Tunneling electroresistance Effect Enhanced by Polar Interface in Hafnia-based Ferroelectric Tunnel Junction

Abstract

Ferroelectric tunnel junctions (FTJs) have attracted considerable attention for emerging non-volatile memory and neuromorphic devices [1,2]. The conventional structure of FTJs consists of a ferroelectric thin film sandwiched between two metal electrodes (See Fig. 1). The polarization reversal of the ferroelectric layer modulates the potential barrier, leading to switching between two tunneling resistance states. It is called tunneling electroresistance (TER) effect. Recent studies have demonstrated FTJs based on the ferroelectric HfO2 (FE-HfO2), which is compatible with the Si-based CMOS process [2, 3]. However, FTJs with FE-HfO2 still exhibit a low TER ratio defined as ON/OFF current ratio. In this work, we investigate the effect of the atomic termination of Zr doped FE-HfO2 (FE-HZO) on the performance of FTJs using density functional theory calculation. Our results report that depending on the polar interface of the atomic termination in FEHZO, the properties of the potential barrier, such as barrier height and electric field, can be significantly tailored (See Fig. 1). As shown in Fig. 2, the improved TER ratio can be driven by only constructing the asymmetric polar interfaces in the FTJs, because the potential barrier between the two polarization states becomes asymmetric. We expect that the interface engineering of FE-HZO becomes a feasible approach to improve the TER effect in FE HfO2-based tunnel junctions.