Exploiting Within-Channel Tunneling in a Nanoscale Tunnel Field-Effect Transistor

In this paper, using device simulations, we investigate electrical characteristics of a tunnel field-effect transistor (TFET) in which band-to-band tunneling (BTBT) occurs dominantly within the channel, rather than at source-channel junction. The within-channel BTBT is enabled by sharp band-bending induced by the dual material gate (DMG). The work-functions of two metal gates are chosen, such that the surface potential profile exhibits a distinct step at the DMG interface. Consequently, even under equilibrium condition, a high lateral electric field and an abrupt tunneling junction exist at the DMG interface. When a small gate voltage is applied, the inherent lateral electric field aids in creating an abrupt band alignment and obtaining a small tunneling width. As a result, an excellent average subthreshold swing is obtained in the proposed device. We have also investigated scaling of channel lengths in the proposed device and have demonstrated that within-channel tunneling can be exploited for channel lengths of 40nm and above. Furthermore, low drain threshold voltage and suppressed drain-induced barrier lowering can be obtained in the proposed device. Moreover, in contrast to conventional TFETs, electrical characteristics of the proposed device are less susceptible to source doping variations and shift in gate-edge with respect to the source-channel junction.