2 2 Carrier Transport at the PN Junction Ptype Ntype Ptype Ntype Depletion region 3 3 Formation of Depletion Region Space charge regiondepletion region region depleted of charge carries electrons or holes ID: 776405
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Chapter 7, PN Junction19 and 21 February 2020
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2
Carrier Transport at the PN Junction
P-type
N-type
P-type
N-type
Depletion region
Slide33
3
Formation of Depletion Region
Space charge region=depletion region= region depleted of charge carries (electrons or holes)
Space charges: ionized acceptor atoms in the p-side and ionized donor atoms in the n- side. Space charges cannot move.
Slide44
4
PN Junction Under Equilibrium Condition— band diagram
Features under equilibrium condition (zero bias):
The Fermi-level is flat throughout the whole junction The diffusion force is balanced by the internal E-field built by the space charges (this is why the depletion region is limited)
Slide5Band Bending and Built-in Potential
Slide6Slide7Slide88
8
E-field in the Depletion Region
Slide9Slide10Built-in Potential
Band bending:
Solution for
V
bi
from Fermi-functions
Slide11Slide12Width of Depletion Region
x
p
x
n
W
12
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