Doping a semiconductor
Doping increases the conductivity of a semiconductor. A doped semiconductor is called an extrinsic semiconductor. When an intrinsic semiconductor is doped with pentvalent (donor) atoms (i.e. Arsenic atoms donates one free electron to the crystal), it has more free electrons than holes.
---> N-type semiconductor
When an intrinsic semiconductor is doped with trivalent (acceptor) atoms (i.e. Baron atoms in the crystal will create a hole which is capable of accepting an electron), it has more holes than free electrons.
---> P-type semiconductor
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