Janus Ga2STe monolayer under strain and electric field: Theoretical prediction of electronic and optical properties

In this work, detailed investigations of the electronic and optical properties of a Janus Ga2STe monolayer under a biaxial strain and electric field have been performed using density functional theory. Via the phonon spectrum and ab-initio molecular dynamics simulations, the dynamical and thermal stabilities of the Janus Ga2STe monolayer are verified. Our obtained results showed that the Janus Ga2STe exhibits a direct semiconducting characteristic and its band gap depends greatly on the biaxial strain. While both the electronic and optical properties are very weakly dependent on the electric field, strain engineering can cause a direct–indirect band gap transitions in the Janus Ga2STe. At equilibrium, the optical absorbance of the Janus Ga2STe monolayer is activated in the infrared light region of about 0.9 eV, which is close to its band gap value. The main peak of the optical absorbance spectrum is located in the ultraviolet light region with an absorbance intensity of 11.914 × 104 cm−1 may be increased by compression strain. In particular, the absorbance intensity of the Janus Ga2STe monolayer increases rapidly in the visible light region, reaching 4.810 × 104 cm−1 and can be altered by strain. Our results not only show that the Janus Ga2STe monolayer has many promising applications in opto-electronic devices but also motivates experimental works on Janus structures in near future. •Janus Ga2STe monolayer is dynamically and thermal stable at room temperature.•Janus Ga2STe is a direct semiconductor and its band gap can be strongly altered by strain.•The direct-indirect gap transitions were found in strained Janus Ga2STe monolayer.•Electronic and optical properties of Ga2STe depend weakly on external electric field.•Ga2STe has wide absorption spectrum, stretching from infrared to ultraviolet light region.