Discuss electrical conductivity of semiconductors. Derive expression for conductivity in terms of impurity ionization energy. Give a plot to discuss 'Theoretical temperature dependence of the electrical conductivity of an impurity semiconductor'.

A semiconductor is a material whose valence band and conduction band are partially filled with a small forbidden gap between them. It acts as a conductor at high temperature and as an insulator at low temperature. The temperature coefficient of resistance is negative (conductivity increases with ...