Periodic SiNx interlayers were employed during the metal-organic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111) substrates. The growth and the evolution of defects were studied in this paper. A reduction of the threading dislocation density to ∼109 cm-2 was observed on the surface of GaN by counting the surface pit density from the atomic force microscopy results. Besides the observation of the continuous bending and subsequent recombination of the threading dislocations related to the periodic conduction of the SiNx interlayer characterized using cross-sectional transmission electron microscopy, we observed a different behavior induced by the SiNx interlayers: Si-rich inverted hexagonal pyramids with their base on the (0001) plane and six sidewalls on the (1011) plane were found near the top surface of the GaN film at the location of SiNx insertion layer characterized using electron energy loss spectroscopy. The preferential deposition of the SiNx on the sidewalls of the pit defects leads to the subsequently selective growth of the GaN beyond the pit defects, which leads to the burying of the pits and the reduction of the pit defects within the film due to the micromasking effect of the SiNx.