Electron-beam-induced current and cathodoluminescence studies of thermally activated increase for carrier diffusion length and lifetime in n-type ZnO

Temperature dependence of the minority carrier diffusion length and lifetime in bulk n-type ZnO was studied using electron-beam-induced current and cathodoluminescence techniques. The diffusion length was observed to increase exponentially over the temperature range from 25 °C to 125 °C, yielding activation energy of 45±2meV. Concomitant decrease of the cathodoluminescence intensity for the near-band-edge transition was also observed. The activation energy determined by optical measurements was 58±7meV. The larger minority carrier diffusion length and smaller luminescence intensity are attributed to the increased lifetime of nonequilibrium holes in the valence band at elevated temperatures.