光電子材料與器件-2-MOCVD-growth

1TheAIX2800G4HTinthe42x2inchconfiguration2MOCVDtechnologyandepitaxialgrowthChenPeng

InstituteofOptoelectronics，NanjingUniversity&Yangzhou

PhysicsDepartment,NanjingUniversity

2-Dec-103IntroductionMetalorganiccompoundsTheMOCVDtechniqueandgrowthsystemEpitaxialgrowthbasicExample:MOCVDgrowthofGaN

MaterialsCharacterizationsOutline4CompareofepitaxialmethodsGrowthmethodtimefeatureslimitLPE

(Liquidphaseepitaxy)1963GrowthformsupersaturatedsolutionontosubstrateLimitedsubstrateareasandpoorcontroloverthegrowthofverythinlayersVPE

(Vaporphaseepitaxy1958UsemetalhalideastransportagentstogrowNoAlcontainedcompound,thicklayerMBE

(MolecularBeamEpitaxy)19581967DepositepilayeratultrahighvacuumHardtogrowmaterialswithhighvaporpressureMOCVD

(Metal-OrganicChemicalVaporDeposition)1968UsemetalorganiccompoundsasthesourcesSomeofthesourceslikeAsH3areverytoxic.Introduction5SomeaboutthenameofMOCVDInthereference,MOCVDalsohavesomeothernames.Differentpeoplepreferdifferentname.Allthenamesrefertothesamegrowthmethod.MOCVD (Metalorganicchemicalvapordeposition)OMCVD (OrganometallicCVD)MOVPE (MOvaporphaseepitaxy)OMVPEAP-MOCVD (AtmosphereMOCVD)LP-MOCVD (LowpressureMOCVD)Introduction6

Veryhighqualityofgrownlayers

(highgrowthrateanddopinguniformity/reproducibility)

Highthroughputandnoultrahighvacuumneeded(-comparedtoMBE)

(Economicallyadvantageous,highsystemup-time)

Highestflexibility

(Differentmaterialscanbegrowninthesamesystem)

Growthofsharpinterfacespossible

verysuitableforheterostructures,

(e.g.,multiquantumwells(MQW))WhyMOCVD?Introduction7MOcompoundsCompoundPat298K(torr)ABMeltpoint(oC)(Al(CH3)3)2TMAl14.2278010.4815Al(C2H5)3

TEAl0.041362510.78-52.5Ga(CH3)3

TMGa23818258.50-15.8Ga(C2H5)3

TEGa4.7925309.19-82.5In(CH3)3

TMIn1.7528309.7488In(C2H5)3

TEIn0.3128158.94-32Zn(C2H5)2

DEZn8.5321908.28-28Mg(C5H5)2

Cp2Mg0.05355610.56175Log[p(torr)]=B-A/T

Metalorganiccompounds8MOcompoundssupplysystemMetalorganiccompounds9gashandlingsystemreactorwithheatedsusceptorvacuumsystemcontrolunitscrubbingsystemComponentsofaMOCVDSystemTheMOCVDtechniqueandgrowthsystem10TheMOCVDtechniqueandgrowthsystem11Reactor-1TheMOCVDtechniqueandgrowthsystem12Reactor-2TheMOCVDtechniqueandgrowthsystem13PlanetaryReactor?

Shallowreactorchamber,smallvolumeNobuoyancyFastswitchingrun/ventsystemStrictlyhorizontallaminargasflowduetoPlanetaryprincipleallowssharpexchangeofgasphaseinreactorRotationnoharmforwafer&layerqualitygroupIIIgroupVWaferInjectorceilinginductiveheatedwafercarrierTheMOCVDtechniqueandgrowthsystem14GashandlingsystemThefunctionofgashandlingsystemismixingandmeteringofthegasthatwillenterthereactor.Timingandcompositionofthegasenteringthereactorwilldeterminetheepilayerstructure.

Leak-tight

ofthegaspanelisessential,becausetheoxygencontaminationwilldegradethegrowingfilms’properties.Fastswitchofvalvesystemisveryimportantforthinfilmandabruptinterfacestructuregrowth,

Accuratecontrolofflowrate,pressureandtemperature

canensurethestableandrepeat.

TheMOCVDtechniqueandgrowthsystem15TheMOCVDtechniqueandgrowthsystem16TheMOCVDtechniqueandgrowthsystem17In-SituMonitoring:EpiCurveTTMethod:distancevariationofparallellaserbeams2DCCDcameraDXD(Dz)substratewafer(bentduetostrain)susceptorparallellaserbeamDzDTLASERTheMOCVDtechniqueandgrowthsystem18ThebasicreactiondescribeGaNgrowthcansimplywriteasGa(CH3)3+NH3GaN+3CH4Thegrowthprocedureasfollows:MOsourcesandhydridesinjecttothereactor.ThesourcesaremixedinsidethereactorandtransfertothedepositionareaAtthedepositionarea,hightemperatureresultinthedecompositionofsourcesandothergas-phasereaction,formingthefilmprecursorswhichareusefulforfilmgrowthandby-products.ThefilmprecursorstransporttothegrowthsurfaceThefilmprecursorsabsorbonthegrowthsurfaceThefilmprecursorsdiffusetothegrowthsiteAtthesurface,filmatomsincorporateintothegrowingfilmthroughsurfacereactionTheby-productsofthesurfacereactionsdesorbedfromsurfaceTheby-productstransporttothemaingasflowregionawayfromthedepositionareatowardsthereactorexitGasphaseandsurfacereactionEpitaxialgrowthbasic19TMGaNH3

AbsorptiondiffusionPyrolysisAdductFormationDiffusionDesorptionSurfacereactionBoundarylayer=NH3

=Ga(CH3)3=H=CH3

(0001)GaNsubstrate

Ga(CH3)3+NH3=GaN+3CH4(by-products)BasicReactionI(ByMOCVD)

Epitaxialgrowthbasic20BasicReactionII(ByMOCVD)Epitaxialgrowthbasic21EpitaxialgrowthbasicGrowthatsurfaceterraces/steps22EpitaxialgrowthbasicLatticemismatchandstrain23EpitaxialgrowthbasicExamplesofmismatchdislocationsSapphireGaN24:GaN:Al2O3[1010]GaN[1210]Al2O3[1210]GaN[1010]Al2O3a=3.186A4.758A?3x3.186AWurtzitestructure(0001)GaN//(0001)sapphirewitha30°rotation:latticemismatchbetweenGaNandsapphire:13.8%SchematicIllustrationofGaNGrowthontoSapphire(0001)SurfaceacGaNCrystalStructureExample:MOCVDgrowthofGaN251)GrowthprocessoftheGaNlayeronLT-AlNnucleationlayer(a)IslandGrowth

(b)LateralGrowth(c)Coalescence

(d)Quasi2-DGrowthSapphireLT-AlNGaNExample:MOCVDgrowthofGaNBuffer-layergrowthtechnique26TwoStepMOCVDGrowthprocedureHightemperaturetreatmentBufferlayerEpilayerGrowthTMGaNH3Temperature1150oC550oC1050oCGa(CH3)3+NH3GaN+CH4MOCVDgrowGaNandrelatedmaterialsExample:MOCVDgrowthofGaN27GrowthofGaNonsapphireExample:MOCVDgrowthofGaNGaNthinfilmsgrowthprocess28MorphologybyAFMobservationAfter0.5-mingrowth,GaN~10nm.Islanddiameter~100nmAfter3.0-mingrowth,GaN~150nm.

After30-mingrowth,GaN~1400nm.

Example:MOCVDgrowthofGaN29Example:MOCVDgrowthofGaNGaNthinfilmsgrowthprocess30P-electrode

n-electrodep-GaNn-GaNSapphireSubstrateInGaNQWp-AlGaNGaNBufferlayerExample:MOCVDgrowthofGaNGaN-basedLEDstructureMg31■CrystalDefectFormation(Dislocation):DuringHTEpi-layerGrowthGrowt