Characterization and Closed-Form Modeling of Edge/Top/Hybrid Metal-2D Semiconductor Contacts

The paper presents the first comprehensive analysis of the electrical contact topologies to two-dimensional (2D) transition metal dichalcogenide (TMD) semiconducting materials by employing ab-initio density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalisms. Using Landauer's equations, comprehensive numerical models for contact resistance (Rc) of these contact configurations have been derived and subsequently extended to develop the first closed-form expressions for contact resistance to 2D materials (2DM) in these configurations. The comprehensive modeling framework, which includes boundary and interface scatterings, Fermi level pinning (FLP) through metal induced gap states (MIGS), terminated edge states, and surface reconstructions due to interface bonding, the effect of FLP quenching through the presence of a van der Waals (vdW) gap, and the physics of carrier transport across such an interface, is intended for designing 2D FETs with minimal Rc and extracting from experiments the accurate Schottky barrier (SB) height to model realistic 2D-FET device/circuit performance. Hybrid contacts with sufficient (similar to 2 nm) metal-2DM overlap are found to be optimal, and carrier (doping) concentrations and SB height needed for satisfying IRDS requirements have been identified.