Question

In case of semiconductors {germanium }why does conductivity increase with increase in temperature ??

Answer 1

Electrical conductivity of the semiconductors increases with increase in the temperature as more and more charge carrier are generated as they acquire thermal energies sufficient to cross the band gap; from valence band to conduction band. After crossing the band gap they reach the conduction band and thus contribute to the conduction process, increasing the conductivity of the material as a whole.