Wurtzite　GaN　and　(Ga,Zn)N　nanocrystals　with　the　size　of　8-20　nm　were　synthesized　by　the　solid-phase　thermal　decomposition　method　at　mild　temperature　of　350-650　C.　This　synthesis　method　is　a　simple　and　low　cost　method.　From　the　further　study　on　the　luminescence　mechanism,　Zn　dopant　introduces　new　energy　levels　in　the　band　gap　of　GaN　nanocrystals,　which　effectively　induces　the　fluorescence　emission　in　the　visible　region.　In　addition,　the　VN-H　defect　significantly　affects　the　optical　properties　of　nanocrystals.　Moreover,　GaN　nanocrystals　with　a　proper　Zn-doping　concentration　will　produce　a　white　light.　©　2013　Elsevier　B.V.　All　rights　reserved.