Defect-induced optical breakdown in aluminum nitride and gallium nitride epitaxial films

摘要

We are investigating conductive gallium nitride films grown on c-plane sapphire for use in a new area of application, high-power optoelectronics. It was found that optically-induced damage in gallium nitride-based transparent conductive thin films occurs at incident laser intensities significantly greater than in conventional metal-oxide based thin films. Furthermore, damage in gallium nitride epi-layers displays a unique morphology consisting of discrete, faceted pits which appear to initiate within fast-grown layers when exposed to high intensity near-infrared laser irradiation. We developed an integrated laser damage system with in-situ diagnostics to probe this damage mode and conducted damage tests of aluminum nitride and gallium nitride/aluminum nitride samples grown under various conditions. Through in-depth analyses using optical microscopy and results from high-throughput damage tests, this paper elucidates some of the prevailing damage processes and design considerations for gallium nitride transparent conductive films important for emerging high-power laser applications.