The surface structure of SiGe layers, deposited onto (100)Si, was studied by using surface analysis techniques. Low-energy electron diffraction data showed that the 2 x 1 surface reconstruction was changed into a 2 x n structure, where n was greater than 8. Scanning tunnelling microscopic images revealed that one dimer was missing after a sequence of n - 1 dimers. The density of missing dimers depended upon the Ge content and upon the layer thickness. Auger electron data revealed the existence of marked Ge segregation. The low-energy electron diffraction intensities suggested that the structure could be explained by a small expansion of the uppermost Ge-enriched SiGe layer.

R.Butz, S.Kampers: Applied Physics Letters, 1992, 61[11], 1307-9