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  • 1
    Digitale Medien
    Digitale Medien
    Acetylenics. 1. Aromatic amines containing the acetylenic triple bond (1970)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 13 (1970), S. 1249-1250 
    Details
    ISSN: 1520-4804
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/jm00300a068
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  • 2
    Digitale Medien
    Digitale Medien
    Acetylenics. 2. Synthesis and pharmacology of certain N,N-dialkyl-3-phenylpropyn-2-amines and some analogs with tryptamine-like behavioral effects in mice (1978)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 21 (1978), S. 253-257 
    Details
    ISSN: 1520-4804
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/jm00201a003
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  • 3
    Digitale Medien
    Digitale Medien
    The use of graded InGaAs layers and patterned substrates to remove threading dislocations from GaAs on Si (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2697-2702 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated threading dislocation (TD) removal from GaAs films on Si by introduction of additional InGaAs graded strain layers in combination with growth on patterned substrates. The substrate patterns consisted of mesas with 10–34 μm widths. The mesa sidewalls were either overhanging (concave), leading to free sidewalls for the film on the mesas, or outward sloping (convex) sidewalls with {111} orientation. The dislocation structure was studied using transmission electron microscopy. It was found that the graded strained layers led to a reduction of dislocation density by a factor of ∼5 in films grown both on mesas with concave sidewalls and on unpatterned substrates. This reduction was due to dislocation reactions leading to annihilation of TDs. For films with graded strained layers on mesas with convex sidewalls, an additional factor of ∼3 reduction in TD density was observed in the part of the film that was grown on top of the mesas. In this case all mobile TDs (TDs associated with 60° misfit dislocations, i.e., TDs that could glide to relieve misfit stress) were removed from the film on top of the mesas to the regions above the sidewalls and only TDs associated with 90° misfit dislocations remained. We suggest that this is due to pinning of the TDs associated with 60° misfit dislocations at the mesa edges and we have presented an explanation for this pinning in terms of the stress conditions at the {111} oriented mesa edges. In addition, this leads us to suggest that in order to obtain minimum TD density it is imperative to prevent formation of 90° misfit dislocation during lattice mismatched heteroepitaxial growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357572
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of Si doping on strain, cracking, and microstructure in GaN thin films grown by metalorganic chemical vapor deposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7745-7752 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of Si doping on the strain and microstructure in GaN films grown on sapphire by metalorganic chemical vapor deposition was investigated. Strain was measured quantitatively by x-ray diffraction, Raman spectroscopy, and wafer curvature techniques. It was found that for a Si concentration of 2×1019 cm−3, the threshold for crack formation during film growth was 2.0 μm. Transmission electron microscopy and micro-Raman observations showed that cracking proceeds without plastic deformation (i.e., dislocation motion), and occurs catastrophically along the low energy {11(underbar)00} cleavage plane of GaN. First-principles calculations were used to show that the substitution of Si for Ga in the lattice causes only negligible changes in the lattice constant. The cracking is attributed to tensile stress in the film present at the growth temperature. The increase in tensile stress caused by Si doping is discussed in terms of a crystallite coalescence model. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.373529
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  • 5
    Digitale Medien
    Digitale Medien
    Dislocation imaging using transmission ion channeling (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2640-2653 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Interface dislocations present in a Si0.85Ge0.15/Si sample have been imaged using the channeling scanning transmission ion microscopy (CSTIM) method with a 2 MeV proton beam 200 nm across. Groups of parallel dislocations gave dark bands of contrast down to ∼1.5 μm across, the contrast arising from dechanneling of the beam by the bent lattice planes. Tilting of the sample caused the band contrast to change and gave quantitative data concerning the local bending of the lattice planes. A low-angle boundary model was developed to describe the effect of the groups of dislocations on the channeling contrast. Channeling and topography contrast were obtained from mesa structures present on the sample. Improvements in the sensitivity of the CSTIM method are discussed. The dislocations in the sample were initially characterized by transmission electron microscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353081
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  • 6
    Digitale Medien
    Digitale Medien
    Phase separation in InGaN multiple quantum wells annealed at high nitrogen pressures (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3950-3952 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Phase separation was found to occur in In0.33Ga0.67N/GaN multiple-quantum-well structures after annealing at 975 °C in a hydrostatic pressure of 5 kbar N2 for 4 h. X-ray diffraction (XRD) spectra of the as-grown samples showed superlattice peaks that were replaced by a broad, single-phase peak after annealing. Transmission electron microscopy (TEM) images of the annealed samples show In-rich precipitates and voids that are found only within the quantum-well region. Both TEM and XRD measurements indicated that the formation of voids and second phases were suppressed after annealing in a hydrostatic pressure of 15 kbar. In addition, optical absorption measurements on these samples showed no indication of a peak at 2.65 eV that was observed in previous annealing studies. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.125504
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  • 7
    Digitale Medien
    Digitale Medien
    Influence of microstructure on the carrier concentration of Mg-doped GaN films (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2734-2736 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Room-temperature Hall effect measurements of (0001) Mg-doped GaN films grown on sapphire substrates by metalorganic chemical vapor deposition show a reduction in hole concentration for Mg concentrations greater than 1020 cm−3. A combination of secondary ion mass spectrometry and transmission electron microscopy indicates a steadily increasing Mg incorporation during growth and the formation of inversion domains at these high concentrations. We discuss mechanisms that could give rise to a reduction of the hole concentration at high Mg doping levels. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1413222
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  • 8
    Digitale Medien
    Digitale Medien
    Faceted inversion domain boundary in GaN films doped with Mg (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2479-2481 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Homoepitaxial GaN films, doped with Mg, were grown by rf-plasma molecular-beam epitaxy on Ga-polarity (0001) templates. Convergent-beam electron diffraction analysis establishes that the film polarity changes from [0001] to [0001(underbar)] when the Mg flux during growth is approximately 1 ML/s. Secondary ion mass spectrometry indicates a doping concentration of ∼1020 cm−3 in the film where the inversion occurs, and a reduced Mg incorporation in the [0001(underbar)] material. Transmission electron microscopy shows that the inversion domain boundary is faceted predominantly along the {0001} and {h,h,−2h,l} planes, with l/h approximately equal to 3. Using first-principles total energy calculations, we show that the {h,h,−2h,l} segments of the boundary are stabilized by the incorporation of Mg in threefold coordinated lattice sites. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1318731
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  • 9
    Digitale Medien
    Digitale Medien
    Structural and optical properties of pseudomorphic InxGa1−xN alloys (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1757-1759 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Thick (225 nm) InxGa1−xN layers, grown on 5 μm thick GaN, were found by x-ray diffraction (XRD) measurements to be pseudomorphic up to x=0.114. Transmission electron microscopy showed that no misfit or additional threading dislocations were created at the InxGa1−xN/GaN interface. Composition of the overlayers was determined by Rutherford backscattering spectrometry and correlated to both the a and c lattice constants from XRD. It was found that Vegard's law is applicable at these compositions, if the biaxial strain is included. Biaxial strain must also be considered to accurately determine the bowing parameter as shown by optical transmission measurements. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.122272
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  • 10
    Digitale Medien
    Digitale Medien
    Stripe-width dependence of threshold current for gain-guided AlGaInN laser diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 404-406 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The threshold current density of narrow-stripe gain-guided nitride laser diodes increases very rapidly as the stripe width is made narrow. To examine this behavior, waveguide simulations, incorporating the complex refractive indices associated with optical gain, have been used to analyze the lateral optical modes of gain-guided laser diodes. Threshold current was then determined from the gain–current relationship of our laser material, which was obtained experimentally. These evaluations reveal that gain guiding, coupled with a carrier-induced index depression, offer a reasonable explanation for the rapid increase in threshold when the stripe width becomes less than 5 μm. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123084
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