Bidirectional highly nonlinear analog memristor based on band-to-band tunneling for reliable crossbar array operation

To fully utilize the advantages of memristor crossbar array, it is required to overcome the nonidealities during the operations, which are unintended voltage drops at unselected cells and lines during the write operation and leakage current through neighboring cells during the read operation. In this study, an analog-type memristor with Pt/p-NiO/n-ZnO/p-NiO/Pt structure with bidirectional nonlinear current-voltage (I–V) characteristics is investigated to mitigate these issues. Nonlinear I–V characteristics for selector-less operations in array architecture were attained by band-to-band tunneling current at p-NiO/n-ZnO/p-NiO heterojunctions. Analog conductance changes of around two orders of magnitude were attained by the modulation of turn-on voltage for the band-to-band tunneling through oxygen ions migration in these layers. Calculation of write voltage window and read margin confirmed that bidirectional highly nonlinear I–V characteristics of memristor could effectively prevent nonidealities during operation, suggesting a reliable selector-less memristor for crossbar array operation.