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. 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. 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, 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.