Interplay of Doping, Defects, and Metal Coupling in P-Type Ohmic Contacts to MoS 2

Achieving p-type Ohmic contacts in MoS2 field-effect transistors (FETs) remains difficult due to Schottky barriers created by strong Fermi-level pinning at metal-semiconductor interfaces. In this work, we investigate how p-type doping, sulfur vacancy defects, and metal-MoS2coupling jointly determine the contact barrier in monolayer and multilayer MoS2. A combined approach using first-principles calculations and device-level simulations is employed to capture contact physics. Experimental measurements of FET devices reveal a systematic thickness-dependent transition from p-type to ambipolar and n-type behavior, which cannot be fully explained by Schottky's model alone. Atomistic modeling shows that ionized dopants generate an interfacial dipole that lowers the hole injection barrier, while sulfur vacancies introduce donor-like gap states that compensate this dipole and strengthen Fermi-level pinning. In parallel, the metal-MoS2interaction varies strongly with the van der Waals gap. Reduced interface distances, which are likely during metal deposition, enhance charge hybridization and suppress the doping-induced potential shift. This combined analysis establishes a unified picture in which the balance among dopants, defects, and metal coupling governs the attainable p-type Ohmic behavior. The results provide guidelines for engineering barrier-free Ohmic contacts in doped MoS2FETS.