Investigations of Conduction Mechanisms of the Self-Rectifying n⁺Si-HfO₂–Ni RRAM Devices

The area, temperature (160–300 K), and bias polarity dependences of theI–Vcurves of the self-rectifying n+Si-HfO2–Ni resistance random access memory (RRAM) have been measured systematically. The complementary nonrectifying p+Si-HfO2–Ni RRAMI–Vdata are also provided for reference. To explain all experimental data, three resistances in series in the RRAM device: 1) the Si-HfO2contact resistanceR\(Si-HfO\); 2) the HfO2dielectric resistanceRHfO; and 3) the HfO2–\(Ni\)contact resistanceRHfO-Nimust be considered on an equal footing. Previously reported first principle calculation results for the density of states of the monoclinic HfO2grain boundary with high and low densities of oxygen vacancyV\(O⁰\)are adopted for describing the conductive filament resistanceRHfOof the dielectric at low- and high-resistance states. The temperature dependence ofI–Vis controlled by three different energy barriers: Schottky-like barrier, multiphonon trap assisted tunneling barrier, and multiphonon deep trap capture barrier (ECAPTURE). It is demonstrated that all experimental data can be explained in a natural and unified way. This model is valuable not only for understanding the conduction mechanism, but also for guiding the future self-rectifying RRAM technology development.