Question

The value indicated by Fermi energy level in an intrinsic semiconductor is

• A. the average energy of electrons and holes.
• B. the energy of electrons in conduction band.
• C. the energy of holes in valence band.
• D. the energy of forbidden region.

Answer 1

The correct option is A the average energy of electrons and holes.

In an intrinsic semiconductor, $n=p$, where, $n$ is number of electrons and $p$ is number of holes in intrinsic semiconductor.
This implies that there is an equal chance of finding an electron at the conduction band edge as there is of finding a hole at the valence band edge. Thus, the average energy level of electrons and holes is half of the energy band gap in intrinsic semiconductors. Also the Fermi energy level lie exactly in the middle of energy band gap in intrinsic semiconductors. Thus, the value indicated by Fermi energy level in an intrinsic semiconductor is the average energy of electrons and holes.