Defect-Engineered n-Doping of WSe₂ via Argon Plasma Treatment and Its Application in Field-Effect Transistors

Doping of van der Waals layered semiconductor materials is an essential technique to realize their full potential for implementation in nanoelectronics. Herein, defect-engineered and area-selective n-doping of ambipolar multi-layer WSe₂ are demonstrated via Ar plasma treatment. The contact regions of the WSe₂ are exposed to a mild Ar plasma treatment to induce Se vacancy, while the channel region is protected by a hexagonal boron nitride. The results are systematically analyzed using structural and optical characterization methods, and the origin of the n-type properties in the plasma-treated WSe₂ is proposed using plane-wave density functional theory calculations. The formation of a defect-induced donor level in the source and drain regions of the multi-layer WSe₂ helps to improve the contact behaviors in field-effect transistors (FETs), enhancing the transport of the free electrons. The n-channel current on/off ratio (from 12.8 to 8.3 × 10⁶) and contact resistance (as low as 2.68 kΩ∙mm) of the n-type WSe₂ FETs are greatly improved by the area-specific Ar plasma treatment, enabling the fabrication of a WSe₂-based complementary metal-oxide-semiconductor inverter. This method provides a viable route to control the carrier type and concentration in ambipolar van der Waals layered semiconductors, paving the way for high-performance nanoelectronic devices.