Such a spectrum can be deconvoluted into three bands that can be assigned to so-called green luminescence (GL), yellow luminescence (YL) and red luminescence (RL) of ZnO. The slightly asymmetric GL band with the maximum around 490 nm (2.53 eV) and FWHM = 0.53 eV is very characteristic for ZnO and was observed many times in various ZnO-related materials 34 . This luminescence is commonly assigned to intrinsic donor-type point defects such as V O . The band of YL with a maximum around 565 nm (2.19 eV) was previously observed in melt-grown samples of ZnO 35 and ascribed to deep V Zn -related acceptors with the activation energy of ~0.4 eV. The shape of RL band varies from sample to sample but its maximum remains between 630 and 640 nm.