Hydrogen-Modulated Step Graded Junction Termination Extension in GaN Vertical p-n Diodes

Junction termination extension (JTE) is a mature edge termination structure in Si and SiC power devices, but remains a technical challenge in GaN due to lack of mature selective area doping technique. In this work, GaN vertical p-n diodes with Hydrogen-Modulated Step Graded JTE (HMSG-JTE) are realized by gradually enlarging photolithography windows for hydrogen plasma treatment and controlled thermal diffusion of hydrogen in p-GaN. HMSG-JTE leads to a gradually decreasing hole distribution outwards from the main junction, which laterally spreads the electric field and mitigates the electric field peak under reverse bias. Consequently, the breakdown voltage of vertical GaN p-n diode is successfully boosted from 661 V (with hydrogen-plasma-based edge termination) to 1489 V with HMSG-JTE.