Femtosecond Time-Resolved Exciton Recombination Dynamics in ZnO Microcrystallite Thin Films at Room Temperature

We report the femtosecond time-resolved studies of room temperature exciton recombination and ultrafast stimulated emission dynamics in ZnO microcrystallite thin films. A free exciton photoluminescence lifetime of few tens of picoseconds and a decay time of a few picoseconds for the stimulated emission were observed. The relatively slow rise time (3ps) for the P band as the result of exciton-exciton scattering compared with the 0.8 ps rise time for the N band attributed to electron-hole plasma recombination clearly distinguished the two stimulated emission processes.