Field-tunable Schottky-to-ohmic contact transition and visible-light absorption enhancement in a newly predicted 2D B3S/graphene van der Waals heterostructure

Two-dimensional (2D) semiconductors with tunable interfacial and optical properties are vital for advanced nanoelectronic and optoelectronic devices. Using global structure prediction and first-principles calculations, we identify a previously unknown low-energy 2D B3S phase with a distinctive S–B–B–S layered configuration. The B3S monolayer is dynamically and thermally stable (up to 2000 K under ab initio molecular dynamics) and exhibits an indirect wide bandgap of 4.21 eV (HSE06) and strong intrinsic ultraviolet absorption. A B3S/graphene van der Waals heterostructure forms an n-type Schottky contact at equilibrium. Under a perpendicular electric field, the interface shows a reversible Schottky-to-Ohmic transition, achieving field-tunable carrier polarity and barrier control through charge redistribution and built-in electric fields. Moreover, visible-light absorption is significantly enhanced and spectrally tunable owing to interlayer electronic hybridization. These findings introduce a novel 2D B3S semiconductor and demonstrate a feasible strategy for designing field-responsive, broadband optoelectronic heterostructures with reconfigurable transport and photoresponse properties.