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  • American Institute of Physics  (22)
  • American Institute of Physics (AIP)  (17)
  • Wiley-Blackwell  (2)
  • Copernicus
  • 1995-1999  (41)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3214-3218 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use photoluminescence to study residual transition metal contaminants in GaN layers, which are grown by the sandwich technique either on 6H-SiC substrate or on sapphire substrate. We observe three no-phonon lines in the near infrared optical region at 1.3 eV, 1.19 eV, and 1.047 eV caused by 3d transition metals. The appearance of GaN related host modes in the phonon sideband of these emissions proves that the luminescence centers are incorporated in the hexagonal GaN layers. In this paper we especially focus on the luminescence band with the no-phonon line at 1.047 eV. Temperature dependent photoluminescence measurements reveal an excited state splitting of 8 meV. In photoluminescence excitation spectroscopy we observe a further excited state at 1.6 eV with a fine structure splitting. The appearance of this excited state in the n-type samples gives evidence that the defect must already exist in its luminescent charge state without illumination. The experimental results on the 1.047 eV emission fit to a 4T2(F)→4A2(F) internal electronic transition of a transition metal with a 3d7 electronic configuration. © 1996 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1481-1485 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on optical and electrical properties of modulation doped InxGa1−xAs/InP single quantum wells in the composition range 0.56≤x≤0.79. Cyclotron resonance, contactless Shubnikov–de Haas and magnetophotoluminescence experiments are used to obtain two dimensional carrier densities, effective masses of electrons and holes and scattering times. We present data which give evidence for zero magnetic field spin splitting. The dispersion relation for electrons and holes is presented. © 1996 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6549-6561 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The intramolecular vibrational relaxation (IVR) of an excited Si–H stretch (second overtone) and C–H stretch (first overtone) in methylsilane has been examined by eigenstate resolved infrared spectroscopy. The experiment probes a molecular beam produced in a supersonic expansion, excited by a laser in a power buildup cavity, and detected by a liquid helium cooled silicon bolometer. The Si–H stretch [local mode (3,0,0), both A and E combinations] is compared with the nearly isoenergetic C–H stretch [predominantly the 2ν70 band]. With the calculated density of states almost unchanged, the two modes exhibit very different IVR behavior, which is quantified in terms of the lifetime of the bright states and the coupling between the bright states and the dark states. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4985-4988 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The characterization of semiconductor heterostructures requires different measurement techniques such as photoluminescence, Shubnikov–de Haas, and cyclotron resonance. We present a simple experimental setup which allows to make use of all these techniques without changing the equipment. There is no need for electrical contacts. The performance is demonstrated on InxGa1−xAs/InP quantum wells. © 1995 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2822-2824 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an optical investigation of the Zeeman behavior of the deep iron acceptor in GaN grown on 6H–SiC. The characteristic ground state splitting of the near-infrared luminescence transition at 1.2988 eV allows for an unambiguous assignment to Fe3+previously proposed on the basis of ODMR results. The observed luminescence lifetime of 8 ms as well as the fine structure of the excited state are consistent with a 4T1(G)–6A1(S) transition. The 4T1(G) state is found to couple only weakly to ε-type phonon modes. © 1995 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2075-2083 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Backward stimulated Raman scattering (SRS) experiments have been performed using the optical fiber smoothing implemented on the high-power Phébus laser facility [Laser Part. Beams 4, 93 (1988)]. The interaction took place in low-Z plasmas presenting either exponential density profiles (solid targets) or Gaussian-type profiles. Raman instability was driven with 1.4 ns duration—0.53 μm laser pulses, containing an energy up to 1.8 kJ. Comparative and absolute measurements of SRS reflectivity are reported as a function of the incident laser intensity, both with and without beam smoothing. Near-backward time-resolved SRS spectra are also presented. Random phase plates are not used in these experiments. With or without smoothing, SRS reflectivities of the order of 10% have been measured. However, smoothing becomes effective in exponential profiles below 1015 W/cm2. Although the optical fiber efficiently reduces the contrast of the energy modulations in the focal spot, the spectral bandwidth may be insufficient to quench SRS development in these conditions. This last assumption is in agreement with theoretical predictions. © 1995 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1890-1895 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN films grown on (0001) 6H–SiC and (0001) Al2O3 substrates using low-pressure chemical vapor deposition with GaCl3 and NH3 as precursors are comparatively explored by optical, scanning tunneling, and transmission electron microscopy. Independent of the substrate material used, the surface of the GaN layers is covered by hexagonally shaped islands. For GaN on 6H–SiC, the islands are larger in diameter ((approximate)50 μm) and rather uniformly distributed. An atomically flat interface is observed for GaN on Al2O3 in contrast to GaN grown on 6H–SiC, where the interface is characterized by large steps. For both substrates, faceted holes (named as pinholes) are observed in near-surface regions of the GaN layers occurring with a density of about 7×108 cm−2. No unequivocal correlation between the density of pinholes and the density of threading dislocations ((approximate)1.6×1010 cm−2 for GaN/Al2O3 and (approximate)4×109 cm−2 for GaN/6H–SiC) can be found. Rather, different types of defects are identified to be correlated with the pinholes, implying a dislocation-independent mechanism for the pinhole formation. Despite the small lattice mismatch between GaN and 6H–SiC, the pronounced original surface roughness of this substrate material is believed to account for both the marked interfacial roughness and the still existing high density of threading dislocations. © 1997 American Institute of Physics.
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results from spatially resolved photoluminescence and Raman experiments on the substrate interface region of wurtzite GaN layers. We show that the broad photoluminescence band with an intensity maximum at 2.4 eV is not an intrinsic property of GaN. We found that this photoluminescence band is strong only near the interface. Our investigations reveal that both the substrate interface and a region of structural reorientation of the layer near the interface act as a source of the photoluminescence. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1298-1300 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence investigations on undoped n-type GaN layers grown on 6H-SiC and sapphire reveal the presence of residual acceptors with a binding energy of 230 meV. Their presence in high temperature vapor phase epitaxy grown layers is strongly correlated with the graphite susceptor containing the Ga. Mg as a contamination can be ruled out. In metal organic vapor phase epitaxially grown layers, the metal organic are probably the source of the carbon contamination. It is concluded that carbon on nitrogen sites introduces the most shallow acceptor in GaN. The experimental observations are supported by an estimate of the acceptor binding energy using effective-mass-theory. © 1995 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2456-2458 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated coherently strained AlxGa1−xN/GaN heterostructures (0〈x〈0.22) grown by metalorganic vapor phase epitaxy on sapphire with photoluminescence (PL), reflexion and cathodoluminescence experiments. The energetic positions of the free A exciton as a function of the alloy compositions are deduced from temperature dependent PL and from reflexion measurements. We obtain a small bowing parameter and no evidence for a Stokes shift between absorption and emission. Compositional inhomogeneities are present, but the fluctuations are too small to be important for carrier localization. The broadening of the luminescence linewidth in the alloys can be described by statistical disorder of a random alloy. © 1999 American Institute of Physics.
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