High On/Off Current Ratio and Ultrashort Channel p-Type Vertical FET Realized by Plasma Oxidation of WSe₂

Vertical field effect transistors (VFETs) based on two-dimensional materials offer exceptional potential for next-generation electronic devices due to their atomically thin channels and scalability. However, achieving high-performance p-type VFETs (p-VFETs) presents substantial challenges, as these devices often face limitations in hole transport efficiency, leakage current suppression, and attainment of high on/off current ratios. This study introduces an ultrashort channel length (less than 3.5 nm) p-type tungsten diselenide (WSe₂) VFET incorporating a tungsten oxide (WO_x) interfacial layer and niobium diselenide (NbSe₂) contacts. The WO_x layer enhances the p-doping concentration shrinking depletion region and serves as a tunneling barrier enhancing gate controllability, while NbSe₂ forms defect-free van der Waals contacts, minimizing charge trapping and interface scattering. These combined effects result in an on/off current ratio of approximately 10³ and 10⁵ in WSe₂ p-VFET with a 2.1 and 3.5 nm channel length, respectively, demonstrating superior performance compared to previously reported studies. This study establishes a robust platform for the development of high-performance p-type VFETs, paving the way for scalable and energy-efficient electronic devices.