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  • 1
    Electronic Resource
    Electronic Resource
    Raman scattering in GaN pillar arrays (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2866-2869 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a detailed study of GaN pillar arrays by atomic force microscopy (AFM), Raman spectroscopy, and photoluminescence (PL) spectroscopy. AFM is used to characterize the shape of the GaN pillars and revealed a large roughness of etched pillar surfaces. Raman scattering spectra of the pillars are well described by angular dispersion of polar optical phonons induced by the three-dimensional shape of the pillar. Additional Raman scattering has been tentatively assigned to the activation of the high frequency B1 silent mode by defects introduced during the ion etching. This result is well correlated with the appearance of donor and acceptor-related PL of the GaN pillars. N vacancy or/and Ga interstitials would be likely candidates for donors in the nonstoichiometric GaN near the surface of the etched pillars. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445492
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  • 2
    Electronic Resource
    Electronic Resource
    Coupled LO–plasmon modes in semi-insulating GaAs of ZnSe/GaAs heterojunctions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1128-1135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy is used to investigate strong band bending at the interface in semi-insulating substrates of ZnSe/GaAs heterostructures grown at high epitaxy rates. Direct evidence is given of the enhancement of polar modes strength, on the substrate side, by the electric field of the space-charge zone associated with Fermi-level pinning. The latter is qualitatively analyzed by following band flattening under illumination through the evolution of interfacial coupled LO-phonon–plasmon modes. Corresponding Raman line shapes are discussed within the phenomenological approach of D. H. Hon and W. L. Faust [Appl. Phys. 1, 241 (1973)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362850
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  • 3
    Electronic Resource
    Electronic Resource
    Raman study of band bending at ZnSe/GaAs interfaces (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1241-1248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Apparent p-type conductivity in nonintentionally doped ZnSe layers, grown at high temperature on semi-insulating GaAs substrates, is investigated by Raman spectroscopy. The microprobe technique provides direct evidence for carrier location on the GaAs side of the structures, close to the interface. Line-shape analysis of the coupled LO phonon-plasmon mode for different exciting wavelengths can be achieved, within the model of Hon and Faust [Appl. Phys. 1, 241 (1973)], only when incorporating plasma inhomogeneity. Electronic band bending at the junction in GaAs is deduced from the inferred carrier-density profile. Changes in Raman spectra under strong illumination are shown to proceed from the flattening of the bands through selective carrier photoinjection. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358925
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  • 4
    Electronic Resource
    Electronic Resource
    Interplay of electrons and phonons in heavily doped GaN epilayers (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1305-1309 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy is used to analyze the effect of electrons on the lattice dynamics of unintentionally heavily doped GaN. The deposition temperature of GaN buffer layers on sapphire substrates is found to have an important influence on the presence of free carriers in GaN layers, evidenced by plasmon coupling to the A1(LO) phonon. Data from infrared measurements are used to calculate the Raman line shape of q=0 coupled A1(LO)-plasmon modes in a dielectric approach and give a good fit of the L−(q=0) component observed in Raman spectra. In particular, the fitting procedure applied to spatially resolved micro-Raman measurements reveals an inhomogeneous concentration of electrons on the scale of hexagonal microcrystallites. Partial screening of phonons with wave vectors differing from the q=0 transfer of incident and scattered photons is invoked to explain LO-like scattering over the whole spectral range of optical phonons, attributed to charge density fluctuations on account of its polarization properties. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365903
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  • 5
    Electronic Resource
    Electronic Resource
    Comment on "Observation of phonon-plasmon coupled modes at the interface between ZnSe and semi-insulating GaAs by Raman spectroscopy'' [Appl. Phys. Lett. 62, 1800 (1993)] (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3236-3237 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110209
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  • 6
    Electronic Resource
    Electronic Resource
    Phonons in a strained hexagonal GaN–AlN superlattice (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 703-705 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A GaN (6.3 nm)-AlN (5.1 nm) superlattice, grown by molecular beam epitaxy on a sapphire substrate and an AlN buffer layer, has been studied by means of micro-Raman spectroscopy. Most of the observed features have been identified and assigned to optical phonons of the superlattice layers. The average biaxial strain in GaN layers has been deduced from the detailed analysis of the frequency shift observed on the phonon lines. Additional measurements on the bevelled sample clearly suggest the significant increase of this strain for decreasing distances from the interface with the buffer layer. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122993
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  • 7
    Electronic Resource
    Electronic Resource
    Coupling of GaN- and AlN-like longitudinal optic phonons in Ga1−xAlxN solid solutions (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2674-2676 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Long-wavelength optical phonons of Ga1−xAlxN solid solutions have been identified in a wide compositional range by Raman spectroscopy. The A1 and E1 polar phonon frequencies evolve continuously with x from one-member crystal to the other. The same behavior seems to hold true for the silent B1 mode, which manifests itself by an interference with an unidentified continuum. Coupling of the longitudinal-optic (LO) modes associated with the two types of bonds, via the macroscopic electric field, is treated by a generalization of the dielectric model [D. T. Hon and W. L. Faust, J. Appl. Phys. 1, 241 (1973)]. This approach accounts for the observed frequencies and supports the apparent one-mode behavior of the polar LO phonons. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121095
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  • 8
    Electronic Resource
    Electronic Resource
    Direct signature of strained GaN quantum dots by Raman scattering (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 686-688 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a Raman study of strained wurtzite GaN quantum dots embedded in AlN spacers. Various laser excitations between 2.33 and 3.81 eV were used, which allows for selective probing of the dots, through resonant enhancement of the Raman signal. A direct signature of the A1 (LO) and E2 phonons of the GaN dots has been obtained. The measured phonon frequencies show that the mean in-plane strain inside the GaN dots approaches the lattice mismatch between GaN and AlN. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388880
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  • 9
    Electronic Resource
    Electronic Resource
    Signature of GaN–AlN quantum dots by nonresonant Raman scattering (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2174-2176 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stackings of GaN quantum dots embedded in an AlN matrix, constituting periodic structures with a mean aluminum content in the 80%–90% range, have been investigated by Raman spectroscopy under excitation in the visible range, i.e., far from resonant conditions. For comparison, spectra of an alloy sample with approximately the same composition has been also recorded. The differences evidenced between these spectra give evidence for separate signatures of quantum dots and spacers of the multilayered structure. The mean (biaxial) strain in GaN dots and AlN spacers has been deduced from the measured phonon frequencies. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310171
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  • 10
    Electronic Resource
    Electronic Resource
    Temporal variations of hemolymph esterase activity and juvenile hormone titers during ovocyte maturation in Acheta domesticus (Orthoptera)
    Amsterdam : Elsevier
    General and Comparative Endocrinology 55 (1984), S. 480-487 
    Details
    ISSN: 0016-6480
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0016-6480(84)90021-2
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