Due　to　the　lateral　current　transport　in　the　mesa-structure　GaN　based　LEDs,the　resistance　of　the　n-type　material　of　the　GaN　and　lower　confinement　layer　is　not　negligible　for　large　area　and　high　applied　current　density　applications,　which　causes　the　current　spreading　nonuniformly　along　the　lateral　direction.　With　an　optimized　contact　scheme　to　reduce　the　length　for　the　lateral　current　transport,　two　different　kinds　of　contact　schemes　of　high-power　GaN-based　flip-chip　LEDs　(FCLEDs)　are　fabricated.　It　is　shown　that　the　forward　voltage　of　this　FCLEDs　with　interdigitated　contact　scheme　is　3.　35　V　at　forward　current　350　mA,　and　exceeds　that　of　FCLEDs　with　optimized　ring-shaped　interdigitated　contact　scheme　by　0.　15　V.　Although　the　light　emitting　area　of　FCLEDs　with　optimized　ring-shaped　interdigitated　contact　scheme　is　slightly　smaller　than　that　of　FCLEDs　with　interdigitated　contact　scheme,　it　is　found　that　the　light　output　from　the　former　is　larger　than　that　from　the　later　at　higher　injection　currents.　Furthermore,　the　light　output　from　the　FCLEDs　with　optimized　ring-shaped　interdigitated　contact　scheme　saturates　slowly　at　higher　injection　currents　as　compared　to　the　FCLEDs　with　interdigitated　contact　scheme,　indicating　that　the　saturation　behavior　of　the　FCLEDs　with　interdigitated　contact　scheme　is　more　pronounced.　It　is　confirmed　that　an　optimized　contact　scheme,　which　leads　to　the　more　uniform　current　spreading,　can　decrease　joule　heat　generated　and　considerably　improve　the　electrical　and　optical　characteristics　of　the　FCLEDs.