Breakdown up to 13.5 kV in NiO/β-Ga<sub>2</sub>O<sub>3</sub> Vertical Heterojunction Rectifiers
Jian-Sian Li, Hsiao-Hsuan Wan, Chao-Ching Chiang, Timothy Jinsoo Yoo, Meng-Hsun Yu, F. Ren, Honggyu Kim, Yu‐Te Liao, S. J. Pearton
Abstract
Vertical heterojunction NiO/ β n-Ga 2 O/n + Ga 2 O 3 rectifiers with 100 μ m diameter fabricated on ∼17–18 μ m thick drift layers with carrier concentration 8.8 × 10 15 cm −3 and employing simple dual-layer PECVD SiNx/SiO 2 edge termination demonstrate breakdown voltages (V B ) up to 13.5 kV, on-voltage (V ON ) of ∼2.2 V and on-state resistance R ON of 11.1–12 mΩ.cm 2 . Without edge termination, the maximum V B 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 -Ga 2 O 3. For large area (1 mm diameter) heterojunction deives, the maximum V B was 7.2 kV with optimized edge termination and 3.9 kV without edge termination. The associated maximum power figure-of-merit, V B 2 /R ON 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 V B of 3.6 kV with edge termination and 2.7 kV without edge termination, but lower V ON 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 Ga 2 O 3 . The key advances are thicker, lower doped drift layers and optimization of edge termination design and deposition processes.