Conductivity of a semiconductor is given by:
o = N ue
Where, u is the mobility
The conductivity of an intrinsic semiconductor is due to its own charge carriers. At room
temperature, there are no free charge carriers. As the temperature increases, the covalent
bond breaks, thereby creating the electron hole pair increasing the conductivity. But, for
an extrinsic semiconductor, a dopant is already added, which gives charge carriers even
at room temperature. The conductivity of extrinsic semiconductors is due to impurities.
But as the temperature rises, thermal breakdown creates more electron hole pair. At
sufficiently high temperatures, the concentration of dopant becomes negligible to the
thermally generated carriers, so the conductivity of both intrinsic and extrinsic
semiconductor becomes comparable. Hence
may be greater than intrinsic conductor depending on temperature.
the conductivity of extrinsic semiconductor.