Spin-orbit coupling effect on electronic, optical, and thermoelectric properties of Janus Ga₂SSe

In this paper, we investigate the electronic, optical, and thermoelectric properties of Ga₂SSe monolayer by using density functional theory. Via analysis of the phonon spectrum and ab initio molecular dynamics simulations, Ga₂SSe is confirmed to be stable at room temperature. Our calculations demonstrate that Ga₂SSe exhibits indirect semiconductor characteristics and the spin-orbit coupling (SOC) effect has slightly reduced its band gap. Besides, the band gap of Ga₂SSe depends tightly on the biaxial strain. When the SOC effect is included, small spin-orbit splitting energy of 90 meV has been found in the valence band. However, the spin-orbit splitting energy dramatically changes in the presence of biaxial strain. Ga₂SSe exhibits high optical absorption intensity in the near-ultraviolet region, up to 8.444 × 10⁴ cm^-1, which is needed for applications in optoelectronic devices. By using the Boltzmann transport equations, the electronic transport coefficients of Ga₂SSe are comprehensively investigated. Our calculations reveal that Ga₂SSe exhibits a very low lattice thermal conductivity and high figure of merit ZT and we can enhance its ZT by temperature. Our findings provide further insight into the physical properties of Ga₂SSe as well as point to prospects for its application in next-generation high-performance devices.