光电子作业答案.ppt

Condition:asiliconphotoconductorat300KBackgrounddoping,Electronmobility,Holemobility,Electronlifetime,Holelifetime,Detectorarea,Detectorlength,Biasvoltage,Gernerationrate,2.10,Calculation:a)darkcurrent;b)theexcessconcentration;c)thephotoconductivity;d)thedevicegain.,Solution:a)Thedarkcurrentisgivenby,sothedarkcurrentis,=,=,b)Theexcesscarrierdensityis,c)thephotoconductivityis,d)Thegainofthephotoconductivedetectoris,where,So,2.13Condition:aGaAsp-i-ndetectorwithIntrinsiclayerwidth,Opticalpowerdensity,Photonenergy,Absorptioncoefficient,Devicearea,Calculation:thepromptphotocurrentofthedevice.,Solution:Thephotonfluxincidentonthedetectoris,Thephotocurrentis,2.16Condition:AnavalanchephotodetectorwithAvalancheregionwidth,Theimpactionizationcoefficient,Calculation:ThemultiplicationfactorSolution:ThemultiplicationfactorfromEqn.(2.66)is,3.8Condition:aGaAsp-n+junctionLEDwithElectrondiffusioncoefficient,Holediffusioncoefficient,n-sidedoping,p-sidedoping,Electronminoritycarrierlifetime,Holeminoritycarrierlifetime,Calculation:injectionefficiencyoftheLEDassumingnorecombinationduetotraps.,Solution:Theelectronminoritycarrierdensityinp-sideis,Andholeminoritycarrierdensityinn-sideisgivenby,Thediffusionlengthare,Theinjectionefficiencyis(assumingnorecombinationduetotrap),3.9Thediodeinproblem3.8isusedtogenerateanopticalpowerof1,thediodeareais1,andtheexternalefficiencyis20。Calculation:theforwardbiasvoltagerequired.,Solution:Thephotonsgeneratedpersecondare,Whicharealsoexpressedby,Sothecurrentrequiredtogeneratethephotonsis,thecurrentwhenthediodeisforwardbiasisgivenby,SolvingtheaboveequationforVyields,3.12Condition:aGaAsLEDcoupledtoanopticalfiberwithRefractiveindexforthecorelayer,Refractiveindexforthecladdinglayer,Calculation:themaximumangleofacceptanceforthefiberandthecouplingefficiencyforthediodeSolution:Themaximumangleofacceptanceiscalculatedby,Thecouplingefficiencyis,Example3.7=32.6o=0.29,3.15Condition:AnAlGaAs/GaAsheterojunctionLEDat300KwithInjectiondensityforelectrons,Injectiondensityforholes,BandgapofGaAs,Calculation:thepositionofemissionpeak;theshiftinthepeakpositioniftheinjectiondensityincreasedto,Solution:Fromtherelationship,forinjectiondensityof,thepeakpositionishalfoflinewidthatthebandedge,forinjectiondensityof,Shiftofthepeakposition,3.18Condition:aheterojunctionLEDbasedonGaAsat300KwithBiascurrentdensity,Thewidthoftheactivelayer,Calculation:the3dbcutofffrequencyofthediode.Solution:the3dbcutofffrequencyis,isrelatedtobiascurrentdensityby,Thus,FromFig.3.6(p140),Sothe3dbcutofffrequencyiscalculatedas,3.21Condition:AGaAsLEDwithOutputpower,Themaximumdevicearea,Theefficiencyofthedevice,Themaximuminjectiondensity,Calculation:thethicknessoftheactiveregionneeded.Solution:theopticalpowerdeliveredbythedeviceis,where,(=bandgapofGaAs)and,(when),Solvingtheaboveequationfordyields,4.1Condition:aGaAslaserwithCavitylength,Bandgap,Calculation:thenumberofallowedlongitudinalmodesinanenergywidth,.Solution:thefrequencyoftheresonantlongitudinalmodesis,Whereqisaninteger.,Thustheenergyofthesemodesis,Thenumberofallowedlongitudinalmodesinanenergywidth,is,4.3Condition:aFabry-PerotcavitywithLength,Mirrorreflectivity,Absorptionlosscoefficient,Refractiveindex,Calculation:thephotonlifetime,Solution:thecavityloss,is,Thephotonlifetimeinthecavityisgivenby,So,4.8Condition:twoGaAs/AlGaAsdoubleheterostructurelasersarefabricatedwithActiveregionthickness,Opticalconfinementfactors,Carrierinjectiondensityneedtocauselasing,Radiativerecombinationtime,Calculation:thethresholdcurrentdensitiesforthetwolasers.Solution:thethresholdcarrierinjectiondensitiesforthetwolasersare,(forboth),Sothethresholdcurrentdensitycanbecalculatedby,asforthetwolasermentionedabove,thethresholdcurrentdensities,forthefirstlaser,forthesecondlaser.,5.1Condition:AGaAs/AlGaAslaserwithThresholdcurrentdensity,Switchpeakcurrentdensity,Carrierlifetime,Calculation:thedelaytimebeforephotonemission.Solution:Thedelaytimeisgivenby,11.2Condition:A1.55,quantumwelllaserwithThresholdcarrierdensity,Radiativelifetime,Augercoefficient,Activ