It was recalled that the ordering of donor and acceptor levels which were introduced into the band-gap by H was related to a positive- or negative-U behavior of H and was crucial to the interaction of H with deep defects. It was shown here that an analysis of the atomic arrangements, and of the electronic-charge distributions for a H atom in the presence of a deep donor (the As antisite), provided clear evidence of an inverted order of the H-induced levels and permitted an estimate to be made of their position in the band-gap.

Evidence of the negative-U behavior of H in GaAs A.A.Bonapasta: Physical Review B, 1998, 58[16], 10378-82