High depth-resolution secondary ion mass spectrometry profiling was used to investigate the broadening of δ-doped planes of Be in material which had been prepared by using molecular beam epitaxial methods. It was confirmed that concentration-dependent diffusion was the predominant broadening process for Be at growth temperatures of less than 600C. By incorporating Si atoms into the same plane, it was shown that the broadening could be completely inhibited. This suggested that the rapid diffusion process resulted from mutual repulsion between the BeGa- ions, and was prevented by the reverse field which arose from SiGa+ ions or by the formation of low-mobility SiGa+-BeGa- complexes. The rapid diffusion of Si as SiGa-SiAs pairs was also reduced. The latter was attributed to a Fermi-level effect, with compensation by Be tending to reduce the probability of SiAs formation. The surface segregation of Si was unaffected, whereas that of Be was reduced. This indicated that the surface fields which existed during growth contributed to the behavior of Be, but not to that of Si.

Migration Processes of Co-Doped Si and Be Delta-Planes in MBE-Grown GaAs. J.J.Harris, J.B.Clegg, R.B.Beall, J.Castagné: Semiconductor Science and Technology, 1990, 5[7], 785-8