Monolayers of Germanene/Janus Ga2SeTe van der Waals Heterostructures by First-Principles Calculations for High-Performance Optoelectronic Devices

The emerging Janus Ga2SeTe with an asymmetric structure has attracted a great deal of research interest. In this paper, we construct the van der Waals heterostructures (vdWHs) of monolayer Janus Ga2SeTe and germanene (Ge) and named their two stacking modes as Te/Ge vdWH and Se/Ge vdWH. We find that Ge/Ga2SeTe vdWHs in both stacking modes form n-type Schottky contacts. Furthermore, the Schottky barrier height and Schottky contact type in Ge/Ga2SeTe are modulated through interlayer distances and electric fields, which lead to a transition from n-type to p-type Schottky contacts or ohmic contacts. In particular, the weak interaction between the two monolayers leads to the creation of a band gap in the Dirac cone. When a compressive strain in the z direction is applied to the Se/Ge heterostructure, Ge has a larger band gap. The results of our work can provide valuable guidance for the design of controllable Schottky nanodevices and high-performance optoelectronic devices based on Ge/Ga2SeTe vdWHs.