Multifield modulation of electronic structure in MoSi2N4/GeI2 van der Waals heterostructures

Abstract

Through first-principles calculations, we systematically explored the evolution of the electronic structure of MoSi₂N₄/GeI₂ van der Waals heterostructure (vdWH) under biaxial strain, interlayer separation, and externally applied perpendicular electric fields. The pristine vdWH emerges as a direct-gap semiconductor with a bandgap of 1.69 eV. A compressive strain of 4% increases the bandgap to a maximum of 2.23 eV, whereas a tensile strain induces a precipitous reduction to 0.63 eV at 8%. Variations in interlayer spacing exert an equally pronounced influence: the bandgap broadens to 1.83 eV at 3.06 Å, but collapses abruptly to 0.16 eV upon further contraction to 1.56 Å. Perpendicular E-fields provide an additional lever of control; a modest field of -0.1 V Å^-1 elevates the bandgap to 1.85 eV, while stronger fields of -0.5 V Å^-1 quench the gap entirely, driving the system into a metallic state. The underlying mechanisms governing these bandgap modulations are elucidated in detail. Collectively, these results highlight the remarkable tunability of MoSi₂N₄/GeI₂ vdWH, thereby providing a theoretical framework for the rational conception of next-generation devices in the optoelectronic and flexible electronic domains.