LATTICE-RELAXATION OF NANOSTRUCTURED SEMICONDUCTOR PILLARS OBSERVED BY HIGH-RESOLUTION X-RAY-DIFFRACTION

High resolution x-ray diffraction is used to obtain two-dimensional re ciprocal space maps from two-dimensional periodic arrays of small (<25 0 nm) semiconductor pillars. The pillars were made by etching an (001) oriented Si wafer that was epitaxially overgrown with Si1-xGex. The p illars were etched to such a depth that they have a Si bottom and a Si 1-xGex top. The shape of the pillars and the lattice parameters in the pillars are determined by comparison of the measured maps with kinema tical diffraction model calculations using separate Fourier transforma tion of the shape of the Si and Si1-xGex parts of the grating. It was found that in the pillars the Si1-xGex lattice was totally relaxed, wh ereas it was compressively strained prior to etching.