EE415/515 Fundamentals of Semiconductor Devices Fall 2012

Transcription

1 // 45/55 uamtals o Smicouctor Dvics all Lctur 4: iolar Juctio Trasistor hatr.4-.8 as-with moulatio arly ct V A ~-3V g o V g o V V V V A A r o // 45/55 J.. Morris

2 // as-with moulatio arrowig with rvrs ias u to ltio with or + : ltio with arox l V q a W L -l β icrass with V arly ct & arly voltag // 45/55 J.. Morris 3 xaml.8 or uiormly o Si P JT with =5x 6 /cc, =x 5 /cc, x =.7μm<<L, D =5cm /s, & V =.6V. alculat th chag i J or V =V to V a trmi V A. irst calculat as withs or V =V a V // 45/55 J.. Morris 4

3 // xaml.8 or uiormly o Si P JT with =5x 6 /cc, =x 5 /cc, x =.7μm<<L, D =5cm /s, & V =.6V. alculat th chag i J or V =V to V a trmi V A. otiu or x a or V or ow us x to trmi th as iusio currts V J g V o L D x V V J V 9.7V x x J or x 54.5 x x 54.5 x J 4.597x V oth whr.648x cass x x x i.5 x 6 5x A // 45/55 J.. Morris 5 3 / cc 4.5x / cc 3.95A / cm A / cm.59 J or V.6 V.6 V A A A urrt ijctio as couctivity moulatio α, β vary with ijctio, lvls Low lvl ijctio: comiatio i ltio rgios sigiicat, scially i juctio rcomiatio rucs mittr ijctio icicy γ, hc α, β haractristic curvs closr tha or mi-lvl High lvl ijctio: High lvl o ijct xcss miority carrirs lctros or P i as rom harg utrality Also icras lvl o xcss hols, ossily > cras hol sity icras cras γ -V charactristic curvs closr tha or mi-lvl // 45/55 J.. Morris 6 3

4 // High ijctio: jct miority carrirs i as majority. High miority lctro ijctio ito P icrass majority hol sity at juctio, a icrass J. Low ijctio :, crasig, a a so High ijctio : still, ut so, J icras mor slowly with V // 45/55 J.. Morris 7 High/low-lvl ijctio cts // 45/55 J.. Morris 8 4

5 // Thrmal cts Joul hatig y V Domiat ct: arrir litims τ, τ icras icras β Thrmal ruaway Also: Moilitis μ, μ cras as T -3/ D, D cras cras as trasit tim τ t cras β // 45/55 J.. Morris 9 mittr a-ga arrowig or - ty As icrass, oors closr togthr tractio slits/roas which rachs. G i c v G G c v G i / i i G crass lss with may icras. mittr... mittr ijctio os' t icras as ast with icrass, may cras. // 45/55 J.. Morris G D cras. icrass, lvl, 5

6 // x.9 Dtrmi th thrmal quilirium miority carrir coctratio or a mittr oig coctratio = /cc, takig a-ga arrowig ito accout. // 45/55 J.. Morris, aras ir irt α a α as rsistac: hysical PP structur r rsistac to cotacts r / as sraig rsistac thi as V icras ar cotacts V A = V - AD + D & V D = V - D orwar ias gratst at g V D // 45/55 J.. Morris 6

7 // mittr currt crowig orwar ias gratst at g Hc hol ijctio gratst at g Possil high ijctio cts hr Miimiz crowig miimiz r cts Powr JTs a log thi cotact or itr-igitat structur // 45/55 J.. Morris 3 o-uiorm as oig: Las to lctric il i as assum zro J a D x i quilirium, a so.. x a a hr, so x, x acclrats lctros to collctor, i..rit currt iusio currt a // 45/55 J.. Morris 4 7

8 // Diusio oig las to oor coctratio grait x i th as rviously assum to costat Hc > W laig to lctric il rit assistig as trasort o hols ucs as trasit tim τ t // 45/55 J.. Morris 5 as il or alac lctro rit a iusio at quilirium, a assumig x x x x qa x x qad givs x D x x x x x q x x q whr W aw x x q x x a W q ax or a otial istriutio x ax W W a W W so a l[ W ] ax W // 45/55 J.. Morris 6 8

9 // rakow voltag: Puch-through Puch - through wh x i.. wh V t x x., i.. wh s x // 45/55 J.. Morris 7 x or V t s Vi V V i t.. rakow voltag: Avalach O O is rvrs - ias saturatio? - currt or o as, - orwar ias, O O At - rakow i.. wh // 45/55 J.. Morris 8 O O M O O or M M VO or V V at rakow, i.. VO VO V V O O or o as at akow, O O O M O currt O O whr M V M V O whr 3 6 9

10 // Thr cts:. Puchthrough wh W =, i.. V =q L /ε, ut usually avalach irst. Avalach: whr M O M V VO 3. urrt multilicatio ommo-mittr a ommoas or =: = M O a at V =V O wh M sigl rv ias io or =, = = M O /-Mα a wh Mα =, i.. icras as M, so V O <<V O 3. Multilicatio: - HP gratio hol to, - to icr icr icr // 45/55 J.. Morris 9 x. Mtallurgical W o a Si P JT is x =.8μm, with =5x 6 /cc & =x 5 /cc. Dtrmi a uchthrough voltag & avalach voltag. // 45/55 J.. Morris

11 // x. Uiormly o Si JT with =5x 6 /cc & =x 5 /cc has β=5. Dtrmi a V O a V O, or =3. // 45/55 J.. Morris Kirk ct ormal - ltio rgio Also, icluig ijct hols, writ: q a x Av v rit vlocity, a V Wc W x V ix, so as icr, as si ltio rgio At high, ijct hols chag ctiv imurity sitis:, >, & a, < a, so W c/ > W c & W / > W as trasit tim τ t icr, so β cr // 45/55 J.. Morris

12 // rs-moll quivalt circuit // 45/55 J.. Morris 3 our oratig mos vali or all Moll rs - ot it,,, a ot : a i th rvrs - activ mo, Similarly : i.. currt saturatio th rvrs is, a currt saturatio th rvrs is, whr i th orwar - activ mo show irctios currt or S S S S S S rs-moll: Saturatio voltag // 45/55 J.. Morris 4 l l V givs Sustitut ito i... oth V, whr V V S S S V V sat

13 // rs-moll: Saturatio voltag cot Similarly S Sustitut ito S S S S givs V l S l S S so V sat V V l. S l. // 45/55 J.. Morris 5 x. alculat V sat or a JT at 3K, with α =.99, α =.5, =.5mA, =5μA. // 45/55 J.. Morris 6 3

14 // Gumml-Poo quivalt circuit mor hysical - iclu o-uiorm as oig x P as J x D x x whr.. x x x x so J x.. D x x x D x x D. x x x x x x x J x x x x x x D or w ias, rv ias : /, x, i / Di / Di / so J x x x whr as Gumml umr, total majority charg i as D i / D i / Similarly or th mittr, J x / / x x whr as Gumml umr, total majority chargi mittr ot: Gumml-Poo ca iclu o-ial cts lik Wmoulatio, high-lvl ijctio y icluig cts o chargs Gumml umrs // 45/55 J.. Morris 7 Sco-orr cts i Gumml-Poo arly ct : Writ W V V x x with ias t limits High lvlijctio, wh a so qv qv qv qv / / qv / W x x W x x i th as : D or high - lvlijctio i th as; s ama 8.. / sic o high - lvlijctio cts i mittr / - ltio rgio gratio/rcomiatio at low ut qv qv qv / s ama 8..o - iality actor larg a uact, so qv / qv / / // 45/55 J.. Morris 8 /, a : 4

15 // Hyri-i quivalt circuit /, /, / ial itral rgios // 45/55 J.. Morris 9 Hyri-i comots small sigal r : sris as rsistac π : w ias iusio caacitac r π : small sigal juctio rsistac j : juctio sac charg caacitac r x : sris mittr rsistac ~-Ω r c : sris collctor rsistac s : rv ias collctorsustrat juctio r O : arly ct g m V // : collctor currt r μ : rv ias small sigal rsistac ~MΩ, glct μ : rv ias juctio caacitac // 45/55 J.. Morris 3 5

16 // x.3 i th valu o π such that A i =h / ½ at 35MHz. h Ai r // 45/55 J.. Morris 3 rqucy limits as trasit tim sigal rio - rsos tim c c / / τ juctio chargig tim r j, r r / / τ collctor ltio rgio trasit tim x c / vs sac charg with/saturatio vlocity τ c collctor caacitac chargig tim rc s τ as trasit tim : x x x x x x x J x v x x a t t v x J x x D or x a J D x x x x x x x x x x x x x x J x D x D D // 45/55 J.. Morris 3 6

17 // 7 JT cut-o rqucy // 45/55 J.. Morris 33 rqucy ta cuto /. a whr rqucy Alha cuto j j j j j j at α α j T T T T T T T c x.4 or JT with =5μA, j =.4, μ =.5, x =.5μm, x c =.4μm, D =5cm /s, r c =Ω, s =., trmi th -to- trasit tim, th cuto rqucy, a th ta cuto rqucy. // 45/55 J.. Morris 34

18 // Larg-sigal switchig // 45/55 J.. Morris 35 Schottky-clam JT Al Si // 45/55 J.. Morris 36 8

19 // Poly-Si mittr JT uc miority hol coctratio grait i th mittr rucs th io hol currt // 45/55 J.. Morris 37 Si-G as JT icras at th - juctio, so icrass // 45/55 J.. Morris 38 9

20 // Htrojuctio JT // 45/55 J.. Morris 39 Htrojuctio JT.g. P wi a-ga mittr: qv hols >> qv - s crass γ as hol currt surss a whr is a ga irc so otial ct g g // 45/55 J.. Morris 4

21 // Assigmt #7 & 55 Projcts.4.4& Grauat rojcts:. MOST alicatios as activ ssors. aomos: Ts, strai lattics, tc 3. Orgaic trasistors: hysics, rortis, aricatio 4. Orgaic LDs: hysics, rortis, aricatio // 45/55 J.. Morris 4 harg otrol Prolm with usig rs-moll a most othr quatios otai so ar: urrts roortioal to otial uctios ut comar thos rlatig currts to charg usually arox urrt-charg rlatioshi liar, so calculatios asir a y comutr astr As aov, sarat th as charg hol or istriutio ito mittr ormal- a collctor ivrt- comots Th: = /τ t whr τ t is ormal mo as trasit tim, i. tim to collct charg = /τ t + /τ icluig th rcomiatio currt, a = - /τ t a = - /τ t - /τ // 45/55 J.. Morris 4

22 // harg cotrol cotiu So total currts ar with a t t t t a as currts ar so t, t // 45/55 J.. Morris 43 harg otrol: Tim c t t t t t t - t t s latr or alicatio i ac cts // 45/55 J.. Morris 44

23 // 3 harg otrol: rs-moll quivalc // 45/55 J.. Morris 45 so & ; / & / Writig qv S qv t qv t S t qv t qv S qv S t t t qv S qv t t t S t t q q q q q q q q q q // 46 45/55 J.. Morris Saturatio: orwar ias, orwar ias ias at ost Ost w ias w ias Ovrsaturatio: tim to rmov xcss charg urig switchig

24 // Switchig cycl: itially cuto t icrass util liar activ t limit; saturatio ost t s icrass i ovrsaturatio towars + S /τ Turo: rmovs S, th Storag lay: costat util S rmov // 45/55 J.. Morris 47-9% switchig tims // 45/55 J.. Morris 48 4