HZO-based ferroelectric tunnel junction in crossbar structure enabling high current reading and large memory window

Here, we report the fabrication of an ultrathin ZrO2/Hf0.5Zr0.5O2-based ferroelectric tunnel junction (FTJ) in a crossbar structure, which exhibits both a large memory window and high current reading, two essential criteria to meet in the practical integration of hafnia-based FTJ memory chips. Giant tunnel electroresistance ratios of over 107 are obtained, attributable to the superior ferroelectric stack of FTJs. The ON-state read current density is roughly inversely proportional to the critical dimension of the crossbar FTJ, with over 600 A/cm2 reached with a 3.5 μm device and 4000 A/cm2 with a submicrometer-sized one, which projects a promising trend in lateral scaling. Under 10 ns single-pulse programming, the FTJs are capable of multiple distinct stable resistance states and can survive up to 7.3 × 106 bipolar switching cycles with a stable memory window of over 10 000. Crossbar FTJs also demonstrate superb synaptic behaviors, including nearly symmetrical and linear long-term potentiation/depression, indicating their great potential in neuromorphic computing. An in-series threshold switching selector is further integrated with a crossbar FTJ to form a one-selector-one-resistor memory, which maintains a large memory window and high current density, paving the way for realizing high-density integration of FTJ crossbar arrays. This work demonstrates the coexistence of a large switching window and high current reading in scaled FTJs with ultrathin fluorite-structured ferroelectrics through back-end-of-line-compatible processing, foreseeing a bright pathway toward the mass production of hafnia-based FTJ memory.