Bevel Edge Termination for Vertical GaN Power Diodes

Edge termination for vertical power devices presents a significant challenge, as improper termination can result in devices with a breakdown voltage significantly less than the ideal infinite-planar case. Edge termination for vertical GaN devices is particularly challenging due to limitations in ion implantation for GaN, and as such this work investigates a bevel edge termination technique that does not require implantation and has proven to be effective for Si and SiC power devices. However, due to key differences between GaN versus Si and SiC p-n junctions (specifically, a grown versus an implanted junction), this technology needs to be reevaluated for GaN. Simulation results suggest that by leveraging the effective bevel angle relationship, a 10-15° physical bevel angle can yield devices with 85-90% of the ideal breakdown voltage. Results are presented for a negative bevel edge termination on an ideally 2 kV vertical GaN p-n diode.