Hi all, I think I understand the concept of doping a group IV semiconductor material with a group V atom which has one extra valence electron to "donate" to the conduction band, or doping with a group III atom with one too few electrons which will "accept" an electron from the lattice and leave behind a hole. As I understood it, donor atoms introduce shallow energy levels just below the conduction band edge, and acceptor atoms introduce levels just above the valence band edge. However I have been reading about defects within the silicon lattice and have seen several references to "donor-like" energy levels just above the valence band edge, and "acceptor-like" defect levels close to the conduction band edge. Is there something simple that I am missing here? I would appreciate any help to shed some light on this.