Question

Assertion (A): We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of an n-type semiconductor.
Reason (R): In a p-type semiconductor, \( n_e \gg n_h \) while in an n-type semiconductor \( n_h \gg n_e \).

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false and Reason (R) is also false.

Hint:

A p-n junction diode can be formed by joining p-type and n-type semiconductors. The electron and hole concentrations in each type of semiconductor are different.

Answer 1

The Correct Option is D

Assertion and Reason Analysis for P-N Junction

Assertion (A): 

We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of an n-type semiconductor.

Reason (R):

In a p-type semiconductor, \( n_e \gg n_h \) while in an n-type semiconductor \( n_h \gg n_e \).

Explanation:

Let's break down the assertion and reason:

• In a p-type semiconductor, the majority charge carriers are holes (\( n_h \)), and the minority carriers are electrons (\( n_e \)), so \( n_e \ll n_h \).
• In an n-type semiconductor, the majority charge carriers are electrons (\( n_e \)), and the minority carriers are holes (\( n_h \)), so \( n_h \ll n_e \).
• When a p-type and n-type material are physically joined, a p-n junction is formed, but the assertion states that this junction cannot be formed by physically joining the materials, which is incorrect. A p-n junction is formed by the diffusion of electrons and holes at the interface between the two materials, creating a depletion region where recombination occurs.
• The reason (\( n_e \gg n_h \) in n-type and \( n_h \gg n_e \) in p-type) is correct in terms of charge carrier concentrations in p-type and n-type semiconductors but does not explain the failure to form a p-n junction.

Conclusion:

Therefore, while both the assertion and the reason are true, the reason does not correctly explain the assertion. The assertion is false because a p-n junction can indeed be formed by physically joining a p-type and an n-type semiconductor.

Correct Answer:

Option 2: Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).