Variability Improvement of TiOx/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 TiOx/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 TiOx/Al2O3 bilayer RRAM devices by interfacial band engineering with an ultrathin Al2O3 dielectric material.