《半导体工程专业英语》课件-1.2 Electric Charge Carriers

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06SemiconductorProperties1.1ElectricalConductivityofSolids1.2ElectricChargeCarriers1.3SemiconductorsandExternalInfluences1.4SemiconductorsinNanoscale0111Introduction

Toallowelectricalconductivity,freetomovearoundcarriersofanelectric

chargemustbeavailableinthebodyofthesolid.Concentrationofcharge

carriers(numberofcarrierspercm3),thewaytheyaregenerated,andthe

mechanismoftheirtransportacrossthesolidplaythekeyroleindefining

electricalconductivityofanysemiconductormaterial./ˈmekənɪzəm/机制1

SemiconductorProperties半导体特性

1.2ElectricChargeCarriers载流子12TextTherearetwotypesofelectricchargecarriersinsemiconductors:electronscarryingelementarynegativechargeq

(q=1.602×10−19

coulombs),andholeswhichcarrythesamecharge,but

positive.Semiconductorsinwhichconcentrationofelectronsnexceedsconcentrationofholesp(n>>p)arereferredtoasn-type

semiconductors.Inthesamewaysemiconductorsinwhichconcentrationof

holespexceedsconcentrationofelectrons(p>>n)arereferredtoasp-type

semiconductors./ˈkuːloʊm/库仑1

SemiconductorProperties半导体特性

1.2ElectricalConductivityofSolids固体的导电性1.2.1

Electronsandholesascarriersofelectriccharge电子与空穴

13

Tomakeanygivensemiconductorn-typeorp-type,properlyselectedalienelementsneedtobeaddedtothehost

semiconductor.Theprocessisknownasdopingandalienelementsadded

arereferredtoasdopants(sometimestermimpuritiesisusedinstead).Infact,onedopantatompermillionhostatomsisenoughto

observenoticeablechangesinsemiconductor’sconductivitytypen,orp.1

SemiconductorProperties半导体特性

1.2ElectricalConductivityofSolids固体的导电性1.2.1

Electronsandholesascarriersofelectriccharge电子与空穴

【Controlofconductivitybydoping】/hoʊst/宿主141

SemiconductorProperties半导体特性

1.2ElectricalConductivityofSolids固体的导电性1.2.1

Electronsandholesascarriersofelectriccharge电子与空穴

【Controlofconductivitybydoping】Illustrationof(a)n-typedoping(donors),(b)p-typedoping(acceptors).15

Selectionofdopantatomsisbasedonthenumberofvalanceelectrons

featuredbythehostatoms.Ifforexamplethehostatomsfeaturefour

valanceelectrons,thentheelementswithfivevalanceelectrons

needstobeintroducedintothelatticetoaddfreeelectronsandmakehost

materialn-type.Dopantatomsarereferredtoasdonorsinthiscaseand

theirconcentrationisdenotedasND.Inthecourseofthedopingprocessa

dopantatomsubstitutesforthehostatominthelatticethenusesitsfour

electronstoformcovalentbondwithadjacenthostatomsleavingonefreeelectronreadytoactasachargecarrier(Fig(a)).Undertheequilibriumconditionconcentrationofelectronsinn-typesemiconductorn=ND>>p

andelectronsareactingasmajoritycarriers.1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.1

Electronsandholesascarriersofelectriccharge/ˌiːkwɪˈlɪbriəm/平衡/əˈdʒeɪs(ə)nt/邻近的/məˈdʒɔːrəti/大多数/ˈlætɪs/晶格16

Inordertomakehostmaterialp-typeratherthann-type,dopantatoms

featuringthreevalanceelectronsareused.Inthiscase,inordertoform

acovalentbondwithadjacentatomsinthelatticedopantatomneedsto

acceptanelectronfromtheexistingbondsleavingbehindaholewhichis

freetomovearoundandtocontributetoelectricalconductivityofthehost

materialandmakingitp-type(Fig

(b)).1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.1

Electronsandholesascarriersofelectricchargep-typedoping(acceptors)17Text1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.2

Generationandrecombinationprocesses(a)Generationoftheelectron-holepairasaresultofband-to-bandgeneration.

(b)annihilationoftheelectron-holepairasaresultofband-to-band

recombination./əˌnaɪəˈleɪʃ(ə)n/湮没18

Generationandrecombinationprocessesarecontrollingtheavailabilityof

freechargecarriersinsemiconductors.Generationistheprocessoffree

chargecarriersformationinsemiconductorsresultingfromtheelectronacquiringenergyfromoutsideoftheatom,forinstancethermalenergyor

energyoflight.Theenergysuppliedtosemiconductorneedstobesufficient

toovercomeenergygapandtoallowelectron’stransitionfromthevalence

bandwhereitcannotmove,totheconductionbandwhereitcanmove,

andthus,contributetotheelectricalconductivityofthesolid.Anoutcome

oftheprocessisanemptystateleftinthevalancebandknownasahole

(Fig

(a)).1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.2

Generationandrecombinationprocesses结果19

Theprocessofrecombinationisoppositetogenerationandresultsinthe

annihilationoftheelectron-holepairbyelectronsreleasingenergyequivalent

totheenergygapEgandtransitioningfromtheconductiontothevalance

bandwheretheyrecombinewithholes.1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.2

Generationandrecombinationprocessesrecombinationprocess/əˌnaɪəˈleɪʃ(ə)n/湮没20Text1

SemiconductorProperties

1.2ElectricalConductivityofSolids1.2.3

Chargecarriersinmotion【Char