It was shown that percolation controlled not only diffusion in solids, but also controlled the electrical activity of semiconductors; via the doping action of the diffusing species. This occurred in Hg1-xCdxTe when x was less than 0.8. A 107-times higher diffusivity at x-values below 0.8 was explained by noting that the percolation threshold for an ideal face-centered cubic lattice was at 0.19. While Ag was normally a donor, it could become an acceptor by stabilizing the Hg(I) state. This was possible by interaction with two Hg neighbours, and such a process was favourable above the Hg percolation limit. Fast Ag diffusion was also related to the occurrence of ultra-low concentration phase-separation in this system, since it was the result of a balance between elastic attraction and Coulombic repulsion between the charged dopants.

Can Percolation Control Doping, Diffusion and Phase Segregation in HgCdTe? D.Cahen, O.Melamed, I.Lubomirski: Journal of Crystal Growth, 1999, 197[3], 537-41