Diffusion experiments were performed on samples of Si-doped AlxGa1-xAs epitaxial layers, with x-values which ranged from 0 to 0.30, as a function of the Si doping level and the diffusion temperature. For each composition, calculated H diffusion profiles which had been deduced by using Mathiot's model were fitted to the experimental profiles. It was assumed that H behaved as a deep acceptor, and that Ho and H- were the diffusing species. The trapping of H- by Si+ donors, and their acceleration by an electric field, were incorporated into the model. As well as the diffusion coefficient of H, and the dissociation constant of the SiH complexes, the model provided for a compositional dependence of the H acceptor level in AlGaAs alloys. It was concluded that the H acceptor level was localized in the band-gap of the present AlGaAs alloys, and deepened below the  conduction band as x increased.

B.Machayekhi, R.Rahbi, B.Theys, M.Miloche, J.Chevallier: Materials Science Forum, 1994, 143-147, 951-6