X-ray studies on self-organized wires in SiGe/Si multilayers

step-bunching process during the growth on vicinal Si substrates provides a template both for improved lateral ordering and size control of the result ing Ge-rich self-assembled quantum dots or wires. We have investigated a 20 period SiGe/Si wire multilayer grown by molecular beam epitaxy on a misori entated Si(001) substrate with a large miscut of 3.5 degrees towards the [1 00] direction. Parallel to the steps, i.e. along the [010] direction, Ge-ri ch wires are formed spontaneously. Their surface morphology was studied wit h atomic force microscopy. In order to get information on the shape and the lateral correlation not only of the wires on the top surface but also of t he buried ones, we employed grazing incidence small-angle x-ray scattering (GISAXS). The GISAXS data were taken for different information depths in tw o orthogonal azimuths. Side maxims in coplanar high-angle diffraction and G ISAXS data indicate the presence of Ge-rich self-organized wires at the bur ied heterointerfaces.