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

Analysis of Assertion and Reason Regarding P-N Junction Formation

Assertion (A):

It is not possible to create a p-n junction diode by physically joining a slab of p-type semiconductor with a slab of n-type semiconductor.

Reason (R):

In a p-type semiconductor, the concentration of electrons (\( n_e \)) is significantly less than the concentration of holes (\( n_h \)), i.e., \( n_e \ll n_h \), whereas in an n-type semiconductor, the concentration of holes (\( n_h \)) is significantly less than the concentration of electrons (\( n_e \)), i.e., \( n_h \ll n_e \).

Explanation:

Let's analyze the assertion and the reason:

• A p-type semiconductor is characterized by a higher concentration of holes (majority carriers) compared to electrons (minority carriers), denoted as \( n_h \gg n_e \).
• Conversely, an n-type semiconductor has a higher concentration of electrons (majority carriers) than holes (minority carriers), expressed as \( n_e \gg n_h \).
• The assertion that a p-n junction cannot be formed by physically joining p-type and n-type materials is incorrect. The process of forming a p-n junction involves the diffusion of majority carriers (holes from the p-side and electrons from the n-side) across the interface, leading to the creation of a depletion region where recombination occurs.
• The provided reason correctly states the relative concentrations of charge carriers in p-type and n-type semiconductors. However, these concentration differences do not preclude the formation of a p-n junction; rather, they are fundamental to its formation mechanism.

Conclusion:

While both the assertion and the reason contain true statements about semiconductor properties, the reason does not validate the assertion. The assertion itself is factually incorrect, as a p-n junction is indeed formed by the physical interface between p-type and n-type semiconductors.

Correct Answer:

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