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

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 Gamma-Y direction can reach 5891.42 cm2 V-1 s-1, while the hole mobility along the Gamma-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 x 105 cm-1. Therefore, the discovery of ul-trahigh anisotropic carrier mobility and optical properties from the GaP/GaSe vdWH provides fertile ground for exploring promising photovoltaic and optoelectric nanodevices.