Intrinsic semiconductor is Silicon with (4 valence electron)
If doped with p type (3 valence electron) it will have an extra hole and changes the band gap such that the charge carrier(holes)can easily cross over to the valence band(when electrons jump up easily when a small voltage is applied.The holes moving in the valence band is the only way the conduction takes place hence p type.
If doped with n type (5 valence electron) it will have an extra electron and changes the band gap such that the charge carrier(electron) can easily cross over to the conduction band when a small voltage is applied .The electrons moving in the conduction band is the only way the conduction takes place hence n type.
pic taken from hyperphysics
