CBSE Class 12-science Answered

If we see the lattice structure of n type semiconductors we can see that the original silicon atoms and also the doped ie , impurity atoms(pentavalent atoms)both are neutral.not ionised. but when impurity is added to the original semiconductor, then 4 out of the 5 valence electrons of the impurity atom get bonded with the 4 valence eletrons of the semiconductor.So one of the 5 outer most valence electrons of the impurity atom remains unpaired,ie, free to move. So in these n type semiconductors a number of such unpaired electrons are available for conduction.

We talk about these free electrons as majority charge carriers.