ECE 474: Principles of Electronic Devices

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ECE 474Principles of Electronic Devices

• Prof. Virginia Ayres
• Electrical Computer Engineering
• Michigan State University
• ayresv_at_msu.edu

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Lecture 30
Chp. 05 Current State-of-Art Transistors

• Introduction to pn junctions

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Transistor a device for binary logic (Chp. 06)
n
n
OFF
p
Si
ON Linear (ohmic) regime
n
n
p
Si
ON Saturation regime
n
n
p
Si
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Transistor a device for binary logic (Chp. 06)
n
n
OFF
p
Si
n
n
p
Si
n
p
Si
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pn junction Energy picture
p0 1013 cm-3
n0 1017 cm-3
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pn junction Energy picture individually
p0 1013 cm-3
n0 1017 cm-3
EC
EC
EF
Egap 1.1 eV
Egap 1.1 eV
0.407 eV
Ei
Ei
EF
0.2 eV
EV
EV
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pn junction Energy picture individually
Align the Fermi energy levels
p0 1013 cm-3
n0 1017 cm-3
EC
Egap 1.1 eV
Ei
EC
EF
EF
0.2 eV
Egap 1.1 eV
0.407 eV
Ei
EV
EV
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pn junction Energy picture individually
Align the Fermi energy levels
p0 1013 cm-3
n0 1017 cm-3
EC
Egap 1.1 eV
Ei
EC
EF
0.2 eV
Egap 1.1 eV
0.407 eV
Ei
EV
EV
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pn junction Energy picture
Connect the dots
p0 1013 cm-3
n0 1017 cm-3
EC
Egap 1.1 eV
Ei
EC
EF
EF
0.2 eV
Egap 1.1 eV
0.407 eV
Ei
EV
EV
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pn junction Energy picture
Junction
p0 1013 cm-3
n0 1017 cm-3
EC
Egap 1.1 eV
Ei
EC
EF
0.2 eV
Egap 1.1 eV
0.407 eV
Ei
EV
EV
Depletion region W
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pn junction Expanded picture of junction
Junction
p0 1013 cm-3
n0 1017 cm-3
EF
EF
B B B- B-
P P P P P P P P P
xp0
xn0
Depletion region W
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pn junction Expanded picture of junction
Junction
p0 1013 cm-3
n0 1017 cm-3
EF
EF
B B B B-
P P P P P P P P P
Unbalanced
If xp0 xn0
Depletion region W
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pn junction another Built-in E-field
Junction
p0 1013 cm-3
n0 1017 cm-3
qV0 0.2 eV 0.407 eV 0.607 eV
Ei
EF
EF
B B B- B-
P P P P P P P P P
Ei
Neutral region p-side
Neutral region n-side
E (x)
Depletion region W
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pn junction new Energy Barrier
Junction
p0 1013 cm-3
n0 1017 cm-3
qV0 0.2 eV 0.407 eV 0.607 eV
Ei
EF
EF
B B B- B-
P P P P P P P P P
Ei
Neutral region p-side
Neutral region n-side
E (x)
Depletion region W