Electronic characteristics of the two-dimensional van der Waals ferroelectric -In₂Se₃/Cs₃Bi₂I₉ heterostructures

Two-dimensional (2D) van der Waals (vdWs) ferroelectric heterostructures provide a platform to design multifunctional electronic devices. In this Letter, the 2D vdWs ferroelectric alpha-In2Se3/Cs3Bi2I9 heterostructures were constructed to investigate the appropriate band alignment, effective masses, charge transfer, and polarization switching barriers by employing first-principle calculation. The results show that the polarization reversal of alpha-In2Se3 engineers band alignment transition from type-II (alpha-In2Se3-P up arrow/Cs3Bi2I9) to type-I (alpha-In2Se3-P down arrow/Cs3Bi2I9), resulting in an indirect bandgap changing from 0.09 to 0.75 eV. Calculated electron effective masses are isotropic, which is smaller than those of anisotropic hole effective masses. Interfacial charges transfer from Cs3Bi2I9 to alpha-In2Se3, which can be ascribed to work function difference. By combining non-equilibrium Green's functions, the current-voltage characteristics of alpha-In2Se3/Cs3Bi2I9 based ferroelectric tunnel junction were investigated, and the current on/off ratio of 10(3) is resulted by spatial charge carrier separation and recombination. The proposed electron-hole separation transport design strategy provides a comprehensive theoretical support for the development of microelectronic storage devices.