A model was proposed for the effect of Zn in-diffusion in enhancing superlattice disordering. It combined recently proposed models for Ga self-diffusion and Zn diffusion in GaAs. Four coupled partial differential equations, which described the process, were solved numerically. Satisfactory agreement was obtained between the simulated results and published experimental data. At a given temperature, and for the values which were assumed for the diffusion coefficient and thermal equilibrium concentration of point defects, doubly positively charged Ga self-interstitials, IGa2+, were deduced to be a consistent splitting of the known Ga self-diffusion coefficient which was dominated by IGa2+. The superlattice disordering enhancement was due mainly to the Fermi-level effect, but IGa2+ supersaturation also made a small contribution. Because of p-doping by Zn acceptor atoms, the IGa2+ concentration was greatly increased via the Fermi-level effect. An IGa2+ supersaturation also developed because the IGa2+ generation rate was higher than its removal rate. Enhanced superlattice disordering occurred mainly under Ga-rich superlattice conditions. The Zn in-diffusion enhanced Al-Ga interdiffusion coefficient exhibited an apparent dependence, upon the Zns- concentration, which differed slightly from a quadratic relationship.

H.Zimmermann, U.Gösele, T.Y.Tan: Journal of Applied Physics, 1993, 73[1], 150-7