Structural investigations on self-organized Si/SiGe islands by grazing incidence small angle X-ray scattering

We present a novel technique, based on grazing incidence small angle X-ray scattering (GISAXS)with which information on the shape and the lateral correlation of buried islands can be obtained. The GISAXS measurements were performed on Ge-rich islands grown by molecular beam epitaxy on (001) vicinal substrates with a miscut 2 degrees along the [100] direction. By varying the angle of incidence, GISAXS data sets were obtained for different information depths. These data were analysed quantitatively using a model based on the distorted wave Born approximation. In order to demonstrate the capabilities offered by this technique a 20 period Si/SiGe island multilayer sample was investigated before and after an annealing step at about 750 degreesC for 80 min. The GISAXS data show that the islands change their shape after annealing. For the top island layer a comparison of the GISAXS data with atomic force microscopy topographs was made.