Ferroelectric tunnel junction based on Zr0.75Hf0.25O2/Al2O3 composite barrier

Ferroelectric tunnel junction (FTJ) with tunable tunnel electroresistance is promising for emerging nonvolatile memory applications. In this work, 6 nm-thick Hf-doped ZrO2 ferroelectrics with Zr : Hf = 3 : 1 (ZHO), exhibiting a high remanent polarization of 30 μC/cm2, was prepared and further used to build Pt/ZHO/Al2O3/W FTJ devices with adding 1 nm-thick Al2O3 dielectric layer to reduce the leakage. The FTJ delivered superior performance with a tunneling electroresistance ratio of over 7000, outperforming previously reported other FTJ devices based on hafnia/zirconia ferroelectrics. Under 100 ns single-pulse writing, the FTJ exhibited multiple stable states, good retention over 104 s, and switching endurance exceeding 5 × 104 cycles. Additionally, it delivered a relatively high read current density of 8 A/cm2 at 0.2 V. The results demonstrate that the ZHO/Al2O3 composite structure can effectively alter the tunneling barrier height and increase tunneling current, resulting in a large ON/OFF ratio. The results underscore a great potential of ZHO ferroelectrics in the future development of high-performance nonvolatile memory technologies.