Variation of N acceptor energy induced by Al-N codoping in ZnO films

Recombination mechanisms of Nitrogen-related emissions in undoped and Al-N codoped ZnO films were investigated by low temperature photoluminescence spectra. The peak near 3.312 meV was existed both in these two kinds of ZnO films. This peak was classified as the transition of the acceptor-bound exciton (A0X) related to NO acceptor. The A0X transition peak in Al-N codoped ZnO films shifted to lower energy comparing with the position of A0X in undoped ZnO films. This phenomenon was induced by the incorporation of Al. A photoluminescence recombination possibly due to free-electron-to-acceptor (FA) transition was observed at temperatures higher than 40 K in Al-N doped ZnO films. The acceptor ionization energy was estimated from the energy position of the FA luminescence to be 183.7 meV. Moreover, the excitation intensity-dependent PL spectra which taken at 80 K in Al-N codoped ZnO film was measured. The luminescence band labeled donor-acceptor pair (DAP) shifts to higher energies with increase excitation intensity.