The mechanism of Si diffusion was studied by using photoluminescence and secondary ion mass spectrometry, and transmission electron microscopy across the corner of a wedge-shaped sample. The diffusion source was a grown-in highly Si-doped layer. It was deduced that Frenkel defects (column-III vacancies and interstitials) were generated within the highly Si-doped region. The column-III interstitials rapidly diffused towards the surface, where they reacted with the column-III vacancies which were generated at the surface during annealing in a gaseous As ambient. This caused a supersaturation, of column-III vacancies in the Si-doped region, which drove Si diffusion. Annealing in vacuum reduced the supersaturation of column-III vacancies, and thus decreased Si diffusion. A predominant Si-donor plus column-III vacancy complex emission band was found in spectra from the Si-diffused region. The results supported the concept of a vacancy-assisted mechanism for Si diffusion and impurity-induced disordering.

Role of Point Defects in the Silicon Diffusion in GaAs and Al0.3Ga0.7As and in the Related Superlattice Disordering.  L.Pavesi, N.H.Ky, J.D.Ganière, F.K.Reinhart, N.Baba-Ali, I.Harrison, B.Tuck, M.Henini: Journal of Applied Physics, 1992, 71[5], 2225-37