Novel Janus group III chalcogenide monolayers Al₂XY₂(X/Y = S, Se, Te): first-principles insight onto the structural,...

Motivated by the recent successful synthesis of 2D quintuple-layer atomic materials, for the first time, we design and investigate the electronic and transport properties of Janus Al₂XY₂(X/Y = S, Se, Te; X ≠ Y) monolayers by using the density functional theory. Our calculations demonstrate that most of the models of Al₂XY₂(except for Al₂STe₂monolayer) are dynamically and mechanically stable. By using the hybrid functional, all models of Al₂XY₂are semiconductors with an indirect bandgap. Meanwhile, Al₂TeS₂monolayer is found to be metal at the Perdew-Burke-Ernzerhof level. Due to the vertical asymmetry structure, an intrinsic built-in electric field exists in the Al₂XY₂and leads to a difference in the vacuum levels between the two sides of the monolayers. Carrier mobilities of Al₂XY₂monolayers are high directional anisotropic due to the anisotropy of their deformation potential constant. Al₂XY₂monolayers exhibit high electron mobility, particularly, the electron mobility of Al₂SeS₂exceeds 1 × 10⁴cm²V^-1 s^-1, suggesting that they are suitable for applications in nanometer-sized electronic devices.