Oxygen Vacancy Density Dependence with a Hopping Conduction Mechanism in Multilevel Switching Behavior of HfO₂-Based Resistive Random Access Memory Devices

We report a switching model that directly explains the change in activation energy (EAC) at different RESET stop voltages (Vstop) in HfO2-based resistive random access memory devices. The dependence of oxygen vacancy-driven conductive filaments (Vo2+) density (nD) on Vstop was validated by a kinetic Monte Carlo (kMC) simulation and hopping conduction mechanism. A wide operating range of temperatures from −40 to 175 °C is achieved with stable endurance of 100 ns short pulses and high retention of more than 10 years at 125 °C. Distinct exponentially increased multilevel high-resistance states are observed at increasing Vstop and is attributed to the increase in EAC with Vstop. The increase in EAC due to the increase in Vstop and depletion of nD during RESET was explained using our proposed switching model. A kMC simulation further emphasizes this relation due to the depletion of Vo2+ during RESET, which was supported by the increase in trap-to-trap distance in the hopping conduction analysis.