Point Defects in Silicon-Doped β-Ga₂O₃: Hybrid-DFT Calculations

In this work, hybrid density functional theory calculations are used to evaluate the structural and electronic properties and formation energies of Si-doped β-Ga₂O₃. Overall, eight interstitial (Si_i) and two substitutional (Si_Ga) positions are considered. In general, our results indicate that the formation energy of such systems is significantly influenced by the charge state of the defect. It is confirmed that it is energetically more favorable for the substitution process to proceed under Ga-poor growth conditions than under Ga-rich growth conditions. Furthermore, it is confirmed that the formation of Si_GaI with a tetrahedral coordination geometry is more favorable than the formation of Si_GaII with an octahedral one. Out of all considered interstitial positions, due to the negative formation energy of the Si +3 charge state at i₈ and i₉ interstitial positions over the wide range of Fermi energy, this type of defect can be spontaneously stable. Finally, due to a local distortion caused by the presence of the interstitial atom as well as its charge state, these systems obtain a spin-polarized ground state with a noticeable magnetic moment.