In a semiconductor, acceptor impurity is:
A. Antimony
B. Indium
C. Phosphorous
D. Arsenic

Hint: Acceptor impurities must be trivalent to accept an electron from semiconductor. Find the number of valence electrons in Antimony, Indium, Phosphorus and Arsenic to determine the acceptor impurity.
Complete step by step answer:
A typical intrinsic semiconductor has 4 valence electrons. It is doped with impurities to increase its conductivity. Doping with pentavalent atoms will lead to an extra electron. It is then called n-type semiconductor with majority carriers as electrons and minority carriers as holes. The dopant is known as a donor in this case. In contrast, doping with a trivalent electron will lead to an extra hole. It is then called a p-type semiconductor with majority carriers as holes and minority carriers as electrons. The dopant is known as an acceptor in this case.
Antimony, Phosphorus and Arsenic have 5 valence electrons hence they act as donor impurity.
Indium has 3 valence electrons and hence it is an acceptor impurity.

So, the correct answer is “Option B”.

Additional Information:
Doped semiconductors are widely used in the construction of electronic devices. A junction diode consists of n-type and p-type semiconductors welded together at a junction. Bipolar junction transistors use two n-type layers with a p-type layer in between or vice-versa.
The other devices utilizing doped extrinsic semiconductors are Field effect transistors, laser, thyristors, light emitting diodes, photodetectors and solar cells.
Note:
Doping changes an intrinsic semiconductor to an extrinsic semiconductor and enhances its electrical, optical and other structural properties.
They are used for current and power application purposes.