Achieving giant tunneling electroresistance ratio of up to 109% in sliding ferroelectric tunnel junctions based on MoGe2N4 bilayer

Abstract

Emerging sliding ferroelectrics hold significant potential in designing ferroelectric tunnel junctions (FTJs) with high tunneling electroresistance (TER) ratios, which are promising candidate devices for next-generation nonvolatile memories. Here, we theoretically design an FTJ utilizing the sliding ferroelectric MoGe2N4 bilayer, achieving a giant TER ratio of up to 109%. First-principles calculations reveal layer-resolved band structures near the conduction band minimum (CBM) and valence band maximum (VBM) of MoGe2N4 bilayer. Notably, biaxial tensile strain reduces its bandgap, inducing a semiconductor-to-metal transition at 8% strain. At this strain, the CBM of one specific layer shifts below the Fermi level. The layer that becomes metallic is controlled by the direction of out-of-plane electric polarization in MoGe2N4 bilayer. Crucially, the semiconducting monolayer MoGe2N4 channel can be metallized by its chemically bonded metallic lower layer within the bilayer electrodes. Specifically, when the polarization in MoGe2N4 bilayer electrodes points downward (P↓), both the lower electrode layer and the channel are metallic, resulting in a conducting state of the FTJ. Conversely, they are rendered semiconducting by the upward polarization (P↑), leading to a blocking state. Therefore, a giant TER ratio is obtained for the designed FTJ device. This work demonstrates a different architecture for high-performance FTJs based on sliding ferroelectrics.