Characterization of morphology and defects in silicon-germanium virtual substrates

Silicon-germanium heterostructures incorporating virtual substrates are successfully used for both microelectronic and optoelectronic applications. However, their use is limited by their surface morphology (e.g. roughness) and defect (e.g. threading dislocations) density. High quality silicon-germanium heterostructures incorporating virtual substrates have been grown epitaxially using different methods. This study reports the effects of the growth parameters on the morphology and defects in different silicon-germanium heterostructures incorporating virtual substrates grown in the Southampton University Microelectronics center (SUMC) by low pressure chemical vapor deposition (LPCVD). Two types of structures: one with a linear and the other with a step variation of the germanium concentration in the virtual substrate, were grown and characterized. Results obtained were in good agreement with others already reported in the literature for similar structures grown using different epitaxial techniques.