Resistive switching characteristics of devices having a trilayer CuAlO_x structure in the dark and under visible light illumination

The multilevel resistive switching (R_S) characteristics of In/CuAlO_1.85/CuAlO_1.92/CuAlO_1.85/heavily doped n-type Si (n⁺-Si) devices are studied. The sensitivity of the R_S characteristics to visible light illumination provides an opportunity to realize stable and reliable R_S properties. The In/CuAlO_1.85/CuAlO_1.92/CuAlO_1.85/n⁺-Si device in the dark shows R_S behavior, whereas the In/CuAlO_1.85/CuAlO_1.92/CuAlO_1.85/n⁺-Si device under visible light illumination exhibits the set/reset-free characteristics and the absence of the hysteresis window. The oxygen vacancy (V_O)–solar irradiation interaction is proposed to describe the multilevel R_S characteristic for the In/CuAlO_1.85/CuAlO_1.92/CuAlO_1.85/n⁺-Si device. The significant R_S degradation for devices under light illumination is due to the charge change of V_O states. The switching conduction mechanism is primarily described as space charge limited conduction according to the electrical transport properties measurement. The findings show the importance of simultaneous control of the positively charged V_O density and V_O distribution in achieving optimization of oxide-based memory devices.