The　defect　characteristics　of　ZnO　film　grown　on　(0　0　0　1)　sapphire　substrate　using　an　ultrathin　Ga　wetting　layer　are　investigated　by　transmission　electron　microscopy　and　X-ray　diffractometry　compared　to　that　of　the　ZnO　film　without　Ga.　It　was　found　that　the　defects　of　the　ZnO　film　with　a　Ga　layer　were　prominently　reduced　and　a　high-quality　film　was　formed.　Within　this　ZnO　film,　most　defects　near　the　interface　are　mixed-type　dislocations　that　interact　strongly,　leading　to　a　remarkable　reduction　of　dislocations　in　the　upper　part　of　the　epitaxial　film　with　a　total　dislocation　density　of　as　low　as　8　x　10(8)　cm(-2).　Almost　no　pure　screw　dislocations　were　observed.　Furthermore,　the　film　exhibits　a　single　domain　structure,　and　no　inversed　domains　were　found.　The　role　of　the　ultrathin　gallium　layer　in　the　defect　reduction　and　inversion　domain　suppression　is　discussed.　(C)　2004　Elsevier　B.V.　All　rights　reserved.