On the Origin of Low-Resistance State Retention Failure in HfO2-Based RRAM and Impact of Doping/Alloying

We study in detail the impact of alloying HfO₂ with Al (Hf_{1_x}Al₂xO_2+x) on the oxide-based resistive random access memory (RRAM) (OxRRAM) thermal stability through material characterization, electrical measurements, and atomistic simulation. Indeed, migration of oxygen atoms inside the dielectric is at the heart of OxRRAM operations. Hence, we performed comprehensive diffusion barrier calculations in HfO₂, Hf_{1_x}Al₂xO_2+x, and Hf_{1_x}TixO₂ relative to the oxygen vacancy (Vo) movement involved in low-resistance state (RON) thermal stability. Calculations are performed at the best level using ab initio techniques. This paper provides an insight on the improved RON stability of our Hf_{1_x}Al₂xO_2+x-based RRAM devices and predicts the degraded retention of Hf_{1_x}TixO₂-based RRAM measured in the literature. Our theoretical calculations link the origin of RON retention failure to the lateral diffusion of oxygen vacancies at the constriction/tip of the conductive filament in HfO₂-based RRAM.