Understanding Controlled Ion Doping Mechanism of Vertical Sensing Electrochemical Random Access Memory Using Ion-Permeable Graphene Electrodes

In this article, we propose vertical sensing electrochemical random-access memory (VS-ECRAM) with improved synaptic behaviors for the neuromorphic application. This new type of ECRAM uses a monolayer graphene layer located between the electrolyte and channel layer, serving as both a barrier and a drain electrode. Controlled ion doping behavior was achieved through the barrier effect of monolayer graphene, resulting in excellent weight-update linearity. The constant ion injection and uniform ion distribution in the channel were verified through device simulation using ionic current mapping. In addition, the graphene barrier was effective in ensuring robust endurance and retention by obstructing ion mixing at the interface between the channel and electrolyte. Furthermore, based on the excellent scalability of the vertical channel structure, the device was scaled down to $30\times30$ nm ² , resulting in reduced read/write energy consumption ( $\sim $ 5 fJ/pulse) and improved read latency ( $\times 20$ ). Finally, a $32\times32$ VS-ECRAM array was fabricated with $4{F}^{\,{2}}$ of cell layout and a high Modified National Institute of Standards and Technology (MNIST) pattern recognition accuracy (95.39%) was evaluated with near-ideal synaptic characteristics.