Effect of packing density and packing geometry on light extraction of Ⅲ-nitride light-emitting diodes with microsphere arrays

Thefinite-differencetime-domainmethodwasemployedtocalculatelightextractionefficiencyofthin-filmflip-chipInGaN/GaNquantumwelllight-emittingdiodes（LEDs）withTiO2microspherearrays.TheextractionefficiencyforLEDswithmicrospherearrayswasinvestigatedbyfocusingontheeffectofthepackingdensity,packingconfiguration,anddiameter-to-periodratio.Thecomparisonstudiesrevealedtheimportanceofhavingahexagonalandclose-packedmonolayermicrospherearrayconfigurationforachievingoptimumextractionefficiency,whichtranslatedintoa3.6-foldenhancementinlightextractioncomparedtothatforaplanarLED.ThisimprovementisattributedtothereducedFresnelreflectionandenlargedlightescapecone.Theengineeringofthefar-fieldradiationpatternswasalsodemonstratedbytuningthepackingdensityandpackingconfigurationofthemicrospherearrays.