The diffusion of -function spikes of B in thin films which had been grown by solid-phase epitaxy was studied during annealing in vacuum. The results were compared with the effects of diffusion in films that had been grown by using low-temperature molecular beam epitaxy. The diffusion temperatures ranged from 750 to 900C, and the 2-dimensional concentrations were between 7 x 1013 and 1.6 x 1014/cm2. The diffusive behavior of dopants in the solid-phase epitaxial films was qualitatively different to that in films grown by low-temperature molecular beam epitaxy. This difference was attributed to the vacancy-like defects that were intrinsic to growth by the former method but not to growth by the latter method. The dopant profiles widened appreciably during solid-phase epitaxial re-growth; thus making the achievement of -function spikes impossible. After vacuum annealing, the diffusion coefficients for both n-type and p-type dopants were lower in solid-phase epitaxial films, than in films which had been grown by using the other method, by up to one order of magnitude. The diffused depth profile of the dopant in low-temperature molecular beam epitaxial films exhibited the characteristic deviation from a pure Gaussian that was expected, due to the concentration dependence of diffusion. That is, it had a flat top and steep shoulders. On the other hand, the dopant depth profiles in the other material exhibited a central spike and relatively flat shoulders after diffusion. The width of the central spike was, following an initial transient that was impossible to resolve, independent of the diffusion time and temperature. This indicated that the solid-phase epitaxial material was defective; with the defects acting as traps during diffusion.

H.J.Gossmann, A.M.Vredenberg, C.S.Rafferty, H.S.Luftman, F.C.Unterwald, D.C.Jacobson, T.Boone, J.M.Poate: Journal of Applied Physics, 1993, 74[5], 3150-5