Question

Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C), and (D) as given below.
Assertion (A): The impurities in p-type Si are not pentavalent atoms.
Reason (R): The hole density in the valence band in a p-type semiconductor is almost equal to the acceptor density.

• 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. Both Assertion (A) and Reason (R) are false.

Hint:

In semiconductors, p-type doping involves adding trivalent elements (like boron), while n-type doping involves pentavalent elements (like phosphorus). The hole density in p-type semiconductors is nearly equal to the acceptor density.

Answer 1

The Correct Option is B

- Assertion (A): In p-type semiconductors, the primary charge carriers are holes. These holes are generated by doping with trivalent elements (e.g., boron), not pentavalent elements. Pentavalent elements (e.g., phosphorus) are used to create n-type semiconductors by supplying excess electrons. Therefore, the statement that impurities in p-type Si are not pentavalent atoms is accurate.

- Reason (R): In p-type semiconductors, acceptor atoms (e.g., boron) create holes in the valence band. The number of holes produced is approximately equal to the number of acceptor atoms, indicating that the hole density closely matches the acceptor density. Consequently, Reason (R) is also true.

However, Reason (R) does not directly explain Assertion (A). The equality of hole density to acceptor density in p-type semiconductors is independent of whether the dopant is pentavalent or trivalent. The assertion addresses the type of dopant used for p-type materials (trivalent), while the reason describes a characteristic of hole concentration in these materials.

Therefore, the correct selection is option (B): Both Assertion (A) and Reason (R) are true, but Reason (R) does not correctly explain Assertion (A).