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Fast characterization of Power LEDs: Circuit Design and Experimental Results

IEEE TRANSACTIONS ON electroN DEVICES 2024年第6期71卷 3753-3760页

作者： Roccato, Nicola Piva, Francesco Buffolo, Matteo Trivellin, Nicola De Santi, Carlo Narduzzi, Claudio Fraccaroli, Riccardo Caria, Alessandro Meneghesso, Gaudenzio Zanoni, Enrico Meneghini, Matteo Univ Padua Dept Informat Engn I-35131 Padua Italy Univ Padua Dept Ind Engn I-35131 Padua Italy Univ Padua Dept Phys & Astron I-35131 Padua Italy

A precise measurement of optical power, forward voltage, and junction temperature of light-emitting diodes (LEDs) is the key for characterization and health monitoring of these devices. In many cases, LED characterization is carried out with relatively long (10 ms and longer) pulses, that is, in conditions in which self-heating can significantly impact measurement results. To overcome this limitation, this article proposes a fast and versatile measurement approach based on a specifically designed current source, with a maximum current of about 1 A, high stability (variations under 0.1%) and settling time <20 mu s, and demonstrates its applicability to pulsed and transient characterization of power LEDs. The proposed system has the inherent advantages of 1) permitting a fast pulsed characterization of the devices, which-as we demonstrate-is much more accurate than quasipulsed or dc analysis;2) allowing isothermal characterization of LEDs without requiring long settling times, with beneficial impact on the throughput of LED characterization;3) allowing characterization of the voltage heating transient (during constant current operation), which is the key for junction temperature and thermal resistance extraction, as well as for the development of compact models;4) monitoring the optical power during the self-heating transient;and 5) the spectrum of the device providing additional information, such as the peak-shift or the phosphor behavior. The efficacy of the proposed approach has been demonstrated by testing commercial LEDs: the results clearly indicate that a fast (< 20 mu s) LED characterization is necessary for a proper extraction of the main spectral parameters and of the related temperature dependence.

关键词： electro-optical characterization light-Emitting diodes (LEDs) optoelectronic devices photothermal effects self-heating temperature measurement thermal analysis

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Evidence for localized trap formation during TADF OLED degradation

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ORGANIC electroNICS 2025年 139卷

作者： Stanzani, Edoardo Sem, Stefano Zufle, Simon Ruhstaller, Beat Jenatsch, Sandra Fluxim AG Katharina Sulzer Pl 2 CH-8400 Winterthur Switzerland Univ Valencia Inst Ciencia Mol C Catedrat J Beltra 2 Paterna 46980 Spain Zurich Univ Appl Sci Inst Computat Phys CH-8400 Winterthur Switzerland

Thermally activated delayed fluorescence (TADF) emitters attract interest as organic light-emitting diode (OLED) materials with potentially 100 % internal quantum efficiency (IQE). Their application in commercial displays is still hindered due to the not yet sufficient operational stability. We analyze the degradation mechanism in a TADF OLED by combining intermittent electro-optical characterization with device simulations. Evidence for the generation of trap states is found in capacitance-voltage (C-V) measurements. To explain both the C-V as well as the current-voltage and the capacitance-frequency evolution during prolonged operation times, at least two types of trap states are necessary. Device simulations are used to assess their location within the multilayer structure. It is found that both hole and electron traps at the HTL/EML interface can explain the experimental data. A quantitative comparison of simulations and experimental data reveal a hole and electron trap density of 8 center dot 1018 cm-3 and 8 center dot 1017 cm-3 , respectively, at LT80 (the time at which the luminance has dropped to 80 % of its initial value). The main driver for the current efficiency decrease are the hole traps inside the HTL. The findings unravel the weak points in the TADF OLED and thereby guide further development to enhance device stability.

关键词： Thermally activated delayed fluorescence OLED Degradation mechanism Trap states Device simulations electro-optical characterization

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Distributed Bragg reflector lasers emitting between 696 and 712 nm

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electroNICS LETTERS 2022年第24期58卷 908-910页

作者： Wenzel, Hans Arar, Bassem Maassdorf, Andre Fricke, Joerg Martin, Dominik Zink, Christoph Schiemangk, Max Wicht, Andreas Weyers, Markus Knigge, Andrea Ferdinand Braun Inst FBH Berlin Germany

The authors report on design, fabrication, and electro-optical characterization of single-frequency diode lasers emitting around 696, 707, and 712 nm. This has been achieved by a variation of the periods of the 10th order surface Bragg gratings implemented on a single epitaxial wafer. Depending on the wavelength, the devices achieved an optical output power of up to 60 mW at a current of 150 mA and spectral linewidths of about 400 kHz (full width at half maximum (FWHM)) and 20 kHz (Lorentzian).

关键词： Bragg gratings distributed Bragg reflector lasers spectral linewidths single-frequency diode lasers full width at half maximum optical fabrication single epitaxial wafer quantum well lasers FWHM electro-optical effects optical output power electro-optical characterization spectral line breadth 10th order surface Bragg gratings

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A 4H-SiC UV Phototransistor With Excellent optical Gain Based on Controlled Potential Barrier

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IEEE TRANSACTIONS ON electroN DEVICES 2020年第1期67卷 154-159页

作者： Di Benedetto, L. Licciardo, G. D. Erlbacher, T. Bauer, A. J. Rubino, A. Univ Salerno Dept Ind Engn I-84084 Fisciano Italy Fraunhofer Inst Integrated Syst & Device Technol D-91058 Erlangen Germany Friedrich Alexander Univ Erlangen Nurnberg D-91058 Erlangen Germany

In this article, we report the experimental results of a visible-light-blind 4H-polytype silicon carbide phototransistor able to detect ultraviolet (UV) radiations for wavelengths lower than 380 nm with a significative improvement in the optical gain compared with the state-of-the-art of 4H-SiC UV phototransistors. From the electro-optical measurements, the device shows a dark current of 0.62 pA, an ON-/OFF-current ratio of seven orders of magnitude up to bias voltage of -0.5 V, and an excellent optical gain of 1.14.10(5) at 300 nm, whereas it is only 2.6.10(-3) at 400 nm demonstrating a good rejection of visible radiations. Besides having high optical gain, the phototransistor is also more sensitive than the conventional 4H-SiC UV detectors for wavelengths with low penetration depths, because its structure is designed to have the electric field up to the radiated surface where the photogenerated electron-hole pairs are efficiently swept up before recombination occurs. The operating principle of the detector is also investigated, and we experimentally proved that differently from the conventional 4H-SiC bipolar junction transistor phototransistor, it is based on the change in the potential barrier height, which controls the current flow, due to the variation in the Fermi levels when the electron-hole pairs are photogenerated. A comparison with the state-of-the-art of 4H-SiC UV phototransistors is reported.

关键词： 4H-SiC semiconductor device electro-optical characterization phototransistor potential barrier ultraviolet (UV) detector

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Collective curved CMOS sensor process: application for high-resolution optical design and assembly challenges 69

Collective curved CMOS sensor process: application for high-...

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69th IEEE electronic Components and Technology Conference (ECTC)

作者： Chambion, B. Gaschet, C. Lombard, M. Fernandez, M. Joly, P. Caplet, S. Zuber, F. Vandeneynde, A. Peray, P. Lasfargues, G. Zussy, M. Deschamps, J. Bedoin, A. Henry, D. Univ Grenoble Alpes CEA LETI MINATEC Campus F-38054 Grenoble France

ISBN: (纸本)9781728114989

Curved sensors is a well-adapted technology solution to enhance the vast majority of optical systems. It helps to remove lenses and simplify optical architectures. These advantages open news challenges such as a specific fabrication process applied to curved sensors and new rules for final system integration. In this paper, we first introduce benefits of curved sensors applied on a compact high-resolution camera to define the sensor shape specifications and to reach high performances and compactness (-50% compared to a benchmark system). Mechanical limits and optical modeling are used. Then, based on these curved specifications, a novel collective curving process is described, developed on 1/1.8" format CMOS image sensors with a radius or curvaturetarget R= 55 mm and R=60 mm. This work includes packaging and assembly steps, optimizations, and morphological characterizations in accordance to optical design requirements. Finally, a dedicated optical test bench is used for Modulation Transfer Function (MTF) characterization of the final camera prototype. All these experiments and optical results introduce new opto-mechanical requirements and demonstrate the feasibility and high performances of systems with curved sensors.

关键词： Curved CMOS sensors collective process Arrays Imaging systems optical design Petzval Field Curvature Photography Mechanical limits Aberrations electro-optical characterization

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Curved sensors for compact high-resolution wide field designs: prototype demonstration and optical characterization 5

Curved sensors for compact high-resolution wide field design...

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Conference on Photonic Instrumentation Engineering V

作者： Chambion, Bertrand Gaschet, Christophe Behaghel, Thibault Vandeneynde, Aurelie Caplet, Stephane Getin, Stephane Henry, David Hugot, Emmanuel Jahn, Wilfried Lombardo, Simona Ferrari, Marc Univ Grenoble Alpes CEA LETI MINATEC Campus F-38054 Grenoble France Aix Marseille Univ CNRS LAM Marseille France

ISBN: (数字)9781510615649

ISBN: (纸本)9781510615649

Over the recent years, a huge interest has grown for curved electronics, particularly for opto-electronics systems. Curved sensors help the correction of off-axis aberrations, such as Petzval Field Curvature, astigmatism, and bring significant optical and size benefits for imaging systems. In this paper, we first describe advantages of curved sensor and associated packaging process applied on a 1/1.8 '' format 1.3Mpx global shutter CMOS sensor (Teledyne EV76C560) into its standard ceramic package with a spherical radius of curvature Rc=65mm and 55mm. The mechanical limits of the die are discussed (Finite Element Modelling and experimental), and electro-optical performances are investigated. Then, based on the monocentric optical architecture, we proposed a new design, compact and with a high resolution, developed specifically for a curved image sensor including optical optimization, tolerances, assembly and optical tests. Finally, a functional prototype is presented through a benchmark approach and compared to an existing standard optical system with same performances and a x2.5 reduction of length. The finality of this work was a functional prototype demonstration on the CEA-LETI during Photonics West 2018 conference. All these experiments and optical results demonstrate the feasibility and high performances of systems with curved sensors.

关键词： Curved sensors Detectors Arrays Imaging systems optical design Petzval Field Curvature High resolution Compact Photography Mechanical limits Aberrations Field of view electro-optical characterization

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Curved Full-Frame CMOS Sensor: Impact on electro-optical Performances 7

Curved Full-Frame CMOS Sensor: Impact on Electro-Optical Per...

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7th electronic System-Integration Technology Conference (ESTC)

作者： Chambion, Bertrand Caplet, Stephane Kopfer, Jan Martin Vandeneynde, Aurelie Diels, Wim de Kerckhove, Alexandre Peray, Patrick Henry, David Univ Grenoble Alpes CEA LETI MINATEC Campus F-38054 Grenoble France AMS Sensors Belgium B-2600 Antwerp Belgium

ISBN: (纸本)9781538668146

optical designs generate curved focal planes for which field flatteners must be implemented. A field flattener consists of an additional lenses block with a consequent loss of throughput and performances. With the recent packaging development for curved sensors, this can be omitted and the optical system simplified. In this paper, we first describe advantages of curved sensors and associated packaging process fabrication, applied on a full-frame format 20Mpx global shutter CMOS image sensor (AMS CMV20000 product). Mechanical limits for curving such full-frame sensor type are discussed, using Finite Element Modelling to manage die breaks. We have curved sensors with a spherical shape from concave Rc=150mm to convex Rc=280mm. We packaged them into their ceramic package and we carried out electro-optical characterization, in collaboration with the AMS CIS characterization team. The electro-optical performances of the curved sensors arc investigated and the results compared to the datasheet. We mainly focus on response uniformity, dark noise and dark current results. We present those characteristics in the form of mappings in order to investigate any impact of curvature process on image sensor performances. All these experiments and their electro-optical results demonstrate the feasibility of curving full-frame image sensor with only small electro-optical parameter shift compared to a typical flat reference.

关键词： Curved CMOS sensors Detectors Arrays Imaging systems optical design Petzval Field Curvature Photography Mechanical limits Aberrations electro-optical characterization

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Development of high-power laser diodes emitting at 975nm with enhanced wall-plug efficiency and wavelength stabilization for optical pumping of doped fibers and realization of fiber lasers.

Development of high-power laser diodes emitting at 975nm wit...

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作者： Roberto MOSTALLINO UNIVERSITE DE BORDEAUX

学位级别：博士

This PhD addresses the development of high-power laser diodes emitting at 975nm with high efficiency and wavelength stabilized using a Bragg grating. This thesis was conducted in the framework of a close partnership between IMS Laboratory, the GIE III-V lab, who is the main French founder of III-V semiconductor devices for electronic and photonic applications, and THALES Research & Technology in Palaiseau. An in-depth characterization and analysis work has addressed thermal aspects that contribute, in particular, to limit the optical output power of a laser diode. In such a context, we have carried out a set of complementary characterizations both at III-V lab and IMS allowing us to provide some corrective solutions for technological optimization concerning the etching depth of the grooves that defines the emitting stripe of the laser diode and the nature of the submount acting as a thermo- compensator. These solutions have been proposed from optical modelling implemented with a dedicated simulator, property of III-V lab, and thermal and thermomechanical (multiphysics approach) finite element simulations of the overall microassembled structure. All this work has resulted in the fabrication as well as electro-optical and thermal characterizations of three vertical structures namely LOC (Large optical Cavity), SLOC (Super Large optical Cavity) and AOC (Asymmetrical optical Cavity). The LOC and SLOC vertical structures have been processed with a Fabry-Perot cavity and also including a Bragg grating (DFB architecture) while the AOC one was only fabricated with a Fabry-Perot cavity. State-of-the-art results are demonstrated since in particular an optical power of 8W with an efficiency of 60% has been obtained that can be compared to those recently published by the Ferdinand-Braun Institute. The originality of the work carried out in this PhD has allowed us to receive a grant from the European Laserlab Cluster (The Integrated Initiative of the European Laser Research Infr

关键词： Optoelectronics laser diode electro-optical characterization DFB 975nm finite element simulation thermal thermomechanical thermal resistance micro-photoluminescence

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Curved sensors for compact high-resolution wide field designs 20

Curved sensors for compact high-resolution wide field design...

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20th Annual Conference on Novel optical Systems Design and Optimization

作者： Gaschet, Christophe Chambion, Bertrand Getin, Stephane Moulin, Gaid Vandeneynde, Aurelie Caplet, Stephane Henry, David Hugot, Emmanuel Jahn, Wilfried Behaghel, Thibault Lombardo, Simona Roulet, Melanie Muslimov, Eduard Ferrari, Marc Univ Grenoble Alpes CEA LETI MINATEC Campus F-38054 Grenoble France Aix Marseille Univ CNRS LAM Lab Astrophys Marseille Marseille France

ISBN: (数字)9781510612105

ISBN: (纸本)9781510612105;9781510612099

Over the recent years, a huge interest has grown for curved electronics, particularly for opto-electronics systems. Indeed, curved sensors help the correction of off-axis aberrations, such as Petzval Field Curvature and astigmatism. In this paper, we describe benefits of curvature and tunable curvature on an existing fish-eye lens. We proposed a new design architecture, compact and with a high resolution, developed specifically for a curved image sensor. We discuss about aberrations and effect of higher sensor curvature on third order aberrations. Besides, we show results of sensors' mechanical limits and its electro-optical characterization. Finally, all these experiments and optical results demonstrate the feasibility and high performances of systems with curved sensors.

关键词： Curved sensor optical design Petzval Field Curvature high resolution compact mechanical limits aberrations field of view electro-optical characterization

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Advances in Multi-Pixel Photon Counter technology: First characterization results

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2016年 806卷 383-394页

作者： Bonanno, G. Marano, D. Romeo, G. Garozzo, S. Grillo, A. Timpanaro, M. C. Catalano, O. Giarrusso, S. Impiombato, D. La Rosa, G. Sottile, G. Osserv Astrofis Catania INAF I-95123 Catania Italy Ist Astrofis Spaziale & Fis Cosm Palermo INAF I-90146 Palermo Italy

Due to the recent advances in silicon photomultiplier technology, new types of Silicon Photomultiplier (SiPM), also named Multi-Pixel Photon Counter (MPPC) detectors have become recently available, demonstrating superior performance in terms of their most important electrical and optical parameters. This paper presents the latest characterization results of the novel Low Cross-Talk (LCT) MPPC families from Hamamatsu, where a noticeable fill-factor enhancement and cross-talk reduction is achieved. In addition, the newly adopted resin coating has been proven to yield improved photon detection capabilities in the 280-320 nm spectral range, making the new LCT MPPCs particularly suitable for emerging applications like Cherenkov Telescope Array, and Astroparticle Physics. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Silicon Photomultipliers Multi-Pixel Photon Counters Fill-factor enhancement Low Cross-Talk Photon Detection Efficiency electro-optical characterization

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