How may the conductivity of an intrinsic semiconductor be increased?

Answer
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Hint: Conductivity of intrinsic conductors can be increased by increasing the temperature as the increase in temperature pushes a greater proportion of electrons from the valence band to the conduction band which increases the conductivity.

Complete answer:
In this question we have asked how to increase the conductivity of an intrinsic semiconductor. An intrinsic semiconductor also called an undoped semiconductor or i-type semiconductor is a pure semiconductor without any significant dopant species present. The number of charge carriers is therefore determined by the properties of the material itself instead of the number of impurities. Its electrical conductivity falls between that of a conductor and an insulator.
In order for a substance to conduct electricity, its valence electron must cross the bandgap, which is the energy gap between the valence band and conduction band. When we increase the temperature, more electrons get the energy to jump from the Conduction band to the valence band and thereby increases the conductivity of the semiconductor. The conductivity of intrinsic semiconductors can also be increased by adding a suitable impurity. This process is called Doping. The impurities can be of two types- electron-rich or electron-deficient.


Note: When we add impurities in an intrinsic semiconductor, two types of semiconductor are formed. If the impurities are electron-rich then it will lead to the formation of n-type (S) semiconductors and if the impurities are electron deficit then it will lead to the formation of p-type semiconductor (T) Silicon and germanium are examples of i-type semiconductors.