Principles of Semiconductor Devices-L15

8/8/2019 Principles of Semiconductor Devices-L15

1/20

www.nanohub.org

NCN

Lecture15:SurfaceRecombination/Generationu amma s ra u am

[email protected]

Alam ECE606S09 1


2/20

Outline

1) Natureofinterfacestates

3) Surfacerecombinationindepletionregion

u

REF:ADF,

Chapter

5,

pp.

154

167

Alam ECE606S09 2


3/20

Surfacestates:Littlebitofhistory

HoernisdiagramofMesa andplanartransistors

DefectInduced SiliconoxideEmitter BaseEmitter Base

LeakagePath

CollectorCollector

Alam ECE606S09 3

One of the fundamental advances in semiconductor history


4/20

AtomicconfigurationofSurfaceStates

Singlebonds

Alam ECE606S09 4


5/20

SurfaceStates

x

E

Alam ECE606S09 5


6/20

MultipleLevelsofSurfaceStates

x

Alam ECE606S09 6


7/20

MultipleLevelsofSurfaceStates

xwrongokay

x

Alam ECE606S09 7


8/20

Outline

1) Natureof

interface

states

u 3) Surface

recombination

in

depletion

region

4) Conclusion

Alam ECE606S09 8


9/20

SurfaceRecombinationCurrent

Forsinglelevelbulktraps.

( ) ( )

2

1 1

1 1i

bulk np nR

n n p p=

+ + + ( ) ( )

2

1 1

1 1i T

np n

n n p p

N=

+ + +p nT T

c c p n

Forsin le

level

interface

tra

at

E

( )( ) ( )2

=s s i T

Dn p nR E

EE d

( ) ( )1 1+ + +s s s s ps ns

n n pc c

pCE

R R E dE =

Alam ECE606S09 9

VE


10/20

Case1:MinorityCarrierRecombination

( ) ( ) ( )20 00 0 + + s s is s IT n p nn p D E dE Donordoped

( ) ( )0 1 0 00 11 1

=

+ + + + +s s ss s s ps ns

n p pn n pc c

( )0

1

0

11

=

s IT

s s

s p D E dE

n p

n ns0+ns0

0

0

0 s

ps ps s ns sc c n c n

0

1 11

=

+ +

ps s IT

pss scn p

ps0+ps0

Alam ECE606S09 10

0 0s ns s


11/20

ConsidertheDenominator

1 111 ps psss ssn nc cp p= =

( ) ( )i iE EE E

00s sns ns DDn nc cN N

( ) ( )1

F iF i

ps

ns

i

E E E E

i i

i

nn e ec

= + +

ns0+ns0

( ) ( )1 F F

E E E E ps

ns

ce e

c

= + +

( )1 x x Fe ae x E E = + + ps0+ps0

Alam ECE606S09 11


12/20

ConsidertheDenominator

( ) ( )

1i i E E E E

psi icn e n e

D

= + + E D ns D

ciE

FE '( ) ( )1 F F E E E E ps

ce e

= + +ns

c

At 1 1psi i

i

D ns D

n n E E D

N c N = = + +

2D

At 0 1 1 2psF i

ns

c E E E , x D smallc

= > = = + +

FE 'FE iE

Alam ECE606S09 12

tF i

, sma= < = + + =


13/20

ApproximatetheDenominator

E

iE( ) ( )1i i

E E E E

psi i

D ns D

cn e n eD N c N

= + +

FE '

2D

1 for

otherwise

'

F F E E E

D

FE 'FE iE

Alam ECE606S09 13


14/20

IntegratedRecombination

C CE E

( ) 1 11= =

+ + V V

ps s

psE E s s R R E cn p

0 0s ns s

( )0 F

'

E

ps sc p D E dE 2

D

F

FE 'FE iE

Alam ECE606S09 14


15/20

SurfaceRecombinationVelocity

( )0 F

F

E

ps s IT

E

R c p D E dE

( ) 0' ps IT F F sc D E E p=

0sgs p=

Surfacerecombinationvelocity

Alam ECE606S09 15


16/20

Outline

1) Natureof

interface

states

ormu aa ap e o n er aces a es

3) Surfacerecombinationindepletionregion4) Conclusion

Alam ECE606S09 16


17/20

Case2:RecombinationinDepletion

( )( ) ( )2

1 1

=

i ITs sn p n D E dE

R E

1 1s s

ps ns

s sc c

~( ) ( )( )

=

i i

ii IT E E E E

nn D E dE

s+i i

ps nsc c

( )21

i

i

ns IT iE Ens

e dEc D n

ce

c

=

+ps~0

( )C iE E E

ns IT i

e dE R c D n

=

Alam ECE606S09 17

1iVE EnsE

ps

ec

+


18/20

Case2:RecombinationinDepletion

( )

2

C iE E E

ns IT iE E

e dE R c D n

c

=

( )iE Ee dE+

V

ps

e

c

+

( )21i

ns IT iE Ens

ps

c D nc

e

c

= +

ns~0

~

2

01

ps

ns IT i

ns

c dxc D n

c x

+

= +

s

ns ps IT ic c D n

=

Alam ECE606S09 18


19/20

Whydodonors/acceptorsnotactasRGCenters?

( )( )0 ps s

D

c p D E dE R E

=

1 1

0 01

pss s

s ns s

n p

n c n+ +

( )

00

Dps

D

s Nc p

D E

=

2D

( )( )0

1 1

ps s

A

pss s

c p D E dE R E

cn p

=

FE 'FE iE

0 0s ns sn c n

0 As s Nc p

Alam ECE606S09 19

( )AD E=


20/20

Summary

Interface (depletion)2ns ps IT i R c c D n=

( ) Interface (minority)'

ps IT F F sR c D E E p=

Bulk minorit R c N =

Alam ECE606S09 20

Documents

Principles of Semiconductor Devices-L15