Negative Pulse and Compliance Current Dependent Negative Differential Resistance in ZnO/Nb:SrTiO3 Heterojunctions

The negative differential resistance (NDR) in ZnO/Nb:SrTiO3 heterojunctions is found to be strongly dependent on negative pulse amplitude/width and compliance current. When a small or short negative pulse is applied, the NDR feature remains almost the same. With the negative pulse amplitude or width increasing, the NDR feature gradually fades down and shifts to a larger negative bias. Meanwhile, the NDR intensity increases markedly without significant shift with increase of the compliance current. Interestingly, the low-resistance state and NDR location are found to exhibit exactly the same trend when varying the negative pulse amplitude, width, and compliance current. The dependence of the NDR intensity and location on the pulse amplitude/width and compliance current can be well understood from the variance of concentration of ionized oxygen vacancies and the depletion layer width, respectively. This will promote the application of NDR devices.