Workfunction Engineering of A Pocket Tunnel Field-Effect Transistor with A Dual Material Gate

Abstract

A dual-material gate pocket tunnel field-effect transistor (DM-PTFET) with separated source gate and channel gate materials is newly proposed. As the workfunctions of the source and the channel gates in the DM-PTFET were varied, we investigated systematically the optimal workfunction region where the hump effect was removed and the ambipolar current was minimized. Also, we investigated the optimal workfunctions of the dual-material gates in the DM-PTFET for three pocket thickness, T_pocket = 1, 2, and 3 nm. The highest on-current I_on was observed when T_pocket = 1.5 nm, and the off-current I_off decreased as the T_pocket was increased, and the optimal T_pocket is 2 nm in terms of I_on/I_off ratio. The band-to-band tunneling (BTBT), which occurs in the gate-pocket direction in the source, was affected by the source gate, and the BTBT, which occurs in the channel direction in the source, was affected by the channel gate. The hump effect was removed when the work functions of the source gate were 0.05, 0.16, and 0.26 eV less than that of the channel gate when the T_pocket = 1, 2, and 3 nm, respectively. In the optimal structure of the DM-PTFET (with no hump effect, T_pocket = 2 nm, and workfunction of the channel gate < 3.7 eV), I_ambipolar decreased by 10⁴ times compared to its value for a conventional PTFET.