Two-dimensional Janus α-AuXY (X, Y = S/Se/Te) semiconductors with favourable band gaps and high carrier mobilities predicted by first-principles investigations.

In this work, two-dimensional Janus α-AuXY (X, Y = S/Se/Te) monolayers are designed and their structural stabilities and fundamental properties are investigated using first-principle calculations. We find that the three α-AuSSe, α-AuSTe, and α-AuSeTe structures have high energetic, thermodynamic and mechanical stabilities, indicating that experimental fabrication is feasible. In addition, the proposed systems have anisotropic Young's modulus and Poisson's ratio values. According to the electronic structure calculations, the α-AuXY monolayers are indirect semiconductors with appropriate band gaps for sunlight absorption of 1.06 to 1.33 eV at the Perdew-Burke-Ernzerhof level. The calculation results from the Heyd-Scuseria-Ernzerhof method for the α-AuXY monolayers also show indirect band gap semiconductor behavior. Moreover, we utilize the deformation potential technique to analyze the electron and hole mobilities of the α-AuXY materials to determine their transport properties. Interestingly, α-AuSSe shows an impressive hole carrier mobility of 6258.42 cm V s along the -axis. α-AuSTe and α-AuSeTe also have high electron mobilities ( ) of 642.21/584.96 cm V s and 676.56/760.39 cm V s in the / directions, respectively. In view of the remarkable electronic and transport properties, the α-AuXY materials are expected to be promising Janus materials for next-generation optical, electronic, and photovoltaic devices.