Comparing contact resistance of edge-, top-, and hybrid-contacted two-dimensional materials

Abstract

Two-dimensional semiconductors are promising channel materials for continuing transistor scaling and extending Moore’s law. However, as transistor density increases, the area available for contacts shrinks, making low-resistance contacts a critical challenge. Here, we theoretically investigate the performance and scalability of edge, top, and hybrid contacts to Mo⁢S2 monolayers. Using a quantum transport model that includes key mechanisms such as image-force barrier lowering as well as open vertical metal leads, we compare the contact resistance of these geometries while analyzing the impact of parameters such as doping concentration, surrounding dielectrics, metal work functions, van der Waals gap thickness, and contact length. We find that hybrid contacts generally yield the best performance, especially when scaled to contact lengths below 10 nm, achieving a contact resistance close to the quantum limit at doping concentrations above 1013 cm−2. The edge contact exhibits the poorest performance under most circumstances, as it suffers from higher Schottky barriers and lacks mechanisms to reduce them. While the top contact performs well, the hybrid contact shows significantly lower resistances at extreme scaling because it is less sensitive to long transfer lengths.