Optically and electrically pumped random lasing from ZnO films annealed at different temperatures

We have investigated the optically and electrically pumped random lasing (RL) actions in ZnO films annealed at low and high temperatures respectively. While the optically pumped RL threshold for the ZnO film annealed at a low temperature, which features stronger light scattering and larger optical loss, is far higher than that for the ZnO film annealed at a high temperature, the electrically pumped RL threshold currents for the two ZnO films are almost the same with the electrical pumping scheme of metal–insulator–semiconductor structure. It is suggested that if the lasing region within the ZnO film is narrow enough in the case of electrical pumping, the strong light scattering can substantially alleviate the adverse effect of large optical loss on the onset of RL.