The conductivity of a semiconductor increases with increase in temperature because

Options

A. number density of free current carriers increases.
B. relaxation time increases.
C. both nomber density of carriers and relaxation time increase.
D. number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density.

Answer

D

Explanation

number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density.
As temperature is increased, large no. of charge carriers transit from valence band to conduction band. Thus, free charge carrier density is increased and so electrical conductivity of semiconductor increases considerably. This is the dominating factor for increase in electrical donductivity of semiconductors.