Vacuum Annealed β-Ga₂O₃Recess Channel MOSFETs With 8.56 kV Breakdown Voltage

This letter reports vacuum annealing of lateral field-plated β-Ga2O3 MOSFETs with significant current recovery and improvement in the on-state resistance, Ron, after Reactive Ion Etching (RIE) induced damage. We fabricate and characterize MOSFETs based on Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) grown β-Ga2O3 wafers to better understand the effects of vacuum annealing. We see a clear trend of vacuum annealed devices showing no reduction in breakdown voltages, Vbr, as compared to polymer passivated MOSFETs. This trend holds for identical gate-drain separation, Lgd, varying from 20 μm to 60 μm. Devices show up to 10 times reduction in Ron as compared to previously reported Ron for SU-8 passivated devices. For MBE sample, Vbr of 7.16 kV for a Lgd = 40 μm device, with an average field strength of 1.79 MVcm-1 and peak drain current density of 40 mA/mm, is reported. Ron is 897 Ω. mm, giving Baliga's Figure of Merit (BFOM) as 5.71 MWcm-2. For a Lgd = 60 μm device, we report record high breakdown of 8.56 kV with BFoM of 4.9 MWcm-2. For MOCVD grown sample, a Lgd = 60 μm device has Vbr of 6.11 kV, Ron of 1.98 kΩ. mm and corresponding BFoM of 1.88 MWcm-2. Transfer Length Method (TLM) analysis indicates incomplete post etch current recovery after vacuum annealing.