Workingprinciple
Theavalanchephotodiodeisap-njunctionphotodetectiondiode,whichusestheavalanchemultiplicationeffectofcarrierstoamplifythephotoelectricsignaltoimprovethedetectionsensitivity.ItsbasicstructureoftenadoptstheReaddiodestructurewhichispronetoavalanchemultiplicationeffect(ieN+PIP+typestructure,P+sidereceiveslight),andalargereversebiasisappliedduringoperationtomakeitreachtheavalanchemultiplicationstate;itslightabsorptionThezoneisbasicallythesameasthemultiplicationzone(thePzoneandtheIzonewithhighelectricfield).
ThePNjunctionisappliedwithasuitablehighreversebiasvoltage,sothatthephotogeneratedcarriersinthedepletionlayerareacceleratedbyastrongelectricfieldtoobtainhighenoughkineticenergy,andtheycollidewiththelatticetoionizeandgeneratenewelectrons.Holepairs,thesecarrierscontinuetocausenewimpactionization,resultingincarrieravalanchemultiplicationandcurrentgain.Inthe0.6-0.9μmband,siliconAPDhasclosetoidealperformance.InGaAs(IndiumGalliumArsenide)/InP(IndiumPhosphorus)APDisanidealphotodetectorforlong-wavelength(1.3μn,1.55μm)opticalfibercommunication.ThelightabsorptionlayerusesInGaAsmaterial,whichhasahighabsorptioncoefficientforlightof1.3μmand1.55μn.InordertoavoidthetunnelbreakdownoftheInGaAshomojunctionbeforetheavalanchebreakdown,theavalanchezoneandtheabsorptionzoneareseparated,thatis,thePNjunctionismadeIntheInPwindowlayer.SincetheholeionizationcoefficientintheInPmaterialisgreaterthantheelectronionizationcoefficient,n-typeInPisselectedfortheavalanchezone.Thereisalargevalencebandbarrierattheheterogeneousinterfacebetweenn-InPandn-InGaAs,whichiseasytocausethecollapseofphoto-generatedholes,whichissandwichedbetweenEntertheInGaAsP(IndiumGalliumArsenidePhosphorus)transitionzonewithagradualbandgaptoformaSAGM(absorption,gradingandmultiplicationrespectively)structure.
InAPDmanufacturing,itisnecessarytoaddaprotectiveringonthesurfaceofthedevicetoimprovethereversewithstandvoltageperformance;thesemiconductormaterialispreferablySi(widelyusedtodetectlightbelow0.9um),butinthedetectionForlong-wavelengthlightabove1um,GeandInGaAsarecommonlyused(largernoiseanddarkcurrent).ThedisadvantageofthistypeofAPDisthatthereisaprocessoftunnelingcurrentmultiplication,whichwillproducelargershotnoise(reducingthep-zonedopingcanreducethetunnelingcurrent,buttheavalanchevoltagewillincrease).Animprovedstructureistheso-calledSAM-APD:themultiplicationzoneusesamaterialwithawiderbandgap(sothatitdoesnotabsorblight),andthelightabsorptionzoneusesamaterialwithanarrowbandgap;here,becauseoftheuseofheterojunction,youcanReducethedopingconcentrationofthemultiplicationregionwithoutaffectingthelightabsorptionregion,sothatthetunnelcurrentcanbereduced(ifitisamutationheterojunction,becauseoftheexistenceofΔEv,thephoto-generatedholeswillbeaccumulatedandaffectthedevice'sperformance.Responsespeed,atthistime,agradualchangelayercanbeinsertedinthemiddleofthemutationheterojunctiontoreducetheinfluenceofΔEv).
Основни характеристики
Основни характеристики①Коефициент на печалба от лавина M (наричан още коефициент на умножение), за внезапни промени
Във формулата,Visима обратно напрежение на отклонение,иVBisthebulkavallanchearuptionvoltage;е свързано сматериала,
структура на устройството и падаща дължина на вълната и т.н. Тя е постоянна и стойността й е 1～3.②Продукт на честотната лента на усилването, когато усилването е голямо и честотата е висока,
M(ω)·ω
whereωistheangularfrequency;NisConstant,whichchangesslowlywiththeratiooftheionizationcoefficient;Wisthethicknessofthedepletionzone;Vsisthesaturationvelocity;αnandαparetheionizationcoefficientsofelectronsandholes,respectively,andthegainbandwidthproductisaconstant.Togetahighproduct,youshouldchoosealargeVs,asmallW,andasmallαn/αp(thatis,thedifferenceintheionizationcoefficientsofelectronsandholesshouldbelarge,andcarrierswithhigherionizationcoefficientsshouldbeinjectedintotheavalanchezone).③ExcessivenoisefactorF.Intheprocessofmultiplication,thenoisecurrentincreasesfasterthanthesignalcurrent.UseFtodenotethenoiseadditionF≈Mxcausedbytheavalancheprocess.Wherexistheexcessnoiseindex.ItisnecessarytoselecttheappropriatevalueofMtoobtainthebestsignal-to-noiseratioandmakethesystemreachthehighestsensitivity.④Temperaturecharacteristics,thecarrierionizationcoefficientdecreaseswiththeincreaseoftemperature,whichleadstothedecreaseofthemultiplicationfactorandtheincreaseofthebreakdownvoltage.ThetemperaturecoefficientofbreakdownvoltageisusedtodescribethetemperaturecharacteristicsofAPD.
β=
Във формулата VB и VB0 са напрежението на пробив, когато температурата е T и T0, съответно.
Whenusing,thetemperatureoftheworkingpointshouldbecontrolled,andauniformP-Njunctionshouldbemadetopreventthelocaljunctionsurfacefrombeingbrokendown.
Материал
Теоретично всеки полупроводников материал може да се използва в зоната на умножение:
Siliconmaterialissuitableforthedetectionofvisiblelightandnear-infraredlight,andhasrelativelyhighLowmultipliernoise(excessnoise).
Германиевият (Ge) материал може да открие инфрачервена светлина с дължина на вълната, която не надвишава 1,7 μm, но шумът от умножаване е сравнително голям.
InGaAsmaterialscandetectinfraredrayswithwavelengthsexceeding1.6μm,andthemultiplicationnoiseislowerthanthatofgermaniummaterials.Itisgenerallyusedasthemultiplicationregionofheterostructurediodes.Thismaterialissuitableforhigh-speedopticalfibercommunication,andthespeedofcommercialproductshasreached10Gbit/sorhigher.
Galliumnitridediodescanbeusedforultravioletdetection.
HgCdTediodescandetectinfraredrayswithawavelengthofupto14μm,buttheyneedtobecooledtoreducedarkcurrent.Usethisdiodetoobtainverylowexcessnoise.
Basicintroductionandapplicationrangeofbasicmodels
Eachmoduleincludesaphotodetector(fastphotodiodeoravalanchephotodiode)andatransimpedanceamplifier.Amplifierandphotodetectorarecombinedinthesamepackage,sothattheenvironmentalnoiseislowerandtheparasiticcapacitanceissmaller.
C30659seriesmodulesincludeanAPDconnectedtoalownoisetransimpedanceamplifier.Thereare4typesofsiliconcrystalavalanchephotodiodesand2typesofindiumgalliumarsenideavalanchephotodiodestochoosefrom.Thestandardbandwidthof50MHzand200MHzcanbeadaptedtoawiderangeofapplications.TherearealsotwoC30659modelsofavalanchephotodiodesequippedwiththermoelectriccooling(LLAMseries)tohelpimprovenoiseorkeeptheavalanchephotodiodesworkingataconstanttemperatureunderanyambienttemperature.
C30659modelcanchooseacustomizedbandwidthorcustomizedproductssuitableforspecialenvironmentalrequirementsaccordingtospecialapplicationneeds.Thereisalsoa14-pindualin-lineplug-inwithapigtailpackage,whichcanachievealmost100%couplingefficiency.
C30950EHisalow-costproductthatcanreplaceC30659.Theamplifierisusedtooffsettheinputcapacitanceofthevoltagegainamplifier.C30919EandC30950EHusethesamedesignstructure,withanadditionalhigh-voltagetemperaturecompensationcircuittomaintainthemodule'sresponsivenessconstantinawidetemperaturerange.TheothertwoHUVmodulescanbeusedforlowfrequencyandhighgainapplications,whichcoverawidespectrumfromultraviolettonearinfrared.
Характеристики и предимства
·Ултра-нисък шум·Висока скорост·Висок трансимпеданс
Общи модели: C30659-900-R5BH, C30659-900-R8AH, C30659-1060-R8BH, C30659-1060-3AH
C30659-1550-R08BH,C30659-1550-R2AH,C30919E,C30950EH,LLAM-1550-R2A,LLAM-1060-R8BH
HUV-1100BGH,HUV-2000BH
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Приложение
·Лазерен далекомер·Конфокална микроскопска инспекция·Видеосканиращ имидж·Инструмент за високоскоростен анализ·Комуникация в свободно пространство
·Ултравиолетов сензор·Разпределен температурен сензор