(Ultra-)Wide-Bandgap Heterogeneous Superjunction: Design, Performance Limit, and Experimental Demonstration
Yuan Qin, Yunwei Ma, Ming Xiao, Matthew Porter, Florin Udrea, Han Wang, Yuhao Zhang
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 Ga2O3. Different from the legacy SJ design based on native p-n junctions, the vertical SJ devices reported in GaN and Ga2O3 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 Ga2O3/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-Ga2O3 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<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot \text {cm}^{{2}}$ </tex-math></inline-formula>, 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.