【Member Papers】Orientation-dependent surface radiation damage in β-Ga₂O₃ explored by atomistic simulations

      Researchers from the Wuhan University and Southern University of Science and Technology have published a paper titled “Orientation-dependent surface radiation damage in β-Ga₂O₃ explored by atomistic simulations” in Acta Materialia.

Background

      The β-phase of gallium oxide (β-Ga₂O₃) possesses an ultrawide bandgap of ∼ 4.9 eV, a high breakdown electric field (8 MV/cm), and high radiation hardness. Its excellent radiation resistance allows β-Ga₂O₃ to maintain the desirable structure and electrical properties under harsh radiation environments, providing significant applications in aerospace and nuclear fields. The incidence of highly energetic particles (such as neutron, electron, proton etc.) on β-Ga₂O₃ can cause primary radiation damage as point defects. Previous studies have extensively researched the growth of the four surface orientations (100), (010), (001) and ((01) of β-Ga₂O₃, highlighting their distinct characteristics. However, the radiation damage in extreme environments has not yet been reported. The insightful understanding of primary radiation damage on different β-Ga₂O₃ surfaces can facilitate the more effective design of radiation-resistant devices.

Abstract

      Ultrawide bandgap semiconductor β-Ga₂O₃ holds extensive potential for applications in high-radiation environments. One of the primary challenges in its practical application is unveiling the mechanisms of surface irradiation damage under extreme conditions. In this study, we investigate the orientation-dependent mechanisms of primary radiation damage on four experimentally relevant β-Ga₂O₃ surface orientations, namely, (100), (010), (001), and (01), at various temperatures. An atomistic simulation with machine-learning-driven molecular dynamics (ML-MD) simulations and density functional theory (DFT) calculations are employed. The results reveal that Ga vacancies and O interstitials are the predominant defects across all four surfaces, with the formation of many antisite defects Ga_O and few O_Ga observed. In the case of the two Ga sites and three O sites, the vacancy found in the O2 site is dominant, while the interstitials in Ga1 and O1 sites are more significant. Interestingly, the (010) surface exhibits the lowest defect density, owing to its more profound channeling effect leading to a broader spread of defects. The influence of temperature on surface irradiation damage of β-Ga₂O₃ should be evaluated based on the unique crystal surface characteristics. Comprehending surface irradiation damage at the atomic level is crucial for assessing the irradiation tolerance and predicting the performance changes of β-Ga₂O₃-based device in irradiated environments.

Conclusion

      In this work, the radiation damage mechanism of four surfaces (100), (010), (001), and (01) of β-Ga₂O₃ at different temperatures of 173 K, 300 K, and 500 K was investigated by ML-MD simulation and DFT calculation. The results indicate that following cascade collisions, the predominant defects of radiation damage on the four surfaces are Ga vacancies and O interstitials, with a propensity for the formation of antisite defect Ga_O. Analysis of two Ga sites and three O sites across different surfaces reveals that the predominant intrinsic defects vary by surface. In the specific lattice occupation of β-Ga₂O₃, O2 site exhibits the highest concentration of oxygen atom. The Ga1 and O1 sites have the highest concentration of interstitial atoms in Ga and O occupations, respectively. Ga_O1 is the most likely antisite defect site. Due to the significant channel effect, the (010) surface displays an extensive defect distribution and results in minimal defect generation. The impact of temperature on the defect in radiation damage should be considered with surface orientation. This finding is crucial for the judicious selection of applications for β-Ga₂O₃-based devices.

Fig. 1. (a) The atomic structure of β-Ga₂O₃ and surface orientations. (b) The side view of surface (100) B.

Fig. 2. (a) Orientation-dependent defect distribution of β-Ga2O3 after collision cascade with 1.5 keV irradiation at 300 K is shown. Red lines represent ion motion trajectories. (b) Statistical count point defects across surfaces at 173 K, 300 K, and 500 K, respectively. Error bars indicate standard error.

Fig. 3. (a) Orientation-dependent GaO (cyan) and OGa (orange) antisite defect distribution of β-Ga2O3 after collision cascade at 300 K is shown. (b) Statistical count of antisite defects across surfaces at 173 K, 300 K, and 500 K, respectively. Error bars show standard deviations.

Fig. 4. Snapshots of the antisite defect GaO and OGa formation from (a, c) the initial states to (b, d) the final states during cascade simulations.

 

DOI：

doi.org/10.1016/j.actamat.2025.121484