GaN/WS2 trilayer heterostructure with tunable band alignment via polarization.

The functional potential and charge-carrier dynamics in van der Waals heterostructures are critically influenced by their electronic band alignment. This alignment can be reconfigured by exploiting spontaneous out-of-plane polarization-induced shifts in the surface energy bands of individual layers. Using density functional theory (DFT), we systematically study how polarization orientation in a two-dimensional buckled GaN layer governs the electronic structure of GaN/WS₂ heterostructures. Simulations reveal that reversing the GaN layer's polarization direction directly modifies the relative band edge positions of the constituent materials, enabling controllable transitions between type-I and type-II band alignments. Such inherent adjustability, when synergized with externally applied electric fields, provides a dual mechanism for on-demand bandgap and alignment tuning with reduced energy consumption. Enhanced interlayer coupling in these heterostructures also enhances light absorption efficiency, exhibiting higher absorption coefficients and a wider spectral response range than isolated WS₂ and GaN monolayers. These tailored optoelectronic properties highlight GaN/WS₂ heterostructures as adaptable candidates for advanced photonic and electronic devices.