Q.
If ne is number density of electrons in conduction band and nh is number density of holes in valence band, then for an extrinsic semiconductor at room temperature, (ni= number density of intrinsic pairs)
(At room temperature, the density of holes in the valance band is predominantly due to impurity in the extrinsic semiconductor. The electron and hole concentration in a semiconductor in thermal equilibrium is given by nenh=ni2