Ab initio insights into radiation-induced defects and band-gap evolution in α-, β-, and κ-Ga2O3

Abstract

The impact of radiation-induced damage on material properties is a critical parameter that determines the performance and reliability of electronic and optoelectronic devices. In this study, using ab initio molecular dynamics (AIMD), we predict threshold displacement energies (E_d) for the three polymorphs (α, β, and κ) of Ga₂O₃. The AIMD-derived E_d values were further used to estimate radiation damage in terms of the number of vacancies generated under irradiation. Our results reveal an increase in O vacancies in Ga₂O₃, which is not captured by the Monte Carlo TRIM code, that exceeds the default E_d. It should be noted that oxygen atoms possess the lowest E_d values (∼25–35 eV), making them the primary contributors to stable defects (i.e., Frenkel pairs), while Ga atoms require significantly higher E_d energies (>35 eV). Among the polymorphs, the α phase exhibits the highest resistance to displacement, while κ is more prone to radiation damage due to weaker bonding. Diverse defect configurations such as Frenkel pairs, multi-vacancy/interstitial complexes, and dumbbell interstitials induce significant band gap modulation and localized states near the Fermi level. These findings underscore the critical role of the type of defects, lattice sites, and orientation in tuning the electronic structure behavior of Ga₂O₃ under irradiation.