Multilevel oxygen-vacancy conductive filaments in β-Ga2O3 based resistive random access memory

Abstract

β-Ga₂O₃ has recently attracted considerable attention for its application in resistive switching memory. However, the resistive behaviors and mechanisms of β-Ga₂O₃ memory dominated by the oxygen-vacancy (V_O) still remain controversial. In this study, we systemically investigated the formation process of V_O conductive filaments in β-Ga₂O₃ memory. There were at least three kinds of V_Os and conductive filaments with different low resistance states (LRSs) in β-Ga₂O₃ memory, suggesting their potential for multilevel storage application. Interestingly, these conductive filaments preferred to be formed along the [010] direction and with a single V_O cluster rather than a mixed V_O cluster due to the lower single V_O cluster formation energy and ellipsoid charge distribution. The lowest migration and activation barriers for different kinds of V_Os in +2 charge states (V²⁺_Os) were discrepant and lower than the neutral charge states. Meanwhile, the forward migration energy of V_O was different from the reversed migration path, so that the conductive filament formation and rupture were not an inverse process in the experiment. The detailed mechanisms were revealed by the charge density and migration process of these V_Os. These results not only revealed the function of the V_O conductive filaments in β-Ga₂O₃ memory but also predicted the potential of β-Ga₂O₃ memory for multilevel storage application.