Temperature dependence of near ultraviolet photoluminescence in ZnO/(Mg, Zn)O multiple quantum wells

We report on temperature dependence of excitonic photoluminescence (PL) fro m ZnO/(Mg, Zn)O multiple quantum wells (MQWs). Two kinds of MQWs having dif ferent barrier heights grown by laser molecular-beam epitaxy showed signifi cantly different temperature dependences of PL spectra; in ZnO/Mg0.27Zn0.73 O MQWs, the PL peak energy at 50-200 K was a monotonically increasing funct ion of temperature, which was opposite to that ascribed by band gap shrinka ge. Moreover, spectra taken at 95-200 K encompassed two peaks, both of whic h originated from recombination of localized excitons. The temperature-indu ced shift (redshift-blueshift-peak duplication-redshift) at 5-300 K is caus ed by a change in the exciton dynamics with increasing temperature due to i nhomogeneity and the exciton localization effect. On the other hand, the co rresponding dependence in ZnO/Mg0.12Zn0.88O MQWs (lower barrier height) was similar to that in bulk II-VI semiconductors. (C) 2001 American Institute of Physics.