Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 27: II-VI semiconductors
HL 27.12: Talk
Wednesday, March 28, 2007, 17:15–17:30, H13
Resonant Raman Scattering and Recombination Dynamics in Homoepitaxial-Grown and Single Crystal ZnO — •Markus R. Wagner1, Patrick Zimmer1, Axel Hoffmann1, Stefan Lautenschläger2, Joachim Sann2, and Bruno K. Meyer2 — 1Institut für Festkörperphysik, Technische Universität Berlin — 2I. Physikalisches Institut, Justus-Liebig-Universität Gießen
Resonant Raman scattering in ZnO at low temperatures is investigated by applying a frequency doubled titan-saphire laser as tunable excitation source. The influence of exciton phonon interactions such as the deformation potential for non-polar optical phonons and the Fröhlich interaction for polar LO modes are discussed. We present experimental evidence for resonant Raman scattering in ZnO involving bound exciton. A strong enhancement of the 2E1(LO) Raman mode for resonant excitation at energies of the dominant bound exciton lines is apparent. The magnitude of the resonance enhancement for the 2E1(LO) Raman mode is found to vary in dependence of the resonantly excited bound exciton complex and is particular strong for excitation energies matching the I8 line. These results will be discussed in terms of different coupling strengths of the Fröhlich interaction with the neutral and ionized bound exciton complexes. In addition, the recombination and decay dynamics of the bound excitons, phonon replicas and resonantly enhanced Raman modes are discussed. For resonant excitation, a decay constant of the 2E1(LO) Raman mode is found, which is considerably longer as for regular Raman scattering. This result is discussed considering scattering via real excitonic versus virtual states.