Dependence of reverse leakage on the edge termination process in vertical GaN power device

Abstract

The trench gate MOSFET represents a prominent device architecture among the GaN based vertical devices currently investigated for the next generation of power electronics. A low leakage current level in off-state under high drain bias is of great importance for vertical transistors since it is a crucial feature for high breakdown voltage and device reliability. The off-state drain leakage originates from different sources in the vertical trench gate MOSFET. Besides the trench gate module, the leakage paths at the dry-etched sidewall of the lateral edge termination can also significantly contribute to the off-state drain-current. In this report, the influence of each relevant process step on the drain leakage current in off-state is investigated utilizing specific test structures on high-quality GaN epitaxial material which mimic the lateral edge termination of the MOSFET. Electrical characterization reveals the sensitivity of the leakage current to plasma-related processes. A termination technology is presented that results in low leakage current while including thick dielectric layers from plasma-assisted deposition as intended for fabrication of a field plate structure over the edge termination.

Vertical GaN MOSFET Power Devices

“…These techniques effectively mitigate the risk of edge breakdown, offering simplicity and scalability. Nevertheless, the dry-etched sidewalls in edge termination introduce a leakage path that significantly impacts the off-state drain current [111]. Ion implantation has demonstrated significant improvements in Si and SiC devices by protecting the dielectric at the trench bottom and serving as a body contact.…”