半导体光电材料课件.ppt

半導體光電材料1

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WhatIsaSemiconductor???????????????????????????????????????????????????????????????????????????????????????????????????????????????

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Manymaterials,suchasmostmetals,allowelectricalcurrenttoflowthroughthemTheseareknownasconductorsMaterialsthatdonotallowelectricalcurrenttoflowthroughthemarecalledinsulatorsPuresilicon,thebasematerialofmosttransistors,isconsideredasemiconductorbecauseitsconductivitycanbemodulatedbytheintroductionofimpurities

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SemiconductorsAmaterialwhosepropertiesaresuchthatitisnotquiteaconductor,notquiteaninsulatorSomecommonsemiconductorselementalSi-Silicon(mostcommon)Ge-GermaniumIII-VcompoundsGaAs-GalliumarsenideGaP-GalliumphosphideAlAs-AluminumarsenideAlP-AluminumphosphideInP-IndiumPhosphide5

SomecommonsemiconductorsII-VIcompoundsZnSCdSZnSeCdSeZnOOrganiccompoundsconjugatedmoleculesSemiconductors6

CrystallineSolidsInacrystallinesolid,theperiodicarrangementofatomsisrepeatedovertheentirecrystalSiliconcrystalhasadiamondlattice7

CrystallineNatureofSiliconSiliconasutilizedinintegratedcircuitsiscrystallineinnatureAswithallcrystallinematerial,siliconconsistsofarepeatingbasicunitstructurecalledaunitcellForsilicon,theunitcellconsistsofanatomsurroundedbyfourequidistantnearestneighborswhichlieatthecornersofthetetrahedron8

What’ssospecialaboutSilicon?CheapandabundantAmazingmechanical,chemicalandelectronicpropertiesThematerialisverywell-knowntomankindSiO2:sand,glassSiiscolumnIVoftheperiodictableSimilartothecarbon(C)andthegermanium(Ge)Has3s2and3p2valenceelectrons9

NatureofIntrinsicSiliconSiliconthatisfreeofdopingimpuritiesiscalledintrinsicSiliconhasavalenceof4andformscovalentbondswithfourotherneighboringsiliconatom