@article{OleynikRyzhakSchlipfetal.2025, author = {Oleynik, Paul and Ryzhak, Diana and Schlipf, Jon and Alvarado Chavarin, Carlos and Yamamoto, Yuji and Berkmann, Fritz and Ratzke, Markus and Fischer, Inga Anita}, title = {Influence of illumination conditions on photoluminescence enhancement in an Al/Si/Ge metasurface}, series = {Optics Express}, volume = {34}, journal = {Optics Express}, number = {1}, publisher = {Optica Publishing Group}, address = {Washington D.C.}, issn = {1094-4087}, doi = {10.1364/OE.577751}, pages = {78 -- 86}, year = {2025}, abstract = {Strong field enhancement supported by metasurfaces at resonance can be used to control and enhance the spontaneous emission rate of emitters. This is particularly relevant for emitters with comparatively low quantum yield such as germanium. Here, we investigate the µ-photoluminescence response obtained from a hybrid metasurface comprising a square lattice of Al/Si/Ge pillars. We explore how variations in excitation energy, excitation intensity and number of excited meta-atoms affect the spectral dependence of the photoluminescence signal and, in particular, the contribution of the metasurface to it. Our metasurface exhibits a magnetic dipole collective lattice resonance, whose contribution to the photoluminescence signal increases with increasing number of excited meta-atoms. Measuring only one metasurface under different illumination conditions can potentially be an alternative approach to probe the transition between finite-size effects and collective effects.}, subject = {Field enhancement; Germanium; Light emitting diodes; Photonic crystals; Quantum light sources; Scanning electron microscop}, language = {en} } @article{SenguelReiterLotfietal.2025, author = {Seng{\"u}l, Akant and Reiter, Sebastian and Lotfi, Zahra and Efremenko, Julia and Laroussi, Arwa and Corley-Wiciak, Agnieszka Anna and Ratzke, Markus and Mirsky, Vladimir M. and Wenger, Christian and Fischer, Inga Anita}, title = {Titanium nitride plasmonic nanohole arrays with polymer coating : optical properties and their humidity-induced modifications}, series = {Optical Materials Express}, volume = {16}, journal = {Optical Materials Express}, number = {2}, publisher = {Optica Publishing Group}, address = {Washington D.C.}, issn = {2159-3930}, doi = {10.1364/OME.578871}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-72739}, pages = {184 -- 196}, year = {2025}, abstract = {The use of titanium nitride (TiN) for the fabrication of plasmonic structures such as nanohole arrays (NHAs) can enable their integration into optoelectronic devices on the silicon (Si) platform, for example, for the realization of on-chip chemical sensors and biosensors based on refractometric transduction. With a corresponding functionalization of the TiN nanohole arrays, these ultra-compact devices can be utilized in the development of various affinity sensors and sensor systems, such as cost-effective electronic noses for the early detection of gases in the food industry or agriculture. In this work, we focus on two types of coating for functionalization of TiN nanohole arrays: electrochemically synthesized poly-N-methylaniline and layer-by-layer deposited polyacrylic-acid/poly-allylamine (PAA/PAH). Our investigation comprises the experimental characterization of the optical properties of TiN nanhole arrays coated with polymer layers of different thicknesses as well as a comparison with simulation results. We demonstrate the potential of our setup sensing applications by measuring changes in optical properties of TiN nanohole arrays coated with PAA/PAH upon exposure to air of different humidity.}, subject = {Chemical sensors; Extraordinary optical transmission; Localized surface plasmon resonance; Optical coatings; Optical properties; Refractive index}, language = {en} } @phdthesis{PerezBoschQuesada2024, author = {Perez-Bosch Quesada, Emilio}, title = {In-depth electrical characterization of HfO₂-based memristive devices for their integration in CMOS-compatible neuromorphic systems}, doi = {10.26127/BTUOpen-6781}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-67815}, school = {BTU Cottbus - Senftenberg}, year = {2024}, abstract = {The rapid development of information and communication technologies is reaching critical limits that might compromise the global digitalization progress, one of the main economy pillars nowadays. Among others, limits like the end of Moore's law, derived from miniaturization issues in nano-scale devices; the need for massive data processing parallelization due to the ever-increasing amount of data generated in every single aspect of our daily routine; and the acute increase of the annual electricity consumption in data center due to energy inefficiency in their computational architectures. Therefore, the need for partial or complete migration of current computing paradigms towards more sustainable ones is of paramount importance to bypass these limits. Neuromorphic computing systems inspired by the neural and synaptic activity of the human brain irrupted as an innovative alternative to merge memory and computing units, traditionally separated following the von Neumann architecture. Emerging non-volatile memory technologies, specifically the Resistive Random Access Memory (RRAM) technology, are playing important roles in the development of new computing paradigms due to their outstanding properties, namely, fast switching, high scalability, long state retention and their multilevel-cell capabilities, among others. The later stands out as a key feature to increase memory densities at lower area cost and it lately gathered special interest concerning neuromorphic applications. Due to the uncertainty surrounding the stochastic processes governing the resistive switching of the RRAM technology, here is still scarce number of real RRAM-based hardware implementations. In this work, motivated by the impact of the inherent stochasticity of the RRAM technology on neuromorphic systems' performance, a thorough wafer-scale electrical characterization is carried out over HfO2-based RRAM devices to study their quasistatic response. Their non-idealities are identified, in a way that they could be modelled and potentially mitigated to enhance the memristive devices stability and thus, their performance carrying out multiply-accumulate (MAC) tasks, fundamental operations for the implementation of artificial intelligence (AI) applications. This characterization supports the adaptation of three physics-based compact models and an empirical study of vector-matrix multiplication (VMM) operations performed using real RRAM devices for neuromorphic applications. The impact of the devices' non-idealities on the final operation results is assessed along consecutive VMMs. This work sets the baseline of the quasistatic characterization of IHP's RRAM devices and opens the way towards real ardware neuromorphic systems with such technology.}, subject = {Vector-matrix multiplications,; Neuromorphic computing; RRAM; Non-volatile; Vektor-Matrix-Multiplikationen; RRAM; Neuromorphes Rechnen; Neuromorphing; Neuronales Netz; Resistive RAM}, language = {en} } @phdthesis{Schlipf2024, author = {Schlipf, J{\´o}n Benedikt}, title = {Enhancement of group-IV optoelectronic sensing devices through materials engineering and nanostructuring}, doi = {10.26127/BTUOpen-6797}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-67979}, school = {BTU Cottbus - Senftenberg}, year = {2024}, abstract = {Driven by the continuous research progress in integrated electronics towards increasing complexity and miniaturization, semiconductor technology has not only yielded very powerful electronic devices, but also provided the necessary tools for miniaturization of mechanical, optical and other functions into micro- and nanoscale devices. While transistor scaling approaches the physical limits mainly governed by heat dissipation, further advances are predicted to stem from the integration of additional functionality into integrated circuits instead. For the case of photonics and optoelectronics, which have plenty of applications in computing, communications and sensing, silicon devices have been applied commercially for several years. While being compatible with mainstream electronics, silicon does not offer the optimum properties for mediation between optics and electronics compared to, for example, III-V materials. To alleviate this, properties can be improved both through wavelength-scale structuring and exploitation of resonances, and through alloying with other group-IV materials like germanium and tin. Both of these avenues are studied within this work. On one hand, nanophotonic structures, most notably metasurfaces, and corresponding simulation and optimization algorithms, are developed for selective filtering and enhancement of light-matter interactions. On the other hand, group-IV materials are studied, most notably their non-destructive characterization with optical methods.}, subject = {Metasurface; Group-IV; Plasmonics; Photodetector; Nanophotonik; Plasmonik; Gruppe-IV-Materialien; Integrierte Schaltung; Nanophotonik; Plasmonik; Silicium; Germanium}, language = {en} } @phdthesis{Becker2023, author = {Becker, Lucas}, title = {The influence of the early relaxation phase on the threading dislocation density in strain relaxed Si₁₋ₓGeₓ buffer layers on Si(001) substrates}, doi = {10.26127/BTUOpen-6743}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-67431}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {The integration of germanium (Ge) on silicon (Si) for microelectronics applications requires strain-relaxed SiGe buffer layers (SRB) as virtual substrates. However, the presence of threading dislocations in these layers remains a challenge, as they can affect device performance. Existing methods achieve threading dislocation densities (TDD) around 1 x 10⁵ cm⁻², but a further reduction is desired for industrial applications. A SiGe backside deposition technique originally intended to compensate for wafer bowing surprisingly improves the TDD. The underlying physics remained poorly understood until now. In this work it is shown, that the SiGe backside deposition leads to a parasitic SiGe layer at the edge of the wafer. Partial relaxation of this layer generates dislocations, which fundamentally change the relaxation mechanism of subsequently deposited SiGe layers on the front side. These preexisting dislocations glide from the edge to the center of the wafer, preventing the formation of dislocation bundles and pile-ups. As a result, the TDD decreases significantly for layers with low Ge content. Adjusting the growth conditions and dislocation glide kinetics optimizes early relaxation, achieving a TDD reduction to 4x10⁴ cm⁻² for 25\% Ge buffer layers. Additionally, a novel ring deposition technique provides controlled preexisting dislocations at the wafer's edge, offering better control over the dislocation reservoir than uncontrolled parasitic deposition. Although initial results show promising results, further optimization is needed due to localized mechanical damage during processing. In summary, this research provides insights into strained SiGe layer relaxation, dislocation physics, and their impact on the TDD. By understanding these mechanisms, an enhancement of established buffer approach can be achieved and novel strategies for further TDD reduction can be developed.}, subject = {Silicon; Germanium; Epitaxy; Dislocation; Wafer; Silizium; Epitaxie; Versetzungen; Wafer; Wafer; Silicium; Epitaxie; Versetzung }, language = {en} } @phdthesis{Tetzner2023, author = {Tetzner, Henriette}, title = {Investigations of the electrical activity of defects in group IV and group III-N alloys integrated on Si substrates}, doi = {10.26127/BTUOpen-6681}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-66819}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {The hetero-integration of group IV and III-V epitaxial layers on silicon (Si) substrates enables novel devices for optoelectronic and high-power applications. However, lattice and thermal mismachtes lead to an unavoidable formation of defects in hetero-epitaxy. The consideration of these defects is important in semiconductor devices as they affect material properties and impair the device performances. Besides the structural characterization of the unintentional introduced defects and the question of it's origin, it is essential to evaluate their electrical activity in order to describe their impact on the device performance. This work explores the electrical activity of threading dislocations (TDs) in Ge-rich SiGe heterostructures integrated on Si substrates as well as the electrical active defects introduced by the growth of aluminium-nitride (AlN) seed layers for the integration of gallium-nitride (GaN) on Si substrates. I demonstrated a defect-related p-type conductivity of intrinsically grown Si ₀ ̣₀₆Ge ₀ ̣₉₄/Ge that reaffirms previous work of similar intrinsic Ge-based material. Moreover, I detailed the threading dislocation related leakage currents in rectifying devices, revealing a power law dependence on the threading dislocation density (TDD). By a variation of temperature I determined the dominant mechanism of transport of this leakage currents in different temperature regimes, for which I suggested possible interactions with TD related defect states. Through the reduction of leakage currents in the fabricated MOS capacitors I was able to examine an effective carrier concentration of 5-6x10¹⁵cm⁻³ in the nominally intrinsic Si ₀ ̣₀₆Ge ₀ ̣₉₄ epitaxial layer, which decreases down to 1x10¹⁵cm⁻³in the Ge buffer underneath. By applying deep level transient spectroscopy (DLTS) I found one dominant hole trap at mid-gap position confirming the presence of an TD-related effective generation-recombination center. In addition, I investigated the hole trapping kinetics of this defect level and associated it with point defects that are trapped in the strain field around threading dislocations. I obtained insights into defect formation in the Si substrate and at the AlN/Si interface in dependence of the AlN growth temperature. A low temperature growth step prevented a deep in-diffusion of Al atoms into the Si substrate with simultaneous increase of the maximal p-type doping in the vicinity of the AlN/Si interface. Furthermore, I found a bulk hole trap inside the Si substrate at mid-gap position that showed an increase in density by applying a low temperature growth step. In contrast, the defect states at the AlN/Si interface decreased when a low temperature growth step was applied, in comparison to AlN layers grown at continuous high temperatures.}, subject = {Silicon-germanium; Extended defects; Electrical active defects; Silizium-Germanium; Durchstoßversetzungen; Elektrisch aktive Defekte; DLTS; C-V; Siiicium; Germanium; MOS; Gitterbaufehler; Elektrischer Durchbruch}, language = {en} } @article{HanReiterSchlipfetal.2023, author = {Han, Weijia and Reiter, Sebastian and Schlipf, Jon and Mai, Christian and Spirito, Davide and Jose, Josmy and Wenger, Christian and Fischer, Inga A.}, title = {Strongly enhanced sensitivities of CMOS compatible plasmonic titanium nitride nanohole arrays for refractive index sensing under oblique incidence}, series = {Optics Express}, volume = {31}, journal = {Optics Express}, number = {11}, publisher = {Optica Publishing Group}, address = {Washington, DC}, issn = {1094-4087}, doi = {10.1364/OE.481993}, pages = {17389 -- 17407}, year = {2023}, abstract = {Titanium nitride (TiN) is a complementary metal-oxide-semiconductor (CMOS) compatible material with large potential for the fabrication of plasmonic structures suited for device integration. However, the comparatively large optical losses can be detrimental for application. This work reports a CMOS compatible TiN nanohole array (NHA) on top of a multilayer stack for potential use in integrated refractive index sensing with high sensitivities at wavelengths between 800 and 1500 nm. The stack, consisting of the TiN NHA on a silicon dioxide (SiO2) layer with Si as substrate (TiN NHA/SiO2/Si), is prepared using an industrial CMOS compatible process. The TiN NHA/SiO2/Si shows Fano resonances in reflectance spectra under oblique excitation, which are well reproduced by simulation using both finite difference time domain (FDTD) and rigorous coupled-wave analysis (RCWA) methods. The sensitivities derived from spectroscopic characterizations increase with the increasing incident angle and match well with the simulated sensitivities. Our systematic simulation-based investigation of the sensitivity of the TiN NHA/SiO2/Si stack under varied conditions reveals that very large sensitivities up to 2305 nm per refractive index unit (nm RIU-1) are predicted when the refractive index of superstrate is similar to that of the SiO2 layer. We analyze in detail how the interplay between plasmonic and photonic resonances such as surface plasmon polaritons (SPPs), localized surface plasmon resonances (LSPRs), Rayleigh Anomalies (RAs), and photonic microcavity modes (Fabry-P{\´e}rot resonances) contributes to this result. This work not only reveals the tunability of TiN nanostructures for plasmonic applications but also paves the way to explore efficient devices for sensing in broad conditions.}, subject = {TiN; Plasmonics; Plasmonik; Plasmonik; Photonik; Titannitrid; Plasmonics; Photonics}, language = {en} } @phdthesis{Reichmann2022, author = {Reichmann, Felix}, title = {Germanium, Zinn und (Zink-) Galliumoxid f{\"u}r fortschrittliche Mikro- und Optoelektronik : Einblicke in die elektronische Struktur der Oberfl{\"a}che mit Photoemissionstechniken}, doi = {10.26127/BTUOpen-6208}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-62080}, school = {BTU Cottbus - Senftenberg}, year = {2022}, abstract = {Historically, Ge is one of the oldest materials in the semiconductor industry and its (001) surface has been the subject of extensive investigations by photoelectron spectroscopy. I am going to challenge the predominant attribution of a semi-conducting nature of the Ge(001) surface in this thesis. My investigations reveal the presence of a Ge(001) surface state above the Fermi-level, occupied at room temperature. Employing time- and temperature-dependent angle-resolved photoelectron spectroscopy, I will demonstrate that the presence of this surface state is evidence for the conducting nature of the surface at room temperature. Sparked by the remarkable properties of the GeSn-alloy and a trend towards Ge-Sn-related multiquantum well fabrication, I investigate the surface electronic structure of Ge(001) after adsorption and incorporation of Sn. With an in-depth analysis of surface core-level shifts, I will extend the growth model of the Sn wetting layer formation by also detailing structural changes in the subsurface region. At the same time, the modifications of the electronic structure will be detailed, observing the removal of the Ge(001) surface states, the creation of a new, Sn-related surface state and the initial stages of the Schottky barrier formation. β-Ga₂O₃ a transparent semi-conducting oxide that has sparked a lot of interest over the last decade, because it offers an ultra-wide band gap and high break down voltage. However, due to its monoclinic crystal structure, device fabrication is rather challenging and researchers are already looking into alternative materials. One of these candidates is ϵ-Ga₂O₃ and this work presents a combined study by photoelectron spectroscopy and ab initio calculations of its electronic structure. (Hard) X-rays reveal the impact of photoelectron recoil and the absence of a band bending to the surface, while the dispersion of experimentally determined valence states compares favorably with the calculations based on hybrid density-functional theory. Another alternative to β-Ga₂O₃ be ZnGa₂O₄ and I will present an investigation on the electronic structure of its (100) surface. Due to the novelty of ZnGa₂O₄ single-crystals, I am first going to explore the preparation of a clean and well-ordered surface by standard in-situ sputtering and annealing. I will show that already low annealing temperatures induce Zn-deficiency, leading to non-stoichiometric surfaces, further exacerbated by sputtering. By changing the sputtering parameters and the annealing conditions, the preparation of a surface with sufficient quality for subsequent investigations will be demonstrated. The results by photoemission techniques compare favorably with the expectations from theory and allowing the first fundamental insights into the surface electronic structure.}, subject = {Angle-resolved photoemission spectroscopy; X-ray photoelectron spectroscopy; Germanium-tin; Zinc gallium oxide; Surface science; ARPES; Gallium-Zink-Oxid; XPS; Halbleiteroberfl{\"a}che; Bandstruktur; Elektronenstruktur; Germaniumverbindungen; Galliumverbindungen; ARPES; R{\"o}ntgen-Photoelektronenspektroskopie}, language = {en} } @phdthesis{Yang2020, author = {Yang, Penghui}, title = {Impact of alkali treatments on the surface and interface properties of Chalcopyrite thin-film solar cell absorbers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-51772}, school = {BTU Cottbus - Senftenberg}, year = {2020}, abstract = {This thesis focuses on the investigation and characterization of the surfaces and interfaces of chalcopyrite-based Cu(In,Ga)Se2 (CIGSe) thin film solar cells using various x-ray and electron spectroscopies. In particular, the impact of alkali post deposition treatments (PDT) on the chemical and electronic surface and interface structure of CdS/CIGSe absorbers is studied. The structure of "real world" CdS/CIGSe interfaces and how they are impacted by different alkali PDTs was investigated by a combination of different x-ray spectroscopies. The interface formation is characterized by studying sample sets with different CdS thicknesses. The chemical environment for indium and cadmium is revealed by deriving the modified Auger parameter α'(In) and α'(Cd) using the kinetic energy of most prominent Auger line together with the binding energy of the chosen core level. A more complex situation is found for CdS/CIGSe samples that underwent NaF+KF PDT, where a K-In-Se compound is initially present on top of the chalcopyrite absorber. The conversion of the K-In-Se type species into a Cd-In-(O,OH,S,Se) interface compound is recorded at short CBD-CdS deposition times. It appears the majority of K that is present at the surface of the NaF+KF PDT CIGSe absorber is dissolved in the CBD and partially re-deposited as K-O type species. The Cd/S ratio clearly deviates from the stoichiometry expected for CdS, and a Cd(O,OH,S)-like compound is likely formed. The electronic structure of CdS/CIGSe interface is similarly more complex for the NaF+KF PDT compared to the NaF PDT case, where only Cd(O,OH,S) buffer was formed. In an attempt to shed more light into this complex situation, the impact of evaporated alkali metals (K, Rb, Cs) on the surface structure of CIGSe was studied in-system by synchrotron-based hard x- ray photoelectron spectroscopy (HAXPES), aiming at understanding the underlying mechanism of the interfacial effect of alkalis on the performance of CIGSe devices. In the case of K deposition, two K species are observed by x-ray absorption near-edge structure (XANES) and HAXPES, one of which species disappears at high annealing temperature. Furthermore, three new In contributions (In-O and K-In-Se, metallic In species) can be observed after K evaporation. The evolution of chemical contribution supports the formation of a K-In-Se and Cu-poor CIGSe (1:3:5) bilayer structure that is similar to what was reported for "real world" NaF+KF PDTs. Deposition of heavy alkali metals (Rb, Cs) induced the formation of alkali selenide phases after alkali evaporation and during low temperature annealing. Similar chemical changes as seen for the K composition (i.e. presence of metallic In, In-O, and alkali-O) are observed. However, detailed analysis of the Alk/Se ratio and composition provide direct evidence for the formation of a Alk-(In)-Se and (Cu,Alk)(In, Ga)Se2 bilayer. The insights from these studies promise to provide crucial aid to fully exploit alkali pre-treatments in scientific and industrial CIGSe production, and will deliberate use of this means of surface/interface tailoring to push efficiencies even further.}, subject = {Alkali PDT; Surface; Interface; Grenzfl{\"a}chen; Alkali-Nachbehandlungen; Oberfl{\"a}chen; CIGSe; Solarzelle; Oberfl{\"a}che; Alkalien; Grenzfl{\"a}che}, language = {en} } @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} }