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

Achieving low contact resistance (R-C) 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 (V-TG and V-BG). The semimetal contacts not only significantly reduce R-C but also induce a strong dependence of R-C on V-TG, in sharp contrast to Ti contacts that only modulate R-C by varying V-BG. The anomalous behavior is attributed to the strongly modulated pseudo-junction resistance (R-jun) by V-TG, resulting from weak Fermi level pinning (FLP) of Sb contacts. In contrast, the resistances under both metallic contacts remain unchanged by V-TG as metal screens the electric field from the applied V-TG. Technology computer aided design simulations further confirm the contribution of V-TG to R-jun, which improves overall R-C of Sb-contacted MoS2 devices. Consequently, the Sb contact has a distinctive merit in dual-gated (DG) device structure, as it greatly reduces R-C and enables effective gate control by both V-BG and V-TG. The results offer new insight into the development of DG 2D FETs with enhanced contact properties realized by using semimetals.

Automated summary

Achieving low contact resistance (R-C) is a major challenge in producing 2D FETs. In this work, the electrical characteristics of semimetal and normal metal-contacted MoS2 devices are analyzed. Semimetal contacts significantly reduce R-C and have a strong dependence on top gate-voltage (V-TG), while normal metal contacts only modulate R-C by varying bottom gate-voltage (V-BG). The anomalous behavior is attributed to weak Fermi level pinning (FLP) of semimetal contacts.