Charge carrier density denotes the number of charge carriers per volume. It is measured in m−3. As any density it can depend on position. It should not be confused with the charge density, which is the number of charges per volume at a given energy.
The carrier density is obtained by integrating the charge density over the energy that the charges are allowed to have.
Charge carrier density is a particle density, so integrating it over a volume
where
If the density does not depend on position and is instead equal to a constant
Charge carrier densities involve equations concerning the electrical conductivity and related phenomena like the thermal conductivity.
Measurement
The density of charge carriers can be determined in many cases using the Hall effect, the voltage of which depends inversely on the density.
Such measurements show that the density for silver is around 1.070·1028 m−3 or around 17,763 moles m−3.