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Sökning: WFRF:(Paskova Tanja 1961 )

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1.
  • Monemar, Bo, 1942-, et al. (författare)
  • Defects in Gallium Nitride
  • 1999
  • Ingår i: International Workshop on Materials Science,1999. - Proc. of the International Workshop on Materials Science 99, ed. by F. F. Bekker et al., Vol. 1 : Hanoi National University Publishing House. ; s. 28
  • Konferensbidrag (refereegranskat)
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3.
  • Monemar, Bo, 1942-, et al. (författare)
  • The 3.466 eV Bound Exciton in GaN
  • 2001
  • Ingår i: Physica status solidi. B, Basic research. - 0370-1972. ; 228:2, s. 489-492
  • Tidskriftsartikel (refereegranskat)abstract
    •  We discuss the available optical data for the 3.466 eV bound exciton in GaN, which has been a controversial issue in the recent literature. We conclude that the experimental results are only consistent with the identification as an exciton bound at a neutral acceptor with a spin-like bound hole. The chemical identity is still not clear.
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7.
  • Darakchieva, Vanya, 1971-, et al. (författare)
  • Anisotropic strain and phonon deformation potentials in GaN
  • 2007
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 75:19, s. 195217
  • Tidskriftsartikel (refereegranskat)abstract
    • We report optical phonon frequency studies in anisotropically strained c -plane- and a -plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The anisotropic strain in the films is obtained from high-resolution x-ray diffraction measurements. Experimental evidence for splitting of the GaN E1 (TO), E1 (LO), and E2 phonons under anisotropic strain in the basal plane is presented, and their phonon deformation potentials c E1 (TO), c E1 (LO), and c E2 are determined. A distinct correlation between anisotropic strain and the A1 (TO) and E1 (LO) frequencies of a -plane GaN films reveals the a A1 (TO), b A1 (TO), a E1 (LO), and b E1 (LO) phonon deformation potentials. The a A1 (TO) and b A1 (TO) are found to be in very good agreement with previous results from Raman experiments. Our a A1 (TO) and a E1 (LO) phonon deformation potentials agree well with recently reported theoretical estimations, while b A1 (TO) and b E1 (LO) are found to be significantly larger than the theoretical values. A discussion of the observed differences is presented. © 2007 The American Physical Society.
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8.
  • Darakchieva, Vanya, 1971-, et al. (författare)
  • Deformation potentials of the E1 (TO) and E2 modes of InN
  • 2004
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 84:18, s. 3636-3638
  • Tidskriftsartikel (refereegranskat)abstract
    • The determination of deformation potentials of E1(TO) and E 2 modes of InN were discussed. The deformation potentials were evaluated for two sets of stiffness constants using x-ray diffraction, IR spectroscopic ellipsometry (IRSE), Raman scattering, and Grüneisen parameter values. The InN layer were grown on GaN buffer layers on (0001) sapphire by molecular beam epitaxy. It was found that the strain-free values of the InN E1(TO) mode was 477.9 cm-1 and 491.9 cm -1 for the E2 modes.
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9.
  • Darakchieva, Vanya, 1971-, et al. (författare)
  • Optical phonons in a-plane GaN under anisotropic strain
  • 2008
  • Ingår i: Group-III nitrides with nonpolar surfaces: growth, properties and devices. - Wiley. - 978-35-2740-768-2 - 3-527-40-768-5 ; s. 219-253
  • Bokkapitel (övrigt vetenskapligt)abstract
    • This is the first monograph to discuss in detail the current stage of development of nonpolar nitrides, with specific emphasis on the three main topics of crystal growth, properties and device studies. World–class researchers summarize their own recent achievements in their respective fields of expertise, covering both nonpolar and semipolar nitride materials. The bulk of the discussion in each chapter is related to the physical properties of the material obtained by the respective technique, in particular, defect density and properties of the defects in nonpolar nitrides. In addiiton, the optical and vibrational properties are also addressed in several chapters, as is progress in heterostructures, quantum wells and dots based on the AlGaN/GaN and the InGaN/GaN systems. Finally, an outlook of the application areas of the differently grown materials is presented in most chapters, together with the capabilities and limitations of the respective growth approaches used.
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10.
  • Darakchieva, Vanya, 1971-, et al. (författare)
  • Phonon mode behavior in strained wurtzite AlN/GaN superlattices
  • 2005
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 71:11, s. 115329
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied phonons in AlN/GaN superlattices with different periods but a constant well-to-barrier ratio using a combination of infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The strain evolution in the superlattice structures is assessed by high-resolution x-ray diffraction and reciprocal space mapping. We have identified E1(TO), A 1(LO) and E2 localized, and E1(LO) and A 1(TO) delocalized superlattice modes. The dependencies of their frequencies on in-plane strain are analyzed and discussed, and the strain-free frequencies of the superlattice modes are estimated. A good agreement between theory and experiment is found in the case of GaN localized modes, while large deviations between theoretically estimated and experimentally determined frequency shifts are observed for the AlN localized modes. The delocalization effect on the A1(TO) and E1(LO) phonons, as well as the free-carrier effect on the E1(LO) phonon are also discussed. ©2005 The American Physical Society.
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