05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
Browse
10 results
Search Results
Item Open Access Sharp MIR plasmonic modes in gratings made of heavily doped pulsed laser-melted Ge1-xSnx(2023) Berkmann, Fritz; Steuer, Oliver; Ganss, Fabian; Prucnal, Slawomir; Schwarz, Daniel; Fischer, Inga Anita; Schulze, JörgItem Open Access Ge(Sn) nano-island/Si heterostructure photodetectors with plasmonic antennas(2020) Schlykow, Viktoria; Manganelli, Costanza Lucia; Römer, Friedhard; Clausen, Caterina; Augel, Lion; Schulze, Jörg; Katzer, Jens; Schubert, Michael Andreas; Witzigmann, Bernd; Schroeder, Thomas; Capellini, Giovanni; Fischer, Inga AnitaWe report on photodetection in deep subwavelength Ge(Sn) nano-islands on Si nano-pillar substrates, in which self-aligned nano-antennas in the Al contact metal are used to enhance light absorption by means of local surface plasmon resonances. The impact of parameters such as substrate doping and device geometry on the measured responsivities are investigated and our experimental results are supported by simulations of the three-dimensional distribution of the electromagnetic fields. Comparatively high optical responsivities of about 0.1 A W-1 are observed as a consequence of the excitation of localized surface plasmons, making our nano-island photodetectors interesting for applications in which size reduction is essential.Item Open Access Plasmonic gratings from highly doped Ge1-ySny films on Si(2021) Berkmann, Fritz; Ayasse, Markus; Schlipf, Jon; Mörz, Florian; Weißhaupt, David; Oehme, Michael; Prucnal, Slawomir; Kawaguchi, Yuma; Schwarz, Daniel; Fischer, Inga Anita; Schulze, JörgPlasmonic modes in metal structures are of great interest for optical applications. While metals such as Au and Ag are highly suitable for such applications at visible wavelengths, their high Drude losses limit their usefulness at mid-infrared wavelengths. Highly n-doped Ge1-ySny alloys are interesting possible alternative materials for plasmonic applications in this wavelength range. Here, we investigate the use of highly n-doped Ge1-ySny films grown directly on Si by molecular beam epitaxy with varying Sn-content from 0% up to 7.6% for plasmonic grating structures. We compare plasma wavelengths and relaxation times obtained from electrical and optical characterization. While theoretical considerations indicate that the decreasing effective mass with increasing Sn content in Ge1-ySny films could improve performance for plasmonic applications, our optical characterization results show that the utilization of Ge1-ySny films grown directly on Si is only beneficial if material quality can be improved.Item Open Access Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting(2022) Steuer, Oliver; Schwarz, Daniel; Oehme, Michael; Schulze, Jörg; Mączko, Herbert; Kudrawiec, Robert; Fischer, Inga A.; Heller, René; Hübner, René; Khan, Muhammad Moazzam; Georgiev, Yordan M.; Zhou, Shengqiang; Helm, Manfred; Prucnal, SlawomirThe pseudomorphic growth of Ge1-xSnx on Ge causes in-plane compressive strain, which degrades the superior properties of the Ge1-xSnx alloys. Therefore, efficient strain engineering is required. In this article, we present strain and band-gap engineering in Ge1-xSnx alloys grown on Ge a virtual substrate using post-growth nanosecond pulsed laser melting (PLM). Micro-Raman and x-ray diffraction (XRD) show that the initial in-plane compressive strain is removed. Moreover, for PLM energy densities higher than 0.5 J cm-2, the Ge0.89Sn0.11 layer becomes tensile strained. Simultaneously, as revealed by Rutherford Backscattering spectrometry, cross-sectional transmission electron microscopy investigations and XRD the crystalline quality and Sn-distribution in PLM-treated Ge0.89Sn0.11 layers are only slightly affected. Additionally, the change of the band structure after PLM is confirmed by low-temperature photoreflectance measurements. The presented results prove that post-growth ns-range PLM is an effective way for band-gap and strain engineering in highly-mismatched alloys.Item Open Access Photonic-plasmonic mode coupling in nanopillar Ge-on-Si PIN photodiodes(2021) Augel, Lion; Schlipf, Jon; Bullert, Sergej; Bürzele, Sebastian; Schulze, Jörg; Fischer, Inga A.Incorporating group IV photonic nanostructures within active top-illuminated photonic devices often requires light-transmissive contact schemes. In this context, plasmonic nanoapertures in metallic films can not only be realized using CMOS compatible metals and processes, they can also serve to influence the wavelength-dependent device responsivities. Here, we investigate crescent-shaped nanoapertures in close proximity to Ge-on-Si PIN nanopillar photodetectors both in simulation and experiment. In our geometries, the absorption within the devices is mainly shaped by the absorption characteristics of the vertical semiconductor nanopillar structures (leaky waveguide modes). The plasmonic resonances can be used to influence how incident light couples into the leaky modes within the nanopillars. Our results can serve as a starting point to selectively tune our device geometries for applications in spectroscopy or refractive index sensing.Item Open Access Continuous-wave electrically pumped multi-quantum-well laser based on group-IV semiconductors(2024) Seidel, Lukas; Liu, Teren; Concepción, Omar; Marzban, Bahareh; Kiyek, Vivien; Spirito, Davide; Schwarz, Daniel; Benkhelifa, Aimen; Schulze, Jörg; Ikonic, Zoran; Hartmann, Jean-Michel; Chelnokov, Alexei; Witzens, Jeremy; Capellini, Giovanni; Oehme, Michael; Grützmacher, Detlev; Buca, DanOver the last 30 years, group-IV semiconductors have been intensely investigated in the quest for a fundamental direct bandgap semiconductor that could yield the last missing piece of the Si Photonics toolbox: a continuous-wave Si-based laser. Along this path, it has been demonstrated that the electronic band structure of the GeSn/SiGeSn heterostructures can be tuned into a direct bandgap quantum structure providing optical gain for lasing. In this paper, we present a versatile electrically pumped, continuous-wave laser emitting at a near-infrared wavelength of 2.32 µm with a low threshold current of 4 mA. It is based on a 6-periods SiGeSn/GeSn multiple quantum-well heterostructure. Operation of the micro-disk laser at liquid nitrogen temperature is possible by changing to pulsed operation and reducing the heat load. The demonstration of a continuous-wave, electrically pumped, all-group-IV laser is a major breakthrough towards a complete group-IV photonics technology platform.Item Open Access Volatile MoS2 memristors with lateral silver Ion migration for artificial neuron applications(2025) Cruces, Sofía; Ganeriwala, Mohit Dineshkumar; Lee, Jimin; Völkel, Lukas; Braun, Dennis; Grundmann, Annika; Ran, Ke; González Marín, Enrique; Kalisch, Holger; Heuken, Michael; Vescan, Andrei; Mayer, Joachim; Godoy, Andrés; Daus, Alwin; Lemme, Max ChristianLayered 2D semiconductors have shown enhanced ion migration capabilities along their van der Waals (vdW) gaps and on their surfaces. This effect can be employed for resistive switching (RS) in devices for emerging memories, selectors, and neuromorphic computing. To date, all lateral molybdenum disulfide (MoS2)‐based volatile RS devices with silver (Ag) ion migration have been demonstrated using exfoliated, single‐crystal MoS2 flakes requiring a forming step to enable RS. Herein, present volatile RS with multilayer MoS2 grown by metal‐organic chemical vapor deposition (MOCVD) with repeatable forming‐free operation is presented. The devices show highly reproducible volatile RS with low operating voltages of ≈2 V and fast‐switching times down to 130 ns considering their micrometer‐scale dimensions. The switching mechanism is investigated based on Ag ion surface migration through transmission electron microscopy, electronic transport modeling, and density functional theory. Finally, a physics‐based compact model is developed and the implementation of the volatile memristors as artificial neurons in neuromorphic systems is exploredd.Item Open Access Ge-on-Si single-photon avalanche diode using a double mesa structure(2024) Wanitzek, Maurice; Schulze, Jörg; Oehme, MichaelItem Open Access Threshold switching in vertically aligned MoS2/SiOx heterostructures based on silver ion migration(2025) Lee, Jimin; Ahmad, Rana Walied; Cruces, Sofía; Braun, Dennis; Völkel, Lukas; Ran, Ke; Maroufidis Andreadis, Vasileios; Mayer, Joachim; Menzel, Stephan; Daus, Alwin; Lemme, Max C.Threshold switching (TS) is a non-permanent change in electrical resistance controlled by voltage modulation in two-terminal devices. Silver (Ag) filament-based TS has been observed in two-dimensional transition metal dichalcogenides, which are promising due to their van der Waals gaps, facilitating ion migration and filament formation without disturbing covalent bonds. This work demonstrates the heterostructure growth of vertically aligned molybdenum disulfide (VAMoS2) with an amorphous silicon oxide (SiOx) layer after sulfurization. Ag ion migration through this material stack enables TS. Our Ag/SiOx/VAMoS2/Au devices exhibit low switching voltages of ~0.63 V, high on-state currents over 200 μA, and stable switching exceeding 10⁴ cycles. A physics-based dynamical model identifies two rate-limiting steps for filament formation, and the simulated switching kinetics align with experimental results. Our devices achieve fast switching in 311 ns and spontaneous relaxation in 233 ns. These findings advance understanding of switching mechanisms and highlight their potential for memory and neuromorphic computing applications.Item Open Access Fabrication and characterization of n-type Ge1-xSnx- and Si1-x-yGeySnx-on-SOI junctionless transistors(2025) Steuer, Oliver; Ghosh, Sayantan; Schwarz, Daniel; Oehme, Michael; Lehmann, Sebastian; Hübner, René; Fowley, Ciarán; Erbe, Artur; Zhou, Shengqiang; Helm, Manfred; Cuniberti, Gianaurelio; Prucnal, Slawomir; Georgiev, Yordan M.AbstractGe1-xSnx and Si1-x-yGeySnx alloys are promising materials for future nanoelectronic applications owing to their high carrier mobilities and CMOS compatibility. However, ternary Si1-x-yGeySnx transistors have only theoretically been discussed, and there are only a few reports on lateral n-type Ge1-xSnx transistors to benchmark their material performance. The low equilibrium solid solubility of Sn in Si1-xGex (less than 1 at%) requires device fabrication processes at temperatures below the growth temperature of Si1-x-yGeySnx (x > equilibrium solubility) or at non-equilibrium conditions. Therefore, Si-based processes need to be adjusted according to the materials requirements. A relatively easy-to-fabricate device concept are junctionless field effect transistors, which operate as a gated resistor. In this work, we use Ge0.94Sn0.06 and Si0.14Ge0.80Sn0.06 grown on silicon-on-insulator substrates to fabricate and characterize lateral n-type Ge1-xSnx and SiyGe1-x-ySnx junctionless field effect transistors. The transistors were structurally characterized by top-view scanning electron microscopy and cross-sectional transmission electron microscopy. Electrical characterizations by transfer characteristics show the first working n-type Ge1-xSnx and Si1-x-yGeySnx hetero-nanowire transistors, achieving on/off-current ratios of up to eight orders of magnitude.