
Principles of Analog Electronics
86
How many of these
10
atoms for
release one electron as a carrier at
room and other temperatures? The volumetric density of free electrons, that is,
promoted from the valence to the conduction band, is called intrinsic carrier
concentration (per unit volume)
3
m
i
−
, and depends on both material and
temperature, according to the equation
23 6
nBTe cm
i
E
kT
G
=
−
−
where
➜
: Energy gap eV
➜ k: Boltzmann constant
8.62 10 /
5
eV K
−
(Ludwig Edward Boltzmann,
Austrian physicist, 1844–1906)
➜ T a bsolute temperat ure
➜ B: a value function of the material and the temperature (for silicon