从磊晶看LED_发光效率

從磊晶看LED發光效率郭政達e-mail:[e-mail]LED照明未來預估與市場規模高功率磊晶技術發展解析LED發光效率演進動向MarketDemand$20X75/1000=$1.5(3W)March2006LuminaireEfficiency2006March2007LuminaireEfficiency2006Nichia’sachieves150lm/WwhiteLED(Dec.2006)Epistar’sblueLEDEQE(50%,inproduction,58%R&Dbestperformance)Nichia’swhiteLEDEQE(68%)LuminaireEfficiencySource:Multi-yearprogramplanFY’08-FY’13(DOE)LightingMarketSource:Nov.2007亞洲電子科技雜誌OnlyPerformanceBetterPerformanceforSmallLED?Summary•HighEfficiency•LowCurrentApplication•FlexibleModuleDesign•HigherChipProcessYield•SimplyPackageStructure•HighLumens/Package•HighCurrentApplication•LowerChipProcessYield•ComplexPackageStructureforHeatDissipationSmallLEDPowerLEDApplicationWhiteLEDPerformanceImprovement20002005201020152020200150100500Efficacy(lm/W)Japan21OIDA/USDOEOIDA/USDOEProductionlevelLab.levelIncandescent/HalogenCompactfluorescentTubefluorescentHIDSource:Nichia/CreeYearWhiteLED@20mAWhiteLED@300mAOpticalEfficiencyHID:100lm/W40%UtilizationEfficiencyLightingefficacy40lm/W80%UtilizationEfficiency2005LED:50lm/WLightingefficacy40lm/WOutlineLED照明未來預估與市場規模高功率磊晶技術發展解析LED發光效率演進動向磊晶機台簡介MOCVD(MetalOrganicChemicalVaporDeposition)有機金屬化學氣相沉積MOCVD製程上膜形成過程(i)反應氣體或反應元素因熱裂解由邊界層(boundarylayer)向基板表面輸送氣相擴散，入射原子衝撞基板，一部分被反射，其他吸附於基板上。(ii)基板表面吸附表面擴散，吸附原子於基板表面上擴散，產生原子間之二次衝撞而形成團簇(cluster,原子集合體)，或只在表面上停留某段時間後，再度蒸發解析脫離。(iii)表面反應，核形成團簇反覆與表面擴散原子衝撞或以單原子再釋出，而當原子數超過某一臨界值後開始成長，與鄰接之團簇聚合而成連續膜，大多為三維團簇，但以二維團簇方式成長情形也有。(iv)反應生成物之蒸發解析脫離。(v)脫離之反應生成物向外擴散（outdiffusion)(氣相擴散)。邊界層供給排氣原料(i)輸送(氣相擴散)(ii)吸附表面擴散(iii)反應，核形成horizontalgasflow(iv)解析脫附(v)向外擴散何謂MOCVDⅢ族的(CH3)3GaTMGa(三甲基鎵)、(CH3)3InTMIn(三甲基銦)等，與Ⅴ族特殊氣體如：AsH3(arsine)砷化氫、PH3(phosphine)磷化氫、NH3等，通過特殊載體氣流送到高溫的GaAs晶片、人造藍寶石等晶片上，在Reactor反應器內的高溫下，這些材料發生化學反應，並使反應物沉積在晶片上，而得到磊晶片上形成一層半導體結晶膜，這樣就能做成半導體發光材料，如發光二極體等基本化學式：四元TMGa(g)+AsH3(g)→GaAs(s)+CH4(g)藍光TMGa(g)+NH3(g)→GaN(s)+CH4(g)+N2(g)+H2(g)MOCVD技術與機台的設計，應用,延伸問題包涵多種學問與原理：物理、化學、數學、流體力學、熱力學、機械力學、材料學及電磁學等等RecipexMOCVD機台=磊晶結果MOCVD反應原理MOCVD設備及系統PpPpPpPppppH2N2PumpScrubberExhaustNH3SiH4V-ManIII-ManUp-carrierLow-carrierVentTMGTMATMICpMg2ValveCheckvalveMFCPressureregulator反應腔Reactor氣體傳輸系統gasmixingsystem電控系統E-ControlunitCoolingunitHeaterunitTemp.controlunitPressurecontrolunitGlovebox後端管路抽氣系統ExhaustsystemFilterButterflyvalveVacuumPumpgassupplypowerControlcomputerPLCSLC…SafetycontrolsystemCoolingsupply氣體偵測器MOCVDReactors–themarketNH3NH3NH3NH3NH3NH+TMG3TMGTMGTMGH/N22H/N22Verticalturbodisc(Emcore)Verticalclose-spaced(ThomasSwan)VerticalQuartzTwo-Flow(Nichia)TMGTMGHorizontalQuartzPlanetary(Aixtron)A)B)C)D)E)F)PrincipleofMOCVDH,NP=10-200mbar22TMGa,AsH3TMGa,NH3TMIn,PH3gasblendingreactorhighpurity,precisemixingsafetyGaAs,InPsubstrate,T~400-1200°CD100rpmproductionorientedlowcostofownershipGa(CH)+AsHGaAs+3CH3334TMAl,TMGa,,sapphire5-Ga(CH)+NHGaN+3CH3334scrubbingsystemH2filterunitvacuumpumpthrottlevalvecrystalquality,thicknessuniformity,reproducibilityMOCVDgrowthboundarylayersurfacediffusionandreactionincorporationandgrowthCH4=CH3+HN*+N*=N2wafersurfacemasstransferbydiffusionHHHNCH3GaCH3CH3precursordecomposition-radicaladsorptionCH3CH3-radicalHHHNGaCH3CH3CH3H2H2H2H2gasphaseMOCVDGrowthCriteriaThicknessuniformityCompositionuniformityDopingconcentrationuniformityCleanwafersurfaceOnwaferuniformityWafertowaferuniformityRuntorunstability(reproducibility)Lessmaintenance(highthrough-put)LightExtractionEfficiencyGeometryEffect0.600.650.700.750.800.850.900.951.0000.511.522.5Diearea(mm^2)NoralizedEfficiency@0.5A/mm^2LumiledsAlInGaNGeometryEffect145632EfficiencyDroopProblem(IQE)Lm/$~Lm/PackageRecombinationMechanismsSchubertetal.Appl.Phys.Lett.91,2311142007DefectDensitywithoutpiezoelectricfieldwithpiezoelectricfieldI.V.RozhanskyandD.A.Zakheim:phys.stat.sol.(a)204,No.1(2007)PiezoeletricFieldEffectI.V.RozhanskyandD.A.Zakheim:phys.stat.sol.(a)204,No.1(2007)nnppp-MQWLEDI.V.RozhanskyandD.A.Zakheim:phys.stat.sol.(a)204,No.1(2007)n-p-nLEDKimetal.Appl.Phys.Lett.91,1835072007PolarizationEffectPolarizationEffectKimetal.Appl.Phys.Lett.91,1835072007OutlineLED照明未來預估與市場規模高功率磊晶技術發展解析LED發光效率演進動向LED發光效率演進動向Marketpulllm/W→lm/packaged→lm/$200mA/mm2→350mA/mm2→700mA/mm2→2000mA/mm2Whatwillhappen@2A/mm2?CurrentdensityHeatdispersionPackageissueCurrentUniformity–1NichiaLumiLedsLightingCurrentUniformity–2CurrentUniformityThermalEfficiencySource:OIDA/USDOELm/$~Lm/PackageChipLevelImprovementTj=Ta+I*V*RthFlipChipThinGaNThermalResistanceModelHeatSpreadingLm/$~Lm/PackageDreamsComeTrue100WLED400WMercury100WLEDRoadTestonNTUCampus(3,600lm@37.5lm/W)