Threshold voltage modulation of AlGaN/GaN MIS-FinFETs with sub-60 mV/decade subthreshold swing

In this work, threshold voltage modulation realized by adjusting fin width and dielectric layer were investigated through MIS-FinFETs. As fin width decreases from 120 to 30 nm, threshold voltage shifts toward positive direction and finally becomes positive value while maintaining SS smaller than 60 mV/dec. The phenomenon of achieving sub-60 mV/dec characteristics were illustrated by simulation and the concept of effective channel length. As for dielectric layer, by 20 nm-thick SiO
₂
dielectric layer, device with fin width of 90 nm exhibits a threshold voltage of -0.5 V with SS as small as 50 mV/dec. Even when fin width is 30 nm, drain leakage is still not small enough when VG = 0, which indicates that the gate is not able to totally deplete the fin structure. In order to further increase threshold voltage and enhance the gate controllability, by 10 nm-thick Al
₂
O
₃
dielectric layer, a threshold voltage of 2 V is achieved when fin width is 40 nm with SS as small as 52 mV/dec due to the higher dielectric constant and thinner thickness of Al
₂
O
₃
compared with SiO
₂
. Therefore, by the modulation of fin width, dielectric layer type, and dielectric thickness, threshold voltage can be carefully designed according to the application requirements while maintaining SS below 60 mV/dec.