Design and simulation of enhancement-mode N-polar GaN single-channel and dual-channel MIS-HEMTs

GaN HEMTs have demonstrated higher power density and efficiency over existing technologies such as silicon and gallium arsenide (GaAs) based RF and microwave transistors [1]. Until recently, improvements in the design of GaN semiconductor device had focused on Ga-polar GaN based HEMTs. Lately, N-polar GaN shows the advantage over Ga-polar device in making enhancement-mode (E-mode) device with low access resistance, and in particular, for low voltage operation. An E-mode N-polar GaN MISFET device was demonstrated to achieve a threshold voltage of 1 V and a record-high drive current 0.74 A/mm at a gate length of 0.62 μm [2]. Unfortunately, there are few analytical and simulation models developed for E-mode N-polar GaN HEMT. Moreover, the drive current under low voltage bias for N-polar GaN HEMT is smaller than the state-of-the-art Ga-polar GaN HEMT. In this work, by 2-D simulations in Synopsys TCAD [3], we, for the first time, (1) investigated N-polar E-mode single channel GaN MIS-HEMT through simulations; (2) designed an E-mode N-polar GaN dual channel MIS-HEMT and identified the mechanism of the drive current enhancement.