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 microcryst allite thin films. A free exciton photoluminescence lifetime of a few tens of picoseconds and a decay time of a few picoseconds for the stimulated emi ssion were observed. The relatively slow rise time (3ps) for the P band as the result of exciton-exciton scattering compared with the 0.8ps rise time for the N band attributed to electron-hole plasma recombination clearly dis tinguished the two stimulated emission processes.