Negative bias-induced threshold voltage instability and zener/interface trapping mechanism in GaN-based MIS-HEMTs**Project supported by the National Key Research and Development Program of China (Grant No. 2018YFB1802100), the Science Challenge Project, China (Grant No. TZ2018004), and the National Natural Science Foundation of China (Grant Nos. 61534007 and 11690042).

Abstract

We investigate the instability of threshold voltage in D-mode MIS-HEMT with in-situ SiN as gate dielectric under different negative gate stresses. The complex non-monotonic evolution of threshold voltage under the negative stress and during the recovery process is induced by the combination effect of two mechanisms. The effect of trapping behavior of interface state at SiN/AlGaN interface and the effect of zener traps in AlGaN barrier layer on the threshold voltage instability are opposite to each other. The threshold voltage shifts negatively under the negative stress due to the detrapping of the electrons at SiN/AlGaN interface, and shifts positively due to zener trapping in AlGaN barrier layer. As the stress is removed, the threshold voltage shifts positively for the retrapping of interface states and negatively for the thermal detrapping in AlGaN. However, it is the trapping behavior in the AlGaN rather than the interface state that results in the change of transconductance in the D-mode MIS-HEMT.