Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry and kinetics of P-for-As exchange reaction
The fundamental chemical and kinetic surface processes governing the P-for-As exchange reaction during epitaxial layer synthesis are investigated. Exposure of a GaAs surface to phosphorus molecular beams (P2) is carried out to create superlattice structures realized by surface reactions. The impact of the GaAs surface reconstruction, the P-soak time, and the surface temperature on the extent of intermixing and on the mechanism governing the anion exchange has been studied using x-ray diffraction, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and atomic force microscopy. It is found that As-rich GaAs surface reconstructions inhibit P-for-As exchange. The extent of the anion exchange increases with temperature. Furthermore, the P-for-As exchange is not controlled by P diffusion into the GaAs. We propose a chemical model that includes P chemisorption and indiffusion, and the competition between P-for-As anion exchange and the formation of AsP isoelectronic compounds. © 2006 American Institute of Physics.
Brown, AS; Losurdo, M; Capezzuto, P; Bruno, G; Brown, T; May, G
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