Distinct contact scaling effects in MoS 2 Transistors revealed with asymmetrical contact measurements.

Two-dimensional (2D) semiconducting materials have great potential for use in future electronics due to their atomically thin nature enabling better scalability. The channel scalability of 2D materials has been thoroughly investigated, confirming their resilience to short-channel effects. However, the current understanding of contact scaling in 2D devices is inconsistent and oversimplified. Here we combine physically scaled contacts and asymmetrical contact measurements (ACMs) to investigate the contact scaling behavior in 2D field-effect transistors (FETs). The ACMs directly compare electron injection at different contact lengths while using the exact same MoS 2  channel, eliminating channel-to-channel variations. Compared to devices with long contact lengths, devices with short contact lengths (scaled contacts) exhibit larger variations, 15% lower drain currents at high drain-source voltages, and a higher chance of early saturation and negative differential resistance. Quantum transport simulations show that the transfer length of Ni-MoS 2  contacts can be as short as 5 nm. Importantly, our results suggest that scaled source contacts can limit the drain current, whereas scaled drain contacts do not. Furthermore, we clearly identify that the actual transfer length depends on the quality of the metal-2D interface. The asymmetrical contact measurements demonstrated here will enable further understanding of contact scaling behavior at various interfaces. This article is protected by copyright. All rights reserved.