Diffusion mechanism of zinc and beryllium in gallium arsenide

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Abstract
The outstanding features associated with Zn and Be diffusion in GaAs substrates and GaAs/AlGaAs superlattices are explained either quantitatively or semiquantitatively 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 (i) the dependence of the Zn solubility upon the pressures of the As and Zn vapor phases, (ii) the square power‐law dependence of the Zn diffusivity on its own background concentrations under Zn isoconcentration diffusion conditions, (iii) the different shapes of the Zn in‐diffusion profiles, (iv) the much lower diffusivities of Zn and Be under out‐diffusion conditions than under in‐diffusion conditions, and (v) 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 (i)–(iv) fairly well. The predicted effects of the Longini mechanism on Ga self‐diffusion are, however, contrary to experimental results associated with superlattice disordering.