The intermixing of superlattices was investigated as a function of the Si concentration following annealing at temperatures ranging from 500 to 900C. The superlattice samples were prepared by means of molecular beam epitaxy, and the near-surface layers were doped with Si to concentrations of between 2 x 1017 and 5 x 1018/cm3. The Si and Al depth profiles were measured by means of secondary ion mass spectrometry. The diffusion length and activation energy of Al, as a function of Si dopant concentration, were deduced from the secondary ion mass spectrometry data. Within the above temperature range a single activation energy, for Al diffusion, of about 4eV was observed (table 1). The Al diffusion coefficient increased rapidly with Si concentration.

P.Mei, H.W.Yoon, T.Venkatesan, S.A.Schwarz, J.P.Harbison: Applied Physics Letters, 1987, 50[25], 1823-5

Table 1

Diffusivity of Al in AlAs/GaAs