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In the rapidly evolving field of quantum computing, niobium nitride (NbN) superconductors have emerged as integral components due to their unique structural properties, including a high superconducting transition temperature (Tc), exceptional electrical conductivity, and compatibility with advanced device architectures. This study investigates the impact of high-temperature annealing and high-dose gamma irradiation on the structural, electrical, and superconducting properties of NbN films grown on GaN via reactive DC magnetron sputtering. The as-deposited cubic δ-NbN (111) films exhibited a high intensity distinct x-ray diffraction (XRD) peak, a high Tc of 12.82 K, and an atomically flat surface. Annealing at 500 and 950 °C for varying durations revealed notable structural and surface changes. High-resolution scanning transmission electron microscopy (STEM) indicated improved local ordering, while atomic force microscopy showed reduced surface roughness after annealing. X-ray photoelectron spectroscopy revealed a gradual increase in the Nb/N ratio with higher annealing temperatures and durations. High-resolution XRD and STEM analyses showed lattice constant modifications in δ-NbN films, attributed to residual stress changes following annealing. Additionally, XRD φ-scans revealed a sixfold symmetry in the NbN films due to rotational domains relative to GaN. While Tc remained stable after annealing at 500 °C, increasing the annealing temperature to 950 °C degraded Tc to 8.7 K and reduced the residual resistivity ratio from 0.85 in the as-deposited films to 0.29 after 30 min annealing. The effects of high-dose gamma radiation [5 Mrad (Si)] were also studied, demonstrating minimal changes to crystallinity and superconducting performance, indicating excellent radiation resilience. These findings highlight the potential of NbN superconductors for integration into advanced quantum devices and its suitability for applications in radiation-intensive environments such as space, satellites, and nuclear power plants.