Comment on the conductivity of extrinsic semiconductor

The conductivity of n-type and p-type semiconductors is given below: 

(i) n-type conductivity: The current conduction in an n-type semiconductor is predominantly by free electrons i.e. negative charges and is called n-type or electron type conductivity. When p. d is applied across the n-type semiconductor, the free electrons in the crystal will be directed towards the positive terminal, constituting electric current. As the current flow through the crystal is by free electrons which are carriers of negative charge, therefore, this type of conductivity is called negative or n-type conductivity.

 (ii) p-type conductivity: The current conduction in p-type semiconductor is predominantly by holes i.e. positive charges and is called p-type or hole-type conductivity. When p. d is applied to the p-type semiconductor, the holes are shifted from one co-valet bond to another. As the holes are positively charged, therefore, they are directed towards the negative terminal, constituting what is known as hole current.