Harnessing strain engineering for adaptive optoelectronics in Janus Ga₂SX (X=Se, Te) monolayers

Two-dimensional Janus materials have garnered significant interest in the domain of optoelectronics owing to their asymmetric structures and tunable electronic properties. However, systematic research on Janus systems based on main group elements remains limited. In this study, we systematically investigated the optoelectronic properties of monolayer Janus structures Ga 2 SSe and Ga 2 STe for the first time and the mechanism of biaxial strain in regulating their properties. The findings reveal that Ga 2 SSe is an indirect bandgap semiconductor with a bandgap of 2.534[Formula: see text]eV, while Ga 2 STe exhibits semimetal characteristics. Both materials exhibit excellent thermodynamic and kinetic stability, as evidenced by the absence of imaginary frequencies in their phonon spectra and the stability of their structures in AIMD simulations at 300[Formula: see text]K. The electronic structure can be significantly tuned by applying biaxial strain: The band gap of Ga 2 SSe can be adjusted within a range of 0.63–2.367[Formula: see text]eV under [Formula: see text] strain; the band gap of Ga 2 STe opens to 0.866[Formula: see text]eV under tensile strain, while compressive strain maintains its electrical conductivity. Optical analysis demonstrates that tensile strain enhances the visible light absorption coefficient of Ga 2 SSe by [Formula: see text] [Formula: see text]cm[Formula: see text], while the absorption characteristics of Ga 2 STe exhibit a strain-dependent spectral response. Furthermore, strain-induced charge redistribution and work function modulation elucidate the microscopic mechanism underlying the piezoelectric response of the material. Thermodynamic calculations further demonstrate that Ga 2 STe has a lower Gibbs free energy at high temperatures, thereby demonstrating excellent thermal stability. This study provides a theoretical foundation for the utilization of Ga-based Janus materials in ultraviolet detectors, strain sensors, and spintronic devices. Additionally, it offers novel approaches for band engineering and interface design of two-dimensional materials.