Electric Field Driven Band Alignment Changes and Charge Redistribution in Defective Graphene/hBN van der Waals Heterostructures

Van der Waals heterostructures made of graphene and hexagonal boron nitride (hBN) are a viable choice for energy-efficient Nanoelectronics and tunnelling devices because their interfaces are atomically sharp and their band alignment can be changed by changing the voltage. In this study, we conduct a first-principles (DFT) analysis of the influence of external out-of-plane electric fields on band alignment and charge redistribution in defective graphene/hBN heterostructures, focusing on defect-localised states within the hBN barrier. We construct ideal and defective stacks with periodic slab models and analyse them using band structures, projected density of states, and real-space charge density difference maps. Point defects in hBN introduce localised gap states which hybridise with graphene states and serve as sensitive electronic 'probes' of the local electrostatic environment. The energy levels of the defects react to an applied electric field perpendicular to the interface in a way similar to the Stark effect. This is also related to a charge redistribution at the graphene/hBN interface. The direction and the magnitude of the band alignment shift are determined by the field polarity and the microscopic nature of the defect. This implies that there is a tunability window for each defect. These results describe a quantitative approach for the engineering of field programmable electronic landscapes in graphene/hBN stacks through the combination of defect design and electrostatic control. The study offers a computer model for the enhancement of 2D functional heterostructures for low-power switching, defect-assisted tunnelling modulation, and reconfigurable device concepts that are relevant for smart and sustainable functional materials. DOI: https://doi.org/10.17762/ijisae.v12i23s.8266