简介:Monolithicwhite-light-emittingdiodes(whiteLEDs)withoutphosphorsaredemonstratedusingInGaN/GaNmultiplequantumwells(MQWs)grownonGaNmicroringsformedbyselectiveareaepitaxyonSiO2maskpatterns.Themicroringstructureiscomposedof{1-101}semi-polarfacetsanda(0001)c-plane,attributedtofavorablesurfacepolarityandsurfaceenergy.ThewhitelightisrealizedbycombiningshortandlongwavelengthsofelectroluminescenceemissionsfromInGaN/GaNMQWsonthe{1-101}semi-polarfacetsandthe(0001)c-plane,respectively.ThechangeintheemissionwavelengthsfromeachmicrofacetisduetotheIncompositionvariationsoftheMQWs.Theseresultssuggestthatwhiteemissioncanpossiblybeobtainedwithoutusingphosphorsbycombiningemissionlightfrommicrostructures.
简介:Angularcoloruniformity(ACU)isakeyfactorusedtoevaluatethelightqualityofwhite-lightemittingdiodes(LEDs).Inthisstudy,anoveldoubleremotemicro-patternedphosphorfilm(doubleRMPPfilm)wasusedtoenhancetheACUofaremotephosphor(RP)down-lightlamp.AconventionalRPfilmandremotephosphorfilmwithsinglemicro-patternedfilm(singleRMPPfilm)alsowereexaminedforcomparison.Theangularcorrelatedcolortemperature(CCT)distributionsandtheopticalperformanceofthefilmswereexperimentallymeasured.ThemeasurementresultsshowedthatdoubleRMPPfilmconfigurationexhibitedbettercoloruniformitywithaCCTdeviationofonly441K,comparedwith556KforthesingleRMPPfilmconfigurationand1390KfortheRPfilmconfiguration.AsimulationbasedonFDTDandraytracingcombinedmethodalsoconfirmedtheACUimprovement.Inaddition,comparedwiththeconventionalRPfilm,theluminousefficiencyofsingleanddoubleRMPPfilmconfigurationswasincreasedby6.68%and4.69%,respectively,atadrivingcurrentof350mA.TheenhancementoftheACUandluminousefficiencyareduetothescatteringandmixingeffectofthemicropatternedfilm.Moreover,thedoubleRMPPfilmconfigurationhadbetterCCTstabilityatdifferentcurrentsthantheothertwoconfigurations.TheresultsdemonstratedtheeffectivenessandsuperiorityofdoubleRMPPfilminwhiteLEDapplications.