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  • 11
    Electronic Resource
    Electronic Resource
    Structural properties of As-rich GaAs grown by molecular beam epitaxy at low temperatures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1881-1883 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs layers grown by molecular beam epitaxy (MBE) at substrate temperatures between 200 and 300 °C were studied using transmission electron microscopy (TEM), x-ray diffraction, and electron paramagnetic resonance (EPR) techniques. High-resolution TEM cross-sectional images showed a high degree of crystalline perfection of these layers. For a layer grown at 200 °C and unannealed, x-ray diffraction revealed a 0.1% increase in the lattice parameter in comparison with bulk GaAs. For the same layer, EPR detected arsenic antisite defects with a concentration as high as 5×1018 cm−3. This is the first observation of antisite defects in MBE-grown GaAs. These results are related to off-stoichiometric, strongly As-rich growth, possible only at such low temperatures. These findings are of relevance to the specific electrical properties of low-temperature MBE-grown GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101229
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  • 12
    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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  • 13
    Electronic Resource
    Electronic Resource
    Schottky barrier instabilities due to contamination (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 145-147 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We reported here a systematic study of the annealing-induced changes in the barrier height of Schottky barrier diodes fabricated on atomically clean and contaminated surfaces. Al, Ag, Au, and Cr/GaAs(110) diodes were fabricated by in situ deposition on clean n-type GaAs(110) surfaces prepared by cleavage in ultrahigh vacuum and on contaminated surfaces prepared by cleavage and exposure to the atmosphere for ∼1–2 h. This study demonstrates that the as-deposited barrier height and the annealing-induced changes in the barrier height of diodes formed with an interfacial layer of contamination are distinctly different from the characteristics of diodes formed on clean semiconductor surfaces. The presence of an interfacial layer of contamination is found to significantly degrade the stability of the diode's barrier height to annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100351
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  • 14
    Electronic Resource
    Electronic Resource
    Aging of Schottky diodes formed on air-exposed and atomically clean GaAs surfaces: An electrical study (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2006-2010 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this report we show that the application of a large voltage and current stress can significantly change the barrier height of a given metal (Ag,Al,Au,Pd,Cr)/GaAs(110) contact. These changes of barrier height depend on the metal used, the method of fabrication of the diode (air exposed or UHV cleaved), and the intensity and direction of the potential and current during the electrical aging. In particular, the air-exposed Ag diodes exhibit the largest change in the barrier height (∼85 meV) upon aging, while the UHV-cleaved Ag diodes do not exhibit a significant change. In the case of Au, both UHV-cleaved and air-exposed diodes show a small change (∼20 meV). The barrier heights of Pd, Al, and Cr air-exposed diodes do not exhibit an appreciable change upon aging (i.e., 〈10 meV). The changes in barrier height are found to have a very consistent and characteristic logarithmic dependence upon time. Once the electrical aging is stopped, the barrier height is found to recover to near the unaged value. The long time constant of the aging process, the ability of the barrier height to recover after aging, the long time constant of the recovery process, and the acceleration of the recovery process by illumination suggest that the changes in the barrier height which occur upon electrical aging are due to the creation and/or annihilation of deep level traps near the interface. We also report a systematic study of a comparison of barrier height determinations for Ag, Al, Au, Cr, and Pd diodes formed on air-exposed and UHV-cleaved GaAs(110) surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341178
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  • 15
    Electronic Resource
    Electronic Resource
    Structures and electronic properties of misfit dislocations in ZnSe/GaAs(001) heterojunctions (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 549-551 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structures and electronic properties of misfit dislocations in ZnSe/GaAs(001) heterojunctions have been studied by transmission electron microscopy, cathodoluminescence (CL), and photoluminescence. In undoped ZnSe epilayers, irregular dislocation segments tending to lie roughly along [100] and [010] directions were observed as well as long straight 60° dislocations along [110] and [11¯0] directions. In N-doped ([N](approximately-greater-than)1×1018 cm−3) ZnSe epilayers, the misfit dislocations were predominantly dissociated into partial dislocations which makes cross slip and formation of irregular dislocations more difficult; only the straight dislocations along [110] and [11¯0] were observed. The CL observations suggest that the irregular dislocations trap carriers more efficiently than the dislocations along 〈110〉.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112293
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  • 16
    Electronic Resource
    Electronic Resource
    Mechanism responsible for the semi-insulating properties of low-temperature-grown GaAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3002-3004 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism responsible for the semi-insulating properties of low-temperature-grown GaAs is investigated by determining the concentration of arsenic antisite (AsGa)-related defects in the material. The concentrations of the defects in neutral and positively charged states, As0Ga and As+Ga, are determined by near-infrared absorption and magnetic circular dichroism of absorption, respectively. Materials grown and annealed at different temperatures are investigated. We find that the defects are abundant in all samples studied, with the concentration of As0Ga higher than that of As+Ga defects. The results indicate that the defects can account for the pinning of the Fermi energy and consequently also the semi-insulating properties of the material. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112490
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  • 17
    Electronic Resource
    Electronic Resource
    Morphological transition of InAs islands on GaAs(001) upon deposition of a GaAs capping layer (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1677-1679 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction between a GaAs cap and InAs islands grown on vicinal GaAs(001) has been studied by transmission electron microscopy and atomic force microscopy. Samples were prepared by molecular beam epitaxy at 480 °C. Upon GaAs cap deposition, it was found that the previously grown InAs islands undergo a novel type of morphological transition, i.e., a transition from disk-shaped to ring-shaped islands. InAs becomes depleted or entirely absent in the central area of what had been a disk-shaped InAs island. The GaAs cap was also shown to be virtually absent within the same central region, resulting in the formation of crater-like surface depressions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112883
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  • 18
    Electronic Resource
    Electronic Resource
    Effects of Al2O3 cap on the structural and electrical properties of Au/Te/Au contacts on an n-type GaAs substrate (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2995-2997 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Au/Te/Au contacts to n-type GaAs were prepared by sequential vapor deposition and subsequently annealed at temperatures in the range 420–480 °C. The structural and electrical characteristics of the contacts were characterized by transmission electron microscopy and current–voltage measurements. We found that the electrical behavior of the contacts depends dramatically on whether they are covered with an Al2O3 cap during annealing. While a cap-annealed Au/Te/Au contact remains rectifying, annealing without the cap results in ohmic behavior. In conjunction with the observed structural properties, this phenomenon can be understood in terms of the doping model for ohmic contact formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109168
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  • 19
    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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  • 20
    Electronic Resource
    Electronic Resource
    Effect of Si doping on the dislocation structure of GaN grown on the A-face of sapphire (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 990-992 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy, x-ray diffraction, low-temperature photoluminescence, and Raman spectroscopy were applied to study stress relaxation and the dislocation structure in a Si-doped GaN layer in comparison with an undoped layer grown under the same conditions by metalorganic vapor phase epitaxy on (11.0) Al2O3. Doping of the GaN by Si to a concentration of 3×1018 cm−3 was found to improve the layer quality. It decreases dislocation density from 5×109 (undoped layer) to 7×108 cm−2 and changes the dislocation arrangement toward a more random distribution. Both samples were shown to be under biaxial compressive stress which was slightly higher in the undoped layer. The stress results in a blue shift of the emission energy and E2 phonon peaks in the photoluminescence and Raman spectra. Thermal stress was partly relaxed by bending of threading dislocations into the basal plane. This leads to the formation of a three-dimensional dislocation network and a strain gradient along the c axis of the layer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117105
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