The diffusion of CrS resulted from the rapid migration of Cri, and their subsequent change-over so as to occupy Ga sites (or  vice versa); a typical substitutional-interstitial diffusion process. It was noted that there were 2 ways in which the Cri-Crs change-over could occur. One involved a kick-out mechanism in which Ga self-interstitials took part, and the other involved a dissociative mechanism in which Ga vacancies took part. It was observed that the Crs in-diffusion profiles had a characteristic shape which revealed the predominance of a kick-out mechanism, whereas the Crs out-diffusion profiles were erf-shaped; thus reflecting the predominance of the dissociative mechanism. An integrated substitutional-interstitial diffusion mechanism, which took account of kick-out and dissociative mechanisms, was here used to analyze Cr diffusion results. It was confirmed that the kick-out mechanism governed Cr in-diffusion, while the dissociative mechanism governed Cr out-diffusion. The parameters which were used to fit existing experimental results provided quantitative information on the Ga self-interstitial contribution to the Ga self-diffusion coefficient. The values which were obtained (table 13) were consistent with those of a study of Zn diffusion in GaAs, and with available experimental data on Al-Ga interdiffusion coefficients.

S.Yu, T.Y.Tan, U.Gösele: Journal of Applied Physics, 1991, 70[9], 4827-36