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

Abstract

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 TiOx-based devices, Al/TiOx/Al devices as a control group and Cu/TiOx/Al devices as an experimental group, and compare their rectification characteristics. As a result, a rectification ratio in Cu/TiOx/Al devices is much larger than that of Al/TiOx/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 TiOx. In addition, it is established that the high rectification ratio of Cu/TiOx/Al devices is capable of constructing large-sized memory array with reliable read margin by simply adjusting energy barrier height