Time-dependent gate breakdown reliability and gate leakage improvements in p-GaN MOS-HEMTs using Al₂O₃ gate dielectric

In this study, a 10 nm Al₂O₃ layer was deposited on the p-type gallium nitride (p-GaN) layer using thermal atomic layer deposition to form a metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT), designed to achieve lower gate leakage current. For comparison, a conventional p-GaN gate HEMT with an ohmic gate contact was employed. Transfer length method analysis of device resistance confirmed a reliable ohmic contact on the source/drain, with a low sheet resistance (R_sh) indicating a high-density two-dimensional electron gas in the access region, unaffected by the residual p-GaN etching process. To further explore the role of post-deposition annealing (PDA) in MOS-HEMTs, the characteristics of devices with and without PDA treatment were evaluated. Our conventional ohmic gate device exhibited excellent enhancement-mode (E-mode) characteristics, with all devices demonstrating low reverse gate leakage below 1 × 10-⁶ mA/mm. Compared to ohmic-gate HEMTs, PDA-treated devices showed reduced gate leakage and improved reliability, achieving a 10-year lifetime at 7.2 V through time-dependent gate breakdown analysis, despite reduced ON-state performance. We analyzed the differences among the three devices based on their respective gate leakage currents.