Question

Derive an expression for conductivity for intrinsic semiconductor

Answer 1

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Answer 2

The expression for conductivity for an intrinsic semiconductor is  σi = ni ( un + un )q

Conductivity of a semiconductor = (nun + pup) q

If the semiconductor is intrinsic, then at any time the concentration of free electrons n and holes p is the same and given by ni called intrinsic concentration.

Thus, for an intrinsic semiconductor - ni = n = p

Because of thermal generation the intrinsic concentration depends on the temperature. As temperature increases, it generates more number of pairs of electrons holes. Hence, the concentration of the free electrons n and the concentration of the hole p increases by the same amount. Therefore, the inherent concentration of the carrier does not increase.

Conductivity of intrinsic semiconductor is denoted as -

σi = ni ( un + un )q