Computational study and ion diffusion analyses of native defects and indium alloying in β-Ga2O3 structures

Wide band gap semiconductors like gallium oxide are promising materials for high-power optoelectronic device applications. We show here a combined density functional theory and molecular dynamics study of diffusion pathways for different defects in β-Ga2O3. Molecular dynamics simulations result in a smaller equilibrium volume compared to density functional theory, but the overall lattice remains relatively unchanged even with the inclusion of defects, outside of the local distortions that occur to accommodate the presence of a defect. Slight thermal expansion occurs with elevated temperature and a combination of electron localization function and Bader charge analysis reveals that the oxygen interstitial is the most mobile defect as temperature is increased. However, interstitial cations may diffuse at elevated temperature due to a relatively small amount of charge transfer between the defect and lattice. The mobile oxygen defects are shown to increase the mobility of oxygen ions from the lattice, which can be beneficial for electrochemical applications when controlled through annealing processes.