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 the I-V curves of the self-rectifying n⁺Si-HfO₂-Ni resistance random access memory (RRAM) have been measured systematically. The complementary nonrectifying p⁺Si-HfO₂-Ni RRAM I-V data are also provided for reference. To explain all experimental data, three resistances in series in the RRAM device: 1) the Si-HfO₂ contact resistance R_Si-HfO; 2) the HfO₂ dielectric resistance R_HfO; and 3) the HfO₂-Ni contact resistance R_HfO-Ni must be considered on an equal footing. Previously reported first principle calculation results for the density of states of the monoclinic HfO₂ grain boundary with high and low densities of oxygen vacancyV_O⁰ are adopted for describing the conductive filament resistance R_HfO of the dielectric at low- and high-resistance states. The temperature dependence of I-V is controlled by three different energy barriers: Schottky-like barrier, multiphonon trap assisted tunneling barrier, and multiphonon deep trap capture barrier (E_CAPTURE). 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.