Table Of Content

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