Untersuchung der Inselbildung im System SiGe/Si

In this work a study on the surface morphology of nominally pure Ge-islands grown on Si-(001)-substrates is presented. The samples were fabricated by low pressure chemical vapour deposition and investigated by scanning electron microscopy and atomic force microscopy. Qualitative and quantitative analyses could be derived from the atomic force micrographs. We were able to observe a clear dependence of the film morphology on substrate temperature. At 700 C a trimodal size distribution appeared, consisting of tiny islands with an average diameter of 33 nm, small sized islands of about 150 nm and large islands with diameters larger than 500 nm. While the size of tiny and small islands remained constant over a wide range of temperatures, the diameter of large islands increased with rising growth temperature. At low temperatures (550 C) only tiny islands appear. The results concerning growth morphology can be explained using theoretical models describing nucleation and growth of islands. The island shape seems to be determined preferably by the process of elastic relaxation, while kinetic effects have also to be taken into account. Transmission electron micrographs show that tiny and small islands are elastically relaxed, whereas large islands contain a lot of dislocations. Samples with a silicon cap layer exhibited islands which have become broader and more flat. Photoluminescence measurements were performed with capped samples. The half width of luminescence peaks was found to be determined by the island size distribution and the intensity remained constant in the temperature range from 20 K up to 77 K. (orig.)118 refs.Available from TIB Hannover: RA 831(3461) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman