Unique band trends in intrinsic direct-gap AlGeX (X = S, Se, Te) monolayers

Abstract

In this work, the structure, stability, and electronic properties of novel AlGeX (X = S, Se, Te) monolayers are investigated using first-principles calculations. Our calculations show that all AlGeX are stable and transition-allowed direct-gap semiconductors, with band gaps of AlGeS, AlGeSe, and AlGeTe calculated to be 0.838, 1.277, and 1.421 eV at the HSE06 + SOC level, respectively. The phenomenon that gaps of AlGeX compounds increase abnormally as chalcogen (X) becomes heavier is further analyzed by projected band structures and crystal orbital Hamilton population (COHP). This study suggests that AlGeX monolayers might be promising materials for future electronic and optoelectronic devices.