GENERAL KNOWLEDGE

Detailed explanation-1: -Answer: Option C Solution: Suitable impurities are added to a semiconductor depending on its use. This is done in order to increase its electrical conductivity.

Detailed explanation-2: -The process of adding impurities to the semiconductor is called doping.

Detailed explanation-3: -In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor.

Detailed explanation-4: -By doping impurities into semiconductors, depending on the valence e− of impurities, either holes or free electrons are formed. These electrons and holes act as carriers for electricity. So conductivity of semiconductor increases.

Detailed explanation-5: -The conductivity of a semiconductor is given by the expression, =nee+peh, where e is the electron mobility, h is the hole mobility, and e is the elementary charge. Generally the mobilities decrease with increasing temperature and doping concentration.