TY - JOUR A1 - Wyborski, Paweł A1 - Podemski, Paweł A1 - Wroński, Piotr Andrzej A1 - Jabeen, Fauzia A1 - Höfling, Sven A1 - Sęk, Grzegorz T1 - Electronic and optical properties of InAs QDs grown by MBE on InGaAs metamorphic buffer JF - Materials N2 - We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window. Based on the photoluminescence (PL) measurements and numerical calculations, we analyzed the factors influencing the energies of optical transitions in QDs, among which the QD height seems to be dominating. In addition, polarization anisotropy of the QD emission was observed, which is a fingerprint of significant valence states mixing enhanced by the QD confinement potential asymmetry, driven by the decreased strain with increasing In content in the MBL. The barrier-related transitions were probed by photoreflectance, which combined with photoluminescence data and the PL temperature dependence, allowed for the determination of the carrier activation energies and the main channels of carrier loss, identified as the carrier escape to the MBL barrier. Eventually, the zero-dimensional character of the emission was confirmed by detecting the photoluminescence from single QDs with identified features of the confined neutral exciton and biexciton complexes via the excitation power and polarization dependences. KW - molecular beam epitaxy KW - quantum dot KW - metamorphic buffer layer KW - band structure KW - photoluminescence KW - photoreflectance Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-297037 SN - 1996-1944 VL - 15 IS - 3 ER - TY - JOUR A1 - Pfenning, Andreas A1 - Krüger, Sebastian A1 - Jabeen, Fauzia A1 - Worschech, Lukas A1 - Hartmann, Fabian A1 - Höfling, Sven T1 - Single-photon counting with semiconductor resonant tunneling devices JF - Nanomaterials N2 - Optical quantum information science and technologies require the capability to generate, control, and detect single or multiple quanta of light. The need to detect individual photons has motivated the development of a variety of novel and refined single-photon detectors (SPDs) with enhanced detector performance. Superconducting nanowire single-photon detectors (SNSPDs) and single-photon avalanche diodes (SPADs) are the top-performer in this field, but alternative promising and innovative devices are emerging. In this review article, we discuss the current state-of-the-art of one such alternative device capable of single-photon counting: the resonant tunneling diode (RTD) single-photon detector. Due to their peculiar photodetection mechanism and current-voltage characteristic with a region of negative differential conductance, RTD single-photon detectors provide, theoretically, several advantages over conventional SPDs, such as an inherently deadtime-free photon-number resolution at elevated temperatures, while offering low dark counts, a low timing jitter, and multiple photon detection modes. This review article brings together our previous studies and current experimental results. We focus on the current limitations of RTD-SPDs and provide detailed design and parameter variations to be potentially employed in next-generation RTD-SPD to improve the figure of merits of these alternative single-photon counting devices. The single-photon detection capability of RTDs without quantum dots is shown. KW - single-photon detectors KW - resonant tunneling diode KW - photon counting KW - III–V semiconductor devices Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-281922 SN - 2079-4991 VL - 12 IS - 14 ER - TY - JOUR A1 - Rothmayr, Florian A1 - Guarin Castro, Edgar David A1 - Hartmann, Fabian A1 - Knebl, Georg A1 - Schade, Anne A1 - Höfling, Sven A1 - Koeth, Johannes A1 - Pfenning, Andreas A1 - Worschech, Lukas A1 - Lopez-Richard, Victor T1 - Resonant tunneling diodes: mid-infrared sensing at room temperature JF - Nanomaterials N2 - Resonant tunneling diode photodetectors appear to be promising architectures with a simple design for mid-infrared sensing operations at room temperature. We fabricated resonant tunneling devices with GaInAsSb absorbers that allow operation in the 2–4 μm range with significant electrical responsivity of 0.97 A/W at 2004 nm to optical readout. This paper characterizes the photosensor response contrasting different operational regimes and offering a comprehensive theoretical analysis of the main physical ingredients that rule the sensor functionalities and affect its performance. We demonstrate how the drift, accumulation, and escape efficiencies of photogenerated carriers influence the electrostatic modulation of the sensor's electrical response and how they allow controlling the device's sensing abilities. KW - resonant tunneling diode KW - mid-infrared sensing KW - photosensor Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-267152 SN - 2079-4991 VL - 12 IS - 6 ER - TY - JOUR A1 - Li, Donghai A1 - Shan, Hangyong A1 - Rupprecht, Christoph A1 - Knopf, Heiko A1 - Watanabe, Kenji A1 - Taniguchi, Takashi A1 - Qin, Ying A1 - Tongay, Sefaattin A1 - Nuß, Matthias A1 - Schröder, Sven A1 - Eilenberger, Falk A1 - Höfling, Sven A1 - Schneider, Christian A1 - Brixner, Tobias T1 - Hybridized exciton-photon-phonon states in a transition-metal-dichalcogenide van-der-Waals heterostructure microcavity JF - Physical Review Letters N2 - Excitons in atomically thin transition-metal dichalcogenides (TMDs) have been established as an attractive platform to explore polaritonic physics, owing to their enormous binding energies and giant oscillator strength. Basic spectral features of exciton polaritons in TMD microcavities, thus far, were conventionally explained via two-coupled-oscillator models. This ignores, however, the impact of phonons on the polariton energy structure. Here we establish and quantify the threefold coupling between excitons, cavity photons, and phonons. For this purpose, we employ energy-momentum-resolved photoluminescence and spatially resolved coherent two-dimensional spectroscopy to investigate the spectral properties of a high-quality-factor microcavity with an embedded WSe\(_2\) van-der-Waals heterostructure at room temperature. Our approach reveals a rich multi-branch structure which thus far has not been captured in previous experiments. Simulation of the data reveals hybridized exciton-photon-phonon states, providing new physical insight into the exciton polariton system based on layered TMDs. KW - strong coupling KW - laser spectroscopy KW - transition metal dichalcogenide KW - coherent multidimensional spectroscopy KW - exciton Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-351303 UR - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.087401 SN - 1079-7114 ET - accepted version ER -