The resistive switching behavior in resistive random access memories (RRAMs) using atomic-layer-deposited Ga2O3/ZnO composite film as the dielectric was investigated. By alternatively atomic-layer-depositing Ga2O3 and ZnO with different thickness, we can accurately control the oxygen vacancy concentration. When regulating ZnO to ∼31%, the RRAMs exhibit a forming-free property as well as outstanding performance, including the ratio of a high resistance state to the low resistance state of 1000, retention time of more than 1 × 104 s, and the endurance of 100. By preparing RRAMs of different Zn concentration, we carried out a comparative study and explored the physical origin for the forming-free property as well as good performance. Finally, a unified model is proposed to account for the resistive switching and the current conduction mechanism, providing meaningful insights in the development of high-quality and forming-free RRAMs for future memory and neuromorphic applications.
Keywords: ALD; Ga2O3/ZnO; RRAM; composite films; forming-free.