Unlocking the Potential of 2D WTe₂/ZrS₂ van der Waals Heterostructures for Tunnel Field-Effect Transistors: Broken-Gap Band Alignment and Electric Field Effects

Heterostructures composed of two-dimensional materials open new avenues for advancing semiconductor technology, particularly in the development of energy-efficient tunnel field effect transistors (TFETs). Here, we employ density functional theory calculations to investigate the electronic behavior of WTe2/ZrS2 heterostructures having diverse dimensions and arrangement motifs. Our simulations suggest that the topmost valence band of WTe2 overlaps with the bottommost conduction band of ZrS2, giving rise to the broken gap or type-III band alignment, which is favorable for fabricating TFETs. Using first-principles molecular dynamics simulations, the temperature effect on the electronic properties is studied, demonstrating that the broken gap band alignment is preserved at 300 K. Furthermore, the electronic properties of the heterostructures are shown to be affected by external electric fields: positive electric fields increase the overlap between the valence and conduction states, whereas negative electric fields lead to the opposite effect. Interestingly, a Rashba-type spin splitting is observed in the topmost valence band, and the Rashba energy is slightly influenced by the presence of external electric fields. Overall, our study sheds light on the inherent characteristics of WTe2/ZrS2 heterostructures and can be valuable for fabricating TFETs with optimal performance.