Epilayers of AlN, grown by metalorganic chemical vapor deposition, were implanted with Co ions and studied using deep ultra-violet photoluminescence methods. A photoluminescence emission peak at 5.87eV (at 10K) was observed for Co-implanted AlN epilayers. It was absent from as-grown AlN epilayers. The temperature dependence of the photoluminescence intensity of the 5.87eV emission line revealed an ion-implantation induced defect with an energy level that was about 0.260eV below the conduction band. The 5.87eV emission line was believed to be due to a band-to-impurity transition which involved the N vacancy (VN) in ion-implanted AlN. The experimentally determined energy level of the N vacancy was in reasonable agreement with the calculated value of 0.30eV. From the band-to-impurity transition which involved VN, the energy band-gap of AlN was deduced to be 6.13eV. This was consistent with previous results. The data suggested that N vacancies in AlN could not make any significant contribution to n-type conductivity, due to a large binding energy as well as a large formation energy.

Optical Properties of the Nitrogen Vacancy in AlN Epilayers. N.Nepal, K.B.Nam, M.L.Nakarmi, J.Y.Lin, H.X.Jiang, J.M.Zavada, R.G.Wilson: Applied Physics Letters, 2004, 84[7], 1090-2