Evolution and ripening of Ge crystals grown by nanoscale induced lateral epitaxy on localized oxide

Abstract

We have previously demonstrated that a high quality Ge on SiO2 layer can be grown by nanoscale seed induced lateral epitaxy, using a method based on the standard local oxidation of silicon technique for creating nanoscale silicon seeds. The growth of Ge from germane is initiated in two silicon seed lines and evolves toward a complete wetting of the SiO2 stripe after coalescence. For isolated crystals, the wetting mechanism of SiO2 by Ge is strongly dependent upon the seed orientation and closely related to the development of {111} facets. We show here that the energetic balance between different surface and interface energies governs the wetting configuration of SiO2 by Ge, and therefore defines the angle of contact between Ge and SiO2, that can only be satisfied by the development of a (11-1) facet in the case studied. We derive from Young's equation an interfacial energy between Ge and SiO2 equal to 5.67 eV/nm2. We show that the coalescence of Ge crystals is mainly driven by surface diffusion, which includes two main aspects. Diffusion driven by the chemical potential gradient due to the variation of seed curvatures leads to preferential nucleation at concave corners of patterns. At the same time, a ripening phenomenon is observed when the two crystals come in contact with each other. © 2011 American Institute of Physics.