Closed-ampoule diffusion led to a net acceptor concentration which was lower than the Zn concentration. Upon annealing in an atmosphere without Zn, the Zn and net acceptor concentrations became almost identical. This was attributed to a decreased Zn concentration and an increased net acceptor concentration. The results were quantitatively explained by assuming that the Zn was incorporated as both substitutional acceptors and interstitial donors, and that only the interstitial Zn was driven out by annealing; due to its large diffusion coefficient. The profiles which were calculated by using this interstitial-substitutional model could be fitted to experimentally determined profiles by assuming that the Zn diffused as singly-ionized interstitial donors. The present model also explained published data, on diffusion in n-type InP, in which a profile cut-off was found at a depth where the acceptor concentration equalled the background donor concentration.

G.J.Van Gurp, T.Van Dongen, G.M.Fontijn, J.M.Jacobs, D.L.A.Tjaden: Journal of Applied Physics, 1989, 65[2], 553-60