High On/Off Current Ratio and Ultrashort Channel <i>p</i>-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 (WOx) interfacial layer and niobium diselenide (NbSe2) contacts. The WOx 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.