Monolayer Bi₂Se_3-xTe_x: novel two-dimensional semiconductors with excellent stability and high electron mobility

Two-dimensional materials play a vital role in next-generation microelectronics, optoelectronics and flexible electronics due to their novel physical properties caused by quantum-confinement effects. In this work, we investigate the stability and the possibility of exfoliation of monolayer Bi₂Se_3-xTe_x (x = 0, 1, 2) using first-principles calculations. Our calculations show that these materials are indirect bandgap semiconductors, and the elastic modulus is smaller than other conventional materials, which indicates better flexibility. We find that the electron mobility of monolayer Bi₂SeTe₂ along the armchair direction is higher than that of black phosphorene, reaching 2708 cm² V^-1 s^-1, and the electron mobility of monolayer Bi₂Se₃ along the zigzag direction is about 24 times larger than the hole mobility. The remarkable electron mobilities and highly anisotropic properties of these new monolayers pave the way for future applications in high-speed (opto)electronic devices.