Luminescence mechanism of prismatic stacking faults in homoepitaxial AlN

A fundamental understanding of the correlation between the microstructure and luminescence properties is critical to advancing deep-ultraviolet optoelectronic applications of aluminum nitride (AlN). Here, we report the first observation and elucidation of hexagonal domain boundaries exhibiting green cathodoluminescence in homoepitaxial AlN. These boundaries consist of prismatic stacking faults (PSFs), which project as 4|8-membered ring chains on the (0001) plane and interconnect via deformed 8-membered rings forming stable 120° junctions. The negative formation energy of these PSF junctions confirms their thermodynamic stability. Atom probe tomography identifies oxygen at the boundary, consistent with a calculated segregation energy of −0.63 eV/atom for ON at PSFs. Partial density of states analysis further reveals that oxygen induces deep in-gap states exclusively within the PSF configuration. This work identifies the oxygen-decorated PSF as a defect-impurity complex responsible for the green cathodoluminescence, suggesting a promising pathway toward transforming defects into tailored optical emitters in wide-bandgap nitrides.