Solid State Device Fundamentals

Transcription

1 Sold State Devce Fudametals 9 polar jucto trasstor Sold State Devce Fudametals 9. polar Jucto Trasstor NS 345 Lecture ourse by Alexader M. Zatsev alexader.zatsev@cs.cuy.edu Tel: N101b Departmet of geerg Scece ad Physcs ollege of State slad / UNY

2 Sold State Devce Fudametals What s JT? 9 polar 8 ased jucto p- Jucto trasstor polar Jucto Trasstor (JT) s a electroc valve cotrollg curret flow. ommoly t s used as curret swtch, or curret amplfer. p--p trasstor -p- trasstor Departmet of geerg Scece ad Physcs ollege of State slad / UNY

3 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ad structure of -p- JT Prcple of JT V N + P N mtter ase ollector 0 V V V s a expoetal fucto of forward bas V ad depedet of reverse bas V. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 3

4 Sold State Devce Fudametals ommo-emtter cofgurato 9 polar 8 ased jucto p- Jucto trasstor As a put parameter, s preferred over V Departmet of geerg Scece ad Physcs ollege of State slad / UNY 4

5 Sold State Devce Fudametals ollector curret depleto layers 9 polar 8 ased jucto p- Jucto trasstor Dffuso equato: d dx L L oudary codtos : t D N + P N emtter base collector x 0 W t - base recombato lfetme D - base morty carrer (electro) dffuso coeffcet N - base dopg cocetrato 0 = /N xcess charge carrer cocetrato jected to base: (0) ev / kt 0( e 1) xcess charge carrer cocetrato at the collector jucto: Departmet of geerg Scece ad Physcs ev / kt ( W ) ( e 1) 0 0 ollege of State slad / UNY 5 0

6 Sold State Devce Fudametals Approxmato of thg base 9 polar 8 ased jucto p- Jucto trasstor Soluto of the dffuso equato: ( x) 0 ( e ev / kt 1) sh ( W x) / L sh W / L Moder JTs have base wdths of about 0.1 μm, whch s much smaller tha the typcal dffuso legth of tes of mcros: W << L ( x )/ (0) e qv 1 ( x) N N kt 1 ( e qv / kt 1) ( x) (0)(1 N ( e ev x / W / kt ) 1)(1 x / W ) 0 x/ 1 x/ W Departmet of geerg Scece ad Physcs ollege of State slad / UNY 6

7 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ollector curret: dffuso curret through the base A ed d dx A D e W N ( e ev / kt 1) S ( e ev / kt 1) S s the saturato curret t ca be show that A e G ( e ev / kt 1) p s the majorty carrer cocetrato the base G s the base Gummel umber Departmet of geerg Scece ad Physcs ollege of State slad / UNY 7

8 Sold State Devce Fudametals Low-level jecto 9 polar 8 ased jucto p- Jucto trasstor geeral case of o-uform base ad hgh-level jecto codto, the Gummel umber ca be foud as: G W 0 p D dx At low level jecto N, p = ; D = costat; p(x) = N (x) The physcal meag of the base Gummel umber s the resstace of base for the morty charge carrer curret flowg from emtter to collector. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 8

9 (A) Sold State Devce Fudametals Hgh-level jecto 9 polar 8 ased jucto p- Jucto trasstor Hgh-level jecto effect At large V p p p e e( e F ev p Fp / )/ kt kt p N e ev / kt kf, the kee curret V 60 mv/decade low jecto 10 mv/decade hgh jecto G p e ev / kt e ev / kt s a expoetal fucto of V. Whe p > N, verse slope s 10 mv/decade. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 9

10 Sold State Devce Fudametals ase curret 9 polar 8 ased jucto p- Jucto trasstor (a) emtter base collector electro flow + hole flow p ' ' Some holes are jected from the p-type base to the + emtter. The holes are provded by the base curret,. W W Departmet of geerg Scece ad Physcs ollege of State slad / UNY 10

11 Sold State Devce Fudametals alculatg base curret 9 polar 8 ased jucto p- Jucto trasstor A q G ( e qv / kt 1) For a uform emtter, G W 0 D dx A D e W N ( e ev / kt 1) t s desrable to keep as low as possble. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 11

12 Sold State Devce Fudametals urret ga 9 polar 8 ased jucto p- Jucto trasstor ommo-emtter curret ga, : ommo-base curret ga α: 1 / / 1 1 G G DW D W N N How ca be maxmzed? Departmet of geerg Scece ad Physcs ollege of State slad / UNY 1

13 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor XAMPL: urret ga A JT has = 1 ma ad = 10 µa. What are, β ad α? Soluto: / / 1mA 10 μa 1.01mA 1mA /10 μa 100 1mA /1.01mA We ca cofrm 1 ad 1 Departmet of geerg Scece ad Physcs ollege of State slad / UNY 13

14 Sold State Devce Fudametals F F urret-voltage characterstcs of JT = max 9 polar 8 ased jucto p- Jucto trasstor F R ~ R R 0 Departmet of geerg Scece ad Physcs ollege of State slad / UNY 14

15 Sold State Devce Fudametals JT as a amplfer 9 polar 8 ased jucto p- Jucto trasstor P >> P V V Departmet of geerg Scece ad Physcs ollege of State slad / UNY 15

16 Sold State Devce Fudametals mtter badgap arrowg 9 polar 8 ased jucto p- Jucto trasstor N N To rase, N s typcally very large. Ufortuately, large N makes (heavy dopg effect). N NVe g / kt Sce s related to g, ths effect s also kow as bad-gap arrowg. g / kt e g s eglgble for N < cm -3, s 50 mev at cm -3, 95 mev at 10 0 cm -3, ad 140 mev at 10 1 cm -3. mtter badgap arrowg makes t dffcult to rase by dopg the emtter very heavly. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 16

17 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor Narrow-badgap base ad heterojuco JT N N To further elevate, we ca rase by usg a eptaxal S 1-h Ge h base. S S 1-h Ge h S Wth h = 0., g s reduced by 0.1eV ad by 30x. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 17

18 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor XAMPL: mtter badgap arrowg ad SGe ase Assume D = 3D, W = 3W, N = cm -3, ad =. What s for (a) N = cm -3, (b) N = 10 0 cm -3, ad (c) N = 10 0 cm -3 ad a SGe base wth g = 60 mev? (a) At N = cm -3, g 50 mev, e g / kt e 50 mev/ 6 mev e DW D W N N (b) At N = 10 0 cm -3, g 95 mev 38 F 4 (c) e g / kt e 60 mev/ 6 mev Departmet of geerg Scece ad Physcs ollege of State slad / UNY 18

19 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor 1. Assume D = 10 cm /s, D = 40 cm /s, W m, W - 50 m, N = cm -3. Fd β ad α for: (a) N = cm -3, (b) N = cm -3, Homework (c) N = 10 0 cm -3 ad a SGe base wth Δ g = 80 mev,. alculate β ad α for the trasstor descrbed above but wth the base dopg cocetrato gradually chagg from to cm alculate collector ad base currets of the trasstors descrbed above. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 19

20 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor Gummel plot ad fall-off at hgh ad low c SR curret From top to bottom: V = V, 1V, 0V Low low power devces Hgh hgh power devces Departmet of geerg Scece ad Physcs ollege of State slad / UNY 0

21 Sold State Devce Fudametals ase-wdth modulato by collector voltage 9 polar 8 ased jucto p- Jucto trasstor Output resstace : r 0 V 1 V A 3 Large V A (large r o ) s desrable for a large voltage ga V A : arly Voltage V A 0 V 1 Departmet of geerg Scece ad Physcs ollege of State slad / UNY 1

22 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ase-wdth modulato by collector voltage V N + P N emtter base collector V W 3 W W1 }V 1 < V <V 3 ' x How the base-wdth modulato effect ca be reduced? Departmet of geerg Scece ad Physcs ollege of State slad / UNY

23 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ase-wdth modulato by collector voltage The base-wdth modulato effect s reduced f we (A) crease the base wdth, () crease the base dopg cocetrato, N, () decrease the collector dopg cocetrato, N. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 3

24 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor Trast tme ad charge storage Whe the jucto s forward-based, excess charge carrers are stored the emtter, the base, ad eve the depleto layers. Q F s all the stored excess hole charge: t F Q F Trast tme τ F s dffcult to predct accurately but t ca be measured. τ F determes the hgh-frequecy lmt of JT operato. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 4

25 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ase charge storage ad base trast tme p' = ' p (0) 0 xcess hole charge ad trast tme the base = N qv ev/ kt kt ( e 1) 1 Q F qa (0) W / Q F t F W D 0 W x Departmet of geerg Scece ad Physcs ollege of State slad / UNY 5

26 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor XAMPL: ase trast tme What s t F f W = 70 m ad D = 10 cm /s? Aswer: t F W D 6 (710 cm) 10 cm /s s.5 ps.5 ps s a very short tme. Sce lght speed s m/s, lght travels oly about 0.7 mm.5 ps. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 6

27 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor Homework alculate hgh frequecy lmt of the trasstors descrbed o slde 19. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 7

28 Sold State Devce Fudametals Drft trasstor bult- feld 9 polar 8 ased jucto p- Jucto trasstor The base trast tme ca be reduced by buldg to the base a drft feld that ads the flow of electros. Two methods: Fxed g : N decreases from emtter ed to collector ed. - c f v Fxed N : g decreases from emtter ed to collector ed. - c f 1 e d c dx v Departmet of geerg Scece ad Physcs ollege of State slad / UNY 8

29 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor mtter-to-collector trast tme To reduce the total trast tme, emtter ad depleto layers must be th, too. Krk effect or base wdeg: At hgh the base wdes to the collector. Wder base meas larger t F. Top to bottom : V = 0.5V, 0.8V, 1.5V, 3V. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 9

30 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor ase wdeg at large c A qv sat base N collector N + collector d dx qn qn q / e s A v sat base wdth base depleto layer N N + collector x collector x base wdth depleto layer Departmet of geerg Scece ad Physcs ollege of State slad / UNY 30

31 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor JT summary The base-emtter jucto s usually forward-based whle the base-collector s reverse-based. V determes the collector curret,. e ev / kt A ( e 1) G G W 0 p D dx G s the base Gummel umber, whch represets all the subtletes of JT desg that affect. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 31

32 Sold State Devce Fudametals JT summary 9 polar 8 ased jucto p- Jucto trasstor The base (put) curret,, s related to by the commoemtter curret ga,. Ths s related to the commo-base curret ga,. G G 1 G G DW D W N N Departmet of geerg Scece ad Physcs ollege of State slad / UNY 3

33 Sold State Devce Fudametals 9 polar 8 ased jucto p- Jucto trasstor JT Summary ase-wdth modulato by V results a sgfcat slope of the vs. V curve the actve rego (kow as the arly effect). Due to the forward bas V, a JT stores a certa amout of excess carrer charge Q F whch s proportoal to. Q F t F t F s the forward trast tme. f o excess carrers are stored outsde the base, the t F t F W D, the base trast tme. Departmet of geerg Scece ad Physcs ollege of State slad / UNY 33