@article{66674, abstract = {{Efficient detection of near-infrared light at telecommunication wavelengths remains a central challenge for GaAs-based photonic and optoelectronic devices due to the absence of linear absorption below the bandgap. Here, we demonstrate a hybrid nonlinear optoelectronic device that enhances the detection efficiency of a (001)-oriented GaAs PIN photodiode under telecommunication-wavelength illumination, where absorption is intrinsically limited to two-photon absorption (2PA). Our approach relies on the integration of a transferred, nanopatterned 385 nm-thick (111)-oriented GaAs nanofilm acting as an on-chip nonlinear frequency-conversion layer. Elliptical GaAs nanoresonators are employed to enhance second-harmonic generation (SHG) resonantly, converting incident 1550 nm radiation into above-bandgap photons efficiently absorbed by the underlying diode. Spatially resolved current–voltage measurements reveal a pronounced enhancement of the detector response in regions covered by the nanoantennas. The device exhibits a low dark current, while the metasurface-covered regions show the largest current response under 1560 nm excitation compared to the bare GaAs(100) diode and the unstructured GaAs(111) film. These results establish a direct functional link between dielectric metasurface–based nonlinear frequency conversion and electrical photodetection, providing a viable route toward integrated sub-bandgap detection schemes.}}, author = {{Spedt, Vladimir and Meier, Falco and Geromel, René and Mahler, Pascal and Henksmeier, Tobias and Reuter, Dirk and Zentgraf, Thomas and Meier, Cedrik}}, issn = {{1094-4087}}, journal = {{Optics Express}}, number = {{16}}, publisher = {{Optica Publishing Group}}, title = {{{Hybrid GaAs (111)/GaAs (100) PIN photodiodes for metasurface-assisted nonlinear upconversion detection}}}, doi = {{10.1364/oe.601288}}, volume = {{34}}, year = {{2026}}, } @article{65611, abstract = {{ Spins confined in optically active quantum dot molecules (QDMs) can be used for the deterministic generation of photonic graph states with tailored entanglement structures. Their usefulness for the generation of such nonclassical states of light is determined by orbital and spin decoherence mechanisms, particularly phonon-mediated processes dominant at energy scales up to a few millielectronvolts. Here, we directly measure the spectral function of orbital phonon relaxation between the energy states of the neutral exciton in a QDM and benchmark our findings against microscopic k · p theory. Our results reveal pronounced resonances and antiresonances in the phonon-relaxation rates, ranging from tens of µ s − 1 up to tens of ns − 1 . Comparison with a kinetic model reveals the voltage (energy) dependent phonon coupling strength and fully explains the interplay between phonon-assisted relaxation and radiative recombination. The resonances and antiresonances enable further tunability of the exciton lifetime which can be leveraged to increase the lifetime of energetically unfavorable charge configurations needed for realizing efficient spin-photon interfaces and multidimensional cluster states. }}, author = {{Lienhart, Michelle and Gawarecki, Krzysztof and Stöcker, Markus and Bopp, Frederik and Cullip, Charlotte and Akhlaq, Nadeem and Thalacker, Christopher and Schall, Johannes and Rodt, Sven and Ludwig, Arne and Reuter, Dirk and Reitzenstein, Stephan and Müller, Kai and Machnikowski, Paweł and Finley, Jonathan J.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{23}}, publisher = {{American Physical Society (APS)}}, title = {{{Resonant and antiresonant exciton-phonon coupling in quantum dot molecules}}}, doi = {{10.1103/xc25-1tph}}, volume = {{112}}, year = {{2025}}, } @article{65669, abstract = {{Local droplet etching and subsequent refilling enables the fabrication of highly symmetric quantum dots with low fine structure splitting, suitable for generating polarization entangled photons. While well established in GaAs/AlxGa1−xAs, this approach does not yield emission in the telecom bands required for low loss fiber-based quantum communication. To achieve emission at 1.55 μm, local droplet etching must be adapted to alternative material platforms such as InP. Here, we systematically investigate how the etching material deposition rate and etching time influence nanohole morphology in In0.52Al0.48As layers lattice-matched to InP. In the first experiment, InAl was deposited at fluxes of 0.2–4.0 Å s−1 at Tetch = 350 °C and 460 °C. Lower fluxes produced nanoholes with lower density and larger ring diameters, indicating fewer and larger initial droplets, consistent with scaling theory. The average nanohole diameter decreased monotonically with increasing flux, whereas the average depth showed no clear dependence on flux. In the second experiment, etching times of 30–600 s were tested for InAl, In, and Al droplets. Average nanohole diameters remained constant for Al across all etching times, but decreased for In and InAl with increasing etching time, suggesting sidewall redeposition during etching. For all droplet types, depths peaked at intermediate times and decreased for prolonged etching, consistent with material diffusion into the nanohole after droplet consumption.}}, author = {{Deutsch, Dennis and Reuter, Dirk}}, issn = {{2073-4352}}, journal = {{Crystals}}, number = {{11}}, publisher = {{MDPI AG}}, title = {{{Influence of the Etching Material Deposition Rate and Annealing Time on Nanohole Morphology Etched into InP/In0.52Al0.48As Layers via Local Droplet Epitaxy}}}, doi = {{10.3390/cryst15110913}}, volume = {{15}}, year = {{2025}}, } @article{57553, author = {{Wijitpatima, Setthanat and Auler, Normen and Mudi, Priyabrata and Funk, Timon and Barua, Avijit and Shrestha, Binamra and Schall, Johannes and Limame, Imad and Rodt, Sven and Reuter, Dirk and Reitzenstein, Stephan}}, issn = {{1936-0851}}, journal = {{ACS Nano}}, number = {{46}}, pages = {{31834--31845}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Bright Electrically Contacted Circular Bragg Grating Resonators with Deterministically Integrated Quantum Dots}}}, doi = {{10.1021/acsnano.4c07820}}, volume = {{18}}, year = {{2024}}, } @article{57678, author = {{Henksmeier, Tobias and Reuter, Dirk}}, journal = {{Communications materials}}, title = {{{Low-temperature fabrication of amorphous carbon films as a universal template for remote epitaxy}}}, doi = {{10.48550/ARXIV.2410.15487}}, year = {{2024}}, } @article{57815, author = {{Karzel, Marek and Samusev, Anton K. and Linnik, Tetiana L. and Littmann, Mario and Reuter, Dirk and Bayer, Manfred and Scherbakov, Alexey V. and Akimov, Andrey V.}}, issn = {{2330-4022}}, journal = {{ACS Photonics}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Polariton-Induced Transparency in Multiple Quantum Wells Probed by Time Domain Brillouin Scattering}}}, doi = {{10.1021/acsphotonics.4c01357}}, year = {{2024}}, } @article{46133, author = {{Bopp, Frederik and Schall, Johannes and Bart, Nikolai and Vögl, Florian and Cullip, Charlotte and Sbresny, Friedrich and Boos, Katarina and Thalacker, Christopher and Lienhart, Michelle and Rodt, Sven and Reuter, Dirk and Ludwig, Arne and Wieck, Andreas D. and Reitzenstein, Stephan and Müller, Kai and Finley, Jonathan J.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{16}}, publisher = {{American Physical Society (APS)}}, title = {{{Coherent driving of direct and indirect excitons in a quantum dot molecule}}}, doi = {{10.1103/physrevb.107.165426}}, volume = {{107}}, year = {{2023}}, } @article{46132, author = {{Littmann, Mario and Reuter, Dirk and As, Donat Josef}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, keywords = {{Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, number = {{7}}, publisher = {{Wiley}}, title = {{{Remote Epitaxy of Cubic Gallium Nitride on Graphene‐Covered 3C‐SiC Substrates by Plasma‐Assisted Molecular Beam Epitaxy}}}, doi = {{10.1002/pssb.202300034}}, volume = {{260}}, year = {{2023}}, } @article{46278, abstract = {{Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture.}}, author = {{Feddersen, Stefan and Zolatanosha, Viktoryia and Alshaikh, Ahmed and Reuter, Dirk and Heyn, Christian}}, issn = {{2079-4991}}, journal = {{Nanomaterials}}, keywords = {{General Materials Science, General Chemical Engineering}}, number = {{3}}, publisher = {{MDPI AG}}, title = {{{Modeling of Masked Droplet Deposition for Site-Controlled Ga Droplets}}}, doi = {{10.3390/nano13030466}}, volume = {{13}}, year = {{2023}}, } @article{57677, abstract = {{We present the fabrication of strain-free quantum dots in the In0.53Ga0.47As/In0.52Al0.48As-system lattice matched to InP, as future sources for single and entangled photons for long-haul fiber-based quantum communication in the optical C-band. We achieved these quantum dots by local droplet etching via InAl droplets in an In0.52Al0.48As layer and subsequent filling of the holes with In0.53Ga0.47As. Here, we present detailed investigations of the hole morphologies measured by atomic force microscopy. Statistical analysis of a set of nanoholes reveals a high degree of symmetry for nearly half of them when etched at optimized temperatures. Overgrowth with 50–150 nm In0.52Al0.48As increases their diameter and elongates the holes along the [01̄1]-direction. By systematically scanning the parameter space, we were able to fill the holes with In0.53Ga0.47As, and by capping the filled holes and performing photoluminescence measurements, we observe photoluminescence emission in the O-band up into the C-band depending on the filling height of the nanoholes.}}, author = {{Deutsch, Dennis and Buchholz, C. and Zolatanosha, V. and Jöns, K. D. and Reuter, Dirk}}, issn = {{2158-3226}}, journal = {{AIP Advances}}, number = {{5}}, publisher = {{AIP Publishing}}, title = {{{Telecom C-band photon emission from (In,Ga)As quantum dots generated by filling nanoholes in In0.52Al0.48As layers}}}, doi = {{10.1063/5.0147281}}, volume = {{13}}, year = {{2023}}, } @inbook{29789, abstract = {{Die Studieneingangsphase Physik stellt für die Studienanfänger Innen einen komplexen Lernprozess mit vielfältigen Anforderungen auf fachlicher, Metakognitions- und Sozialisations-Ebene dar, der ihre akademische Identitätsbildung beeinflusst und prägt. Ziel des Projektes Paderborner Studieneingangsphase Physik (PSΦ) ist die evidenzbasierte Gestaltung eines strukturierten Studieneinstiegs und einer in sich kohärent abgestimmten Studieneingangsphase „aus einem Guss“. Die Implementation eines neuen Übungsformats (Präsenzübungen) in den Fachvorlesungen sowie die Unterstützung der Studierenden im Bereich des selbstregulierten Lernens zeigen positive Effekte in einer erhöhten Teilnahmequote sowie Zufriedenheit der Studierenden mit der Veranstaltung, in einem aktiveren Arbeitsverhalten sowie einer höheren Bestehensquote der Klausur. Ein messbar größerer Fachwissenserwerb konnte nicht nachgewiesen werden. Auf Basis der Evidenzen konnten Stellschrauben für die Weiterentwicklung sowie für die Unterstützung der Lehrenden abgeleitet werden. In dem Beitrag werden die Gelingensbedingungen und Strukturen für eine wirksame Zusammenarbeit von Fachdidaktik und Fachwissenschaft am Beispiel der Überarbeitung der Studieneingangsphase im Rahmen einer community of practice sowie der Wirksamkeit der Implementierung diskutiert.}}, author = {{Bauer, Anna and Woitkowski, David and Reuter, Dirk and Reinhold, Peter}}, booktitle = {{Hochschullehre erforschen. }}, editor = {{Fahr, Uwe and Kenner, Alessandra and Angenent, Holger and Eßer-Lüghausen, Alexandra}}, pages = {{339--362}}, publisher = {{Springer Fachmedien}}, title = {{{Fachliche und überfachliche Herausforderungen in der Studieneingangsphase Physik}}}, doi = {{10.1007/978-3-658-34185-5_19}}, year = {{2022}}, } @article{30743, author = {{Riedl, Thomas and Kunnathully, Vinay S. and Trapp, Alexander and Langer, Timo and Reuter, Dirk and Lindner, Jörg K. N.}}, issn = {{2196-7350}}, journal = {{Advanced Materials Interfaces}}, keywords = {{Mechanical Engineering, Mechanics of Materials}}, publisher = {{Wiley}}, title = {{{Size‐Dependent Strain Relaxation in InAs Quantum Dots on Top of GaAs(111)A Nanopillars}}}, doi = {{10.1002/admi.202102159}}, year = {{2022}}, } @article{30880, author = {{Kobecki, Michal and Scherbakov, Alexey V. and Kukhtaruk, Serhii M. and Yaremkevich, Dmytro D. and Henksmeier, Tobias and Trapp, Alexander and Reuter, Dirk and Gusev, Vitalyi E. and Akimov, Andrey V. and Bayer, Manfred}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, keywords = {{General Physics and Astronomy}}, number = {{15}}, publisher = {{American Physical Society (APS)}}, title = {{{Giant Photoelasticity of Polaritons for Detection of Coherent Phonons in a Superlattice with Quantum Sensitivity}}}, doi = {{10.1103/physrevlett.128.157401}}, volume = {{128}}, year = {{2022}}, } @article{32108, author = {{Henksmeier, T. and Schulz, J.F. and Kluth, E. and Feneberg, M. and Goldhahn, R. and Sanchez, A.M. and Voigt, M. and Grundmeier, Guido and Reuter, Dirk}}, issn = {{0022-0248}}, journal = {{Journal of Crystal Growth}}, keywords = {{Materials Chemistry, Inorganic Chemistry, Condensed Matter Physics}}, publisher = {{Elsevier BV}}, title = {{{Remote epitaxy of InxGa1-xAs (0 0 1) on graphene covered GaAs(0 0 1) substrates}}}, doi = {{10.1016/j.jcrysgro.2022.126756}}, volume = {{593}}, year = {{2022}}, } @article{31241, author = {{Verma, A.K. and Bopp, F. and Finley, J.J. and Jonas, B. and Zrenner, A. and Reuter, Dirk}}, issn = {{0022-0248}}, journal = {{Journal of Crystal Growth}}, keywords = {{Materials Chemistry, Inorganic Chemistry, Condensed Matter Physics}}, publisher = {{Elsevier BV}}, title = {{{Low Areal Densities of InAs Quantum Dots on GaAs(100) Prepared by Molecular Beam Epitaxy}}}, doi = {{10.1016/j.jcrysgro.2022.126715}}, year = {{2022}}, } @article{31541, author = {{Kobecki, Michal and Scherbakov, Alexey V. and Kukhtaruk, Serhii M. and Yaremkevich, Dmytro D. and Henksmeier, Tobias and Trapp, Alexander and Reuter, Dirk and Gusev, Vitalyi E. and Akimov, Andrey V. and Bayer, Manfred}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, keywords = {{General Physics and Astronomy}}, number = {{15}}, publisher = {{American Physical Society (APS)}}, title = {{{Giant Photoelasticity of Polaritons for Detection of Coherent Phonons in a Superlattice with Quantum Sensitivity}}}, doi = {{10.1103/physrevlett.128.157401}}, volume = {{128}}, year = {{2022}}, } @article{33332, author = {{Bopp, Frederik and Rojas, Jonathan and Revenga, Natalia and Riedl, Hubert and Sbresny, Friedrich and Boos, Katarina and Simmet, Tobias and Ahmadi, Arash and Gershoni, David and Kasprzak, Jacek and Ludwig, Arne and Reitzenstein, Stephan and Wieck, Andreas and Reuter, Dirk and Müller, Kai and Finley, Jonathan J.}}, issn = {{2511-9044}}, journal = {{Advanced Quantum Technologies}}, keywords = {{Electrical and Electronic Engineering, Computational Theory and Mathematics, Condensed Matter Physics, Mathematical Physics, Nuclear and High Energy Physics, Electronic, Optical and Magnetic Materials, Statistical and Nonlinear Physics}}, publisher = {{Wiley}}, title = {{{Quantum Dot Molecule Devices with Optical Control of Charge Status and Electronic Control of Coupling}}}, doi = {{10.1002/qute.202200049}}, year = {{2022}}, } @article{35232, author = {{Meier, Falco and Littmann, Mario and Bürger, Julius and Riedl, Thomas and Kool, Daniel and Lindner, Jörg and Reuter, Dirk and As, Donat Josef}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, keywords = {{Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, publisher = {{Wiley}}, title = {{{Selective Area Growth of Cubic Gallium Nitride in Nanoscopic Silicon Dioxide Masks}}}, doi = {{10.1002/pssb.202200508}}, year = {{2022}}, } @article{34056, abstract = {{ A process sequence enabling the large-area fabrication of nanopillar-patterned semiconductor templates for selective-area heteroepitaxy is developed. Herein, the nanopillar tops surrounded by a SiNx mask film serve as nanoscale growth areas. The molecular beam epitaxial growth of InAs on such patterned GaAs[Formula: see text]A templates is investigated by means of electron microscopy. It is found that defect-free nanoscale InAs islands grow selectively on the nanopillar tops at a substrate temperature of 425 °C. High-angle annular dark-field scanning transmission electron microscopy imaging reveals that for a growth temperature of 400 °C, the InAs islands show a tendency to form wurtzite phase arms extending along the lateral [Formula: see text] directions from the central zinc blende region of the islands. This is ascribed to a temporary self-catalyzed vapor–liquid–solid growth on [Formula: see text] B facets, which leads to a kinetically induced preference for the nucleation of the wurtzite phase driven by the local, instantaneous V/III ratio, and to a concomitant reduction of surface energy of the nanoscale diameter arms. }}, author = {{Riedl, Thomas and Kunnathully, Vinay S. and Verma, Akshay Kumar and Langer, Timo and Reuter, Dirk and Büker, Björn and Hütten, Andreas and Lindner, Jörg}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{18}}, publisher = {{AIP Publishing}}, title = {{{Selective area heteroepitaxy of InAs nanostructures on nanopillar-patterned GaAs(111)A}}}, doi = {{10.1063/5.0121559}}, volume = {{132}}, year = {{2022}}, } @article{34053, author = {{Riedl, Thomas and Kunnathully, Vinay and Trapp, Alexander and Langer, Timo and Reuter, Dirk and Lindner, Jörg}}, issn = {{2196-7350}}, journal = {{Advanced Materials Interfaces}}, keywords = {{Mechanical Engineering, Mechanics of Materials}}, number = {{11}}, publisher = {{Wiley}}, title = {{{Size‐Dependent Strain Relaxation in InAs Quantum Dots on Top of GaAs(111)A Nanopillars}}}, doi = {{10.1002/admi.202102159}}, volume = {{9}}, year = {{2022}}, }