Strain-Robust and Electric Field Tunable Band Alignments in van der Waals WSe₂–Graphene Heterojunctions

We study the band alignments and band structures of van der Waals WSe₂–graphene heterojunctions by varying out-of-plane external electric field and in-plane mechanical strain using density-functional calculations. We find that the electronic properties of WSe₂–graphene heterojunctions are insensitive to the change of the mechanical strain, showing strong robustness. However, the external electrical field intensity is able to significantly change the band alignments of WSe₂–graphene heterojunctions, while a constant band gap value of WSe₂ in the heterojunctions is nearly maintained. We further show that the highest hole concentration injected by the external electric field is estimated as high as 6.40 × 10¹² cm^–2, while the highest electron density is about 3.00 × 10¹² cm^–2. These findings suggest that the WSe₂–graphene heterojunctions are a promising structure instrumental for electronic device applications