- We have demonstrated that GaN can be grown epitaxially by atmospheric pressure metalorganic chemical vapor deposition on an aluminum oxide compound layer utilized as an intermediate layer between GaN and a Si(111). X-ray diffraction measurement indicates that single-crystal hexagonal GaN with its basal plane parallel to the Si(111) plane is grown. Using a scanning electron microscope, the macroscopic evolution of GaN grown on the AlOx/Si(111) substrate is found to be similar to that of GaN grown on a sapphire(0001) substrate. Cathodoluminescence (CL) spectrum shows a unique emission that consists of several peaks with the intensity comparable to that of the near-band-edge emission. Unique characteristics in CL spectrum are discussed in terms of a possible oxygen contamination of GaN grown on the AlOx/Si(111) substrate.