Abstract
We present an experimental and theoretical analysis of the formation of nanovoids within Si microcrystals epitaxially grown on Si patterned substrates. The growth conditions leading to the nucleation of nanovoids have been highlighted, and the roles played by the deposition rate, substrate temperature, and substrate pattern geometry are identified. By combining various scanning and transmission electron microscopy techniques, it has been possible to link the appearance pits of a few hundred nanometer width at the microcrystal surface with the formation of nanovoids within the crystal volume. A phase-field model, including surface diffusion and the flux of incoming material with shadowing effects, reproduces the qualitative features of the nanovoid formation thereby opening new perspectives for the bottom-up fabrication of 3D semiconductors microstructures.
Highlights
In recent years the monolithic integration of group IV and III− V semiconductors on silicon has been widely investigated as a viable pathway to go beyond Moore’s law
Microcrystals grown on deeply etched Si substrates exhibit clear crystallographic facets with well-defined orientations, corresponding to the most stable crystal planes of the Si face centered cubic (FCC) crystal, i.e. (001), {111}, and {113}
In the high deposition rate case, the (001) facet can be found on top of pillars smaller than 3 × 3 μm[2] and occupies a larger fraction of the microcrystal surface as compared to the corresponding sample grown at a lower rate
Summary
In recent years the monolithic integration of group IV and III− V semiconductors on silicon has been widely investigated as a viable pathway to go beyond Moore’s law. The material quality of such microcrystals has been deeply investigated, showing that the thermal strain is fully relaxed[5] and that all the threading dislocations can be expelled from the crystals.[6] it has been predicted[7] and experimentally verified[8,9] that, by decreasing the size of the pillars etched into the substrate and by linearly grading the compositional profile, it is possible to achieve full elastic relaxation without the nucleation of misfit dislocations
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