Tunable type-II band alignment and electronic structure of C3N4/MoSi2N4 heterostructure: Interlayer coupling and electric field

In this work, we perform a first-principle study to investigate the atomic and electronic structures of the ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ van der Waals heterostructure (vdWH) as well as its tunable electronic structure via interlayer coupling and an external perpendicular electric field. The ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ vdWH is structurally and thermodynamically stable at room temperature. Our results demonstrate that the ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ vdWH exhibits a semiconducting characteristic with a direct band gap of 1.86/2.66 eV as given by the PBE/HSE06 calculation. This value of band gap conveniently lies in the visible light energy range, thus unraveling the strong optical absorption of ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ vdWH in the technologically important visible light regime. The band edges of the ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ vdWH separately from the ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ and ${\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ layers, thus resulting in a type-II band alignment, which is highly desirable for achieving efficient electron-hole separation. Remarkably, the electronic structure and the band alignment types can be flexibly tuned between type-I and type-II by applying an external electric field, by changing the interlayer distance and by applying the in-plane strain. Our findings reveal the potential of ${\mathrm{C}}_{3}{\mathrm{N}}_{4}/{\mathrm{MoSi}}_{2}{\mathrm{N}}_{4}$ vdWH as a tunable hybrid material with strong potential in optoelectronic applications.