Reinterpreting Low Resistance in Sb–MoS₂ Ohmic Contacts by Means of Ab Initio Transport Simulations

By using an in-house nonequilibrium Green's function (NEGF)-based ab initio simulator, we investigate the physical mechanisms driving the Sb( <tex-math notation="LaTeX">011̄2</tex-math> )–MoS <tex-math notation="LaTeX">₂</tex-math> system to exhibit the lowest reported contact resistance, <tex-math notation="LaTeX">RC=42~Ω · μ</tex-math> m, to the 2-D semiconductor MoS <tex-math notation="LaTeX">₂</tex-math> . We can find that the transport from the hybridized bands in the Sb–MoS <tex-math notation="LaTeX">₂</tex-math> heterojunction is quite ineffective and that the back-gate-induced doping of MoS <tex-math notation="LaTeX">₂</tex-math> in the contact region is crucial to explain the experiments. In fact, by accounting in our ab initio simulations for the presence of a back gate according to the experiments, it is possible to match the band structure of the MoS <tex-math notation="LaTeX">₂</tex-math> in the Sb–MoS <tex-math notation="LaTeX">₂</tex-math> heterojunction with that of the external MoS <tex-math notation="LaTeX">₂</tex-math> layer, which drastically increases the electronic transmission throughout the contact, and ultimately pushes <tex-math notation="LaTeX">RC</tex-math> close to the quantum limit. Furthermore, we extend the applicability of our previously demonstrated simulation methodology and thus investigate a field-effect transistors (FETs)-like device including an ab initio description of the carrier injection at the Sb–MoS <tex-math notation="LaTeX">₂</tex-math> contact.