Deep-level transient spectroscopy measurements were conducted on He-implanted $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ thin films to study the $E_4^{*}$ level, which is a known irradiation-induced defect that is energetically positioned $1.5\mathrm{e}\mathrm{V}$ below the conduction band minimum. We find that the formation of $E_4^{*}$ after implantation is strongly dependent on a reverse-bias annealing step, where the activation energy for the thermally-activated introduction of $E_4^{*}$ is estimated to be $\sim 2.4\mathrm{e}\mathrm{V}$. Contrary to previous reports, we find, for some of the measured diodes, that the level is stable upon subsequent measurements. From first-principles calculations of the intrinsic defects, we find that the properties of the $V_{\text{O1}}$ and $V_{\text{O3}}$ configurations of the oxygen vacancy closely agree with the experimental observations for the $E_4^{*}$ level. A model is suggested where the reverse bias lowers the Fermi-level position in the depletion region of the diode and changes the relative formation energies of the possible configurations of the oxygen vacancy; the formation of $E_4^{*}$ then results from an increase in the relative stability of the O1 and O3 configurations of $V_{\mathrm{O}}$.

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• Defects
• Point defects
• Schottky barriers
• Wide band gap systems
• Annealing
• Deep level transient spectroscopy
• Density functional theory
• Ion implantation
• Irradiation