(Ultra-)Wide-Bandgap Heterogeneous Superjunction: Design, Performance Limit, and Experimental Demonstration

Abstract

Superjunction (SJ) breaks the performance limit of conventional power devices via multidimensional electrostatic engineering. Following a commercial success in Si, it has been recently demonstrated in wide bandgap (WBG) and ultra-WBG (UWBG) semiconductors, including SiC, GaN, and Ga $2$ O $3$. Different from the legacy SJ design based on native p-n junctions, the vertical SJ devices reported in GaN and Ga $2$ O $3$ were built on heterogenous junctions that comprise a foreign p-type material. This hetero-SJ is particularly promising for UWBG materials, in which bipolar doping is difficult. Here, we comprehensively discuss the performance limit, design, and characteristics of the emerging hetero-SJ devices. After a generic performance limit analysis, we use the UWBG Ga $2$ O $3$ /NiO SJ diode as an example to showcase the design guideline, fabrication, and performance of hetero-SJ devices. The emphasis is placed on a self-align process to deposit p-NiO around n-Ga $2$ O $3$ pillars and the impact of the p-NiO thickness inhomogeneity on the device breakdown voltage (BV). Such process and device physics are uniquely relevant to hetero-SJ devices. The fabricated SJ diode achieves a BV over 2 kV and a specific ON-resistance of 0.7 m $Ωċ cm2$ , the tradeoff of which is among the best in kilovolt Schottky barrier diodes (SBDs). These results provide key references for the future development of hetero-SJ devices in diverse material systems.