Reliability improvements in AlGaN/GaN schottky barrier diodes with a gated edge termination

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_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 (β ∼ 3 and/or β ∼ 5) related to intrinsic failure mechanisms. The exponential dependence of t_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.