[en] Amorphous Si/amorphous Ge artificial multilayers were prepared by ion beam sputtering. The diffusion or mixing lengths were measured very accurately from the change in the intensity of the X-ray diffraction peak resulting from the composition modulation. Annealing of multilayers with equiatomic average composition showed that the diffusivities are higher than the extrapolated values of the self-diffusivity in crystalline Ge, and that the temperature dependence after initial relaxation is described by D = 2.9 x 10^-3exp(-2.29eV/kT) cm²/sec. Amorphous Si/Ge multilayers have been partially mixed with 1.5 MeV Ar⁺ ions at temperatures in the range 77 to 673 K. The diffusive component of the square of the mixing length, obtained by subtracting out the ballistic contribution, does not depend on the dose rate at a given dose, and shows an Arrhenius-type temperature dependence with activation enthalpies between 0.13 and 0.22 eV. Possible mechanisms for migration and annihilation processes of defects are discussed to understand these low activation enthalpies. Silicon, boron or gold atoms were introduced into the Si/Ge multilayers by ion implantation or during the sputtering deposition. Annealing of Si-implanted samples showed that after relaxation the diffusivity appeared unaffected by the implantation process. Annealing of the multilayers containing B or Au impurities showed that the interdiffusion of Si and Ge in their amorphous phase is enhanced. The enhancement factor is independent of the degree of structural relaxation of the amorphous phase, as observed by the decrease of the diffusivity with annealing time. This can be explained by trapping of electrons or holes, introduced by the dopants, by preexisting structural defects