Semi-empirical models of electronic energy loss and damage formation by implanted MeV ions (B, P, As) at room temperature were investigated by comparing measurements with Monte Carlo simulations of impurity and damage depth distributions. Accurate prediction of dopant profiles in an amorphous target or in a low-dose implanted crystal was achieved by suitably parametrizing well-known analytical stopping models. In order to describe accurately the dynamic effects of damage accumulation during medium-dose implantation, an ion-energy dependence of the efficiency parameter used in the Kinchin-Pease model had to be introduced into the simulation. This factor, as determined by fitting measured integrals of defect profiles, was found to decrease for P and As ions; with increasing nuclear energy released to primary recoil atoms. It appeared to reach a saturation value of about 0.25. Full cascade simulations showed that the increased fraction of primary recoil energy spent in electronic processes, which was not considered in the simple Kinchin-Pease approximation, could not explain the observed trend. Although the empirical adjustment of damage efficiency led to good agreement between simulated and experimental dopant profiles, a systematic underestimation of the depth position of the peaks of simulated damage distributions was observed. This could not be accounted for by simple ballistic transport effects.

G.Lulli, E.Albertazzi, M.Bianconi, R.Nipoti, M.Cervera, A.Carnera, C.Cellini: Journal of Applied Physics, 1997, 82[12], 5958-64