First-principles study of the contact resistance at 2D metal/2D semiconductor heterojunctions

Abstract

The high contact resistance at metal/two-dimensional (2D) semiconductor junctions is a major issue for the integration of 2D materials in nanoelectronic devices. We review here recent theoretical results on the contact resistance at lateral heterojunctions between graphene or 1T-MoS2 with 2H-MoS2 monolayers. The transport properties at these junctions are computed using density functional theory and the non-equilibrium Green's function method. The contact resistance is found to strongly depend on the edge contact symmetry/termination at graphene/2H-MoS2 contacts, varying between about 2 x 102 and 2 x 104 Wμm. This large variation is correlated to the presence or absence of dangling bond defects and/or polar bonds at the interface. On the other hand, the large computed contact resistance at pristine 1T/2H-MoS2 junctions, in the range of 3-4 x 104 Ω•μm, is related to the large electron energy barrier (about 0.8 eV) at the interface. The functionalization of the metallic 1T-MoS2 contact by various adsorbates is predicted to decrease the contact resistance by about two orders of magnitude, being very promising for device applications.