Towards High-Performance Monolayer Semiconductor Transistors with Semimetallic Ohmic Contact

Atomically thin two-dimensional (2D) semiconductors have great potential for realizing high-performance electronic devices. However, energy barriers at the metal-semiconductor interface, which fundamentally lead to high contact resistances and poor current-delivery capabilities, have restrained the advancement of 2D semiconductor transistors to date. Here, we report a novel ohmic contact technology between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where the gap-state pinning is sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a record-low contact resistance (R_C) of 123 Ω μm, and a record-high on-state current density (I_ON) of 1135 μA μm^-1 on monolayer MoS₂. We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS₂, WS₂, and WSe₂. Theoretical investigation show that I_ON is now limited by the self-heating effect and can be further optimized. This technology unveils the full potential of high-performance monolayer transistors that are on par with the state-of-the-art 3D semiconductors, enabling further device down-scaling and extending Moore’s Law.