An Investigation of Light Induced Defects in Aluminum Nitride Ceramics

Abstract

ABSTRACTIt has been observed that aluminum nitride (AIN) ceramics exhibit a significant photo-darkening when exposed to UV or X-ray radiation, though the origin of this effect has never been understood. In this study, the optical character of these defects is investigated utilizing a UV-pump, visible-probe arrangement, where very large changes ΔT in the probe transmission T (induced absorption) are observed after excitation (Δ/T-0.60). These experiments reveal that the photo-darkening is due to the creation of light induced defects, with an energy level deep in the AIN bandgap. Utilizing these results, a light induced defect formation model is proposed which is consistent with the known defect chemistry of this material.