金属有机化学气相沉积法生长纯闪锌矿结构P型砷化镓纳米线

Vol.32,No.5JournalofSemiconductorsMay2011Growthofpurezincblendep-typeGaAsnanowiresbymetal-organicchemicalvapordepositionLiRan(李然)1;Ž,HuangHui(黄辉)1;2;Ž,RenXiaomin(任晓敏)1,GuoJingwei(郭经纬)1,LiuXiaolong(刘小龙)1,HuangYongqing(黄永清)1,andCaiShiwei(蔡世伟)11KeyLaboratoryofInformationPhotonicsandOpticalCommunications,MinistryofEducation,BeijingUniversityofPostsandTelecommunications,Beijing100088,China2ElectronicsScienceandTechnologyInstitute,DalianUniversityofTechnology,Dalian116085,ChinaAbstract:Verticalp-typegalliumarsenide(GaAs)nanowireswithpurezincblendestructureweregrownonGaAs(111)Bsubstratebymetal-organicchemicalvapordepositionviaaAu-catalystvapor-liquid-solidmechanism.Thep-typedopingwasinvestigatedbyadditionaldiethylzinc(DEZn).InthehighII/IIIratiorange(II/III9.1%),thereexistsacriticallengthbeyondwhichkinkingtakesplace.Twopossiblereasonsarediscussed.ZnoccurrenceinthenanowireswasverifiedbyenergydispersiveX-ray(EDX)analysis.CorrespondingtoII/IIID0.2%,thedopingconcentrationisabout81018cm3.Keywords:GaAsnanowire;p-typedoping;metalorganicchemicalvaporposition;zinc-blendestructureDOI:10.1088/1674-4926/32/5/053003PACC:0130;0220;7280E1.IntroductionSemiconductornanowires(NWs)areidealbuildingblocksforafunctionalnanoscaledeviceŒ13.P-typedopingisessen-tialforthenanoscaledevice.However,systematicstudiesonreliableandwell-controlleddopingarestilllackingforsemi-conductornanowires.Asreported,therearethreemajorp-typedopantatomsinGaAsnanowires:ZnŒ4;5,CŒ6andBeŒ7;8.AsforCŒ6,addingCBr4tothegasphasewillcorrodethenanowires.ForBeŒ7;8,itisusuallyasap-typedopantprecursorinamolecularbeamepi-taxy(MBE)system.Inprinciple,therearetwopossiblewaystoincorporateactivedopantsintonanowiresŒ5:(a)dopingduringthegrowthprocessŒ4;68;and(b)postgrowthdopingviadif-fusionorionimplantationŒ5.However,forpostgrowthdopingviaimplantationandannealing,anumberof5109cm2dislocationswereobservedinthedark-fieldimage.Thedislo-cationsresultedfromtherecrystallizationprocessŒ5.Inthispaper,Au-catalystvapor-liquid-solid(VLS)Œ9growthofstacking-faults-freezincblendep-typeGaAsnanowiresonGaAs(111)Bsubstratewereinvestigatedbyus-ingDEZnasadopantprecursorduringthegrowthprocess.Thenanowireswerecharacterizedwiththefollowingtechniques:scanningelectronmicroscopy(SEM),transmissionelec-tronmicroscope(TEM)andenergydispersiveX-ray(EDX)analysis.2.ExperimentTheepitaxywasperformedbymetalorganicchemicalva-pordeposition(MOCVD)withaThomasSwanCCS-MOCVDsystematapressureof100TorrŒ10;11.GrowthofP-GaAsnanowirewascarriedoutinthefollowingsteps.(1)a4nmAulayerwasdepositedonthesubstratebymagnetronsputtering.ThentheAu-coatedGaAs(111)BsubstratewasloadedintoaMOCVDreactorandannealedinsituat650Cunderarsineambientfor300stoformAu–Gaalloyparticlesasacatalyst.(2)H2wasusedasthecarriergas.Trimethylgallium(TMGa)andarsine(AsH3/wereusedasprecursorsataconstantV/IIIratioof70.Simultaneously,DEZnasdopingprecursorwasin-jectedintothereactorcell.(3)Nanowiresweregrownfor500satagrowthtemperatureof440C.SamplesA,BandC’sII/IIIratiowas18.1%,9.1%,0.2%,respectively.Instep(3),lowtemperaturegrowthcanreduceplanarde-fectsandlateralovergrowthŒ12;13,andthegrowthconditionincludingtemperatureandV/IIIratioispreviouslyoptimized.Atomforcemicroscopy(AFM)wasusedtoanalyzethedensityoftheAu–Gaparticlesaftertheannealingprocess.ThemorphologiesofthenanowireswerecharacterizedbyaHitachiS-5500SEM.Thecrystalstructureofthenanowireswasinves-tigatedbyaJeol-2100FTEM,whichoperatesat300kV.TEMspecimenswerepreparedbyultrasonicnanowiresinethanolfor5minandthendispersingthemontoholeycarbongrids.3.ResultsanddiscussionFigures1,2,and4showtheSEMimagesofsamplesA,BandC,respectively.Ineveryfigure,(a)–(d)showtheverticalview,20inclinationviewandcross-sectionalviewofNWs.ForsamplesAandB(depictedinFigs.1,2),nanowiresarenon-uniformindiameterandlength.InFig.1(d),kinkingtakesplaceinthe389nmposition,whileinFig.2(d),thekinking*ProjectsupportedbytheNationalBasicResearchProgramofChina(No.2010CB327601),theKeyInternationalCooperationRe-searchProjectoftheNationalNaturalScienceFoundationofChina(No.90201035),theChineseUniversitiesScientificFund(No.BUPT2009RC0410),theNationalNaturalScienceFoundationofChina(No.61077049),andthe111ProgramofChina(No.B07005).ŽCorrespondingauthor.Email:[e-mail];[e-mail]12October2010,revisedmanuscriptreceived2December2010c2011ChineseInstituteofElectronics053003-1J.Semicond.2011,32(5)LiRanetal.Fig.1.SEMimagesofsampleA(II/IIID18.1%).(a)Verticalview.(b)Cross-sectionalview,scalebarD2m.(c)Cross-sectionalview,scalebarD1m.(d)Cross-sectionalview,scalebarD500nm.Fig.2.SEMimagesofsampleB(II/IIID9.1%).(a)Verticalview.(b)3timesmagnification,scalebarD4m.(c)Cross-sectionalview,scalebarD3m.(d)ScalebarD1m,andthearrowindicatesthekinkingplace.locationis838nm.Twopossiblereasonsmayinfluencethebendingofp-GaAsnanowires.(1)ExcessZnatomsmayseg-regateonthesidewallsformingthedeformationareaŒ7:Thecomparisonexperimentkinkingbeforeandafter(asshowninFig.3andTable1)candemonstratethattheZnconcentrationhasincreasedafterkinking.(2)Surfacestressan