半导体材料论文7(精)

1、APPLIEDPHYSICSLETTERS94, 0611152009?Electrolumi nesce ncefromTiO2/p+-SiheterostructureYua nyuan Zha ng,Xia ngya ngMaaPeilia ngChen,D on gshe ngLi,a ndDere nYangbStateKeyLaboratoryofSilic on Materialsa ndDepartme ntofMaterialsScie ncea ndEngin eeri ng,ZhejiangUniversity,Hangzhou310027,People sRepubli

2、cofChinaReceived24July2008;accepted15Ja nuary2009;publishedo nlin e12February09Titanium ?lmssputtered on heavilyboron- dopecp+silic onsubstrateswerethermallyoxidizedtoformelectro lumin esce ntTiO2/p+-Siheterostructures.Theelectrolimi nesce nceELfeaturesabroadspectrumcoveri ngredree n ,andblueregio n

3、s.Webelievethati nTiO2recombi natio nsbetwee nelectro nsatoxyge n- vaca ncy-relatede nergylevelsa ndholes in thevale nceba ndresult in theEL.Furthermore,theELmecha nismhasbee nexplai nedi ntermsofthee nergyba nddiagramoftheTiO2/p+-Siheterostructure,whichpossessesa nin termediateultrathi nSiOxlayerre

4、vealedbyhighresolutiontran smissio nm icroscopy.?2009America nln stituteofPhysics.D 01:10.1063/1.307840 9?TiO2isa nin directba nd-gapsemic on ductorwitha nextremelylowef?cie ncyofro om-temperatureTba ndedgelumi nesce nce.1Howeveef?cie ntRTIumi nesce ncemayresultfromdefect-relatedlight-emitti ngce nt

5、ersi nTiO2.2 5Variouseffortshavebee nmadetorealizeelectro lumin es- cenceELfromTiO 2bytakingadvantageofthedefect-relatedlightemissio n. Nakatoeta.6a ndHouzoujietal.7achievedELfromdiffere ntTiO2?lmsi nelectrolytes.Liquidco ntactemployedi ntheirstructures,however,is no tbe ne?cialforwidespreadapplicat

6、i on s.l nthisco ntext,electricallycon ducti ngorga nic,i norga nic,andhybridlayershavebee nu sedtoreplacetheelectrolytestorealizetheELfromTiO2-basedsolid-statedevices.5,8,9Ge nerally,theappropri- atelydesig nedheterostructuresareemployedintheelec-trolumi nesce ntTiO2- baseddevices.l nthisletter,wep

7、reparetheTiO2lms on heavilyboron-dopedsilic on p+-Sisub- stratestoformreas on ablyelectrol umin esce ntTiO2/p+-Siheterostructures.Thisworkmayc on tributetothedevelop-me ntofsilico n- basedoptoelectro nics.Previously,theTiO2lms on silic on substrateswereusuallyi nv estigate dashighdielectricc on stan

8、high- kmaterialsforsilico nm icroelectro nics.1O,11TheELfromTiO2/p+-Siheterostruc-tures,however,has no tbee nreportedsofar.OurTiO2/p+- Siheterostructuresexhibitfairlyi ntensevisibleemissio nsun derforwardbiaswithpositivevolt agec onn ectedtop+-Si,whiletheyare notelectrolumi nesce ntun derreversebias

9、.There- latedELmecha nismhasbee ntentativelydiscussedi ntermsofthee nergyba ndstructuresofTiO 2/p+-Siheterostructures underforwarda ndreversebiases.Tita niumTi ?lmsweresputtered on polished100?rie nted,a nd1.5?1.5cm2sizedp+-Sisubstrateswithacar-rierc oncen trati ono f?1.1?1020cm-3byus in ga99.99%pur

10、eTitarget.Priortobe in gloaded intothesputterchamber,thesilico nsubstrateswereclea nedbyasta ndardRCAprocess,12followedbyadipi nadiluteHFsolutio nH 2O:HF=1O:1i nv olumeratioi no rdertoremovethere sidualoxide onthesurface.Thesputteri ngchamberwas?rstevacuatedto5?10-3Padthe nch argedwitharg ongastoawo

11、rki ngpressureof0.8Pa10 Onm Ti?lmswerede-a positedonthesiliconsubstratesat100Cfor10minwithasputteringpowerof60W.TheTi?lmsweresubsequentlyoxidizedat500 Cfor5hunderoxygenambienttoformTiO2?lms,whichwereofa natasephase,asc on? rme(yx-raydiffracti onan alysis.Moreover,Hall-effectmeasure- mentrevealedthat

12、theTiO2?lmswereofntypec on ductiv-itywitha nelectro neon ce ntratio no f?3?1017cm-3.?150nmthicki ndiumt in oxide ITO?lmswerethe nsput-teredontheTiO2?lmsatasubstratetemperatureof350 C.ThelTOatmiBwetobecircularwithadiameterof?1cm .Fin ally, ?15 Onm thickalumi nu m?lmsweredeposited on thebacksideofsili

13、c on substratesat200CtoformOhmicco ntactsbyelectro n-beamevaporati on .Atypi-caldevicefabricatedthroughtheabove-me nti on edproce- duresisschematicallyillustratedinthetop-lefti nsetofFig.1.Figurelshowsthecurre ntvoltagel- VcharacteristicofthedeviceHerei n,theforwardandreversebiasesrefertothoseofthep

14、+- Sisubstratethatisc onn ectedtothepositivea ndnegativevoltages,respectively.Theli nearl- Vcharacter-isticshow nin thebottom-righti nsetofFig.ldem on stratesa nOhmicco ntactbetwee nITOa ndTiO2.Si nceAlalso bElectro nicmail:mxy oun .Authortowhomcorresp onden ceshouldbeaddressed.Electro nicmail:-64-2

15、024Voltage (V)mseya .c n.FIG.I.Coloro nli neCurre nt-voltagel-VcharacteristicoftheTiO2/p+-Siheterostructure-baseddevice.Thetop-left in setshowstheschematicdia-gramforthedevice,a ndthebottom- rightinsetshowstheIVcharacteristicofthelTOco ntact on TiO2?lm.?2009Americanln stituteofPhysics 0003-

16、6951/2009/946/061115/3/$25.0094,061115-1Downloaded 08 Apr 2010 to 1. Redistribution subject to AIP license or copyright;see /apl/copyright.jsp061115-2Zhan getal.Appl.Phys.Lett.940611152009?FIG.3.Cross-sectio nalHRTEMimageoftheTiO2/p+-Siheterostructure.FIG.2.Coloro nli ne

17、aRTELspectrafortheTiO2/p+-Siheterostructureappliedwithdiffere ntforwardbiasvoltagesof4.0,4.5,4.8,5.2,a nd5.4V.Theupperi nsetshowstheCCDcameraimagesofthelightemissio nscor-enden ceofi ntegratedspectrali nten sity onaging00(c-5(90fnA5 4V4 (75mA5.2V3(60mA4 0V)2(45mA4 5V 1(30mA4 OVJ800as. Un derforwardb

18、ias,thee nergyba ndofliO2bendsdow whiletheen ergyba ndofSibe ndsupwardneartheSi/SiOx1A. 2rns&(/)uu-(nra) gsusu600Wavelength (nm)7004005000100200300400 500600Aging time (h)FIG.4.Coloro nli neSchematice nergy-ba nddiagramsfortheTiO2/p+- Siheterostructure underappropriatelyhighforwardbiasvoltagaa n

19、dre- versebiasvoltage).Theoxyge n-vacancy-relatedvisibleemissio nsarealsoillustratedia. bi newithholesi navery narrowregionduetotheveryshortlifetimeofexcessmi no ritycarriersel ectronsn p+-Si.C on- sequently,therearefewelectro nsin theco nductio nban dofTiO2,leadi ngto negligibleelectro n-holerecomb

20、 in ati onin TiO2a ndthereforetheabse nceofELfromTiO2.In summary,TiO2/p+- Siheterostructuresareformedbythermaloxidatio no fTi?lmsputteredon silico nsubstrates.T heheterostructuresexhibitever-stro ngerELwithi ncreasi ngforwardbias.Thered,gree n,a ndbluecomp onentsofELresultfrom thetra nsiti on sofele

21、ctr on satdiffere ntoxyge n-vaca ncy- relatedenergylevelstothevale nceba ndofTiO2.Despitethedegradatio nduri ngthei niti?1OOhoperatio n, theELfromTiO2/p+-Siheterostructuresisstabilizedafter- ward.ThemechanismsofELa ndcarriertra nsportatio nfortheTiO2/p+-Siheterostructuresareelucidatedbyexami nin gth

22、ee nergy- banddiagramsoftheheterostructures un derfor- warda ndreversebiasesa ndtaki ngin toaccoun tthecarriert unn eli ngthroughtheultrathi nin termediateSiOxlayerTheauthorswouldliketotha nk?nan cialsupportsfromthe 973Program ”？an tNo.2007CB613403?ResearchFu ndforDoctoralProgramofHigherEducatio nof

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26、licatio nsNoyesParkRidge,NJ,1993?1faceAtasuf?cie ntlyhighforwardbiasvoltage,theEvS ican beleveleddow nan devenlowertha n theEvTiO2? nthiscase,holesaccumulatedattheSi/SiOxi nterfaceca ntun-n elthroughthei ntermediateSiOxlayeri ntothevale ncebandofTiO2.Asschematicallyillustrat edinF ig.4?,electro nsin thec on ductio nban dofTiO2spon ta neouslydropdow ntotheoxyge n- vaca ncy-relatede nergylevelsa ndthe ntotheva-len ceba ndtorecombi newithholes,givi ngrisetodiffere ntvisibleemissions.Moreover,electro n saccumul