光导率.pdf

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1、LEYBOLDSolid-StatePhysicsPhysicsConductionphenomenaLeafletsP7.2.3.1PhotoconductivityRecordingthecurrent-voltagecharacteristicsofaCdSphotoresistorObjectsoftheexperimentsMeasuringthephotocurrentIPhasafunctionofthevoltageUataconstantirradianceF.MeasuringthephotocurrentIPhasafunction

2、oftheirradianceFataconstantvoltageU.PrinciplesPhotoconductivityistheeffectofincreasingelectricalSemiconductorresistorsthatdependontheirradianceconductivitysinasolidduetolightabsorption.Whenthe(photoconductivecells)arebasedonthisprinciple.Theyhaveso-calledinternalphotoeffecttakesp

3、lace,theenergyab-openedupawidefieldofapplicationsandare,amongothersorbedenablesthetransitionofactivatorelectronsintothethings,employedintwilightswitchesandlightmeters.Theconductionbandandthechargeexchangeoftrapswithholessemiconductormaterialsmostcommonlyusedarebeingcreatedintheva

4、lenceband.Therefore,thenumberofcadmiumcompounds,particularlyCdS.chargecarriersinthecrystallatticeand,asaresult,theIntheexperiment,aCdSphotoresistorisexposedtolightfromconductivityareenhanced:alamp.TheirradianceFatthepositionofthephoto-Ds=Dp×e×mp+Dn×e×mn(I)resistorbeingvariedbymea

5、nsoftwopolarizationfilterswhichareplacedonebehindtheother.Ifthetwopolarizationplanese:elementarychargeofthefiltersarerotatedagainsteachotherbytheanglea,theDp:changeoftheholeconcentrationirradianceisDn:changeoftheelectronconcentrationmp:mobilityoftheholesF=F0×D×cos2a(III)mn:mobili

6、tyoftheelectronsF0:irradiancewithoutpolarizationfilters,WhenavoltageUisapplied,thephotocurrentisD:transparencywhenthepolarizationplanesareparallelAThephotocurrentisstudiedasafunctionofthevoltageIPh=×Ds×U(II)appliedtothephotoresistorataconstantirradiance(current-dvoltagecharacteri

7、stic)andasafunctionoftheirradianceataA:crosssectionofthecurrentpathd:distancebetweentheelectrodesconstantvoltage(current-irradiancecharacteristic).0209-WitModelofanidealphotoconductor:electron-holepairsareproducedthroughoutthecrystalbytheexternallightsourceandundergorecombination

8、.Electronsleavingthecrystalattheelectrod