Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 49: ZnO: Optical properties
HL 49.7: Talk
Thursday, February 28, 2008, 12:15–12:30, ER 164
Dynamics of charge carrier relaxation and recombination in high quality homoepitaxial-grown and single crystal ZnO — •Markus R. Wagner1, Ute Haboeck1, Axel Hoffmann1, Stefan Lautenschläger2, Joachim Sann2, and Bruno K. Meyer2 — 1Institut für Festkörperphysik, Technische Universität Berlin — 2I. Physikalisches Institut, Justus-Liebig-Universität Gießen
The improvement of growth procedures enables the fabrication of high quality homoepitaxial-grown ZnO layers with negligible amounts of strain near the interface. The optical, electronical and vibrational properties of homoepitaxial grown layers are compared to those of high quality ZnO single crystals. In particular, we report experimental results of time resolved PL and Raman spectroscopy, which provide information on the recombination and relaxation dynamics of charge carriers. The decay times of the observable exciton complexes were studied for different laser energies, resulting in resonant and non-resonant excitation. The dynamics and energy transfer processes were analyzed by probing the free and bound exciton states and phonon replicas, while varying the laser energy. The phonon and carrier dynamics are investigated by time resolved pump and probe spectroscopy. High energy excitation produces hot carriers by two-photon absorption. Their relaxation is accompanied by the emission of phonons, which are studied by time-resolved Raman spectroscopy. The results including resonant and non-resonant Raman measurements are discussed considering electron-phonon and phonon-phonon interactions.