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544 results on '"Weyers, Markus"'

1. Telecom-Band SPDC in AlGaAs-on-Insulator Waveguides

Author

Placke, Marlon, Schlegel, Jan, Mann, Felix, Della Casa, Pietro, Thies, Andreas, Weyers, Markus, Tränkle, Günther, and Ramelow, Sven

Subjects
Quantum Physics, Physics - Optics
Abstract

Widespread commercial adoption of telecom-band quantum-key-distribution (QKD) will require fully integrated, room-temperature transmitters. Implementing highly efficient spontaneous parametric down-conversion (SPDC) on a platform that offers co-integration of the pump laser has been an outstanding challenge. Here, using such a platform based on AlGaAs-on-insulator waveguides, we report telecom-band SPDC (and second harmonic generation) with exceedingly large efficiencies of 26 GHz generated pairs/mW over a 7 THz bandwidth, which would saturate the usable photon-flux for a 70-channel wavelength-multiplexed QKD-system at merely 1.6 mW of pump laser power.

Published
2023

2. AlGaN/AlN heterostructures: an emerging platform for nonlinear integrated photonics

Author

Gündogdu, Sinan, Pazzagli, Sofia, Pregnolato, Tommaso, Kolbe, Tim, Hagedorn, Sylvia, Weyers, Markus, and Schröder, Tim

Subjects
Physics - Optics, Physics - Applied Physics
Abstract

In the rapidly evolving area of integrated photonics, there is a growing need for materials that satisfy the particular requirements of increasingly complex and specialized devices and applications. Present photonic material platforms have made significant progress over the past years; however, each platform still faces specific material and performance challenges. We introduce a novel material for integrated photonics: Aluminum Gallium Nitride (AlGaN) on Aluminum Nitride (AlN) as a platform for developing reconfigurable and nonlinear on-chip optical systems. AlGaN combines compatibility with standard semiconductor fabrication technologies, high electro-optic modulation capabilities, and large nonlinear coefficients while providing a broad and low-loss spectral transmission range, making it a viable material for advanced photonic applications. In this work, we design and grow AlGaN/AlN heterostructures and integrate fundamental photonic building blocks into these chips. In particular, we fabricate edge couplers, low-loss waveguides, directional couplers, and tunable high-quality factor ring resonators to enable nonlinear light-matter interaction and quantum functionality. The comprehensive platform we present in this work paves the way for nonlinear photon-pair generation applications, on-chip nonlinear quantum frequency conversion, and fast electro-optic modulation for switching and routing classical and quantum light fields.

Published
2023

4. Carbon doping of GaN: Proof of the formation of electrically active tri-carbon defects

Author

Gamov, Ivan, Richter, Eberhard, Weyers, Markus, Gärtner, Günter, Irmscher, Klaus, Kristallzüchtung, Leibniz-Institut für, Berlin, Germany, Ferdinand-Braun-Institut, Höchstfrequenztechnik, Leibniz-Institut für, Physics, Institute of Experimental, Freiberg, TU Bergakademie, and Freiberg

Subjects
Condensed Matter - Materials Science
Abstract

Carbon doping is used to obtain semi-insulating GaN crystals. If the carbon doping concentration exceeds $5*10^{17}$ $cm^{-3}$, the carbon atoms increasingly form triatomic clusters. The tri-carbon defect structure is unambiguously proven by the isotope effect on the defects' local vibrational modes (LVMs) originally found in samples containing carbon of natural isotopic composition $(~99 $%$ ^{12}C, ~1$%$ ^{13}C)$ at $1679$ $cm^{-1}$ and $1718$ $cm^{-1}$. Number, spectral positions, and intensities of the LVMs for samples enriched with the $^{13}C$ isotope (~99 % and ~50 %) are consistently interpreted on the basis of the harmonic oscillator model taking into account the probability of possible isotope combinations. Including the polarization dependence of the LVM absorption, we show that the tri-carbon defects form a triatomic molecule-like structure in two crystallographically different configurations: a basal configuration with the carbon bonds near the basal plane and an axial configuration with one of the carbon bonds along the c-axis. Finally, the disappearance of the LVMs under additional below-bandgap illumination is interpreted as defect recharging, i.e. the tri-carbon defects possess at least one charge state transition level within the bandgap and contribute to optical absorption as well as to the electrical charge balance.

Published
2020
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8. Prospects of far-UVC LED technology

Author

Kneissl, Michael, primary, Cardinali, Giulia, additional, Guttmann, Martin, additional, Muhin, Anton, additional, Schilling, Marcel, additional, Sulmoni, Luca, additional, Wernicke, Tim, additional, Cho, Hyun-Kyong, additional, Glaab, Johannes, additional, Kolbe, Tim, additional, Ruschel, Jan, additional, Hagedorn, Sylvia, additional, Lobo-Ploch, Neysha, additional, Netzel, Carsten, additional, Rass, Jens, additional, Einfeldt, Sven, additional, and Weyers, Markus, additional

Published
2024
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9. Author Correction: Skin tolerant inactivation of multiresistant pathogens using far-UVC LEDs

Author

Glaab, Johannes, Lobo‑Ploch, Neysha, Cho, Hyun Kyong, Filler, Thomas, Gundlach, Heiko, Guttmann, Martin, Hagedorn, Sylvia, Lohan, Silke B., Mehnke, Frank, Schleusener, Johannes, Sicher, Claudia, Sulmoni, Luca, Wernicke, Tim, Wittenbecher, Lucas, Woggon, Ulrike, Zwicker, Paula, Kramer, Axel, Meinke, Martina C., Kneissl, Michael, Weyers, Markus, Winterwerber, Ulrike, and Einfeldt, Sven

Published
2022
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13. Group III-Nitride-Based UV Laser Diodes

Author

Wernicke, Tim, Sulmoni, Luca, Kuhn, Christian, Tränkle, Günther, Weyers, Markus, Kneissl, Michael, von Klitzing, Klaus, Series Editor, Merlin, Roberto, Series Editor, Queisser, Hans-Joachim, Series Editor, Keimer, Bernhard, Series Editor, Gulian, Armen, Series Editor, Rogge, Sven, Series Editor, Kneissl, Michael, editor, Knorr, Andreas, editor, Reitzenstein, Stephan, editor, and Hoffmann, Axel, editor

Published
2020
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14. Skin tolerant inactivation of multiresistant pathogens using far-UVC LEDs

Author

Glaab, Johannes, Lobo-Ploch, Neysha, Cho, Hyun Kyong, Filler, Thomas, Gundlach, Heiko, Guttmann, Martin, Hagedorn, Sylvia, Lohan, Silke B., Mehnke, Frank, Schleusener, Johannes, Sicher, Claudia, Sulmoni, Luca, Wernicke, Tim, Wittenbecher, Lucas, Woggon, Ulrike, Zwicker, Paula, Kramer, Axel, Meinke, Martina C., Kneissl, Michael, Weyers, Markus, Winterwerber, Ulrike, and Einfeldt, Sven

Published
2021
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15. Imaging Threading Dislocations and Surface Steps in Nitride Thin Films Using Electron Backscatter Diffraction

Author

Hiller, Kieran P, primary, Winkelmann, Aimo, additional, Hourahine, Ben, additional, Starosta, Bohdan, additional, Alasmari, Aeshah, additional, Feng, Peng, additional, Wang, Tao, additional, Parbrook, Peter J, additional, Zubialevich, Vitaly Z, additional, Hagedorn, Sylvia, additional, Walde, Sebastian, additional, Weyers, Markus, additional, Coulon, Pierre-Marie, additional, Shields, Philip A, additional, Bruckbauer, Jochen, additional, and Trager-Cowan, Carol, additional

Published
2023
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18. Origin of the parasitic luminescence of 235 nm UVC LEDs grown on different AlN templates.

Author

Hagedorn, Sylvia, Kolbe, Tim, Schmidt, Gordon, Bertram, Frank, Netzel, Carsten, Knauer, Arne, Veit, Peter, Christen, Jürgen, and Weyers, Markus

Subjects
SCANNING transmission electron microscopy, LIGHT emitting diodes, LUMINESCENCE, POINT defects, CATHODOLUMINESCENCE
Abstract

AlN layers annealed at high temperatures offer low threading dislocation densities of mid 108 cm−2 and are therefore increasingly used as base layers in ultraviolet (UV) light emitting diode (LED) heterostructure growth. These LEDs, just like those grown on conventional metalorganic vapor phase epitaxy (MOVPE) AlN templates, often suffer from long-wavelength parasitic luminescence. In this work, luminescence properties of far-UVC LED heterostructures grown on MOVPE-AlN/sapphire templates and high-temperature annealed AlN/sapphire templates are compared. To investigate the origin of parasitic emission with high spatial resolution, cross section scanning transmission electron microscopy was combined with cathodoluminescence measurements. As a result, the main origin of the parasitic luminescence band centered at 3.5 eV (354 nm) for the heterostructure grown on annealed AlN is assigned to point defects related to oxygen in the AlN template layer. The defect band centered at 3.0 eV (413 nm) for the heterostructure grown on MOVPE-AlN was found to be related to self-compensating VAl-Si point defect complexes in the n-AlGaN layer and oxygen incorporation close to the AlN/sapphire interface. The results also suggest that the type of AlN template determines the kind of parasitic luminescence from the n-AlGaN layer. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Temperature-dependent electroluminescence of stressed and unstressed InAlGaN multi-quantum well UVB LEDs

Author

Höpfner, Jakob, primary, Gupta, Priti, additional, Guttmann, Martin, additional, Ruschel, Jan, additional, Glaab, Johannes, additional, Kolbe, Tim, additional, Rass, Jens, additional, Knauer, Arne, additional, Stölmacker, Christoph, additional, Einfeldt, Sven, additional, Wernicke, Tim, additional, Weyers, Markus, additional, and Kneissl, Michael, additional

Published
2023
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26. Solar- and Visible-Blind AlGaN Photodetectors

Author

Brendel, Moritz, Pertzsch, Enrico, Abrosimova, Vera, Trenkler, Torsten, Weyers, Markus, Hull, Robert, Series editor, Jagadish, Chennupati, Series editor, Kawazoe, Yoshiyuki, Series editor, Osgood, Richard M., Series editor, Parisi, Jürgen, Series editor, Seong, Tae-Yeon, Series editor, Uchida, Shin-ichi, Series editor, Wang, Zhiming M., Series editor, Kneissl, Michael, editor, and Rass, Jens, editor

Published
2016
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27. Vapor Phase Epitaxy of AlGaN Base Layers on Sapphire Substrates for Nitride-Based UV-Light Emitters

Author

Richter, Eberhard, Hagedorn, Sylvia, Knauer, Arne, Weyers, Markus, Hull, Robert, Series editor, Jagadish, Chennupati, Series editor, Kawazoe, Yoshiyuki, Series editor, Osgood, Richard M., Series editor, Parisi, Jürgen, Series editor, Seong, Tae-Yeon, Series editor, Uchida, Shin-ichi, Series editor, Wang, Zhiming M., Series editor, Kneissl, Michael, editor, and Rass, Jens, editor

Published
2016
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28. Femtosecond Mode-Locked Semiconductor Disk Lasers

Author

Griebner, Uwe, Klopp, Peter, Zorn, Martin, Weyers, Markus, Rhodes, William T., Editor-in-chief, Adibi, Ali, Series editor, Hänsch, Theodor W., Series editor, Krausz, Ferenc, Series editor, Masters, Barry R., Series editor, Venghaus, Herbert, Series editor, Weber, Horst, Series editor, Weinfurter, Harald, Series editor, Midorikawa, Katsumi, Series editor, Nolte, Stefan, editor, Schrempel, Frank, editor, and Dausinger, Friedrich, editor

Published
2016
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31. Role of oxygen diffusion in the dislocation reduction of epitaxial AlN on sapphire during high-temperature annealing.

Author

Cancellara, Leonardo, Markurt, Toni, Schulz, Tobias, Albrecht, Martin, Hagedorn, Sylvia, Walde, Sebastian, Weyers, Markus, Washiyama, Shun, Collazo, Ramon, and Sitar, Zlatko

Subjects
SAPPHIRES, SECONDARY ion mass spectrometry, ELECTRON microscope techniques, HEAT of formation, TRANSMISSION electron microscopy, POINT defects
Abstract

Recovery of epitaxial AlN films on sapphire at high temperatures is now an established process to produce pseudo-substrates with high crystalline perfection, which can be used to grow epitaxial structures for UV-light-emitting devices. To elucidate the elementary mechanisms taking place during the thermal treatment of MOVPE-grown films, we studied as-grown and annealed samples combining transmission electron microscopy techniques and secondary ion mass spectrometry (SIMS). By using SIMS, we find a temperature-dependent increase in the overall oxygen content of the films, which cannot be explained quantitatively with either simple bulk or pure pipe-diffusion from the sapphire substrate. Instead, we propose a lateral outdiffusion from the dislocation cores to explain qualitatively and quantitatively the presence of observed oxygen concentration plateaus. Based on the formation enthalpy of various atomic defects and complexes found in literature, we conclude that the di-oxygen/aluminum vacancy complex (VAl–2ON) is the dominant point defect controlling the annealing process. The formation of this defect at high temperatures promotes a dislocation core climb process, which causes the annihilation/fusion of the threading dislocation segments. [ABSTRACT FROM AUTHOR]

Published
2021
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36. Enhanced light extraction efficiency of UV LEDs by encapsulation with UV-transparent silicone resin

Author

Wu, Shaojun, primary, Guttmann, Martin, additional, Lobo-Ploch, Neysha, additional, Gindele, Frank, additional, Susilo, Norman, additional, Knauer, Arne, additional, Kolbe, Tim, additional, Raß, Jens, additional, Hagedorn, Sylvia, additional, Cho, Hyun Kyong, additional, Hilbrich, Katrin, additional, Feneberg, Martin, additional, Goldhahn, Rüdiger, additional, Einfeldt, Sven, additional, Wernicke, Tim, additional, Weyers, Markus, additional, and Kneissl, Michael, additional

Published
2022
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38. Development of far-UVC LEDs and their application in irradiation systems for antisepsis and sensing

Author

Lobo Ploch, Neysha, primary, Cho, Hyun Kyong, additional, Filler, Thomas, additional, Glaab, Johannes, additional, Gundlach, Heiko, additional, Guttmann, Martin, additional, Hagedorn, Sylvia, additional, Mehnke, Frank, additional, Rass, Jens, additional, Ruschel, Jan, additional, Schilling, Marcel, additional, Sulmoni, Luca, additional, Wernicke, Tim, additional, Wittenbecher, Lucas, additional, Woggon, Ulrike, additional, Kramer, Axel, additional, Meinke, Martina C., additional, Kneissl, Michael, additional, Weyers, Markus, additional, Winterwerber, Ulrike, additional, and Einfeldt, Sven, additional

Published
2022
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45. Time-resolved photoluminescence from n-doped GaN/Al0.18Ga0.82N short-period superlattices probes carrier kinetics and long-term structural stability.

Author

Mahler, Felix, Tomm, Jens W., Reimann, Klaus, Woerner, Michael, Hoffmann, Veit, Netzel, Carsten, Weyers, Markus, and Elsaesser, Thomas

Subjects
PHOTOLUMINESCENCE measurement, GALLIUM arsenide, SUPERLATTICES, HETEROSTRUCTURES, ELECTRONIC excitation
Abstract

Heavily n-doped GaN/Al0.18Ga0.82N short-period superlattices with and without SiN protection layers are studied in spectrally and temporally resolved photoluminescence (PL) experiments. The room-temperature PL from a protected sample displays a nonexponential decay with an initial decay time of 150 ps for low excitation levels and an exponential decay with a time constant of ∼300 ps for higher excitation. The PL decays are governed by nonradiative carrier relaxation into deep defect states which are partially saturated at high excitation densities. PL measurements at low sample temperature reveal a marked influence of carrier cooling on the PL kinetics in a time range up to 50 ps and a significant radiative decay component. SiN coatings are shown to provide long-term stabilization of surface morphology while increasing nonradiative carrier relaxation rates. [ABSTRACT FROM AUTHOR]

Published
2019
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