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  • 1
    Electronic Resource
    Electronic Resource
    N-induced vibrational modes in GaAsN and GaInAsN studied by resonant Raman scattering (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5027-5031 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vibrational modes introduced by the incorporation of N into GaAs and GaInAs have been studied by Raman spectroscopy on samples grown by molecular-beam epitaxy using a rf nitrogen plasma source. When proceeding from GaAs1−xNx to Ga1−yInyAs1−xNx with x≤0.04 and y≤0.12, the nitrogen-induced vibrational mode near 470 cm−1 observed in GaAsN was found to broaden and to split into up to three components with one component at a frequency higher than that of the Ga–N mode in GaAsN. This observation shows that the incorporation of In into GaAsN strongly affects the local bonding of the N atoms by changing the local strain distributions as well as the formation of a significant fraction of In–N bonds. The resonant enhancement in the scattering cross section of the Ga–N vibrational mode, observed in low N-content GaAs1−xNx (x(approximate)0.01) for incident photon energies matching the mostly N-related E+ transition at around 1.8 eV, was found to broaden significantly upon increasing N content as well as upon the addition of In to form GaInAsN. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412277
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric function spectra of GaN, AlGaN, and GaN/AlGaN heterostructures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2779-2785 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pseudodielectric function spectra 〈ε〉 of wurtzite GaN, AlGaN, and GaN/AlGaN heterostructures were determined for photon energies ranging from 2 to 5 eV, using variable angle spectroscopic ellipsometry (SE). Samples were grown by low-pressure metalorganic chemical vapor deposition on c-plane sapphire substrates. The experimental 〈ε〉 spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. In this way, parametric dielectric function spectra of GaN and AlxGa1−xN (x≤0.16) were derived, as well as the composition dependence of the AlxGa1−xN band gap energy. The SE band gap data were found to be consistent with a bowing parameter close to 1 eV. Finally, the GaN and AlxGa1−xN parametric dielectric functions were used to quantitatively analyze the pseudodielectric function spectrum of GaN/AlGaN modulation doped field effect transistor structures, demonstrating the potential of SE in combination with a multilayer parametric dielectric function model for nondestructive ex situ control of GaN/AlGaN device structures. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1342022
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  • 3
    Electronic Resource
    Electronic Resource
    Quaternary GaInAsN with high In content: Dependence of band gap energy on N content (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2448-2450 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quaternary pseudomorphically strained GaInAsN films and double-quantum wells were grown by plasma assisted molecular-beam epitaxy on an InP substrate. The In content ranged from 53% to 70% while the N content was varied between 0% and 2.4%. A reduction of compressive strain and a low-energy shift of photoluminescence (PL) peak position was observed with increasing N concentration, accompanied by a reduction in PL peak intensity and increase in linewidth. The net effect of N incorporation on the GaInAsN band gap energy was calculated from the measured PL peak energies. The thus obtained composition dependent GaInAsN band gap energy was fitted using the band anticrossing model, yielding values for the interaction parameter CMN for high In-containing GaInAsN being only slightly smaller than that reported for low In-content GaInAsN on GaAs. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467612
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  • 4
    Electronic Resource
    Electronic Resource
    Improvement of λ(approximate)5 μm quantum cascade lasers by blocking barriers in the active regions (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2048-2050 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the improvement of quantum cascade lasers emitting at λ∼5 μm by introducing AlAs blocking barriers together with strain-compensating InAs layers into the active regions. The blocking barriers are designed to selectively prevent electrons in the initial laser state from tunneling out of the active region, while maintaining the high tunneling probabilities of the electrons in the final laser states. Adopting blocking barriers, the maximum peak power per facet at 77 K (300 K) is increased from 285 (30 mW) to 900 mW (240 mW), and the maximum operation temperature in pulsed mode has been improved from 320 to 350 K with respect to a reference sample without blocking barriers. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462866
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  • 5
    Electronic Resource
    Electronic Resource
    GaAsN interband transitions involving localized and extended states probed by resonant Raman scattering and spectroscopic ellipsometry (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3592-3594 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interband transitions in GaAs1−xNx (0≤x≤0.033), involving a localized resonant N-derived energy level and the GaAs-like L conduction and valence band states, have been studied by resonant Raman scattering and spectroscopic ellipsometry, respectively. Raman scattering by the GaN-like LO2 phonon showed for x(approximate)0.01 a pronounced resonant enhancement for incident photon energies approaching the mostly N-related E+ transition at around 1.8 eV, but not at the E1 and E1+Δ1 interband transitions, reflecting the strongly localized nature of both the N-related electronic level and the Ga–N vibrational mode. Spectroscopic ellipsometry, in contrast, being sensitive to the overall dielectric function of the GaAsN, revealed the effect of N incorporation on the GaAs-like E1 and E1+Δ1 interband transitions, which is a high-energy shift with increasing N-content accompanied by a significant broadening. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329167
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  • 6
    Electronic Resource
    Electronic Resource
    Piezoelectric field and confinement effects on the dielectric function spectrum of InGaN/GaN quantum wells (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 79-81 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In0.13Ga0.87N/GaN double heterostructures and quantum wells (QWs) have been studied by room-temperature photoluminescence (PL) and spectroscopic ellipsometry (SE). PL revealed the presence of strong piezoelectric fields, which strongly influence the luminescence properties for InGaN QW widths in the 3–12 nm range. The pseudodielectric function spectrum derived from the SE measurements were analyzed using a multilayer approach, describing the dielectric function of the individual layers by a parametric oscillator model. The fundamental band-gap resonance in the InGaN dielectric-function spectrum was found to broaden for an InGaN layer width of 12 nm, as compared to bulk-like InGaN layers, due to piezoelectric field effects. For a much narrower QW width of 1.7 nm, however, quantum confinement was found to dominate over piezoelectric-field effects, resulting in a much sharper band-gap resonance shifted to higher energies and an increased oscillator strength. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125662
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  • 7
    Electronic Resource
    Electronic Resource
    Preferential formation of Al(Single Bond)N bonds in low N-content AlGaAsN (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2081-2083 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bonding of nitrogen in low N-content AlxGa1−xAs1−yNy with x≤0.05 and y≤0.04 has been studied by Raman spectroscopy. Upon the addition of Al to GaAsN, additional vibrational modes are observed at around 450 cm−1, which is below the GaN-like longitudinal optical (LO) phonon mode centered at 470 cm−1. These modes are attributed to the formation of Al and N containing complexes with Al-to-N bonding. With increasing Al content the Al–N related modes gain intensity at the expense of the GaN-like mode, and they become the dominant N-related feature for an Al-content of 5% at a fixed N content of 1%. On the other hand, increasing the N content from 0% up to 4% at a constant Al concentration of 5% results first in the appearance and eventual saturation in intensity of the AlN-like modes, accompanied by a steep increase in intensity and eventual dominance of the GaN-like vibrational mode. Simultaneously the AlAs-like LO2 phonon mode shows a drastic decrease in intensity for N contents exceeding 2%. All these observations strongly indicate that there is a preferential formation of Al(Single Bond)N bonds in low N- and Al-content AlGaAsN, which is in direct contrast to GaInAsN, where even after thermal annealing the GaN-like mode remains dominant in the Raman spectrum compared to the InN-like modes. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464660
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  • 8
    Electronic Resource
    Electronic Resource
    GHz-THz Detection by Asymmetrically-Shaped GaAs: Bulk Material versus Nanostructures (2002)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 384-385 (Jan. 2002), p. 193-196 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/06/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.384-385.193.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Heck reactions catalyzed by oxide-supported palladium – structure–activity relationships (2000)
    Springer
    Topics in catalysis 13 (2000), S. 319-326 
    Details
    ISSN: 1572-9028
    Keywords: Heck reaction ; formation of carbon–carbon bonds ; oxide-supported palladium ; Pd dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic activity and selectivity of palladium supported on various metal oxides in carbon–carbon coupling reactions of aryl bromides with styrene (Heck reaction) were investigated. The activity is determined by the nature of the oxide support and the Pd dispersion (structure–activity relationships). The relation of homogeneous (leaching) and heterogeneous mechanisms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009022030636
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  • 10
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    Preferential formation of Al–N bonds in low N-content AlGaAsN (2002)
    American Institute of Physics
    Details
    Publication Date: 2002-03-25
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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