Orthorhombic　tantalum　pentoxide　(beta-Ta2O5)　monocrystalline　films　were　deposited　on　epi-GaN/alpha-Al2O3　(0001)　substrates　using　the　metal-organic　chemical　vapor　deposition　method.　The　prepared　films　were　grown　along　the　beta-Ta2O5　(001)　plane.　The　film　deposited　at　850　?C　exhibited　the　best　crystalline　quality　and　the　corresponding　FWHM　of　the　XRD　w-rocking　curve　for　beta-Ta2O5　(001)　plane　was　1.81?.　The　prepared　beta-Ta2O5　film　possessed　a　domain　structure,　and　the　growth　mechanism　was　studied　in　detail.　By　the　XRD　0　scan　and　HRTEM　analyses,　the　in-plane　epitaxial　relationship　of　the　850　?C-prepared　sample　was　determined　as　beta-Ta2O5　[100]　?　GaN　[1　over　bar　100].　The　elemental　composition　and　valence　states　were　studied　and　the　band　gap　of　the　film　prepared　at　850　?C　was　calculated　to　be　4.34　eV　by　the　analysis　of　the　electron　energy　loss　spectrum.