Polarized photoluminescence spectra of the non-polar ZnO single crystals annealed at different temperatures in air were investigated, for which the whole emission spectra from visible up to ultraviolet range for zinc and oxygen defects states were taken separately via the parallel and the crossed polarization geometries, respectively. It was also deduced from the spectra that the density of oxygen vacancy defects attains minimum for the sample annealed at 400 C, and above which both anharmonic effects of ultraviolet emission and enhancement of defect-related deep band emission band due to the increase of oxygen and zinc vacancy defects were observed.

Identification of Zinc and Oxygen Vacancy States in Nonpolar ZnO Single Crystal Using Polarized Photoluminescence. J.Liu, Y.Zhao, Y.J.Jiang, C.M.Lee, Y.L.Liu, G.G.Siu: Applied Physics Letters, 2010, 97[23], 231907