Silicon-Germanium Nanostructures: From Physics to Applications
Sprache des Vortragstitels:
In this talk an overview will be presented on electronic and optical properties of silicon-germanium nanostructures .
In 2003 Germanium was introduced into mainstream Si technology and has been used ever since. Oue to the different lattice constants of Ge and Si mechanical strain is introduced in SiGe grown on Si substrates, which leads to a modification of the electronic band structure. This is used to enhance e.g. the carrier mobility in electronic CMOS devices and has been essential for the continued validity of Moore's law up to now. In devices based on planar technology, the maximum strain values employed are about 0.5%. However, in Si-cap layers on top of three dimensional self-organized SiGe islands deposited on two-dimensional periodic pit-patterned Si substrates strains above 1% can be achieved to further enhance the electronic characteristics of field effect transistors. Synchrotron x-ray diffraction experiments with focused x-ray beams have been used to determine the strain distribution even in a single transistor. The optical properties of two-dimensional (20) ordered SiGe islands are modified, too, with respect to their randomly nucleated counterparts on flat substrates. Oue to their inherent island size and composition homogeneity their photoluminescence emission lines are much narrower. Furthermore the 20 Ge island arrays can be incorporated commensur ately in two-dimensional photonic crystal slab structures and thereby not only room temperature infrared emission is achieved but also a custom tuning of their overall light emission properties.