Fermi-Level Pinning-Free WSe₂ Transistors via 2D Van der Waals Metal Contacts and Their Circuits

Precise control over the polarity of transistors is a key necessity for the construction of complementary metal–oxide–semiconductor circuits. However, the polarity control of 2D transistors remains a challenge because of the lack of a high-work-function electrode that completely eliminates Fermi-level pinning at metal–semiconductor interfaces. Here, a creation of clean van der Waals contacts is demonstrated, wherein a metallic 2D material, chlorine-doped SnSe₂ (Cl–SnSe₂), is used as the high-work-function contact, providing an interface that is free of defects and Fermi-level pinning. Such clean contacts made from Cl–SnSe₂ can pose nearly ideal Schottky barrier heights, following the Schottky–Mott limit and thus permitting polarity-controllable transistors. With the integration of Cl–SnSe₂ as contacts, WSe₂ transistors exhibit pronounced p-type characteristics, which are distinctly different from those of the devices with evaporated metal contacts, where n-type transport is observed. Finally, this ability to control the polarity enables the fabrication of functional logic gates and circuits, including inverter, NAND, and NOR.