Self-organization of germanium nanoislands obtained in silicon by molecular-beam epitaxy

Nanometer germanium islands in epitaxial layers of silicon are obtained by molecular-beam epitaxy. The dimensions and shapes of the islands are determined in an atomic-force microscope. The photoluminescence spectra are found to contain lines that can be interpreted as quasidirect optical transitions in the islands. It is concluded on the basis of optical and microprobe measurements and theoretical calculations of the energies of electronic states that silicon is dissolved in the germanium islands. Values of the germanium and silicon contents in the solid solution are presented. (C) 1998 American Institute of Physics. [S0021-3640(98)00901-3].