New fine structure of red luminescence in ZnO observed under exciton resonance excitation

The RL can be extremely enhanced at the incident frequency in resonance with the donor exciton and the intensities of some adjacent lines separated by similar to 4 meV are thermally populated with the increase in temperature. The new structured RL was studied in the terms of photoluminescence (PL) and PL excitation spectra and the origin was discussed taking into account the internal transitions of transition metal elements, structure defects, and native point defects. There is a great possibility that the new structured RL arises from the excited states converted from bound excitons, for example, the excitons or the electron and hole pairs bounded by the donor and acceptor pairs (DAPs) of O and Zn vacancies, because the binding energy determined by the equation of DAP fluorescence is highly in accordance with the theoretic values reported in the literature. (C) 2019 Author(s).