# Does doping affect the number of band states?

Does doping a semiconductor with acceptor impurities affect the number of states in the valence and conduction bands? How about doping with donor impurities?

It seems to me, that in the former case the answer should be yes, adding acceptors should decrease the number of band states while in the latter I think the answer should be no. The donor impurities add electrons to the system as well as new levels inside the gap, while the accpetor impurities decrease the number of electrons and convert some of the band states into acceptor states inside the gap. In this way, at zero temperature we always have all valence band states full and all conduction band states empty. Otheriwise, we would end up with conduction electrons or holes present even in the ground state. I am not sure however if this is correct.

• Recall that typical dopant concentrations are in the parts per million range. The bit about zero temperature makes no sense, since any 'excess' carriers will be captured by the dopant levels you introduced in the first place. – Jon Custer Feb 9 at 20:47
• @JonCuster i think the zero temperature that is referred is about the example of Boron in the answer i provided. You are correct about the PPM range. I mean if someone wants to change certain attributes of semi-conductors then a precise recipe of impurities would occur and it should be in the form of PPM. – user141306 Feb 10 at 18:12