Semiconductors are the materials whose conductivity and resistivity lie in between metals and insulators

When  temperature higher than zero degree Kelvin some of the electrons are excited from valence band to conduction band creating an equal number of holes in the valence band

Silicon and germanium are the good examples of semiconductors

Types of semiconductors

1) Intrinsic semiconductor

The pure semiconductor is called intrinsic semiconductor in intrinsic semiconductors conductivity is due to holes and electrons both which increase with rise of temperature electrons move in antiparallel direction to the external field

2)Extrinsic semiconductors

When is small quantity of impurity is mixed in a pure aur intrinsic semiconductor the conductivity of semiconductor increases sach and impure semiconductor is called extrinsic semiconductor

There are two types of extrinsic semiconductors

N type

N type semiconductor pentavalent impurity are used as a dopant with silicon or germanium such a impurity called donor impurity because each dopant atom provides one free electron

P type

To prepare a p type semiconductor and trivalent impurity are used as a dopant with silicone or Germany I'm such an impurity is called as chapter impurities as he impurity atoms wants to accept an electron from the crystal lattice in p-type semiconductors each loop and atom provides a hole