Electronic and Optical Properties of Two-Dimensional MoSi₂P₄/BAs Heterostructures

Vertical stacking of two semiconducting monolayers is an effective way to improve the optoelectronic performance of individual monolayers. Employing first-principles calculations, MoSi2P4/BAs heterobilayers with six stacking configurations (AA1 ∼ AA6) are investigated. In particular, the electronic and optical properties of the AA2 stacking configuration are explored in depth due to the relatively high stabilities. The AA2 configuration is predicted to be a direct semiconductor with a moderate gap at the G0W0 level. It also exhibits strong optical absorption for near-infrared and visible lights, which is significantly better than that of the isolated MoSi2P4 monolayer. Based on G0W0+BSE calculations, the light absorbance coefficients of the AA2 configuration can be larger than 107 cm–1 in the near-infrared-visible light range. More interestingly, a type-II band alignment and an advantageous built-in electric field are formed in the AA2 stacking, which facilitates the effective separation of intralayer photogenerated electron–hole pairs, thus forming an indirect exciton with a relatively large oscillator strength and a long radiative lifetime of several nanoseconds at room temperature. These findings indicate that the MoSi2P4/BAs heterobilayer can be a good candidate for new optoelectronic devices.