Crystallographic orientation-dependent resistive switching devices based on hybrid Ga₂O₃ thin films

Resistive random-access memories (RRAMs) based on wide-bandgap oxides are not only a promising candidate for next-generation non-volatile storage technology but also a suitable family of materials capable of neural network computing. However, the exact mechanism of resistive switching (RS) is not yet clearly understood. In this paper, two typical sandwich structures of Ga2O3-based RRAMs were investigated to understand the microscopic-level RS behavior and its relation to the actual process. The results showed that the oxygenation process during magnetron sputtering affected the crystallization orientation of Ga2O3 thin films. The crystalline orientation of Ga2O3 films deposited with O-2 flow was [006], and the prepared devices exhibited a lower operating voltage, a higher high/low resistance state ratio, and a more concentrated distribution. By the climbing image nudged elastic band (CI-NEB) method, the oxygen vacancies of the [006] crystalline Ga2O3 films only needed to migrate in the (110) plane to form conductive filaments with an energy barrier of 0.65 eV. In contrast, [122] crystalline Ga2O3 films required additional movement in the Z-axis direction, resulting in a much higher energy barrier. This work demonstrated that the crystallographic orientation significantly affected the performance of Ga2O3-based RRAMs and provided new insights into the oxygen vacancy migration paths and associated migration energy barriers of hybrid Ga2O3 thin films.