The luminescence characteristics of O-related defects were studied, and new results concerning the photoluminescence excitation and photo-stimulated luminescence of irradiated samples were explained in terms of a proposed luminescence mechanism. According to the electronic structure of this nitride, the top of the valence band was made up of N 2p-states, whereas the bottom of the conduction band was made up of Al 3s-orbitals. The O-related defects formed an energy level within the band-gap. An excited state of this level could be expected below the conduction band, based upon the existence of an absorption band at 5.24eV in the photoluminescence excitation spectrum. This excited state seemed to be situated very close to the conduction band because the irradiation of AlN with 5.24eV light resulted not only in luminescence but also in charged defect storage. A 3.5eV photoluminescence band which was detected by the low-dose irradiation of samples at 5.24eV seemed to be due to radiative transitions from the excited state to the ground state of O-related defects.

B.Berzina, L.Trinkler, E.Palcevskis, J.Sils: Materials Science Forum, 1997, 239-241, 145-8