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Conductivity of Semiconductor

In intrinsic semiconductors, ne = nh. Both electron and holes contributed in current conduction.
When some potential difference is applied across a piece of intrinsic semiconductor current flows in it due to both electron and holes, i.e., i = ie + ih 106992.png
Fig. 8
As we know 106998.png. Hence conductivity of semiconductor
σ = e[neμe + nhμh]; where ve = drift velocity of electron, vh = drift velocity of holes, E = Applied electric field, μe = ve/E = mobility of electron and μh = vh/E = mobility of holes.
The motion of electrons in the conduction band and the motion of holes in the valence band under the action of electric field is shown in Fig. 9.
Fig. 9
At absolute zero temperature (0 K), the conduction band of semiconductor is completely empty, i.e., σ = 0. Hence, the semiconductor behaves as an insulator.

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