Library of intrinsic defects in β-Ga₂O₃: First-principles studies

Gallium sesquioxide (β-Ga₂O₃) acts as a prime candidate for next-generation power electronics, of which complex defects largely impact its electrical performances and limit its practical applications. Herein, using the first-principles method, various intrinsic defects (63 in total) are systematically investigated, including point defects and complexes, of which properties involve formation energies, transition levels, binding energies, etc. It is demonstrated that most defects are likely easier to form under Ga-rich chemical conditions, in which V_O, Ga_i, Ga_O, O_Ga-Ga_O, O_i-Ga_O, and Ga_O-V_Ga defects are metastable to be probably detected in the experiment. Combing with deep-level transient spectroscopy (DLTS) experiments, it is preferred that O_Ga-V_GaI(4-/6-) are related to the unknown experimental level E_C-0.12–0.28 eV; Ga_i(+3/+1), Ga_OII(+3/+1) or O_i-Ga_OIII(+3/+1) are related to the level E_C-0.74–0.82 eV; Ga_OIII(+3/+1), O_i-Ga_OI(+3/+1), O_i-Ga_OII(+3/+1) or O_Ga-Ga_OII(+2/0) are related to the level E_C-0.95–1.1 eV; V_OIII(+2/0), Ga_O-V_GaII(+2/0) or O_Ga-Ga_OI(+2/0) are associated with level E_C-1.2–1.48 eV; V_OI(+2/0), O_Ga-V_OI(1-/3-) or O_Ga-V_OII(1-/3-) are associated with level E_C-2.0–2.3 eV; O_Ga-V_OII(+3/+2) is associated with level E_C-4.37–4.38 eV. Although the uncertainty of the consistency between our theoretical predictions and experiments always remains due to the complex atomic structure and low symmetry, our findings provide a near-complete database in combination with experimental observations to define and identify defects in β-Ga₂O₃, which has a profound impact on understanding the radiation damage and degradation of β-Ga₂O₃ devices.