c-plane (0001) AlN layers were grown on sapphire (11-20) and (0001) substrates by hydride vapor phase epitaxy (HVPE) and metal-organic vapor phase epitaxy (MOVPE), respectively. The growth temperatures were adjusted from 1430-1500 °C and the reactor pressure was kept constant at 30 Torr. Mirror and flat c-plane AlN were obtained grown on both a-plane and c-plane sapphire. Crystalline quality and surface roughness are improved with increasing growth temperature, detected by high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM). The Full widths at half maximum (FWHM) values of (10-12) diffraction are 519 and 1219 arcsec for c-plane AlN grown on a-plane sapphire and c-plane sapphire, respectively. It indicates that a-plane sapphire substrate benefits to decrease dislocations density.