Effect of SiO${}_2$ surface passivation on the performance of GaN polarization superjunction heterojunction field effect transistors

In this article, the effects of the SiO${}_2$ surface passivation layer are reported on normally-on 1.2 kV GaN polarization superjunction (PSJ) heterojunction field effect transistors (HFETs) by comparing the electrical performances of PSJ HFETs with and without SiO${}_2$ surface passivation. A slight recovery of the 2D electron gas sheet density is observed in the slight negative shift of V${}_{th}$ after SiO${}_2$ surface passivation. Passivation also increases the breakdown voltage. This improvement may result from removing positive surface charges in defects along the P-GaN gate sidewall and top u-GaN layer after the specifically designed SiO${}_2$ surface passivation. Furthermore, the SiO${}_2$ surface passivation can also effectively suppress the surface gate leakage currents in the PSJ HFETs by eliminating the conductive channel created by the positive surface charges in defects. (© 2023 The Authors. physica status solidi (a) applications and materials science published by Wiley‐VCH GmbH)