Photoluminescence relevant to intrinsic defects of ZnO crystal by Zn doping

ZnO single crystal wafers were treated by thermal diffusion Zn doping to study the intrinsic defects in ZnO, optical properties of samples which were obtained under different diffusion time and cooling mode were investigated by photoluminescence (PL) spectra. It can be seen that the UV intensity enhanced clearly by Zn doping, and when prolonging diffusion time, the visible band also appeared. According to the analysis of the thermal diffusion mechanism, it can be concluded that Zn-i formed in the first stage of diffusion, and then Zn-o generated later. Based on the energy levels of these defects, the visible peak at 510nm is probably from Zn-o. Low temperature (LT) PL spectrum of ZnO sample with the strongest UV peak was measured and investigated. At 10K, the neutral donor-bound excitons dominate in the PL spectrum. Two electron satellite (TES) transitions of the donor-bound excitons appeared in the chart allow us to determine the donor binding energy around 52meV, which is consisted with Zn-i defect. Therefore, the Zn-i is an important shallow defect contributing to the conductance of ZnO at room temperature.