Crystallographic Orientation-Dependent Resistive Switching in Ga2O3 Thin Films

Resistive random-access memories (RRAMs) based on wide-bandgap oxides is 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, we investigate Ga 2 O 3 -based RRAMs to understand the microscopic-level RS behavior and its relation to the actual process. We find that the oxygenation process during magnetron sputtering affects the crystallization orientation of Ga 2 O 3 thin films. The XRD analysis reveals that the crystalline orientation of Ga 2 O 3 films deposited with O 2 flow is [006], and the prepared devices exhibit a lower operating voltage, a higher high/low resistance state ratio, and a more concentrated distribution. By using first-principles calculations and the climbing image nudged elastic band (CI-NEB) method, we show that the oxygen vacancies of the [006] crystalline Ga 2 O 3 films only need to migrate in the (110) plane to form conductive filaments with an energy barrier of 0.65 eV. In contrast, [122] crystalline Ga 2 O 3 films require additional movement in the Z-axis direction, resulting in a much higher energy barrier. Our results can be utilized to modulate the operating voltage and improve the endurance of Ga 2 O 3 -based RRAMs.