A study on the resistance switching of Ag₂Se and Ta₂O₅ heterojunctions using structural engineering

The resistive random access memory (RRAM) devices with heterostuctures have been investigated due to cycling stability, nonlinear switching, complementary resistive switching and self-compliance. The heterostructured devices can modulate the resistive switching (RS) behavior appropriately by bilayer structure with a variety of materials. In this study, the bipolar resistive switching characteristics of the bilayer structures composed of Ta₂O₅ and Ag₂Se, which are transition-metal oxide (TMO) and silver chalcogenide, were investigated. The bilayer devices of Ta₂O₅ deposited on Ag₂Se (Ta₂O₅/Ag₂Se) and Ag₂Se deposited on Ta₂O₅ (Ag₂Se/Ta₂O₅) were fabricated for investigation of the RS characteristics by stacking sequence of Ta₂O₅ and Ag₂Se. All operating voltages were applied to the Ag top electrode with the Pt bottom electrode grounded. The Ta₂O₅/Ag₂Se device showed that a negative voltage sweep switched the device from high resistance state (HRS) to low resistance state (LRS) and a positive voltage sweep switched the device from LRS to HRS. On the contrary, for the Ag₂Se/Ta₂O₅ device a positive voltage sweep switched the device from HRS to LRS, and a negative voltage sweep switched it from LRS to HRS. The polarity dependence of RS was attributed to the stacking sequence of Ta₂O₅ and Ag₂Se. In addition, the combined heterostructured device of both bilayer stacks, Ta₂O₅/Ag₂Se and Ag₂Se/Ta₂O₅, exhibited the complementary switching characteristics. By using threshold switching devices, sneak path leakage can be reduced without additional selectors. The bilayer heterostructures of Ta₂O₅ and Ag₂Se have various advantages such as self-compliance, reproducibility and forming-free stable RS. It confirms the possible applications of TMO and silver chalcogenide heterostructures in RRAM.