Thermally Oxidized Al_xGa_2-xO₃/n-Al_0.6Ga_0.4N:Si Unipolar Resistive Random-Access Memory

Thermally oxidized Al_xGa_2-xO₃/n-Al_0.6Ga_0.4N:Si resistive random access memory (RRAM) presented unipolar resistive switching characteristics. The resistance ratio of the high-resistance state (HRS) to the low-resistance state (LRS) was higher than 10⁴ for the RRAM device. After a retention time of 10000 s, the ratio of HRS/LRS exhibited no obvious degradation. The thickness of the Ti layer on the top electrode affected the switching cycles of the RRAM. The resistive switching cycles increased from 17 to 45 times with increasing Ti thickness from 1 to 5 nm. In addition to the effect of Ti thickness, the oxygen (O₂) plasma treatment on the thermally oxidized Al_xGa_2-xO₃ layer improved the resistive switching cycles of the RRAM. The resistive switching cycles increased from 45 to 165 times with increasing the O₂ plasma treatment time from 0 to 90 min. Ti formed a TiO_x layer, which could act as an oxygen reservoir. Thick Ti and O₂ plasma treatment could increase the amount of oxygen in the TiO_x layer. Oxygen could be supplied to the conductive filaments for redox reactions, leading to an improvement in the resistive switching cycle of RRAM.