The anomalous distribution of As which was implanted under self-annealing conditions (with simultaneous damage recovery activated by beam heating) was investigated. Rutherford back-scattering/channelling, transmission electron microscopy, and carrier profiling techniques were used to analyze the dopant profiles and the microstructure of samples which had been irradiated with 150keV As+ ions to a current density of about 0.000207A/cm2 for between 2 and 6s. Two relevant effects were observed. The first one consisted of the formation of 2 dopant peaks which were electrically inactive and were separated by a depletion region at the position of the ion projected range. Whereas the deeper peak disappeared with increasing irradiation time, the one which was located at the maximum of nuclear energy loss tended to grow. Microstructural analysis suggested that both peaks occurred as a result of As segregation at lattice defects. In particular, the one which was located at the maximum of nuclear energy loss was a consequence of the segregation of As atoms at voids which formed during irradiation at high temperatures. The second relevant effect was the formation of a deeply penetrating tail, in the As profile, which could not be explained by a simple thermal diffusion mechanism. Although a contribution from channelling effects could not be ruled out, the effect seemed to be related mainly to a diffusivity enhancement that was weakly temperature dependent and was due to interaction of the dopant with radiation-induced defects.

G.Lulli, P.G.Merli, R.Rizzoli, M.Berti, A.V.Drigo: Journal of Applied Physics, 1989, 66[7], 2940-6