Effects of the oxygen vacancy concentration in InGaZnO-Based RRAM

Abstract

Resistance random access memory (RRAM) composed of stacked aluminum (Al)/InGaZnO(IGZO)/Al is investigated with different gallium concentrations. It is widely known that the increased concentration of gallium on IGZO reduces off-state current of transistors due to a decrease of oxygen vacancy (VO). As employing the previous results about thin film transistors, from the analysis of electrical properties, it is demonstrated that the controlled VO leads to bipolar resistive switching (BRS) characteristics. The stoichiometric ratio (x) of gallium in the InGaxZnO is varied from 0 to 4 for intentional control of the concentration of the VO, which influences the electrical characteristics of the RRAM. No Ga in the IGZO (x=0) significantly increases the value of VO and leads to a breakdown of the IGZO. In contrast, a high Ga concentration (x=4) suppresses the generation of VO; hence, resistive switching is disabled. Thus, the optimization for controlling the concentration of VO is necessary. The optimal value of x is 2 in terms of IGxZO. Accordingly, enduring RRAM characteristics are achieved.