Selective Electron Beam Patterning of Oxygen-Doped WSe₂ for Seamless Lateral Junction Transistors

Surface charge transfer doping (SCTD) using oxygen plasma to form a p-type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field-effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p-type (p⁺)-doped WSe₂ FETs via electron beam (e-beam) irradiation is reported. The effect of the selective e-beam irradiation is confirmed by the gate-tunable optical responses of seamless lateral p⁺–p diodes. The OFF state of the devices by inducing trapped charges via selective e-beam irradiation onto a desired channel area in p⁺-doped WSe₂, which is in sharp contrast to globally p⁺-doped WSe₂ FETs, is realized. Selective e-beam irradiation of the PMMA-passivated p⁺-WSe₂ enables accurate control of the threshold voltage (V_th) of WSe₂ devices by varying the pattern size and e-beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high-performance WSe₂ p-FETs with a saturation current of −280 µA µm⁻¹ and on/off ratio of 10⁹ are achieved. This study's technique demonstrates a facile approach to obtain high-performance TMD p-FETs by e-beam irradiation, enabling efficient switching and patternability toward various junction devices.