Sn-rich cubic phase nanocrystals in a SiGe/Si(001) quantum well

We report on Sn-contained nanocrystals formed in Si and SiGe matrixes via Sn precipitation upon annealing of thin metastable Si1−x−yGexSny layers grown by molecular beam epitaxy. The nanocrystals exhibit a cubic lattice, which is coherent with the matrix. The density of the nanocrystals decreases with the annealing temperature revealing a kinetic formation pathway. New optical spectral features below the Si band gap are observed in photoluminescence spectra of the samples with nanocrystals. The origin of these new spectral features is discussed.