A possibility is shown to use substrates with column structure for the growth of thick GaN epitaxial layers with reduced levels of thermoelastic stress and structural defects. A detailed characterization of ~600 µm-thick GaN layers was performed using transmission electron microscopy and optical methods, namely, Raman spectroscopy and photoluminescence. The obtained results showed that the grown material had excellent quality with high uniformity of parameters across the surface of the layers.