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HL: Fachverband Halbleiterphysik

HL 36: Heterostructures

HL 36.4: Vortrag

Donnerstag, 29. März 2007, 10:45–11:00, H14

Exciton-Polaritons at room temperature in a planar ZnO resonator structure — •Rüdiger Schmidt-Grund, Bernd Rheinländer, Christian Czekalla, Gabriele Benndorf, Holger Hochmuth, Michael Lorenz, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig

The wurtzite-structure II-VI-semiconductor ZnO has currently gained substantial interest because of its attractive properties for possible applications in optoelectronics. Due to the large binding energy of about 60meV, excitons in ZnO are stable at room temperature. This makes ZnO based resonators attractive for Bose-Einstein condensation of exciton-polaritons and therefore for the realization of cavity coupled exciton-polariton lasers operating at room temperature.

We report on coupling of exciton and photon modes observed in an all oxide planar resonator consisting of a λ/2 ZnO cavity, which acts simultaneously as active medium. It is embedded between lower and upper Bragg reflectors consisting of λ/4 stacks of the materials ZrO₂ and MgO (each 10.5 layer pairs). The resonator structure has been deposited using pulsed-laser deposition on sapphire substrate. The exciton-polariton modes have been observed in both reflectivity and photoluminescence measurements at temperatures between 4K and 306K and at room temperature at various incidence angles respective exit angles of the light. We have observed an energy splitting of the exciton-polariton branches of about 50meV, which is as large as the best values reached for the well known material system AlInGaN.