Enhanced photoluminescence caused by localized excitons observed in MgZnO alloy

Temperature-dependent photoluminescence of MgZnO alloy film has been studied, and it is found that the emission intensity increases significantly at a certain temperature range and then decreases when increasing temperature further. The anomalous increase is resulted from the localized excitons in MgZnO alloy, as revealed by the enhanced second-order longitudinal optical phonon in the Raman spectrum of the MgZnO film. A schematic model was suggested to depict the carrier transportation process in the MgZnO film considering the existence of localized exciton states. The results reported in this paper indicate that localized excitons in MgZnO alloy can result in greatly enhanced emission efficiency, which is eagerly wanted for the application of ZnO-based materials in high-efficiency light-emitting devices.