Low power Ti-doped NbO₂-based selector device with high selectivity and low OFF current

The crossbar array-based resistive memory is considered a potential architecture for high-density nonvolatile memory applications. However, the sneak current path problem associated with the crossbar array structure limits its use in practical applications. This limitation can be removed by employing a selector device in the crossbar array structure. Therefore, we propose NbO₂ as a selector device as it operates at a rapid speed during the insulator-metal transition (IMT). Herein, we fabricated a Ti-doped NbO₂ selector device and demonstrated a very low OFF current (5 × 10^-11 A). The effect of Ti doping in the NbO₂ device was studied by varying the Ti concentration during a radio frequency co-sputtering process. We intentionally prevented the formation of Nb₂O₅, and a high-quality NbO₂ layer was deposited with an appropriate Ti concentration. Furthermore, we modulated the IMT characteristics of the NbO₂ device by varying the Ti concentration. The fabricated Ti-doped NbO₂ selector device showed an I_ON/I_OFF ratio greater than 5 × 10⁴. Additionally, a drift-free fast switching operation (<20 ns) was achieved for the optimized selector device. These results suggest the high suitability of IMT-based NbO₂ devices in selector applications.