Identify the correct statements among the following.
A. The resistance of the intrinsic semiconductor decreases with rise in temperature.
B. Doping pure Si with trivalent impurities gives p-type semiconductor.
C. The majority carriers in n-type semiconductor are holes.
D. A p-n junction can act as a semiconductor diode.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, B and D only
Doping with a pentavalent impurity gives an n-type semiconductor (majority carriers electrons), doping with a trivalent impurity gives a p-type semiconductor (majority carriers holes).
(A) The resistance of the intrinsic semiconductor decreases with rise in temperature. — Correct. Heating breaks covalent bonds and creates more electron-hole pairs, so the resistance falls.
(B) Doping pure Si with trivalent impurities gives p-type semiconductor. — Correct. A trivalent atom (B, Al, In) has one electron too few to complete four bonds, and the vacancy acts as a hole.
(C) The majority carriers in n-type semiconductor are holes. — Incorrect. In n-type material the majority carriers are electrons; holes are the minority carriers.
(D) A p-n junction can act as a semiconductor diode. — Correct. A p-n junction conducts easily in forward bias and hardly at all in reverse bias, which is the action of a diode.
NCERT (2026-27):
Temperature Dependence of Resistivity – “… For insulators and semiconductors, however, n increases with temperature. This increase more than compensates any decrease in \( \tau \) in Eq.(3.23) so that for such materials, ρ decreases with temperature.”
Extrinsic Semiconductor – “… Hence in an extrinsic semiconductor doped with pentavalent impurity, electrons become the majority carriers and holes the minority carriers. These semiconductors are, therefore, known as n-type semiconductors.”
Extrinsic Semiconductor – “… Therefore, extrinsic semiconductors doped with trivalent impurity are called p-type semiconductors.”
Semiconductor Diode – “A semiconductor diode [Fig. 14.12(a)] is basically a p-n junction with metallic contacts provided at the ends for the application of an external voltage.”