Delta-doped layers were made by depositing Sb onto monocrystalline Si, and then depositing amorphous Si, before performing a final solid-phase epitaxy treatment at 620C. After post-annealing at temperatures of between 625 and 725C, Sb precipitates with a diameter of several nm were observed in the -plane by using transmission electron microscopy. By using channelling Rutherford back-scattering spectrometry, the increase in the precipitate fraction with time was deduced from the minimum-yield signal. The results were explained by using a model which was based on Sb nuclei that grew via the lateral diffusion of Sb atoms, in the -plane, followed by incorporation into the nucleus. The generation of nuclei appeared to involve 2 parallel processes. One was the rapid simultaneous generation of a limited number of nuclei at low-energy sites in the -plane, with subsequent diffusion-controlled growth, and the other was the slow continuous generation of a larger number of nuclei at random sites in the -plane, with subsequent incorporation-controlled growth. The diffusion of Sb at the extremely high concentrations used here was very fast and concentration-dependent. This could be explained by the Mathiot-Pfister model for vacancy-percolation diffusion. The activation energy for the incorporation of Sb atoms into liquid precipitates appeared to be considerably lower than that for incorporation into solid ones.

C.Van Opdorp, L.J.Van Ijzendoorn, C.W.Fredriksz, D.J.Gravesteijn: Journal of Applied Physics, 1992, 72[9], 4047-62