Optical properties of germanium monolayers on silicon

Photoluminescence and Raman spectra of thin germanium layers grown on silic on at a low temperature (250 degreesC) have been studied. In structures of this kind, in contrast to those grown at high temperatures, luminescence fr om quantum wells is observed at germanium layer thicknesses exceeding simil ar to9 monolayers (ML). With the development of misfit dislocations, the lu minescence lines of quantum wells are shifted to higher energies and transv erse optical (TO) phonons involved in the luminescence are confined to a qu asi-2D germanium layer. Introduction of an additional relaxed Si0.95Ge0.05 layer into the multilayer Ge/Si structure leads to a substantial rise in th e intensity and narrowing of the luminescence line associated with quantum dots (to 24 meV), which points to their significant ordering. (C) 2001 MAIK "Nauka/Interperiodica".