Electric field-tunable electronic properties of GaTe/GaSe van der Waals heterobilayers: a first-principles study

We conduct a comprehensive first-principles study on the electronic properties of GaTe/GaSe van der Waals heterobilayers, focusing on the effects of stacking order and a perpendicular electric field. While the individual monolayers exhibit indirect band gaps, the heterobilayers develop a direct band gap at the Brillouin zone center due to interlayer orbital hybridization. Projected density of states analyses reveal that the valence and conduction band edges originate from orbitals localized in different layers, indicating a type-II band alignment favorable for charge separation. Application of a perpendicular electric field induces a tunable band gap reduction and reinforces the type-II character through asymmetric charge redistribution and enhanced layer-specific localization. Notably, the system exhibits a strong polarity-dependent response under positive and negative fields, arising from the intrinsic chemical asymmetry between GaTe and GaSe. This electric-field-driven modulation offers a viable strategy for engineering the electronic structure of Ga-based heterostructures toward high-performance nanoelectronic and optoelectronic applications.