Current in an Intrinsic semiconductor is equal to 

Intrinsic semiconductor:

• It is a crystal having all atoms of the same nature i.e. extremely pure semiconductor is called an intrinsic semiconductor.

          Ex: pure silicon, germanium.

• At room temperature (300 Kelvin), the electrons in the valence band are moved to the conduction band. When an electron leaves the valence band it creates a vacancy known as a hole. A hole attracts electrons as it is positively charged.
• In intrinsic semiconductor number of free electrons is equal to the number of holes. i.e. ne = nh
• Since there is an equal number of both the electrons and holes in an intrinsic semiconductor, the current contribution will be equal from both the charge carriers.
• The total current passing through intrinsic semiconductors is given by:

           I = Ie + Ih

          I_e = Electron Current

          I_h = Hole current

This is explained with the help of the following diagram:

For an extrinsic semiconductor the current will be because of majority carriers:

• For an n-type extrinsic semiconductor, the current will be because of the majority carrier electrons (I_e only)
• For a p-type extrinsic semiconductor, the current will be because of the majority carrier holes (I_h only)