Handout 2
ECE 315, Cornell University
1
Overview of Semiconductors and P-N
Junctions
What you will learn:
•
Intrinsic (pure) and extrinsic (doped) semiconductors.
•
Carrier statistics in equilibrium and under bias.
•
Basic differential equations to model the semiconductor
devices.
•
Electrostatics of P-N junction diodes
•
Diode IV: reverse bias, reverse-bias with injection, weak
forward-bias, resistive.
Handout 2

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Handout 2
ECE 315, Cornell University
2
2.1. Statistics of Electrons and holes in
homogeneous semiconductors
•
Electrons and holes in intrinsic semiconductors
•
N-type and P-type doping semiconductors
•
Electrons and holes in equilibrium and quasi-neutral
relations.
•
Carrier statistics in N-type and P-type semiconductors.
Sedra and Smith: Sec. 3.7

Handout 2
ECE 315, Cornell University
3
•
Semiconductor is the class of material where the
conductivity of the material can be controlled to vary a
large orders of magnitude, i.e., > 10
10
, (metal: conductivity
always high; insulator: conductivity always low).
–
Elemental semiconductor: Si, Ge
–
Compound semiconductor (fixed composition): SiC, GaAs, GaN
–
Alloy: Si
1-x
Ge
x
, Al
1-x
Ga
x
As, Hg
1-x
Cd
x
Te, etc.
•
Purity: semiconductor devices are made of semiconductors
with ultra purity: unintentional doping < 10
-9
in part, i.e.,
0.001 ppm in solids
–
To increase range of control in conductivity (lower leakage when
devices are switched off, faster switching when devices are on)
–
To increase mobility (faster and less power consumption from
lower resistivity)
Introduction to Semiconductors

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