Question

In N-Type semiconductor, the Fermi Level

• A. Is lower than the centre of energy gap
• B. Is at the centre of energy gap
• C. Is higher than the centre of energy gap
• D. Does not exist

Hint:

In an N-type semiconductor, the Fermi level shifts closer to the conduction band due to the presence of excess electrons from donor impurities.

Answer 1

The Correct Option is C

The Fermi level (\( E_F \)) represents the energy level at which the probability of finding an electron is 50% at thermal equilibrium.
Step 1: Understanding the Fermi Level in N-Type Semiconductors - In intrinsic semiconductors, the Fermi level lies at the centre of the energy gap. - In N-type semiconductors, donor impurities introduce extra electrons, shifting the Fermi level closer to the conduction band. - The presence of excess electrons raises the probability of electron occupancy in higher energy states.


Step 2: Evaluating the Options - Option (A) - Incorrect: The Fermi level in an N-type semiconductor is higher, not lower.
- Option (B) - Incorrect: The Fermi level is not at the centre in an N-type semiconductor.
- Option (C) - Correct: The Fermi level is closer to the conduction band, making it higher than the centre of the energy gap.
- Option (D) - Incorrect: The Fermi level always exists as a fundamental property.


Step 3: Conclusion Since the Fermi level in an N-type semiconductor is higher than the centre of the energy gap, the correct answer is option (C).