Variability Improvement of TiO_x/Al₂O₃ Bilayer Nonvolatile Resistive Switching Devices by Interfacial Band Engineering with an Ultrathin Al₂O₃ Dielectric Material

Variability control over the resistive switching process is one of the key requirements to improve the performance stability of the resistive random access memory (RRAM) devices. In this study, we show the improvement of the variability of the resistive switching operation in the TiO_x/Al₂O₃ bilayer RRAM devices. The achievement is based on the thickness engineering of the Al₂O₃ layer. A thick Al₂O₃ dielectric actively takes part to control the resistive switching behavior; on the contrary, the ultrathin layer of Al₂O₃ behaves as the tunnel barrier in the structure. At lower voltage, the low resistance state conductions follow the trap-assisted tunneling and Fowler–Nordheim tunneling for the thick and thin Al₂O₃ RRAMs, respectively. Finally, the variation control in device forming, SET voltage distribution, high resistance state, low resistance state, and resistance ratio is achieved with the TiO_x/Al₂O₃ bilayer RRAM devices by interfacial band engineering with an ultrathin Al₂O₃ dielectric material.