Molecular beam epitaxially grown copper indium diselenide and copper gallium diselenide films

2005·12.8 MB·English

by  Yoon, Seokhyun

MOLECULARBEAMEPITAXIALLYGROWNCOPPERINDIUMDISELENIDE
ANDCOPPERGALLIUMDISELENIDEFILMS
By
SEOKHYUNYOON
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2005
Tomywife,JeongyunYang;andmychildren,Yeolim,Edward,andJake.
Copyright2005
by
SeokhyunYoon
ACKNOWLEDGMENTS
TheauthorwouldliketothankDrs.OscarD.Crisalle,FanRen,ShengS.Liand
PaulHollowayforservingassupervisorycommitteeandthoughtfuladvice.Hewould
liketopresenthissinceregratitudetohiscommitteechair,Dr.TimothyJ.Anderson.His
encouragementandinsightintotheresearchtopichavebeenveryhelpfultothecandidate
throughouthisstudy.
TheauthoralsowantstoshowhisgratitudetohispredecessorsincludingBillyJ.
Stanbery,SukuKim,andSerkanKincalfortheireffortinconstructingthePMEEsystem
andfortheprecedingstudyonCu(In,Ga)Se2materials.Itwasalsoagreatpleasureforthe
authortoworkwithcolleaguesincludingWooKyoungKim,RyanKaczynski,Ryan
AcherandothermembersinthephotovoltaicsgroupandDr.Anderson’sresearchgroup.
TheauthorwouldalsoliketothankDr.ChinhoPark,whoprovidedphotoluminescence
measurements.HealsowishestoexpresshisappreciationtoMr.D.VinceandMr.J.
HinnantfortheirkindsupportforhisexperimentsandS.Gapinskiforhissupportofthe
infrastructureatMicrofabritechwherethePMEEreactorislocated.Healsobelievesthat
thestaffmembersinthedepartmentalofficedeservehisgratitude.Theauthorwouldlike
tothanktheLGChemicalResearchParkforthesupportduringhisdoctoratestudy.
Finally,theauthorwouldliketothankhiswife,JeongyunYang;hisparents,
GumjaParkandSungjungYoon;andhismother-in-law,SukheeAhn.Withouttheir
support,encouragement,andlove,hecouldnothavesucceeded.
IV
311
TABLEOFCONTENTS
Page
ACKNOWLEDGMENTS iv
LISTOFTABLES viii
LISTOFFIGURES xi
ABSTRACT xx
CHAPTER
INTRODUCTION
1 1
1.1TheoreticalBackground 1
1.1.1HistoryofSolarCells 1
1.1.2DevicePhysics 3
11..11..34CThueI6rn.2mSoec2haenmdisCturGyaaSned2-sbtrauscetdurpahlotporovpoelrttaiiecsdoefviCcIeSsorCGSmaterials 78
1.1.4.1Chalcopyriteora-CIS 11
1.1.4.2Sphaleriteor8-CIS 1
1.1.4.3P-CIS(Cu2In4Se7andCuIn3Se5) 14
1.1.4.4CuAu-likeCIS 14
1.1.5DefectsinchalcopyriteCISorCGS 15
1.1.5.1DefectsinCIS 17
1.1.5.2DefectsinCGS 18
1.1.5.3ComparisonofdefectsinCISandCGS 21
1.1.5.4NaandCIGS 23
1.1.5.5Firstprinciplescalculationofdefectenergies 27
1.1.5.6SummaryofDefectStatesandEnergyLevelsinCISandCGS 29
1.1.6Reviewoftheliteratureontheeffectsofgrainboundaries(GBs) 3
11..11..66..21IStmupdaicetsoofnGGBBsEofnfeCcItsGSuscienlglsaOne-DimensionalModel 332
1.1. StudiesonGBEffectsusingaTwo-DimensionalModel 35
1.1.7GBmodelsforCIGScells 36
1.2ExperimentalMethods 38
1.2.1ReactorSpecification 38
1.3ScopeoftheThesiswork 40
v
791
2EPITAXIALGROWTHOFCuInSe2ATLOWTEMPERATURE 44
2.1Backgrounds 44
2.2ExperimentalApproach 45
2.3Composition,PhaseandSurfaceMorphologyofEpitaxialFilms 47
2.4TEMAnalysisofas-grownEpitaxialFilms 59
2.5StrainAnalysisofEpitaxialCISFilmgrownatLowTemperature 68
2.6SummaryandConclusions 74
3EPITAXIALGROWTHOFCuInSe2ATHIGHTEMPERATURE 78
3.1Introduction 78
3.2ExperimentalApproach 79
3.3Composition,PhaseandSurfaceMorphologyofCISFilms 80
3.3.1EPMAAnalysis 85
3.3.2Cross-sectionSEMImages 89
3.4XRDAnalysisofCISFilmsgrownatHighTemperature 90
3.4.1.XRD0-20Scanandco-rockingCurveAnalysisofCISFilmsGrownat
HighTemperature 90
3.4.2StrainAnalysisofCISFilmsGrownatHighTemperature 93
3.5TEMAnalysisofCISFilmsGrownatHighTemperature 96
3.5.1TEMAnalysisofCu-richCISFilm(W558) 97
3.5.2TEMAnalysisofIn-richCISFilm(W560) 102
3.5.3TEMAnalysisofCu-richandNa-dosedCISfilm(W584) 106
3.5.4TEMAnalysisofIn-richandNa-dosedCISfilm,W590 11
3.6SummaryandConclusions 114
4EPITAXIALGROWTHOFCuGaSe2ATHIGHTEMPERATURE 117
4.1Introduction 11
4.2ExperimentalApproach 118
4.3Composition,PhaseandSurfaceMorphologyofCGSFilms 11
4.3.1EPMAAnalysis 124
4.3.2Cross-sectionSEMImages 126
4.4XRDAnalysisofCGSFilmsgrownatHighTemperature 128
4.4.1XRD0-20Scanandco-rockingCurveAnalysisofCGSFilmsGrownat
FlighTemperature 128
4.4.2StrainAnalysisofCGSFilmsgrownatHighTemperature 131
4.5TEMAnalysisofCGSFilmsGrownatHighTemperature 133
4.5.1TEMAnalysisofCu-richCGSFilm(W552) 134
4.5.2TEMAnalysisofGa-richCGSFilm(W567) 140
4.5.3TEManalysisofCISfilmW583 144
4.6SummaryandConclusions 148
5STUDYOFDEFECTSTRUCTUREBYPHOTOLUMINESCENCE
SPECTROSCOPY 152
vi
5.1Introduction 152
5.2TheoreticalBackground 153
5.3ExperimentalApproach 157
55..44PLMeasurementofEpitaxialCGSFilms 158
5.4.1PLSpectra 158
5.4.2ThermalQuenchingofPLPeaks 167
SummaryandConclusions 170
6STUDYOFGRAINBOUNDARYEFFECTSINCISSOLARCELLS 174
6.1TheoreticalBackground 174
6.2Electrostaticsofp-nJunctionSolarCells 174
6.3One-dimensionalSimulation 179
6.3.1ReferenceCase(CIS-1) 182
6.3.2ImpactofDeeperAcceptorandCompensatingDonorsinCISLayer 183
6.3.3ImpactofElectronandHoleTrapsandRecombinationCenterinthe
CISLayer 184
6.4.2
6.3.4ImpactofGrainBoundaries 186
6.4Two-DimensionalSimulation 189
6.4.1TheGBEffectoftheSquareRectangularGrain 189
6.4.2EffectoftheGBorientation 205
EffectoftheJunctionDepletionRegionontheGBEffect 210
6.5SummaryandConclusions 216
7CONCLUSIONS 212
7.1EpitaxialGrowthofCuInSe2atLowTemperature 220
7.2EpitaxialGrowthofCuInSe2andCuGaSe2atHighTemperature 222
7.3PhotoluminescenceStudyofEpitaxialCuGaSe2Films 225
7.4StudyoftheGrainBoundaryEffectonCuInSe2SolarCell 226
LISTOFREFERENCES 230
BIOGRAPHICALSKETCH 237
vii
11
LISTOFTABLES
Table page
1-
1-1.Defectstatesandenergylevelabovethevalencebandandformationenergyfor
acceptorsinCIS 29
21--2.Defectstatesandenergylevelbelowtheconductionbandandformationenergyfor
donorsinCIS 31
3.Defectstatesandenergylevelabovethevalencebandandformationenergyfor
acceptorsinCGS 3
2-
31--4.DedfoencotrsstianteCsGaSndenergylevelbelowtheconductionbandandformationenergyfor3
1.BulkcompositionofthreeCISfilmsonMo-coatedglassdeterminedbyICP 74
2-2EPMAanalysisforthematrixandislandregionsofeachCISfilmgrownon
(100)GaAssubstrates 50
2-3.EPMAanalysisforthematrixandislandregionofeachCISfilmgrownon(100)
GaAsafteretchingin10%KCN 52
4.TheoreticalpeakpositionsforGaAs:Spacegroup(Fm-3m),A.=1.54056A 74
1.BulkcompositionofCISfilmsonMo-coatedglassdeterminedbyICP 83
3-2.EPMAanalysisforthematrixandislandregionofCISfilm 88
3-3.co,20,cpandpsivaluesfortheGaAs(224)planeandCIS(228)plane 96
3-4.LatticeconstantsandlatticemismatchwithGaAsforeachCISfilm 97
3-5.LatticeparametersofGaAsandCIScalculatedfromSADPat[1-10]zoneaxisfor
Cu-richCISfilm(W558) 100
3-6.LatticeparametersofGaAsandCISregionforIn-richCISfilm(W560)calculated
fromSADPat[-110]zoneaxis 104
3-7.AssignmentofdiffractionspotsofIn-richCISfilm(W560)fortheregionnearthe
interface 105
1
3-8.LatticeparametersofGaAsandCISregionforIn-richCISfilm(W560)nearthe
interfacecalculatedfromSADPat[-1 10]zoneaxis 105
33--9.LatticeparametersofGaAsandCIScalculatedfromSADPat[-103]zoneaxis..109
34--10.LatticeparametersofGaAsandCIScalculatedfromSADPat[-103]zoneaxis?iL
=20.65 110
11.LatticeconstantsofGaAsandCIScalculatedfromSADPat[01-1]zone 113
1.BulkcompositionofCGSfilmsgrownonMo-coatedglassdeterminedbyICP....120
4-2EPMAanalysisforthematrixandtheislandregionofCGSfilm 123
4-3.(to,20,cp,psi)valuesfortheGaAs(224)planeandCGS(228)plane 130
4-4.LatticeconstantsandlatticemismatchwithGaAsforeachCGSfilm 130
4-
45--5.LatticeparametersofCu-richCGSfilm(W552)calculatedfromSADPat[-1-12]
5- zoneaxis 133
46--6.LatticeparametersofislandtopregioncalculatedfromSADPat[-1-12]zoneaxis...
134
4-7.LatticeparameterscalculatedfromSADPat[1-10]zoneaxisinFigure4-24 140
4-8.LatticeparameterscalculatedfromSADPat[01-1]zoneaxis 143
9.LatticeparameterscalculatedfromSADPat[01-1]zoneaxis 144
1.PeakenergiesandtheirassignmentsobservedinCGSfilmsinthisstudy 170
2.PeakenergiesandtheirassignmentsobservedinCGSfilmsafterSeannealinginthis
study 170
1.Theelectricalpropertiesofeachlayerinthedevice 179
6-2.Propertiesofeachcellforthestudyofthecompensationeffect 183
6-3.Performancesfordifferentacceptorlevelandforcompensatingdonors 183
6-4.Propertiesofeachcellforthestudyoftheeffectoftraps 184
6-5.Performanceofeachsolarcellforthestudyoftheeffectoftraps 186
6-6.ThelengthofthedepletionregionintheCISlayerandbuilt-inpotentialineach
dopingratio 21
IX
6-7.TheparametersforthecalculationofthedepletionregionintheCISwith
heterojunctionsequations 212
6-8.ThelengthofthedepletionregionintheCISlayerandbuilt-inpotentialineach
dopingratiowithheterojunctionsequations 212
x