Defect Engineering of Nitrogen Vacancies in Sputtered AlN Thin Films: The Roles of Gas Stoichiometry and Thermal Annealing

Abstract Aluminum nitride is a vital wide-bandgap semiconductor for deep-ultraviolet optoelectronics, yet the deterministic control of its intrinsic defects remains a challenge for sputtered films. In this work, (002)-oriented AlN thin films were synthesized on silicon substrates via radio-frequency reactive magnetron sputtering at a low temperature of 300 °C. The resulting films exhibited high crystallinity, dense nanocrystalline morphology, and superior optical transparency with a characteristic absorption edge below 250 nm. A prominent photoluminescence emission centered at 410 nm was identified and attributed to nitrogen vacancy related centers. Our results demonstrate that the PL intensity and defect dynamics can be effectively modulated by tuning the Ar:N2 flow ratio and post-deposition annealing. Specifically, complementary X-ray photoelectron spectroscopy and electron spin resonance analyses provide direct evidence correlating the processing parameters with nitrogen vacancy concentration and luminescence behavior. This study establishes a robust framework for controllable defect engineering in AlN thin films, highlighting their potential for advanced DUV and high-power electronic applications.