Diffusion Mechanism of Zinc and Beryllium in Gallium Arsenide

摘要

The outstanding features associated with zinc and beryllium diffusion in galliumarsenide substrates and in GaAs/AlGaAs superlattices are explained either quantitatively or semi-quantitatively using the kick-out mechanism in which it is assumed that the doubly-positively-charged Ga self interstitial governs Ga self-diffusion. These features include (1) the dependence of the Zn solubility upon the pressures of the As and Zn vapor phases; (2) the square power law dependence of the Zn diffusivity on its own background concentrations under Zn isoconcentration diffusion conditions; (3) the different shapes of the Zn in-diffusion profiles; (4) the much lower diffusivities of Zn and Be under out-diffusion conditions than under diffusion conditions; (5) the tremendous enhancement effect of Zn in-diffusion on GaAs/AlGaAs superlattice disordering and the undetectable effect of Be under out-diffusion conditions. Some useful quantitative information has been obtained. Strictly on a qualitative basis, we have found that the Longini mechanism is also able to explain the above features (1)-(4) fairly well. The predicted effects of the Longini mechanism on Ga self-diffusion are, however, contrary to experimental results associated with superlattice disordering.