Question

When a small amount of Impurity atoms are added to a semiconductor, then generally its resistivity ____________.

Options

• may increase or decrease depending upon the percentage of doping

• increases

• decreases

• does not change

Answer 1

When a small amount of Impurity atoms are added to a semiconductor, then generally its resistivity decreases.

Explanation:

The conductivity of a semiconductor is given by

σ = n_eeµ_e + n_heµ_h

where n_e and n_h = number of electrons and holes per unit volume

and µ_e and µ_h = mobility of electrons and holes.

When impurity atoms are added in a semiconductor, then the concentration of holes and electrons increases. So, the conductivity Increases and hence the resistivity `(ρ = 1/σ)` of semiconductors decreases.