Opposite bias polarity dependence of resistive switching in n-type Ga-doped-ZnO and p-type NiO thin films

A hypothesis based on the model that explains the resistance change effect of resistive random access memory by redox reaction is proposed. This hypothesis leads to the conclusion that the relationship between the polarity of the applied bias voltage and the resultant resistance change in p-type semiconductors is opposite to that for n-type semiconductors. The bias polarity dependence of the resultant resistance change in ZnO and Ga-doped ZnO (GZO), which are n-type semiconductors, and that in NiO, which is a p-type semiconductor, were investigated using conducting atomic force microscopy. Opposite bias polarity was confirmed to induce GZO and NiO into the same resistance state, which is consistent with the hypothesis.