Test: Donor & Acceptor Impurities - Electrical Engineering (EE) MCQ

At room temperature, the donors have donated their electrons to the conduction band.

AT 0 K, all the donors and acceptors are in their lowest energy levels.

Freeze out means none of the electrons are transmitted to the conduction band.

The density of the electrons is equal to the electrons present in the substrate minus the number of donors present.

For n-type semiconductors, the donor band is just above the intrinsic Fermi level.

At T=0 K, the tem exp(-∞)=0 in the expression of

Thus, EF>ED
So, only conduction band lies above the Fermi energy level.

At T=0 K, the Fermi level of n band lies between the midway of Ec and Ed as intrinsic Fermi level always lies between the Ec and Ev.

At T=0 K, the tem exp(-∞)=0 in the expression of

So, only valence band lies below the Fermi energy level of the acceptors.

For n-type semiconductors, the donor energy level is always greater than the Fermi level energy.

The given figure has B band below the intrinsic Fermi level, so that would be acceptor energy band and will be a p-type semiconductor.