Conduction mechanism of self-rectifying n + Si-HfO 2 -Ni RRAM

Comprehensive experimental I–V data for the self-rectifying n + Si-HfO 2 -Ni RRAMs in the temperature range 160–300K are provided. By analyzing these data, the following conclusions are obtained: (1) the current in the initial state (I) of the fresh devices before forming process is conducted uniformly through the whole cross section area of the dielectric rod, while the low resistance state (LR) current after set process and the high resistance state (HR) current after reset process are conducted through conduction filament (CF) in the dielectric, in average in few of 10 4 µm 2 per CF. (2) The LR current has a high current component appeared only when V>+0.6V, with ohmic like I–V relationship and weak temperature dependence, mainly reflecting the self-rectifying property of the RRAM. All other low current LR component and HR currents appear at both bias polarity and are highly temperature dependent with activation energy E a . There are three different kinds of barriers causing the temperature dependence of LR and HR currents, and the rectifying property of LR. The Schottky like barrier between the electrode and dielectric, the multi phonon trap assisted tunneling barrier between trap to electrode and trap to trap respectively, and the Si to deep trap capture barrier through multi phonon emission. (3) Using the recently reported density of states results of HfO 2 grain boundary associated with high and low concentrations of oxygen vacancy V O 0 , and different kind of barriers stated in (2), all experimental data are explained in a natural and unified way.