Layers were grown, by molecular beam epitaxy, at a substrate temperature of 520C. The layers contained three δ-doped planes, with Si concentrations of 4 x 1012, 1013 or 4 x 1013/cm3, and were annealed at temperatures of up to 648C. Secondary ion mass spectroscopy and capacitance-voltage methods were then used to monitor broadening of the profiles. It was found that the most lightly doped plane gave a near-Gaussian profile, and the diffusion coefficient was comparable with published data on the simple diffusion of isolated SiGa atoms. The more highly doped planes exhibited complex profiles with 2 components; in which some of the atoms were confined to the original plane, while there was an essentially square-shaped profile of fast-diffusing atoms. A comparison of the 2 types of experimental data suggested that the formation of Si islands took place during deposition of the δ-doped plane. This gave rise to electrically inactive atoms which could then diffuse into the surrounding material during heat treatment.

Post-Growth Diffusion of Si in Delta -Doped GaAs Grown by MBE.  R.B.Beall, J.B.Clegg, J.Castagné, J.J.Harris, R.Murray, R.C.Newman: Semiconductor Science and Technology, 1989, 4[12], 1171-5