Device physics and design of symmetrically doped tunnel field-effect transistors

Abstract

Symmetric tunnel field-effect transistors (TFETs) have recently been proposed in order to make the design and fabrication of TFET-based circuits favorable. In this paper, we adequately investigate the device physics and design of point-tunneling TFETs with symmetric doping profiles. Based on two-dimensional numerical simulations, it is shown in the proposed symmetric TFETs that the on-current is doubled due to an additional source and the ambipolar off-leakage is significantly diminished because the drain tunnel junction is designed far from the gate. Moreover, those advantages in on- and ambipolar off-currents are not only performed in high-bandgap but also remained in low-bandgap materials. Examining the roles of structure parameters indicates that designing the drain junction width, the gate, drain-to-gate or horizontal drain-to-source lengths smaller than their lower limits, namely in this investigation, 20, 80, 70 and 20 nm, respectively, can severely deteriorate the on- and/or off-currents of the normal symmetric TFETs. Based on the design guidelines provided, an advanced Y-shaped structure is proposed to simultaneously optimize both the electrical characteristics and the scalability of symmetrically doped TFETs.