EFFECT OF TRACE CARBON ON THE UV-INDUCED BEHAVIOR OF ALUMINUM NITRIDE CERAMICS

The effect of uv irradiation on the material properties of AlN containing low oxygen content (<0.3 wt. %) has been investigated. Upon irradiation with a 150 W Hg-Xe arc lamp, increases in dielectric loss and thermal conductivity drops were observed. Changes in the optical properties, including formation of an absorption band at 650 nm, and photodarkening were also observed. All samples were characterized for trace impurities including carbon, calcium, and oxygen. The magnitude of the uv-induced drops in dielectric loss and the absorption at 650 nm of samples tested were found to depend on the presence of trace levels of residual carbon. UV-induced increases in dielectric loss show an inverse relationship, and formation of an absorption band shows a direct relationship to carbon content.