The extrinsic n Type Semiconductor is formed, when a pentavalent impurity is added to a pure silicon or germanium atom in small amount and as result large number of electrons are created in it.
A pentavalent impurity like phosphorous, arsenic, antimony, antimony, bismuth, lithium
Antimony have having five valence electrons but, silicon or germanium need only four valance electrons. it forms four covalent bonds. But, one electron will be left excess in Antimony Thus, each Antimony atom leaves one excess electron in the germanium crystal.
As an extremely small amount of Antimony impurity has a large number of atoms, therefore, it provides millions of electrons in the semiconductor.
A pentavalent impurity like phosphorous, arsenic, antimony, antimony, bismuth, lithium
Antimony have having five valence electrons but, silicon or germanium need only four valance electrons. it forms four covalent bonds. But, one electron will be left excess in Antimony Thus, each Antimony atom leaves one excess electron in the germanium crystal.
As an extremely small amount of Antimony impurity has a large number of atoms, therefore, it provides millions of electrons in the semiconductor.
Energy band diagram :
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