HIGH-RESOLUTION X-RAY-DIFFRACTION FROM MULTILAYERED SELF-ASSEMBLED GEDOTS

We have studied multilayers of self-assembled Ge-rich dots embedded in silicon grown by molecular-beam epitaxy using high resolution x-ray r eciprocal space mapping and reflectivity. The Si spacer thicknesses be tween the dot arrays were in the range of 10-40 nm, the typical dot si ze was about 150 nm for the diameter and 7 nm for the height. The meas ured reciprocal space maps were simulated using statistical kinematica l x-ray-diffraction theory, and a good agreement between experimental and simulated data has been achieved. From the measurements, the in-pl ane strain in the dot lattice was determined. We derived the degree of the vertical correlation of the dot positions (''stacking'') and a la teral ordering of the dots in a square array with main axes parallel t o the < 100 > directions, with an array lattice constant of about 500 nm.