GROWTH INTERFACES OF SI1-XGEX/SI HETEROSTRUCTURES STUDIED BY INSITU LASER-LIGHT SCATTERING

Elastic scattering of laser light has been used to monitor surface topography in real time during growth of Si1-xGe(x) heterostructures. Large increases in scattered intensity were caused by surface height fluctuations in the alloy layers which, after growth, could be imaged in cross section by transmission electron microscopy and in plan view by scanning optical microscopy. For pseudomorphic alloy layers (x = 0.19 +/- 0.01) grown at 750-degrees-C the surface height fluctuations were periodic, the wavelength of approximately 270 nm giving strong laser scattering. Plan view transmission electron micrographs on such a layer showed periodic strain fluctuations with the same wavelength, whereas an equivalent layer grown at 610-degrees-C showed strain fluctuations which were irregular in shape and spatial distribution. The intensity of light scattered from the surface of this layer was much lower. Thick alloy layers grown beyond the critical thickness for appearance of misfit dislocations showed strong scatter which increased more quickly in intensity at higher growth temperature.