Wide-Bandgap Nickel Oxide with Tunable Acceptor Concentration for Multidimensional Power Devices

Abstract

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 (NA) 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 tunable NA from < 1018 cm−3 to 2×1018 cm−3 with the practical breakdown field (EB) of 3.8 to 6.3 MV cm−1. This NA range allows for charge balance to n-type region with reasonable process latitude, and EB is high enough to pair with many WBG and UWBG semiconductors. The extracted NA is then used to design a multidimensional Ga2O3 diode with NiO field-modulation structure. The diodes fabricated with two different NA both achieve 8000 V breakdown voltage and 4.7 MV cm−1 average 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.