UV induced dielectric loss in AlN ceramics

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Abstract
The dissipation factor of aluminum nitride ceramics (AlN), doped with various concentrations of oxygen, is probed at 1 kHz before and after exposure to UV radiation. The results of this study show that UV photogenerated carriers, which are trapped at charged oxygen impurity related defect sites, are responsible for the observed dielectric loss. A simple energy level diagram is presented that outlines trapped carrier distributions within the AlN bandgap and is consistent with the experimentally observed changes in dissipation factor as a function of time, UV exposure, and exposure to visible light, which liberates carriers from charged trap sites.