Robustly stable intermediate memory states in HfO2−based ferroelectric field−effect transistors

Multilevel ferroelectric field−effect transistors (FeFETs) integrated with HfO2−based ferroelectric thin films demonstrate tremendous potential in high−speed massive data storage and neuromorphic computing applications. However, few works have focused on the stability of the multiple memory states in the HfO2−based FeFETs. Here we firstly report the write/read disturb effects on the multiple memory states in the Hf0.5Zr0.5O2 (HZO)−based FeFETs. The multiple memory states in HZO−based FeFETs do not show obvious degradation with the write and read disturb cycles. Moreover, the retention characteristics of the intermediate memory states in HZO−based FeFETs with unsaturated ferroelectric polarizations are better than that of the memory state with saturated ferroelectric polarization. Through the deep analysis of the operation principle of in HZO−based FeFETs, we speculate that the better retention properties of intermediate memory states are determined by the less ferroelectric polarization degradation and the weaker ferroelectric polarization shielding. The experimental and theoretical evidences confirm that the long−term stability of the intermediate memory states in HZO−based FeFETs are as robust as that of the saturated memory state, laying a solid foundation for their practical applications.