Excitonic transport in ZnO

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