Principles of Semiconductor Devices-L15
Transcript of Principles of Semiconductor Devices-L15
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Lecture15:SurfaceRecombination/Generationu amma s ra u am
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Outline
1) Natureofinterfacestates
3) Surfacerecombinationindepletionregion
u
REF:ADF,
Chapter
5,
pp.
154
167
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Surfacestates:Littlebitofhistory
HoernisdiagramofMesa andplanartransistors
DefectInduced SiliconoxideEmitter BaseEmitter Base
LeakagePath
CollectorCollector
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One of the fundamental advances in semiconductor history
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AtomicconfigurationofSurfaceStates
Singlebonds
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SurfaceStates
x
E
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MultipleLevelsofSurfaceStates
x
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MultipleLevelsofSurfaceStates
xwrongokay
x
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Outline
1) Natureof
interface
states
u 3) Surface
recombination
in
depletion
region
4) Conclusion
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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 =
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VE
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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
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0 0s ns s
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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
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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
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tF i
, sma= < = + + =
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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
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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
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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
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Outline
1) Natureof
interface
states
ormu aa ap e o n er aces a es
3) Surfacerecombinationindepletionregion4) Conclusion
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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
=
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1iVE EnsE
ps
ec
+
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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
=
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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
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( )AD E=
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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 =
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