THE MEASUREMENT OF THREADING DISLOCATION DENSITIES IN SEMICONDUCTOR CRYSTALS BY X-RAY-DIFFRACTION

The measurement of threading dislocation densities in heteroepitaxial semiconductor layers is important for the development of injection las ers, microwave transistors, and also the integration of devices in dis imilar semiconductors. Dislocation density measurements have been made by destructive techniques such as etching and by transmission electro n microscopy (TEM). However, X-ray rocking curves provide non-destruct ive measurements of dislocation densities with accuracy equal to cryst allographic etches or TEM. The theory of this technique has been descr ibed by Gay, Hirsch, and Kelly [P. Gay, P.B. Hirsch, and A. Kelly, Act a Met. 1 (1953) 315] and Hordon and Averbach [M.J. Hordon and B.L. Ave rbach, Acta Met. 9 (1961) 237], for the case of highly dislocated meta l crystals. In this paper, the theory of dislocation density measureme nt from rocking curves is extended to the case of (001) zinc-blende se miconductors. It is shown that the measurement of several (hkl) rockin g curve widths with a particular X-ray wavelength allows the calculati on of the dislocation density by two independent techniques, thus allo wing for a check of self-consistency. It is shown that for the case of epitaxial GaAs on Si(001), dislocation densities determined by these two methods are in good agreement.