It was noted that Mg implants in this material exhibited 2 types of diffusion during annealing. These were up-hill diffusion in the implantation peak, and concentration-dependent diffusion into the bulk. The up-hill diffusion predominated at short times and low temperatures, while the concentration-dependent diffusion was predominant at long times and high temperatures. By studying implants that had been annealed at temperatures where no up-hill diffusion occurred, diffused profiles could be modelled and an expression for the Mg diffusivity could be obtained. The activation energy for this process was 1.77eV. The results of Fermi level experiments showed that the diffusivity was hole-dependent rather than concentration dependent. The hole-dependent exponent was equal to unity for Mg which was implanted into semi-insulating substrates, but could change to 2 at high hole concentrations.

H.G.Robinson, M.D.Deal, D.A.Stevenson: Applied Physics Letters, 1991, 58[24], 2800-2