The migration of Cr was studied by using a new photoluminescence method which involved measurement of the Cr-related luminescence intensity. The form of the intensity profiles after thermal annealing was explained in terms of the substitutional-interstitial dissociative mechanism. It was observed that the redistributed profiles had an abnormal peak, in the near-surface region of wafers, which was annealed out by heat treatment at temperatures above 900C for 6h. This was attributed to the in-diffusion of As vacancies from the surface. The Cr-related luminescence was studied as a function of the As pressure during wafer annealing. The data showed that the in-depth profiles could be understood in terms of the diffusion of Cr and As vacancies. The luminescence center was deduced to be a CrGa-VAs complex.

J.T.Hsu, T.Nishino, Y.Hamakawa: Japanese Journal of Applied Physics, 1987, 26[5], 685-9