Silicon, Circuits, and the Digital Revolution
Doping Semiconductors - Donors
- What happens if we add a few atoms of arsenic?
Recall the periodic table and electronic configurations:
||[neon] 3s2 3p2
||[argon] 4s2 4p1
||[argon] 4s2 4p3
- Arsenic has one more valence electron than silicon
-- when it is placed substitutionally in the lattice for a Si atom four of
the valence electrons bind to neighboring Si atoms, the one left over becomes
free for conduction
- In the band structure picture, impurity states are created much closer to
the conduction band
- These states are known as donors, since they "donate" electrons to the conduction
- It is much easier to "liberate" the electron for conduction at lower thermal
- A semiconductor doped with donors is known as an "n-type" semiconductor.
(n for negative charge carrier)
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Last updated April 20, 2000.
© George Watson, Univ. of Delaware, 2000.