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.