2XN SURFACE-STRUCTURE OF SIGE LAYERS DEPOSITED ON SI(100)

The surface structure of SiGe layers deposited on Si(100) has been studied by surface analysis techniques. The 2 X 1 surface reconstruction is changed into a 2 X n (n > 8) structure observed in low energy electron diffraction. Scanning tunneling microscopy pictures reveal that after (n - 1) subsequent dimers one dimer is missing. The density of missing dimers depends on the Ge content and on the layer thickness. Auger electron spectra show a strong Ge segregation. The evaluation of the intensities of low energy electron diffraction can explain the structure by a small expansion of the topmost SiGe layer enriched by Ge.