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  • 1
    Electronic Resource
    Electronic Resource
    In situ YBa2Cu3O7−x superconductor films on GaAs/AlAs superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5108-5110 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting YBa2Cu3O7−x films have been deposited in situ onto III-V superlattice substrates. The substrates were GaAs/AlAs superlattices grown by molecular beam epitaxy onto GaAs substrates. For 5000-A(ring) -thick YBCO films grown at 615 °C substrate temperature, we have obtained Tc of 73 K. For thinner films the Tc's are lower, indicating poor interfaces. However, the onset of the superconducting transition is 90 K in all cases. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy (TEM) show these films to be polycrystalline. TEM shows an interaction layer of about 1000 A(ring) at the interface. Low-temperature cathodoluminescence measurements of the substrate show that atomic interdiffusion has intruded at least 5000 A(ring) below the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349020
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  • 2
    Electronic Resource
    Electronic Resource
    Electron states in mesa-etched one-dimensional quantum well wires (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2849-2853 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional, self-consistent solutions of the Schrödinger and Poisson equations are used to find the electron states in GaAs/AlGaAs quantum well wires. Both deep and shallow mesa structures are simulated. Our results show that while these structures are capable of providing the single occupied subband and wide energy separations needed for a true quantum wire, the process tolerances allowed are very small, on the order of 200 A(ring) of width variation. Cutoff widths calculated are 1000 A(ring) for the shallow mesa and 2100 A(ring) for the deep mesa. The agreement with experimental results is good for the shallow mesa, but poor for the deep mesa. This suggests additional process-induced sidewall depletion mechanisms contributing to the cutoff of the deep mesa structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346443
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  • 3
    Electronic Resource
    Electronic Resource
    Large subband spacings in δ-doped quantum wires (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5922-5924 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum wire subband separations of 15 meV have been calculated in delta-doped structures using self-consistent, two-dimensional, solutions of the Poisson and Schrödinger equations. δ-doped layers are used to provide the high charge concentrations needed to obtain lateral confinement, while avoiding parasitic conduction paths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346920
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  • 4
    Electronic Resource
    Electronic Resource
    A self-consistent solution of Schrödinger–Poisson equations using a nonuniform mesh (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4071-4076 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent, one-dimensional solution of the Schrödinger and Poisson equations is obtained using the finite-difference method with a nonuniform mesh size. The use of the proper matrix transformation allows preservation of the symmetry of the discretized Schrödinger equation, even with the use of a nonuniform mesh size, therefore reducing the computation time. This method is very efficient in finding eigenstates extending over relatively large spatial areas without loss of accuracy. For confirmation of the accuracy of this method, a comparison is made with the exactly calculated eigenstates of GaAs/AlGaAs rectangular wells. An example of the solution of the conduction band and the electron density distribution of a single-heterostructure GaAs/AlGaAs is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346245
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  • 5
    Electronic Resource
    Electronic Resource
    X-ray reciprocal-space mapping of strain relaxation and tilting in linearly graded InAlAs buffers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3578-3584 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The extent of relaxation and orientation of linearly graded InxAl1-xAs (x=0.05–0.25) buffers grown on GaAs were examined using a novel x-ray diffraction reciprocal-space mapping technique (kmap). Samples were grown at temperatures ranging from 370 to 550 °C. The fractional relaxation of the buffers grown between 470 and 550 °C was essentially identical (77%) and symmetric in orthogonal 〈110〉 directions. These buffers are believed to be in equilibrium indicating that the incomplete relaxation is not a kinetic effect. The extent of relaxation was less than that expected for equilibrium relaxation in the absence of dislocation–dislocation interactions indicating that such interactions must be considered to accurately predict the extent of relaxation. The saturation of the relaxation as a function of temperature indicates that at the grading rate used (8% In/μm or 0.69% strain/μm), we are not working in a growth regime where the relaxation is nucleation limited. In addition, all the buffers are slightly tilted with respect to the GaAs substrate about [11¯0] toward the [110] direction suggesting either a bias in the dislocation types in the boule-grown GaAs, or a bias in the way in which α and β dislocations interact with unintentional substrate miscuts. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361410
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  • 6
    Electronic Resource
    Electronic Resource
    Measurements and analysis of Hall effect of a two dimensional electron gas in the close proximity of a superconducting YBa2Cu3O7−x film (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3562-3565 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A direct integration of YBa2Cu3O7−x and a two dimensional electron gas Hall probe was made possible through the use of a MgO buffer layer. We demonstrate the use of this structure for the measurements of the magnetization hysteresis of a superconducting YBa2Cu3O7−x thin film, and we make an estimate of the sensitivity and resolution that can be achieved with this probe structure. The close proximity of the YBa2Cu3O7−x to the two dimensional electron gas (∼1700 A(ring)) allows sensitive measurements of interactions between the two; more importantly, closer superconductor-semiconductor spacing can be achieved without severe compromise of the component material quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357415
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  • 7
    Electronic Resource
    Electronic Resource
    Emission mechanisms of bulk GaN and InGaN quantum wells prepared by lateral epitaxial overgrowth (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1460-1462 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The emission mechanisms of bulk GaN and InGaN quantum wells (QWs) were studied by comparing their optical properties as a function of threading dislocation (TD) density, which was controlled by lateral epitaxial overgrowth. Slightly improved excitonic photoluminescence (PL) intensity was recognized by reducing TD density from 1010 cm−2 to less than 106 cm−2. However, the major PL decay time was independent of the TD density, but was rather sensitive to the interface quality or material purity. These results suggest that TDs simply reduce the net volume of light-emitting area. This effect is less pronounced in InGaN QWs where carriers are effectively localized at certain quantum disk size potential minima to form quantized excitons before being trapped in nonradiative pathways, resulting in a slow decay time. The absence of any change in the optical properties due to reduction of TD density suggested that the effective band gap fluctuation in InGaN QWs is not related to TDs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123581
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  • 8
    Electronic Resource
    Electronic Resource
    Low-temperature-grown GaAs enhanced wet thermal oxidation of Al0.98Ga0.02As (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2624-2626 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of incorporating low-temperature-grown GaAs (LT GaAs) into the layer structure of Al0.98Ga0.02As/GaAs are studied. Results show that the structures containing a 300 nm layer of LT GaAs have faster oxidation rates and lower oxidation temperatures compared to reference samples without the LT GaAs layer. This letter will discuss the mechanisms involved in the oxidation rate increase, attributed to the LT GaAs enhancing the transport of As species during the oxidation process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122526
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of high-quality InGaN/GaN multiquantum wells with time-resolved photoluminescence (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1066-1068 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recombination in single quantum well and multiquantum well InGaN/GaN structures is studied using time-resolved photoluminescence and pulsed photoluminescence measurements. Room-temperature measurements show a rapid lifetime (0.06 ns) for a single quantum well structure, while an increasingly long decay lifetime is measured for multiquantum wells as more quantum wells are incorporated into the structure. Temperature-dependent lifetime measurements show that a nonradiative recombination mechanism activates above 45 K in the single quantum well but is less important in the multiquantum wells. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120966
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  • 10
    Electronic Resource
    Electronic Resource
    Near-field scanning optical spectroscopy of an InGaN quantum well (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 927-929 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Near-field scanning optical microscopy is used to image photoluminescence (PL) in an InGaN/GaN quantum well (QW) with spatial resolution of approximately 100 nm for temperatures between 50 and 295 K. Strong (∼50%) fluctuations in the quantum well photoluminescence as well as a tenfold enhancement of deep level-related emission at lower energies occur at large (∼500 nm diam) pits in the heterostructure. Regions of smaller (∼15%) fluctuations in the QW PL are not correlated with the presence of pits. The spectrum of the QW PL shows no significant variations on the length scales probed in this experiment. We thus find no spectroscopic signature of the recombination of strongly localized carriers at temperatures above 50 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120875
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