Percolation-driven bandgap narrowing and magnetic ordering in Ni<b>++</b>-implanted GaN

Ion implantation introduces structural disorder in semiconductors, yet a predictive framework linking implantation parameters to phase transitions remains lacking. In this work, we investigate the emergence of a percolation-driven mechanism underlying bandgap narrowing and magnetic ordering in Ni-implanted GaN. Monte Carlo simulations of defect transport reveal that the bandgap reduction follows a nonlinear scaling law governed by Coulombic screening, defect hybridization, and strain accumulation. Concurrently, magnetization evolves from localized superexchange interactions to conduction-mediated RKKY coupling beyond a critical defect density. Experimental validation confirms the predicted trends in bandgap renormalization and magnetic hysteresis across varying ion fluences.