The growth of a thick AlGaN is performed on Al 2 O 3 substrate by metalorganic vapor phase epitaxyhydride vapor phase epitaxy (MOVPE-HVPE) combined system. Thin AlN or GaN layer is grown on a substrate by MOVPE growth method with the conventional manner but in a hot-wall chamber and followed by the HVPE growth of a thick AlGaN in the same chamber. For the growth of a AlGaN layer, NH 3 and aluminum-gallium chloride formed by HCl which is flown over metallic Ga mixed with Al are used as aluminum-gallium and nitrogen sources. The peak of the cathodoluminescence (CL) spectrum of the thick AlGaN is shown at the wavelength of 354 nm. This suggests that the metallic Ga mixed with Al can be used as a group III source material in the HVPE growth of the AlGaN.