Through　comparing　ZnO　directly　grown　on　the　substrates　of　a-plane,　c-plane,　and　(11-22)　plane　GaN　and　AlxGa1-xN　(0.06　＜=　x　＜=　1),　the　roles　of　different　factors　that　may　influence　growth　have　been　studied.　Seeded　by　surface　pits,　ZnO　nanowire　(NW)　preferentially　grew　along　the　polarized　direction　on　top　of　the　nonpolar　GaN　(laterally　aligned),　polar　GaN　and　AlGaN　(vertically　aligned),　and　semipolar　GaN　(obliquely　upward　aligned).　Nanosheets　were　easily　formed　when　the　polarized　surface　of　the　AlGaN　film　was　not　intact.　The　kinetic　effect　of　polarization　must　be　considered　to　explain　the　high　aspect　ratio　of　NWs　along　the　polarized　direction.　It　was　found　that　dislocation　affected　NW　growth　through　the　surface　pits,　which　provided　excellent　nucleation　sites.　If　the　surface　pits　on　GaN　could　be　controlled　to　distribute　uniformly,　self-organized　ZnO　NW　array　could　be　controllably　and　directly　grown　on　GaN.　Moreover,　surface　pits　could　also　seed　for　nanosheet　growth　in　AlN,　since　Al(OH)(4)(-)　would　presumably　bind　to　the　Zn2+　terminated　surface　and　suppress　the　kinetic　effects　of　polarization.