distinguish between p-type and n-type semiconductor

The addition of pentavalent impurity has produced a number of conduction band electrons. The four valence electrons of pentavalent atoms form a covalent bond with the neighbourhood  germanium atoms. The fifth left over valence electrons cannot be accommodate in the valence band and travels to the conduction band.​ This is due to the predominance of free electrons over holes.​

p-type semiconductor:

The addition of the trivalent impurity has produced a large number of holes. However, there a few conduction band electrons due to thermal energy associated with room temperature. But the holes far outnumber the conduction band electrons. This is due to the predominance of hole over free electrons.
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