Ohmic Behavior in Metal Contacts to n/p-Type Transition-Metal Dichalcogenides: Schottky versus Tunneling Barrier Trade-off

High contact resistance (RC) between 3D metallic conductors and single-layer 2D semiconductors poses major challenges toward their integration in nanoscale electronic devices. While experiments the large RC values can be partly due to defects, ab initio simulations suggest that, even defect-free structures, interaction metal semiconductor orbitals induce gap states that pin Fermi level band gap, increase Schottky barrier height (SBH), thus degrade resistance. In this paper, we investigate, by using an in-house-developed transport methodology combines density functional theory nonequilibrium Green’s function (NEGF) calculations, physical properties electrical of several options for n-type top contacts monolayer MoS2, presence buffer layers, p-type WSe2. The delicate interplay SBH tunneling thickness is quantitatively analyzed, confirming excellent Bi–MoS2 system as ohmic contact. Moreover, simulation results supported literature Au–WSe2 a promising candidate contacts. Finally, our analysis also reveals small modulation few angstroms distance (semi)metal transition-metal dichalcogenide (TMD) leads variations RC. This could help explain scattering experimentally reported because different deposition techniques result changes metal-to-TMD besides affecting possible defects.