The structural, electronic and optic properties in a series of M2XY (M = Ga, In; X,Y = S, Se, Te) Janus monolayer materials based on GW and the Bethe-Salpeter equation

Utilizing first-principles calculations, we have investigated the structural, electronic, and optic properties of a series of two-dimensional (2D) stable direct band-gap semiconductors, which are M 2 XY (M = Ga, In; X,Y = S, Se, Te) in group-III-V with the Janus single layer structures. Meanwhile, the MX (M = Ga, In; X = S, Se, Te) of binary single layer structures, which are parent materials for Janus structures, have also been investigated. The electronic structures are calculated via GW 0 self-consistency, and the results show that these Janus monolayer structures belong to the direct band-gap semiconductors with large band gap. In contrast to the indirect band-gap MX monolayers, it indicates that an indirect-direct band-gap transition can be realized by constructing Janus structures. Moreover, we systematically investigated the optic response properties of M 2 XY Janus single layers by solving the Bethe-Salpeter equation (BSE), and the exciton absorption peaks are observed in these monolayer structures. Our results show that these Janus structure materials should be potential candidates for optoelectronic nanodevices. Graphical abstract