Recombination dynamics of excitons in ZnO/ZnMgO multiple quantum wells grown on silicon substrate

摘要

Time-resolved photoluminescence measurements were taken at various temperatures to investigate the behavior of excitons in ZnO/Zn_(0.9)Mg_(0.1)O multiple quantum wells (MQWs) grown on Si substrate using epitaxial Lu_2O_3 buffer layer by pulsed laser deposition. The temperature dependence of the radiative decay times of the emissions from both the ZnO wells and the Zn_(0.9)Mg_(0.1)O barriers is analyzed. The radiative lifetime of the well excitons exhibits linear dependence till room temperature, indicating that the excitons are effectively confined in the quantum wells and do not ther-malize to 3D excitons. The short radiative lifetime of ～ 1.15 ns indicates high radiative recombination rate at room temperature. The radiative lifetime of the barrier excitons shows approximately T~(1/2) dependence on temperature. In combination with the spectral dependence of the PL lifetime, it indicates localization of excitons in the barrier due to compositional fluctuation. The short radiative lifetime at room temperature and the weak localization energy of ～9 meV suggest that our MQWs are of high optical quality.