Sub-10-nm Scalability of Emerging Nanowire Junctionless FETs Using a Schottky Metallic Core

Inefficient volume depletion is a dominant leakage mechanism in junctionless (JL) field-effect transistors (FET). Moreover, the realization of efficient volume depletion is compensated by the detrimental leakage mechanism of the lateral band-to-band tunneling (L-BTBT), which drastically degrades the performance of nanowire (NW) JLFETs with short gate lengths. A Schottky metallic core (SC) nanowire (NW) junctionless (JL) FET is therefore proposed herein to realize efficient volume depletion along with a significant reduction of the L-BTBT-induced parasitic leakage. Using calibrated three-dimensional (3-D) simulations, it is demonstrated that the presence of a Schottky metallic core effectively depletes the surrounding NW shell by abolishing the shielding effect of holes, which helps in realizing the efficient volume depletion that is desirable in OFF-state. Furthermore, it also leads to a significant reduction of the L-BTBT-induced parasitic bipolar junction transistor (BJT) action. This simultaneous suppression of both leakage mechanisms reduces the OFF-state current by around eight orders of magnitude, leading to a significant ON-state to OFF-state current (I_ON/I_OFF) ratio of ~ 10⁹ for a gate length of 20 nm. The reduced parasitic BJT action facilitates the scaling of SC NW JLFET, leading to a remarkable I_ON/I_OFF ratio of ~ 10⁷ even at a scaled gate length of 7 nm. The Schottky junction results in a vertical electric field that hinders the lateral electrostatic coupling of the drain field lines with the channel, leading to reduced detrimental short-channel effects in the sub-10-nm regime. This immunity against short-channel effects is further boosted by using high-k spacers. Thus, the excellent OFF-state behavior along with the reduced short-channel effects provides an incentive for realizing the proposed SC NW JLFET at sub-10-nm technology nodes.