Two different approaches to epitaxy of 4-μm-thick layers of polar GaN(0001) and semipolar GaN(10 $$\bar {1}$$ 1) on a V -shaped nanostructured Si(100) substrate with nanometer-thick SiC and AlN buffer layers have been experimentally demonstrated. The GaN(0001) layers were synthesized by hydride vapor-phase epitaxy, and GaN(10 $$\bar {1}$$ 1) layers, by metal-organic vapor-phase epitaxy, with the growth completed by hydride vapor-phase epitaxy. It was shown that layers of the polar GaN(0002) have a longitudinal elastic stress of –0.45 GPa and the minimum full width at half-maximum of the X-ray diffraction rocking curve ω_θ ~ 45 arcmin, whereas for the semipolar GaN(10 $$\bar {1}$$ 1), these values are –0.29 GPa and ω_θ ~ 22 arcmin, respectively. A conclusion is drawn that the combined technology of semipolar gallium nitride on a silicon (100) substrate is promising.