Modulation of Contact Resistance of Dual-Gated MoS2 FETs Using Fermi-Level Pinning-Free Antimony Semi-Metal Contacts

Abstract

Achieving low contact resistance (RC) is one of the major challenges in producing 2D FETs for future CMOS technology applications. In this work, the electrical characteristics for semimetal (Sb) and normal metal (Ti) contacted MoS2 devices are systematically analyzed as a function of top and bottom gate-voltages (VTG and VBG). The semimetal contacts not only significantly reduce RC but also induce a strong dependence of RC on VTG, in sharp contrast to Ti contacts that only modulate RC by varying VBG. The anomalous behavior is attributed to the strongly modulated pseudo-junction resistance (Rjun) by VTG, resulting from weak Fermi level pinning (FLP) of Sb contacts. In contrast, the resistances under both metallic contacts remain unchanged by VTG as metal screens the electric field from the applied VTG. Technology computer aided design simulations further confirm the contribution of VTG to Rjun, which improves overall RC of Sb-contacted MoS2 devices. Consequently, the Sb contact has a distinctive merit in dual-gated (DG) device structure, as it greatly reduces RC and enables effective gate control by both VBG and VTG. The results offer new insight into the development of DG 2D FETs with enhanced contact properties realized by using semimetals.