The weblink will be announced at the beginning of March at
Hinweis auf Deutsch (English Program see below):
Online-Vortragsreihe des Fachverbandes Halbleiterphysik "Halbleiter zum Frühstück"
virtuell, 15.03. - 26.03.2021
Nach dem großen Erfolg in 2020 geht "Halbleiter zum Frühstück" 2021 in die zweite Runde: Im Zeitraum vom 15.-26. März wird jeden Tag ein spannender Vortrag zu einem aktuellen Thema der Halbleiterphysik präsentiert.
Die Online-Vorträge werden live in Zoom gehalten und sollen insbesondere Studierende und Promovierende ansprechen. Die Vorträge finden passend zur Frühstückszeit um 10:15 Uhr statt, mit der Möglichkeit anschließend Fragen zu stellen. Der Zugang ist ohne Anmeldung über einen Weblink möglich (siehe https://www.dpg-physik.de/vereinigungen/fachlich/skm/fvhl/halbleiter-zum-fruehst...).
Zum Fachverband Halbleiterphysik (Semiconductor Physics) der DPG:
15.03.21 - Light from Silicon
Erik Bakkers (Eindhoven University of Technology)
Silicon and germanium cannot emit light efficiently due to their indirect bandgap, hampering the development of Si-based photonics. However, alloys of SiGe in the hexagonal phase are predicted to have a direct band gap. In this work, we demonstrate the realization of this new material and the direct band gap properties. We show efficient light emission up to room temperature accompanied by a short radiative life time, the hallmarks of a direct band gap material. The band gap energy is tunable in the range of 0.35 till 0.7eV opening a plethora of new applications. We finally discuss possible routes to integrate this material in Si- technology.
16.03.21 - Semiconductor nanolasers
Jesper Mørk (Technical University of Denmark)
Semiconductor micro and nanolasers are of practical importance for integrated photonics as well as emerging quantum technology. At the same time, they are an excellent playground for the study and exploration of light-matter interaction in nanostructures. In this talk, I will discuss a few emerging topics within nanolasers. The first topic is semiconductor Fano lasers, where the laser mode is based on a bound-state-in-the-continuum exploiting Fano interference. Such lasers have a number of intriguing properties, including passive pulse generation, ultra-high modulation bandwidth, reduction of quantum noise and increased stability towards optical feedback. Secondly, a new possibility of confining an optical mode far below the diffraction limit and its possible application to nanolasers and nanoLEDs will be discussed. This may offer the possibility of realizing intensity-noise squeezing in a large bandwidth. The analysis of such extreme lasers demand a detailed account of Purcell effects, and it becomes important to understand whether lasers with near-unity spontaneous emission factor actually lower the quantum noise or rather increase it.
17.03.21 - 2D van-der-Waals materials: phonons and excitons
Janina Maultzsch (FAU Erlangen Nürnberg)
18.03.21 - Fighting germs with deep UV LEDs
Michael Kneissl (TU Berlin)
Galvanized by high volume applications like water purification, disinfection of appliances and air filtering systems the development of light emitting diodes in the ultraviolet spectral range (UV-LEDs) has significantly intensified, with a focus on LEDs emitting near the germicidal effectiveness peak around 270 nm. This presentation will provide an overview of the state-of-the art in UV-LED technologies and discuss recent advances in the development of low defect density AlGaN heterostructures and AlN base layers on sapphire substrates. We will demonstrate high power AlGaN quantum well LEDs emitting near 270 nm and explore the wavelength limits of deep UV-LEDs with emission as short as 217 nm. These deep UV-LEDs are ideally suited for sensing applications like the monitoring of toxic gases, nitrates in water, and may also be utilized for the in-vivo inactivation of multi-drug-resistant germs and airborne viruses without damaging the human skin. However, a strong decline in the external quantum efficiency (EQE) can be observed for UV-LEDs below 250 nm. We will investigate the root causes for the drop in EQE at deep UV wavelengths, including changes in the optical polarization of light emission and their effects on light extraction as well as changes in radiative recombination rates and the role of point defects in AlGaN materials with high aluminium mole fractions. Based on these advances, milliwatt power LEDs emitting near 233 have been realized and the first spectrally pure deep UV LED irradiation module for the in-vivo inactivation of multi-drug-resistant bacteria is demonstrated.
19.03.21 - Brain-inspired computing with resistive memory
Irem Boybat (IBM Research Europe)
AI systems managed to reach and even exceed human performance in
various cognitive tasks, ranging from image recognition to strategic games
and to reasoning. Yet, today’s computing systems based on the classical
von-Neumann architecture dating from the 1940s cannot efficiently address
these highly data-intensive workloads. It is becoming increasingly clear
that we need to transition to non-von Neumann architectures in which
memory and logic co-exist in some form. Brain-inspired computing is one
such approach, where inspiration is taken from biological observations of
the brain. One can build in-memory computing units where the separation
between memory and processing is blurred, and physical attributes and
state dynamics of memory devices are exploited to perform certain
computational tasks. The neural structure and operation of the brain
including the rich neural and synaptic dynamics can also be adopted to add
to the information processing abilities and improve the efficiency of
computing systems. Resistive memory is expected to play a key role for
brain-inspired computing, from building in-memory computing arrays to
emulating neurons and synapses for neuromorphic computing. Explorations in
device technology and memory architectures could further enhance the
capabilities of brain-inspired computing systems.
22.03.21 - Buckling induced flat bands: giant nanoscale periodic strain
Francois Peeters (University of Antwerp)
23.03.21 - NIR and MIR Lasers and their use in sensing applications
Johannes Koeth (nanoplus Nanosystems and Technologies GmbH)
24.03.21 - Quantum Fluids of Interacting Photons
Daniele Sanvitto (CNR Nanotec - Lecce)
There is a growing interest in the study of polaritonic systems, mixed states of photons and excitons, for both, the observation of quantum macroscopic phenomena, and the realisation of all-optical devices that could offer limitless advantages in terms of energy consumption, dissipation-less operation, and high clock frequencies.
Here we show several macroscopic quantum phenomena that can be observed in polariton condensates, both at low temperature, in inorganic semiconductor microcavities–for which the very long lifetime can show behaviour associated to the Berezinskii-Kosterlitz-Thouless (BKT) regime – and in organic based polaritons, where superfluidity can be observed at room temperature. We also show the possibility of observing interesting topological behaviours by exploiting the peculiar band structure that can show, under certain conditions, the appearance of a Berry curvature as well as the emergence of artificial gauge fields acting on the propagation property of polariton fluids. Finally, we will show how such nonlinear systems could be used as hardware implementation of neuromorphic computing devices that demonstrate a high recognition rate compared to linear classifiers. Eventually we will also speculate on the possibility to reach the genuine quantum regime using single polaritons as quantum bits for the implementation of photonic nonlinear quantum devices.
25.03.21 - Collective phenomena in a QD nuclear spin ensemble
Claire LeGall (University of Cambridge)
A coherent ensemble of spins interfaced with a fully controllable proxy qubit is an attractive platform to generate many-body entanglement and study out-of-equilibrium dynamics in a complex quantum system. Semiconductor quantum dots are a physical realization of such a toy system, where the electron spin can be operated both as a control and a probe over the dense ensemble of nuclear spins within the QD. This talk will introduce how we can engineer all-optically a “flip-flop” interaction term between the electron and the nuclei and control the interaction strength. Further, I will present our latest experimental progress on the manipulation and characterization of the nuclear spin state, and specifically, the manifestation of subradiance in optically tailored polarised nuclear states.
26.03.21 - A quantum dot in a tunable microcavity as a fast and bright source of coherent single photons
Richard Warburton (University of Basel)
Photons at optical frequencies can transfer quantum information over large distances – a source of single photons is a valuable resource. Described here is a semiconductor source of single photons. A single quantum dot is used as quantum emitter; an open microcavity is used to funnel the photons into a single optical mode. A record overall efficiency is achieved with this approach. Crucially, the coherence of the photons is maintained over streams of thousands of photons. The talk will describe the basics of quantum dots and cavity-QED along with the latest results.
Information on participating / attending:
You can participate without registration by just using a weblink.
The weblink will be announced at the beginning of March at the website:
03/15/2021 10:15 - 03/26/2021 10:15
Scientists and scholars, Students
Electrical engineering, Information technology, Materials sciences, Physics / astronomy
Types of events:
Conference / symposium / (annual) conference, Presentation / colloquium / lecture, Seminar / workshop / discussion
Event is free:
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URL of this event: http://idw-online.de/en/event68077
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