The electrical conductivity ? of a metal or semiconductor is directly related to the mobility µ of the charge carriers
The mobility of the charge carriers is the average drift velocity per unit electric field
The mobility of the carriers is related to the diffusion coefficient D by
We can use the Hall Effect to find RH=eN and hence obtain µ and <vd>.
The Fermi Energy
For an intrinsic semiconductor: EF lies at Eg/2
For a p-type semiconductor: EF > 0 (valence band edge)
For a n-type semiconductor: EF > Eg (conduction band edge)
Carrier Density Relationship
For any semiconductor, intrinsic or extrinsic, the product of the density of electrons and holes is constant at a given temperature. It does not depend on the density of doping or the position of the Fermi level
Note that for p-type semiconductors Nh>>Ne . While for n-type Ne>>Nh . For intrinsic semiconductors Nh=