Distinguish between intrinsic and extrinsic semiconductors? 

Intrinsic semiconductor

Extrinsic semiconductor

1. It is a pure semiconductor material with no impurity atoms in it. 

1. The pure semiconductors doped with tetravalent or pentavalent impurity atoms are called extrinsic semiconductors.

2. Their electrical conductivity is low.

2. Their electrical conductivity is high.

3. Number of free electrons in the conduction band is equal to the number of holes in the valence band.

3. Number of holes is never equal to the number of electrons. No. of electrons is greater in n-type semiconductor and number of holes is greater in p-type semiconductor.