In this paper, we analyze the heterojunction GaAs 0.4 Sb 0.6 /In 0.65 Ga 0.35 As TFET with vertical nanowire structure and non-uniform diameter design (V-NW TFET with non-uniform diameter). A thin channel layer (Ti) is inserted between the gate and source regions for improving the on currents, and the non-uniform diameter thickness is used for suppressing the leakage current (Imin). The bandgap widening induced by quantum confinement is considered in this work. The leakage current can be suppressed by using thinner diameter thickness of the drain/channel junction (Tdc), and the gate-to-drain underlap design is used to further reduce the ambipolar leakage. The impacts of Ti, Tdc, source and drain doping concentrations, and gate-to-source overlap length (Lovs) on the V-NW TFET have been investigated. Compared with the ultra-thin body (UTB) TFET, the proposed V-NW TFET with non-uniform diameter (thin Tdc) exhibits 2 times larger Ion (236 μA/μm) due to the increased line tunneling area, and 59.8 times lower leakage current (5.5 × IO−10 μA/μm).
