An X-ray double- and triple-axis diffractometry study was made of mosaic structures in partially-relaxed Si0.7Ge0.3 epilayers which had been grown onto (001) Si substrates. The samples had differing layer thicknesses and differing degrees of strain relaxation. The results showed that, in the early stages of strain relaxation, the films contained mosaic regions which were separated laterally by perfect regions. This was because the mosaic structure which was caused by a misfit dislocation was effectively localized within a lateral range of the layer thickness. The film was therefore essentially a perfect crystal far from dislocations. With increasing degree of strain relaxation, and thus dislocation density, the mosaic regions of the layer expanded while the perfect regions shrank and finally vanished. The results also indicated that the usual method for estimating the dislocation density from the X-ray rocking curve width failed in the present case.

Evolution of Mosaic Structure in SiGe Epilayers Grown on Si(001) Substrates J.H.Li, C.S.Peng, Z.H.Mai, J.M.Zhou, Q.Huang, D.Y.Dai: Journal of Applied Physics, 1999, 86[3], 1292-7