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Chapter 7, PN Junction 25 and 27 February 2015

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Presentation on theme: "Chapter 7, PN Junction 25 and 27 February 2015"— Presentation transcript:

1 Chapter 7, PN Junction 25 and 27 February 2015

2 Carrier Transport at the PN Junction
P-type N-type P-type N-type Depletion region 2 2 2

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. 3 3 3

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) 4 4 4

5 Band Bending and Built-in Potential

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8 E-field in the Depletion Region
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10 Built-in Potential Band bending: Solution for Vbi from Fermi-functions
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12 Width of Depletion Region
xp xn W 12 12

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