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Dissertation / PhD Thesis | FZJ-2015-06112 |
2016
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-132-3
Please use a persistent id in citations: http://hdl.handle.net/2128/10112 urn:nbn:de:0001-2016063005
Abstract: Sn-based group IV semiconductors have attracted increasing scientific interest during the last decade due to their exciting electronic properties, such as a fundamental direct bandgap or high carrier mobility. Whereas these properties have been predicted already in the early 1980’s, the quality of epitaxially grown GeSn and SiGeSn layers on Si and Ge substrates has been limited owing to the low solid solubility of Sn in (Si)Ge (<1 at.%) and the large lattice mismatch (>15 %). Hence, the enormous potential of these material systems regarding its implementation in nano- and optoelectronics has not been exploited to date. A low temperature reduced pressure chemical vapour process using commercially available Ge- and Sn-precursors, namely Ge$_{2}$H$_{6}$ and SnCl$_{4}$, is developed for the growth of GeSn and SiGeSn epilayers directly on Si(001) and on Ge-buffered Si(001). Sn concentrations far beyond the solid solubility of Sn in (Si)Ge are achieved. High growth rates at low growth temperatures assure exceptionally high monocrystalline quality evidenced by exhaustive layer characterization, i.e. transmission electron microscopy, Rutherford backscattering spectrometry, X-ray diffraction or photoluminescence. Moreover, it is shown that the plastic strain relaxation of these (Si)GeSn epilayers on Ge/Si(001) takes place mostly via edge dislocations rather than via threading dislocations as well-known in other group IV systems, i.e. SiGe/Ge. Subsequently, dedicated heterostructures are used for admittance and optical characterization. Highly biaxially tensile strained Ge and GeSn layers grown on GeSn strain relaxed buffer layers are used to fabricate metal oxide semiconductor capacitors in order to investigate the interfacial quality between these narrow bandgap semiconductors and high-k dielectrics. For the investigation of the Nickel metallization process of GeSn and SiGeSn epilayers, Sn concentration above 10 at.% are used. Furthermore, the transition from an indirect to a fundamental direct group IV semiconductor is presented by means of temperature dependent PL measurements on a set of high Sn content GeSn epilayers. Strain relaxed GeSn layers with a Sn concentration of 12.6 at.% grown on Si(001) substrates exhibit high modal gain values at cryogenic temperatures. Finally, the first demonstration of lasing action in direct bandgap group IV Fabry-Perot cavities is presented.
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