Conduction mechanism of a TaOx-based selector and its application in crossbar memory arrays

Abstract

The conduction mechanism of a Pd/TaO_x/Ta/Pd selector device, which exhibits high non-linearity (∼10⁴) and excellent uniformity, has been systematically investigated by current–voltage–temperature characterization. The measurement and simulation results indicate two dominant processes of selector current at opposite biases: thermionic emission and tunnel emission. The current–voltage–temperature behaviors of the selector can be well explained using the Simmons’ trapezoidal energy barrier model. The TaO_x-based selective layer was further integrated with a HfO₂-based resistive switching layer to form a selector-less resistive random access memory (RRAM) device structure. The integrated device showed a reliable resistive switching behavior with a high non-linearity (∼5 × 10³) in the low resistance state (LRS), which can effectively mitigate the sneak path current issue in RRAM crossbar arrays. Evaluations of a crossbar array based on these selector-less RRAM cells show less than 4% degradation in read margin for arrays up to 1 Mbit in size. These results highlight the different conduction mechanisms in selector device operation and will provide insight into continued design and optimization of RRAM arrays.