Question

The width of forbidden gap in silicon crystal is
1.1eV. When the crystal is converted into n-type
semiconductor, then the distance of fermi energy
level from conduction band is
1) equal to 0.55eV 2) equal to 1.1eV
3) less than 0.55eV 4) greater than 0.55eV

Answer 1

Fermi level in intrinsic semiconductor lies in middle of the energy forbidden gap .

                       In case of silicon it is at .55eV ,but when it doped with pentavalent

           n-type semiconductor fermi energy level  rises up just below conduction 

                       band  so that electron can easily  move to conduction band . 

                       So energy gap in fermi level and conduction band will be less than .55eV

                        Option 3 is correct .