Luminescence properties of defects in ZnO

We briefly review the luminescence properties of defects in ZnO responsible for broad bands in the visible part of the photoluminescence (PL) spectrum. Bulk and thin-film ZnO samples produced by several companies and research groups were studied at different temperatures and excitation intensities. Steady-state and time-resolved PL was analyzed. We resolved and classified about 10 PL bands having maxima from 1.75 to 2.6 eV at 10 K. Types of transitions and possible assignments of the PL bands are briefly discussed.