Dynamic band alignment modulation of ultrathin WO _x /ZnO stack for high on/off ratio field-effect switching applications

A two-dimensional (2D) WO_x/ZnO stack reveals a unique carrier transport behavior, which can be utilized as a novel device element to achieve a very high on/off ratio (>10⁶) and an off current density lower than 1 nA cm^-2. These unique behaviors are explained by a dynamic band alignment between WO_x and ZnO, which can be actively modulated by a gate bias. The performance of FET utilizing the WO_x/ZnO stack is comparable to those of other 2D heterojunction devices; however, it has a unique benefit in terms of process integration because of very low temperature process capability (T < 110 °C). The high on/off switching with extremely low off current density utilizing the dynamic band alignment modulation at the WO_x/ZnO stack can be a very useful element for future device applications, especially in monolithic 3D integration or flexible electronics.