LIGHT-INDUCED DEFECTS IN ALUMINUM NITRIDE CERAMICS

Aluminum nitride (AlN) ceramic samples exhibit a dramatic photo-darkening when exposed to UV radiation. In this paper, this phenomenon has been investigated utilizing photo-induced absorption measurements, where the transmission of a visible probe beam is monitored before and after exposure to a UV pump beam. Changes in the probe transmission as large 60% have been observed. The results of this study show that the center responsible for the photo-induced absorption process is an aluminum vacancy-oxygen impurity complex which resides in the AlN lattice. An energy level diagram is constructed which is consistent with these experimental findings.