Symmetric Linear Rise and Fall of Conductance in a Trilayer Stack Engineered ReRAM-Based Synapse

• Published in: ACS applied electronic materials 2020-10, Vol.2 (10), p.3263-3269
• Main Authors: Vishwakarma, Kavita, Kishore, Rishabh, Datta, Arnab
• Format: Article
• Language: English
• ISSN: 2637-6113; 2637-6113
• DOI: 10.1021/acsaelm.0c00585

Tapered conductive filament is crucial to safeguard the ideal symmetric linear variation in conductance during learning (potentiation) and forgetting (depression) phases in a neuromorphic synapse, electrically realized with resistive random access memory (ReRAM) cell. Here, we have demonstrated that, by engineering the spatial location of an AlO x intermediate layer in a trilayer ReRAM stack having ZrO x /AlO x /HfO x in a fixed total stack thickness, oxygen vacancies can be nonuniformly distributed, and as a result, an appropriate taper structure of the filament can be realized. Furthermore, spatial location of the AlO x layer in the trilayer stack determines the amount of leakage in the off state of the cell and hence its read current margin between the different conducting states. A remarkable conductance linearity with symmetry was obtained by input pulsing to a favorable ReRAM cell, while improvement in its characteristics was found because of its tapered filament structure and low leakage current resulted due to the farthest AlO x layer in stack with respect to the top electrode than the remaining cells.