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Edge termination is the enabling building block of power devices to exploit the high breakdown field of wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductors. This work presents a heterogeneous junction termination extension (JTE) based on p-type nickel oxide (NiO) for gallium oxide (Ga2O3) devices. Distinct from prior JTEs usually made by implantation or etch, this NiO JTE is deposited on the surface of Ga2O3 by magnetron sputtering. The JTE consists of multiple NiO layers with various lengths to allow for a graded decrease in effective charge density away from the device active region. Moreover, this surface JTE has broad design window and process latitude, and its efficiency is drift-layer agnostic. The physics of this NiO JTE is validated by experimental applications into NiO/Ga2O3 p–n diodes fabricated on two Ga2O3 wafers with different doping concentrations. The JTE enables a breakdown voltage over 3.2 kV and a consistent parallel-plate junction field of 4.2 MV/cm in both devices, rendering a power figure of merit of 2.5–2.7 GW/cm2. These results show the great promise of the deposited JTE as a flexible, near ideal edge termination for WBG and UWBG devices, particularly those lacking high-quality homojunctions. 

Medium-voltage (MV) power electronic devices are widely used in renewable energy processing, electric grids, pulse power systems, etc. Current MV devices are mainly made of Si and SiC. This paper presents our recent efforts in developing a new generation of MV devices based on the multi-channel AlGaN/GaN platform and many new device designs involving charge balance, fin, and Cascode. The specific on-resistance of our 10 kV-class GaN Schottky barrier diodes and normally-OFF transistors is ~40 mΩ•cm 2 , rendering a Baliga’s figure of merit exceeding the 1-D unipolar SiC limits. We show the great promise of GaN in medium and high-voltage power applications.