Microscopic structure of interfaces in Si1−xGex/Si heterostructures and superlattices studied by x-ray scattering and fluorescence yield

Abstract

The angular dependences of grazing-incidence x-ray scattering and Ge Kα fluorescence yield were measured for ${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Ge}}_{\mathit{x}}$/Si and its inverted Si/${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Ge}}_{\mathit{x}}$ heterostructures. The results reveal useful information on microstructures in these layered materials and show similar interfacial structures in terms of the rms interfacial roughness, correlation length of height fluctuations, and Ge density profile. Two ten-period superlattices with different thickness and Ge concentration were also investigated; correlation between height fluctuations of different interfaces is clearly demonstrated in the data of x-ray-diffuse scattering. These results show that x-ray scattering and fluorescence techniques can be employed as convenient tools for nondestructive characterization of epilayer thickness, interfacial roughness, density profile of selected atomic species, and correlations between microstructures of different interfaces in layered materials.