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  • 1
    Electronic Resource
    Electronic Resource
    Physical and electrical investigation of ohmic contacts to AlGaAs/GaAs heterostructures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7966-7972 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism by which Ni-Au-Ge metallizations establish electrical contact to the two-dimensional electron gas (2DEG) in modulation-doped AlGaAs/GaAs heterostructures is investigated. Transmission electron microscopy was used to examine samples after electrical characterization by magnetoresistance measurements at cryogenic temperatures. We present a picture in which a 2DEG of reduced electron density exists under the deposited metallization. The success of the contacting procedure is described in terms of the magnitude of this density and the size, areal density, and penetration depth of a series of metallic spikes which establish the electrical link to the 2DEG. We suggest that the electrical behavior is not dominated by the current injection process at the spike/2DEG interface but is instead dictated by scattering from the array of antidots formed by the spikes and by a dependence of the 2DEG density on the size of the metallic pad. The implications of this picture for future nanostructure devices, featuring patterned ohmic metallization smaller than a micron, are discussed and preliminary results are reported. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357908
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum-well intermixing for optoelectronic integration using high energy ion implantation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3697-3705 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The technique of ion-induced quantum-well (QW) intermixing using broad area, high energy (2–8 MeV As4+) ion implantation has been studied in a graded-index separate confinement heterostructure InGaAs/GaAs QW laser. This approach offers the prospect of a powerful and relatively simple fabrication technique for integrating optoelectronic devices. Parameters controlling the ion-induced QW intermixing, such as ion doses, fluxes, and energies, post-implantation annealing time, and temperature are investigated and optimized using optical characterization techniques such as photoluminescence, photoluminescence excitation, and absorption spectroscopy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359948
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  • 3
    Electronic Resource
    Electronic Resource
    Electrodeposition and characterization of magnetic Ni-Fe thin films on InP(100) surfaces (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5795-5799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrodeposited magnetic Ni-Fe films are used in storage devices and are applicable as magnetic sensors. In this work, we demonstrate the electrochemical conditions for deposition of permalloy Ni-Fe nanocrystalline films onto InP(100) surfaces. The prepared Ni-Fe films were analyzed by scanning electron microscopy to determine surface morphology and by Auger electron spectroscopy for compositional depth profiling. Permalloy films with bulk composition of 81% Ni and 18% Fe were obtained by electrodeposition at −1.2 V (versus standard calomel electrode) in a bath of 0.5 M NiSO4, 0.02 M FeSO4, 0.4 M H3BO3, pH=3. Transmission electron microscopy measurements show that these films consist of fcc Ni-Fe nanocrystallites embedded in an amorphous matrix. The films also show good magnetic hysteresis loops, with low coercivity. The magnetic properties of these films are improved by an extended anneal at 100 °C. Interdiffusion occurred between Ni-Fe and the InP substrate after the sample was heated to 300 °C, and consequently a loss of ferromagnetic behavior was observed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359643
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  • 4
    Electronic Resource
    Electronic Resource
    An annealing study of strain relaxation and dislocation generation in Si1−xGex/Si heteroepitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6292-6300 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The generation of interface misfit dislocations, and the accompanying strain relaxation, in a molecular-beam epitaxy grown 0.17 μm thick metastable Si0.82Ge0.18/Si(100) strained epilayer have been studied in detail as a function of rapid thermal annealing treatments over the 500–850 °C temperature range. Charge collection and transmission electron microscopy were used to determine the onset of relaxation by directly imaging misfit dislocations and to investigate the variation in dislocation density with increasing anneal temperature. The strain variation in the epilayer was carefully monitored using double-crystal x-ray diffraction and Raman spectroscopy, and the annealing induced changes in strain related to the electron microscopy observed density of interface misfit dislocations. The relative merit of each experimental technique is discussed in the light of these results. The generation of strain relieving dislocations was found to be an activated process, with an activation energy on the order of 1.5 eV for the Si0.82Ge0.18 epilayer. Preferential surface streaking, along one of 〈110〉 directions, was observed in the relaxed samples despite a nondirectional uniform network of interface misfit dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345146
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of the size, shape, and composition of indium-flushed self-assembled quantum dots by transmission electron microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2272-2277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single and multiple layers of self-assembled InAs quantum dots (QDs) produced by the indium-flush technique have been studied by transmission electron microscopy (TEM) in an effort to develop techniques to reproducibly grow QDs of uniform size and shape. To monitor the changes in QD dimensions, plan-view samples of capped single layers were studied as well as cross-sectional samples of QDs in multiple layers and stacks. The changes in the observed round- and square-shaped QD images under various plan-view TEM imaging conditions, as well as the contrast reversal in the center of QD images viewed in cross-section are modeled using the many-beam Bloch-wave approach, including strain. The sizes and shapes of the QDs are determined through the interpretation of the observed (primarily strain) contrast in plan-view and the observed (primarily atomic number) contrast in cross-sectional TEM. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287226
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  • 6
    Electronic Resource
    Electronic Resource
    Interpretation and modeling of buried InAs quantum dots on GaAs and InP substrates (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1784-1787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Comparisons of buried InAs/GaAs and InAs/InP quantum dots (QDs) utilizing transmission electron microscopy display interesting parallels and differences between the two systems. The higher 7.2% misfit in the InAs/GaAs system produces small (∼20 nm diameter) QDs with a majority displaying a predominately round shape. The lower 3.2% misfit in the InAs/InP system produces larger QDs (∼35 nm diameter) with the majority also displaying a predominately round shape. In both systems, the size of the QDs can be varied by changes in growth procedures and the largest QDs in any population show evidence of faceting © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1384861
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  • 7
    Electronic Resource
    Electronic Resource
    Epitaxial Y1Ba2Cu3O7 thin films on CeO2 buffer layers on sapphire substrates (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3986-3988 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulsed laser deposition has been used to deposit Y1Ba2Cu3O7 layer on CeO2 buffer layers on (11(underbar)02) sapphire. Both layers are epitaxial with the 〈110〉 direction of the CeO2 layer aligned with the 〈2(underbar)021〉 direction of the sapphire substrate. The c-axis Y1Ba2Cu3O7 layer has its 〈100〉 direction alligned with the 〈110〉 direction of the CeO2. Cross-sectional transmission electron microscopy shows the epitaxy to be coherent and the interfaces to be abrupt at an atomic level. The best films have a critical current of 9 × 106 A/cm2 at 4.2 K and lower microwave surface resistance than copper at 77 K and at a frequency of 31 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349166
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial growth of extended solubility CdxPb1−xTe alloys on BaF2 by rf magnetron sputtering (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2430-2432 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial (111)CdxPb1−xTe//(111)BaF2 films in the rocksalt structure have been made by codeposition from CdTe and PbTe magnetron targets in an rf discharge onto chemipolished substrates at 320 °C. Films were prepared with x values from 0 to 0.47, well past the range of bulk thermodynamic solubility. Raman spectroscopy, Auger spectroscopy, and transmission electron microscopy showed phase segregation had not occurred. The lattice spacing in the growth direction was observed to be insensitive to x.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102900
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  • 9
    Electronic Resource
    Electronic Resource
    Structural properties of ultrathin arsenic-doped layers in silicon (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1332-1334 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown δ-doped layers in Si by low-energy As-ion implantation during molecular beam epitaxy. The layers were investigated using cross-sectional transmission electron microscopy, secondary-ion mass spectrometry, Rutherford backscattering, and electrical measurements. The δ-doped layers were between 3.5 and 5.5 nm thick, and showed perfect epitaxy with 50–80% of the incorporated As on substitutional sites. Layers doped at concentrations from 1×1013 cm−2 to 8×1013 cm−2 had bulk-like mobilities and spanned the metal to insulator transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100707
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  • 10
    Electronic Resource
    Electronic Resource
    Coupled InAs/GaAs quantum dots with well-defined electronic shells (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2268-2270 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Artificial molecules are studied using coupled quantum-dot (QD) ensembles with well-defined electronic shells. The coupling strength between the zero-dimensional states is varied by changing the distance between two layers of stacked self-assembled InAs/GaAs QDs. For strongly coupled QDs grown with a 4 nm spacer, state-filling spectroscopy reveals a shift of the QD symmetric state to lower energies by ∼23 meV. The wetting layer states are also strongly coupled because of the shallow confinement, resulting in a redshift of its symmetric state by ∼26 meV. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126317
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