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

Abstract

The scaling of transistors to sub-10 nm dimensions is strongly limited by their contact resistance (RC). 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 (10(12) to 10(13) cm(-2)), and contact dimensions (20 to 500 nm). We uncover that Au deposited in ultra-high vacuum (∼10(-9) Torr) yields three times lower RC than under normal conditions, reaching 740 Ω·μm and specific contact resistivity 3 × 10(-7) Ω·cm(2), stable for over four months. Modeling reveals separate RC 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 ∼35 nm at 300 K, which is verified experimentally using devices with 20 nm contacts and 70 nm contact pitch (CP), equivalent to the "14 nm" technology node.

High Responsivity and Photovoltaic Effect Based on Vertical Transport in Multilayer α‐In2Se3

“…Such current crowding occurs when the physical contact length becomes smaller than the transfer length ( L t ). Generally, for 2D materials (e.g., MoS 2 ), L t < 100 nm and hence the active area is much smaller than L t . In vertical devices, the current crowding mechanism is not dominating because the photogenerated carriers are swept toward the bottom electrode efficiently.…”

Gate-Tunable WSe2/SnSe2 Backward Diode with Ultrahigh-Reverse Rectification Ratio

“…We also demonstrate an efficient modulation of the rectification ratio by tuning the applied gate voltage, contact metals, and thickness of the WSe2 layer. Finally, we show that the effective current transfer length at the heterointerface of these vertical heterojunctions can be very large encompassing the entire overlap area of WSe2 and SnSe2, avoiding current crowding, which is in sharp contrast to typical metal-2D semiconductor contact interfaces, with small transfer length 44,45 .…”

WSe 2 -contact metal interface chemistry and band alignment under high vacuum and ultra high vacuum deposition conditions

“…Whereas MoS 2 has been widely studied as a potential channel material in TMD-based FETs [3][4][5][6][7], studies focused on WSe 2 -based FETs are less prevalent. The electrical behavior of various contact metals on TMDs will vary significantly depending on the TMD, for instance MoS 2 favors n-type conduction while WSe 2 favors p-type conduction [8].…”