Atomic-resolution images of Be delta-doped layers were obtained by means of cross-sectional scanning tunnelling microscopy. In the case of samples which had been grown at 480C, it was observed that the doping layer width for concentrations of up to 1013/cm2 was less than 1nm. At higher dopant concentrations, it was found that the dopant layer thickness increased markedly with dopant concentration. It was suggested that this broadening of the dopant layer at high dopant concentrations was due to Coulombic repulsion between individual Be ions. The effect of Coulombic repulsion could also be observed in the spatial distribution of the dopant atoms in the plane of the dopant layer.

P.M.Koenraad, M.B.Johnson, H.W.M.Salemink, W.C.Van der Vleuten, J.H.Wolter: Materials Science and Engineering B, 1995, 35[1-3], 485-8