Uncovering the Different Components of Contact Resistance to Atomically Thin Semiconductors

Abstract

Achieving good electrical contacts is one of the major challenges in realizing devices based on atomically thin 2D semiconductors. Several studies have examined this hurdle, but a universal understanding of the contact resistance (Rc) and an underlying approach to its reduction are currently lacking. Here, the classical Rc transmission line model description of contacts to 2D materials is experimentally examined, and a modification based on an additional lateral resistance component, namely, the junction resistance (Rjun) is offered. A combination of transfer length method and contact-end measurements to characterize contacts to monolayer MoS2 and separate the different Rc components is used. Technology computer-aided design simulations are also used to study Rc in Fermi-level pinned and unpinned contacts. This study finds that Rjun is the dominating component of Rc in atomically thin semiconductor devices, and is also responsible for most of the back-gate bias and temperature dependence. The experimental results help understand the underlying physics of state-of-the-art contact engineering in the context of minimizing Rjun.