Electronic transport properties of phosphorene/graphene(silicene/germanene) bilayer heterostructures: A first-principles exploration

Recently, new researches on van der Waals (vdW) two-dimensional bilayer heterostructures have been carried out owing to their unique properties different from single-layer materials. Herein, three types of bilayer heterostructures, phosphorene/graphene, phosphorene/silicene and phosphorene/germanene are constructed and their electronic transport properties are calculated based on the first-principle method. The results show that their I-V curves are totally different that the phosphorene/graphene devices have higher electron transmission probability, resulting in higher current values. Furthermore, we calculate their band structures to explore the internal mechanism of current difference. The graphene-like Dirac cones are found in the bilayer phosphorene/graphene heterostructures. However, the positions of their Dirac cones in the Brillouin zone are markedly different from that of graphene. But when the silicene or germanene is combined with the phosphorene together, the Dirac cones of the silicene or germanene disappear, instead, there are band gaps of about 0.2 eV around the Fermi level. Our results suggest that the Dirac cone can be mainly retained by the weak hybridization between monolayer phosphorus and 2D Dirac materials. Due to the existence of the Dirac cone, the overlap between the source and drain electrodes increases, which leads to a larger current value. This discovery of the Dirac cones in the bilayer heterostructures is applicable in designing Dirac materials and understanding their electronic transport properties.