Effects of Charge Imbalance on Field-Induced Instability of HfO2-Based Ferroelectric Tunnel Junctions

Abstract

Ferroelectricity in hafnium-based materials has attracted significant research attention and is used in various applications owing to their complementary metal-oxide-semiconductor compatibility, scalability, and low-power operation. However, their widespread integration into various technologies is hindered by reliability and stability problems, particularly field-induced instability, which causes fluctuations in polarization characteristics during operation. Herein, on the underlying mechanism of field-induced instability is reported in pure hafnium oxide films within metal-ferroelectric-insulator-semiconductor (MFIS) ferroelectric tunnel junctions (FTJs). The comprehensive material analysis combined with low-frequency noise (LFN) measurements reveals that the presence of oxygen vacancies and interface traps within the ferroelectric and dielectric layers induces a charge imbalance in the FTJ, leading to distortion in its polarization characteristics and the onset of cyclic evolution in field-induced instability. Furthermore, high-pressure annealing effectively mitigates field-induced instability by reducing the defects within the film, thereby alleviating the associated charge imbalance. These findings contribute to a deeper understanding of the internal dynamics of FTJs and provide an efficient approach to enhancing their stability.