半导体材料与技术课件：chapter4-1（第一章）

Chapter4Semiconductordevices4.1Idealpnjunction4.2pnJunctionBandDiagram4.3BipolarTransistor4.4JunctionFieldEffectTransistor4.5MetalOxideSemiconductorFieldEffectTransistor4.6LightEmittingDiodes4.7SolarCellsFromPrinciplesofelectronicMaterialsDevices,SOKasap(McGraw-Hill,2005)4.1Idealpnjunction4.1Idealpnjunction4.1Idealpnjunction4.1Idealpnjunction4.1Idealpnjunction4.1IdealpnjunctionConsideringanabruptpnjunction:ρnet(x)cansimplybedescribedbystepfunctionsshowninFig.(d).Usingthestepformofρnet(x)inFig.(d)intheintegrationofgivestheelectricfieldatM.IntegratetheexpressionforE(x)inFig.(e)toevaluatethepotentialV(x)andthusfindV0byputtinginx=Wn.W0=Wn+Wp,isthetotalwidth

ofthedepletionregionunderazeroappliedvoltage.ThesimplestwaytorelateV0tothedopingparametersistomakeuseofthefactthatinthesystemconsistingofp-andn-typesemiconductorsjoinedtogether,inequilibrium,Blotzmannstatisticsdemandsthattheconcentrationsn1andn2ofcarriersatpotentialenergiesE1andE2arerelatedbyConsideringelectrons(q=-e),weseefromFig.(g)thatE=0onthepsidefarawayfromMwheren=npo,andE=-eVoonthen-sideawayfromMwheren=nno.ThusWhichmeanthatVodependsonnnoandnpoandhenceonNdandNa.ThecorrespondingequationforholeconcentrationsisclearlyRearrangingAndWeobtainWecannowwriteppoandpnointermsofthedopantconcentrationsinasmuchasppo=NaandForwardbias:diffusioncurrentForwardbias:diffusioncurrentForwardbias:diffusioncurrent(b)Forwardbias:diffusioncurrent(b)Forwardbias:diffusioncurrentLawofthejunctionisanimportantequationthatwe(b)Forwardbias:diffusioncurrent(b)Forwardbias:diffusioncurrent(b)Forwa