The　effect　of　KrF　excimer　laser　irradiation　on　the　optical　and　electrical　properties　of　epitaxial　wafers　with　a　p-GaN　surface　were　investigated　at　different　laser　energy　densities　and　pulse　numbers.　The　laser-irradiated　samples　were　annealed　in　oxygen.　The　laser　irradiation-induced　changes　in　optical　and　electrical　properties　of　GaN　epitaxial　wafers　were　examined　using　PL,　I-V,　XPS,　SIMS,　and　Hall　effect　measurements.　Experimental　results　show　that　under　an　appropriate　laser-irradiated　condition,　optical　and　electrical　properties　of　the　samples　were　improved　to　different　degrees.　The　samples　which　were　annealed　after　laser　irradiation　have　better　electrical　properties　such　as　the　hole　concentration　and　sheet　resistance　than　those　without　annealing.　We　hypothesize　that　the　pulsed　KrF　excimer　laser　irradiation　dissociates　the　Mg-H　complexes　and　annealing　treatment　allows　the　hydrogen　to　diffuse　out　more　completely　under　the　oxygen　atmosphere　at　a　proper　temperature,　by　which　the　crystalline　symmetry　of　GaN　is　improved.　Under　appropriate　laser　conditions　and　O-2-activated　annealing,　the　light　output　of　the　laser-irradiated　GaN-based　LED　sample　is　about　1.44　times　that　of　a　conventional　LED　at　20　mA.　It　is　found　that　the　wall-plug　efficiency　is　10%　higher　at　20　mA　and　the　reverse　leakage　current　is　80%　lower　at　5　V.