The diffusion and drift of Si were studied by means of capacitance-voltage measurements. These revealed that low substrate temperatures, during growth via molecular beam epitaxy, were required in order to achieve Dirac δ-like dopant profiles. It was further shown theoretically that the random Poisson distribution, which was usually assumed for dopant distributions in semiconductors, should be modified at high dopant concentrations. This was because of repulsive interactions between the impurities.

E.F.Schubert, C.W.Tu, R.F.Kopf, J.M.Kuo, L.M.Lunardi: Applied Physics Letters, 1989, 54[25], 2592-4