Assessment of temperature and ITCs on single gate L-shaped tunnel FET for low power high frequency application

Abstract

In a vertical TFET structure, controllability over the gate is enhanced because of the favorable electrostatic potential and tunneling under the entire gate region by preventing the direct source to drain tunneling. For an L-shaped TFET, the Band-to-Band-Tunneling (BTBT) is perpendicular and parallel to the channel length. Also, it has a higher I on (ON-current) with suppressed ambipolar current (low I ambi ) and is more scalable than other vertical BTBT mechanism-based TFET structures. The reliability of n-type single gate L-shaped TFET (SG-nLTFET) is investigated by examining: (1) impact of temperature (Temp K ) variation (from 260 K to 460 K) and (2) Interface trap charge (ITCs) polarity at fixed charge density on analog /RF /linearity figure of merits (FOMs). The obtained results reveal that change in polarity of ITCs at the Si/HfO 2 interface,modifies the analogue characteristics of the SG-nLTFET significantly in terms of turn-on voltage as well as I on . The temperature sensitivity of SG-nLTFET device indicates that the ShockleyReadHall (SRH) and Trap-Assisted-Tunneling (TAT) phenomenon dominates at lower gate bias and degrades the I on /I off ratio at high temperatures. On the other hand, the BTBT mechanism predominates in the subthreshold regime of transfer characteristics. Furthermore, the results reveal that the off-state current (I off ) degrades dramatically at high temperatures. According to the empirical analysis, SG-nLTFET is insusceptible to Positive-ITCs (Donor trap charges, P-ITCs) present at Si/HfO 2 interface in comparison to Negative-ITCs (Acceptor trap charges, N-ITCs).