High-performance multilayer WSe2 p-type field effect transistors with Pd contacts for circuit applications

WSe 2 is thought to be one of the best emerging p-type transition metal dichalcogenide (TMD) materials for potential low-power complementary metal oxide semiconductor (CMOS) circuit applications. However, the contact barrier and the interface quality hinder the performance of p-type field effect transistors (FETs) with WSe 2 films. In this work, metals with different work functions—Pd, Pt, and Ag—were systematically investigated as contacts for WSe 2 to decrease the contact resistances at source/drain electrodes and potentially improve transistor performance. Optimized p-type multilayer WSe 2 FETs with Pd contacts were successfully fabricated, and excellent electrical characteristics were obtained: a hole mobility of 36 cm 2 V −1 s −1 ; a high on/off ratio, over 10 6 ; and a record low sub-threshold swing, SS = 95 mV/dec, which may be attributed to the small Schottky barrier height of 295 meV between Pd and WSe 2 , and strong Fermi-level pinning near the top of the valence band at the interface. Finally, a full-functional CMOS inverter was also demonstrated, consisting of a p-type WSe 2 FET together with a normal n-type MoS 2 FET. This confirmed the potential of TMD FETs in future low-power CMOS digital circuit applications.