INTERFACE ROUGHNESS CORRELATIONS IN Ge/Si/Si_1-xGex QUANTUM WELL HETEROSTRUCTURES. Y. Yamaguchi, P. M. Reimer, J.H. Li, O. Sakata, H. Hashizume, Tokyo Institute of Technology

We examine roughness correlations between interfaces in a simple Ge/Si/Si_1-x Gex heterostructure as a function of Si layer thickness. Recently it has been found [1] that the photoluminescence (PL) spectra from quantum wells (QW) of Ge/Si/Si_1-xGex (with x less than 0.4) can be strongly perturbed by growing several Ge-rich monolayers on top of a Si layer which tops the QW. No PL perturbation is observed for Si thicknesses greater than about 1000 nm, and the perturbation saturates for Si thicknesses less than about 30 nm.

We collected x-ray diffuse scattering data at glancing angles from solid-source MBE grown Ge/Si/Si_1-xGex heterostructures on Si (100) substrates, with a variety of Si layer thicknesses. Using techniques described in another session (see the presentation by P. M. Reimer, et. al.) we modelled and fit parameters to find in-plane and inter-layer roughness correlations as a function of Si layer thickness. Parameters may be compared with recent results from multilayers on Si (111) substrates (see the presentation by J.H. Li, et. al.).

[1] see N. Usami, H. Sunamura, T. Mine, S. Fukatsu, Y.Shiraki, J. Cryst. Growth, 150, 1065 (1995).