Lub ntsiab lus ntawm tus PIN (Post-Intrinsic- Tsis zoo) yog tias ib txheej ntawm cov khoom siv semiconductor nrog cov doping concentration tsawg heev (xws li Si) yog ntxig rau ntawm P- hom thiab N- yam khoom semiconductor. Cov txheej no yog denoted li kuv (Intrinsic) thiab hu ua lub intrinsic cheeb tsam. Tus qauv ntawm aPIN photodiode(PIN-PD) muaj nyob rau hauv daim duab sab laug. Nyob rau hauv daim duab, tom qab qhov teeb meem tshwm sim los ntawm P * cheeb tsam, nws yog absorbed tsis tau tsuas yog nyob rau hauv lub depletion cheeb tsam, tab sis kuj nyob rau sab nraum lub depletion cheeb tsam. Cov absorptions no tsim cov diffusion tivthaiv hauv photocurrent. Piv txwv li, electrons nyob rau hauv cheeb tsam P * thawj zaug diffuse mus rau sab laug ciam teb ntawm lub depletion cheeb tsam thiab ces dhau los ntawm lub depletion cheeb tsam mus txog lub N * cheeb tsam. Ib yam li ntawd, qhov nyob hauv cheeb tsam N ' diffuse mus rau txoj cai ciam teb ntawm thaj av depletion ua ntej dhau los ntawm cheeb tsam depletion mus txog thaj tsam P *. Lub photocurrent nyob rau hauv cheeb tsam depletion yog hu ua drift tivthaiv, thiab nws lub sij hawm propagation mas nyob ntawm qhov dav ntawm lub depletion cheeb tsam. Obviously, lub sij hawm propagation ntawm lub diffusion tam sim no tivthaiv yog ntev tshaj li ntawm lub drift tam sim no tivthaiv. Raws li qhov tshwm sim, qhov kev ncua deb ntawm cov zis tam sim no mem tes ntawm photodetector yog lengthened, thiab lub sij hawm ncua sij hawm yuav cuam tshuam cov lus teb ceev ntawm photodetector.
Yog tias thaj av depletion yog nqaim, feem ntau cov photons yuav mus txog thaj tsam N + ua ntej absorbed los ntawm cheeb tsam depletion. Hauv cheeb tsam no, hluav taws xob hluav taws xob tsis muaj zog heev thiab tsis tuaj yeem cais cov hluav taws xob thiab qhov, ua rau muaj qhov ua tau zoo ntawm quantum.
Lub cheeb tsam nqaim depletion dav *w* ua rau muaj kev sib tshuam loj dua thiab lub sijhawm RC loj dua, uas ua rau muaj kev puas tsuaj rau siab - cov ntaub ntawv xa mus ceev.
Xav txog lub sijhawm drift thiab junction capacitance teebmeem, bandwidth ntawm photodiode tuaj yeem qhia tau tias:
Hauv cov qauv, R1yog lub load kuj.
Cov kev soj ntsuam saum toj no qhia tau hais tias kev nce qhov dav ntawm thaj av depletion yog qhov tseem ceeb.
Raws li pom hauv daim duab saum toj no, qhov dav ntawm I- cheeb tsam loj dua li thaj tsam P+ thiab N+. Yog li ntawd, ntau photons yog absorbed nyob rau hauv I- cheeb tsam, ua kom quantum efficiency thaum tuav ib tug me me diffusion tam sim no. Qhov rov qab tsis zoo voltage ntawm tus PIN photodiode tuaj yeem teeb tsa rau tus nqi me dua vim tias qhov tuab ntawm nws thaj tsam depletion yog qhov tseem ceeb txiav txim siab los ntawm qhov dav ntawm I- cheeb tsam.
Tau kawg, qhov dav dua kuv - cheeb tsam tsis zoo dua ib txwm. Qhov dav dav (w) ua rau lub sijhawm ntev dua rau cov neeg nqa khoom hauv cheeb tsam depletion, yog li txwv qhov bandwidth. Yog li ntawd, yuav tsum muaj kev txiav txim siab dav dav. Txij li cov khoom sib txawv ntawm cov khoom siv semiconductor muaj qhov sib txawv ntawm qhov sib txawv ntawm qhov sib txawv ntawm qhov sib txawv ntawm lub teeb, qhov dav ntawm thaj av sab hauv (I-} cheeb tsam) sib txawv. Piv txwv li, I- thaj tsam dav ntawm Si PIN photodiode yog kwv yees li 40 hli, thaum lub InGaAs PIN photodiode yog kwv yees li 4 hli. Qhov no txiav txim siab qhov sib txawv bandwidths thiab wavelength ranges ntawm photodetectors ua los ntawm ob yam khoom sib txawv: Si PIN photodiodes yog siv nyob rau hauv 850 nm band, thaum InGaAs PIN photodiodes siv nyob rau hauv 1310 nm thiab 1550 nm bands.
(APD) Avalanche photodiode
Ib qho APD (Avalanche Photodiode) yog ib qho photodetector rhiab heev uas siv cov nyhuv avalanche kom muab cov photocurrent. Lub hauv paus ntsiab lus ntawm cov nyhuv avalanche yog raws li hauv qab no: Ib qho teeb meem teeb meem teeb pom kev tsim hluav taws xob thawj zaug -qhov khub hauv APD. Vim yog qhov siab rov qab tsis zoo voltage thov rau APD, cov khoom siv hluav taws xob no - lub qhov khub nrawm nrawm raws li lub zog hluav taws xob, tau txais lub zog kinetic tseem ceeb. Thaum lawv sib tsoo nrog nruab nrab atoms, electrons nyob rau hauv lub valence band ntawm nruab nrab atoms nce lub zog thiab dhia mus rau lub conduction band, yog li tsim tshiab electron - qhov khub, hu ua lwm yam electron - qhov khub. Cov neeg nqa khoom thib ob no tuaj yeem sib tsoo nrog lwm cov atoms nruab nrab nyob rau hauv lub zog hluav taws xob, tsim hluav taws xob tshiab - lub qhov khub, yog li inducing cov txheej txheem avalanche uas tsim cov cab kuj tshiab. Hauv lwm lo lus, ib qho photon thaum kawg tsim ntau tus neeg nqa khoom, ua kom pom cov teeb liab hauv APD. Tus qauv tsim, qhov sib txawv ntawm APD thiab tus PIN photodiode nyob rau hauv qhov sib ntxiv ntawm P txheej ntxiv. Tus qauv ntawm APD yog qhia hauv daim duab 3-18. Thaum thim rov qab, muaj zog hluav taws xob muaj nyob rau hauv PN hlws ris sandwiched ntawm I txheej thiab N * txheej. Thaum qhov teeb meem teeb liab teeb nkag mus rau thaj tsam I los ntawm sab laug P * thaj tsam, nws tau nqus hauv I cheeb tsam los tsim cov khub electron-qhov. Cov hluav taws xob hauv cheeb tsam I nrawm nrawm mus rau thaj tsam PN kev sib tshuam, thiab cov hluav taws xob muaj zog hauv PN kev sib tshuam ua rau cov hluav taws xob ua rau muaj kev cuam tshuam avalanche.
Raws li kev tsim qauv, qhov sib txawv ntawm APD thiab PIN photodiode nyob rau hauv qhov sib ntxiv ntawm ib txheej ntxiv, P. Cov qauv ntawm APD yog qhia hauv daim duab zoo. Nyob rau hauv kev tsis ncaj ncees lawm, muaj zog hluav taws xob muaj nyob rau hauv PN hlws ris sandwiched ntawm I thiab N + txheej. Thaum qhov teeb meem teeb liab nkag mus rau hauv cheeb tsam I los ntawm sab laug P + cheeb tsam, nws yog absorbed nyob rau hauv I cheeb tsam, tsim hluav taws xob- qhov khub. Cov hluav taws xob nrawm nrawm mus rau thaj tsam PN kev sib tshuam, thiab cov hluav taws xob muaj zog hauv PN kev sib tshuam ua rau muaj kev cuam tshuam avalanche.
Piv rau PIN photodiodes, lub photocurrent yog amplified internally los ntawm APD, yog li tsis txhob muaj suab nrov qhia los ntawm sab nraud circuitry. Los ntawm qhov kev txheeb xyuas qhov nruab nrab, piv txwv li ib qho photon tsim M cov neeg nqa khoom, qhov no yog sib npaug rau qhov piv ntawm photocurrent kuv tso tawm tom qab APD avalanche mus rau thawj photocurrent kuv ua ntej sib npaug.
Hauv cov mis, M yog hu ua qhov sib npaug.
Qhov sib npaug yog cuam tshuam nrog tus nqi ionization ntawm tus nqi thauj khoom, uas yog hais txog qhov nruab nrab ntawm cov hluav taws xob - qhov khub uas tsim los ntawm ib chav nyob deb ntawm drift. Tus nqi hluav taws xob ionization thiab lub qhov ionization tus nqi sib txawv, txhais los ntawm ₀ thiab ₂, feem. Lawv muaj feem xyuam rau cov yam xws li thim rov qab tsis zoo voltage, depletion cheeb tsam dav, thiab doping concentration, thiab yog denoted li ₀.
Hauv cov mis, k yog tus ionization coefficient, uas yog ib qho kev ntsuas ntawm kev ua tau zoo ntawm photodetector.
Cov nyhuv ntawm ionization tus nqi ntawm M tuaj yeem muab los ntawm cov qauv hauv qab no:
Thaum=0, tsuas yog cov hluav taws xob koom nrog hauv cov txheej txheem avalanche, M=e^(-ω), thiab qhov nce nce ntxiv nrog ω. Thaum ω=1 thiab -1, raws li kev sib npaug (3-26), M → ∞, thiab avalanche tawg tshwm sim. Feem ntau, tus nqi ntawm M nyob ntawm 10 txog 500. Avalanche tawg nyob rau hauv APD tshwm sim vim hais tias cov ntaub ntawv rov qab tsis zoo voltage yog loj heev. Xav txog kev sib raug zoo ntawm M thiab qhov rov qab tsis zoo voltage, feem ntau siv cov qauv siv los piav txog lawv txoj kev sib raug zoo, piv txwv li:
Hauv cov mis, n yog qhov kub thiab txias -dependent characteristic index, n=2.5~7; Un yog avalanche tawg voltage, uas txawv ntawm 70 mus rau 200V rau cov khoom sib txawv semiconductor; U yog qhov rov qab tsis zoo voltage, uas feem ntau coj li 80% mus rau 90% ntawm UgR. Thaum siv APD, nws yog ib qho tseem ceeb los xyuas kom meej tias qhov kev khiav hauj lwm qhov hluav taws xob tau khaws cia hauv qab lub avalanche breakdown voltage kom tsis txhob ua rau lub cuab yeej puas.
