Question

In an extrinsic p-type semiconductor, which of the following schematic diagram depicts the variation of the Fermi energy level (E_F) with temperature (T) ?

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is A

To determine the correct schematic diagram that depicts the variation of the Fermi energy level (E_F) with temperature (T) in an extrinsic p-type semiconductor, we must understand how Fermi energy behaves in such materials.

Understanding Extrinsic p-Type Semiconductor:

• An extrinsic p-type semiconductor has an abundance of holes as the majority charge carriers.
• This is typically achieved by doping a pure semiconductor with an acceptor impurity which introduces more holes than electrons.
• At absolute zero, the Fermi level is located near the valence band; as the temperature increases, the Fermi level shifts toward the middle of the energy gap.

Temperature Variation:

• For p-type semiconductors at low temperatures, E_F is closer to the valence band.
• As temperature rises, thermally generated carriers lead to E_F moving slightly upwards towards the intrinsic level because the band gap effectively narrows.

Identifying the Correct Schematic:

Among the provided diagrams, the one that correctly shows E_F starting closer to the valence band and moving towards the center of the band gap with an increase in temperature is the correct representation.

This image accurately reflects the behavior of E_F in an extrinsic p-type semiconductor with temperature change.

Conclusion:

The Fermi level in an extrinsic p-type semiconductor will shift from near the valence band towards the middle of the energy gap as temperature increases. Therefore, the correct schematic diagram is Option 1.