Simulation Study of the Double-Gate Tunnel Field-Effect Transistor with Step Channel Thickness

Double-gate tunnel field-effect transistor (DG TFET) is expected to extend the limitations of leakage current and subthreshold slope. However, it also suffers from the ambipolar behavior with the symmetrical source/drain architecture. To overcome the ambipolar current, asymmetry must be introduced between the source and drain. In this paper, we investigate the performances of DG TFET with step channel thickness (SC TFET) by utilizing the 2D simulation. The asymmetry between source and drain is introduced through the step channel thickness; hence, the ambipolar behavior is expected to be relieved. The results show that the SC TFET exhibits significant reduction of ambipolar current compared with the conventional DG TFET. The mechanisms of SC TFET are thoroughly discussed to explore the physical insight. The impacts introduced by the structure parameters on onset voltage, subthreshold slope, drain current in on-state and ambipolar-state are also exhibited in determining the optimal structure.