Question

Arrange the following types of materials in decreasing order of Fermi energy level from valence band:
A. \(p\)-type semiconductor,
B. \(n\)-type semiconductor,
C. Intrinsic semiconductor,
D. \(n\)-type degenerate semiconductor.

• A. C, B, A, D
• B. B, C, D, A
• C. D, B, C, A
• D. A, B, C, D

Hint:

Fermi level moves upward for \(n\)-type doping and downward for \(p\)-type doping.

Answer 1

The Correct Option is C

Concept:
The Fermi level position in semiconductors depends on doping.

Step 1: \(p\)-type semiconductor.
In a \(p\)-type semiconductor, the Fermi level lies closer to the valence band. So, its distance from the valence band is smallest. \[ A \text{ is lowest} \]

Step 2: Intrinsic semiconductor.
In an intrinsic semiconductor, the Fermi level lies near the middle of the band gap. \[ C \text{ is above } A \]

Step 3: \(n\)-type semiconductor.
In an \(n\)-type semiconductor, the Fermi level lies closer to the conduction band. \[ B \text{ is above } C \]

Step 4: \(n\)-type degenerate semiconductor.
In a degenerate \(n\)-type semiconductor, the Fermi level may enter the conduction band. So, it has the highest Fermi level from the valence band. \[ D \text{ is highest} \] Therefore, decreasing order is: \[ D>B>C>A \] \[ \therefore \text{Correct Answer is (C)} \]