Observation of nitrogen vacancy in proton-irradiated AlxGa1-xN

The optical absorption spectra of nitrogen vacancy (V-N) in proton-irradiat ed AlxGa1-xN samples are observed. The spectra obtained for samples with 0. 55 less than or equal tox less than or equal to1 exhibit a peak and a shoul der with their energy positions dependent on the Al mole fraction. The peak and shoulder in the optical absorption spectra were interpreted as transit ions from the valence band to the V-N energy levels located below the condu ction band in samples with x >0.55. The results were used to extrapolate th e V-N energy level positions in samples with 0 less than or equal tox less than or equal to0.55. A linear fit of the observed V-N energy level yields E(V-N)=4.230+0.680x (eV) for all values of x. Thermal annealing of various samples shows that the total integrated area, which is directly proportiona l to the defect density, of the absorption band attributed to the nitrogen vacancy is decreased as the annealing temperature is increased. (C) 2001 Am erican Institute of Physics.