The diffusion of Si out of -planes in GaAs was investigated by means of high-resolution X-ray diffractometry, infra-red absorption localized vibrational mode spectroscopy and secondary ion mass spectroscopy. In the case of a Si -doped sample which had been grown at 400C with a Si areal concentration of 3.4 x 1014/cm2, the Si was confined to a layer which was no more than 0.5nm in thickness. After post-growth annealing (600C, 3h), 22.6% of the Si remained on the -planes, while the remainder had diffused homogeneously throughout the epilayer to give a Si concentration of 2.1 x 1019/cm3. Localized vibrational mode spectroscopy indicated that these Si atoms were located mainly on Ga sites (SiGa). The Si atoms were also found to occupy As sites, or were present as SiGa-SiAs pairs, Si-X and SiGa-VGa complexes. At 950C, all of the Si had diffused away from the -planes to form precipitates and dislocation loops near to the surface.

Si Diffusion Out of δ-Planes in a GaAs Superlattice. L.Hart, P.F.Fewster, M.J.Ashwin, M.R.Fahy, R.C.Newman: Materials Science Forum, 1994, 143-147, 647-52