The optical absorption spectra of the N vacancy (VN) in proton-irradiated AlxGa1–xN samples were studied. The spectra which were obtained for samples with x = 0.55 to 1 exhibited a peak and a shoulder; with energy positions which depended upon the Al mole fraction. The peak and shoulder in the optical absorption spectra were interpreted as being transitions from the valence band to the VN energy levels located below the conduction band in samples with x > 0.55. The results were used to extrapolate the VN energy level positions in samples with x = 0 to 0.55. A linear fit to the observed VN energy level yielded E(VN) = 4.230 + 0.680x (eV) for all values of x. Thermal annealing of various samples showed that the total integrated area, which was directly proportional to the defect density, of the absorption band that was attributed to the N vacancy decreased as the annealing temperature was increased.

Observation of Nitrogen Vacancy in Proton-Irradiated AlxGa1–xN. Q.Zhou, M.O.Manasreh, M.Pophristic, S.Guo, I.T.Ferguson: Applied Physics Letters, 2001, 79[18], 2901-3