A broad investigation was made of Al implantation in crystalline Ge. It was shown that, up to 600C, Al did not diffuse and a remarkable electrical activation of ∼1020/cm3 was obtained. For annealing temperatures of 700 to 800C, Al exhibited significant diffusion towards the bulk and an unexpected uphill diffusion next to the surface, where the electrical measurements indicated a significant deactivation of Al. Both these latter observations were explained in terms of the presence of dopant traps, able to make immobile and electrically inactive the dopant next to the surface.

Aluminium Implantation in Germanium: Uphill Diffusion, Electrical Activation, and Trapping. G.Impellizzeri, E.Napolitani, S.Boninelli, V.Privitera, T.Clarysse, W.Vandervorst, F.Priolo: Applied Physics Express, 2012, 5[2], 021301