Enhanced carrier separation in ferroelectric In2Se3/MoS2 van der Waals heterostructure

Abstract

α-In₂Se₃, a recently reported two-dimensional (2D) van der Waals (vdW) ferroelectric, is gaining significant attention due to its potential applications in nano-scale devices. Here, we have systematically investigated the electronic properties of three configurations of In₂Se₃/MoS₂(I, II, III) heterostructures by first-principles calculations. The results reveal that the intrinsic ferroelectricity polarization in α-In₂Se₃ can dramatically tune the electronic properties. When the out-of-plane ferroelectric polarization field is pointing from In₂Se₃ towards MoS₂, the energy band of the heterostructure is type-II band alignment with a band gap of 0.8 eV, which is beneficial for carrier separation. With reversal of the ferroelectric polarization, the band alignment switches from type-II to type-I with a band gap of 1.6 eV, which is suitable for luminescence device applications. Based on the nonequilibrium Green's function method (NEGF), the calculated photoinduced current density under visible-light radiation is up to ∼0.5 mA cm⁻² in the In₂Se₃/MoS₂(I) heterostructure, which can remarkably exceed that of thin-film silicon devices at a phonon energy below 2.5 eV. Moreover, the band alignment transition can also be realized through the application of an external electric field. We believe that the present work will greatly enlarge the potential applications of the In₂Se₃-based heterostructures in future nano-optoelectronic devices.