The Zn-vacancy related green luminescence and donor-acceptor pair emission in ZnO grown by pulsed laser deposition

Low temperature (10 K) photoluminescence study shows that green luminescence (GL) peaked at 2.47 eV and near band edge (NBE) emission at 3.23 eV are introduced in undopd ZnO grown by pulsed laser deposition (PLD) after the 900°C annealing. The NBE emission exhibiting blue shift with increasing temperature is assigned to the transitions of donor-acceptor-pair (DAP)/free-electron-to-acceptor (FA). Positron annihilation spectroscopy (PAS) study shows that the introduction of the GL is correlated with the formation of the Zn vacancy-related defect (VZn). Comparing the transition energies of VZn obtained by the previous first principle calculation [Janotti and Van de Walle, Phys. Rev. B 76, 165202 (2007)], the GL is associated with the transition from the conduction band to the ε(-/2-) state of VZn and the DAP/FA emission involves the acceptor level ε(0/-) of VZn.