Temperature dependence and decay times of zinc and oxygen vacancy related photoluminescence bands in zinc oxide

A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc- and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are both involved in the deep band emission (DBE) that is often observed in ZnO but exhibit different optical characteristics promoting defect identification. In particular, when decreasing the PL measurement temperature the energy peak position of the VO-related band decreases while that of VZn increases. Secondly, phonon replicas are clearly observed in the DBE spectra in the sample containing VZn. Finally, the characteristics of the DBE decay time for VZn- and VO-enriched samples are also different. Specifically, for the VZn-enriched sample the decay curves show strong wavelength dependence and generally slower decay components as compared to the sample enriched with VO.