Breakdown up to 13.5 kV in NiO/β-Ga2O3 Vertical Heterojunction Rectifiers

Abstract

Vertical heterojunction NiO/β n-Ga2O/n+ Ga2O3 rectifiers with 100 μm diameter fabricated on ∼17–18 μm thick drift layers with carrier concentration 8.8 × 1015 cm−3 and employing simple dual-layer PECVD SiNx/SiO2 edge termination demonstrate breakdown voltages (VB) up to 13.5 kV, on-voltage (VON) of ∼2.2 V and on-state resistance RON of 11.1–12 mΩ.cm2. Without edge termination, the maximum VB was 7.9 kV. The average critical breakdown field in heterojunctions was ∼7.4–9.4 MV. cm−1, within the reported theoretical value range from 8–15 MV.cm−1 for β-Ga2O3. For large area (1 mm diameter) heterojunction deives, the maximum VB was 7.2 kV with optimized edge termination and 3.9 kV without edge termination. The associated maximum power figure-of-merit, VB 2/RON is 15.2 GW·cm−2 for small area devices and 0.65 GW.cm−2 for large area devices. By sharp contrast, small area Schottky rectifiers concurrently fabricated on the same drift layers had maximum VB of 3.6 kV with edge termination and 2.7 kV without edge termination, but lower VON of 0.71–0.75 V. The average critical breakdown field in these devices was in the range 1.9–2.7 MV. cm−1, showing the importance of both the heterojunction and edge termination. Transmission electron microscopy showed an absence of lattice damage between the PECVD and sputtered films within the device and the underlying epitaxial Ga2O3. The key advances are thicker, lower doped drift layers and optimization of edge termination design and deposition processes.