The influence of defects and impurities in polycrystalline AlN films on the violet and blue photoluminescence

The influence of defects and impurities in polycrystalline aluminum nitride films on the violet and blue photoluminescence properties was investigated. The photoluminescence spectra show a broad emission band in the range from 380 nm to 550 nm, which consists of two components of the violet band centered at 400 nm and the blue band centered at 480 nm. When the native defects reduce and the crystal quality is improved by annealing in nitrogen atmosphere, the shoulder band around 480 nm declines. The center of the violet luminescence shifts from 400 nm to about 440 nm as the oxygen content increase from 2.9 at.% to 12.3 at.%. The intensity and the center of the violet emission vary mostly linearly with the oxygen content. Combining the results of X-ray diffraction and Auger Electron Spectroscopy, the violet emission around 400 nm (3.09 eV) can be attributed to the transition from the shallow donor to the deep acceptor related to the oxygen impurity, while the blue emission around 450 nm (2.58 eV) may originate from transition from the shallow donor to the deep acceptor related to the native defect.