AlN single crystal grown by physical vapor transport (PVT) using homogeneous seed is considered as the most promising approach to obtain high-quality AlN boule. In this work, the morphology of AlN single crystals grown under different modes (3D islands and single spiral center) were investigated. It is proved that, within an optimized thermal distribution chamber system, the surface temperature of AlN seed plays an important role in crystal growth, revealing a direct relationship between growth mode and growth condition. Notably, a high-quality AlN crystal, with (002) and (102) reflection peaks of 65 and 36 arcsec at full width at half maximum (FWHM), was obtained grown under a single spiral center mode. And on which, a high-quality Al_xGa_1–xN epitaxial layer with high Al content (x = 0.54) was also obtained. The FWHMs of (002) and (102) reflection of Al_xGa_1–xN were 202 and 496 arcsec, respectively, which shows superiority over their counterpart grown on SiC or a sapphire substrate.