@phdthesis{Schlykow2019, author = {Schlykow, Viktoria Diana}, title = {Selective growth and characterization of GeSn nanostructures on patterned Si wafers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-48860}, school = {BTU Cottbus - Senftenberg}, year = {2019}, abstract = {Over the past seven decades Si microelectronics have developed rapidly. The success of the growing microelectronic industry is also caused by the expansion of materials in addition to Si. Open challenges are the monolithic integration of group IV devices on Si photonics as well as overcoming the size mismatch between electronic parts in the nm range and photonic parts in the µm scale. In this thesis the future application of GeSn NIs on Si as a photodetector is evaluated. The key element required for high performance optoelectronic devices is the formation of high-quality GeSn nano-islands (NIs), i.e. overcoming growth challenges such as introduction of defects due to lattice and thermal mismatch between GeSn and Si substrate as well as suppression of Sn precipitation caused by the limited solid solubility of Sn in Ge. To achieve high-quality nanostructures, the selective growth of GeSn NIs on Si(001) seeds via molecular beam epitaxy is investigated, exploiting the advantages of nanoheteroepitaxy (NHE), i.e. growth on nano-patterned substrates. The best compromise between selective growth of GeSn on Si nano-pillars at significant higher growth temperature than the eutectic temperature of GeSn and the incorporation of Sn into the Ge lattice was achieved at 600°C. X-ray diffraction studies confirmed the substitutional incorporation of 1.4at.\% Sn into the NIs avoiding considerable Si interdiffusion from the substrate. Transmission electron microscopy images have shown that dislocations and stacking faults caused by plastic relaxation of the GeSn NIs are located near the NIs/substrate interface and thus, dislocation-free GeSn NIs can be formed, due to gliding out of the threading arms triggered by the NHE approach. The high crystal quality of the GeSn NIs, enables the investigation of the bandgap by μ-photoluminescence (PL) analyses, demonstrating the shrinkage of the direct bandgap with increasing Sn content in the quasi-direct semiconductor. All NIs however feature a β-Sn droplet on their nano-facets. To suppress the out-diffusion of Sn and hence increase the Sn concentration of the GeSn alloy, the GeSn NIs were overgrown with a thin Ge cap layer. The Ge cap successfully hinders the formation of Sn segregates on top of the NIs. Capping at 600 °C and 650°C results in an enrichment of Sn at the surface, forming a GeSn crust with 8±0.5at.\% Sn. This wetting layer both enhances the optoelectronic properties of the NI core and exhibits a relatively strong PL emission attributed to direct radiative recombination. Finally, a first demonstration of a GeSn NIs based photodetector was successful, due to the utilization of Al nano-antennas exhibiting an enhanced light coupling into the GeSn NIs at a wavelength of 700nm. The responsible mechanisms is the local plasmonic field enhancement of the incoming light. The manipulation of the resonance wavelength into the telecommunication regime, i.e. >1550nm, have to be investigated in future studies.}, subject = {Group IV; Nanoheteroepitaxy; Photoluminescence; Selective growth; Gruppe IV; Nanoheteroepitaxie; Photolumineszenz; Selektives Wachstum; Germanium; Zinn; Silicium; Heteroepitaxie; Photodetektor}, language = {en} }