Reliability Improvements in AlGaN/GaN Schottky Barrier Diodes With a Gated Edge Termination

Abstract

This paper focuses on the time-dependent breakdown of the AlGaN/GaN Schottky barrier diodes with a gated edge termination (GET) submitted to high-voltage stress. The impact of the GET structure, the passivation layer thickness, and a preclean process (sulfuric acid and hydrogen peroxide mixture + ammonia and hydrogen peroxide mixture) before the GET layer deposition on the time to breakdown ${t}_{\text {BD}}$ is analyzed. Initially, a reference structure with a single-GET structure, a thick passivation layer and excellent performance under dc, and pulse characterization is submitted to stress. The results show that the time to failure follows a Weibull distribution with high shape parameter values ( $\beta \sim \text {3}$ and/or $\beta \sim \text {5}$ ) related to intrinsic failure mechanisms. The exponential dependence of ${t}_{\text {BD}}$ on the stress voltage suggests a degradation driven by the electric field, while lower thermal activation energies indicate that temperature acts as a weak acceleration factor. A more uniform distribution of the electric field—by adding an additional peak (double-GET structure) or with more equilibrated peaks (thin passivation structure)—and a more aggressive preclean process before the GET layer deposition improves the breakdown voltage and prolongs the device lifetime.