Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 3: Heterostructures
HL 3.3: Vortrag
Montag, 23. März 2009, 10:45–11:00, BEY 154
Formation of Exciton-Polaritons up to 410 K in ZnO based planar resonators — •Chris Sturm, Helena Hilmer, Rüdiger Schmidt-Grund, Christian Czekalla, Michael Lorenz, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II, Linnéstraße 5, 04103 Leipzig
Exciton-polaritons are quasi particles formed by the coupling of excitons with photonic modes. They can undergo a Bose-Einstein-Condensation (BEC) even at elevated temperatures; for ZnO based resonators the critical temperature at which BEC can occur was predicted up to 560 K. In this work we will present the observation of exciton-polaritons in a ZnO based resonator up to 410 K. This represents the first observation of exciton-polaritons above room temperature. The resonator consists of a half wavelength ZnO microcavity [1] embedded between two Bragg reflectors made of 10.5 layer pairs of YSZ and Al2O3. The exciton-polaritons were observed by means of photoluminescence (PL) and reflectivity (R) measurements at temperatures (10 − 410) K. Taking into account the coupling between only one exciton mode and one cavity-photon mode we were able to describe the observed polariton dispersion as well as its broadening behaviour. Thereby, we obtain a Rabi splitting of about 95 meV (R) and about 90 meV (PL) at 10 K. Furthermore, non-resonant excitation dependent PL measurements of the resonator yield a saturation of the occupation of the ground state, i.e. there is a saturation of the relaxation from an excited state to the ground state.
R. Schmidt-Grund et al., Appl. Phys. B 93, 331 (2008).