Regular Article

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

¹ Department of Physics, Yantai University, Yantai 264005, P.R. China
² Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P.R. China

^a e-mail: zhdai@ytu.edu.cn

Received: 21 August 2019
Received in final form: 28 April 2020
Published online: 13 July 2020

Abstract

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 M₂XY (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 GW₀ 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 M₂XY 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.