Swift heavy ion irradiation of gallium nitride: a review of defect dynamics, ion–matter interactions, and property modifications

This review paper analyzes the modifications induced by effects of swift heavy ion (SHI) irradiation on gallium nitride (GaN), emphasizing its structural, optical, and electrical modifications. Recognized for its exceptional semiconducting properties, GaN has become a focal material in radiation environments. SHI irradiation offers a distinct technique for tuning GaN’s properties through controlled defect formation. The review elaborates on the interactions between swift heavy ions and GaN, highlighting key energy loss mechanisms—electronic and nuclear energy losses—that govern the nature and extent of damage. It incorporates theoretical models such as Coulomb explosion, thermal spike, and molecular dynamics simulations to interpret the physical processes underlying defect generation and evolution. The study primarily addresses the role of varying projectile ion masses (A = 7–238), categorized as light (A < 20), medium (20 ≤ A < 50), heavy (50 ≤ A < 150), and super-heavy (A ≥ 150) ions. Irradiation conditions span fluences from 2.5 × 10⁷ to 1 × 1014 ions/cm² and energies between 3 and 2300 MeV. The induced changes in GaN are characterized using techniques such as X-ray diffraction (XRD), Raman, photoluminescence (PL), transmission electron microscopy (TEM), and Hall effect measurements. In addition to mass effects, the influence of ion energy, energy loss parameters such as electronic energy loss (S_e) and nuclear energy loss (S_n), fluence, flux, and post-irradiation annealing is critically reviewed for their cumulative impact on GaN’s behavior. Although challenges remain in fully controlling these irradiation effects, the review outlines potential future research directions, including the extension of SHI studies to other wide bandgap materials such as ZnO, Ga₂O₃, and SiC. In conclusion, the findings underscore the relevance of SHI irradiation as a potent tool for engineering GaN-based materials and devices for emerging applications in next-generation semiconductor technologies.