In this work, we report on the results of structural characterization of α- and β-Ga2O3 layers grown on various substrates: Al2O3, AlN/Al2O3 and AlN by halide vapor phase epitaxy. Scanning electron microscopy analysis is used to control the thickness of the Ga2O3 layers. The maximum achieved thickness is 46 µm, this is for α-Ga2O3 grown on the bulk AlN substrate. X-ray analysis is used to find the crystallographic orientation of the layers and to characterize the structure quality of the samples. Measured full-width at highmaximum of rocking curves of 15' and 56' confirms crystal quality of the grown α-Ga2O3 and β-Ga2O3 layers on AlN and AlN/Al2O3 substrates, correspondingly. Using AlN as substrate material or buffer AlN layer leads to an increase of Ga2O3 layer thickness and crystal quality in comparison to the layers grown on Al2O3 substrate.