Uncovering the Different Components of Contact Resistance to Atomically Thin Semiconductors

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 (R-c) and an underlying approach to its reduction are currently lacking. Here, the classical R-c 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 (R-jun) is offered. A combination of transfer length method and contact-end measurements to characterize contacts to monolayer MoS2 and separate the different R-c components is used. Technology computer-aided design simulations are also used to study R-c in Fermi-level pinned and unpinned contacts. This study finds that R-jun is the dominating component of R-c 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 R-jun.

Automated summary

Achieving good electrical contacts is a major challenge in devices based on atomically thin 2D semiconductors. This study experimentally examines the classical transmission line model description of contacts to 2D materials and proposes a modification based on an additional lateral resistance component. It finds that the additional lateral resistance component dominates the contact resistance in atomically thin semiconductor devices and is responsible for the back-gate bias and temperature dependence.