Dual-Metal Graded-Channel Double-Gate Tunnel FETs for Reduction of Ambipolar Conduction

In the presented work, a Tunnel FET device with dual-metal graded-channel structure is proposed and investigated showing the influence of energy band modulation at channel-drain interface on the ambipolar conduction. Through two-dimensional numerical simulations, it is demonstrated that a heavily-doped channel region adjacent to drain terminal along with lower work function gate material modulates the alignment of energy band profile of channel and drain regions at drain-channel interface which, further, increases the tunneling width in Tunnel FETs. Eventually, it leads to a significant reduction in band-to-band generation of charge carriers tunneling at drain-channel interface, thus causing a noticeable suppression in the nature of ambipolarity. The device performances of the presented structure is analysed through TCAD simulations to optimize length and doping concentration of two channel regions. Additionally, it is shown that the presented structure does not deteriorate subthreshold swing and ON-state current of Tunnel FETs.