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

To determine the truth of the assertion and the reason provided, we need to evaluate them based on semiconductor physics. 

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.

Explanation: A p-n junction diode is formed by doping a single crystal of semiconductor material such that one side becomes p-type and the other becomes n-type. This ensures a continuous lattice structure and a seamless junction. Simply joining two slabs physically would introduce interface defects and create a lack of a continuous crystal lattice, leading to high recombination of charge carriers at the interface and ineffective diode operation. Thus, the assertion is true under practical conditions required for effective diode function, but a simple physical joining does not form a functional diode due to discontinuities.

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

Explanation: This reason is technically incorrect. In a p-type semiconductor, the majority carriers are holes (\( n_h \)), and in an n-type semiconductor, the majority carriers are electrons (\( n_e \)). Therefore, \( n_h \gg n_e \) is true for p-type, and \( n_e \gg n_h \) is true for n-type, which is the opposite of the given reason.

The correct answer: Assertion (A) is false and Reason (R) is also false.