First principles exploration of tunable electronic properties in MoSi2N4/AlSb heterostructures via interlayer spacing, external electric fields, and biaxial strain

• The properties of MoSi 2 N 4 /AlSb were investigated under variations of spacing, electric field, and strain. • The reduction in interlayer distance results in a gradual narrowing of the bandgap. • As the external electric field increases, the bandgap progressively narrows, ultimately reaching 0 eV. • Under tensile strain, the bandgap decreases linearly. The MoSi 2 N 4 /AlSb heterostructure features a type-II band alignment and possesses an indirect bandgap of 0.69 eV. Work function and charge density analyses reveal an intrinsic built-in electric field ( E int ) oriented from MoSi 2 N 4 to AlSb. As the interlayer distance decreases from 3.31 to 1.31 Å, the bandgap gradually narrows from 0.69 to 0 eV. In contrast, with the interlayer spacing increasing from 3.31 to 5.31 Å, the bandgap increases from 0.69 to 1.23 eV. This transition is attributed to enhanced interlayer coupling and orbital hybridization, which facilitate increased charge transfer both across and within the constituent layers. Under a positive field from 0 to 0.5 V/Å ( E ext , from MoSi 2 N 4 to AlSb), the alignment of E ext with E int augments the electrostatic barrier between layers, thereby widening the bandgap from 0.69 to 1.13 eV. Conversely, the application of a negative field (0 to −0.5 V/Å) weakens the barrier and facilitates charge transfer, progressively narrowing the bandgap from 0.69 to 0 eV. Tensile strain increases the in-plane lattice constants, thereby expanding interatomic distances and weakening orbital interactions. This causes the valence band maximum ( VBM ) of AlSb to shift upward and the conduction band minimum ( CBM ) of MoSi 2 N 4 to shift downward, ultimately reducing the bandgap from 0.69 to 0 eV. In contrast, the application of compressive strain induces a non-monotonic variation in the bandgap of the heterostructure. Specifically, as the strain increases from −1 % to −5 %, the bandgap increases from 0.77 to 0.95 eV. However, with a further increase in strain to −7 %, the bandgap decreases to 0.89 eV. In summary, the electronic characteristics of the MoSi 2 N 4 /AlSb heterostructure exhibit remarkable tunability under the influence of interlayer distance adjustments, externally applied electric fields, and mechanical strain engineering.