The number of free electrons and holes in an intrinsic semiconductor increase when the temperature
Right Answer is:
At room temperature (T> 0 K), the valence electron acquires a sufficient amount of thermal energy. As a result, breakage of covalent bonds takes place releasing free electrons. These free electrons create a vacancy in their initial position in the crystal.
These free electrons, due to acquiring sufficient thermal energy, cross the energy gap and enter into the conduction band from the valence band and occupy the energy levels in the conduction band.
In the intrinsic semiconductor, the electrons and holes are generated in pairs and at any given temperature the volume concentration of electrons is equal to that of holes.
With the rise in temperature, more and more electron-hole pairs are formed and more charge carriers are available for conduction. Thus the conductivity of intrinsic semiconductors increases with the increase in temperature (and hence the resistivity decreases with an increase in temperature).