Physical mechanism of oxygen diffusion in the formation of Ga₂O₃ Ohmic contacts

The formation of low-resistance Ohmic contacts in Ga₂O₃ is crucial for high-performance electronic devices. Conventionally, a titanium/gold (Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulting in mutual diffusion of atoms at the interface. However, the specific role of diffusing elements in Ohmic contact formation remains unclear. In this work, we investigate the contribution of oxygen atom diffusion to the formation of Ohmic contacts in Ga₂O₃. We prepare a Ti/Au electrode on a single crystal substrate and conduct a series of electrical and structural characterizations. Using density functional theory, we construct a model of the interface and calculate the charge density, partial density of states, planar electrostatic potential energy, and I–V characteristics. Our results demonstrate that the oxygen atom diffusion effectively reduces the interface barrier, leading to low-resistance Ohmic contacts in Ga₂O₃. These findings provide valuable insights into the underlying mechanisms of Ohmic contact formation and highlight the importance of considering the oxygen atom diffusion in the design of Ga₂O₃-based electronic devices.