Photoluminescence and selective photoluminescence experiments were used to analyze the near-bandedge emission spectra of unintentionally doped epilayers. It was shown that the various band-edge emission transitions involved only donor centers. The lines could be divided into 2 groups. Those lying on the low-energy side consisted of recombinations of neutral-donor bound exciton complexes, while those lying just below the A free excitonic emission corresponded to donor-to-valence band transitions. One of the donors was identified as being In. The emission energy of the In-donor bound exciton, the spectra of the bound exciton excited states, the In-related D0h transition energy, and the electronic spectrum of the In-donor were established. The binding energies of another 3 donor centers were evaluated. The occurrence of 2 of these centers was shown to depend upon the stoichiometry, as revealed by annealing experiments in an O2 atmosphere.

Near Band Edge Emission of MBE Grown ZnO Epilayers - Identification of Donor Impurities and O2 Annealing Effects. Morhain, C., Teisseire-Doninelli, M., Vézian, S., Deparis, C., Lorenzini, P., Raymond, F., Guion, J., Neu, G.: Physica Status Solidi B, 2004, 241[3], 631-4