Vertical correlation of SiGe islands in SiGe/Si superlattices: X-ray diffraction versus transmission electron microscopy

We have investigated the vertical correlation properties of SiGe islands in a series of Si/SiGe multilayers using grazing incidence x-ray diffraction. The degree of island correlation is found to strongly depend on the thickn ess of the Si spacer layer separating subsequent SiGe layers. A comparison with results obtained from transmission electron microscopy demonstrates th e feasibility of the x-ray diffraction method for the investigation of samp le series, and an improved statistical accuracy of the obtained parameters: with x-ray diffraction, the statistical average of typically 10(6)-10(7) i sland columns is obtained, compared to only few in the case of transmission electron microscopy. (C) 2000 American Institute of Physics. [S0003-6951(0 0)00252-7].