Dipole-regulated bandgap and high electron mobility for bilayer Janus MoSiGeN4

Two-dimensional (2D) Janus materials have attracted the interest of scholars due to their asymmetric structure and unique physical properties. Recently, the 2D Janus MoSiGeN4 based on MoSi2N4 has been predicted. Here, the structure, electronic character, and carrier mobility of a bilayer in different stacks are investigated using the first-principles calculations. The results show that the dipole moment perpendicular to the x-y plane plays a dominant role in regulating the bandgap, which can be supported by the difference in vacuum energy levels between the two sides of the material. The layer stack has a dramatic effect on the bandgap, which is reduced to 0.57 eV for a bilayer structure. Further exploration of the electronic structure reveals that the bilayer energy band exhibits the type II energy band alignment, which is beneficial for the separation of photogenerated carriers. The bilayer boosts electron mobility by an order of magnitude to 58 522.3 cm2 V−1 s−1 for the monolayer. The results demonstrate the potential of the bilayer MoSiGeN4 for photocatalytic water splitting and electronic devices.