Data retention and low voltage operation of Al₂O₃/Hf_0.5Zr_0.5O₂ based ferroelectric tunnel junctions

Ferroelectric random-access memories based on conventional perovskite materials are non-volatile but suffer from lack of CMOS compatibility, scalability limitation, and a destructive reading scheme. On the other hand, ferroelectric tunnel junctions based on CMOS compatible hafnium oxide are a promising candidate for future non-volatile memory technology due to their simple structure, scalability, low power consumption, high operation speed, and non-destructive read-out operation. Herein, we report an efficient strategy based on the interface-engineering approach to improve upon the tunneling electroresistance effect and data retention by depositing bilayer oxide heterostructure (Al₂O₃/Hf_0.5Zr_0.5O₂) using atomic layer deposition (ALD) on Ge substrate which is treated in-situ ALD chamber with H₂-plasma before film deposition. Integrating a thin ferroelectric layer i.e. Hf_0.5Zr_0.5O₂ (8.4 nm) with a thin interface layer i.e. Al₂O₃ (1 nm) allowed us to reduce the operation (read and write) voltage to 1.4 V, and 4.3 V, respectively, while maintaining a good tunneling electroresistance or ON/OFF ratio above 10. Furthermore, an extrapolation to 1000 years at room temperature gives a residual ON/OFF ratio of 4.