Excitonic transport in ZnO

The temperature dependence of diffusion length and lifetime or diffusivity of the free exciton is measured in a commercial ZnO-substrate and in an epitaxial ZnO quantum well using nm-spatially and ps-time resolved cathodoluminescence (CL) spectroscopy. The characteristic temperature dependence of the exciton mobility is a fingerprint of the underlying excitonic scattering processes. Since excitons are neutral particles scattering at ionized impurities should be not effective. With decreasing temperature diffusion lengths and lifetimes give rise to a monotonous increase of the excitonic mobility. Two different methods for determining the excitonic transport parameters will be presented. On the one hand we are able to perform completely pulsed excitation experiments and on the other hand a combination of cw- and pulsed excitation in two independent measurements are needed.