The diffusion mechanisms which operated during post-growth annealing were investigated in p-type Be-doped epitaxial layers which had been grown between 2 undoped InGaAs layers. Annealing (30 to 180s, 500 to 800C) was applied to samples with dopant concentrations of 5 x 1018, 1019 or 3 x 1019/cm3. It was found that no appreciable Be diffusion occurred during post-growth rapid thermal annealing, for all of the dopant levels, when annealing was carried out at 500 or 600C for times of less than 60s. The same was true, for a Be concentration of 5 x 1018/cm3, during annealing at 700C for 30s. At a doping level of 3 x 1019/cm3, significant Be diffusion occurred during annealing (>700C, 60s). The resultant curves exhibited a concave kink region (figure 4). It was deduced that the effective Be diffusion coefficient was approximately constant in one part of the concentration profile, and was proportional to the square root of the concentration in another part. By assuming the latter dependence, an effective diffusivity could be substituted into Fick’s second law. The resultant differential equation was solved numerically by using an explicit finite difference method. Good agreement was obtained between the measured depth profiles and the simulated distributions.

S.Koumetz, J.Marcon, K.Ketata, M.Ketata, P.Launay: Journal of Physics D, 1997, 30[5], 757-62