Superior high temperature performance of 8 kV NiO/Ga2O3 vertical heterojunction rectifiers

Abstract

NiO/β-Ga₂O₃ vertical rectifiers exhibit near-temperature-independent breakdown voltages (V_B) of >8 kV to 600 K. For 100 μm diameter devices, the power figure of merit (V_B)²/R_ON, where R_ON is the on-state resistance, was 9.1 GW cm⁻² at 300 K and 3.9 GW cm⁻² at 600 K. By sharp contrast, Schottky rectifiers fabricated on the same wafers show V_B of ∼1100 V at 300 K, with a negative temperature coefficient of breakdown of 2 V K⁻¹. The corresponding figures of merit for Schottky rectifiers were 0.22 GW cm⁻² at 300 K and 0.59 MW cm⁻² at 600 K. The on–off ratio remained >10¹⁰ up to 600 K for heterojunction rectifiers but was 3 orders of magnitude lower over the entire temperature range for Schottky rectifiers. The power figure of merit is higher by a factor of approximately 6 than the 1-D unipolar limit of SiC. The reverse recovery times were ∼26 ± 2 ns for both types of devices and were independent of temperature. We also fabricated large area, 1 mm² rectifiers. These exhibited V_B of 4 kV at 300 K and 3.6 kV at 600 K. The results show the promise of using this transparent oxide heterojunction for high temperature, high voltage applications.