Vertical GaN Superjunction FinFET: A Novel Device Enabling Multi-Kilovolt and Megahertz Power Switching

Suneriunction (SJ) devices could break the theoretical trade-off between breakdown voltage $(V_{\mathrm{B}})$ and on-resistance $(R_{\mathrm{o}\mathrm{n}})$ in conventional power devices, and allow for a much smaller $R_{\mathrm{o}\mathrm{n}}$ for the same $V_{\mathrm{B}}$ [1]. Si SJ MOSFETs have achieved a huge commercial success up to 900 V; over 1 kV SiC SJ MOSFETs were recently announced [2]. GaN SJ devices have superior theoretical performance compared to Si and SiC SJ devices. Recent progress in the fabrication of vertical GaN pn pillars [3] [4] has shown promising prospects for demonstrating GaN SJ devices. Despite these progress in SJ fabrication, the carrier channel design remains an open question for GaN SJ transistors. Conventional inversion-type MOS channel suffers from low mobility and low acceptor activation ratio. Recently, a fin-shaped accumulation-type MOS channel has been demonstrated by using only n-GaN layers, which led to the realization of 1.2 kV vertical GaN power FinFETs with a record switching figure-of-merit (FOM) [5] [6].