Approach for ambipolar behaviour suppression in tunnel FET by workfunction engineering

Abstract

A dual material control gate tunnel field effect transistor (TFET) for asymmetric doping at source and drain regions is proposed. The gate consists of three segment different workfunctions ϕ 1, ϕ 2, and ϕ 3, which are named as tunnelling gate (M 1), control gate (M 2), and auxiliary gate (M 3), respectively. Forward to this, three possible combinations of ϕ 1, ϕ 2 and ϕ 3 to maintain the dual workfunctionality of the device (ϕ 2 = ϕ 3 > ϕ 1, ϕ 1 = ϕ 2 > ϕ 3, ϕ 1 = ϕ 3 < ϕ 2) were considered. Further, the comparison of these possible combinations are performed with conventional TFET (ϕ 1 = ϕ 2 = ϕ 3). Among these ϕ 1 = ϕ 3 < ϕ 2, generates most optimum results in terms of suppression of ambipolar behaviour, and enhancement in ON state current (I ON) of the device. The proposed device shows significant improvement in terms of I ON (1.66 × 10−5 A/μm for SiO 2), I ON/I OFF (7.22 × 1011), and sub-threshold swing (∼19 mV/decade) as compared with conventional and the dual material TFET devices. Further, the analysis of analogue/RF performance is performed for the devices showing optimum performance in terms of suppression of ambipolar behaviour.