Strain relief and shape oscillations in site-controlled coherent SiGe islands.

Strain engineering and the crystalline quality of semiconductor nanostructures are important issues for electronic and optoelectronic devices. We report on defect-free SiGe island arrays resulting from Ge coverages of up to 38 monolayers grown on prepatterned Si(001) substrates. This represents a significant expansion of the parameter space known for the growth of perfect island arrays.

Strain distribution in Si capping layers on SiGe islands: influence of cap thickness and footprint in reciprocal space.

We present investigations on the strain properties of silicon capping layers on top of regular SiGe island arrays, in dependence on the Si-layer thickness. Such island arrays are used as stressors for the active channel in field-effect transistors where the desired tensile strain in the Si channel is a crucial parameter for the performance of the device. The thickness of the Si cap was varied from 0 to 30 nm.

Strained MOSFETs on ordered SiGe dots.

The potential of strained DOTFET technology is demonstrated. This technology uses a SiGe island as a stressor for a Si capping layer, into which the transistor channel is integrated. The structure information of fabricated samples is extracted from atomic force microscopy (AFM) measurements.

X-ray nanodiffraction on a single SiGe quantum dot inside a functioning field-effect transistor.

For advanced electronic, optoelectronic, or mechanical nanoscale devices a detailed understanding of their structural properties and in particular the strain state within their active region is of utmost importance. We demonstrate that X-ray nanodiffraction represents an excellent tool to investigate the internal structure of such devices in a nondestructive way by using a focused synchotron X-ray beam with a diameter of 400 nm. We show results on the strain fields in and around a single SiGe island, which serves as stressor for the Si-channel in a fully functioning Si-metal-oxide semiconductor field-effect transistor.

Collective shape oscillations of SiGe islands on pit-patterned Si(001) substrates: a coherent-growth strategy enabled by self-regulated intermixing.

The shape of coherent SiGe islands epitaxially grown on pit-patterned Si(001) substrates displays very uniform collective oscillations with increasing Ge deposition, transforming cyclically between shallower "dome" and steeper "barn" morphologies. Correspondingly, the average Ge content in the alloyed islands also displays an oscillatory behavior, superimposed on a progressive Si enrichment with increasing size. We show that such a growth mode, remarkably different from the flat-substrate case, allows the islands to keep growing in size while avoiding plastic relaxation.