# Carrier density

In physics, the charge carrier density is the number of charge carriers that are present in a certain volume ( unit m −3 ). It is an important parameter for describing electrical conductivity and all associated processes. It should not be confused with the charge density , which indicates the amount of charge per volume (in coulomb · m −3 ). ${\ displaystyle n}$

The carrier density is a particle density , i.e. i.e., like any density , it can be location-dependent:

${\ displaystyle n = f (\ mathbf {r}) \ neq const.}$

and the integration over a volume provides the number of charge carriers in this volume: ${\ displaystyle V}$${\ displaystyle N}$

${\ displaystyle N = \ int _ {V} n (\ mathbf {r}) \, \ mathrm {d} V \ Leftrightarrow n = {\ frac {dN} {dV}}.}$

Is the charge carrier density independent of location :

${\ displaystyle n = const. = n_ {0} \ neq f (\ mathbf {r}),}$

the above formula is simplified to

${\ displaystyle \ Rightarrow N = n_ {0} \ cdot V \ Leftrightarrow n_ {0} = {\ frac {N} {V}}.}$