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B Fermi Energy Dependence on Free Charge Carrier Concentration
The number of allowed k-values per unit volume of k-space in a piece of
material with volume V is .
The number of energy levels in the
Fermi sphere, considering two spin values for each k-value, is
Thus if there are N electrons in a volume V the concentration is
n = N/V, which leads to
In the case of semiconductors the band gap has to be taken into account.
Using the Boltzmann approximation to the
Fermi distribution the carrier
concentrations in the conduction and valence band are
Noting that for the intrinsic case,
EF = EF,i,
nc=pv=ni the
concentrations may be written as
And with the net carrier concentration n=nc-pv one derives
Christoph Wasshuber