PHYS 3310 Module 11.3

Semiconductors and Doping

11.3 Semiconductors and Doping

Describe changes to the energy structure of a semiconductor due to doping
Distinguish between an n-type and p-type semiconductor
Describe the Hall effect and explain its significance
Calculate the charge, drift velocity, and charge carrier number density of a semiconductor using information from a Hall effect experiment

Practice!

Practice 11.3.1
How would you expect the electric conductivity of a semiconductor to vary with increasing temperature?
A. It should increase, because more electrons are thermally excited from the valence band into the conduction band.
B. It should increase, because more electrons are removed from their parent atoms and added to the valence band.
C. It should decrease, because the added thermal energy breaks apart correlated electron pairs.
D. It should decrease, because the atoms in the crystal will vibrate more and thus block the flow of electrons.
E. It should remain the same, because the band structure does not depend on temperature.

Check your answer: A. It should increase, because more electrons are thermally excited from the valence band into the conduction band.

Practice 11.3.2
With all those negative charge carriers in the conduction band, we call this an n-type semiconductor. What is the net charge charge on this material?
A. positive
B. negative
C. zero

Practice 11.3.3
With all those positive charge carriers in the valence band, we call this a p-type semiconductor. What is the net charge charge on this material?
A. positive
B. negative
C. zero

Practice 11.3.4
Compared to an intrinsic (pure) semiconductor, what should you expect the conductivity of an n-type doped semiconductor to be?
A. lower conductivity
B. the same conductivity
C. higher conductivity

Check your answer: C. higher conductivity

Practice 11.3.5
Compared to an intrinsic (pure) semiconductor, what should you expect the conductivity of an p-type doped semiconductor to be?
A. lower conductivity
B. the same conductivity
C. higher conductivity

Check your answer: C. higher conductivity

Practice 11.3.6
The difference between donor and acceptor atoms in a doped semiconductor is that
A. the donor energy level lies halfway between the valence band and the acceptor level.
B. the donor energy level lies near the valence band and the acceptor energy level lies near the conduction band.
C. donor energy levels cannot exist unless acceptor energy levels are present.
D. the donor energy level lies near the conduction band and the acceptor energy level lies near the valence band.
E. the acceptor energy level lies halfway between the conduction band and the donor energy level.

Check your answer: D. the donor energy level lies near the conduction band and the acceptor energy level lies near the valence band.