In Quest of Nonfilamentary Switching: A Synergistic Approach of Dual Nanostructure Engineering to Improve the Variability and Reliability of Resistive Random-Access-Memory Devices

This study demonstrates a synergistic approach of dual nanostructure engineering to improve the performance of AlO_x-based resistive random access memory (RRAM) devices. More precisely, a novel material stack engineering of RRAM with nonlinear area scalable low current switching and extensive improvement of reliability and variability issues is reported. Dual nanostructures (nanodome bottom electrode and nanocrystals in switching layer) in RRAM is an effective way to change the switching from filamentary to a nonfilamentary one, resulting in forming-free highly stable device. Several methods such as transmission electron microscopy, energy dispersive spectroscopy, and atomic force microscopy have been employed to investigate the morphology of the RRAM devices. Enhanced electric field within the enclave of switching layer is controlling the intrinsic distribution of oxygen vacancy profile with extrinsic operation. As compare to filamentary RRAM, nonfilamentary devices can effectively control dc switching for >10³ cycles, ac switching for >10⁶ cycles without any severe fluctuation of resistance states for different levels. Area and temperature-dependent semiconducting behavior along with time-dependent high resistance states are certainly confirming the nonfilamentary switching process. In addition, the device yield improvement ≈98% using nonfilamentary switching, is making dual nanostructure devices a very promising candidate for high-density memory application, is highlighted.