Enlarged read window in the asymmetric ITO/HfOx/TiN complementary resistive switch

The narrow read-window of most complementary resistive switches proposed to-date poses a significant challenge to array level implementation, as inherent variations in the set and reset voltages result in an unacceptably small read margin. In this work, we present the asymmetrical ITO/HfOx/TiN complementary resistive switch, with a significantly enlarged positive read window of 1.6 V as compared to the much narrower window of 0.5 V of the symmetrical TiN/HfOx/TiN switch. A read margin of 1.1 V is obtained after accounting for statistical variations, representing a significant improvement over the 0.1 V margin of the symmetrical counterpart. Analyses show that the enlarged read window may be ascribed to two important attributes: (1) the stronger affinity of ITO for oxygen, which leads to a reduced positive set voltage and (2) a larger work function of the ITO, resulting in an increase in the positive reset voltage.