Transient　temperature　field　of　GaN　films　has　been　analyzed　by　finite　element　method　for　laser　lift-off　(LLO)　technique.　Temperature　distribution　in　GaN　films　irradiated　by　pulse　laser　with　different　energy　density　as　a　function　of　time　and　depth　has　been　simulated.　The　results　show　that　the　high　temperature　region　in　GaN　films　localizes　within　about　70 nm　below　the　GaN/Al2O3　interface.　It　is　also　found　that　the　energy　density　of　the　pulse　laser　should　be　confined　to　a　certain　range　decided　by　the　simulation　to　realize　damage-free　GaN　films　LLO　from　sapphire　substrates.　LLO　experiments　have　also　been　carried　out　using　KrF　excimer　laser　with　248 nm　wavelength　and　30 ns　pulse　width.　GaN　films　are　separated　from　sapphire　substrates　using　the　parameters　obtained　from　the　simulation.　Atomic　force　microscopy,　scanning　electron　microscopy　and　photoluminescence　measurements　show　that　the　surface　morphology　and　optical　characteristic　of　GaN　films　degrade　a　little　after　LLO.　©　2006　Elsevier　B.V.　All　rights　reserved.