2015第1次课第一章绪论.

半导体异质结物理PhysicsofSemiconductorHeterojunction秦志新第一章绪论第一节什么是半导体（1）背景知识通信：传递信息，烽火台，邮驿有线电话电报的发明无线通信、广播检波原理矿石检波电子管收音机晶体管集成电路(i)semiconductorshaveelectricalresistivityintherangebetweenthoseoftypicalmetalsandtypicalinsulators(i.e.,betweenabout10-4and10-10Wcm）(ii)theyusuallyhavenegativetemperaturecoefficientofresistance,(iii)theelectricalconductivityofsemiconductorscanbevaried(inbothsignandmagnitude)widelyasafunctionof,e.g.,impuritycontent(e.g.,doping,temperature,excesschargecarrierinjection,andopticalexcitation.（2）半导体的性质1833年：M.Faraday发现半导体所具有的负电阻温度系数1873年：W.Smith首次发现半导体的光电导效应1874年：F.Braun首次发现半导体的整流效应1947年：Bardeen,Brattain,Shockley制造了第一个晶体管：锗点接触三极管(1956年，获NobelPrize)1949年：提出了PN结晶体管的理论1951年：W.Shockely用扩散技术制造了晶体管1958年L.Esaki研制出隧道二极管1962-63年N.G.Basov研制出半导体激光器1963年H.KroemerZ.Alferov提出异质结激光器1969-70年L.Esaki&R.Tsu提出半导体超晶格1993年S.Nakamura研制出高亮度GaN蓝光发光二极管第二节半导体的发展史Point-contacttransistorJ.Bardeen,W.Shockley,andW.Brattain(1956NobelprizeLaureaet)JohnBardeen,WalterBrattainandWilliamShockleydiscoveredthetransistoreffectanddevelopedthefirstdeviceinDecember1947。1947年，美国电报电话公司（AT＆T）贝尔实验室的三位科学家巴丁、布莱顿和肖克利在研究半导体材料——锗和硅的物理性质时，意外地发现了锗晶体具有放大作用，经过反复研究，他们用半导体材料制成了放大倍数达100量级的放大器，这便是世界上第一个固体放大器——晶体三极管。晶体管的出现，迅速替代电子管占领了世界电子领域。随后，晶体管电路不断向微型化方向发展。第一代半导体材料，以Si、Ge为代表集成电路的主要材料,技术上最成熟，代表人类物质文明的最高水平,广泛应用于计算机和各种电子产品.第二代半导体材料，以GaAs、InP为代表光电子器件，LED和LD,光通信,微波功率器件和电路第三代半导体材料，以GaN、SiC为代表短波光电子器件，蓝、白光LED，蓝紫光LD,高温、高频、高功率电子器件,高场高功率电力电子器件第三节半导体的分类i.Diamond-typesemiconductors•C(diamond),Si,Ge,-allinthefourthcolumnoftheperiodtable.ii.GroupIII-Vcompounds•GaAs,InSb,GaP,InAs,GaSb,etc.•Sonamedbecauseeachcontainstwoelements,onefromthethirdandtheotherfromthefifthcolumnoftheperiodictable.iii.GroupII-VIcompounds•ZnS,CdS,etc.iv.GroupIV-IVcompounds•SiC.v.IIInitridesWhichMaterialsAre“Semiconductors”?ResistivitiesAreIntermediate(“Semi”)MaterialResistivityinΩcmMetalsCopper1.7x10-6SemiconductorsSilicon25GalliumArsenide104Germanium40SiliconCarbide10BoronCarbide0.5Fe3O410-2InsulatorsSiO2glass1014WhichMaterialsAreSemiconductors?“II-VI”CompoundS’c’s•ZnS2.6eV•CdTe1.45eV“III-V”CompoundS’c’s•GaAs1.4eV•InSb0.17eV•GaN3.1eVElementalSemiconductors•Si1.1eV•Ge0.67eV2sBandOverlappingenergybandsElectrons2s2p3s3p1s1sSOLIDATOME=0FreeelectronElectronEnergy,E2pBand3sBandVacuumlevelInametalthevariousenergybandsoverlaptogiveasinglebandofenergiesthatisonlypartiallyfullofelectrons.Therearestateswithenergiesuptothevacuumlevelwheretheelectronisfree.?1999S.O.Kasap,Optoelectronics(PrenticeHall)第四节半导体的能带BandDiagramBandDiagramfor“Pure”SemiconductorsBandGapValuesforSomeTechnologicalSemiconductorsGapsareUsually2eVMaterialEg(eV)ne(m-3)Si1.10714x1015Ge0.6723x1018GaAs1.471.4x1012InSb0.1713.5x1021ValenceBandConductionBandPossibleElectronEnergyGapElectronenergy,EConductionBand(CB)Emptyofelectronsat0K.ValenceBand(VB)Fullofelectronsat0K.EcEv0Ec+(b)Bandgap=Eg(a)CovalentbondSiioncore(+4e)(a)AsimplifiedtwodimensionalviewofaregionoftheSicrystalshowingcovalentbonds.(b)TheenergybanddiagramofelectronsintheSicrystalatabsolutezerooftemperature.?1999S.O.Kasap,Optoelectronics(PrenticeHall)e–holeCBVBEcEv0Ec+EgFreee–hEgHoleh+Electronenergy,E(a)AphotonwithanenergygreaterthanEgcanexciteanelectronfromtheVBtotheCB.(b)EachlinebetweenSi-Siatomsisavalenceelectroninabond.WhenaphotonbreaksaSi-Sibond,afreeelectronandaholeintheSi-Sibondiscreated.h(a)(b)?1999S.O.Kasap,Optoelectronics(PrenticeHall)第五节.半导体的掺杂IntrinsicMaterial（本征）Aperfectsemiconductorcrystalwithnoimpuritiesorlatticedefectsiscalledanintrinsicsemiconductor.AtT=0K–NochargecarriersValencebandisfilledwithelectronsConductionbandisemptyAtT0Electron-holepairsaregeneratedEHPsaretheonlychargecarriersinintrinsicmaterialSinceelectronandholesarecreatedinpairs–theelectronconcentrationinconductionband,n(electron/cm3)isequaltotheconcentrationofholesinthevalenceband,p(holes/cm3).Eachoftheseintrinsiccarrierconcentrationsisdenotedni.Thusforintrinsicmaterialsn=p=niElectron-holepairsinthecovalentbondingmodelintheSicrystal.e–(a)As+xAs+As+As+As+EcEdCBEv~0.05eVAsatomsitesevery106SiatomsDistanceintocrystal(b)ElectronEnergy(a)ThefourvalenceelectronsofAsallowittobondjustlikeSibutthefifthelectronisleftorbitingtheAssite.Theenergyrequiredtoreleasetofreefifth-electronintotheCBisverysmall.(b)Energybanddiagramforann-typeSidopedwith1ppmAs.TherearedonorenergylevelsjustbelowEcaroundAs+sites.?1999S.O.Kasap,Optoelectronics(PrenticeHall)n型材料Thiscrystalhasbeendopedwithapentavalentimpurity.B–h+(a)xB–EvEaBatomsitesevery106SiatomsDistanceintocrystal~0.05eVB–B–B–h+VBEcElectronenergy(b)(a)BorondopedSicrystal.Bhasonlythreevalenceelectrons.WhenitsubstitutesforaSiatomoneofitsbondshasanelectronmissingandthereforeahole.(b)Energybanddiagramforap-typeSidopedwith1ppmB.ThereareacceptorenergylevelsjustaboveEvaroundB–sites.TheseacceptorlevelsacceptelectronsfromtheVBandthereforecreateholesintheVB.?1999S.O.Kasap,Optoelectronics(PrenticeHall)P型材料载流子的统计分布1允许的量子态按能量如何分布。2电子在允许的量子态中如何分布。半导体的基本性质敏感地依赖温度ECEv第六节状态密度()(1.1)dZgEdE导带和价带中有很多能级：相邻能级间隔：10-22eVE-E+dE内有dZ个量子态状态密度状态密度EcEv产生复合产生数==复合数ED在一定的温度下，→热平衡状态○●○●球形等能