EE 232 Lightwave Devices. Photodiodes

Transcription

1 EE 3 Lgwav Dvcs Lcur 8: oocoucors a p-- ooos Rag: Cuag, Cap. 4 Isrucor: Mg C. Wu Uvrsy of Calfora, Brkly Elcrcal Egrg a Compur Sccs Dp. EE3 Lcur 8-8. Uvrsy of Calfora oocoucors ω + - x Ara w L Euval Crcu ω Dark curr: ( p) J σ E μ + p μ E Lg llumao gra lcro-ol pars, crasg coucvy: δ δ G Say sa: / --> δ G ( p) Δ J δ μ + μ E oocoucor rurs bo coacs cs o b Omc EE3 Lcur 8-8. Uvrsy of Calfora

2 oocarrr Grao Ra ω Lg Isy α x + - x Ara w L op ( R ) x ( α ) op op G η : poocarrr grao ra [ ] 3 ω lw cm s η η ( R)( α ) R : rflcvy of poocoucor surfac α: absorpo coffc : absorpo lg α : fraco of lg rmas afr absorpo lg EE3 Lcur Uvrsy of Calfora oocoucv Ga ( )( μ μp) Δ I lwδ J lw G + E op Δ I lw η ( μ + μp) E ω lw op Δ I η ( μ E ) η v ω ω : ras m v I Δ η op ω op oocurr oocoucv Ga EE3 Lcur Uvrsy of Calfora

3 Aalogy o Curr Ga Bpolar Trassor Curr ga bpolar rassor: E B C I C β I B T curr ga ca also b xprss as rb β :rasm m rb : carrr rcombao lfm bas EE3 Lcur Uvrsy of Calfora N op N η ω lw Small sgal rspos: N N + N jω N jωn η ω lw N η ω ( lw ) jω+ / ( ) I J lw N v lw Frucy of oocoucors Rspos (B) ooc coucv /, /, / / / I η ω jω + ( DC Quaum Effccy ) ( oocoucv Ga ) ( Normalz Frucy Rspos) EE3 Lcur Uvrsy of Calfora Frucy (Hz)

4 Rvrs-bas p-- juco Mos of volag rop across -rgo, ma absorpo rgo Hg fl sparas poogra lcro a ol -- ooo ν N Larg bagap marals ar us for a N f possbl Ec Ev Fas rspos ν Low os No ga (uaum ffccy 4 < %) F x EE3 Lcur Uvrsy of Calfora I-V Curv kt B Dark curr: I I ( ) V I oocurr: I η p op ω Quaum ffccy: η η ( R)( α ) V kt B Toal curr: I I ( ) + I p V I p I p Loa L for Basg D EE3 Lcur Uvrsy of Calfora

5 Absorpo Coffc Lg sy cays xpoally smcoucor: I( x) I αx Drc bagap smcoucor as a sarp absorpo g S absorbs poos w v > E g. V, bu absorpo coffc s small Suffc for CCD A gr rgy (~ 3 V), absorpo coffc of S bcoms larg aga, u o rc bagap raso o gr CB EE3 Lcur Uvrsy of Calfora Two Typs of p-- ooos L Surfac-Illuma p-- η η ( R)( α ) η : ral uaum ffccy R : rflcvy : absorpo layr ckss Wavgu p-- Γ L η η ( R)( α ) η : ral uaum ffccy R : rflcvy Γ : cofm facor L : lg of wavgu D EE3 Lcur 8-8. Uvrsy of Calfora

6 Ramo s Torm A T curr caus xral crcu by a movg carg movg a a volocy v ( ) a paralll pla w a sparao of a a volag bas of V s v() () roof: Work o o carg: W Forc Dsplacm V Ex x Work prov by powr supply: W () V V V () x x v () () EE3 Lcur 8-8. Uvrsy of Calfora Rspos of O oogra Elcro-Hol ar v () () + () / () N v / () Tm EE3 Lcur 8- x x x Tm v v Hol Trajcory Elcro Trajcory 8. Uvrsy of Calfora Toal carg gra: Q () + () v x v x + v v O absorb poo o carg c

7 Tras Tm () () + () N () () May lcro-ol pars gra v v Tm Elcro curr s w las lcro gra ar -s racs N-lcro: v Hol curr s w las ol gra ar N-s racs -lcro: v Hol s usually slowr A cosrvav sma of ras m: v EE3 Lcur Uvrsy of Calfora Toal Rspos Tm of p-- () m: ε A R ( A : ara of p--) () Tras m: v Toal rspos m: f 3B + π Absorpo layr ckss for opmum frucy rspos: Rε A + + v Rε A v v f 3B f3 B,max π 4π Rε A Opmum baw occurs w Rε A v opmum Rε Av EE3 Lcur Uvrsy of Calfora

8 Mor Rgorous Aalyss of p-- Rspos Tm Small-sgal aalyss: assum pu lg s moula a frucy ω, poocurr s proporoal o ( ( ) ) log H f ω Tras s Tm () + log H( f jω ω ) T frs rm s sgl-pol rspos from, wl sco rm s pas lay u o Toal ras m rspos. ( ) ( ( ) ) log H3 f f f EE3 Lcur Uvrsy of Calfora f Comparso of Numrc Exampls Exampl: 4.4 ps ps f 3B 4.6 GHz π + ω s () H( ω) + j ω ω Solvg H( ω ), f3b 9.7 GHz T scrpacy s smallr w omas, a largr w ras m omas. (Tras m rspos as a sarp rop-off). EE3 Lcur Uvrsy of Calfora ( ( ) ) log H f Tras Tm log H f ( ( ) ) Toal ( ( ) ) log H3 f f f f

9 Baw-Effccy rouc () For surfac-lluma p-- (assum AR coag: R%), xrm of absorbg layr a ras-m-oma rspos: α η η ( ) η ( ( α )) ηα v f3b π v ηα v Baw-ffccy pr ouc: f3b η ( ηα ) π π () O or a, ffccy of wavgu p-- s ΓαL η η ( ) ηγαl -lm baw: f3b π RεLw ηγα Baw-ffccy prouc: f3b η ( ηγ αl) π R ε L w π R ε w I gral, r s a baw-ffccy ra-off EE3 Lcur Uvrsy of Calfora