X-ray diffraction studies of semiconductor nanostructures

The silicon-germanium material system is not only of interest for basic research but also of high importance for advanced electronic, optoelectronic, or mechanical nanoscale devices. A detailed understanding of the structural properties and in particular the strain state of nanostructures forming the building blocks for such devices, or of the active region of functioning devices is of high interest. To tune device characteristics at the frontiers of scaling, strain engineering is a versatile tool to overcome restrictions or tailor material properties. To speed up silicon-based transistors, both tensile (enhanced electron mobility, n-type) or compressive strain (higher hole mobility, p-type) can be applied to the Si channel of MOSFETs, depending on the geometry of the device. Several approaches to induce strain exist, for example the application of stressed nitride layers or the use of planar SiGe stressor structures. The latter have the disadvantage to develop dislocations easily, which then act as scattering centers for charge carriers and thereby impair the functionality of the transistor.