note2slides - Handout 2 Overview of Semiconductors What you...

Handout 2 ECE 315, Cornell University 1
Overview of Semiconductors
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.
Handout 2

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