Reaction-Drift Model for Switching Transients in Pr₀.₇Ca₀.₃MnO₃-Based Resistive RAM

Abstract

Pr$_{0.7}$Ca$_{0.3}$MnO$_3$ (PCMO) based RRAM shows promising memory properties like non-volatility, low variability, multiple resistance states and scalability. From a modeling perspective, the charge carrier DC current modeling of PCMO RRAM by drift diffusion (DD) in the presence of fixed oxygen ion vacancy traps and self-heating (SH) in Technology Computer Aided Design (TCAD) (but without oxygen ionic transport) was able to explain the experimentally observed space charge limited conduction (SCLC) characteristics, prior to resistive switching. Further, transient analysis using DD+SH model was able to reproduce the experimentally observed fast current increase at ~100 ns timescale, prior to resistive switching. However, a complete quantitative transient current transport plus resistive switching model requires the inclusion of ionic transport. We propose a Reaction-Drift (RD) model for oxygen ion vacancy related trap density variation, which is combined with the DD+SH model. Earlier we have shown that the Set transient consists of 3 stages and Reset transient consists of 4 stages experimentally. In this work, the DD+SH+RD model is able to reproduce the entire transient behavior over 10 ns - 1 s range in timescale for both the Set and Reset operations for different applied biases and ambient temperatures. Remarkably, a universal Reset experimental behavior, log(I) is proportional to (m X log(t)) where m~-1/10 is reproduced in simulations. This model is the first model for PCMO RRAMs to significantly reproduce transient Set/Reset behavior. This model establishes the presence of self-heating and ionic-drift limited resistive switching as primary physical phenomena in these RRAMs.