Self-aligned implanted mesa termination enables a high BFOM of 1.64 GW/cm2 and non-edge junction breakdown for vertical GaN SBDs

Abstract

This work demonstrates a self-aligned implanted mesa termination for GaN-on-GaN vertical Schottky barrier diodes (SBDs), and studies its effects on electrical characteristics and breakdown behaviors of diodes. A self-aligned mesa termination with nitrogen implantation (SNT) has been proposed and fabricated to alleviate electric field crowding and suppress the sidewall leakage current near the edge of Schottky junction, as explained by technology computer-aided design (TCAD) simulations and validated through emission microscopy images. The SBD with SNT (SNT-SBD) exhibits an enhanced breakdown voltage (BV) from 224 to 615 V, achieving a critical electric field of 2.19 MV/cm and a high Baliga Figure of Merit 1.64 GW/cm2. Meanwhile, as predicted by the simulation-optimized structure, it is observed that the destructive breakdown ideally occurs in the non-edge active region of the Schottky junction, not at the common edge region. The as-fabricated SNT-SBD maintains a low normalized dynamic on-resistance below 1.03 under a high reverse bias of 550 V (∼90% BV) and exhibits negligible forward performance degradation under a pulsed off-state stress test, indicating minimized defect densities in GaN materials and the effectiveness of the optimized fabrication processes. This efficient termination technology potentially holds promise as a building block for high-voltage vertical power devices and offers a valuable process solution for investigating the electrical characteristics of wide-bandgap materials under high-voltage conditions.