Memory-State Dependence of Random Telegraph Noise of $\hbox {Ta}_{2}\hbox {O}_{5}/\hbox {TiO}_{2}$ Stack ReRAM

Memory-state [low-resistance state (R_L) and high-resistance state (R_H)] dependence of random telegraph noise (RTN) of Ta₂O₅/TiO₂ resistive random access memory is investigated. The conduction mechanism of both memory states and a limit of resistance controllability are also investigated to clarify the difference in the RTN mechanism of both states. The boundary between the R_L and R_H states was found at 5-20 kΩ , and the conduction mechanism much depended on the memory state. The noise also depended on the memory state. The noise amplitude in the R_H state was larger than that in the R_L state. In the R_H state, a tunnel barrier was generated to cut off a conduction path (filament), and traps inside the tunnel barrier were supposed to increase the noise amplitude. Moreover, the composition of the following degraded the noise distribution in the R_H state: 1) capture and emission of charges with traps and 2) instability of these traps against the bias temperature stress.