The electron and hole concentrations in intrinsic semiconductors

The force exerted on an electron by an electric field, E, is given by  

The mobility of the electrons, p, is defined as the drift velocity gained per unit electric field that is, 

Comparing this with Equation (S4.14) makes it apparent that  

This is sometimes called the drift mobility, to distinguish it from mobility measured via the HaU effect. The conductivity and the mobility are then related by substituting t of Equation (S4.16) into Equation (S4.15) to give  

If the length of the conductor is L, the electric field can be replaced by V/L, where V is the voltage applied to the conductor (see Section S4.6) to give  

---