Voicu, Dolocan - Fizica jonctiunilor cu semiconductoare

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EDITUNA ACADEMIEI REPUBLICU SOCIALISTE ROMANIA
R 79717, Bucureqti, Calea Victoriei, nr. 125

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(lapitolul 5, S'fl|UOTt'l.iI l1;iT:\i. IZOT,ITOIi-SE\II{iOflI)U(:'f{}1,\ 1{5

5.1. Slructura,\IIS (s:tu ]IOS) idcal:i llir
it.2. Flfectul difclenfci dintrc luclurilc rie icsirc asuill.a
151
caracteristicilor structurii,\{OS. Diagrarna dr bcnzi rlc
l('ueri.a-ie shucturii rrtr:tlrl- SiOr-Si 111 {
5.3. Ijfcctele capcanclor ;i sarcinilol fixc dc ill inl-r:rlata siliciu-
168
bioxi<l dc silicirr .
174
J.4. Iifectcle ionilol rnobili, nouni.[on.rritifilor letcralo si cnp, t7 4,
178
canclot ionizate asupra caractcristicilorstrrrclurii tr{OS 18!

5.5. Stratul dc invctsiunc. L,lltctelc lcmpcratuiii si lurninii 186
asupra stle tului dt: invelsirrnc. Conrlrrctanl.a canalului
18li
i.fi- I'lfrcLclt' r:rriiatiilor
5.1. (laractet'jsticilc curcnt-tensiunc alc tlurrzistorului \,IOS. 192
5.ti. liegiunea dr: sirLur':rtio 193
;.(). (lircrritul cchivnlent al tlazistoruhri l{OS. Arnplific:rrtra. 198
200
Ii'rtncl-ionarca lir inaltir [rccvcnfir
5.10.'Iipuri de tranzistoare \1OS. {lont:ctalcu trauzisloa

rtlot'ilr circrriI
5.11. Influen[a tempcrrlt'-trii ir,supra caractcristicilor trirn,

zistornlui \'I0S.

5.12. AItc tipuri dc tranzisto:lt't crr cfcct rlc cirnp (lo su-

prafatri
5.13. Structuli rnctal-izolator-nrctltI

5.1.tr. i:fcctul tuncl in s[ructuri rnctal,oxid-semiconductol'
5.15.'l'ranzistoarele cu elcctroni licrbinti

.l) iirl iogra f i e

(l:rpilolnl G, l) ISPOZI'l'I\r I, I)Ll -\{L)l0rtIFt sI t)tt t}IAGIii!'t. }iHi:i{) 2 0:l
201
G.t,.,\F Ir\ 209
214
6.1. I)ispozitir:c de ntcnolit' <'rr ooartir plrrtitoarc 215
6.2. l)ispozitivc de rne rnoric cLr c:lptarr do sarci,'tii 216
{i.:J. llcrnorir cr.l Lroarti fclocll'cti ic:i 220
i-lelcle de rnertorirl
ti..l. 22t-
6.;'r. \Ietotlc clt' r'eproclucelc a irnugirlilor 2:io
6.0. \crografil
6,7. l)cscricrca proccsclor Iizice carc itu loc in inttcrialul 241
cllctlofol rgr:r Iic.
ti.tt. 219
Oondilii dr: opliirriz:rrr a ;-ll'ocesulLri dc xcrogi'alir.rrt. ilIat.c 25:i
25{i
t irlr' tttiiiz;tlt'
6-0. Scnscri dc irnaginc
(i.10. l)ispozitir c c..rplrrtc Djrin sru'cilld

6.11. Zg-omotul in tlispozitivelc cu r:upla.j prin saicinii

ii.12. \Ietocic tic baleiaj i;r sensolii dc irrngiuc

0.111. {larncicl'isticilc sellsolilo: cte ir;rngin,: cli dispc}zitivc
platI prilr sJrciitr

6.'14. Sclsori cu dispoziIitr] cu injccfic (1.' sa!'cii]ir

6.15. Scnsori cltl iilagine i:r infraroSu

Ilihliogralic

{iapitolttl 7. OIRCt,'l'lE Iii l'EGR:\TE 258

'l',:hnic i ntilizatc in f abricarea cilclrit(rlor i::rtr: grate 2i-r8

lzolarca, intcrconr.ctaroa, prsivarea 26ll
2lt7
(lircuite intcgrate ncrrolitice din siliciu 270
dircuitc iategrate cu strate subliri .)?t
Circuite intograte cu stratc groase.
{lircuitc hibridc 272
:\plica!ii ,a^

Bibliografic 280

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caz s€r gencreazS, lipbeelerichrliecul(r'crtrsoinn-gguort)se; l(nbn)).extrinsccl, (in care ca,z sLi qcne-
reazd,
purtd,tori

2. Efecttr fotovoltaice l4l (apare o tensiune fotoeleetricX cla,torat,X

urrui cimp electric intern sau alt5, camzil care scparii perechilc rhctlon-
gol generato do cii,trt fotoni). Apare in urmS,toarele situai,ii : (a) joncliuncr

p-rr, diotll err uvalan;i, diodrr, p-i-n, dioda ScboLlk3-, ht tcl.oji_rrrcl,iunr.,

fototranzistoi'; (b) efecte fr-itovoltaice de volum (datorate unui grarlient
al conccntraliei dr-: irnpurit[,ti, unui gradient aI masei efcctive, uirui gra-

dicnt al bcnzii intcrzise); (c) cfectul fotoeltctromagnetic; (d) cfcitntr
lJembct'.
B. Ilfccrt'e in care fotonii intelacl,ioneaz5 cu purtirtolii libel'i: r,fec-
tul dc an1,rq:nare fotonic5,, detr:ctorul Pntley, ltolometrul cn
fir:rbinti 13l. elcctloni

C. Efect,'o cle interactii locaiiza,te (electlonii sint t xcita.i tle citre r,adi-
alia po st5,ri locaiiza,'r,cr de energie). Pe accast5, bazi, functioncazS, lurnino-

forii,-filmcle fotografice ;i nurni,r:d,tolul cuantic in infrart;u.
afrrfinnciltiaoBntfeceaccztcldel,ecftorfoototnocincaiitic,ocnzceiigxacteatirlrne.ic,p(socitnatfpicitfdocelcutlteL4od)uc.irFfofoetotloucrmrnii:usiicetio.pnllivlccra:ntatocioreiniaasflutiin;cbifaioezl-ti

neazra pe baza mecanismuiui de rnultipiicale a electronilor ernigi de cil,tre
fotocatozi.

Efectele torrnic,t-r st datorcazri incS,lzirii rnaterialului srb ac-tiunca

r(a1d) ibaolieioim. EextlicstS: ,temrmaiisml,uolrtuel,tibpoulroimdeetcrlueltercnteotrai lbica,zsaulippt,aecro_n,fretcruteclteorte, rsrnuipcrea-:

inductor, cu semiconductor r'5,cit; (2) tietector piroelectric; (B) detcbtor
tr.:rmot'lectric; (4) detector pirornagnetic; (5) detector Nernst; (6) celulr,
Golay (tt:tectol pneurnatic); (7) rnicrofonu-l condensator. eu gLZ; (8) evzr-
polagraf ; (9) detector cu ei'istale lichicle ; (10) detector.bazat pe dcpendcn!,a
dcr tcmpelatnr5, a marginii de absorbtio a unui scrnicontluctor.

Principalii detectori ltaza\i pe efectul interacliei de und5 sint detee-

torul heterodirrd, ;i arnplificatorul parametric.
in dett'ctorul heterorlin5,, folosind un oscilator local cle rrft:rinli,

se convortcqte unda incidarrt5 intr-o und5, de frecven!5 joasd,, in domeniul
undelor radio sau rnicroundelor. Dctectorii parame,trisi sint constituitl'
din cristale in care a,r'c loc mix:lr'ca a douX fascicole de raclialie coelcntf,
ryi rezultX, dc tr>;gmphr, ratliatie eu frecventa sumX sau difer.en!5.

Evidcnt cX aceasti, clasificaxr a dctectorilor de radiatie nu este strict*.
tTnele efecte fotonice potficonsickrratr: efectrr termice sau efeate de interae-
l,ie de uncld,. Structurile metal-oxitl mertal qi clispozitivele Josephson [4]
pot de ascrntnca considcl'atc ca dctectori ba,za!,i prl fcnornenul dc interac-
li
!,ie de undd,.
Detectorii mai pot' fi clasifical;i ctr detectori elerntntari qi dctectori
(sensori) de imagine in functir di. faltlul dacd, semnalul t1,.r ieqire reprczintd
o valoarc medie peste intleaga a,i'ic r;ensibilS, sau redd, o dcpend+:nfd, spa-
fiald, pe suprafa!5,. Detectorii cle irnagine sr.: ltazo-azil pe aceleaqi mecanis-
me de deteclie (in general fotoconcluctia sau r fectul fot,ovoltaic) in plus
in detectorii cle irnagine variatia spaliaid, se citcryte cu u.n sistem c1c traleaj :
un fascicol de electroni ea in tubul vidicon sau clectric ca in circuitele
cuplate prin sarcinX. Sensorii de imaginr: ct sircuit;e cuplate prin sarcini
sint prezentali in capitolul 6. Dupi, circuitul electric utilizat detectorii
se impart in activi qi pasivi.Detectorii activi produc o tensiune sauun curent

14

:*BptF-;R.'

9T

(r'r) (Eo)r,r : (rrurl)oy lu

16'T TIJO

cilceld {Lri}srs rm-,r}uI',ro1ri1pi1r.rndilurJrlcst3oJs.rsunars+cim"€rujprpsrla,rlr.:ruil1,i;llrcJlys(r-{rp?1Ernrn;peupn ?uI
3I
-. -'c9t-l o.,
L :!

er{e1e.r rrlp ?qm SNI
-rd+sp as Se"ril ep gpun trp tarirr8unl '(rcasul.r1x., rJo+cnpuocolol) ?urcJtsB €]p
dl+ .rnFuis rnrrn EaJr?+raxi ed yzvrzvq es el{oo1ep op Innour -s
r.rolpgrnd ap uJ '+tsmu"rrlr rnlnJo+cnpuoorlriij-q B osrz.{,J+rrr rrzuoq eourr8
-ouoJ pr4o -ed
IISnzp'Blac -ui i1u1urn1 tszr+r-i' c '4cue1d rnl E+uts+suoc ,a+sJ E opun ?1r
-JKI -'A
Ir
0fl.
- ']l
:-"Y
tr
cq
-tl
op ,uourr8unl (crul1oao+oJ +oaJ.) (castaurultzlulatr urp KururJ.?sp os 5cld op ppun 's
Jo+c1lpuocolo;) rlolcnpuocrruas
9
1pua5eupi1lcauour8Ilnr-rruzaFotsdu.crsnlcluaiiJKllas+'osug,rBqnpocducaesn?Jpaolgld+pse'Ftoapqdurers'oroiSror.'eranp'"Jsnrzatocru€r+ru{lsI}3lpaFcua+rsrnduenteuJrvprqzouanaaoqudzperecrpcpquusuoal ?isacd+oapsrpr-udrpoicctuprauu'l5or[lnepeai?proodIJnpectoarIannpr+Juuooora+3pymcuoKpno+ppluaruna{pnncl
'Epun ap earul8uni ep rritunJ uI !i
luJjJJds lnsundslg 'u d L '"':rl .reruq atriarc 1e;rlcads lnsunclsp;r ruo+o; ap InJot It!
-calop n;rluacl Fc F,!.rasqo aS 'qt?apr rcrruJo+
*Y _i
Ii iuolo; op rrro+ca+op uluaci ?p{rn op arurFunl
1]
'-eespag+oJts+++€rtu+?nr+uuenJ1zIa1€,rrc:J1lae,.rr+ooudqru"sa.ra'dLnrpl lgZu'aTprlurrc..rrunlcr8arodt;is'u.l,lJln.r1s'aduanoi+dp
-
-t1a.i rfpgirrn ui gtrrr,rdxo irrd 1e.r1cads insund
'tl
-sKJ rJnzcc o?Intrr reur oiJJ u1 '1c1,1t{o JoIrJo1
fi

---ccrJoa€?+aoepP,BIInrntozzpvBc'tc?rorrlrprrarrc3aroqrcroq;zaoprro,n.lp*iors.:rroqlz*l.oors;]uoar1s0uJpIalu"sruo?rlrJ+J€uoaE+

t?rrrrJd ',r:pun ap aturFrrnl op Ba+e+run ad r{uap
,i? olt??run uq.eJ EI nus 'Kpun op ourrrSunl ilp a+m,trrun l?aJogrrr
o-rdcu(rprluolaruporc+uolJ
Ko+puerrrpnt3dJrel ;roaIqa.snJcOloAprp€Jo?J€+?u_rur n?u+luluarplcnalcdusolncsuonrd{esplu:rduerozecaolrord}ce€.Jr:
os IJo+oa+op
€ n.r?uad 'o+€1ca?op rar{erpe,r € Epun ap earur8unl ap ar{cunI uI Jo}caqoB
tsI oB arriar .rp rnlnl€uiuas u{uopuadap ar,rcsap lu.rlcacls 1n"^unc{spg

7n4ced,s lrtsrntdsp2l ' L'Z' L

oo.rlslraloErBo rIIIlrPI{'z'I

' ilJ'r3uor{cun; n.rluad

nnur+uoc +LroJnc ap Errr.ra+xa FSJns o ap oroaau ne ri .rla.rqeuroloq ri rr.rolsrz

qr--arcJ.arool+qac.oooJl+rdo1pur1r:Jso+l+urrcriJsa+uraedrp?rc'(r€;J.ro1rr+,Jrc.oon?lccooqo+loa'eqcc+'rnr{+4ruscrsrrl1uaunoocuc)r.rla{a;rxlae;oergn1caca1+ordDppr?SeselJcnlpasoldronpcu(orcrrrluuia.'3rce1uol a'otaq1.o.rrg1*

vzvazrlr+Lr -rs rJoarrrl r*rp o,reluourqe ap KSJns o ?J'llsooJu arJ Frr EJTJ lrnl,rrc ur

in tabela 1.1 se dau lungimiio de und5, de prag pentru unii rlrtectori
fotoconcluctivi (FC) qi fotovoltaici (FV) calo funetioneazd, in domeniutr

infraro;u.

T'abela 1.1

Caracteristici alc detectorilor de infrarogu

Ilirterialut ji l-nl'ntoclarounaor"e emperatura, Iio, pm D** f'S
I cmllzr/z Srr/z/1.1,*
K

Ge: B FC A' 108 I n, o. ro,o 10-8
Ge: Ga FC 4,2 104 6, 8. 10ro
Ge: Cu 4.3 2. 1010 4.10-r
Ge: Cu trc ZJ 3.10-e
(sb) 4,2 2. 1010
Ge: Hg FC 27 10,5 4.1010 2.10's
Ge: Hg FC
(sb) 4,2 11 1 , 8. 1010 3. 10-10
PbSnTe FC 10 3. 108
FC, FV 77 1,5.10 s
FIgCdTe FC ?7 9,6 3, 1 . 1010
FC ?7 3'10s 8. 10-7
Ge: Au 6 3. 10-s
Ge: Au FC 77 6. 10s
(sb) FV 77 tl 8,7.1010 1 ,6 . 10-e
PbTe FV
FC 77 -o 1011 2,5'10*3
InSb FV 77 6.1010 2 .10-8
4,9
PbS 3,8 7.70t4 3,2 . 10-5
InAs 2,8 5. 10-?

1.2.2. Pu,terea echi,ucelentd, d,e zgomot

Puterea echivalentS, cle zgomot P"notatd, in literatura striind, NEF
iNoise Equivalent Power) sau Pi' este puterea incidentd, pe detector nece-
sar5, pentru a obline la ie,Sire un semnal (tensiune sau curent) egal cu sem-
nalul de zgomot. P"variazd, direct proporlionalcur5,cl5,cina p5,trat5, din
tzsreeicrvetWcxnpl.rEtdimz, t5qtz,i .dpeeCcniintrtduresbJe:uadinedsaPpd"eectirffeircbeacutSviee, nqs!ip5te,rcadinfeicdaalltSfdz,ea,sfrr'iieacsvdr,eemnte-5tcd,st,o.orauDrd.e-,
banda de

obicei P,
in acest c
trui qi cimpul vizual. Pentru detectorii din domeniul infraroqu pin5, in clo-
mi'niu} trndelol milimetrice, ea €'ste propo{ionald, cu ridS,cina ph,tratf,, din
aria dctect'orului.

7.2.3. Responsio'itateu

Responsivitatea este raportul dintre tensiunca sau curentul de ieqire
pp;ioopnnusstiievvriitetaaatteeraaaddicaeonttreXpc,utoiinurcuiildnueeingitadru,.raeSd(eTiam,li5fa,)sodnaseirXsinpiet"rcatVrlaeflW5e,mesiQas5n,,, A/W. Se disting res-

f). e(f , f) esto res-

de un corp negru Ia
?A,nradlo,sgpru&ls(u1l,.ffi)in, desrtneSd,seufirnaittdp,ecafrcrcevsepnolnasi/vilcautecaalI.ea
tcrnperatura absolutd,
rlste modulatd, aceasta.
o radial;ie m.onocromaticd, de lungime de ulcld, ). modulatd, ct frecven{a
J'. Daci,'de exemplu os este tensiuiea semna,lului md,surat P
radiantfi, incident5,, qi este puterd,a
e,tunci responsivitatea de tensiune

o os 'Ds

P .4.[

r.inde i. esic aria dertectorului qi f este iluminarea.

rG

LT ot 'esl c -z

Irrx€n?ulnruiJ)J.oert??strsurrcJrIinJl?r1uldoluulerluo5o1znru1,oo;,,uFr1rzopfor'zronpolntqol€y+ortslr+autpwisrrliElT.pr"rurlusoJy.ntsooElprrrtorIn?o+aJoolt1rrrarroplFdzoI1noo?,rr-+;ilua!€cJurorcrporJr6JJus?.drsozgrslro+cne

ploruo$T .g.1

g--.rAi,oi"JlrooLod).:I?t)(dpl)lra"i[in,o-p".ireooai.nn'ua,.:rlqD1o3utlr.ti,;tsc:rrllrlf'are'Je..o[ru.J)p,Jd)u€^plcJaaJprllJsndazngBpl,niceslnouusdnlgdtuu'sorr-re.al;lsrvor.g(]s,oal,rrtlql:r€nIm5ou€pruerurilnu;c+alrddlJ,prrJ.Jupr}nF*ns.cr;lssn1oduo1apoo.;1p€o'JrsKourtluitil

-€ip".r E o,rtlnporlr orpiutnjuan-rnlue;at"{r;,?rzn€la?€rru,nru1oslur1nds'(gs,urnidlpspInr darpudru; 4'T1'Tr*€oIrliqo€ru1nuul
?]'up o?sa rrolco?op
{€ur osr) o.raz eiu.re'ca.g nrlued plnur{qo uJunrsual o1s.'r 0o rS rarfrrpe.r € cJsl
-npour op f t:{ualcJ,rJ ,rrl rnln,ro}crlap e sundse.r op €runrsua? olsa (.f)c apun

,;t!:!ol[a: \(.'f)/c"

triel'r'r
irr.rd r.rolcalrp r.ilnur r€ru raa n"rluacl Tllu-r;rp olsJ r dunl ap €lrreJsrro3

'sundsp"t ap dru.tx ap n?xrnqsuoC 'g'7,'T

6Ieuor1qo.ezlIaof.["rrarrlulrq.gc]oputq[rQ"€orJ1dSu.cqr*oq*1nooccsl'1ulap€1pnnlu1zq,rra^sgorlp{nJguor1nqlc;15ra1uu+ggn.d)p'oxrlrrs({tfaernr:6p€nI *.S.rr*luuporaqsdlCcsu*(,'n/re,,r:(}{I€eIrxrptl?*rIe(ieo.[rJir(uJarqo,pfepla€1laa)g.rr'airaulJi,ros/.aarrldurrJ.arS6sdr

tla,J€Ulr+cclap op g1eFa1 d+sa oJtsc **O r3arrn.rfur ocnpoJlur os ("ro1p.rnfuocug
Ftrpaur) piroJ 3p liullu4l +uIS oJt3J ,rollJolcalap €a.rBzl.r3'lcuJ€t n,4rrad

*xO '9'Z'T

'*6r rrd o+€+ral+ca+ap
urncts csJurnu rJo+nu IluO 'r-A Jlrrrnrsruarulp e.r,r3 ac ,Hluutp"o"r o,r.r1nd op €ol'B?
-' gruqne,ioladadlosr'uurol.5i3zJ/rle^ru?r4u.)tr1sirp1tr1i,rond,reFJ.rururrnulnndu,rsoaolatJiq+€€+-rsaroleqoetr?.rrparlccsaJlauprJu.lrp;rdoSlqi1ql

-__g_ - *(I

;,rct Y\

,u.'r.rirgrrcl op gl,u5.r1 oir'J Edlr?]rarlca']ocl u'in1a.r uild louroSz op ?+rlalirrlqc'J
'(Nu&;1wc nI TJeos1ur os) loruo8z

/-ieudur.rs'piorrli,ur'nrrros,urJ;::1.lpi).rrlrrz.ur-prJ1(tn'u1aloudrrtS,r,rg-l -('agfa)'u.rrtgrr.frloulaodp+rc.lupr KluEIptsJ ea,ralnd
tsr.ru 'J+s.) Tr opull

'.t(q"nt/\ d xu

u,tsv-t: rnlu.rolcdlap t]IrB

urp p1e.i1pd Bura?ppr cd 'plrropr;ru Flu€Ipur aralnd ap r:a+€lrun .:tI3z11 1 op
rrzuilcl e .xrrrS,rg1 o-.rlrrJ loruo8z/leumas 1n1;od€J clst1 *O €a1€lrarlca?o6J

*c ila?D!1,ax?coloo'T'z'l

Jnultc cornponrrltc : zgornotui Johnson, zgorrrotul dc alice, zgontotul cle

gcn('l'ar()-r'ccombinarcrr zgcmotul d,: scinteiete otc. i5, 6]. Zgornotul Joirn-
${)r1 ;je rlatoteazS, tluctualiilor vitezei purtd,torilor desarcind, (fluctualiilor
t'nergiti acestor:r,). E1 cxistir, indiferent d.acti sistemul este polarizat sau nu.

O rezixten!,:l fi dezvolt5, o tensiunc piitratici mt'die (mcdirr se facr: pe uni-

irrir'a tir tinrp) d,-' zgoinut .Iohuson clati de t'xpresia

(u2) :Llt T R B, (1.2)

Ir:rdc: /ir csto consiarita lsuisi tBcronltuzlmuitLcnLt'tm, TiLs-urtirt.'nYrpaeloraarteuillapirnitrKattilivciinm$eciBlie-a

iranda cll frtcvrnl[ a
curcntrilui tlt' zgornot estt

4 l;T IJ (1.3)

R

l:al puteleir. tlt'zgomot Jolursotr lstt'P :ltTB.I)tr exentpln, pentru R :
40kQ, -B la ? : 300I( r'ezultd, o tensiune de zgotnot V@ :
: 100 kIIz
z-idicES,pLa[,'c. oZngcoernntroat{uiel icplcualttli-clttrr-rsriciotr1:d11t''oslta'arzcriinfzliu. c-Etul aalpiialorer sarcinii electrice,
in fotodiocle cind

acesteft sint poiarizate ryi esttt tlzr't cle i xpresia

(i2> :2qtrIl :2qlt, + truea|-ttt' * 1,,78, (1.4)

rr:rde I ostrr cui'l'rltui de saiurafie, I" r-.rp (qVlkf) - cirrt'ntiildirect iar'

-1,-. cru'l,ntui indus dr: r'atliatit', c?,I'r-' se sct'ir

Q\ P, (1.5)

Itv

utide l cstc rficienia cnalbicd,, ia,L lr,- puterrra raciiantii incidentd, ce trc-

buie detrci:rtii . Zgourotul de foncl sl' dtrtoreazi, rned iului inconjurirtor. Notind
cu Pt putel+.r-r radialiei tl'., fonrl caro cacle pe detector, relatia (1.5) sc rnodi-
fici qi dgviiii.,

, q-\(P, l- P/) (1.6)

"t I t, \,)

l{oliunra ril zgoino'r dc aiice s: utilizeazi, in fotodiode iar in fotocon-
ductori se folose;.bo noliunea de zgoinot cle generare-recombinare. Zgomo-
tul d.a g0nclilr.'r-1'ccombinare se datoreazX, fluctualiilor ratelor de generare

ryi recombinzlrr tlrrniczi a put'td,toriloi' cle sarcini, csea co conducc la fluc-
tualia concentra'1iei rncclii a acestoia.Mediapd,traticX a curentului de zgomot
este clat5, itr trc-'st caz de expresia

(t3) :411IBa' (1.7)

i1 aceastd relatie a :$ f"rl| :1t"Vrllz este coeficientul de ampii-
cfilc':acrteroazlirfocto-cotidrnupcutol rdu,lrtivi(atrld- ,elsitrir-tt-nsmiunoebailitaaptcliacaptSu,r,t57,-tordiloisrtadn,:lsaarccliinndtr,)e.

_ld

6T

,Jol )rl;po?oJ 'INI

rilun Ie lotuotz rp In.r:i"r3ds _ .q.Z.I .FIg oaa-r-l-nro*llnroqe8+lrJoocczoEsudorlocar.r+rca,o€eqo€ra5o;puurprzJor1rnJ;ald,eonotlrsmn1prlqo+ndu(€"dpgrio€nJe"gI+lprnnoourel?plrerIuJu"nouqero({?dup+Fuuxr:urzoaaua^o8ssroJ;[{z+nrpl€oeonoe?ppqKA.or.aor+1oIJ+,pnurpnuo1oazp+oot€s€e8uracppzJr

*-9-6ot :i1tii ! z'rr i-ao!-oag

oor

3ali _ uJc ^l (c'r) '(it): 7t

"ril

\al l u{e1o,r qp aqiqo
?'qno' atu{on5qzaro'}rilgg+c€+aopa+oap1€r?;rrau1r,[eoludg'a---as'aongsapp"ar"roe4qr'a(pr,'{og.r.rllteoeou'lfr€1rorp)pbuuF'eeaouwz.1.rl5r'aoletizesepsp1eKeoaKa."uprlrp+aorouirlFuInrpno{+edLl+u€u+uuoArn€"olrdrep€qoroancJon.ro,crlqcrsoaco.elpdaeneuqrd.ong€rte1ro?cscJloonpaeN18d?1
qu{'KIncI?c

B nr,1rod

JolrJolaa?ap .lolejrruur"rog.led uo.relrurlT .7.f

uI ''.;rsor+lctao+iloopoalorrnlrrn.rua{dr o1reoql oour-oFz"JapI*-F€uX1a.u;o:dl€sa1rq,uogo,uaBz{eu.rodlas;rzJa}.sroo?Qso6.A1 -e,ornp_uqrn;

.?t : Gt)

.r =tqv

- - /i -Ir--'1rar1i3{cu'-rle1r€uurq1rr'txpaao?rp'ourd**pi*o..lonriKdlrno'ol;ur-d.=,l,osocprr.p.o"rJaoEJt'1o,l'r$Jrr?fl;ss,u.'rgo'*#zc,"€retaorrr5o1t6?.rn31i1}p:-1pi?*ipi""eFt:zo#,riti,lru1u;1"ir1r"ird':.,t.;*i#prob1r1sro1it,_t1.1iE..l,q5_lJr|oT.-i,r,+l€"r+oo*s?ouisBoacnJrca-:psi"ipe"u8dunaL

(e'r) : (:t>

'1'ruo5z op rnrn?uil.rrlc E ilrr?€"{+Td rorpour r o?s!)

g1e;r'uos Bln{uJotl

"JiiHiTr.."r;i;j,yIr-I,l'nrpuo?prt,rrorn"t.orriuo8n,cl+Icorogn.prrup,ltdr'uceouroi5lruncnzaoaJ:oeialop.farT;;?rrteonyu1Iarlnon.pTru4drr1ao.c:.r.u1Frao;uzrr.Jaio,anurfooBncdcls+ornq,uJrccdro.lr-gp\rrrs1..*),rln1r.o)ruSia1leuu.dlrfair1..n.ro1,ip*rirolcle1rleiarnu.+i1i9rysox.uo1iru-l;y;ro"d75up.'7!*i",:1urf1n1oilo"r*i,ir1oouiq"p"17aa1-np€p+pnuoIa,citlsoe:a?nozrJnir

7.4.L. Ltm'itarea de cd,tre zgomotul ampliJicatoru,ltr,i

irr carineaIce:stIrc,adzaptednetlueuxnpfroetsoiaco(1n.c5l)ucmtourltip(il?ic)aetSst,ecduat0..de expresia (1.7)

Se ohline

Pu=P,:-!!"B-. (1.10)

1

7.1.2. L'imitareu d,e cdtre zgomotul de Jond'

in ii,ce'rb caz in ecualia (1.7) se introd.uce valoarea iui f oblinutd, din
(1-6) rntrltiplicatzi cl:. d., pentru P, 4 Pt

(i2): * q B az ++

inlocuiud aceastii valoare in ecualia (1.9) osi Fe Iz dat de ecualia

(1.5) multiplicati, cr1 or se obtine

P":2vDP, (1.11)

unde P, este puterea radiatX de ci,tre rnediul inconjurir,tor' (nu cea care
tretnie detectati,) care cade pe detector.

1.4.3. Li.mitarerv de ctitre ctn'entul ile i.ntu,neric

in acest caz iri leliLtia (1.7) I :1, este cnrentul r1e lntuueric qi clin
(1.9) 'e 6l;!irre
r) lt, llrtj iJ,
'r,(l I a (1.12)

P(1e.1n2t)l,uutrijl.ioztientdrioirlullofi,c,tu1l1rc-,orlptaleicssit'ci (1tl.t7tl)qrte' laelripare(1s.i4i )a. naloge cu (1.10) -

7.4.4. Limitaren ile cd,tre agomotwl amplificatorului
(rl?) este dat de ecua-tia (1.8). Din (1.9) rezult[

-Pz": 2. t'' ly[Vng--. (r.ra)
t
"rte

L.4.5. Li'mitaraa de cd,trre zllomotu,l Johnson,
Din ecua,tiile (1.9), (1.3) qi (1.5) se obline

D _ hv 1y[+kRr B-' (1.14)
"-it11

unde -E este rezistenla detectorului.

20

IZ

4--ou6.rroopsouu'ooq_udIrn.errpor{+umcqoFp-+eoogpor'o+JodK+c€r?zoT€prorJo?+J+Tc€or+ouccoaurlnJoocur 1o6e+ospJorutlncro.or+lEgTdruco,rgJiocnlcscuo€rapuluvrdlalsrupo ecl gsrurr.rl r*
fnop ulp +rnlpclu Inruolsis ur:rdpurce"r+.g esrns q ep erferp€U osar oc for+€ur

.ego.rIieuJhs*-i*z1uyrqrspo
lnl€lrroTrr putsolo] ?J€osfm os Jo?co+opo?oJ rnun 1e le.rgceds lnsundsgg

rolrroloo?op rollolxslrolouJBo uoJuJnsFI{'g.T

rnlnJolco+ap,r?rJr? r* rfue1.-rze.r '?trrrurur ro{uJtesrocl€rayoooqJn?srl?lpptlsncssnppso"arlculo(dpuno1u
op lnlourooez al+fc op o+e+rTrrrl 'plrquenc
aplcJqEdst rnlnro+oo?op aleiiueur.ro;"rod uc n;luarl
Tc KAJasqo "s 'aporpotro; ui r*
as sns r€m op ellr{u1e.r tr: ro n.r+uod

(orr) 't6"blt:l 4 yrg tr"n

ouraop (tl.f) ersa.lclxa 1?c 1aJ?s€

(srr) 'T. ' 'O: 7"^dI:t

-calap Br.r* T,- nc r"i puog op ror{urpu.r rB.ro1oJ op InxnIJ r* ;""Tff*"!nlnrog
_cnpuo'o+orolaiuuu;roy,";nHr,l$J#!:,ffiJ,?1f ;"T.?liJiTjr;,J"ff i"lf t";

(zrr) ''"d> aD E

trrt^"rbUl .

-)unJ op ,Flurx€..r u.rnqe.radrue+ Kz*alio,rr ,, "i'H"j,oi',i";:51,i*#";'u,""t+

(srr) '/d > nbttg

j^u

rrc rnlnrtsur'on* € grns'pur ep p{uo,r.ce"iJ ap Bpurq ri elulrun uffir,ifrH. i;H
+Ic
forlurnc p{rrarcr;o o fql€ KS lrrlrlrro+rur ub """o (gr."rni e.rirb"o3

(grr) 'r.f > V

{I^El

ro.sro(:tIcI'nI)prloico(alof';r)n_.r-lu,(orcrI.rI)€l,{(aO}Gr.trT) aopgrr{uliriep;ur oaaroaplao^rEuo;+Kprur3rr,nl.yzE.pcuo}sJaco,Bp u; ur{qo

ui4uipd;r
uorsepcuEro+"&'se+quIrqucroJIItfs1lun0rlrroruauos5rozoF'r-+ezKpcaFJo1+.pu?oc,lFtos,p}d€r+nrlIc€uasTimagraJo;ouaur1non'8_czrl,mlagpcoapppfIunroe?lluuIuo-lJi,utnqicucao{41e^n6Bu"crroer1.pnroapl^e1raiui'e1gr(*prreyj
-Krpulu?rJ€oTsuurl'rr3rl+rustrsoracyro'lpnudoJ€cep€rInuo+loquooJ8dzeourn+dFcoospniEo+"rtsu+rJIuuI{f
orJ 'gs glrqts?co+op r?uts
e1i
rr.roqoe+3p €T

yozu.afio ep astrdrut y).ralntu apr tr,i.r,puog .g.y.1

nalul eules este trecut, printl'-iln pieampiifioator Pl la instrumentni de
(f;iig)ntlari,in1s.4c.riTp,tarlrte[r7n]p. eCriarctuuriitujol aesleecrtreiczisat'lednei,taecdteolreuclutoiretlslutei
rnfi,suri H sa,u

reprezentat in

Fjg* . 1.1i. Schcnra instalafiri tie rndstrrir q li'ig. 't.4. (liicuitul clectric al
rispunsului spectral.
(ictoctorului'

devine foarte mare Di rezistenta do sarcind, -E, din citcuit i,rebu_ie s5, aib* vzr,k;ri
cazuii de zeci cle IsIAar.eiMnde,,nvliaoliorlamreaczmi ianxi.mea|z,ual ,caincdesstuemianeasltuel
*r"ir l"
Se culege""edleepe rezisten!,a de
atunci iirrd t-oristenta de sarcin5, este ega15, cu rezisten!'a detectorului'
CinA rezisten,ta cle pe ca,re se cnlege semnalLll depdqeqte valoarea r:ezistenlei
irtcmlneodp-,iesneotteAraPa"raiire,ne,drldei*atert*puiei*m'xr".aeep"macdmptir,le,uirleti,ifemitfceurparnnietsicondituriaaounnnleui{ea'ieila,szcrapni"\toiuicnncniasrcfiuivr(enfisitpcegaelt'iieento1atrrd.op5esdepJutres.c.uAcetrplsiaro[--iridE.cs,iiefraacincudeloitecturtueenieccqettrotraeernuadzluideseittoe'lqrlae-'
torul cu un altul ie referin!5, a clrui responsivitate spectral5 relatiYii'e{}.)t
este cunoscut[. Se md,soarii, tensiunea t1, datl, rle cletectorul de referinld'
astfel responsivitatea, relativzi a detectolului
inacelaqidorneniuspectral qi o.s(}.)fr,". In rnulte laboratoare
neexistind u.
se g5se{te din reh,f,ia o(}.):
detiector de referinifi, cu rcsponsivitai,ea spectrald, cunoscut5,, becul fotrosil

F-ig. 1.5. - Circuitu-l electl'ic a] tietcctorului, cu adaptor ue impedan!5'

pentlu ridicarea caracteristicilor spectrale tretruie etalonat la o unitate

t;ficno[;afAel-roclaeisi"ca'ei'nlt-ie,zd-rapiui"sil5n"tti."oc*maiAtr"ocisXeipflaoesrcctlir,ts,aroa-mvilandaas,leotoracanrunruecenaaucuza1eip,ritreripires-arcmliuxnciicf,rirurne5d5f'eam)illc,taeu"m'l1aie,nr,ei,ntsn,i,laifatusrteadnrotdecderlcaaiweatpoiondurle'tferflDairlgenmeuagr,eiarmxattrrede.a$imaas.npatdlStuie,''
,,

d6

-(oa'r) ',,,.,{ 11",,[.(+) :, utz.t!#rrr] :,r'r)z = ,'i#

vzvarnor*D es (211 1 ep p{ue-taorJ ep rrzuoq eaurrs;rp1 n1 u*n*"*#i?;iif ,rXlH
-o8zep Bounrsueor ':roleleuoF q ep In?Tnc;rc alieun;d
o a.rrc ad a,r,e4ur e1 ep
rsounrsua+ ri onial €I op ri?aunlsuo? oJturp lng"roclu;l nc ap
leFe e+Eo f! .a:riier el
es r* (rolco1op ed op€c
tsaunrsua+ FJtscsFrrr op Inruourop epur"ldnc ri oJ€c rarfeipu:l u sJ€Inpotxl 3r) 1o+
-uo^coJJ 1n:) so;lo1ur gJrqer.rn,t elso glue.Lco.rtr rrl.iID {l
Jo1l3pcso un aJ€J+{r{ El Kneslcalrca es dcos. +_ctoc€ uf .t}rrreJrc mp rnlil.rc:.t3orJ
--Dr1OcJ[JurOeplqIn? r#&oaI.IlI€ocprFuld1 r(nou"uetepr .1u;aptsuoc ginori
Iunlj.Te;partc'rarao'1opmroodFez; €uruuolep ag ir{rpuoo ortlQrr? ilr
,-tBrlJ'lt3sousrRrxruo.ordg€ '1a1,u.rudrrJo+r+couo0_,axrncolul ap €onnrFluel
oJ€ oJrsc K?€ulqoq p{ua1o-rza;n 0
-olur os 1i guio.rus ap'tuLiualsrzo.r r-( ;ola+uoruolo refiialsrze,r Eelec{€a
-rsucc 'ufue,rca;r; op lntcourop ed r-ic-aaluouralo'gnof o+riao€ ,rsainc
iccly .1,e.iap
1irni{;rrloruieooalop-a+lsran?a,eir'oir;u;lapelrciaorsaaps
;0o ;1ouro;L

oee;prelo3euno:ruuo1niirozsluia&spp+ru?FrJJeBalnopsdK.auBloroserJ€snrnsl3ssR?(rrp?ru{o+on3rg+.orunpoqpdul'ruliigel.rrapose+,;oy)zsvlluaaepziicterieuulrobedri'aoinsulnnIirapoai1nueln'ioJdroa?ar?illueaa?rpoutp'4r
rrrurnunlnrnsruo/Ba+J+cgoadl+outprn-IrFI1I urituyro;if+Fl onaercd+sutselandosclucndl]dsoisJ,igtoiz.ircrJrr3qcJoEtrslfcJoa'lltls:3rDru/rn?f{rKi)uaCb]rpo'I.JnieoecSJEnrCa,i}uItusnea,tl'e[r-pe,"ri,err,opa}u,-;riad;atar,aiur$
dlsa TJprrn "1{fa(ol'fo llo{)oa(!)'n = ({)n eriLlo,r urp ga"udc1nlr.rr1ieu.r,t,r<rjf ciue.r.ro,r1 ui
l.Lruouroir
{nsundsFtLrnlnro+Enpour relua.rce.ry aleoa gjira.t
-c3JJ rnJKc E l€uluas sp.roil,BJarro"3 un eJ ap ginnrfqo (/)uo pounrsuoil ,fJn.iEur
uar-TilrJpulpJte?.o+ro-olustBc?,aHlosunui.rzprqnuooJ€aulssJprulo:ura+[orr/o'giJeqJ+c{euustc€nerurlaeucrznnrarrcoJorIJpn'K1e1l,a*tct'rspoooi+.sailacrKrls{orcree1rrusreJneFpu},-1rrrluo*nrnrstr:rrinunpnilrnncp:,..otrJlqrsorcan?goc{lrnle-rl,1paoie/1c;ipeorr}cJaln1onleEs+s"{r]uisolcne1a,orezcpsclns,r.a,e'relluulp1noocrpoi;dpons,ulru.:arrnis'r"(}d/tr,)?il%[rn.s/1r.

'nlr![rs Lrrp ro:]slzLiuJtlojol inllt Ill 1i osatroruo rnlnrqoo
1u le.rlaacls ltrsundsr.r n:r arfu.ruch.rrot rlj ')trgtg .E$t.I.ru.3EIJ.JI
-Io,!l 0p lrroilrElrJ 11) rnlnrJ([ ror1erpr.r *e
lnlqtads-

w'{'Y

tfz r 9'l ZI s0 zb

nr)lts utp 0,
JoisizuDJlo ]o i
orl

as

1"- l"'ifix'l *

eleluezarde;r lprunullrnssTo[/lu}o'uTJllrr'sotesIJ'qBu1(I-yre)(araimrg{qr1r'ceatdn.rrl'rnu?JoooJc?€oCni,Jor3+lo^rprorid;ieu,'n)"c"afe'lnaps:upn(t1udss)ra,p.rJr'rlzpnrT{omr-".1rr.e,rrnr1sru_?uiri,prf
KurrrrJoqap as
-o.tcouordr rrn

m-uRn5-d,seurPerZize,!i.sn,-t'tiernru4t,-Vaa,TcgdRuelsr,tBeei rcptteuoeslrtuBepiulziisn,geo1curllnet-ioltieztubeclaatozndrdda,datarecdtlleeacllfireareetzcevisnetsenitnidrtn,aeaaclsre.iisestaepromclianurdlizu,ai8re,"id.,

B: J_l*let/)i,o/, (1.21)

unde G,o este valoar.ea rnaximd, a coeficientutrui de arnplificare al sistemului.

Frecvenla fi a centrului benzii este frecvenla la care G: G*. in eele mai
rcZnuguoflmtecocatuapzl uacnlreatBmecestoterruuialul7ci lu.sperrinespreinztirnetXfresucvbefnotremlea.f,unq;o/i',-claarbcearZe(GI, :fG);',i,tlfl[lt.

1.6. Fotorezistenlele

se mocTl.iif-iclciir,ejz;.isu,btean^lacliusnaeuafotatodciaolniediu.cFtoorruml aesotebiroynreuzitiisl,teanftodt,oareczdis,rteeinvleailoeasrtee
paralelipipeiiic5 (fig. 1.7). Circuitul de polarizare ;i de md,surd,
zentat in figLrra 1.4. este r,epre-
Semnalul de rXspuns la ladialie se poato mXsur:i fie
ca o va,r'iafie cle tensiune pe detector (fig. 1.4), fie ca o variagie a tensiunii
pe |ezistenta de sarcind,. Se poate, rle asemenea, inregistra curentul de scurt,
circuit care intr-un fotoconductor este dat de relalia fSl

Iro: d h q(h '\^ rt, * Lp) ,p"o6, (r.22)

unde d si la sint dimensiunile probei i! direcliile transversale po directia
de ilirminare (fig. 1.7), b este raportul dintre mobilitatea electronilor'p,
usni eaagaoplulierialotdr,!pr,ei&prro6bi-', Eci:mVplut,l electric prin
prob5,. Nobindl eu Tz tensi-
unde I este lungimea probei.

Curentul rie scurtcircuit se mai poate sorie

Iu,: AQ\@ q", (1.23)

ul'4:nit-c)leiea'flilcieoe(snstleea aria suprafelei pe care cade radialia, Q -defluunxufol tdoen fotoni,
cua,ntici., (num5,i'ul de purti,tori generali
absor-
nunlefte coeficientul de amplificare al-fotoconductorului si
rcplezintii, t'apoi'tu)'clintre numd,nll de elecironi care trec prin circlitril
extern ;i numS,rul de electroni gene-
ra-,ti cle racliafie. a este egal cu ra,por,tul
clintre timpul de via!5, t al pnrtitori-
]or de sarcinS, qi timpul cle t,ranzit al
--rln',
acestora intre electronzi. Se obseiv5, cf;,
dac5, timpul de viald, este mai rnare
rlccit timpul de tranzit, cc este mai

\.--!.,,- J rnare clecit unitatea. 'Iimpul de viald,
fotoconducrtiv este detelminat de tim-
I
pul de viali a purtXtorilor majoritari
Fig. 1,?. --(lircuilul clectric al unti
[8], astfel c5, intr-un rnodel simplificab
fotorezisten Ic.

24

v6

ael'fRAol,rrrl{.trlesiluo":crlms:"Fr.aqeuctoIateoseoupfsorun.tr're{,adturlparuagnaalaglad;qeEEaopaJ.(ruSI'tJrtgrre{aJcaor'+f1{psro)tnr1sapr.l}rrsesgs'a.autrrrsa;crgd,eurzxllr'loEaa,}rLJruluaar?lorerIornrfrlpl}s.paruroo.e,4oIprp.Sucurarl{aaIeuupulmpourrrqi,sie.rlru,ic1^toooau.?V.pr,il;a(KI.)naar+to+lqLri+uor.uso6raanrluTc+unrfsuJ-uaa.oo,fan,cesZ1u_lanel6ll*s;i*ral:ne1"apolroloc/ur'u;;rr:a7art{5l:ro,rui",pnnr7nt1csi

,(srr) ','(.'"ioi)'l'"lJ"] 1-:,J ),",

anr{e1o as ,(?+uI

- ftpr]ur alsa rr i'r:rpul) ar{elpr:.r ap .-lncl sp- 131go.rt[ u.iilnl:,c lcllilt a_r fcu([

.]u-*s-., -..

u

a-alu,rlrUrp^JirreauJ+sJrncpr3nurS.'pI'r[ua?EopnJ,crEc"UJppt1irr3urc:Dar.lJllsel0arpzar"ranea.!r?fU]uqsaopodlo"o-rospizt'r{frr}ila.c:Ft?ssaBaB+glpasr-^auInrlrr+{"J,n:uJfsc1nJJaplcr"lulrcououoqc"rp,lrr-nI'KcpJru+icr3uqqr+pJer]€otc{gqrobJ.Fsulouoe,anroursl1es+a€qaao.roJJcdar;e.sdrurr{eouJa'uctauaplngrscparr}qszue,uao1ri".oulr1rofdoa?i }alposeJo}ranz1lepsaIr,oe1rJ

-urud watj otaz €I aprcs Elsar' ep..* 0.1 su;rd ep Rpun, op -".rrr;lrt..,|"t"d;i5
Eorur5unl n.t ro& FrrrlJED. ai: .ro1r,rolpi.mcl e pi,r:r,r'ep trini",l ilc
'rerfurpu.re EpunoI)
'uqo;ul ecl rauntsnJ+ n.riplrclrosqr] J.2]uurpe,rue.rolndncldiiorfo.rdolcl
pltarld'e

alsa +xncJrc+.rncs.lp JrJlseloo+oJ In?i]o.mc rJJ{r',rru}Irinl r?zc:ir,!;]+so r spun

(l a'r) zlc1l ,L

'4;:-i u4 b U"

-sa.r iJ oluocl {SA'f) uiriuie.r IJ i.rj+st ,*qVi\.I tlu.rl}I (liti,{ !srJc

-q'K)lrcru[,oro+sLq}rBapuirIin,uxrpuri;dr JJ+1?C
ap riurauo8 n.rrirprlJorll{ "}p Jolr.roigl;rncl oprle.rlue;ubi 1u35 dy li-,rr,y apun

{sa'r) {r} }./{rtv 4 t{ v r1)gdr) y pt:n

(aa'l) ;o*r{c1e,l ra.iu.recu;o}^rrrp F}Irlzo,r r rnl rui ll,{p*,riaeur.ar raTprrln*ci haur.rqla€.]rldsaxJrtj tl tu
'r;ru1r;ro[ulu
.rop.rc1E1;nC a1]un

-, J1

(r,a'r) ad:.

ar.ils aluoe{ a*' 'a,rErrrJn r.rr.rd 'r"t'Blr.rofeur ;oii"rolF}anrI ra},t3+ilrriow alsa ri apun

(ra'r) , Jn -- "' --t,,
aI
,llJapisuoo aluocl os

Fotoconcluctolii pot fi extrinseci sau inlrinseci. in cei intrinsecri pi'in

adsoltrlia fotonilor cle energie h v, eel pulin egali, cu l5rgimea benzii inter-

zise Eo a serniconclucl,orului, se generea,z[, perechi electron-gol (fig. 1. 8o);

j'rr-=-T-- H

El hu----p4

c;

Irig. l.iJ. Proce-ce do gonerarc a purtiitcril0i lilteri in scnriccnclitc[c;"i.

lungirnea de undd, ele prag este d:1,t5 de relatia (J.1). Fotoconductorji extrin-
seci sint cei in care energia fot<lnilol mr este suficient5, penii'u a g'eiler'tr
plin
perechi electron-gol libere, ci "qe genereazra f,ie lrumai electloni liberi,
excitarea aeestora cle pe eentrii in banda t1e conductie (fig.
de impuritate

1.8 b), fie numai goluri libere, prin ercitarea electronilor din banda de va-

lentX pe centrii de impuritS,li (fig.1.8c). Pentru fotoconductorul intrinsec
coeficient,uL rle amplificare este

(vnrn -l- v )r-

12

unde rR e.tte timpul de via!,L a electronilor ;i rr- tirnpul clc viafi, a golu-
rilor. lu genelal fotoconductorul intrinsec se poa,te realiza atit din semi-

concluctori intrinseoi cit;i din serniconductori extrinseci, nltirnul caz fiincl
cel obiqnuit. Contribulia purt[l;orilor minoritari la procesul de fotoconduc-
tie fiind irr cele mai rnulte cazuri ne.glijairil:i,ct este deforrna(1.25).Iierr-

pcnsivitat,efi, de clrrert pcate fi scrisii,

_&^(1_") I tl ;',,'-;7' (1.Je )

;:^ ',

gi avind in veclere relalia (2.2it), r'ezult5

&o(r"") :a-.|]fulr' (1.30)

f)in relaf ia (1.30) .qe observ[ ci, r'esponsivitatea cre;te cu creqterea
lui r;, a lui r qi a, rezistenlei probci. Cre;1 erea, lui r; se poate realiza folosirrd
un strat antireflestant, ,5i mflrind grosimea detectoruh.ri. Pentru fotolezis-
tenla clin HgOclTe acoperitd, eu un sirat antireflectant de ZnS se ob{;in
valori ale lui '4 cuprinse in ilomeniul TO + 90o,,( [9]. Pentru ca performanlete
fotoconductorului s5, fie limitate de c5tre zgomotui cle foncl trebuie indepli-
nitir lelalia (1.19). i\eeasta implicX valori rnari ale lui a, n, R fi -4 si tem-

26

n,

'(urrlgg e1 rnril) 'tr1 op ''gpun op rrirr.fiunl op orrm rlruoulop un r.rad
-oce eluod ailpOFH r€rr.ro1 p",sneluoc) ariou5nruro.r+caloo+o} lcora ap gzeq od
aa.irltp?LCroFr+Hutsxrnrpc[nlo.rco?ncuos+acpr,t'K1ccortprai.oi ,r?rsd a1e.rc't-rrJti1.ur'eu€ruuineste(rafrjo.uge.ruenuol'rtaeecul oBurTas'€rr?acrpuotl,oy.Jr
-l3ouortrcunI a.rtsr r.rc)+c31op JolTr3 ,13 ?icatr) {Jq?ru
:-oloJ 'l"n)uJpn:)e8.lrl rullcrtnr rrJo{'t.r(ni.pl u.;o-IcrI
tr€lII alLIr,THiII ep ottlllJo E,{.OIIO na luIS J[]]tA3ap
-OJ{}J IlllsOAt| Ea+t?}I.{lr;Uocl,,ial t* EA}B}I,\I},AIACI

'1, !!z71-suro sOr *(I' uo]ts+r^r]oalap ts ,ca/rr
op ounrsu'd+ EI tit)+Bulrsuodsa,r urrlgtgl op Eplll
arao3''o+cp6pp,lX{u,up+piil}:33Ciel.are.ru,3lllt(tIa,r1r1oirlc1J)(5n1ri'Dluol)u}r..rIl(ulr)nr'(url1):c'p:1nr.)olrc,'eo!lii,andlp}ro?ltunos.r]rlcrpEollinq..zr1ocrolaln-ppJ+oE(,sB9ripa-aoJ)n.ci+J+s'ellnczsd&urnru,?,r"iprlllpsniurrCa(zrrog"uiucg-l)nrct.igd('.l.5rgroaolxgl{)1ppr'ugrat(uurgit)dpgEr)l

-e.r ad lnlnJo+ta+ai) tso,rt3xrr n;1uad gurSp.r (5)
''-([c;Onctpfltu]ropiuceo.tril)ofJnf..r+rrol8n?c; Iaunlorrpupo/irr?nuJrnorpnpi?,cEuJornp+1,cprcrulpJe+rcosdrtJrl.o?g+z(E1ei)ua:auz1oar4.rrisdcorotinyrars?osr,orr.ein6;;l'cTor:JBtpJ.1jrsnl.oFoe1lro;1+uuuaIrrpuo^lrCt]
pzte'oulorJr{ocJu.qno}uralu.rtrJoJo+sf"uutlJso"J-roqpdutrdIise,orofo'pa}c''r-uIFriF' lII
tounrFe,r u.r +B glt,ltrcads

r.n3r.["re+ .rriricl

el I'O s6e aJE'ople'o3I-I
LL or 8'0uS z'0qd
ZI r'0
LL qSUI
I1," as'0 q6r svul
6t'0
Gb €z'o q6r JS Ctd
z?'a
v'9 t9'0 962 :- clcl 67 ti,0'0 qS:IS
g6u a,J 86 6tr0'0 g:Is
6',2 7,T'L d:IS
,,b(, lt- 8e qFO'0 SV: ]S
8'r sg' r E6A SV€:} IV: IS
L, I 0s'r 96e cJp:) t.a r[90'0 III:IS
8'r 962 csp:) st ss90'n RC:IS
e6 '0 .qx 90lo'0 uI:ls
88'0 T8,7, 962 cIE) !_r t6t0'0 T

6S'0 v'z 96U sp3 9SI'0 u
99'0 0t'€ 962 su7
z9'0 -.Ia
urri 'ov rr .I-: ri ulr.rndiirl III.I
't'0 : JolJnprroJ{ruis
j
JolJnptroJrirrtq

l5 I* IS rr.lol)ripuo)
rJasLru?Ir! rJolcripuocoloJ ?] rlBZIMn -Iru.)s ur .8e.rd ap 0.{ Fpun rp Brurr$unl 11!
rJolJnpuoarulos Joull o[!crls]rJ]JE.rEJ
.ru;tiylr.nrdtttr E JJEZruot,rp,r;1ri.1urr1
g'l nlz4lDI
; L DIaqnJ

-eucroncaduourgiclrrInnyrrlrcr+rlIna"rrr€lcFr-Jtroic+ncqnpousoscor.utors+sur1o1lutsnur1_,icu1gua'rzcoo.rsduor;JJ+uuilsr.rto'IJcenplauqo,ru{it?uoJl

'a+lurTl rt?ur r.rn?€Jochual'u1 euorfcunl 1od rcasur,r+ur rrJo+cnpuoao?od

liq'c*.izure{l.gara1u:rol:rr_n{ooduirl€un'zrll.trrr-uorloor+}lncofaft?lEJ;ouproru,krrr,ilu3ipezrrscunoyear p'a1l{ipTp{ur1zc1rdi,Jo,ot[nppodoloutrSrg5r.rl11iot1iuIcgoSug-rounl1]oBrSpJplusr;?r.€c'uirlJn(oSo.prslAsBFu'oTpcfJuqrn.olran.q..lrllr$,.Dl]aeslurdorsJiu.o{rl;r{rF){1non€r-1l

]lnu-r rtiul loJ rcosur.il\o rr"roi,)n]!u,1,)()loJ d.t lltrU 'J.r/puoii,)rrnJ ap ospof t"ur lu,re rI

1. 7. Foteitliode

in fotoc'liode aliare o tensiune electlomol,oale ca ut,rltar',e a separ,.)i,t,ii

electrotrilol qi golulilor', generate c1e la,tliatie, de ci,tle urr cimp electric

intern care existii in jonclirTraea p-n, in clioda Schotthy, in dioda p-i-,n,

tinatihr,etienrofjiog-urrlcaNi1u.n1i,0e: tjconl.c{1ti.uCneoanspl.r-tzctja(ftilgiv.e1rs.1e0loal){,otdoioddioapc-lei,-,ter,st(efigre.-p1l.e1z0cbn)-,

ctrl.i1o0dac)p,-ci-liroarl:irnSccihrr*etlkih1r.rn(ifniga.re1a.1s0ecfla),cetliopi'lar-liarlneel teanl-dp-nlam(firgl.jo1.n7c0liue)n, ici li1ofrilga.,
cu corrlrrct punctifoln (fig. 1.10 f).

,!4etot n,ai'(h;it

.p+

n @' j-t,+|r-yL-qTraqtym*

b

.lp/+ hv AR

L\ r-
-:rzz+z;7-z
lJ =t A

n+

ht\/).r/ l4et o I

a!!4ffi Ji

i i

-:a:+r: hv _____ __,_i

fi*Io bj

l:'iS'. 1.10. - IJir-ersc Lipriri dt'folotliorlc. irig.te1r.r1s1iu. n-e (laracteristlca cur.elt-

a unei fotodioclc.

-l(.^fri,.gp.o1Fla.o1rti1oa)tatileoecrtliaenrp.c'oelaal1rs5,iei,,.ftulCenacerdaxiopcnrteeasl.iiscatiilctalet1e-clt-orafilflo'it,otdeino.cr'i!ueniee de polarizar.e sau
fonc!,iune p-ia
u

I - I,1sor';*t - 1) tr",

usniucnleea-[,foetsoteelielaottl'oclreneoetouailrteiaet-rs1t.e51c. lTaetariscinieneyaela]atiaeircuii, deschis, aclici, ten-

uucle To:IL' Rj (1.31)
d1 tt I^ (1.:12)

P dt,- ,-o--it -

Itt'otlusul B.l eare calactei'izeazi'r, perfomr:r,ntele urnLi cletee tor (pnra-
gla,ful 1.4) are pentru ,ionctiunea p-n vakrar.ea

RA: tt{Y l; (f)''' * * (f)'J-' , (1.33)

28

6Z

t:frsd.ir).'r(glcgaogdpr'sfnu)elrn'Iyn(-'rIlgnidcaIrg€n+ualngsntqn1r+p4)ou'ua,i)rf{dci:u{o's1ag1qp"d0re0ooi{4lu"t++4l ,gato"g.:rr}t€g+}X;ulr?on/zAzl{eere.'"rJarrdelde-r€u.Or-os1t+.u8lr31nIsp*?6eIrn-r'O1landfaeu.u9.rrrano115pret;ousu.i-r10a'(nTtrgp.T'fe:)1

I'S I 9'ZT 'o lroo'o l.oo'o '0 fzi0rI ''z6 crpc6H
tL0 'o tIttor''00
Ldz, 97, 'o Izzo'o iueo'o vOI'e ?SUSqd

8Zt cc aJusqd

lz,ro'o lzto'o

6e or-nlrru Io:ualtut \oulluI

Iiil

>I LL vl oJp3fiH -I$ asusqd 'aJusqd rolalurrolBrrr Iulaulurud

,'I DlaqDJ

'[ff] 14ff q t'f EoqrB] ug l'ie'1ueze;rd 1t1.ia1eur ep ilrlorutsr€d putsolol e1e1
ar'--'-1a.lurppral.a;co1r.udrJlerzoip1sncel1rqur.o*oSrndOaopaocs1,lrrru-ornldi€oJoIaeseillorcrugJl€orn,o,prlltrooao{-3{aclprt.$€srun+gaznoccrrf'lnalrteusJpngle€aou:urcurol1g€1J}uaIoo.qeFrJp+od4illor"ntlrtsrrrrlJolrnrrerpeyldr.lltriergrupoSuds+lroolurcol1uiaoIqce+orr'a.19Isarnpeu1oIl1€BedeusjIllua.u3I'rglaeeeeo?1zlruuelueaso1r;roaciuq'aci{luctr"'8rp,ua{ironr4roleSrgo(pa1.9umel.aqKoo1?dozqt€t+olt;czsapqsasto)tlustl-srt.olrrrrap,g+narou+'roflala:pc1la3{s'u1monIae1lrJ8auolnuuertq.r*reraquonodgcrrI;
r* fa r-d eounricuol n.rluad ll]{? eFq€IEr }n[s r'rrs {'t:l{r ap airt{qag 'Inln.to-}
ol€J alrrlrptrl oa+sa ((Z't) tril:tco)
g-roar?uoaFpzBaop1ts(]jq]rraqrlsvu^oIrslrgace€rorpraXlnzcval no.pra+lacaw,r€rcp p1t5a1 purlJ
tto]'uJr^rlca+ag

(se'r) ,,(#)l#:uo

ersarclxe ap flup a+sa EalB+rai+co'1op r€l t(Tg'I) n:ii'r:1a,r ap SiroD lnul{ .l:-s apun

(c*:'r) eq "tdrQ,: vLD

raor'-(btt -

.l:rsa"rclxo op E-]Ep o+sa aunlstt?+ op l3olurl.IAlsuodsag '1'u1auI ulp .ioliuoJ?coia

{u-nrlal;rauuJrdrrrr{ra1radrgJrui1o1eplejSIpan"i,,pJr1Jor{nlarI{,iproou+nporrt-rFlqp}cpu{,.ro1reuc5prqil1lrcoerlogtrT{ru'aranpI11nroizIed€aluclasepauliIruro-oi.'ttaooi4slro1r€.z1}qsJocaeq?(ecsuTrglufJtr1luizltgurt{.anu:1qre{l'r9o):ua1cu,tIstrrn)c.85:p.rrr*g1l1a1-Jgap-otur1p.q1rucu?an{ql

(ru'r) *Yb ,(
'Jr1,'Q1b? _trl:l-U
-1
riqruiren:rs-i',rrrd.iceurpioir''zrdreu1-'retrrlarus-nu',urre5Ju,?a+ta",,u,rrrIrl€ilgoiFaln"ruBtorllrscp!o'.s,tatr€toalsa'l1ucYo*nupEdlorp8uJlnoarlrsuri.iennrol.rprr+Fo.orKapro;+curf,ol€run;uft4cl1rpla1Jae1Jo1roo{loltqIJ:ra"corrnpg?'lI'rgioig€e1Flpclrlnlourcd1oiLpco"erupoonrrg.}{rsue+-oo.lrr;got?+.rdcTcrt,liaaelrcaSpuro"mIreci (r

C

Ii.

I{g{'tl'lt'. 'l'irnpul de viatir s-a lonsider':rl c[, este rlettrntinal, de recom-

lrilra,r'ea, Augcr' bantlX-bzrntlir ;i pt'nil'tL caieultrl la diversc {.ernperaturi

in conrprr;ii PilSrLTc si I)bSnSe s-au ntilizal relatiile i1?l :

,1 t i;r
l',rr?! - l'lrn'2

lll ca;'8 5-t llrestllnls i',r: )'r,: t,tt url<l(' i'.r estc coeficicnt.ul de recornbi-
rlru'o ,i1{"ug()f i 1;i I Pent|u accsto rlouii, rnrrteliir,io va,r'iai;iel cu ternperaf,uril

rIF_ /

101 x
o//
IF_

'i03

=F-

102

C n-p ll,oi1go-t.lio1t.J1t2' .c-u ProdusLrl liA penlnr
.jonc!ittrrt' 7;-rt si cu
q Scholtky bat'irri Scirottkr'.

dro o o Pb Snte

r0 X Pb SnSe

o H9 CdTe

1d

I o-51 1?. 16 20
0

n3iT, K-1

;i irrr.stri efetrivc ertc de foltrrlr 'rt*{71:,l['k\0)8,,1T)1I,10),iarrnobilitrr,tel,

eltrctr'ouilor r-lr luat identicir, cu ir goliLrilul si s-a considerat ploporlionali
{'u ?1 2,6. Pr-'rr1 r'rr IIg('dTe s-irLr folisit ululillouele expresii ale timpului de

i'ia fiL r,:

) p:2 ': ^,(n,f '1i)2 a 2r,1r(n.ulrt)2,

urr(.le:.,;es1t'1iri:pul de r-iafri Auger intt'inricc [1+]. Se obselvii. cX produsul
J?l este nuri rrrru'e llenlr'u jorrctiirnilep-ri decit pentt'u di<ltlele Schottk-1. 1i,
de astirretrea, al'e vtlloat't'A cca rtrai n)aro pentt'u PbSnSe qi valoarea cea

rruti nricil penlrn IIgCclTe. iir tabeltt f.ir sirit pt'ezentate vakrrile cletectivi-
trilii t'rrlculute lxrnlr'u jorrc{iuni 2-ir ;i tliot1e Sr:hottky, la 77K, pcntrn lun-

3A

'FLTIJJCS cp JOIr.iO:1..jtr -E lr{Il.roJrun BJnFrs€ € nJ+ued el€rcods
-J11f] u sJtsrrldlllllttr ijp rnInJuJiJ{.iJoc e llJLrJ rriiltscoJd o?€nl ornqoJ? gsuq4€^€
-IIrIil i}lrnlslrJ] Jp €iurpurdr0 -'ti'I '5ljl -eporpo+oJ Eor€+carord nc JoI
€T '[gI]
/\ 'A nlclljs
uolpn.'rtlsuseacrlu(KgJ1n'1?ctn:..rrlnsFnr;cu'lpp,togarp.rooslqoo;
azt 0rz cgi op ss urnc aur,iticu'pql.eocqocJTSt aEsnurlIusuorJ]€orrpr
T.icrrril
runrsue+ er1 'a.re5und"g;r1s ap €aums
--uai1 '1 ri pluu,lsrro? o also lE- opun

R , ('-l -l)-j\r-:A;

,
"_f pcr.rrdua

rEcZ5€arJ1E'Kt. d'pnupro.gr€lescoqtp{e,r€opa.uron1rspu1.orn+dnEc

!ul-(u-r!er{ri1r{.$r/.1ooraa+cgsoJlorzcc-yullnszra)oo1ueut;a}*rddoouazxrJrl"a1pcJy,oa"zir.lslelrac':-inr.€aryrrJr.unsaoro1ltrollD+youiplcFaauoaopprdnlspa.oeorrrJFsl?luieoeopaJllJ'raiqoqluouoctgr+e'aad)srll/'oonai1ordaplrqr\nuo-rtDguosl''o1aEIrrI4l.;Jaro1tIcu,nn]a..oJcrrJulznoloDaercldirpanqoln,,n({,rr'K,JJrJordqr*1sluc'rlorKntqlaztopsr1lcduarua'pce.n]loalo"pscepuJrue'ra,o{lF.oerrrIo,uultldu.IIzirnls€rIe?rpnupzlolniTorourcJdTrrrart.lrJs}rarroI+\ccop2e?Jrcdz;1'oaRonvJlqsogfaturczovTarel.,prlrr^aJI]anr,rrte{td?€alnluaruoualeoautrrSc]5cnc

pSuulunu no apo1polod '8'{

o lso 'Frrra.{E'J ap Joi{,ro?K};rncl l: e,re,reira5 cp ' JasurJ+u{ }ra[.J(]+oJ In+?aJo
Inursru€aor"ru,1 ror+c€.rd raruq,loa
ucai-'rrosoprr:.os;}roOlrsqni?loJledInlroarnprnrr,curlrleoiloellslcocnlioporr{ulit1otaogolc]r+gi;uuiou?nTnJ{uur;e'rKrosriou?ucorrlicolsou:,uI,r-pr?rnt1sdcnuol{l}oeddiul'pq1ure,?}rrJJsalsaoxunpuloorr,cIllron0oapd']'ptprurlti1rul.tnr1;}1ltc1s'KlpounptiqrzBruucreunrgTria'o1coJct}|pooail,nrlp4arfaueJopFrla+ur?5sr1t,zoIunl"€-cnustq{tulirrunqatcrnr1pln-Era0zptrp€.palrlrcil{uaore?*pTpcTorlrurEIizlpoduezo-'epae-+u;l1orruuA3cJgg.
gr0l aF d dr1 ap Inl.i..r,ro:]qlrir u1 lo1rio1t1;rnd r:rfurluocuoc t3 u-r{. teunr{cuofl

I I'O rr0l ' I 't ,t orrr00I I''ll''€I 90'o OJ,P)3FI
n0l ''Zii''3f
,'o rr0l I'82 (t asusqd
8'6 rr0I'I'Z 6'r c,Lusqd
9q'o

'*4gjei$fjx-",-trl zrurlJ'l'U lr11/.7rz11Luc'*1i'l .ur:r15'l:U l"Ira:l!"r{
.J-d .iuuli)uol .1i{}}or{cS .rpoir(I

cpomolo; n.riuccl s*i3 !! *1J 'trU Inl cllJollr

9'I DlaqDJ

apnut"nrrltculoalloodqJt(s(r+e-rru;rricuenlara6pc1e€a: u?EI(+'([{AurnoaIuc'T0)fluco,truuuq:1Ea)gpw{Ftntu'{' n{Tt1Je'€ZJs+Tsa:pE\a"lr'o€Fl+ruJrc,or€d}pda1€;cprnIKd*peEui.nf1e€"a}rup'leuzeoecorudtroar;?8r

tea slrati:i,l[ a rnulripliczitii pur:Nir'torilor cltl szlrcinf, pe intreaga arie sensi-
bilil la racliatie a diodei. t\:[icroplasmele sint regiuni miei carc iau terrsiunea
ldiceast{er'aLprulinsgpeorzeitrirn.aLirlrunii.ciLSetlleeccilt;iarersntiurtlejorinacletrliolLrnfiii,rciieedaefceecteliuqriitecaoznSd,itaiimlepdiie-
pulitate riin t,iru1ru1plepali'i'ii poate conduce ia diode fi,r'5 regiuui rle nriclo-
plasmil. De asernerrezl, pot apale nenniforrnitili spaliale
ale coeficientului
de inultiplicare rlatoritit reornogitiitilol de dopaj
aie rnaterialului
ilji{eron,to:gin-tagaic.atteltli.uc,frln1eiq4iiilfrlaalne)ip-ls.€ititntoLcutalrrrlacouptigarileie,iipnuipanit:irt'dr:eir,inlitsierlposarorezdaap,ceiitreiiczvosiaetfioilrelieiuuaslpuirluiaiunnndctceaellrilie.iiocq'iicrlisrfuieuum,lzcfsopibe5ltou.,lusrUee.i slAneccccuacetlliotaictnisrzneltaiieilpafrmdljoeueacfnei,csrgsgieeaiennrsirtltltieeieitr
rlifrizie : o tlifuzie pertrn e {olnra inOelsulil'LdLectgnarirl,dianrlzer,tloipgi,rip' ;oi aoteclitlLiusietrplcetnutrr,.ua
a, forma
jolctiunen actir-il rr'p.
conrpleulent:rrir s1t'rr-an't,pnl'octc;ru,1n, rcu;1i1celisotcelarrSrclsroi,'iL'rtt1,i.ar-nctilucfilnecetladrrei
glaarldsdt,ra{ftigir.l
1.14 i,). Prirlul
I-uctalic, 2, esio un stillt seniitn'r,ns1,ltl'ctrf . L-tu roabe ci, inelul dcl gardi| con-
tluce la cre;telea telsiunii t1e -qii'iipunEele a structnrii. totu:ji ecesi:r
la crolt{rroa r-itezei de r.Lspulrs. cop-
ltrnce cllrlcitii!ii ;i 1a rricfor'&r'r,ft

Perrl,r'u iL r:lirrrina si atcitst ticirjuiLs -qe utilizcazil o strr.rctur5 invelsatil
rLumiti, si r-Lrr arlincirne. r'eprozi)Lrt;riir in figula, 1.14 c l1ill. Se lealizeazd, intii
epilaxial,iorrt'l irruea ?/pF aloi se
torrrrctzii pt'in ciif rrzic regiurrea p
;i conta,ctul rr+ carc este ingusi.
pSltnrucatjuursataolepatimgdrosseimriei aslizi bcaozn:-i
centlatiei t1e dopai ale regiunii

'a.0 alt[ rnetodir, deaevitarea-
tliizltrilneaaut1uansi tirni-cicl ttuLreiigaordaXs,tfceolndse-
C fonni, incit cimpul electlic, in
leginriea uncle jonctiunea p-.rz
zitinge suprafata, sf, fic rnai rnic
r.lecit in regiunea actir'* a r"letec-
iolului. O asemenea stluctur5.
rncsa-iiLclinatI, cai e sr. irr&i .rLu-
rne;te ;i structuri cLL suplafali
r'orrturatl este^ r'r'plezelrlali iu
f igru'a I.11 il. Iutii se folrnerzt"r
jorrcliunea 7)-' n, de exemplu,
Si-n de rezis-
plin rlifuzia Ga in
tivitate ilr.ale. Apoi strnctura se
taie la margirri astfel ca acestea
s5, fie inclinate sub un unghi de

6 + l-0". O a,lt'i stlucturX,, l'epre-
zentatS, in figula 1.14 e, este n+
,p ii p". Regiunezl n+ este con-
I
tacl ohuric ,si in acelagi timp
liig. 1.1i1- -- 'l'ipuli clc lolocliocle crr rr':rl:rrrsii
inei de garcld, pentru joncliunea
n-p, deoarece ea vioe in contact
si cu l'egiuilea ; slab clopat[. Gstrlr':ilstLirtnl icle1e;bi acroanjcdeinntrraelgiiiluenereagpiunsiil,orr-inl,d+,
qi
p se proiecteaziL astfel iucii
in
cortta,{rr; cu legiunea i: atruci cirLcl coeficienlul cle amplificare atinge va-

tt rr oss') - rl

uno-rOlrq+rodu?souogdlosrlpsu+rnurorcoJiJoltnrJrucroOopli+ounu8a€l(asIuulIEorucIcIus?oauInsuooJrIolooolpJsrgozuscrJrqaostdc+rtror.nIoorcdsItnsprcInJolonarulJl€soLro+i{ns:lr'1€tzsa.uIrc4l€ectsJoI+uptltlssErKrclfnnrp.?rsucuultnsoi.JlrrtuqtartSsudpI'glgEt.st'lcrSa"ttsrgeoI.o]Jr

ar,ierpe.r €I Irqrsuos u,-d-rc uvs d-u-rtr,ro+srzutsJ+ un olse In.ro+srzut?,rlolo.i1

InJolslzlrtsJlolod '6'I

'g'I €IoqE+ rrr a.iB+ui)za,rd luro- pr&riu1,e,re
n-oclooJpuorlproilonJrcrropus nrneploaiurrmnur{ra.ruoo;.IIondc'so.1lo1p€oplpuotploJ{4u1IqcolrqucsalsFa.ro1rn.r1eoqunroc37oloporp

(+ a) nor,wba -(3)

II--ntorsr.lrurur+arco,oIlonslo+oc,sB.oIot;?oIrn.rIral,otBrl1z.ludtriuro)1ouF1rnnzcluupr(rae€,or+ptptlswl.nrInsraJeo.urrctuaco,,aIlrnrd..trc€rIznttrizu.rotlocrr1taroI,r,rpniIr1c.ot'o?'8+IlroIc?t,Jr:anapc,IFrflrt,+i1iapro.l1srpcua+lul.plrrl1nurldclsan,rrouarx.rclrrnsiyarlaglicrtlios,cra7idip-a,prl;+otlrroluurrurrtrii

'[['r,ttrf,bl: (i,l )

erse,rd,xc qIts louro5z op rnlll]ua,rnc r elpcldr gcrryn:.r1ud c;,l'lsolsa n,tlrroc[
eparupirrrlciqeoFnrlozcs€n?igarao{i,lrl'lu[eelurfrluulr8"parou1rlocrp4Jsuor,'+roospop.rgnriolroilur8.lrtor.iti]'uf.r1o.nprnuodoa.relloapacollnercp€toyt-ooIr.J1rc1zunruuIrolrnoalpo1rilunirosiueFacgroa,rr;daonar
€rxoopll;lt,:rrioouuccoqa5i.lrdclnuolrltlraIln',lrJs€oncpal.oe'ra.€.r.rcrd)reug(cauIq1rdIcern.t1rrz1ernnstntuarorptopJpl+.'IcrIo.n,IltogltuJaiI,orpilurdic|cr{l:Inliep{.rorrlpuJal t}Flrot'ozpluoiEot,tmolareu{ziunilurrrlso5rarr?,narrilrruirrrirdl.lrieidlrcrl,Ecrrrrop.{rlourr,onrrloarrrll
rfq-pp*u1.,.orEronc1qtnrllnpyI1€oc.oilb.lzr,lorru:uicunr.,;+rlr]o1uladrruprcuop€r.rnlclrllunolspldonlu?ptursorelo;.rru..mn1cazr'rap€u,booruulJlceoraitp;lJiolouiilcoIlouiltllr3flr.-Ir'rrorrr,)-rp",or;i1rrnr'rerlrllullinuo1lrruni.1rooo.rrprorldroIJ,.nuiar.llrouli<+a).plrtnasoo,orp,iirrarral.rir.rd{1a'}as,FrapJi}

a-lpru?nll€l laiuprJiclrrorrlsro{palr,sruucaqludrrlper'lfu '[aSpf]Inrlinu+rrulalnrcl lololtoi;lr.lBrrrTr riiuprlxr€suu.or lBuer,rutlo11qtsl,rrTw'a.gie]rriri
or- rf,rnc ',u1saar: nc rBruII nit r* 1uo;ncoloJ rrlp !1,e.I+TII Eurc'Fpq.r nt .r1*o.ra

es ar{e.rn1es op 1nlca}g1 'o,recrlthllnui ap rnln+uorolJooc /r? r;rop 1i aunri:trrol

lIuJIaJut-Wnnn€ou1.Ips'rl]1ouzel€ncrp,nlorzJJrplrln.nrlrv,urno.lc?scBrssd{.rcuarrJraodoloucoaloncopgolroaorsltoJ;r,.C-orrsrnoos€dlBgnlspgon'cpulur*dtTrlrmpru1o'rIrrdLuuq)urpurrolotuecrccl,rxlrusn1ari€f€Jsuer€duur.orJa,Izdrrrc.onn+arnro+utuc.tlsclru;cieouoBrtnso,.lororrapirtdd;sKlaenlucamo.Jcplo:epln1teror;cou,lllIurrlnu€rolorppn1un.oIr4oiro1cor+n,olrlcacsnror'c'ura-pulJoapncoJcrDrprpgs1iuxSntuoo'Isaredpzo-.rnrrrlplt€ltnuapsrc1oloJtlelun,o3iruBrluaolpucuorr€.",lreurd.rarorro8Fcu.oiarqurgerpnccluni.i,nrcoruRariro.llrcecc,rupprntoplpoJoalsKz,?uJInrolanp,iotEcpaCl'uuupesuarra3ursciIl+r()'onla0ct'px.alrr.')AcxoJ(rJclcoeraon,c.oJe+rtporcri.osu)rr;courqca0,r1a[oB,ip(rrlrd,,zI;or,trrrl.lhfuu+1,)r.t-ei]cntisr',io)ftiit"r1,rarru{5rrumraa?aolocrtruro1,ippilfrtii{r

\ Ia tcrirr I 'l',tlttlu 1.ri
I)trlot'rrranirlt' itriotliodelol r:u avrrlaus:"r

'f ip

si(.I6) n'p (), l ti(r--120
pn (). 1500-2000
Si(:'lii1) n-p'p o.
si it(xi--,!;i
InAs l)t1
InSb 1(!
pn
( ir'\s Ir l-n ( l:t -\s i

6{}

lG-ittr,l cle cardi, .'l1I-nrcsa inclinrrt,

lGrtcrsfioi1,o1tt-'ir.(n)z,1is1'rlorlrpl{r'-lllt-r,tri cSsi.tr']liirr'r(rrllrlltetlz(olerlltif-ttlsli)trrtrlfsiglr)rot iriri (r lLt.ilrg('\-itloiu'ci1 L{)-'7s"

L l:r ir I senuiirllil sc
r..11|1rgt) p(r lezistrilta, (le s:u'ciD?i Il. qi diasrlarllii su rlri irttrzi rle clrctgit irr
figttt'rt l.l(i. In schenl:r elcclt'it'r-r, tiirL ligullr 1.1i clt'r1 r'(xlu] i)i]zci {'st('[?isi11
in gol iitl'sut'sa, de ltrusiuttt. sLr ('ol]ect(firz';i, inl,r'e ('olec1 ()r'si runil{)r'{'11 I)ohitr
pozil ir. lit colcctoi'. irr ircestc, con(li1 ii jontliuut'rr t',rlr','torl-i;:izi, este prilali'
riirecl sau
ztiac1iiI,reinpovlcirlts'iziirl1r,r'r.il.orPrclliinriuieluftrrerri]nliatolrc'-1s)ei,rzgi're, rere',sletoazu'i;,opr' tr1llto'rla'i,ii:'iz(.iire,(t'i1 r'on-gol irr [)r'ar-
l-eci-
t1;tiltea ioitctirrnii (iolector'-biizri (t'ie. J,.1{i). Elccii't;trii geilt,ra!i se llcpla-
seilz'i la ooleclol'iat. golulile gelle|ato se dopl?Is(lil,zii iri baz5;i inca,r'c[, [la,za.

cn sal'cir15/ pozit i\'5. Aceasttr este sirnilal cu o lloilii izirt'e dii'e{.'.td, a ionclirrnii
etrrilor-llazii si t'onrluce la, iniecl,ia electt'otiilor dirr eurit,ou iu bu,zii,. (lnt"sntul

h,

ferecslrd

+

a p n

++

R.

I.ig. 1.1 J- - l:'ototrutnzistolirl Ijii. 1.1(t. - lli:rgrarna rlc i:enzi clr rrrrrqir

rr iotol r:tirzistcrrrltri.

t.ie ittiet:1.ie lir r:rnilol dru'eazil ir1 it tinrli ci1 golulile g()rrerate in birzii t'r,"oolri-
baittrrlrtilifsicar:rrtd'eiftrirzlrlnfoztzoitriantrezmistiotot'ru' hI)rl'jilteisoinec,ticularr-;1i.1irertrcliitrozru'-lltatrzl5ru,.i Clcleficie;iiuI dt
cla1, tle I'apot'l ul
de 1r'anzit plirr foioconductor'.
rlinlre tiinlrul tle viatil ?r olect,ronilol'in bazd, 1i tirnpul lor'
baz'i'. L'oeticit't.r1ul de a,nrplificr:lr'e G (,ste (lil,1 rlo cxplesia

U:1 , c,J'r"i(6b.{l),

Jt,At

9t

l[-cnpuocrTuas I€lJaltsttr un-.rlulp p.r,udo.rd oD* .ru ri 91+ f lntuourop uI lunri
al,ulursuodso,r oJts r* n,(o.rer;ur uI .nal+dsraueJxoa+sorrquJi4 nJ
1n.rlourolog 'J"lo/oVrt:*olsa p rnl € Frlrsuos Jolcalop un
eo.reol,ur o
p;)1,]cr?ld

JI) II
ilpt
tr-eso{luoca({q.lsur'enzl,saqr.azr ouIJrrol?loccqrprrutr?un'J.ataol,sllcoInnp(l"nrrro,ol1ucsaors}?raro.Jrraaro,tnC.ru?nr'suuJIarns'1rXalrlrrearJudualtrmuxsaaql.lnrldn)FxcorIlrleuIorquoprrls$olutlu?woslsilotoJqlpna"z1B,o1ulaspu,Jrt

lnJofsntrrotr '0r'I

'(g'f '31+) )I 0lg 6 .r.r,uuor{cunp
IaonFpluotasleJ.utnneluJ,,rlauodIqS.ustaaaql,.ernnIoiol.IuFarJ+,orstrJoJ]cl(;\]),'rr1'rsJn!p.lrno.rliJott(sl[s.Irnuzn,ueIlrrr:r.)lro+:]ranlloilr)r'rB{t.t{t.3tp-trIi-r€youa.r..ertcuclunursuI tan(p'l"l/,)'u3[7of],]0:€'1)7rurenzuoneq;l
optji) oe.r.tr?nl)8rrrruurur ron+l €tsluooltz3elllsdrat.lur rilri]r}lrs'.oroolrqz.rrrnB)J+raoJ?eoJrorrJntrrr+nsroJIotsloJtsoJlcccoloIncJiloillp{r{a?l.lIo€rdl
'11'1

'?z,uct-.ro+Ja1oD tautiliiluof ruurnu ea^a ,rB r?]saoE

.[t] i).r,1?f) rrJgulurnp I'E.ro+t?p Ur']rrornc olsa tr A
,.:-D'IJalcE.rt?C .ro]srzu,e.t+

urld o$rtro Y;" opun
't?.)up

fj

..<I .{):.rI

'urso.rdxa op lup aisa .lolrzuu.i,1 u1.rtl
I'[n9lI1r]aJ.rnoClru'0e0rfe€uanJr€soolel au.Ia5JouTrl'rulzna1Jelpod'o,-p1 TJ laJh't p 4'oT qI*ieerol <'o pr.r;rua8ul

qrultu.ri)]ap al-sr op ,ro11ndrm1 r{

A' "A

rn 'rlu,rp[JuI rlurtr:nl rl ir]l
-rsualu! rlR rJolE.\ osla,rrlt n.rluorl
a JrOpISIaZlUrrEllJsIorrlOalJc€rnruL)rn--c[.1L)I'JlO?c.Fal!o.,iI]
a

]-

i

i

I

)+

I

'r,l

,r.rz'uct ul fmqluocal nu og.rnlos o.ltsJ rrI aprfrpuoc u.r ,Hrq,Bltsrt c,1*o irl,1n1.r.r g1s
-e-,a_,E1a' Dttve'rzcaz\eq uourrto.r5 p J-r?IqJoo'rltnll1rno.rou1r1luorlor.rtn?laolFrlruara+rcznnJprupoaJpirulsirour'ioFuonpl u-n

"olBlrrlJflilnpuoc

l.ol sinterizilt, t,rilr('esto cornpus rlin tixizi tle ttritngatt, cobalt;i rrichei l:J2],
sub form5, de ba,r{,, d.istr, sfer5,, sond-i ettr. I)onteniul de lempet'atr-ll'ir in
cat'e poate fi lolosit depinde de lezrstenfir sa B (trlbela 1.7).
Deoalrrce va,rirllia tempclirturii mecliului anlbiant rnodifici, r'ezislLlntit
1r'r'mi.qtonrlui, lrentlu o rni:ri colertri miisuliitoirlt' sc utilizeazX' tloi tclnris-
tori iclt'ntici, t'onet:t:i(i in punte, dintler
c?ll'e nulllai pe rrilul cilde l'a,(liiii ill tlt,
7'abela 1.7

ilezistenIa tcrmistoru]ui la 211 '(l si rniisrua,t (In cazrrl in ca,r'e st-r tnfsoit,r",lt' o
dottteniui t.lc ternpcra turii in calc tempelatnrii, rnlrntr,i umri tlitt tci'itii.t,ot'i
poatc fi utilizat este intlodus in irrcinla. a t'ii,rci l,errrprla-

tuli, dorittr i.-o nril,ririli"[nr). Un triit'ui1 tlr
nrXsrutl iu purrle t'sie r'eplez('n1lli iti
figuril 1.1.R, utrcL, lt.irttislct'tt] 1', t'slr-' tlt'
referinlI iut' ?, cstt' t'r'l pe tre'rt' r'ild('
-110500FF-llaa 150F
3OO| radiafia.'IensiLrtre:t l',, csle lrt'opur'lio-
nalS cu tlifcrenl:r tic tt'm1lt'r'rr,turt-t. [ni-
30OI. la 600I.-
t!oiarIuslue ia1juius,tcr-lzirtloi,rt1lel'ain zi(r'rrl'tr')r'rlir.rri:utliiull-trt.rz\-isi--
teza, de rS,spuns este determinatl de tinrpul in c'at't tt't'tttisttirrii lcir,'iut lii,
ternperaturi.u mediului arnbiant dupl indepiir'1 a,r'e:r i'ircliatiei itrcidetttt'"
Cildula din termistol este disipatir, (inciepiir'1rrtil) prinlarlia,tic or'
prin conductie termic5, prin substt'ilt sau prin firele de lcg5,turti,. irr gt'nr,rirl,
disiparea c5idurii se face plin suhstrat ;i in ac(fst caz timpul dc t[,spnl::
este controla,t de cl,tre raportul c1intre capacitatca t'alolicit ri, tennisltnrhri
si cond.nctan.t:r, t'ermit'5, dintre lelmistor ;i subslr'rt1.

1.11. Detectoml piroeleet,ric

Detectorul piroelectrio are performilnle toalte bune la, t.onlpelil,t'ut'ir,
carnerei in ceea ce prive\qte sonsibilitatea ryi r*spunsul ltr, ft'ecvenLi. Ilateria-
lcle piroelectrice prezintS, pola'r'iza,r'c electric5 spontan5, care se prrric irr
eviclen{,5, prin aparilia unei tensiuni intre cloi electrozi a,la;a!i rler o palle
qi de alta a probei. I-,a ternperaturd constantii salcina clin intet'icir' oste rreu-
tlalizatd, de c5,tre sarciina, de la, suprafatS,, rlstfel cd nu se pttlt,te dr:l,c.rtrr
o tensiune. Acezrsti, salcinX, de Ja, snpllfatii
este lelatir- stabil5,, astfel r:ri d:r,ci se mod.i-
ty ficX putin tempera,tura, plobei se rnocliiici'l
tlistribulia sat'cinii din interiol rii rleti se
{
riroclificir, salcirra d,e la suprafa!^ri si se puale
tletecta o tensiline. lTn dctector piroekctrirr
este uu capacilol fonnat dintl-un ma,trrria,l
feroelectric sensibil Ll tempeltr,tur'5, cale tlle
clr-ri electrozi atasali pe dou5 fele opuse.
DacL pe detecrtor' <.ade o ratlia{ie rnoclutratti
atunci apale o vru'iatie :llteln:rtivii, -\ f .L
tempelaturii aeestuia 1i t; sa,r'cini alternrrtivi.

A0 : p,4 L.7,

1.11(1'.u- Oircuit de nrlsurii unde p este coeficientul piroeleclrie ,!i l-itid-i-
Icrniistori. aria cletectorului prin c:r,re se a,bsoir,rbe
a!ia. Curentul dat detector este proportirtnrin

36

,Q

tlrtro,r*1a;rean1aqoa,u'd(nIlIl1,rioolcpalltaslpr:+ruiltsc])Jntoeztqnr+tnl ((gur;rq.8r,r1 ap legns) SOtr : i96l rugrra

arI.r?cal?)o,I?)J alol'BIJat'urr{ .],I}tirO

. oeey)c6ll sl
Vdt^

anr{ryr os yioes : PC FJ o.rleol,r3a ur pura,u Ii lru(l.sczi'rO{rcr*.r2iyu.r.atpuauFn

{iI'}r}In.ro}rir}ap'Ra1utrrtudq?r r* plualulrqaa e,fuolsrz;r.r

*zn(?,c ?.{ zct r) : J1.

'tf "!'

O ISO ,Io]Co}Op ad glts,rrrs,Fr{r "c uaunrsr[4,1

?*utltt":'1

?r) IaJls't? r1(.:,or lt,raua;t- u1

glo :1 apun

-, --Lr93?:o:4-JylL7eJ\il- - ,, l(, A(D[-rg :: tl-'rr!

! ' or7 lt.
1,oti)

.ruriqo os sns I'Rur ap tr{.,u1al urlJ
.-tlillarpl}e-alruISct*rrdaitu',rrrore51;1ulasn1.lal p-'DoId7,rt,(l:.ruur1i?,ui)1riausrpuJau;]pn+
t-1{;.rrnp! rpr;or1;rr,-racglr 'rnlrr.ro+Dolop rrJ{r

-rlmplgJ a (.ro1,n,rn[uoau1

(Inln,ro}Jo1op 'u fJI,IoIl3;l

:'ro,ro 0.1 U" ,LV P : ti(lJ''v)tr f'

ap l)ilr'I)1? ppr'iua.ra;rp Erriplraa urp a1iasg,"l as tlrn1'u.radrual

'lr'l1u'lr'u''l as u1p 1s

'1'|a

;;::"'.;:::,;:;;'"*"',

3LZlc,

'titiuo-r.,ra,r1 r1,l'1?l,uJlrp()ur iJS.) d- []UrpB.r ta,ra,1nd vJtlff 'g'.r.:1.1 al]s? In,ro+
-;)a,lep n.) ar.ros trl flvlJorrol 21 niuclsrzar o ed ,BJIoAzap os o.) ,l udrrnrs-riaI Jtlr

. _?I) __. T_d :.1
(,t v)lr

IlJnlt?,radura1 r ar{errua a[] EJEI no

igerrn:r,lrat d,e pturnb), I'Lzl' itituniLt zirt'otta't cle plttrnb tlttpilt cu i:rnfha'n)'
zirtionirf rle plnLnb).
trl, (tifarr:lt ['\'F: (diflolm'a dr polir-inil) ;i NiI]r
l-roraxa't. Caracl,elisticiltr i.rcestor mlteriilit,: sirit pl'ezellt'a,te in tabela 1-8'
nnd.e E este permibivitatea relit,t,irX ;i tg D cste tangenta de pieltleri dieiec-
trice. Pgtorca ephivalgntil c1e zgomot linril,rlt[ cltr flttctua{iile de bemperaturd,

t sfc

P"(I?) : (l lr;) ('Ll; Tz G\ttt,

'f ttbela .1.6 QtJ rni
CaracLtrristirili' rnatcrialelot' piroclectrict-'
0,6
"l
0,l4
1'GS :J,5.10-8 30 5.10-:t 4.10*8
Li'faO3 2, 3 . 10*8 o,4
Pb"[icno, t 4i 10-4 l 9.10-t
I>l,r.T 2.:10-8 1
6lr 10'.:t l-r,5.10 $
PZ'T 1.10-t 14$ 5. l0-3 2,3.10-8 1,5
:J ,5. 10-8 1,3
PVtrs 2l';0 10-3 1,6.10-6 () ,25
8. 10 -e
NiBr l:oraxat Itl tro-:r 1,8.10-s
1 ,4 . 10-d
10 :10 :r 9,9.10-E

iriltrr{1I1tr1lte't'trr'1sperct'hiiavidcntir, de zgollI()1 limititti, cl.e zgoutotul Johttrittn est+;
P"lJ"') : t'li'iP) tlsl;TGt: eoo tgEl.lr!'

{-ielc nLa;i }-11111qr perfognr1l!1 1t. :tn detectolii lr0ntrtt fiilre rirpotLi}l

;i:i,,,-q(.t,,t 1=#*'- 1"'

inre la,loarelr uliuimfi,, (ieea ce sc o]l{,ititl cilttl

@ : p{, u ls 8l-t/'

itl'e lrtlloil,rea maxitnii. \irtlorilu ?t,L1tllit,ot' rni,rirni pentlu cliVerSe materi&le
slritnrntJJrtrreezbennXienl6trra,inpitealdbe.elarile1.8c.liAelpeacrterieeevistilie, fniet c[ pentru a obfine performan{e
cit rnai mici. ln fig. 1.19 s* re-

prezintli gornpar;tiv detectivit,a,tea in funclie rle lungimea de undil a eletec-
iilonrmdriek:pir1rr,,:rin1adrieeqnlfertiavl racolelqo. urlui.innSgrenimotnbessa:etr(lvezlr,uc)n:1-di;r.(5lbe, )t[e22c4;t.o](.tcu)Al 1rpi0iirl;eo(ce1tlle)ect6le,r;cict(oear)irle6o;rd(cmft)cl4sctuiivr(giata)lit2ea0a'u;
(h) 10r (i) 10; (j) 3 ; (k) ? ; (1) ? ; (rn) 20. ITltirnii patru cletectori reprez{'n-
i*1i iri fignrt tunc.tioneaz[ la' ternperatrra' c:r'melei'

t(r

6t

'(1)16i) qgqe '22 ''sFtJ,1 '1tld1.'1' 'afiuluI:I 'tI '.J 'f;I
!'pi)rn.r.lrrI'.r1.)r.{ .{I
'(gU.Of) tt'8I''sirl.i
'(6a6I) gl c 1;1 .'s.{r;rl.l pilJlr.rJrrJ ,u1sr:fi1: .,\ 'Bllt.rlrqq .11 !clclitl) .c It
"(ttstit) i:t; t '0; "s.(il,l 'p;l.rtl.rirrI 'r-ys^o.rlor(T '["rrJrzl)r]rr) '11 ',rozrr;'y '11

'(6a01) fil'g 'liI "s.\rr(l 'p3.rrr.rJUl 'r][s.\or]ol(l '{' 'rlrs.t.rcl '.[_ 'snlt:t) 'ti {
'(11iiI) leI';1 "s.tt1,1 l).r.ltl.lJtll rstlolttltllq \:'ollr.l.I()€i tt's'llotIr\i'\: 'ti
t\
'Ol0[ 'lls.r.rll)ntT 'll].rolcop .ll) lrzJJ. 'rrBt(rl{)(i .\ 's
'1ft;1 'Ss,,.r,i Jrlllipil.)\- 'zl 'J{).\ 'sll:lJrurtuJS l)ur?.loltllpuoillu.)s ur '17 'r^JoP)t}p 1t.t.iD.t.jLt1 + * * .:
'olti1 'lll)l l JJllrr.).r(l 'slLr]1rr).D1s)))Lrr ptit) lrotp:t.t,.)1.)t)Jt)t[') )r'to.\ 'lrlz JJI) ur].\ '\i .,.1
'{i,til'rli.uil)DFJ n.rlulrsJ,r.\ru.} -,)/)r/os tl.ruls tr,)Iuoil:)r/:1 'rluJolo(J'.\ '!

'f.i/(;i rliJ.rn)nfl 'r.)rlir.)l)ur\' lrpr{ 'lrlos tl.to.t tLt tolaatlt:otlstp /);).1:1..i 'rr,'Jo[{){l -.\ 'I

'1,16l 'Srr{ r'),\
-.r.rr'rrl.icl\ '61 'l{},\ sJrs^(11(l irrtldtll' rrt s:rtd0,1. l|sJol)tl)D pa.tt;L.ltr y Tttrn 1n.n yl11 'JsnJ\[ ']\ '([

'1311;1 'fir:1.r.r_1-.rrn-rriidS 'uollDIlDt.t 1t;t.tDt.ltu Ttttn lntylo.lo u0t7tt1a6J'rro?r-n-lrr)t 'il lI ('

't:t6 I
'tuBr{liJfi "JtiI isll{l{l rlJJ).t\. 'i'.tol)]l)p tllfitttltrtttttt .r)l)urtll]|l4l-l),).1r).r/t/J 'slttl,'J\,' 'Ll ':jl 'I

gIdYlrS()I'rgr€I

rt.r1u,,tt rrtq:11rri.,).']Jr) B;i:]ll.1l'i,.1;"'1,)1",'i,'',,r,,"u.,1i 'rj1r 'n-1..1

.r.l'y

CCC aci

"r"r@l

stJlaiacJii

Ltl;94'1"11nv3a'"-

,rol tr-

{

zto i

at n3 nJJauolog la) ePt

tt) ! t

.I

.

I l. \1. Iiinclr. \i. lllarr.. .\,. Siirrrons. .1, .\.irpi. l'hvs.. {1. 1(il1) iiil;;ii
1;. j... ll..Lrlrr:son. IIll:l: frarrs. Illcctlon [)r'iicrs. l'J, ri(19{):-r).
lri. l) i). Iicrtttrilr. It.li.O. Rlicrr. IFll[.J. lirs. I)L'r., 10.21:i {i{){;1i).
1;. \..\. Iross. S. .\. 1\'arri. .I..\ppJ . I'!rls..4Z. t-28 (11)?:l).
1ri. i 1. \Ielclriof. \\r. 'f. Llnch. llliill'l'rans. I'llrctron I):r'it:rs, ItI)-l3. 8:1) 111)i;i;)
'1 {'. Il. D. Iloct''Lsch.. IllllilTrzins. l:lccIt'on l).:r'icts, ItD.13. {)iJ; (1{l{;li).
:lO. i). il. Scilr. i,. \\r. ,\lrlicrlrl.r). Plto[otlt:lr.:clors Ior llte 0,1lo 6nL spt(lt{tl t,',1iotr itt tdilrr..tt;r:; iie

rl:':Irortits ttu,l cieclrott p,,rrlsi.s. rrl. :]tr -\r:rrclerrrii' l)r'tss, i1)711.
11. I [)ii1a. I. l,icca. I:ttrontettt iotot:!trlrite itt tcrtiirttrLtitrtloti si uitli.ttltr. ].rlit. .\rrr rlrnt i,:i,

IJucurcsii. 1 9110.
'::. L. \I. \\'orr;isrr'..I. Opt. Sr;c. -\ill..,l:J. 1; (1ili-):l).
):1. l-. il. l)Lrtltr'. Infralr.rl Phrs..:]0, i.l!l (1{)80).
:1. \1 lr. liir:r;r:il l. I:iir I rtlrtitcLi 'l'etlttrillttts. i'iolr I-irrriilll. i ;11;111,11. {!lil.

40

T?

f.urnTrur ersrrrrn-iluJJ op a,rap,rald o n-Ll cJ'IlJ {.n:nc urp ,IoleJqIJ €o,rt?cr"rqtsJ ug csa.r5
-ord 1uzq,i:a.r rlts-s a.;rldo Jolo.rqrJ rr5olouqol olSau,rcl aJ uaJJ nJ 'TriualJadxo

r* euool o.rlul a"r,e"r€druor o ap rqJoa atruod is Jolalulnr,r;r rrralSa.ro I!+pllIUJ
InIoJluot rrr aluola;t alosa,rFo.rd o.rapaa rrl pu1ly 'rn1n*trgrzodsrp rrcrzrJ u a"ra?

-"&torrn; o gclnp :)|iap aae] a1'u od aD. nrr oJ ro,,l,l (;r.t3o1ouqo1 aJapal op laund urp
JJ(arlnqarrrltgllnutlpoJoa"';r)ldd)o.or.qrr?rrrJSrnlng,rqtse,eioliae]sa.rrrploc"a6rddgs.ranirSi;r,?r1.sr1d,tourKantlq'r]otu?,lo4,rrs?IaJulcB+rjruEfrlzpQrrlsr+1uIu.i)€r-a,l.Jul)a.gi;RseI1llrudp,norrul ltr,pzo1opud1slu;zrupa"r?eurF1c
gqlrijeuon..r1agdito?1r,rula,'r;rrrruler ulsirolri,l r amolqoJd olaJ'€o]furJn oaIozJJ cs ornqa,rg
gcge 'Es a.r,Bo]tuprroar{rros nD rr.r?n-,u[ En- n"r+iroaf pF.ru1

q?r

'1uoza,rd rrg

pugd glruqddptir olsJ nu irfur.rac o?-qJ,')E urp eunr.)rN 'alualsrxa Jolaa o,r,Bor.r

r-r"atrldr,ennoslon1lauarou,nr?arlulJrrr{FaaSrd1u(+a1u,rarciroDcyrrJtrnnupsruoJorrJ.rgr,EusraIanrso,.}nsaoJOiT;r.eroacpsetolr,a{rrcppuuRoorn{aoauqnn.lrtJdo)al,pBaunlrznon1d.uu-rfrsre;o;,1il1'ofdu2u,1tos]allannrEurSrl
-rgur.ropr{..t;lr1d,u u,rert ur c.mo icnpuoJruras nr JoIrJos€I ,e a.rtole{ruro.rd er{uc

'[gf] I,ta-t't-Xrau,€qoltcJn.rrldISoailarugitJBiup;.acrar'rreulpssruuououpar.Ifror"dooc.orJrro,nuudr;a.nUo?"rr,JIsaIauJroc,fFrqJrlroSo,ru+rr,urItlr,sro3uqr;p,u.Jrrrpass"otorsrlpoEil?uarr-dolrrosrdarDudrrarrs\arrlul'Jrrralrlo,nioD,BLI]ut1rpr.sa+Jrn;Brupgad1rJoosoa.o(rJE;qJorrr1{aIncr"pup{rprr.oo,lmEoldJlpoJrocu"u]urruaEutnJr,zrrrn,oqzu€rlIgnopduwo'dl1oEcJl,n'JuqJiloS1ooruu-J1eo€fraIy?r'-pl$uoryAo,1,r:r1gpolscs"]lou€uilunlnsOnc,dyelfnau,,l'eupeugIou,rgealtsriuoeu-lftsD]vc+(nrr-ao,lu(;sru1)olprvsco.]u,€alirasoponaC;la.ourn1IlpopJn6onc.o.,r1drrrtroaspnrr-Jlpo1)sdua?ousrrgocunctsJtq€cpusI
un.tn---rr€raJ:or..lr.:.t;lorrlne,.lomuIr1r.nyczqrt+n"drlurlttetrrasnlruofodopJc,crugrdure.oasuoIsDoc+rfnr.uBlradsndaJBooa.cI.r1rsrt-rdtlnrsou.arnrgc.d+nsru,oaseu1rros"a+[plrJe7edupI.]tnaotl?e?co't.SIdrrrlsfqaocuno]eg.luJorpuudorfen+Errolreist,Jc{psirctau1lruue.nan1rnoll.pf;sr[urrIoar?i1ftlussaugo,rrg,t1d,+z-,q+u\osJr\u"aiotqol-az.{;olr].rnluyccrrrrnlarrlrs)'rnr+Eira(-r(slronp{,fourlouuJouarJulu.€Erri(?rarlttur?uf?r,aJ1oJoi;lo'gt;€etar)Boz,jzpir.zf]rnrIurlaa'll(rIters?l.Of,nr,gora,rB,flaOrqi1,ldo-ryn,fl]gunu;-f)rer1a'nr*l1+9[pu1.[rur6tga'os1uo"TIF]Lr]Jol.vrrrr.ufrIqazriI;rroolsuseaor€pto1cussI
aIq---Ioor;Briczr1If?uuutIrl;otc)o,slulpliq"uiuumoo1n'1sVppu'nLu,p1.ur0ar{ar10oddlnstDfau1oap1gnJq1u..sorrrutcpsocniralllKoK.nrop.+uerpcuo,oranaolu.cr?nnrorpdrpsp,nruono-eo.drrs5rauortzrsr.rurrrrord,lrroJ'5Ile+ssguloo]rn,dJnr.l+trDesKap1zD1urlrn.-l1re,do'terplsa?u.tgusrouKItrir1nS"i{tigcIorSrnuiuJcsronquurrrnoesnrgrfi,,roindserdicry'up€['oue1a6,rn,gjcrrrcfauu.rzpsn{et(rtps6?qqloa9rslztr6effl-,1dgrunp,rr1[upunfeun]1

alu.rouoli ggie.raplsuo;1'1'6

gu\roJ,Sn(INocrngs rlc rugsYT

a Ir IorI du J

..,i q{1vr1rr'i'sit r}lilrirlrii itt rLrrrietriul i1t'ltrgirrte t[e rrrufi 1ll,ijni+1ir.r(,ei s1l,-rrttno. rDnttuair{rrc1c1ltr"
.:itii <'r.t'i'otit,t,{l ilrlolls sttt'sr^lt'si rlet:r'r'tolii tltr lrtinini
lrtngiini ck' rinrli .

2.:). Ellrisirr slilrrrrlatir. Iifer.lrrl laser

('ottsitlt-'nirn tlottii trir-elt'tle cttct'gie E, si E" ll),u'l,irLill{1 rrnui it,totn srlu
iru)l(){'ttl(r cir'l't's('aflit itt inl et'rtl'{ic ('Il iln {'il}ip tlr latliu{ie ai urrui (r{rll, nc.gr.tr
:tfl:tl Iil 1t:tttpet'irtrit'il 7'('itrt':1.t'e delsilaleu clt, 1'otorri rlrrtiL de for.urrrlil lrri

I '1lr nt'l< r;/z v I

c( t\ '- t (2.ilr

,.1 ,,lvl/ * i

sutiitllp(ltpeil'rr(.,i('Lr1,lcsesalrrt?ler-.-'ig1tet.rzt-titlll'rllr'tlittr'trenzii\(titta'ilirp2iuil-t-rrl.iIL'it'ell.s1tfrl)i't.'tirrI,rruilztprifoir:(irut)prsuodalttrrtirtl:ncrcvzociluiilt.r'lstlioLll(:r,rr]c')(mcr li(stl(ia:I[rirau,,2r1'icr-rs2lai'
tlorr:i se lll) folon tlt' errcrgit ht .= [1]),(r-ttirt/o1l.uiIlltl,tp,:tr.,ntlirr
1r'ir,uzili{r l}ltsoiLll)ei lritnzi{,it tt tl(f
e,lrrctt'tlttilot'
_6 vclul 2 (fiu. 2.1 rr) osif(] rliti, rltr (rxprcsiir,
'rt^.i A
Ilt2 .- /i,, p( v), (2.2)

i iiit' t'llta de tt'uttzitic tlc ptr nivelu[ 2 ptr nivc-

I Irrl I (fie. 2.1 D), r)st('tlil,ti"r,, coufonn I.coriei
lrri l'litrsleiit. t[t' r'x1lt'r'*i:r
E7
i't,=BlP('')':' I (2.3)
o

i,ig. l.i. 'l'r:inziliilr tlcctro-
rurririi inlrt' tloiri. ttirtlc tlr. ('ncrl-ir.

llidr ;. lrstc titttptrl dtr t'irln'r'iislniczi{spiito,'2lIl-it-lIliisciitltlt'l1it3l,e,r;fai t/,itrt tsspittltllt'fittrttissttlrt't(trsoll,lsittnlluntk,(ltl

t:e lr.t'ilrritr dtrl,elnrinat,c.
$ul),l(.tirut(ra, rrirnllrlrri rlt'r'urliit,trit'). Notit'rit {'it ,lr }ji tt, rttttrtiilitl tlc clocl,rttiti
zr{iefir1rreirrr,tcrleelcrk<ntroiittiui,irs-ecnlrsu1t'i;i1, tr'c'tb'supitt''ts'tiit,'.liJt'. Lit ct'ltilibrn tlc
f,r.'l'tnit'rit1.()lc t,ratr-
t'glrle

nrR.ro =: n" Il."r. (:1.4)

Il,tLPtrr{ ttn

:1n.,f 'n1\ (gr1.r7r)trrP I - (rl: Etiilil'1,

lri(ft) Ih 6i g, sint t1i:gcnt,rd,r'il1r celtn't.lt.rrti rtivcle. l)ilt r:t'ttilfiiLt {2.2) --

(2.-lt) se otrtintr
u., I
..
!/ a - l.-tattRl

l;-p(v) ..= 9t. Ts (2.]-t )
B ,r(11 ,l 1y ,)t:- t"'! k't

],'r\urir.:ei rrsiiil:,afitt':I:)*"lg-r't1li)i ,c.u= llv. Iru, t*hilibru |ernri(l p(v) da,l do r:ela1:ia (2.5) tlt:-

c()l tla,t, cir.: r'elatia (2.i). fiezultr'1,

fr* : 'Br, (grlgi,

-lB1.o=1-{c'rl3:o {2.{;i

42

€F

-,(ipl.@l!' -_ rl (a)"C (.,,\ * g)"!(nrt- fl).d tt - ,O

ols.) Jolrtrolo; r olicl.rosqu op tu'trn"r .Soltur potu ul

'ep[(r.q - U)'!'* rl (nrt - E)'d(n)'Ag)'d !t : "*

alnF.ioua

a1eo1 ad pttSlSolur i)uli([o r)r. Jts-nlrr Jp plulol u,1t21 'm]ualra op.arlaadso.r

c(f*,i1tfr*)1'IO'la)(agld(f)i^s"nod{p,r'-nr'SaorUciicr)rn50'pld1au)'nEo(o1,r'rzicuupooeptr1l.erug/replsnouoouppp(l€Bi)upaIurillpE,)Elrr(3sr[rrururoJo1po.prllr.lruuaoolllsra.drl(nn)aaca{1YooaIalSe'urr(lngro.-rrr)n'r,d?in]ro-c.rplporu.lrpsnls.oqm(p()rl.ore1Jplo1r?s-rBuljE?LarcsYprur.crtrp4-i

al')ulp lnsnpo,rcl n,t ep5a oJsa DrsrrrrJ ,Jp rtr,l?U ''rr1 arS.raua op uo]oJ ap als

[-)IpIua€pnttc€qocu"Jlpot{ta'r.fi)urrsc.tlaauaapap'Brp.rrEr,ul.(s[ uur!p,^ro{ l[-ro.gr]!)oor8lo.raru?orirozpu€rJJfJ}s.rnuglu.ooJr{..ccnnppuuooci)
q {rl(llrortuno.trcsa,grrtl?Inorolsaxlzao.rrrarulmrlclllgz,.nun1alcdlquFrur.oroxqualrtJFaa1.prsp..lrczeari1lrs,ruaaa.lru'grc'lruelpopcu,ulnposu('Bga"rq{.:rutpl r(dr".o.1g1do.1ro8rpula,r,uaugarsIan,rpIaolrAuulrbu.lnn,By,tl

l.' (r.,):t0 ---./, t:I '(q))10 < ir.1p- r,]rsrJ.\ur lllzu.l u!
llulndoc[

r,rl:ls al) eJ.lt'JrsrrJl) r1l ari:rrrrt.J rrj ur;-.r;rr.;1 -'Z'Z'"*!.,t

2qo -&(tiu (3) u

Cat-/

-7

I

2-
l

!3,

tttuzrrlctsl ar.ur_o';Er'-lcsaola.rtlsraorFr[+,(uAd'tar,ro'.3oU}s) J"rJol]i)Jnnpputoro;lJmaropsurprnrr,lLlglrc..rat]lplursi-nrrcolio) rlTSop.T,rcJrr?sJua€anrrlrt
e,r'rzatplchuu op olamnu 'pl,ruocl saco.rd ]soJy 'rrroi]srs ulp-r.]trr aJRo ruo]oJ cp

I1otlrllntsll-gt.JrIt'JJura.uliullulJ"'tolgnlItItcut-zoaa:r].'ofrgetJl.re:eltrlidlquu.rnr)oorJl-s),nIrHrr1r;"'rer'arl,tltrli'rpiuttldtoptalar-ts.tprtrt"Cl'{rtlrpslsE,pdtl',l4rr,ug?drrlcrrlm.nrrolnrlrAlurf.,nrs^rr{er,rnrt]y-rprusru.ar.3ulzl"t.rrrlao.rnudluirr.u"errit)ltr?i)ls.'.r-rrusrro,ri1€.r}FaolgurJtaaloruo,crfpa1l snza'6rnpi-l
{a,'mgaltuz,fttuu?,polluraDorowxdeas,rr.;u*)rprso*en.lrlouuoaoa,r,apprulEtsllrraJltr'r,n.rIr"u(rT)tluIa€rgI'.Bnr€LgoJuir'!-l.ra]Lunr,r-orilrJlIporSu'gr(usrror1ru;,rrlolnogpJ"1deururlzouc*ul1ooarr.lc.t)rrsca[apur,irhiazuln-$ro;to1uo,nrr*'s1rr]dotopru,urrlr,truul,1npo"3uuu]urolrdolr.?orlqlascilalnuoesopnolu$l.\rro,raa-rfu{siooaBaff.rrororppsl

U;z) '(^)i "r, "r. ly:lg tuttslr6.r;)

-;, -

u3sa.rdx.r ap.Fltsp ah-J ,ul,ElnurrJ.s arsrurJ ap ar,irzuu,rl ap t1,el rf

Const:lnta de proporlionalit,aie in acei lterarnlozuilii'erie(ialfl)ii este acecaqi qi

conline pit,tratul elementulni de matrict'

13 : (lnq2hvf ntzh2cg))(rli) l2 . vol,

r,Urtle [, este indicele de refraclie al semicond.uctonrlui ,si ,,r'o['r este vrllu-
rnul serniconductorului. Pentru amplificare,a radialiei este necesar ca P.n)Ilo
qi rlin reialiile de mai sus rezult5,

tr'n-It-,>hv, (2.8)

rlnde ilu este cr.asinivelul Ferrni din bantla de conduc{ic tsi ?, este cvasi.ni-
velul Fermi din banda d"e valen!,i. I)aci mr e-xistd, reguli de selectie, inte-
grait')r'peste banda clc. conduclie qi peste banda tle valenf5,, in rela{,iile cle

rn&i sus, se pot face indepentlent gi se gflserste penl,ru rata totalS, de ernisie

expresia :I?," 3t r,,

(2.e)

srucrl(nicico'rrn.c;liucptosli,inptricnonrecceonmtrbainlizillercaeleelcetclotrnoinloilor r[ic,uregsopluercilteir',argeolluorciloemr.isiina
r1e nlrliir,fie. Densita,t;ea fotonikrr ernili creqte cu creqterea ratei de recombi-
niLle. Cre,terea densitiit,ii fotonilor duce la crqterea ra,tei de recornbinare,
q.a.nl.tl. Fotonii rleo anulriti, encrgie stimuleaz[ ernisia fotonilor de aceearyi
cnelgir'. Ilaci, t-:xistti o anumiti, distribulic (tlupd frt'cvenld,) a spectrului
de rtr,dirr,!,ie (care poal.e fi numai spectrul de radialie spontii,nil,), in acord cu
spectrul se ingusteazi in jurul
aeie de rnai su.s, datoriti, emisiei stinulate
frecvenlci maximului distribuliei radiafiei (pentru cX, la aceast'fr, frecvenld,
numi:lrul fotonilor initiali ester rnai rnare). Creqterea rnaxirnului distribuliei
radiatiei ernise se nurneqte ciqtig sau arnplificare. Dacri aceastd creqtere
este snpraliniarl cu excitarea', proce'sul se nume$Le supram,diant. Tn cazuL
suprarndianlei, cleqi spectrul st' ingusteazri, radiatria rS,mine incoerentd,
tleo:r,r'r'ce se rr,mplific:i nruniirul tle fotcrni de toate fazele. Penlru a
sarisfiicute urnt6toarele condi{,ii se obf,ine
ofectul laser este necesar sil, fie
: (1) ciry-
tigni sr"r, fie cel pu!,in egal cu pierderile si (2) rattria{,ia sd, fie coererntii, in fazil'.
R,eia,{ia generali, a arnplificririi intr-un sistem in care au loc tranzil,ii spon-
tanr, li tranzitii induse se cloduce folosind cazul clasic al corpului nggru la
c&!re llc-am referit la inceputul acestui paragraf. Lutnd iu consid,erare interac-
tia rlinrre fotoni;i elcctroni intr-*n semiconductor, rat:l tlc r"aria!,ie a tlen-
sitfl{ii fotonilor p(v) este datd, tle ecualia

d(pAv)/cld : "' Av ;- tBrrnz - Elrt,)pAv, (2.10)

T,

tnde A'r este l5rgimea benzii de frecvenlX (a liniei) ceea ce presupune c6,
radiatia are ftecven{,a cuprinsd, intre v qi v f Av.
relalinSot lu: -tiLalce,cturafliiienid(2l.u1n0g)imesetae tle forma exp(-a1,), unde s-a utilizat
si a*e r.aloatea cavit5,fii iar cr coefieientut do absorb,tie

*: _r1[ -8rcv2, " Avtz {\.nq"ri g-= ,,'} (2.11)
it

44

9F

(erz) '(lnZ-7 66) dxaagtyrl: I

fr"iffi,fr".ffi"5*' ;11 e+se-,?z tTllT"T

'Fi.{-'1o.ra4-.{.rqeg sor.lr^€c .r.u n'ecr_n1rA8uailr1uJb8pun*l+a"p*ii€"ia.?"qtriunn 1o,dff€ia".irA€c'ri;
,, F*%,,,
Z|i*ru5r*%},-Se***, ct ;lftT%f :?.frH.,h-ffi*"1;?lveroris
I e.rec rori?pryop.tresucoclrua+Sua.?c uI Kulmnl ap
,' K*".ts
a]sa olo aJ+ulp
lie-oiulJeo+.rs1op1o{eyau1.ard1neg"re.ad-gue(l.dt11+caqds!ee.rlu.re*gregc

1o::els1n(({X.uXruOstduOi€l+uSr?')o,som:ou.r:rd(*y|eO61"r6ZeeT9p1).arre{rdeordylou€e"ar!pd.nomslIancerut.?arpour1r+cr_FJ"Qroui+flr1n.€tLnfo;lsl('€nA#apYa:ap"ts(f+fysni;"o;,tf;?DJnut€oo?d"dro?':zr?"mSuHc'roc,rtrrr.*u_301gfuf;l.e*..d*gg:a",,00pJu:::n$.

'dos*1trus:,F

l1] er.rcs eluod es r"& r;reqq r.ro1g1.rnd eodl.rearp{.qra;rrodsqp€quorzpa.Irnd?ou"ralr?lprrJoaoJctsrr€oLrsurnrlur

aguza.rde"r ps aluod ,rc 'er{ou"ry1p ur.rd
-sutsq m.rd ag"reprerd plmzeldor (A-/1)8ot{7'li I (ea:recryrdrnts col o.ru apnn)
K^T?cts eeunr8al uT rrmuml rar{.q.rosqu a+tsJo?tsp ep"rep;rerd 1€?ou n€-s ,p oC

(ztz) u^.lrpp * IT T

161] ar.rcs as ar{rpuoc K+s€acy

a(('acn6r'a6uu'r(6euu5evr,.trrruSneBroglrerJq;rgF.mrd"orrsepuqueuaoaspo"oruroor1p;Jceourqlrocneauooondur+rSn€oealsa(o'.dotr3gaff?lces-'mrtpusuao";c-+Err€as+sr:usnel14mru'.(Irn1egp+'de6car)8aolr.ecJJreorgo{uJpro1g'J"eoaa8"orrppd-pr'e"lsrr1"eruuquEr1role1d<1aruroppoozquqEup.loa1-Jal.vrlrn"fsrrEdaan

pqc rcun+€ ?+ncpJsr+€s a1se ar{rpuoc K+s€ocy 'f.opol eriq.rosqe op €+r, gcseei;
-gdep gs r?+€1nun+s orsrrtro op €+€J ec er{lpuoc I€runu Tts+ncsrp €-s rcr€ KuId

:',.dp(s).{(a).,d I
J

,w (E)"{ 1sy'a\: zu,

nc rz, ri zu, tn1olrJoltsA csarncolr4 os Fc€p (ff'a) up aq+qo os ar€c
oept{rprauloscJa'l[uerf€]o(JS€z'Zrl)tsua"rr{ropJutsooc+Kcn+pIuuoIIcdrorupoqs o}so pulc rcrrn+€ auornl carpadenr{qeln.fduoqd
u1 'lu,rlasqo ur€
-u-<gr;zgugwqdd.rruyuuaceeldaepppvr*'Flanz+ruloiue(+arlncwrsdclroacJrd+eusrooJocop'+?1€c6rr-u:s)Jqgazlclafrgqmrluclda+srzumeoaz.zdIrl'va'((6asut una-cpsuvK"n?uS,v).oa,rn+rrn1ocqaulo8ee.au4suoror*u{.lruolnurd8coorrsq";qrfodudcru€olnrls€?aacsmpaau'.;irtql€u3occl

I-iurnina se reintoan'ce in punctul de unde a plecat, dup5, doud, retlcxii la
cele dou5, suprafele. Atunci cincl amplificarea este mai mare sau egal[ decit
pierderile, lurnini-soseqte in punctul de plecare >ftf_cel _puqliinreczuulatd,c,eeaqi irltensi-
(2.13)'
tate cu ca,re a plecat,-adic5, in relafia

-1 =</irJ?rexp (%gL 2 aL)"
ntCrroo-rtnmastaidgan1eer*il,nicdaoalrlrci:a:,Iea1.fotf2rome;eiraei,nozdtga,aursinetmdoeibn!cs,iltnacs!,cipornoiabnr!,eainriennpelcixfaipcvraietraesiatae.a(c2Ee.1vlo2idr)e'ununntddccef,e,-lesd-ciir--'
rnelsirinile cavit5,lii se aleg a"lafel ca naclia!,i:r, emisX c1c sistemul lespectiv
sntaulimonirarien.treUgnddeelejusrtantii,otnilai rde cse forrneazS, a'tunci cind cavi-
s5, formeze uncle lungime de unili,.

tatea oon!,ine un

2.3. ilIetode de realizarc a inversiei de poputrafio '

in semieonduetoare

p[2a2;_uJ,tupIiierioan,plittzrlcanrmespeaagijnevnceeurresfaaiezsSci i,eci,ieonlpdsoeepmuelliaeclcoietnrodsnoei"Fp1o{2a.p3tee] rgoeibc_.hteiinrlteedcetprcircit.nro^Innp-gtrcomal zppuarliinpopoi1rma,ic--
aicrea crr lurnin'i,, provenitS, de exe'rnplu tltl la un laser. Purt5furii genera,t,i
recombinl i:rtre ei qi dau radialyitt laser. Cu un la"ser clin GaAs cu jonc{'i-
une s-a iracliat o probi omogenii semiconcluctoare de fnSb. Radiatia laser
ernisf, d.e GaAs are lungimea de und5,, de 0,84 p m iar radia{,ia laser emis:i,
I)e asemenea,, cu :tjutonr]
de InS} are lungirnea de undi, t1e 5,3 pm [24'1.
unui laser cu GaAs cu joncliune a fost excitat uu laser ehn fnAs (sernicon-
A""to" ornogen), cu ajutorui unui
last'r cu Ile-Ne- (6 32SA) a fost txcita,t,
Aca)rectce.sltleetcnldifiacild.sci,psoemrepaa,ljizoepzeticjosnecluiutinlie-
u:r laser omogen clin CdSe ((i900
zeazd, in
speicial in ac.elc cazuri in
p-n ct scmiconductorul rcspectiv.
O altd, rnetodX cle realizare a inverrsiei d,e populalic constS, in lxrmlvar'-
rlarea sernienncluctorului eu fascic,ol dc elcctroni de energie tnare. Iilectronii
p5trund in scmiconductorul bombardat qi genereazzl, perechi electron gol care,

apoi, recombin[, ;i dau natlialie ]a,ser. Avind in ved"ere ci se pol, obfle energii

rnari (aproximativ 200 keV) ale fascicolului de electroni,se poate realiza inver-
sie d.e'populalie in materialele cu bandd, interzisi,lnare. Prin aceasti, metod5'
s-a oblinlt ra,dia!,ie laser ultru,violetii, in ZnS [25]' Fascicolul de electron.!
pude-dernl,rertelrtcurtanardooeensl-etigencotolmroecan,sotuentlerusitaiailndlapt,{ete,d.e,oEnetna1,etrelgringieceiaixEmp-Bereoesdsnteieeac5ednsa-ap1tr5:d0,0, dp4pee,m5ne.t)xrAEnpdrogeien"rn+cieai.rl&"t['@r2'e,6&,u]dun,indlceel=ei pd,trun-
aUst2 ,
perechi

-U' est'e
proporlional cu numdrul total de fononi optici implieat in proces (0r5 <
k -ll'<lev). Coneentm,lia pcrechilor olectron-gol genera'te cu fascicol de
eiectroni estei datd, de exPre.ria

n
1,6 .10-1t Ilo d

untle f esfu dencitatea d"e curent de electroni (-fi1'6 ' 10-re est€ num5,rul
carc cad intr-o smunclt, pe o suprafafd, tle semicon-
de electmni I cmz din
ductor) $i " - l,impul de viald, a perechilor electron-gnl. Un asemenea

46

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Inz€o op p{uy p{ue1ea op rrzuaq eauJF;rru ep leidoldu Itsur a+so r;rn1o8 rerlued
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q'k-^Il3E EeuniFeJ

=., ylf : (q) elcarlp orBzlrulod BI 13 (D)
rlrrrral nrqll.rr{ca ui u-d rlun-rlcuol u orF

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t',oun1Fa.r lr?+s op Jolrzoc ralir.redm g1r.r
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eleod os lcts+uoc 11

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absentei cozilor de stXri. Apare o situatie analogl cu cea de mai sus. in genertr,l
regiunea p a joncliunii p-n. este urmatX, de o regiune p+. La, cruent mai mare
poate ap5,rea emisie racliantS, qi ln regiunetu p*. DatoritS, efectului cirnpulni
electric in regiunea neutrii,, cu creqterea nivdului tle injectic marimul ira-
tensitdlii ra,dialiei se deplaseaz[, de la r'oncliune e5trc marginea legiunii
pce@lo*r)e1m3$21i .inEnreegriguinaeafoptofneilsotre ernili in regiunea p este de 1.47 eV iar
d"e 1,408eV, in laserul din Garls a
[li3].
l,a suprafala unui semioonductor, clakrrit5, st5,rilor de suprafald, poate
apare un strat de inversie ;i deci o jsoencre.taiulinr,eeazpra-titn(vfiegr.sia2.5c1ae)p. oLpaulpaoliLelrqizi aallee

dircctd,, cincl benzile se aplatizeazf
loe recombinarea radiantd, (fig. 2.1-r b). S-a obfinut in acest fel recoinbin:r,re

+b)-.1- -+- '-v

Ilig.2.5s.ie-de,{plaarsiufiaprarefacfoanurbninuiirrsiiernaidcoianndleucltnorstcraletuti]ptknr .inver-

rvpeaasedltoesiaatnrrneeataitaupiSlnin,crtalGeetnasnsAaeitrcsdce,i[snl3iaidarcd]di,m.qePiplieuannlustGiruueaplProeacf[aat3rlnid5cu,],.dmaIinJcitxeisisstptrtaeoanltsalepariolt[aasrtttgeeraqaattpueSltue,r'ie1naicsllieagueninonivieearaanrpsruleiiemcaainttddaue,i
purt5,tori liberi prin ionizare prin ciocnire 6i multiplicare in avalaryd, (ina-
inte de a apd,rea stratul de, inversie). La schimbqlea polariti,f,ii purtXtorii
sint injectali in volumr recombin5, r_adiani,. Sistg,rnul poate fulcliona
la tensiune alternativd. ^fnuntrd-eo semiperioadd, a tensiunii se gener€azi purtfi,-
tori de sarcin}, iar in cealalt5, semiperioadS, apare ratlialia laser. Menliond,m

c[ un spectru d.e rarlialie apa1e qi in timpul semiperioadei in care are loc
avalanqa insd, acesta se intind.e pe un domeniu larg de frecven!5, qi are
intensitate mai micd,.
lntr-o structur5, rnetal-izolator-semiconductor la o anumitX r'&loare
Iacotnednusciutonriui laupi lipcoattSt,ripneelsatrinucrtnuertfal_el(efcigtr.o2n.i6i )d, iinnjebcatnrldclau-tslee.I'aris,ltefen!l5goa_- lsueriryiin-
i:frTiJu$ii"l;1ffi'ffi"f#.iT ,S"ii:h*il"1;.;
- *-{ll-l-ff-i-,:" radiantd inCds 1361, semiconductor cu care nu
t- s-a putut realiza jonc-tiune p-2. Stratul izolator
trebuic sX fie suficient de sublire pentru a fi
posibil efectul tunel- Existi, pierderi datorate tu-
qv 1 | if -'ft.(,j,)., ieH,rii in rnetal a electronildr din banda de con-
*ll{ . ductieasemiconductorului.
-4J=E\---:* -

M 2.4. B'{ateriale utilizate in laserii en semieon-

duetoare

Itiij. 2.0. -- Ilccornltinarea ra- Ilaterialeie utiiizate cel mai mult pentru
diantl in structura f{OS. e.misia c1e lurnini, siut compusii semiconrluctori

48

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ternperatnlii intle 20 si 901i un laser cu (Pbse)r-" (snTe)., a fost acorrrat
pe un dorneniu de qi 12 prn (datoritd, va-
lungirni de undii, cuprins intle I
rlatiei cu ternpetatura a }i'rgimii benzii interzise) ; prin variatia curentului

7, J"*

u,t 10 40

,,Dh-r\-tC,1^_x*, <^

PFb:-"-S'.nl...-.-Tfe

PEhc 1-C*.

tft- iA/ >- XJcLJl_X

ffica,-"Tu

r-!

GoAs."Sb1- '

ln As" P1-,

Alr'JJ1-x/i5

GcAsrPt-*

-llxJLl 1-xA5 ,

G d Se" St-,
ZnrCdl,-*S

Iris. *2.7. tot,[it:,], tli;iili.$:tndi in cerc crnit rase-

Xlrin structurf lungimea de undil s-a variat pe un tlomeniu de 1pm 1401.
Sub influenla unui cimp magnt'tic pind, la 10kG un laser cu Pb,Snr_, T-e
amaelmefasoiipssiactiecaa.rliecnronclr-fd,ilanuanetdbnpaeeluanuzacinleinmcivplpoeemulremleuloniisriuemddcaeeegeen2ane2ectre-igc2fiea5fuc. .eStpetsrSnnds,,.ricclaerisemcuauppsaucranil,triedfninicaseagtrrtnigebeiautsicleicetrpelierpop-slcartlas5uegc,areizlcodloer,
de energie intr-un serniconductor este reprezentatd, in figura 2.8. Sub influ-
enla cimpului magnetic transversal curentul
de prag se micsoreazrar 1411. Presiunea hidro-
staticd, modific5 ld,rgimea benzii interzise a se-
".,n miconductorului^,si deci lungirnea de undd, a

radiatiei emise. fn GaAs l5,rgimea trenzii in-
terzis'e creqte cu creqterea prZsiunii hidrosta-

Ctteicoaenzrcqali.ucIzlneiaciPalubcnSegsiamtpueai arperaaorcasligiaturlaiae.fitieeersnitniesveecrs5se,dm,exi1oi4sq2toS1-.,
materiale semiconductoare cunoscute pine,
in prezent care emit radialie acoperind o
i'fEH)+*o*+itj,i.),'uI,l:cti,-,*ii.n.Io'oto:7'n,o'r1"1' 1Bpglrlilramf'nljlrdidrmdediefrer:clunlanumd:arp5gn,eiirms'iuelae.npl''donaeatneuunrdmeda,itltizndat"roie-nme0anJ,c3-eiulqat-diqBie_-r0c--lop-ummn.--
[;"iii. ?.ri. -- I'riuen{a c_'npului pus prin varialia fracliunii cle compozilie (in
;ttrgnetic iutens .sttprn ternari gi cuaternari), a curentuiui
l;ci stirilor perrnlslr ln :sle*n:*ic-on- c" o"-m^-rp*n;q--ii
rlirctoiirc (despicare r,anriau). electric, a ciurpului magnetic, a presiulii qi

5{J