Evidence of the negative-U behavior of H in GaAs from an investigation of H and As antisites

The ordering of the donor and acceptor levels induced by hydrogen in the band gap of GaAs is related to a positive- or negative-U behavior of H and is crucial in the interaction of H with deep defects. However, it is still an object of debate because of uncertain experimental results. In the present paper, it is shown that an analysis of the atomic arrangements and of the electronic-charge distributions fur a H atom in presence of a deep donor, the As antisite, provides clear evidence of an inverted order of the I-I-induced levels and allows to estimate their position in the band gap. [S0163-1829(98)09239-X].