Charge neutrality condition for a p type semiconductor
Answers
Well there is no reason for the doped semi-conductor to be charged; either positive, or negative. Every single atom in the semiconductor came with its full complement of electrons, so the whole thing has no charge surplus or deficiency.
For example, if the semiconductor is say Silicon, every Si atom has 4 valence electrons. If you dope it P type with boron, which is a group III atom, each B atom has just 3 valence electrons. If you dope it N type with phosphorus, that is a group V element so each atom comes with 5 valence electrons. But either type of dopant atom is still charge neutral.
If a B atom replaces a Si atom in the crystal, one of the Si valence electrons has no mate from the Boron, and if a P atom replaces a Si atom, then the P atom has one electron with no mate from a Si atom; but it is always electrically neutral (the whole crystal)