Question

List two methods that can be used to increase the conductivity of a semiconductor. Why don't these methods work on insulators?

Answer 1

The conductivity of semiconductor can be increased by these following methods:

1. By doping: The addition of impurity atoms to a pure-semi-conductor is known as doping. The doping is done to increase in the conductivity of a pure semi-conductor. It must be noted that the impurity atom is about 1 in every 10¹⁰ atoms. Doping is not possible in non-metals because there is big gap between conduction band and valance band.

2. By increasing the temperature: In case of a Semi-Conductor there is an energy gap between the valence band and the conduction band but at sufficient distance. Hench no electron has sufficient energy to cover this gap. So, when temperature of Semi-Conductor is increased, covalent bands may break up and some of the electrons may acquire sufficient energy to cover this gap thereby increase in the conductivity. Whereas in case of non-metals, with the increase in temperature the gaps are still far away. So no effect of temperature on nom-metals.