Robust Avalanche in 1.7 kV Vertical GaN Diodes With a Single-Implant Bevel Edge Termination

This work demonstrates a novel junction termination extension (JTE) with a graded charge profile for vertical GaN p-n diodes. The fabrication of this JTE obviates GaN etch and requires only a single-step implantation. A bi-layer photoresist is used to produce an ultra-small bevel angle (similar to 0.1 degrees) at the sidewall of a dielectric layer. This tapered dielectric layer is then used as the implantation mask to produce a graded charge profile in p-GaN. The fabricated GaN p-n diodes show a breakdown voltage (BV) of 1.7 kV (83% of the parallel-plane limit) with positive temperature coefficient, as well as a high avalanche current density over 1100 A/cm(2) at BV in the unclamped inductive switching test. This robust avalanche is ascribed to the migration of the major impact ionization location from the JTE edge to the main junction. This single-implant, efficient, avalanche-capable JTE can potentially become a building block of many vertical GaN devices, and its fabrication technique has wide device and material applicability.

Automated summary

This study presents a novel junction termination extension (JTE) technique with a graded charge profile for vertical GaN p-n diodes. The fabrication process does not require GaN etching and only involves a single-step implantation. The fabricated GaN p-n diodes exhibit high breakdown voltage and robust avalanche current density, making them suitable for various vertical GaN devices.