Question

a) The probability that a state is filled at the conduction band edge (E_c) is precisely equal to the probability that a state is empty at the valence band edge (E_v). Where is the Fermi level is located?

b) Where is located the Fermi energy in an insulator and metal as compared to a semiconductor?

1. Show on a schematic band diagram the amounts of carrier populations or concentrations in an intrinsic, n-type and p-type semiconductor?

Answer 1

a) because the probability of filled state of conduction band is equal to the valance band therefore it must be an intrinsic semiconductor.

And in intrinsic semiconductor the Fermi level lies at the middle of the gap between conduction band and valance band.

b) In metals the Fermi level lies inside at least one band. In insulators and semiconductors the Fermi level is inside a band gap; however, in semiconductors the bands are near enough to the Fermi level to be thermally populated with electrons or holes.

Schematic diagram of carrier concentration