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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1954-1958 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of 0.7 μm thick GaN layers have been grown by solid-source rf-plasma assisted molecular beam epitaxy on sapphire (0001) substrates with the addition of 0.10%–3.30% Al. The Al concentration was determined by secondary ion-mass spectrometry and Auger-electron spectroscopy, while the layer quality was assessed by photoluminescence, Hall effect measurement, and high-resolution scanning electron microscopy. Microscopy revealed a surface roughness varying with Al content. The smallest surface roughness was obtained at 0.10% and 3.30% Al. Low-temperature photoluminescence revealed dominating peaks attributed to the neutral donor-bound exciton. Its energy increased slightly with Al concentration, which established a correlation between the Al concentration and the band gap. The surface morphology, the corresponding optical and electrical properties, showed a clear improvement of the GaN layer quality for the range of 0.10%–0.17% Al content. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3662-3667 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial molecular beam epitaxy growth of GaN on GaAs(001) was studied by real-time monitoring of the (3×3) surface reconstruction and its transition to an unreconstructed (1×1). Various growth conditions were established by variation of the V/III ratio, i.e., the Ga flux. We characterized the effect of the first two strained GaN monolayers: a N-terminated GaN (3×3) monolayer and a second unreconstructed (1×1) monolayer. A series of samples were grown under N-rich, Ga-rich, and near-stoichiometric growth conditions. The resulting morphology of the interface region was analyzed by high-resolution scanning electron microscopy, Auger-electron spectroscopy, and double crystal x-ray diffractometry. The N-rich and Ga-rich conditions resulted in extensive defect formation due to the nitridation damage of the GaAs substrate. The extent of this was found to be determined by the properties of the first GaN monolayer. The surface roughness under optimum growth conditions could be as low as ∼20 nm, defined by nanocrystalline grains, showing no observable nitridation damage. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6247-6250 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An inverse parabolic quantum well was successfully grown by molecular-beam epitaxy using a digital compositional grading superlattice composed of Al0.36Ga0.64As/GaAs. The photoluminescence and photocurrent measurements for this structure gave a good agreement between experimental and theoretical results. Large Stark shift and amplitude reduction of 1e-1hh exciton resonance under applied electric field were found in the photoluminescence spectra, which are substantially larger than the conventional square quantum well. These properties benefited from the concept of local-to-global state transitions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3464-3466 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report results for Si layers embedded in GaAs, extending from the delta-doped (δ-doped) range up to 6 monolayers (MLs) derived by means of variable temperature resistivity and Hall effect measurements, secondary ion mass spectrometry (SIMS), and high resolution x-ray diffractometry (HRXRD) techniques. The conductivity transition from free carrier transport in ordered δ-layers (〈1 ML) to strongly localized two-dimensional variable range hopping (2D-VRH) transport under potential fluctuation disordered conditions ((approximately-greater-than)4 ML) is clearly observed. This observation is in good agreement with the SIMS and HRXRD data. Results from the intermediate case with 2–3 MLs are also discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 336-337 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influences of GaAs cap layer thickness on residual strain in partially relaxed, 25-nm-thick In0.2Ga0.8As/GaAs single quantum wells have been investigated by photoluminescence and photoreflectance at 77 K. It was found that the residual strain increased and the optical quality improved with increasing cap layer thickness. Therefore, both quantum well and cap layer thicknesses determine the optical quality in lattice-mismatched semiconductor heterostructures.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1552-1554 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Steps of monolayer height (0.28 nm) were observed by atomic force microscopy on a GaAs surface grown by molecular beam epitaxy. The monolayer terrace width between steps was found to be as large as 1000 nm in some areas. Surface reconstruction affects the surface diffusion process during growth and the shape of the step edges. Growth spirals were observed. Spirals originate from screw dislocations. The growth mechanism is according to the Burton–Cabrera–Frank theory.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3242-3244 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The strain mediation in multiple quantum well structures consisting of In0.36Ga0.64As layers separated by GaAs barriers has been investigated by photoluminescence. Strain in layers grown by molecular beam epitaxy was evaluated by comparing the photoluminescence-peak energies with calculated recombination energies in strained quantum wells using the effective-mass Schrödinger equation. In structures consisting of two 40 A(ring) thick In0.36Ga0.64As layers separated by a GaAs barrier, onset of relaxation is not observed until the barrier thickness is reduced below 100 A(ring). The corresponding value is 180 A(ring) in a structure with two 50 A(ring) thick In0.36Ga0.64As layers. Results also show that strain mediation increases with the number of strained In0.36Ga0.64As layers. In multiple quantum well structures with four 50 A(ring) thick In0.36Ga0.64As layers, the barrier thickness required to stop strain mediation increases to 225 A(ring). In similar structures with eight and twenty 50 A(ring) thick In0.36Ga0.64As layers this value is 275 A(ring). © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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