A sub-thermionic MoS2 FET with tunable transport

Abstract

The inability to scale supply voltage and hence reduce power consumption remains a serious challenge in modern nanotransistors. This arises primarily because the Sub-threshold Swing (SS) of the thermionic MOSFET, a measure of its switching efficiency, is restricted by the Boltzmann limit (kBT/q = 60 mV/dec at 300 K). Tunneling FETs, the most promising candidates to circumvent this limit, employ band-to-band tunneling, yielding very low OFF currents and steep SS but at the expense of severely degraded ON currents. In a completely different approach, by introducing concurrent tuning of thermionic and tunneling components through metal/semiconductor Schottky junctions, we achieve an amalgamation of steep SS and high ON currents in the same device. We demonstrate sub-thermionic transport sustained up to 4 decades with SSmin ∼ 8.3 mV/dec and SSavg ∼ 37.5(25) mV/dec for 4(3) dec in few layer MoS2 dual gated FETs (planar and CMOS compatible) using tunnel injected Schottky contacts for a highly scaled drain voltage of 10 mV, the lowest for any sub-thermionic devices. Furthermore, the same devices can be tuned to operate in the thermionic regime with a field effect mobility of ∼84.3 cm2 V−1 s−1. A detailed mechanism involving the independent control of the Schottky barrier height and width through efficient device architecture and material processing elucidates the functioning of these devices. The Gate Tunable Thermionic Tunnel FET can function at a supply voltage of as low as 0.5 V, reducing power consumption dramatically.