Abnormal High Resistive State Current Mechanism Transformation in Ti/HfO2/TiN Resistive Random Access Memory

In this letter, the electrical characteristics of Ti/HfO2/TiN resistive random access memory (RRAM) were thoroughly investigated. An abnormal current degradation was seen in the DC sweeping cycle. Both the on-state and off-state current clearly exhibited degradation with time. Next, current fitting analysis was used to investigate the carrier transport mechanisms. The results indicate that the on-state carrier transport mechanism changed from space-charge-limited current into hopping conduction after cycle sweeping. However, the off-state current changes from Schottky thermal emission to hopping conduction. Based on comparisons of different Schottky distances and Schottky barriers, physical models were proposed to explain the abnormal current degradation behavior. Finally, COMSOL electric field simulations were used to show the electric field distribution around the conducting filament (CF), and the conducting model was subsequently verified.