A1261155613xPzhJ

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Chem 140a
Lecture Notes 8 Class 10
Recombination-Generation Statistics
(R-G) (Shockley-Read-Hall statistics)
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ltReviewgt
ns
nb
?p
3
ltReviewgt
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Five Mechanisms
Majority carrier process
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Ecb
Thermionic Emission Tunneling
1
2
2
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Minority carrier process
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Bulk Recombination Depletion Region
Recombination Surface Recombination
3
ET
Evb
4
4
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Under light or a bias, npgtni2. So there is a
driving force to return to the equilibrium. Extra
holes will recombine with extra electrons ?
Recombination If somehow we were sucking
carriers out of a region of the SC, npltni2 and
carriers would be generated ? Generation
Shockley-Read-Hall statistics Good model for all
of these minority carrier processes
of recombination
in the SC
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Bulk Recombination
e-
Ecb
1
2
kn
kn
ET
kp
kp
3
4
Evb
p
1
2
cm-3sec-1
cm-3
cm-3
3
(unitless)
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cm3/sec has an analogy with
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Bulk Recombination
e-
Ecb
1
2
kn
kn
ET
kp
kp
3
4
Equilibrium conditions Principle of detailed
balance ? All fundamental processes and their
inverse processes must self balance
Evb
p
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Bulk Recombination
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Bulk Recombination
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Bulk Recombination
Steady state relationship Major assumption in
device problems and analysis At steady state, (
Different from the equilibrium)
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Bulk Recombination