Interference Fringes in the Plane Wave Topographic Images of Growth Bands in Si:Ge

An Si:Ge crystal with approximately 3% of germanium was studied with strongly collimated short-wavelength monochromatic synchrotron beam (beamline E2 at HASYLAB). The topographs obtained in the asymmetric 224 reflection revealed the presence of interference fringes related to growth bands caused by segregation of germanium. The fringes, observed for the first time, were strongly dependent on the angular setting and it was possible to distinguish at least three systems of fringes. A number of features of the existing strain field, which may be important for the formation of the fringes, was determined using other topographic methods, especially the Bragg-case section topography.