Question

In a semiconductor, if the Fermi energy level lies in the conduction band, then the semiconductor is known as

• A. degenerate n-type.
• B. degenerate p-type.
• C. non-degenerate n-type.
• D. non-degenerate p-type.

Hint:

If the Fermi level lies {inside} a band (conduction or valence), the semiconductor is {degenerate}. If it lies {within the bandgap but close to a band}, the semiconductor is {non-degenerate}.

Answer 1

The Correct Option is A

Step 1: Recall Fermi level position.
In intrinsic semiconductors, the Fermi level lies around the middle of the bandgap.
In extrinsic (doped) semiconductors: - For n-type: Fermi level shifts closer to the conduction band.
- For p-type: Fermi level shifts closer to the valence band.
Step 2: Condition for degeneracy.
When doping is so high that the Fermi level moves into the conduction band, the semiconductor behaves almost like a metal. This is called a degenerate n-type semiconductor.
Step 3: Eliminate other options.
- (B) Degenerate p-type: occurs if Fermi level lies in valence band (not conduction band).
- (C) Non-degenerate n-type: Fermi level lies close to but below the conduction band.
- (D) Non-degenerate p-type: Fermi level lies close to but above the valence band.
Hence, the correct answer is (A).
\[ \boxed{\text{degenerate n-type}} \]