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1、Chapter1OpticalPropertiesofSemiconductors半导体光学特性一复折射率的实，虚部的意义：Refractiveindexnrn=c/v=(弗i曾)1/2=n+inrrrTherealpartofindexnrospeedoflightTheimaginarypartofindexnroattenuationoflight二折射率与增益吸取系数的关系：AbsorptioncoefficientaTheabsorptioncoefficientaisdescribedbytheabsorptionoftheintensity.dI=I(-a)e-azdz,0a=I
2、dz传播单位距离相对光强的吸取量。量纲：/cm.三电子与光子相互作用遵守能量与动量守恒：表达式：课件1-1P16,17图：失去一个光子(光子被电子吸取)，得到动量转变，光子数减一，能量从光场转变到电场，满足能量，动量守恒。Aschematicofanabsorptionprocesswhereaphotonisabsorbed(destroyed)andtheenergyandmomentumoftheelectronisaltered;theemissionofaphotonwhereaphotoniscreated.P18,Bandtobandabsorptionandemissionin
3、semiconductors.Anelectroninthevalencebandabsorbsaphotonandmovesintotheconductionband;Inthereverseprocessanelectronintheconductionbandemitsaphotonandmovesverticallydownintothevalenceband.DirectInterbandTransitions力2k2心(EC-EV)+2（丄+丄）m*em*h枸一Eg力2k211亍(一+一)2m*m*ehReducedehmass（折合质量）一Theinteractioncancau
4、seabsorptionor2一*emissionofphotons.Theabsorptionprocessisproportionaltothephotondensitynph比较本征吸取与非本征吸取的条件，类型：Conditions:本征吸取：光子能量大于材料带隙；非本征吸取：光子能量小于材料带隙。intrinsicabsorption（本征吸取）：directabsorption直接吸取）indirectabsorption（间接吸取）extrinsicabsorption（非本征吸取）：Excitonabsorption（激子吸取）,interbandabsorption（带内吸取）
5、，impurityabsorption（杂质吸取）本征吸取中的直接,间接吸取的不同点：intrinsicdirectindirectIndirectgapsemiconductors,theelectrontransitionsareverticalink-space,duetomomentumconservation.Indirectbandgaptransition：phonon/impuritiesassistedtransitions,secondorderprocess,notverticalinkspace,mediatedbyaphononinteraction.Theratea
6、requitesmall,comparedtotheratesfordirectgapsemiconductors.光电子器件相对电子器件的优缺点：Thedisadvantageofelectronicdevices（a）metallicinter-connectslimittheinter-connectivityofthedevices;（b）difficulttotransmitinformationoververylongdistances（c）externalelectromagneticinterference（EMI）effects（d）chargedparticlesscatt
7、eringprocessSpecialfeaturesofoptoelectronicdeviceswhichmakeopticsanattractivemediumforinformationprocessing1Immunitytoelectromagneticinterference2Non-interferenceoftwoormorecrossedbeams3Highparallelism4Highspeed-highbandwidthTheconditionforinversionwhentheemissionandabsorptioncoefficientsbecomeequal
8、.Undersuchconditionstheelectron-holepairscouldrecombineandemitmorephotonsthancouldbeabsorbed.Thegainofthematerialistheemissioncoefficientminustheabsorptioncoefficient.tdependsuponimpuritydensityNnrttrapcaputurecross-sectionccnpelectronthermalvelocityvth（m*v2=kT）2th2B1Tn=nrNvctthn1Tp=nrNvctthpI(z)=Ie
9、gz02m*rh2k2Ee=E+=Ec2m*ceh2k2Eh=E-=Ev2m*vhh2k2hw-E-hkg+m*(hw-e)m*ge-m*(hw-e)m*ghTheAugerprocessinvolving2electronsand1holeintheinitialstateand1holeelectronafterthescattering.TheprocesswheretwoholesandanelectronsufferanAugerprocessandgiveahotholeinthesplit-offband.111+-TTTnrnrL：DtpYppDiffusionlengthre
10、presentsthedistanceoverwhichtheinjectedcarrierdensityfallsto1/eofitsoriginalvalue.Italsorepresentstheaveragedistanceanelectronwilldiffusebeforeitrecombineswithahole.Chapter2OptoelectronicDetectors光电子检测器221直接吸取系数，间接吸取系数的表达式及量级Thedirectabsorptioncoefficient(直接吸取系数)agN(he)1naA(he-E)2gAisaconstant,relat
11、edtothestructureofenergyband.Fordirectabsorption,aisabout104106cm-1Theindirectabsorptioncoefficient(间接吸取系数)a(he)-【K+K(T)(he-E)2in01gKisaconstant,0K(T)isatemperaturedependentfactor.1Forindirectabsorption,aisabout100103cm-1222截止波长的计算Forintrinsicabsorption,theessentialcondition(本征吸取的必要条件)hohu二Ecgucutof
12、ffrequency(截止频率)hc1.24九=一=二(ym)cutoffwavelength(截止波长)cEE(eV)gg223吸取厚度与吸取光功率之间的关系，对吸取层厚度的要求Thelengthofthesamplemustbesuitable.P（0）:IncidentPower（入射功率）opP=P(L)=e-Lp(o)：TransmissionPower(透射功率)topopP=P(0)一P=1-e-olaboptP(0)：AbsorptivePower(吸取功率)op1StrongabsorptionnloInLTo1Whendirectabsorptiono103cm-inL10
13、ym(1020ym)SiSioo104cm-1GenLGelymo(only1ym)224载流子产生率，响应度，量子效率，表达式及概念Rateofe-hpairgeneration、ResponsivityandQuantumefficiencyRateofe-hpairgeneration（电子空穴产生率）Thepoweratpointx:P(x)=P(0)e-oxopopTheenergyabsorbedpersecondperunitareabetweenxtx+dxP(x+dx)P(x)opop=P(0)e-oxodx=P(x)odxopopGisthecarriergeneratio
14、nperunitvolumepersecondrp(x+心)-popopAxG=lim-LAxt0oP(x)G=op=oJ(x)LhphJ(x)isthephotonfluxdensityimpingingatpointx(光子流密度)phResponsivityR（响应度）phphoton（hoE）ne-hpairgphotocurrentILPhotocurrentdensityJLQuantumefficiency耳（量子效率）Qistheratiobetweenthecarrierscollectedandphotonsimpingingonthedetector.ophohophe=
15、Pb=1-e-如Popr=n上phQhon九（ym）Q1.24225光电检测器的工作过程Tocollecttheelectron-holepairsgeneratedbylightoneneedsanelectricfield.Thiscanbegeneratedbyeithersimplyapplyingabiasacrossanundopedsemiconductororbyusingap-ndiode.226光电检测器的偏置状态（反偏）231如何选择衬底Howtochoosethesubstratematerialsforopticaldetectors?Thechoiceofsemiconductormaterialsfordetectorsislimitedtothosewhichhaveagoodlatticematchingwiththeaforementionedsubstrates.Insomecasesitispossibletogrowalatticemismatchedepitaxiallayerandcausedislocationstobetrappe
