MoS Field-Effect Transistor Performance Enhancement by Contact Doping and Defect Passivation via Fluorine Ions and Its Cyclic Field-Assisted Activation.

MoS-based field-effect transistors (FETs) and, in general, transition metal dichalcogenide channels are fundamentally limited by high contact resistance () and intrinsic defects, which results in low drive current and lower carrier mobilities, respectively. This work addresses these issues using a technique based on CF plasma treatment in the contacts and further cyclic field-assisted drift and activation of the fluorine ions (F), which get introduced into the contact region during the CF plasma treatment. The F ions are activated using cyclic pulses applied across the source-drain (S/D) contacts, which leads to their migration to the contact edges via the channel. Further, using ab initio molecular dynamics and density functional theory simulations, these F ions are found to bond at sulfur (S) vacancies, resulting in their passivation and n-type doping in the channel and near the S/D contacts. An increase in doping results in the narrowing of the Schottky barrier width and a reduction in by ∼90%. Additionally, the passivation of S vacancies in the channel enhances the mobility of the FET by ∼150%. The CF plasma treatment in contacts and further cyclic field-assisted activation of F ions resulted in an ON-current () improvement by ∼90% and ∼480% for exfoliated and CVD-grown MoS, respectively. Moreover, this improvement in has been achieved without any deterioration in the /, which was found to be >7-8 orders.