1.

Experiments show the electrical conductivity of semiconductors to rise drastically with temperature. Assuming that it is possible to calculate the probability of electron transition from the valence to the conduction band using the barometric distribution, derive the formula for the temperature dependence of a semiconductor's conductivity.

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Solution :The electric CONDUCTIVITY of electronic (N-type) semiconductors is PROPORTIONAL to the number of electrons in the conduction BAND. In the assumption that the transition probability of the electron from the valence to the conduction band can be computed with the aid of a barometric distribution, we obtain `n=Ae^(-Deltaepsi//kT)`, where `Deltaepsi` is the forbidden band width. Hence we obtain for the electric conductivity
`GAMMA=(e^(2)lamdaA)/(pF)e^(-Deltaepsi//kT)=Re^(-Deltaepsi//kT)`
where B is a constant characteristic of the material (at a SPECIFIED temperature).


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