n-type semiconductor at 0k temperature. where do you expect the fermi level to be
Answers
An n-type semiconductor at 0k temperature.
Fermi energy will be near to conduction band.
Fermi enegy is defined as highest occupied energy level at absolute 0k.
A n-type semi conductor is formed when petavalent impurity is added to the intrinsic germanium or silicon conductor.
Due to the adding of pentavalent impurity, the free electron concentration is just above the intrinsic carrier concentration. The hole concentration also falls below the intrinsic carrier concentration because the rate of recombination of electrons with holes is increased due to excess electrons.
Due to the added pentavalent impurity, an allowable energy level will be produced in the forbidden energy gap level. This level will correspond to the loosely bound valence electrons of the donor pentavalent impurity.
The newly formed donor level is found just below the conduction band.
We are asked to determine the position of the Fermi level.
At room temperature, all the donors are ionized due to the thermal agitation, and excess electrons have jumped to conduction band. At absolute zero temperature , the free electrons will be found in the donor level.
The Fermi energy is the maximum energy that can be occupied by the electrons at absolute zero.
Hence, from above, it is obvious that the Fermi energy will be found just below the conduction band.