Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 30: ZnO and Relatives I
HL 30.1: Vortrag
Dienstag, 27. März 2012, 09:30–09:45, EW 202
Resonant phonon and exciton dynamics in ZnO — •Markus R. Wagner1,2, Juan Sebastian Reparaz1, Ronny Kirste1, Gordon Callsen1, Christian Thomsen1, Axel Hoffmann1, and Matthew R. Phillips2 — 1Institute of Solid State Physics, Technische Universitaet Berlin, Berlin, Germany — 2Department of Physics and Advanced Materials, University of Technology Sydney, Sydney, Australia
The optical transitions and dynamics of excitons, phonons, and defects in ZnO are reviewed. The influence of resonant and non-resonant excitation on the decay dynamics of phonons and excitons is studied. A strong resonance enhancement of the second order LO Raman modes is observed for excitation energies in resonance with the dominating bound exciton states. This enhancement is caused by the wave vector dependent Fröhlich interaction which leads to a pronounced coupling of excitons with LO phonons. Time resolved energy dispersive luminescence and Raman measurements enable the differentiation between the resonantly enhanced coherent Raman process and the non-coherent luminescence process. It is shown that the 2LO phonon lifetime greatly depends on the excitation energy and is mainly governed by the lifetime of the real excitonic state under resonant excitation reaching lifetimes of up to 200ps. In addition, temperature dependent time resolved measurements demonstrate that the dissociation of bound excitons at elevated temperatures correlates with a decrease of the resonantly enhanced lifetime of the 2LO Raman modes.