Trenches around and between self assembled silicon/germanium islands grown on silicon substrates investigated by atomic force microscopy

Self assembled silicon/germanium islands grown on silicon at high growth temperatures are investigated. The islands are studied with transmission electron microscopy (TEM) and trench formation around the islands is clearly identified. Selective wet chemical etching is used to remove the islands and facilitate atomic force microscopy (AFM) studies of the trench shape. Trenches are found to be anisotropic and the 4-fold symmetry of the trenches is related to the cubic symmetry of the elastic properties of the Si crystal. A simulation of the strain energy distribution under a SiGe island is presented and found to be in good qualitative agreement with the observed trench shape. It is verified by comparison of islands before and after etching that the etching process does not introduce artifacts.