Improved rectification characteristics by engineering energy barrier height in TiO_x-based RRAM

Resistive random access memory (RRAM) is a strong candidate for next-generation memory. Despite its versatility, the sneak path current severely threatens accurate read operations, preventing RRAM from being expanded to high density array. To solve this sneak path current, here we propose a method to enhance a rectification effect through barrier height engineering. We fabricated two TiO_x-based devices, Al/TiO_x/Al devices as a control group and Cu/TiO_x/Al devices as an experimental group, and compare their rectification characteristics. As a result, a rectification ratio in Cu/TiO_x/Al devices is much larger than that of Al/TiO_x/Al devices, e.g., approximately 122 times for low-resistance-state and 251 times for high-resistance-state. Furthermore, we analyze the energy band diagram considering the bias polarity and electric-field-driven oxygen ion migration. It is confirmed that the rectification effect results from high energy barrier height between Cu top electrode and TiO_x.