For extrinsic semiconductors; when doping level is increased;

Fermi-level of p-type semiconductors will go downward and Fermi-level of n-type semiconductor will go upward.

Fermi-level of both p-type and n-type semiconductors will go upward for T > TFK and downward for T < TFK, where TF is Fermi temperature.

Fermi-level of p-type semiconductor will go upward and Fermi-level of n-type semiconductors will go downward

Fermi-level of p and n-type semiconductors will not be affected.

Electronic Devices PYQ — JEE Main 2021 · 25 Feb · Shift 2 · Q64 with Solution

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Correct answer: D

Concept of Fermi level in extrinsic semiconductors

The Fermi level indicates the energy level at which the probability of occupation is $\tfrac12$ .
- In an n-type semiconductor, donor impurities add extra electrons, so the Fermi level shifts towards the conduction band.
- In a p-type semiconductor, acceptor impurities create holes, so the Fermi level shifts towards the valence band.
Effect of increasing doping level

When doping is increased:
- For n-type, more donor atoms are added $\Rightarrow$ electron concentration increases $\Rightarrow$ Fermi level moves closer to the conduction band edge $E_C$ , i.e. it moves upward.
- For p-type, more acceptor atoms are added $\Rightarrow$ hole concentration increases $\Rightarrow$ Fermi level moves closer to the valence band edge $E_V$ , i.e. it moves downward.
Check each option

A: Says both p-type and n-type Fermi levels move upward/downward depending on temperature. This is not the standard effect of increasing doping level. Incorrect.

B: Says p-type goes upward and n-type goes downward. This is opposite to the actual behavior. Incorrect.

C: Says no effect. But doping definitely changes the Fermi level. Incorrect.

D: Says p-type goes downward and n-type goes upward. This matches the correct physical behavior. Correct.
Final answer

Therefore, the correct option is: $\boxed{D}$

View written solutionFree

Correct answer: D

Concept of Fermi level in extrinsic semiconductors

The Fermi level indicates the energy level at which the probability of occupation is $\tfrac12$ .
- In an n-type semiconductor, donor impurities add extra electrons, so the Fermi level shifts towards the conduction band.
- In a p-type semiconductor, acceptor impurities create holes, so the Fermi level shifts towards the valence band.
Effect of increasing doping level

When doping is increased:
- For n-type, more donor atoms are added $\Rightarrow$ electron concentration increases $\Rightarrow$ Fermi level moves closer to the conduction band edge $E_C$ , i.e. it moves upward.
- For p-type, more acceptor atoms are added $\Rightarrow$ hole concentration increases $\Rightarrow$ Fermi level moves closer to the valence band edge $E_V$ , i.e. it moves downward.
Check each option

A: Says both p-type and n-type Fermi levels move upward/downward depending on temperature. This is not the standard effect of increasing doping level. Incorrect.

B: Says p-type goes upward and n-type goes downward. This is opposite to the actual behavior. Incorrect.

C: Says no effect. But doping definitely changes the Fermi level. Incorrect.

D: Says p-type goes downward and n-type goes upward. This matches the correct physical behavior. Correct.
Final answer

Therefore, the correct option is: $\boxed{D}$