Improvement of light extraction of GaN by using FCVA-deposited TiO₂ conformal layers and self-assembled nanosphere

This study developed a light extraction enhancement method for gallium nitride (GaN) scintillators by integrating microsphere self-assembly technology with filter cathode vacuum arc deposition (FCVA) deposition technology. As a representative third-generation wide-bandgap semiconductor, GaN exhibits excellent radiation resistance and superior optical properties, with its 8-inch wafer fabrication capability providing a critical foundation for large-area imaging applications. To address the light extraction limitations imposed by the high refractive index of GaN, we designed a photonic crystal structure: an array of polystyrene microspheres with a 600-nanometer periodicity, combined with a conformal TiO₂ layer deposited via FCVA. Experimental results demonstrate significant enhancement: after angular integration, the integrated spectral intensity of the yellow emission band increased by 197% (100 nm TiO₂) and 136% (50 nm TiO₂), while the near-band-edge emission integrated spectral intensity increased by 83% (100 nm TiO₂) and 70% (50 nm TiO₂). This performance enhancement stems from the synergistic effect between the optical localization effect of the PS microsphere array and the high refractive index (∼2.4) of TiO₂. The FCVA technique, characterized by its high deposition rate (∼10 nm/min) and substantial ion flux, enables rapid fabrication of TiO₂ conformal layers with exceptional large-area uniformity, meeting industrial production requirements. This work establishes a significant technical approach for improving light extraction efficiency in GaN materials, demonstrating promising potential for large-area imaging and related applications.