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

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 Al2STe2 monolayer) are dynamically and mechanically stable. By using the hybrid functional, all models of Al2XY2 are semiconductors with an indirect bandgap. Meanwhile, Al2TeS2 monolayer 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 Al2XY2 and leads to a difference in the vacuum levels between the two sides of the monolayers. Carrier mobilities of Al2XY2 monolayers are high directional anisotropic due to the anisotropy of their deformation potential constant. Al2XY2 monolayers exhibit high electron mobility, particularly, the electron mobility of Al2SeS2 exceeds 1 × 104 cm2 V−1 s−1, suggesting that they are suitable for applications in nanometer-sized electronic devices.