Recently, a general technique for the measurement for the threading dislocation densities in epitaxic semiconductors by high-resolution X-ray diffraction was reported [Ayers (1994). J. Cryst. Growth, 135,[71][72][73][74][75][76][77].Here, this method has been extended to the case of a Barrels five-crystal diffactometer by making use of known instrumental effects for this diffractometer. The usefulness of the method has been demonstrated by application of the technique to epitaxic ZnSe grown on GaAs (001) by photo-assisted metalorganic vapor-phase epitaxy. It is shown that in this case the threading dislocation density of the epitaxic layer can be determined quantitatively. Evidence for the introduction of dislocations in the underlying GaAs substrate is also presented.

A simple closed-form expression has been derived for the instrumental broadening function of the general Barrels five-crystal diffractometer. The use of this result allows the extraction of sample rocking-curve widths from the measured widths. Such use facilitates the determination of dislocation densities in heteroepitaxic crystals by the measurement of several hkl rocking curves using a Bartels five-crystal diffractometer.