Electronic properties of MoS(2)/MoO(x) interfaces: Implications in Tunnel Field Effect Transistors and Hole Contacts

In an electronic device based on two dimensional (2D) transitional metal dichalcogenides (TMDs), finding a low resistance metal contact is critical in order to achieve the desired performance. However, due to the unusual Fermi level pinning in metal/2D TMD interface, the performance is limited. Here, we investigate the electronic properties of TMDs and transition metal oxide (TMO) interfaces (MoS(2)/MoO(3)) using density functional theory (DFT). Our results demonstrate that, due to the large work function of MoO(3) and the relative band alignment with MoS(2), together with small energy gap, the MoS(2)/MoO(3) interface is a good candidate for a tunnel field effect (TFET)-type device. Moreover, if the interface is not stoichiometric because of the presence of oxygen vacancies in MoO(3), the heterostructure is more suitable for p-type (hole) contacts, exhibiting an Ohmic electrical behavior as experimentally demonstrated for different TMO/TMD interfaces. Our results reveal that the defect state induced by an oxygen vacancy in the MoO(3) aligns with the valance band of MoS(2), showing an insignificant impact on the band gap of the TMD. This result highlights the role of oxygen vacancies in oxides on facilitating appropriate contacts at the MoS(2) and MoO(x) (x < 3) interface, which consistently explains the available experimental observations.