Intrinsic Semiconductor

Description:

Intrinsic semiconductor is a crystal having all atoms of same nature i.e. extremely pure semiconductor is called intrinsic semiconductor.

E.g.: pure silicon, germanium.

Si atom has four valence electrons. Every Si atom in the crystal shares its four valence electrons with its four neighbours. Thus, all atoms complete their octet and attain stability. At initial temperature i.e. absolute zero temperature (0 Kelvin), the valence band is completely filled with electrons and the conduction band is empty.

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 Hole. A hole attracts electrons as it is positively charged.

In intrinsic semiconductor number of free electrons is equal to number of holes.

n_e = n_h

When current is passed through a material containing free electrons, the current is conducted and it is known as current due to electrons (I_e).

Similarly, when a current is passed through a material it can be conducted due to holes and it is known as current due to holes (I_h).

The total current passing through intrinsic semiconductors is given by -

I = I_e + I_h