consider an 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.
Before coming into any conclusion, first we have to understand the n- type semiconductor.
A n- type semi conductor is formed when a pentavalent impurity is added to intrinsic Ge or Si. The impurities added to intrinsic Ge or Si is called donor impurity.
When donor impurities are added, an allowable energy level corresponding to the loosely bound valence electrons is introduced in the forbidden energy gap level .This level is just below the conduction band. This level is called as the donor level.
We are asked to determine the position of Fermi level.
In n- type semiconductor, all the donors are ionized because all their extra electrons are excited to the conduction band at room temperature. At absolute zero temperature, the extra electrons are present at the donor level.
Hence, the Fermi level will lie just below the conduction band of the metal.