Doped or Extrinsic semiconductors:

N-Type:

Group IV elements like Si, Ge, etc. is doped with group V elements like P, N, As, Sb, etc.

If an atom with five valence electrons is added to the semiconductor four of the five electrons will participate in the covalent bonds while the fifth electron is left over. This extra electron is almost free and has an energy level just below the conduction band. Such a pentavalent atom is called a donor atom. In N type of semiconductor electrons are majority charge carriers and holes are minority charge carriers.

P-Type:

If the intrinsic semiconductor is doped with atoms of a trivalent element such as Al, In, B etc., the three electrons enter into covalent bonds with neighbouring atoms, leaving a vacant space, or hole, in the fourth bond. The energy levels of such vacant spaces lie just above the valence band.

In P type semiconductors hole are majority charge carries whereas electrons are minority charge carriers.