《半导体工程专业英语》课件-1.1 Electrical Conductivity of Solids

微专业---半导体制造技术课程：半导体工程专业英语ContentsSemiconductorProperties半导体特性01SemiconductorMaterials半导体材料02SemiconductorDeviceandHowTheyareUsed半导体器件及其使用03ProcessTechnology工艺技术04FabricationProcesses制造工艺05SemiconductorMaterialsandProcessCharacterization半导体材料与工艺表征06SemiconductorProperties1.1ElectricalConductivityofSolids1.2ElectricChargeCarriers1.3SemiconductorsandExternalInfluences1.4SemiconductorsinNanoscale011

SemiconductorProperties1ChapterOverview

Thegoalofthischapteristoconsiderinqualitativetermsfundamentalpropertiesofsolidsknownassemiconductors.Thediscussionisnotmeanttobeastructuredoverviewofthephysicsofsemiconductors,butratherasimplifiedreviewaimedattheidentificationofthosepropertiesofthisclassofmaterialswhichareessentialtotheunderstandingoftheprinciplesuponwhichfunctionalsemiconductordevicesarebuiltandoperate./ˈkwɑːlɪteɪtɪv/定性的/ˈsɪmplɪfaɪd/简化的/sɛmikənˈdʌktərz/半导体器件2Introduction

Theextenttowhichasolidisabletoconductelectricityisacharacteristic

definingitsusefulnessintherangeofpracticalapplications.Inthissection

atomic-levelfeaturesdefiningelectricalconductivityofthesolidandatthe

sametimeareusedasacriteriaidentifyingaclassofmaterialsknownas

semiconductorsareconsidered./kraɪˈtɪriə/标准1

SemiconductorProperties

1.1ElectricalConductivityofSolids/əˈtɑːmɪk

/原子的3Text

Electricalconductivityσ,whichisaninverseofresistivityρ(ρ=1/σ)and

whichisdeterminedbytheatomicstructureofmaterials,representsability

ofmaterialtoconductelectricity.

Electronsareplayingaroleofelectriccharge

carriersinthesolid.Themainfactorcontrollingelectricalconductivityσofthesolidisanumberofelectronswhich

arefree./əˈtɑːmɪk/原子的1

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.1

Interatomicbandsandelectricalconductivity/ˈkæriərz/载流子4(a)

Schematicdepictionofanatomusing

siliconwith4electronsinthe

outermostshellMasanexample.

/ˈveɪlənsɪˈlektrɑːn/价电子/səˈfɪʃ(ə)nt/足够的/ˈbaɪndɪŋ/束缚的1

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.1

Interatomicbandsandelectricalconductivity

(b)valenceelectronacquiresenergysufficientto

overcomebindingenergyandtobecomeafreeconductionelectron.5(a)

separated.

1

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.1

Interatomicbandsandelectricalconductivity

(b)broughttogetherandformingcovalent

bonds.

Siliconatoms

(c)electronreleasedfromthecovalentbondleavingbehindpositivelycharge

holewhichisfreetomoveandtocarrypositivecharge./ˌkoʊˈveɪləntbɑːnz/共价键61

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.1

Interatomicbandsandelectricalconductivity

Figure

(a)

showstwoseparatedfromeachothersiliconatomsschematicallyrepresentedbypositivelychargedatom

coresand

fourvalenceelectronsassociatedwiththeouter-mostatomicshell.When

broughttoclosecontactatomswillformabondusingtwovalenceelectrons,

onefromeachatomparticipatinginthebond(Fig

(b)).Abondcreated

thiswayisreferredtoasacovalentbond.Toformcovalentlybondedlattice

allfourvalenceelectronsofanatomareusedtoformbondswithfourneighboringatomsleavingnofreeelectrons.Ameasurableenergyisrequiredto

breakacovalentbondandtoreleaseanelectronmakingitavailableforconduction(Fig

(c)).Materialsfeaturingcovalentbondsarenotexpected

tobegoodconductorsofelectricityandassucharecommonlyreferredto

assemiconductors./ˈveɪlənsɪˈlektrɑːnz/价电子71

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.1

Interatomicbandsandelectricalconductivity

Theresultoftheelectronbeingreleasedfromthecovalentbond(Fig

(c))isaleftbehind“hole”whichfeaturesthesameaselectron,

butpositiveelectriccharge.Similarlytotheelectron,theholecanmovein

semiconductorinthepresenceofelectricfield,andthus,canactasacarrier

ofthepositiveelectriccharge.

Siliconatoms电场81

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.2

Energybandstructureandelectricalconductivity

electricalconductivityofsolidsofinterestisthe

outermostsectionoftheenergybandstructureconsistingofvalencebands

andconductionbandsseparatedbytheenergygapasshowninFig

(a).

Theenergydifferencebetweenedgesoftheconduction(Ec)andvalence

(Ev)bandsisameasureoftheenergygapwidthEgalsoreferredtoasa

bandgapwidth.EnergybandText/kənˈdʌkʃnbænd/导带带隙91

SemiconductorProperties

1.1ElectricalConductivityofSolids1.1.2

Energybandstructureandelectricalconductivity

Letusconsidernowsolidswhichfeaturevalencebandscompletelyfilled

withelectrons(Fig

(a)).Here,thevalenceelectronshavetoovercomethe

energygapinordertobecomeconductionelectrons.Otherwise,considering

completelyoccupiedvalencebands,no“tiedup”valenceelectroncancarry

electricalcurrent.Inconsequence,theenergyinexcessofEg,orinother

wordshighenoughtobreakinteratomicbondsandreleasevalenceelectrons,

hastobesuppliedtothesolidtomakeitelectricallyconductive.Following

thisreasoningthevalueofEgcanbeusedasameasuredefiningabilityof

varioussolidstocarryelectriccurrent.Dependingonthesolid,theenergygapwidthmayvaryfrom0eVformetals(Fig(b))toashighas10eVforinsulatorswhereelectronvolt(eV)isaunitofenergyuniversallyadoptedinsemiconductorterminology./ˌtɜːrmɪˈnɑːlədʒi/术语/ˌɪntərəˈtɑːmɪk/原子间的价带10