NiO Junction Termination Extension for Ga2O3 Devices: High Blocking Field, Low Capacitance, and Fast Switching Speed

This work investigates the blocking electric field, capacitance, and switching speed of the p-type NiO based junction termination extension (JTE) for vertical Ga2O3 devices. The JTE comprises multiple NiO layers sputtered on the surface of Ga2O3 drift region, the acceptor concentration and length of which are carefully optimized. This NiO JTE enabled a breakdown voltage over 3 kV in vertical Ga2O3 diodes with a parallel-plate junction field of 4.2 MV/cm. Large-area Ga2O3 p-n diodes with a current over 1 A were fabricated to evaluate the JTE's capacitance and switching characteristics. The JTE accounts for only, ~11 % of the junction capacitance of this 1 A diode, and the percentage is expected to be even smaller for higher-current diodes. The turn-ON/OFF speed and reverse recovery time of the diode are comparable to commercial SiC Schottky barrier diodes. These results show the good promise of NiO JTE as an effective edge termination for Ga2O3 power devices.