Line and point defect reductions in thin GaN epilayers with single and double in situ SiNx nanonetworks on sapphire substrates grown by metal-organic chemical vapor deposition were studied by deep-level transient spectroscopy (DLTS), augmented by x-ray diffraction (XRD), and low temperature photoluminescence (PL). All samples measured by DLTS in the temperature range from 80 to 400 K exhibited trap A (peak at ∼ 325 K) with an activation energy of 0.55–0.58 eV, and trap B (peak at ∼ 155 K) with an activation energy of 0.21–0.28 eV. The concentrations of both traps were much lower for layers with SiNx nanonetwork compared to the reference sample. The lowest concentration was achieved for the sample with 6 min deposition SiNx nanonetwork, which was also lower than that for a sample prepared by conventional epitaxial lateral overgrowth. In concert with the DLTS results, PL and XRD linewidths were reduced for the samples with SiNx network indicating improved material quality. Consistent trend among optical, structural, and DLTS results suggests that SiNx network can effectively reduce both point and line defects.