Monolayer γ-MTe (M = Ga, In): Indirect semiconductors with robust stability and low exciton binding energy

We propose monolayer γ-MTe (M = Ga, In) and conduct comprehensive investigations of their crystal structure, electronic properties, carrier mobility, optical properties using first-principles calculations. The thermal, dynamic, mechanical stabilities of the monolayer γ-MTe is rigorously validated through abinitio molecular dynamics simulation, phonon dispersion analysis, elastic constants calculation, demonstrating robustness under various physical conditions. With band gaps of 0.97 eV and 1.16 eV, respectively, γ-MTe is an indirect semiconductor that maintains its semiconducting nature over a wide strain range of -5% ≤δ≤ 5%, highlighting its mechanical resilience. The reduction in band gap under strain is primarily attributed to weakened M-M bond interactions, leading to diminished orbital overlap and hybridization. The predicted optical properties, derived from the many-body G0W0 plus Bethe–Salpeter equation method, show case high absorption coefficients throughout the ultraviolet–visible spectrum, accompanied by remarkably with low exciton energies of 0.15 eV for γ-GaTe, 0.34 eV for γ-InTe. •Monolayer γ-MTe has strong stability, as confirmed by various evaluations.•Monolayer γ-MTe maintains its semiconducting nature under strains of -5% ⩽δ⩽ 5%.•Monolayer γ-MTe exhibits strong optical absorption and low exciton binding energies, highlighting its potential for advanced optical applications.