Charge carrier density

Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units, it is measured in m−3. As with any density, in principle it can depend on position. However, usually carrier concentration is given as a single number, and represents the average carrier density over the whole material.

Charge carrier densities involve equations concerning the electrical conductivity, related phenomena like the thermal conductivity, and chemicals bonds like covalent bond.

Calculation

The carrier density is usually obtained theoretically by integrating the density of states over the energy range of charge carriers in the material (e.g. integrating over the conduction band for electrons, integrating over the valence band for holes).

If the total number of charge carriers is known, the carrier density can be found by simply dividing by the volume. To show this mathematically, charge carrier density is a particle density, so integrating it over a volume

V

{\displaystyle V}

gives the number of charge carriers

N

{\displaystyle N}

in that volume

N

=

∫

V

n

(

r

)

d

V

.

{\displaystyle N=\int _{V}n(\mathbf {r} )\,dV.}

where

n

(

r

)

{\displaystyle n(\mathbf {r} )}

is the position-dependent charge carrier density.