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 Al2O3thin layer between the TiN bottom electrode and the HfO2switching film. The nonlinear switching mechanism caused by Flower-Nordheim tunneling involves the tunneling barrier of the Al2O3layer. Besides, the nonlinear behavior is also sensitive to the thickness of the inserting Al2O3layer. 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.