Read the following statements and identify the correct statements.
(A) In a semiconductor doped with trivalent impurity, the holes are the majority carriers and electrons are minority carriers.
(B) In pure semiconductors, the number of free electrons is equal to the number of holes.
(C) In a semiconductor doped with pentavalent impurity, electrons become the majority carriers and holes the minority carriers.
(D) Important electronic devices can be developed using intrinsic semiconductors.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B) and (C) only
(A) In a semiconductor doped with trivalent impurity, the holes are the majority carriers and electrons are minority carriers. — Correct. A trivalent atom has one electron too few for the four bonds, which creates a hole, so the material is p-type.
(B) In pure semiconductors, the number of free electrons is equal to the number of holes. — Correct. In an intrinsic semiconductor each electron that breaks free leaves one hole behind, so \( n_{e} = n_{h} \).
(C) In a semiconductor doped with pentavalent impurity, electrons become the majority carriers and holes the minority carriers. — Correct. A pentavalent atom donates one extra electron, so the material is n-type.
(D) Important electronic devices can be developed using intrinsic semiconductors. — Incorrect. The useful devices, such as the diode and the transistor, are made from doped (extrinsic) semiconductors with a p-n junction; a pure semiconductor has too few carriers for this.
NCERT (2026-27):
Intrinsic Semiconductor – “… In intrinsic semiconductors, the number of free electrons, ne is equal to the number of holes, nh.”
Extrinsic Semiconductor – “The conductivity of an intrinsic semiconductor depends on its temperature, but at room temperature its conductivity is very low. As such, no important electronic devices can be developed using these semiconductors.”
n-type Semiconductor – “… Hence in an extrinsic semiconductor doped with pentavalent impurity, electrons become the majority carriers and holes the minority carriers.”
p-type Semiconductor – “… Thus, for such a material, the holes are the majority carriers and electrons are minority carriers. Therefore, extrinsic semiconductors doped with trivalent impurity are called p-type semiconductors.”