Question: For extrinsic semiconductors: when doping level is increased;
Fermi-level of $p$ and $n$-type semiconductors will not be affected.
Fermi-level of p-type semiconductors will go downward and Fermi-level of n-type semiconductor will go upward.
Fermi-level of both p-type and n-type semiconductors will go upward for $T>T_{F} K$ and downward for $\mathrm{T}<\mathrm{T}_{\mathrm{F}} \mathrm{K}$, where $\mathrm{T}_{\mathrm{F}}$ is $\mathrm{Fermi}$ temperature.
Fermi-level of p-type semiconductor will go upward and Fermi-level of n-type semiconductors will go downward. }
Correct Option: , 2
Solution:
(2)
In n-type semiconductor pentavalent impurity is added. Each pentavalent impurity donates a free electron. So the Fermi-level of n-type semiconductor will go upward.
$\&$ In p-type semiconductor trivalent impurity is added. Each trivalent impurity creates a hole in the valence band. So the Fermi-level of p-type semiconductor will go downward.