High　quality　single　crystalline　n-type　ZnO　film　was　grown　on　p-type　GaN　substrate　using　molecular　beam　epitaxy.　Transmission　electron　microscopy　reveals　a　sharp　ZnO/GaN　interface.　Light-emitting　diode　was　fabricated　from　this　heterostructure,　and　a　turn-on　voltage　of　similar　to　3.4　V　was　demonstrated.　We　found　that　the　emission　peak　shifts　from　violet　(430　nm)　to　near-ultraviolet　(375　nm)　when　the　driving　current　increases　from　0.38　mA　to　3.08　mA.　This　intriguing　phenomenon　can　be　understood　by　charged　carrier＇s　radical　recombination　occurring　at　both　sides　of　the　device,　and　the　current　enhancement　of　ZnO　emission　efficiency.　(C)　2011　Elsevier　B.V.　All　rights　reserved.