Since
the electron concentration is described as
,
(1)
the following relation is obtained:
(2)
On
the other hand, since
,
(3)
the following relation is obtained:
.
(4)
Therefore,
substituting Eq. (4) to Eq. (2) gives
.
(5)
Since
,
(6)
we
obtain the following relationship:
.
(7)