Solid State Device Fundamentals

Transcription

1 Solid Stat vic Fundamntal ES 345 Lctur Cour by landr M. Zaitv Tl: b Collg of Statn Iland / CUY

2 p-n Junction p-n junction i a phyical contact of p- and n-typ miconductor. p-n-junction i prnt almot in vry miconductor dvic. Mtallurgical junction n-typ layr can b formd by ion implantation and/or diffuion of donor into p-typ miconductor and vic vra. onor ovrcompnat accptor, or accptor compnat donor. n-typ p-typ ubtrat dopd with accptor Eampl of fabrication f p-n junction Collg of Statn Iland / CUY

3 Charg carrir ditribution in p-n junction oping ditribution of an abrupt p-n junction n p diffuion Equilibrium concntration of charg carrir in p- and n-typ miconductor bfor and aftr phyical contact. Collg of Statn Iland / CUY 3

4 pltion layr Total currnt through p-n- junction at quilibrium qual zro: pltion layr i formd by civ (non-quilibrium) lctron and hol. Collg of Statn Iland / CUY 4

5 Spac charg rgion Spac charg rgion i formd by uncompnatd chargd donor and accptor. Collg of Statn Iland / CUY 5

6 Enrgy band diagram of p-n junction n-rgion p-rgion E f E f i contant at quilibrium E c E c E v E f E v E c E f E v E c and E v ar known rlativ to E f E c and E v ar mooth, th act hap to b dtrmind. utral n-rgion pltion layr utral p-rgion E c E f E v dpltion layr it at th p-n junction whr n 0 and p 0. Collg of Statn Iland / CUY 6

7 Built-in potntial n-typ d p-typ a f bi E C E F E V f bi V n p 0 Built-in potntial Φ bi qual diffrnc btwn th Frmi lvl in p- and n-typ miconductor. Can th built-in potntial b maurd with a voltmtr? Collg of Statn Iland / CUY 7

8 Calculating built-in potntial n-rgion p-rgion n n i n C C B kt kt B kt ln kt ln C ni C f bi B kt C ln ni ln C f bi kt ln ni Φ bi B Built-in potntial dpnd on th miconductor matrial th p-n junction i mad of. For dopant concntration ovr cm -3 : f bi E g E E Collg of Statn Iland / CUY 8

9 Homwork 1. I it poibl to maur built in potntial with a voltmtr?. If trminal of a p-n junction diod ar hort-circuitd, do currnt flow on th outid circuit? 3. Calculat built-in potntial in Si and G p-n diod dopd with donor and accptor to concntration of am -3 and cm -3 rpctivly. Collg of Statn Iland / CUY 9

10 Gau Law: Poion Equation : prmittivity (~1 o for Si) : charg dnity (C/cm 3 ) E () E( + ) Poion quation Collg of Statn Iland / CUY 10

11 d a (a) ut ral Rgion pltion Layr utral R gi (b) Charg and lctric d fild in th a P dpltion layr P d E d (b) (c) (c) On th n-id: = ut ral Rgion n 0 p 0 n p q d n n q d pltion Layr q a q a p p utral R gi on P On th p-id: = (d) E ( ) ( - ) (d) () Built-in lctric fild in p-n partmnt of Enginring (f) Scinc and Phyic f bi f bi n 0 p V n 0 p V n () n p p junction i maimal E ma at Ema E c n p f bi, built-in potntial q E ( ) C 1 ( P ) mtallurgical intrfac: E c bi 11 Collg of Statn Iland / CUY

12 (a) Charg in th dpltion layr d a P (b) ut ra l R gion pl tion La yr utral R gi on n 0 p n Th lctric fild i continuou at = 0. p P (c) q d p = n Low-dopd id of th junction i dpltd to a gratr dpth. n q a p on-idd junction i calld a n + -p junction ( >> ), or p + -n junction ( << ). Collg of Statn Iland / CUY 1

13 q d (c) n p Potntial in th dpltion Layr q a (d) () (f) f bi f bi, built-in potntial n 0 p P V n p P E c E f E v On th p-id, a V ( ) ( P ) rbitrarily choo th voltag at = P a V = 0. On th n-id, d V ( ) C ( f bi d ( ) ) Collg of Statn Iland / CUY 13

14 Homwork Calculat potntial at th mtallurgical junction in Si and G p-n diod dopd with donor and accptor to concntration of am -3 and cm -3 rpctivly. Collg of Statn Iland / CUY

15 (a) Width of th dpltion layr d a P (b) ut ra l R gion pl tion La yr utral R gi on P n 0 p V i continuou at = 0 P W dp fbi 1 1 If >>, a in a p + -n junction, (c) W dp fbi n q d p q P a d 0 Width of an aymmtrical p-n junction: i lightr dopant dnity. W dp f bi (d) Collg of Statn Iland / CUY 15

16 EXMPLE: a p + -n junction ha =10 0 cm -3 and =10 17 cm -3. Find: a) Φ bi, b) W dp, c) n, and d) p. a) f bi kt ln 0.06 ln 0 n i 1V b) W dp fbi / 0.1 μm c) n W dp 0.1 μm d) p n μm 0.1 nm 0 16 Collg of Statn Iland / CUY

17 Homwork Calculat width of th dpltion layr, maimum lctric fild and pac charg in Si and G p-n diod dopd with donor and accptor to concntration of am -3 and cm -3 rpctivly. 17 Collg of Statn Iland / CUY

18 p-n Junction: Summary f bi kt ln ni p = n W dp f j 1 1 W dp f j E ma n p f j 18 Collg of Statn Iland / CUY