Condensed Matter - Semiconductor

In an n-type semiconductor, which of the following is true of impurity atoms?

1. They accept electrons from the filled valence band into empty energy levels just above the valence band.
2. They accept electrons from the filled valence band into empty energy levels just below the valence band.
3. They accept electrons from the conduction band into empty energy levels just below the conduction band.
4. They donate electrons to the filled valence band from donor levels just above the valence band.
5. They donate electrons to the conduction band from filled donor levels just below the conduction band.

(GR9677 #78)

Solution:

Semiconductor:

n-type:

• n for negative-charge
• atoms have extra electron
• donors to the conduction band

p-type:

• p for positive-charge (holes)
• atoms have missing electrons
• acceptors in the valence band

Source: physics.udel.edu

Answer: E 

Solid State Physics - Hall Effect

The Hall effect is used in solid-state Physics to measure

A. ratio of charge to mass
B. magnetic susceptibility
C. the sign of the charge carriers
D. the width of the gap between the conduction and valence bands
E. Fermi energy

(GR8677 #50)

Solution:

Hall effect is the production of voltage difference (Hall voltage) across a current-carrying conductor under the influence of a magnetic field.

Hall voltage can be used to reveal the sign of the charge carriers.

Answer: C