Effects of p-type dopants on enhancing AlAs/GaAs superlattice disordering

It is quantitatively shown that the mechanism reponsible for enhancing AlAs/GaAs superlattice disordering by the p-type dopants Zn and Be is essentially the Fermi-level effect occurring in Ga-rich crystals. In the abundance of holes, the Fermi-level effect increases the concentration of the doubly-positively-charged group III element self-interstitials (designated as I-GA(2+)), which govern Al-Ga interdiffusion in crystals rich in group III elements. Under Zn (or Be) in-diffusion and ion implantation conditions, the crystal portion where the enhanced Al-Ga interdiffusion occurs has become rich in group III elements irrespective of whether the annealing ambient is As rich or poor. This is because the incorporation of the Zn (or Be) atoms onto the group III sublattice site will naturally produce crystals rich in group III elements. In the As-rich annealing ambient cases, only the crystal surface region becomes rich in As, while the superlattice disordering reaction occurs in the deeper Zn (or Be) diffusion front region, which is rich in group III elements.