Mechanism of Nonlinear Switching in HfO2-Based Crossbar RRAM With Inserting Large Bandgap Tunneling Barrier Layer

In this paper, the nonlinear switching mechanism of the Ti/HfO₂/Al₂O₃/TiN crossbar structure resistive random access memory device with good reliability is investigated. The nonlinearity of the device can be revealed by inserting a large bandgap of an Al₂O₃ thin layer between the TiN bottom electrode and the HfO₂ switching film. The nonlinear switching mechanism caused by Flower-Nordheim tunneling involves the tunneling barrier of the Al₂O₃ layer. Besides, the nonlinear behavior is also sensitive to the thickness of the inserting Al₂O₃ layer. A high nonlinear factor of 37, large endurance more than 10⁴, and good retention properties are achieved in the Ti/HfO₂/Al₂O₃ (1-nm)/TiN structure.