Design and fabrication of GaN-based heterojunction bipolar transistors

148 Pages·2003·6 MB·English

by  Lee, Kyu-pil. 1961-

DESIGNANDFABRICATIONOFGaN-BASEDHETEROJUNCTION
BIPOLARTRANSISTORS
By
KYU-PILLEE
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2003
Inhisheartamanplanshiscourse,
But,theLORDdetermineshissteps.
Proverbs16:9
ACKNOWLEDGMENTS
Firstandforemost,Iwouldliketoexpressgreatappreciationwithallmyheartto
ProfessorPeartonandProfessorRenfortheirexpertadvice,guidance,andinstruction
throughouttheresearch.Ialsogivespecialthankstomembersofmycommittee
(ProfessorAbernathy,ProfessorNorton,andProfessorSingh)fortheirprofessionalinput
andsupport.Additionalspecialthanksarereservedforthepeopleofourresearchgroup
(Kwang-hyun,Kelly,Ben,Jihyun,andRisarbh)fortheirassistance,care,andfriendship.I
amverygratefultopastgroupmembers(Sirichai,Pil-yeon,David,DonaldandBee).1
alsogivemythankstoP.Mathisforherendlesshelpandkindness;andtoMr.Santiago
whoisnetworkassistantintheChemicalEngineeringDepartment,becauseofhisgreat
helpwithmysimulation.Ialsothankmydiscussionpartnersaboutmaterialgrowth
technologies,Dr.B.Gila,Dr.M.Overberg,JerryandDr.Kang-NyungLee.Iwouldlike
togivemythankstomyfriends(especiallyKyung-hoon,Young-woo,Se-jin,Byeng-sung,
Yong-wook,andHyeng-jin).Evenwhentheywereverybusy,theyalwayshelpedmy
researchworkwithouthesitation.
IcannotforgetSamsung'svicepresidentDr.Jong-wooPark’sdevotedhelp,and
thesteadfastsupportfromSamsungElectronics.WithoutSamsung’sfinancialsupport,it
wouldnothavebeeneasytofinishmyworksuccessfullyattheUniversityofFlorida.
Igiveallofmysinceregratitudetomyparents,myparents-in-law,andmy
brothersandsisters.Iespeciallythankmylovelywife,Soon-hee;mysmartson.
Ah-rhem-sol;andmyhoney-sweetdaughter,Ah-rhem-byeol,fortheiremotionalhelp,
inspiration,andcontinualprayers.Finally,IthankourJesus.
IV
1 461
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFTABLES vii
LISTOFFIGURES viii
ABSTRACT
xiii
CHAPTER
INTRODUCTION
1 1
2 LITERATUREREVIEW 7
2.1 GaN-BasedMaterialCharacteristics 7
2.1.1 PhysicalProperties 7
2.1.2 TransportProperties 13
2.1.2.1 ElectronSaturationVelocity 13
2.1.2.2 MobilityVersusImpurities/Phonons 1
2.1.2.3 MobilityVersusDislocation 1
2.1.2.4 MinorityCarrierLifetimes 17
2.1.3 PhysicalParametersofIll-NitrideSemiconductors 17
2.2 Simulation 20
2.2.1 DeviceSimulators 21
2.2.1.1 MEDICI 22
2.2.1.2 ATLAS 25
2.2.1.3 MIN1MOS-NT 25
2.2.1.4 PISCES-2ET 26
2.2.1.5 SEDAN 27
2.2.2 BasicEquations 28
2.3 GaN-BasedElectronicDevices 30
2.3.1 FieldEffectTransistors(FETs) 3
2.3.1.1 HeterojunctionFieldEffectTransistors 32
2.3.1.2 GaN-basedMOSFETs 35
2.3.2 GaN-BasedBipolarDevices 36
2.3.2. PhysicsofHeterojunctionBipolarTransistors 37
v
1
3
PROCESSDEVELOPMENTFORGaN-BASEDBIBOLARTRANSISORS .41
3.1 Introduction 41
3.2 ProcessDevelopmentforSmall-AreaGaN-BasedBipolarTransistors 42
3.2.1 ExperimentalMethods 42
3.2.2 ResultsandDiscussion 42
3.2.2.1 DevelopmentofSelf-AlignedProcess 42
3.2.2.2 TemperatureDependentPerformanceofGaN-Based HBTs 54
3.2.2.3 Emitter-andBase-RegrowthGaN-BasedHBTsandBJTs 58
4 SIMULATIONOFGaN-BASEDNPNBIPOLARTANSISTORS 63
4.1 Introduction 63
4.2 EffectsofBaseStructureonPerformanceofGan-Based
HeterojunctionBipolarTransistors 63
6 4.2.1 ExperimentalMethods 63
4.2.2 ResultsandDiscussion 67
4.3 InfluenceofLayerDopingandThicknessonPredictedPerformance
ofnpn AlGaN/GaNHBTs 75
4.3.1 ExperimentalMethods 75
4.3.2 ResultsandDiscussion 75
4.4 SimulationsofInGaN-BaseHeterojunctionBipolarTransistors 87
4.4.2 ExperimentalMethods 87
4.4.2 ResultsandDiscussion 88
4.5 RfPerformanceofGaN-BasednpnBipolarTransistors 99
4.5.1 ExperimentalMethods 99
4.5.2 ResultsandDiscussion 100
5 SIMULATIONOFGaN-BASEDPNPBIPOLARTRANSISTORS 112
5.1 Introduction 11to
5.2 TemperatureDependenceofpnpGaN/InGaNHBTPerformance 1 to
5.2.1 ExperimentalMethods 11to
5.2.2 ResultsandDiscussion 114
SUMMARY
122
REFERENCES 125
BIOGRAPHICALSKETCH 131
VI
LISTOFTABLES
Table page
2-1. Thephysicalparametersindifferentsemiconductormaterials ..8
22--2. IonizationenergyofimpuritiesforWurtziteGaN ..9
3-
24--3. PhysicalparametersofIll-Nitridesemiconductors ..18
2-4. Comparisonofdifferentdevicesimulators
2-5. Namingconventionsofthefrequencyband 34
6. Banddiscontinuitiesatheterointerfaces 39
1. Temperature-dependentcontactdataforp-GaN 56
1. Workingconditionofdevicesasprocessdesign 67
4-2. Basecurrentcomponentsfordifferentbasestructures 69
4-3. Basecurrentcomponentsasbasedoping .71
4-4. Basecurrentcomponentsasafunctionofemitterdoping ,73
vii
0 0 0 1
LISTOFFIGURES
Figure page
2-1 TheIII-Vcompoundsemiconductortree 7
2-2 SIMSprofileofMgtailinemitterofMOCVDgrownnpnstructure
comparedwithMBEgrownjunctions 1
2-3 ContributionstoelectronmobilityinGaNfrompolaroptical,piezoelectric
andacousticsscattering,asafunctionoftemperature 14
22--4 EffectofionizedimpurityscatteringonelectronmobilityinGaNfortotal
3- oiofn(i1z)ed5xi1mpu17rictmy'c3;on(c2)en2txrlat0i1o7ncmof'37;.(53x)17.156xc1m'136,camn'd3c;a(r4r)ie2rxdle0ns16itcime's3 15
2-5 Electronmobilitiesincubic(dashedline)andhexagonal(solidline)GaN 16
2-6 SchematicstructureofHEMT 33
2-7 SchematicstructureofMOSFET 36
2-8 BasicfeaturesofenergybanddiagramofHBT 38
9 VariouscurrentcomponentsinaHBT 38
1 MasklayoutofthesmallsizeHBT 43
3-2 ProcesssequenceforHBTtotheemitter-etchstep 44
3-3 ProcesssequenceforHBTfromsidewalldepositiontobasemetaldeposition..45
3-4 ProcesssequenceforHBTfrombasemesalithographytodevicepassivation...46
3-5 Schematicdevicestructureafterfinalmetaldeposition 48
3-6 SEMmicrographsofHBTafterdifferentstagesoftheprocess 49
m-7 SEMmicrographsofsmall-areaHBTwithemittermetal,
basemetal,collectormetalandbasemesa 50
viii
0
3-8 Common-base(top)andcommon-emitter(bottom)I-Vcharacteristics
fromlarge-areaHBTs 51
3-9 Common-baseI-Vcharacteristicsfromsmall-areaHBT 53
3-10 IonizationefficiencyofMgacceptorsinGaN,andFermi-levelposition
forGaNdopedwith1018cm"1Mgacceptorsasafunctionoftemperature 54
3-11 TmperaturedependenceofgaininlargeandsmallareaHBTs 57
3-12 LayerStructurefortheBJTwithregrownemitter 58
33--13 TEMcross-sectionofBJTwithregrownemitter 59
4-
3-14 SEMmicrographsoflargearearegrownemitter(top)and
close-upofedgeofregrownregion(bottom) 60
3-15 SEMmicrographsofsmallarearegrownemitterinsideview(top)
andplanview(bottom) 61
16 Common-emitterI-Vcharacteristicsfromsmall-area,regrownemitterBJT 62
1 HBTbanddiagramatVCe=10V,VBe=4.2V(top)and
c5uprariernstoffloAwl0(.2bGotat0o.mg)N/fGoraNAl(01.20G0aA0/.1g0N0eAm)itdtoerpeadndatba1s0e19ccomns'i3stingof 64
4-2 HBTbanddiagramatVce=10V,VBe=4.2V(top)and
currentflow(bottom)forAlo.2Gao.8Nemitterandbaseconsistingof
5pairsofIn0.2Gao.gN/GaN(100A/100A)dopedat1019cm"3 65
4-3 HBTbanddiagramatVCe=10V,Vbe=4.2V(top)and
c1uprariernstoffloInw0(.2bGoatot.ogmN)/fGoraNAl(05.02G0aA/0.5g0N0eAm)itdtoepreadndatb1a0se19ccomn"s3istingof 66
4-4 HBTdccurrentgainasafunctionofcollectorcurrentfordeviceswith
AlGaNemitteranddifferentInxGai.xN(5pairs)baselayers(top)or
clno0m.2pGoanoe.ngNt/laGyaeNrtbhaisceknleasyser(sboofttdoimff)erentnumbersofpairsanddifferent 68
4-5 Effectofbasedopingondccurrentgain(top),saturationcurrent(center)or
dBoVpcienog(5bxo1tto16m)c.m"T3heanedmibtatseertdhoipciknngeswsa1s010.08Axli0n1e9accmh"c3,asceollector 70
IX
0 0 0 0 0
4-6 Effectofemitterdopingondccurrentgain(top)andsaturationcurrent(bottom).
Theemitterdopingwas1.8x1 19cm"3,collectordoping5x1 16cm"3andbase
thickness1000Aineachcase 72
4-7 SchematicofHBTstructureusedforthesimulationandalsothecurrentflow
Contours 76
4-8 HBTbanddiagram(Vce=0,VBe=0)fortwodifferentbasedopinglevels,
5xl017cm"3(top)or1019cm"'’(bottom) 77
4-9 Simulatedcommon-emittercharacteristicsforHBTswithtwodifferentbase
dopinglevels,5xl019cm’3(top)or1019cm"3(bottom).Theemitterdoping
w1a0s2<)1c.m8"x31an1d9cbma"s3e,tcholilcekcnteosrsdionpbiontgh5cxa1ses16cm’3sub-collectordoping 78
4-10 dccurrentgain(top)andVceatthesaturationpoint(bottom)
asafunctionofbasedoping 79
4-11 BVceo(top)andsaturationcurrent(bottom)asafunctionofbasedopingfor
variouscollectordopinglevels 80
4-12 BVceo(top)asafunctionofcollectordoping(top)andGummelplot
(bottom)foraspecificsetofdopingandthicknessconditions 82
4-13 HBTgainversuscollectorcurrent(top)anddccurrentgainand
collectorcurrentversusemitterdoping(bottom) 83
4-14 DCcurrentgainandcollectorcurrent(top)andBVceo(bottom)
asafunctionofthickness 85
4-15 DopingprofileinGaN/InGaNHBT 87
4-16 CalculatedbanddiagramsforHBTatVce=0V,Vbe=0V(top)
orVCe=15V,VBe=4.2V(bottom) 89
4-17 Schematicofdepletionregionatoperationconditionfor1000Abase,
e-dopingof1.8xl019cm"3andc-dopingof5xl016cm"3
atbasedopingof1017cm"3(top)or1018cm"3(bottom) 90
4-18 Gummelplotsasafunctionofbasedoping(top)anddccurrentgain
asafunctionofcollectorcurrent(bottom) 91
4-19 Common-emittercharacteristicsforbasedopingofeither1018cm"3(top)
or5x1 19cm"3(bottom) 93
4-20 Earlyvoltage(top)andBVceo(bottom)asafunctionofbasedoping 94
x