Growth features at competing nucleation of quantum dots and nanopits in Si-Ge-C ternary system

The continuum elasticity model is applied to quantitatively investigate the growth features and nucleation mechanism of quantum dots (QDs), nanopits, and joint QDs-nanopits structures in SiGeC ternary systems. We determined the critical concentrations of carbon, x = 0.08 for Si 1− x C x and y = 0.0033 for Si 1− x − y Ge x C y at the concentration of germanium x = 0.467, when the growth mode changes from, respectively, nucleation of QDs to formation of nanopits. We have shown that the increase in the carbon concentration in a SiC binary system and of germanium concentration in a SiGeC ternary system leads to a decrease in the critical size of QD. The free energy of mixing for Si 1− x − y Ge x C y ternary system was calculated and studied and its 3D sketch plotted. It is demonstrated that incorporation of carbon into Si and Ge up to background impurity concentration is energetically preferable, which explains the experimentally detected “contamination” of silicon and germanium crystals by carbon during the growth in the graphite crucible.