Contact Scaling for 2D FETs Using Asymmetrical Contact Measurements

Atomically thin two-dimensional (2D) crystals are promising channel materials for extremely scaled field-effect transistors (FETs) for the 2030 era [1]. In the quest of ultra-scaled transistors, both channel length (distance from source to drain contacts) and contact length (distance that the contacts overlap the 2D channel) must be scaled. However, contacting 2D materials at scaled contact lengths (L_c < 30 nm) has rarely been pursued or studied in-depth. In this work, we experimentally scaled contact length for Ni-contacted MoS₂ FETs and use asymmetrical contact measurements (ACM) as a new approach for characterizing the devices. We found that, contrary to most previous reports, top contacts can be scaled down to ~30 nm without noticeable degradation in contact resistance. Surprisingly, we also observed significant self-heating in scaled contacts in the saturation regime. While the first observation is promising for extremely scaled FET technologies, the second illustrates that current crowding in metal-2D contacts is a challenge toward the development for future scaled devices.
[1] IEEE International Roadmap for Devices and Systems. https://irds.ieee.org/ (2020).