A study is made of the diffusion of copper, silver, and gold labelled by the corresponding radioactive tracers in epitaxial AlxGa1−xAs–GaAs heterostructures in the temperature range 800 to 1000°C. The maximum concentration of impurity is shown to occur in the film–substrate interface region. A similar maximum occurs in the distribution of the dislocation density over the thickness of the structures. The totality of the diffusion, metallographic, electric, and optical studies performed permits to conclude that the observed anomalous concentration profiles are caused by interaction of the group I impurities with imperfections at the boundaries of epitaxial structures.
Both surface and bulk nonuniformities in A1,Gq -,As solid solution compositions were determined by surface radiography of epitaxial A1,Gal -,As-GaAs heterojunctions with diffused radioactive Zne5 atoms. properties of epitaxial films depend to a considerable extent on uniformity of their composition, impurity distribution, structural defects etc. The distribution of solid solution components and impurities is usually studied by X-ray electron probe analysis ( DZHAFAROV et al. 1967DZHAFAROV et al. , 1969 as well as by the methods based on electrical and radioactive measurements on individual layers (BOLTAKS) It is often desirable to obtain the distribution pattern of composition uniformity over the surface. Using for this purpose the method of contact radiography (DRITZ et al.), we succeeded in determining the nonuniformity in the composition of A1,Gal -,As solid solutions. It should be noted that the use of autoradiography in its conventional form is not always possible because of difficulties encountered in finding convenient isotopes in the systems of interest (in particular, in the A1,Gal -,As solid solutions). These difficulties can be avoided by diffusing into the surface of the sample radioactive tracer atoms the distribution of which would be sensitive to nonuniformities in composition. Radiography involving tracer atoms permits to obtain the pattern of distribution of solid solution components both on the surface and in the bulk of the crystal.The method used is essentially as follows. First, brief diffusion is effected into the sample under study of a radioactive impurity with sufficient high solubility. Next, the sample is subjected t o contact radiography with subsequent photometry. Since the surface concentration of impurity depends on solid solution composition (ARSENI et al.), a change in composition over the surface should produce a corresponding change in concentration of the radioactive isotope of impurity, and hence, a change in the density of blackening over the surface.The above method of locating nonunformities in solid solution compositions was tested on A1,Gal -,As-GaAs-heterostructures.The heterojunctions were
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.