Effect of Facile p-Doping on Electrical and Optoelectronic Characteristics of Ambipolar WSe₂ Field-Effect Transistors

We investigated the electrical and optoelectronic characteristics of ambipolar WSe₂ field-effect transistors (FETs) via facile p-doping process during the thermal annealing in ambient. Through this annealing, the oxygen molecules were successfully doped into the WSe₂ surface, which ensured higher p-type conductivity and the shift of the transfer curve to the positive gate voltage direction. Besides, considerably improved photoswitching response characteristics of ambipolar WSe₂ FETs were achieved by the annealing in ambient. To explore the origin of the changes in electrical and optoelectronic properties, the analyses via X-ray photoelectron, Raman, and photoluminescence spectroscopies were performed. From these analyses, it turned out that WO₃ layers formed by the annealing in ambient introduced p-doping to ambipolar WSe₂ FETs, and disorders originated from the WO₃/WSe₂ interfaces acted as non-radiative recombination sites, leading to significantly improved photoswitching response time characteristics.