Engineering the electronic and optoelectronic properties of InX (X = S, Se, Te) monolayers via strain

In this paper, we present a comprehensive study on the electronic and optoelectronic properties of indium monochalcogenide (InX with X = S, Se, Te) monolayers with and without strains. Our results show that InX monolayers are indirect semiconductors. Upon the application of strain, the band structures can be modulated and an indirect-to-direct bandgap transition is observed in an InSe monolayer. The electron mobility of up to 2.0 × 10³ cm² (V s)^-1 is quantitatively determined in the framework of deformation potential theory. Though the mobility of holes is relatively small, it can be greatly improved by introducing compressive strain, with a value up to 2.8 × 10³ cm² (V s)^-1. In addition, the performance of the photoresponse of InX monolayers is evaluated based on first-principles calculations. Under illumination, the InX based systems exhibit high photoresponsivity (R_ph = 0.18 A W^-1) and external quantum efficiency (EQE = 62.5%), which can be further enhanced via strain. Owing to such excellent electronic and optoelectronic merits, InX monolayers will become promising candidates for next-generation ultrathin and flexible electronic and optoelectronic devices.