A type-II GaP/GaSe van der Waals heterostructure with high carrier mobility and promising photovoltaic properties

[Display omitted] •The GaP/GaSe van der Waals heterostructure (vdWH) exhibits a type-II staggered band alignment with an indirect bandgap of 1.59 eV.•The GaP/GaSe (vdWH) possesses excellent carrier mobility with high anisotropy.•The external vertical electric field can effectively modify the electronic band dispersion structure and induce the near-free electronic (NFE) states in GaP/GaSe (vdWH).•The carrier mobility of GaP/GaSe vdWH is sensitive to compressive strain and the hole mobility is up to 129891.12 cm2 V−1 s−1 at a compressive strain of –5 %.•The GaP/GaSe vdWH has a small exciton binding energy of 0.35 eV and an excellent optical absorption coefficient in the visible region. In this paper, a novel GaP/GaSe van der Waals heterostructure (vdWH) is constructed, and using first-principles calculations, the geometric, electronic, transport, and optical properties of the heterostructure are systematically explored. The stability of the constructed GaP/GaSe vdWH is verified using binding energy, phonon spectra, ab initio molecular dynamics (AIMD) simulation, and elastic constants. The results demonstrate that the GaP/GaSe vdWH has a type-II staggered band alignment with an indirect bandgap of 1.59 eV and possesses excellent carrier mobility with high anisotropy. The electron mobility along the Γ–Y direction can reach 5891.42 cm2 V−1 s−1, while the hole mobility along the Γ–X direction is up to 7944.29 cm2 V−1 s−1. Additionally, the near-free electronic (NFE) states induced by the electric field can significantly reduce the bandgap of the vdWH and even turn it into metal. Meanwhile, at a compressive strain of −2 %, the hole mobility of GaP/GaSe vdWH can reach 129891.12 cm2 V−1 s−1. According to calculations, the exciton binding energy of the vdWH is 0.35 eV and the optical absorption coefficient in the visible region is up to 4.8 × 105 cm−1. Therefore, the discovery of ultrahigh anisotropic carrier mobility and optical properties from the GaP/GaSe vdWH provides fertile ground for exploring promising photovoltaic and optoelectric nanodevices.