Structural, electronic, and optical properties of pristine and bilayers of hexagonal III-V binary compounds and their hydrogenated counterparts

Density functional theory calculations were performed to investigate the structural, electronic, and optical properties of two-dimensional hexagonal III-V binary compounds (h-MX, M = B, Al, Ga, and X = N, P and As), the fully hydrogenated counterparts (MXH2) and the MX/MXH2 van der Waals (vdW) heterostructures. The results show that hydrogenation can change the stability and electronic band dispersion of hexagonal III-V binary compounds, of which the fully hydrogenated h-AlN becomes dynamically unstable. The full hydrogenation induces an indirect-to-direct bandgap transition for hexagonal BN, GaN, GaP, GaAs, and the band gaps become tunable by applying the biaxial strain.These characteristics are conducive to design of strain-based 2D materials for application in nanoelectronic and optoelectronic devices. Furthermore, the different stacking pattern MX/MXH2 vdW heterostructures have been investigated. Of which, BN/BNH2, GaN/GaNH2, GaP/GaPH2 and GaAs/GaAsH2 were found to have the typical type-II band alignments, which can facilitate the effective separation of photogenerated electrons and holes. The calculated band alignment and enhanced optical ab-sorption suggest that the GaP/GaPH2 and GaAs/GaAsH2 vdW heterostructures possess great potential to be high-performance optoelectronic device.