OSRAM (Germany)

The selection of UV-C light sources for disinfection and treatment applications involves consideration of performance, efficiency, lifetime, and cost. This paper introduces a novel performance metric - Cost of Germicidal Energy (CGE) - designed to provide a standardized framework for comparing UV-C sources across different technologies and both technical and economic parameters. CGE integrates key parameters, including radiant power, germicidal effectiveness (based on wavelength and spectral power distribution), energy consumption, source lifetime, and cost. By quantifying the cost per unit of germicidal energy delivered, CGE enables easier comparison and application-relevant assessment of different solutions. This metric is particularly valuable for guiding technology selection and system design in surface, air, and water disinfection applications. The paper presents a comparative analysis of conventional mercury-based UV-C lamps applications and emerging UV-C LED technologies. While mercury lamps have long been the industry standard, they face increasing regulatory and environmental challenges. In contrast, UV-C LEDs have advanced rapidly in recent years, with significant improvements in wall-plug efficiency, spectral targeting, operational lifetime, and cost reduction. The forward-looking roadmap for UV-C LED development is outlining projected milestones in performance and affordability. These projections are supported by recent record-setting prototypes and experimental data, demonstrating the accelerating pace of innovation in this field.

In this study, we continue the investigation of the oxide-GaN interface for a series of transition metal oxides: HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, ZrO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, Ta<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>, TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, Nb<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>, and Y<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, with SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> for reference. The oxide films were coated by atomic layer deposition. We compared the band-edge photoluminescence under two different optical excitation conditions: (i) using nanosecond pulses at 266 nm and (ii) picosecond laser pulses at 355 nm. These two wavelengths allow us to probe different excitation depths, from near-interface to sub-surface regions. Based on the experimental data showing changes in band-edge photoluminescence with excitation depth, we performed a qualitative analysis of band bending and the modulation of barrier height by photocarriers. We also examined its role in non-radiative recombination and carrier trapping. A relatively high barrier was observed at the SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-GaN interface, while lower barriers were inferred for the TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-GaN and Nb<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>-GaN interfaces.

The reliability of wire bonds in LED devices under temperature cycling tests is significantly affected by thermal expansion mismatches between encapsulation and wire materials, leading to mechanical stress and potential fatigue failure. Finite Element (FE) simulation is a powerful tool for designing reliable wire bonds. To improve simulation accuracy, this study integrates X-ray imaging, which provides precise wire geometry for constructing realistic models and serves as a validation tool for assessing simulation predictability. Cyclic thermomechanical simulations successfully predict plastic strain accumulation in the nailhead of wire bonds and capture differences between various wire bond designs. The simulation results align well with experimental observations, highlighting the influence of wire geometry on lifetime performance. The findings demonstrate that optimized wire bond designs enhance reliability, and the integration of X-ray imaging with FE simulations provides a robust framework for wire bond assessment and optimization.

Tungsten Fiber-Reinforced Composites In article number 2400951, Johann Riesch, Maximilian Fuhr, and Jürgen Almanstötter present a review which illuminates the unlikely revival of tungsten wire, from its iconic role as coils in incandescent bulbs to its emerging applications in high-performance composites for nuclear fusion reactors. This includes new insights into its unique combination of strength, ductility, and high-temperature properties, which are key properties for the excellent fracture behavior of tungsten fiber-reinforced composites. The authors discover how this versatile material is being reengineered and what new applications are emerging from cutting-edge research.

With the advent of µLED displays, multiple paradigm shifts in the overall system architecture will offer new opportunities and dramatically change the requirements of display management and general sensing. This work focuses on the required system architecture of a microLED display with embedded sensing functionality.

We present a Deep Level Transient Spectroscopy (DLTS) study on dedicated test samples to investigate the defect landscape of deep trench (DT) sidewalls. The DT is commonly used to prevent crosstalk between two neighboring optoelectronic devices or as a separator between different functional blocks on a monolithic semiconductor chip. However, in minority carrier-based optoelectronic devices, such as photodiodes, carriers might recombine at trap states located at the DT to silicon interface causing performance degradation. The extracted parameters of the DLTS study are further utilized to investigate this recombination in terms of TCAD simulations. The results suggest that carrier recombination at the DT sidewalls of DT-terminated photodiodes may lead to non-linear responsivities with respect to the optical radiant flux. Furthermore, on the example of silicon dangling bonds, we investigate the influence of structural relaxations at the defect sites which are incorporated in the nonradiative multiphonon (NMP) model. By a comparison between the NMP model to the conventional Shockley-Read-Hall (SRH) model we show, that a difference in the emission barrier of approx. 50 meV will arise, resulting in a strong shift of the corresponding DLTS transients.

In this paper, we report the latest advances in light-emitting diodes (LEDs) of the three primary colors red, blue, and green optimized for ultra high-power operation to achieve highest luminance and radiance values. These kinds of LEDs are mainly used in étendue-limited applications, particularly projectors. For the three colors different material systems are used: AlInGaP for red and InGaN for blue and green, while green uses a blue chip combined with a green ceramic converter. The chip designs and epitaxies have been modified compared to lower power versions to withstand high current densities up 6.6 A/mm² for blue, up to 4.5 A/mm² for red. The LED chips have been optimized at this operating point. The latest improvements show an increase of 8% in luminance for red, 17% for green, and 15% in radiance for blue compared to the previous generation. The LEDs using the latest improvement measures are setting the benchmark for ultra high-power LED technology.

Abstract We propose quantitative probing as a model-agnostic framework for validating causal models in the presence of quantitative domain knowledge. The method is constructed in analogy to the train/test split in correlation-based machine learning. It is consistent with the logic of scientific discovery and enhances current causal validation strategies. The effectiveness of the method is illustrated using Pearl’s sprinkler example, before a thorough simulation-based investigation is conducted. Limits of the technique are identified by studying exemplary failing scenarios, which are furthermore used to propose a list of topics for future research and improvements of the presented version of quantitative probing. A guide for practitioners is included to facilitate the incorporation of quantitative probing in causal modelling applications. The code for integrating quantitative probing into causal analysis, as well as the code for the presented simulation-based studies of the effectiveness of quantitative probing are provided in two separate open-source Python packages.

Micro-ring resonators (MRR) are basic photonic components, which serve as crucial building blocks for a variety of devices, e.g. integrated sensors, external cavity lasers, and high speed photonic data transmitters. Silicon nitride photonic platforms are particularly appealing in this field of application, since this waveguide material enables on-chip photonic circuitry with (ultra-) low losses in the NIR as well as across the whole visible spectral range. In this contribution we investigate key performance properties of MRRs in the wavelength range around 850 nm, such as free spectral range (FSR), quality factor (Q factor) and extinction ratio. We systematically investigate a large parameter space given by the MRR radii, coupling gaps between ring and bus waveguide, as well as waveguide width. Furthermore, we compare key properties such as the Q factor between low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) Si₃N₄ platforms and find enhanced values for LPCVD ring resonators reaching nearly a Q factor of 10⁶.The fabrication is carried out with standard CMOS foundry equipment, utilizing photolithography and reactive ion etching on 250 nm thick silicon nitride films. As cladding material, high density PECVD silicon oxide is deposited prior to the waveguide onto bare silicon and a sputtered oxide serves as upper cladding. With this process toolbox full CMOS backend compatibility is achieved when considering only PECVD Si₃N₄ waveguide material. In terms of manufacturability, special focus is put on the die-to-die as well as on wafer-to-wafer variability of the performance parameters, which is crucial when considering mass production of MRR devices. Finally, the experimental findings are compared to finite difference time domain (FDTD) simulations of the MRR circuits revealing excellent agreement when considering the manufacturing variability.

Small projector units for Near-To-Eye (NTE) displays such as AR glassed are currently a field of intensive research and development activity. To industrialize the first generation of user-friendly consumer smart glasses we propose using LED based solutions. LED illuminated DLP/LCoS pico-projectors are a mature technology which can be further optimized for the use in AR glasses. This article paper will share some updates on recent LED based NTE activities, and describe important design challenges such as etendue match, integration size and power efficiency.