LAUSR

Abstract To maintain fast development of communication toward terrahertz frequencies, InP-based high electron mobility transistors in InGaAs/InAlAs heterojunctions with ultra-short T-shape gates are constantly demanded. Our earlier work has successfully developed a 10 nm wide T-shape gate anchored by a Si3N4 sheath for high mechanical reliability, nicknamed as the tri-layer T-shape gate. However, the short channel effect, the gating efficiency and the sheath effect on the device performance based on this gate structure are still unclear. This work focuses on the above mentioned issues, trying to establish the connection between the gate structure and the device DC/AC performance through systematic simulation study. The simulation results show that the tri-layer T-shape gate not only enhances the mechanical reliability, but also reduces the lateral electric field around the gate-edges, leading to high break down voltage. Furthermore, such a gate structure exhibits an improved gating efficiency with a positive threshold voltage (Vth) for the gate-width down to 50 nm. The only drawback with the existence of the sheath is that the operation frequency is reduced by 17% comparing to the conventional T shape gate. However, as high as 550 GHz for the current cut-off frequency is still feasible, which is much higher than that with the Si3N4 passivation field plate gate. The foundation built in this work is extremely imperative to the advances of THz technology.