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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. 

We report the first experimental demonstration of a vertical superjunction device in GaN. P-type nickel oxide (NiO) is sputtered conformally in 6μm deep n-GaN trenches. Sputter recipe is tuned to enable 1017 cm −3 level acceptor concentration in NiO, easing its charge balance with the 9×1016 cm −3 doped n-GaN. Vertical GaN superjunction p-n diodes (SJ-PNDs) are fabricated on both native GaN and low-cost sapphire substrates. GaN SJ-PNDs on GaN and sapphire both show a breakdown voltage (BV) of 1100 V, being at least 900 V higher than their 1-D PND counterparts. The differential specific on-resistance (RON,SP) of the two SJ-PNDs are both 0.3mΩ⋅ cm 2 , with the drift region resistance (RDR,SP) extracted to be 0.15mΩ⋅ cm 2 . The RON,SP∼BV trade-off is among the best in GaN-on-GaN diodes and sets a new record for vertical GaN devices on foreign substrates. The RDR,SP∼BV trade-off exceeds the 1-D GaN limit, fulfilling the superjunction functionality in GaN. 

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. 

Multidimensional power devices can achieve performance beyond conventional limits by deploying charge‐balanced p‐n junctions. A key obstacle to developing such devices in many wide‐bandgap (WBG) and ultra‐wide bandgap (UWBG) semiconductors is the difficulty of native p‐type doping. Here the WBG nickel oxide (NiO) as an alternative p‐type material is investigated. The acceptor concentration (N_A) in NiO is modulated by oxygen partial pressure during magnetron sputtering and characterized using a p‐n⁺heterojunction diode fabricated on gallium oxide (Ga₂O₃) substrate. Capacitance and breakdown measurements reveal a tunableN_Afrom < 10¹⁸ cm⁻³to 2×10¹⁸ cm⁻³with the practical breakdown field (E_B) of 3.8 to 6.3 MV cm⁻¹. ThisN_Arange allows for charge balance to n‐type region with reasonable process latitude, andE_Bis high enough to pair with many WBG and UWBG semiconductors. The extractedN_Ais then used to design a multidimensional Ga₂O₃diode with NiO field‐modulation structure. The diodes fabricated with two differentN_Aboth achieve 8000 V breakdown voltage and 4.7 MV cm⁻¹average electric field. This field is over three times higher than the best report in prior multi‐kilovolt lateral devices. These results show the promise of p‐type NiO for pushing the performance limits of power devices.