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Distinct Contact Scaling Effects in MoS2 Transistors Revealed with Asymmetrical Contact Measurements



Zhihui Cheng, Curt A. Richter, Hattan Abuzaid, Jonathan Backman, Mathieu Luisier, Huairuo Zhang, Albert Davydov, Guoqing Li, Yifei Yu, Linyou Cao, Aaron Franklin


Two-dimensional (2D) materials have great potential for use in future electronics due to their atomic thin nature which withstands short channel effects and thus enables better scalability. Since improved scalability is the core advantage, both the channel and contact scalability must be investigated. The channel scalability of 2D materials has been thoroughly investigated, confirming their resilience to short-channel effects. However, systematic studies on contact scalability remain rare. Here we combine physically scaled contacts and asymmetrical contact measurements to investigate the contact scaling behavior in 2D field-effect transistors (FETs). The asymmetrical contact measurements directly compare electron injection with different contact lengths while using the exact same channel, eliminating channel-to-channel variations. Compared to devices with long contact lengths, devices with short contact lengths (scaled contacts) exhibit larger variation, decreased drain current at high drain-source voltages, and have a higher chance of showing early saturation and negative differential resistance. Also, quantum transport simulations show that the transfer length of Ni-MoS2 contacts can be intrinsically smaller than 5 nm. Our results suggest that the electron injection at the source contact is different from the injection at the drain side: Scaled source contacts can limit the drain current, whereas scaled drain contacts would not. Furthermore, we clearly identified that the transfer length depends on the quality of the metal-2D interface. The asymmetrical contact measurements proposed here will enable further understanding of contact scaling behavior at various interfaces.
Advanced Materials


Contact scaling, transfer length, current crowding, Negative differential resistance, 2D FETs, nanoelectronics


Cheng, Z. , Richter, C. , Abuzaid, H. , Backman, J. , Luisier, M. , Zhang, H. , Davydov, A. , Li, G. , Yu, Y. , Cao, L. and Franklin, A. (2023), Distinct Contact Scaling Effects in MoS2 Transistors Revealed with Asymmetrical Contact Measurements, Advanced Materials, [online],, (Accessed April 13, 2024)
Created February 27, 2023, Updated June 5, 2023