Strain-Enabled Polarity Reversal of Transport in Bi/MoS₂ van der Waals Heterostructures

Strain engineering serves as a powerful strategy for modulating the electronic properties of semiconductors and enhancing device performance. In this work, we employ first-principles calculations to systematically explore the mechanical properties, electronic structure, and charge carrier mobility of a bismuth/molybdenum disulfide (Bi/MoS₂) van der Waals heterostructure under applied strain. The heterostructure demonstrates notable mechanical robustness and pronounced anisotropy. For the AB₁ stacking configuration, the electron mobility reaches 1.51×10⁵ cm²·V⁻¹·s⁻¹ and 1.56×10⁴ cm²·V⁻¹·s⁻¹ along the x and y directions, respectively, while the hole mobility is 1.56×10⁵ cm²·V⁻¹·s⁻¹ and 1.65×10³ cm²·V⁻¹·s⁻¹-one to two orders of magnitude lower than that of electrons. Remarkably, under a 2% strain, the electron mobility attains 6.5×10⁴ cm²·V⁻¹·s⁻¹ and 2.66×10⁶ cm²·V⁻¹·s⁻¹, whereas the hole mobility rises significantly to 2.9×10⁴ cm²·V⁻¹·s⁻¹ and 7.4×10⁵ cm²·V⁻¹·s⁻¹. This results in a striking polarity reversal, with hole mobility surpassing that of electrons by one to two orders of magnitude. Our findings reveal that strain not only effectively tunes the electronic structure but also induces a switch in the dominant charge carrier type-from electrons to holes-under specific strain conditions. These insights provide critical theoretical guidance for the design of strain-modulated electronic devices based on Bi/MoS₂ heterostructures.