《电子陶瓷》PPT课件

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1、p-njunctionsElectronsandHolesInanintrinsicS.Mlikesiliconattemperaturesaboveabsolutezero,therewillbesomeelectronswhichareexcitedacrossthebandgapintoC.VandwhichcanproducecurrentWhentheelectroninpuresiliconcrossesthegap,itleavesbehindanelectronvacancyor"hole"intheregularsiliconlatticeUnderth

2、einfluenceofanexternalvoltage,boththeelectronandtheholecanmoveacrossthematerialInann-typesemiconductor,thedopantcontributesextraelectrons,dramaticallyincreasingtheconductivityInap-typesemiconductor,thedopantproducesextravacanciesorholes,whichlikewiseincreasetheconductivityP-andN-typeS.MBa

3、ndsforDopedSemiconductorsTheapplicationofbandtheoryton-typeandp-typesemiconductorsshowsthatextralevelshavebeenaddedbytheimpurities.Inn-typematerialthereareelectronenergylevelsnearthetopofthebandgapsothattheycanbeeasilyexcitedintotheconductionband.Inp-typematerial,extraholesinthebandgapall

4、owexcitationofvalencebandelectrons,leavingmobileholesinthevalenceband.P-njunctionTheopencirclesontheleftsideofthejunctionaboverepresent"holes"ordeficienciesofelectronsinthelatticewhichcanactlikepositivechargecarriers.Thesolidcirclesontherightofthejunctionrepresenttheavailableelectronsfrom

5、then-typedopant.Nearthejunction,electronsdiffuseacrosstocombinewithholes,creatinga"depletionregion".TheenergylevelsketchaboverightisawaytovisualizetheequilibriumconditionoftheP-Njunction.Theupwarddirectioninthediagramrepresentsincreasingelectronenergy.Completep-njunctionAp-njunctioninther

6、malequilibriumwithzerobiasvoltageapplied.Electronsandholesconcentrationaredrawnrespectivelywithblueandredlines.Grayregionsarechargeneutral.Lightredzoneispositivelycharged.Lightbluezoneisnegativelycharged.Theelectricfieldisshownonthebottom,theelectrostaticforcebuildingbetweenelectronsandho

7、lesandthedirectioninwhichthediffusiontendstomoveelectronsandholes.DepletionRegionWhenap-njunctionisformed,someofthefreeelectronsinthen-regiondiffuseacrossthejunctionandcombinewithholestoformnegativeions.Insodoingtheyleavebehindpositiveionsatthedonorimpuritysites.Dep