Improved Contacts to MoS2 Transistors by Ultra-High Vacuum Metal Deposition

The scaling of transistors to sub-10 nm dimensions is strongly limited by their contact resistance (R-C). Here we present a systematic study of scaling MoS2 devices and contacts with varying electrode metals and controlled deposition conditions, over a wide range of temperatures (80 to 500 K), carrier densities (1012 to 1013 cm(-2)), and contact dimensions (20 to 500 nm). We uncover that Au deposited in ultra-high vacuum (similar to 10(-9) Torr) yields three times lower Rc than under normal conditions, reaching 740 Omega.mu m and specific contact resistivity 3 X 10(-7) Omega.cm(2), stable for over four months. Modeling reveals separate R-C contributions from the Schottky barrier and the series access resistance, providing key insights on how to further improve scaling of MoS2 contacts and transistor dimensions. The contact transfer length is similar to 35 nm at 300 K, which is verified experimentally using devices with 20 mn contacts and 70 nm contact pitch (CP), equivalent to the "14 nm" technology node.