If an impurity is added to increase the conductivity of intrinsic semiconductors, then which of the following term is used for such a process?

Doping

The correct answer is option 2. Doping.

When an impurity is added to an intrinsic semiconductor to increase its conductivity, the process is called doping.

Doping is the process of intentionally introducing impurities into a pure semiconductor to modulate its electrical properties. There are two types of doping:

(i) n-type doping: Adding donor impurities that have more valence electrons than the semiconductor (e.g., adding phosphorus to silicon).

(ii) p-type doping: Adding acceptor impurities that have fewer valence electrons than the semiconductor (e.g., adding boron to silicon).

The purpose of doping is to increase the number of charge carriers (electrons or holes) in the semiconductor, thereby increasing its electrical conductivity.

1. Sandwiching: This term does not relate to the process of increasing conductivity through impurity addition. It might refer to constructing a layered structure of different materials but not specifically related to doping semiconductors.

3. Conducting: This term describes the property of a material to allow the flow of electric current but does not refer to the process of adding impurities to increase conductivity.

4. Insulating: This term refers to materials that do not conduct electricity well. It is the opposite of what is achieved by doping a semiconductor.

Therefore, the correct term for the process of adding impurities to increase the conductivity of intrinsic semiconductors is 2. Doping