Vacuum Annealed β-Ga2O3 Recess Channel MOSFETs With 8.56 kV Breakdown Voltage

This letter reports vacuum annealing of lateral field-plated beta-Ga2O3 MOSFETs with significant current recovery and improvement in the on-state resistance, R-on, 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 beta-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, V-br, as compared to polymer passivated MOSFETs. This trend holds for identical gate-drain separation, L-gd, varying from 20 mu m to 60 mu m. Devices show up to 10 times reduction in Ron as compared to previously reported Ron for SU-8 passivated devices. For MBE sample, V-br of 7.16 kV for a L-gd = 40 mu mdevice, with an average field strength of 1.79 MVcm(-1) and peak drain current density of 40 mA/mm, is reported. R-on is 897 Omega. mm, giving Baliga's Figure of Merit (BFOM) as 5.71 MWcm(-2). For a L-gd = 60 mu m device, we report record high breakdown of 8.56 kV with BFoM of 4.9 MWcm(-2). For MOCVD grown sample, a L-gd = 60 mu m device has V-br of 6.11 kV, Ron of 1.98 k Omega. mm and corresponding BFoM of 1.88 MWcm(-2). Transfer Length Method (TLM) analysis indicates incomplete post etch current recovery after vacuum annealing.

Automated summary

This letter presents the vacuum annealing of lateral field-plated beta-Ga2O3 MOSFETs, which leads to significant current recovery and improvement in the on-state resistance after damage induced by Reactive Ion Etching (RIE). MOSFETs based on Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) grown beta-Ga2O3 wafers are fabricated and characterized to study the effects of vacuum annealing. It is observed that vacuum annealed devices show no reduction in breakdown voltages compared to polymer passivated MOSFETs, and the devices exhibit up to 10 times reduction in on-state resistance compared to previously reported SU-8 passivated devices.