Electronic properties of a two-dimensional van der Waals MoGe2N4/MoSi2N4 heterobilayer: effect of the insertion of a graphene layer and interlayer coupling

van der Waals heterostructures (vdWHs) based on 2D layered materials with select properties are paving the way to integration at the atomic scale, and may give rise to new heterostructures exhibiting absolutely novel physics and versatility. Herein, we investigate the structural and contact types in a 2D vdW heterobilayer between MoGe2N4 and MoSi2N4 monolayers, and the monolayers in the presence of electrical graphene (GR) contact. In the ground state, the MoGe2N4/MoSi2N4 heterobilayer forms type-II band alignment, which effectively promotes the separation of electrons and holes and provides opportunity for further electrons and holes. Thus, the MoGe2N4/MoSi2N4 heterobilayer is promising for designing optoelectronic devices with significantly suppressed carrier-recombination. Interestingly, the insertion of the GR contact to a MoGe2N4/MoSi2N4 heterobilayer gives rise to the formation of a metal/semiconductor contact. Depending on the GR position relative to the MoGe2N4/MoSi2N4 heterobilayer, the GR-based heterostructure can form either an n-type or p-type Schottky contact. Intriguingly, the contact barriers in the GR contacted MoGe2N4/MoSi2N4 heterobilayer are significantly smaller than those in the GR contacted with MoGe2N4 or MoSi2N4 monolayers, suggesting that the GR/MoGe2N4/MoSi2N4 heterostructure offers an effective pathway to reduce the Schottky barrier, which is highly beneficial for improving the charge injection efficiency of the contact heterostructures. More interestingly, by controlling the interlayer coupling through stacking, both the Schottky barriers and contact types in the GR/MoGe2N4/MoSi2N4 heterostructure can be manipulated. Our findings could provide theoretical insight into the design of nanodevices based on a GR and MoGe2N4/MoSi2N4 heterobilayer.

Automated summary

Van der Waals heterostructures based on 2D layered materials show promise in designing optoelectronic devices and improving charge injection efficiency, especially when incorporating graphene contacts, which can alter contact types and reduce Schottky barriers.