Crystallographic Orientation-Dependent Resistive Switching in Ga2O3 Thin Films

Abstract

Abstract 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 Ga2O3-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 Ga2O3 thin films. The XRD analysis reveals that the crystalline orientation of Ga2O3 films deposited with O2 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 Ga2O3 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 Ga2O3 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 Ga2O3-based RRAMs.