Enhanced Avalanche (2.1 kV, 83 A) in NiO/Ga<inf>2</inf>O<inf>3</inf> Heterojunction by Edge Termination Optimization

Abstract

Avalanche capability is an essential robustness of power devices for system applications. Edge termination (ET) is the key design to enable avalanche as it allows the device junction to reach the material's avalanche field (EAVA) without premature breakdown. Avalanche ET design is very difficult in ultra-wide bandgap (UWBG) devices due to the high EAVA. This work unveils the enabling edge termination for a robust, circuit-level avalanche in a UWBG NiO/Ga2O3 p-n heterojunction diode (HJD), and correlates the ET design with avalanche energy. Such ET combines a NiO junction termination extension (JTE) and a high-k oxide-based (BaTiO3) field plate. The avalanche voltage and current are found to be enhanced from 761V/26A to 2135V/83A by lowering the p-type NiO doping in this high-k enhanced JTE. The achieved avalanche energy density (11.3 J/cm2) sets a new record in heterojunction devices and is comparable to the highest values reported in SiC and GaN homojunctions. The enhanced avalanche is attributable to the spread-out distributions of electric field and impact ionization. In addition, device shows no degradation after 10,000 cycles of 2.1kV/83A avalanche stress. These results open the path to design the avalanche-robust UWBG power devices.