Exploring <i>p</i>‑Type Contact for\nMonolayer WS<sub>2</sub> FETs Using Halogen Doping and Intermediate\nLayers

This work presents a density functional theory (DFT)\nstudy of substitutional\nand adsorption-based halogen (I or F) doping of WS<sub>2</sub>-based\ntransistors to enhance their contact properties. Substitutional doping\nof the WS<sub>2</sub> monolayer with halogens results in <i>n</i>-type behavior, while halogen adsorption on the surface of the WS<sub>2</sub> monolayer induces <i>p</i>-type behavior. This\nis attributed to differing directions of charge flow, as supported\nby the Mulliken analysis. However, due to Fermi-level pinning (FLP)\nat the WS<sub>2</sub>-metal interface, the <i>p</i>-type\nbehavior resulting from halogen adsorption is not very prominent.\nTo achieve better <i>p</i>-type contact, intermediate layers\nof graphene and h-BN are used to mitigate the FLP effect, showing\nsignificant improvement. The F-adsorbed WS<sub>2</sub>-graphene-Pt\ninterface demonstrates excellent <i>p</i>-type contact with\na substantial reduction in the hole Schottky barrier height, making\nit ideal for efficient WS<sub>2</sub>-based <i>p</i>-type\nMOS transistors in CMOS technology.