GaN-based　high-power　laser　diodes　(LDs)　have　attracted　tremendous　interests　in　next-generation　lighting　applications,　such　as　laser　display,　car　laser　light.　However,　high　injection　current　usually　brings　inevitable　drawbacks,　including　the　well-known　efficiency　droop,　Auger　recombination　and　self-heating　which　obstruct　further　improvements　of　GaN-based　optoelectrical　devices.　In　this　paper,　influence　of　hole　overflow　at　high　injection　current　in　an　asymmetric　GaN-based　high-power　blue　LD　has　been　comprehensively　investigated　and　successfully　suppressed　by　employing　a　new　sandwiched　GaN/AlGaN/GaN　lower　quantum　barrier　(GAG-LQB).　Systematical　simulations　and　measurements　of　structural　and　optical　properties　are　carried　out.　As　a　result,　the　V-shaped　defects　induced　by　thick　n-InGaN　waveguide　layer　are　apparently　eliminated,　which　provides　a　more　growth-friendly　platform　for　deposition　of　the　rest　epitaxial　layers　and　thus　a　better　crystalline　quality　is　obtained.　On　the　other　hand,　the　modified　LD　exhibits　better　photo-electrical　properties　with　slope　efficiency　(SE)　increasing　from　0.98　to　1.24　and　wall-plug　efficiency　(WPE)　increasing　from　18.7%　to　20.5%　at　a　high　current　of　1.5　A　and　no　obvious　efficiency　droop　is　observed　at　a　current　as　high　as　2　A　compared　with　the　conventional　one,　because　the　middle-inserted　AlGaN　layer　could　form　an　extra　barrier　on　the　valence　band　to　weaken　the　hole　overflow　and　enhance　the　radiative　recombination.　Furthermore,　the　in-plane　compressive　strain　induced　by　InGaN　quantum　wells　(QWs)　is　also　partially　compensated　by　the　tensile　strain　induced　by　the　AlGaN　layer.　Therefore,　the　piezoelectric　field-induced　polarization　is　effectively　alleviated　and　the　wavelength　blueshift　is　reduced　from　7　nm　to　1.6　nm.