A NOVEL METHOD OF ANALYZING PEAK BROADENING DUE TO MOSAICITY FOR CUBIC-CRYSTALS ON (001)SUBSTRATE USING DOUBLE-CRYSTAL X-RAY-DIFFRACTION MEASUREMENTS

A novel method of analyzing X-ray peak broadening due to mosaicity for double-crystal X-ray diffraction measurements is proposed, which is a n improved version of a conventional method using azimuthal angle depe ndence. The method is applicable to cubic crystals grown on a (001) su bstrate. The novelty of the method lies in the fact that the dependenc e of the full width at half-maximum (FWHM) on various relation indices hkl is analytically derived in detail. The geometric relation between a tilted epilayer and the hkl measurement configuration is clarified, and a theoretical formula is derived. The resultant value of the FWHM divided by cos theta(c), where theta(c) is the angle between (001) an d (hkl) planes, is independent of the reflection index when the broade ning is due to local tilt distribution caused by crystal mosaicity. Th e analytical method can be used as a criterion to judge whether or not X-ray pear; broadening is due to the mosaicity. It is demonstrated th at this formula holds for InAsP/InGaAsP SLS (strained layer superlatti ce) samples. The presented method is especially useful for samples wit h very weak peak intensity due to a high degree of mosaicity, to which reciprocal lattice-mapping measurement cannot be applied.