Insights into the nature of optically active defects of ZnO

ZnO is a wide bandgap semiconductor in which point and extended defects tune its optoelectronic properties, and the identification of essential microscopic ingredients for such a tunning is a challenging task. In this work, we combine experimental techniques with theoretical calculations at the atomistic level to investigate a variety of neutral and charged point defects along with their response to thermal treatment by optical and transport measurements. We obtain photoluminescence spectra compatible with simulations of Zn vacancies, oxygen interstitials, and complexes combining vacancies of Zn and O. Annealing is an effective way to neutralize the oxygen interstitials, being an effective mechanism to control the ZnO optoelectronic properties. The photosensitive behavior is explored in temperature-dependent electrical responses under different cooling-down modes. The role of both, extended and point defects, in the photoexcitation with energies below and above the bandgap is also discussed.