Operations, Charge Transport, and Random Telegraph Noise in HfOx Resistive Random Access Memory: a Multi-scale Modeling Study

In this work we explore the mechanisms responsible for Random Telegraph Noise (RTN) fluctuations in HfOx Resistive Random Access Memory (RRAM) devices. The statistical properties of the RTN are analyzed in many operating conditions exploiting the Factorial Hidden Markov Model (FHMM) to decompose the multilevel RTN traces in a superposition of two-level fluctuations. This allows the simultaneous characterization of individual defects contributing to the RTN. Results, together with multi-scale physics-based simulations, allows thoroughly investigating the physical mechanisms which could be responsible for the RTN current fluctuations in the two resistive states of these devices, including also the charge transport features in a comprehensive framework. We consider two possible options, which are the Coulomb blockade effect and the possible existence of metastable states for the defects assisting charge transport. Results indicate that both options may be responsible for RTN current fluctuations in HRS, while RTN in LRS is attributed to the temporary screening effect of the charge trapped at defect sites around the conductive filament.