UNAMBIGUOUS DETERMINATION OF CRYSTAL-LATTICE STRAINS IN EPITAXIALLY GROWN SIGE SI MULTILAYERS/

A new method for unambiguous reconstruction of crystal-lattice strains in epitaxially grown layers from high-resolution x-ray diffraction da ta is proposed. The technique uses x-ray diffracted intensity profiles collected for two different radiation wavelengths. We enhance the the ory for the previously developed algorithm for model-independent deter mination of crystal-lattice strain profiles in single crystals with ep itaxially grown top-surface layers. The method relies on the retrieval of the scattered x-ray wave phase from its intensity profile via a lo garithmic Hilbert transform. This phase-retrieval technique is always associated with the problem of complex polynomial root finding. A prac tical procedure for the mapping of complex polynomial roots is propose d to distinguish true and virtual zeros. This allows the phase of the diffracted x-ray wave to be retrieved unambiguously. The method was ap plied to determine physical dimensions and concentration composition o f a Si/Si1-xGex/Si alloy multilayer structure typical for SiGe heterob ipolar transistor device. (C) 1996 American Institute of Physics.