The diffusion of Be during post-growth annealing was studied in epitaxial layers. Two models were proposed in order to explain the observed concentration profiles. In the first model, the Boltzmann-Matano method was used while taking account of the diffusivity time-independence. An observed double profile was explained in terms of a change in diffusivity. In a second model, vacancy equilibrium was not assumed, and kinetic terms which were related to vacancy production had to be included in the diffusion equations. The observed double profile was then explained in terms of a reduction in the vacancy concentration in the crystal bulk. By using these 2 approaches, it was shown that good agreement between the experimental and simulated profiles could be obtained. In the case of the non-equilibrium model, the vacancy concentration was close to its equilibrium value. It was therefore possible to assume that Be diffusion in InGaAs epitaxial layers occurred with quasi-equilibrium point defect concentrations. Under these conditions, the diffusion depth varied as the square root of the diffusion time. There was no significant under-saturation of vacancies or super-saturation of self-interstitials at the diffusion front which could change the normalized Be diffusion depth in InGaAs epitaxial layers.

J.Marcon, S.Gautier, S.Koumetz, K.Ketata, M.Ketata, P.Launay: Solid State Communications, 1997, 101[3], 159-62