Effects of Oxygen Plasma Treatment on Fermi-Level Pinning and Tunneling at the Metal-Semiconductor Interface of WSe2 FETs

Recently, 2D materials have been intensively investigated for their novel nanoelectronic applications; among these materials, tungsten diselenide (WSe2) is attracting substantial research interest due to its high mobility, sizable bandgap, and ambipolar characteristics. However, Fermi-level pinning (FLP) at the metal-semiconductor contact is a critical issue preventing further integration of WSe2 to complementary metal-oxide-semiconductor (CMOS) technology. In this study, a facile doping method of oxygen (O-2) plasma treatment and an aging effect to overcome the FLP of WSe2 field-effect transistors (FETs) are utilized. After aging, a reduction is observed in FLP on oxidized WSe2 FETs, along with a decrease in pinning factor (S) for holes from -0.06 to -0.36. Further, the field-effect mobility of high- (Pd) and low- (In) work-function contacted WSe2 devices indicates the presence of more improvement in high-work-function metal-contacted p-type WSe2 FETs, which further strengthens the Fermi level de-pinning behavior attributed to the O-2 plasma and aging processes. The existence of different tunneling behaviors of Pd and In devices also confirms the effect of O-2 plasma doping into WSe2 FETs. Ultimately, this work demonstrates a simple and efficient method for achieving the de-pinning of Fermi-levels and modulating FLP of 2D FETs.

Automated summary

Recently, researchers have been studying 2D materials for their unique nanoelectronic applications. Among these materials, tungsten diselenide (WSe2) has attracted significant interest due to its favorable properties. This study proposes a simple method involving oxygen plasma treatment and aging to overcome an issue called Fermi-level pinning (FLP) in WSe2 field-effect transistors (FETs). The results show a reduction in FLP and improved performance in the FETs after aging, along with changes in the metal contacts used. This work demonstrates an efficient approach to addressing FLP and modulating the performance of 2D FETs.