitridated sapphire surface by TEM. Both the thickness of the AlN layer and the N 1s photoelectron peak intensity increase nonlinearly with respect to nitridation time. The nonlinear relationship between the thickness of the nitridated layer and the reaction time suggests the growth of the AlN layer follows a diffusion limited growth mechanism. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370606
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of parameters of deep level defects from numerical fit of deep level transient spectroscopy spectra: Analysis of accuracy and sensitivity to noise (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 244-250 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The numerical fit of deep level transient spectroscopy (DLTS) spectra, used primarily to analyze complex DLTS spectra, is evaluated in terms of the accuracy of measuring deep levels and the sensitivity to noise. It is shown that by using numerical fit of DLTS spectra, the uncertainties in the emission activation energy and the capture cross section of deep level defects can be improved by three to four times over the standard Arrhenius plot method. Two modifications of the fitting procedure are tested: a fit of a DLTS spectrum using one rate window, and a simultaneous fit using five different rate windows. It is shown that simultaneous fit of spectra using different rate windows is significantly more accurate, has noticeably larger convergence radius for the initial values of parameters, and is less sensitive to noise. The advantages of the fitting routine are demonstrated on experimentally obtained noisy DLTS spectra. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148503
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  • 7
    Electronic Resource
    Electronic Resource
    Evaluation of precipitate densities and capture radii from the analysis of precipitation kinetics (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 713-717 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of Ham's law in various forms to analyze precipitate site density is discussed. Ham's law is also applied to situations where the site density is of the same order as the solute concentration. While the results are general, this analysis uses iron precipitation and iron-boron pairing in silicon as example systems. The results of Ham's paper are reviewed and several implementations of Ham's Law are compared and fitted to experimental data. Iron-boron pairing is described using Ham's law and a capture radius of the boron of 6 nm is obtained. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368127
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of the growth temperature and As/Ga flux ratio on the incorporation of excess As into low temperature grown GaAs (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 561-566 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The controlled incorporation of excess As into GaAs grown by molecular beam epitaxy at low growth temperatures (LT-GaAs) is explored. The substrate temperature and the As/Ga flux ratio were systematically varied to investigate the influence of growth parameters on the formation of native defects and structural properties. Near infrared absorption, magnetic circular dichroism of absorption, and slow positron annihilation were applied to determine point defect concentrations of As antisites (AsGa) and Ga vacancies (VGa). Structural properties of as-grown and annealed LT-GaAs layers were investigated by x-ray diffraction and transmission electron microscopy. In a well defined parameter range the lattice expansion of the LT-GaAs layers correlates with the amount of AsGa. The VGa acceptor concentration can quantitatively account for the ionization of the AsGa donors. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366723
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  • 9
    Electronic Resource
    Electronic Resource
    Over-relaxation of misfit strain in heavily carbon-doped GaAs grown by metalorganic molecular beam epitaxy after annealing (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1104-1106 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using double crystal x-ray diffractometry (XRD) and transmission electron microscopy (TEM), the annealing effects on heavily carbon-doped GaAs films were studied. From isochronal annealing, the evolution of compressive strain in carbon-doped GaAs films was observed by XRD. From cross-sectional TEM, unusual misfit dislocations with extra-half planes on the GaAs side were observed in the sample annealed at 900 °C for 30 min in addition to normal misfit dislocations with extra-half planes on the film side. A possible mechanism for the formation of such misfit dislocations is proposed based on the over-relaxation of misfit strain in the film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114975
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of matrix on InAs self-organized quantum dots on InP substrate (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 362-364 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAs self-organized quantum dots in In0.53Ga0.47As and In0.52Al0.48As matrices have been grown on InP substrates by molecular beam epitaxy. The dot size in InGaAs has been found to be 3–4 times larger, but the areal density about an order of magnitude smaller than that in InAlAs. Low-temperature photoluminescence (PL) of the InAs/InGaAs quantum dots is characterized by a narrow (35 meV) PL line as compared to that of InAs/InAlAs quantum dots (170 meV). Quantum dot formation increases the carrier localization energy as compared to quantum well structures with the same InAs thickness in a similar manner for both InAs/InGaAs and InAs/InAlAs structures. The effect of the barrier band gap on the optical transition energy is qualitatively the same for quantum well and quantum dot structures. The results demonstrate a possibility of controlling the quantum dot emission wavelength by varying the matrix composition. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120737
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