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Conference 12022
Light-Emitting Devices, Materials, and Applications XXVI
In person: 24 - 27 January 2022
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POST-DEADLINE ABSTRACT SUBMISSIONS
- Submissions are accepted through 06-December
- Notification of acceptance by 20-December
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OPTO Plenary Session
In person: 24 January 2022 • 8:00 AM - 10:10 AM 8:00 AM: Welcome and Opening Remarks
Sonia M. García-Blanco, Univ. Twente (Netherlands); Bernd Witzigmann, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
8:05 AM: Announcement of the IBM-SPIE HBCU Faculty Accelerator Award in Quantum Optics and Photonics
Kayla Lee, IBM Research (USA)
Sonia M. García-Blanco, Univ. Twente (Netherlands); Bernd Witzigmann, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)
8:05 AM: Announcement of the IBM-SPIE HBCU Faculty Accelerator Award in Quantum Optics and Photonics
Kayla Lee, IBM Research (USA)
12001-501
Frontier electronics in memory of Professor Isamu Akasaki
(Plenary Presentation)
In person: 24 January 2022 • 8:10 AM - 8:50 AM
Show Abstract +
ISAMU AKASAKI, special distinguished professor of Meijo University, and distinguished university professor and emeritus professor of Nagoya University, the pioneer of blue LEDs, and the Nobel Laureate in physics, passed away from pneumonia on Thursday, April 1, 2021 at the age of 92. He was always a real pioneer. He started nitride research in 1967. At that time, blue LED research was an undeveloped area. When he moved from Matsushita Giken Co., Ltd. to Nagoya University in 1981, almost no other organizations attempted to continue with the topic. At that time, the majority of researchers determined that it was very difficult to grow single crystals, and that realizing p-type GaN was impossible. Therefore, many abandoned GaN. According to him, his situation at that time was like “going alone in the wilderness.” Today, the wilderness pioneered by Professor Isamu Akasaki is now a prosperous and fruitful field where many researchers all over the world are gathering and bringing happiness to the people. He liked the term “Frontier Electronics.” In this presentation, in addition to his memorial, today’s frontier electronics will be discussed.
12004-502
Inverse designed integrated photonics
(Plenary Presentation)
In person: 24 January 2022 • 8:50 AM - 9:30 AM
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Despite a great progress in photonics over the past few decades, we are nowhere near the level of integration and complexity in photonic systems that would be comparable to those of electronic circuits, which prevents use of photonics in many applications. This lag in integration scale is in big part a result of how we traditionally design photonics: by combining building blocks from a limited library of known designs, and by manual tuning a few parameters. Unfortunately, the resulting photonic circuits are very sensitive to errors in manufacturing and to environmental instabilities, bulky, and often inefficient. We show how a departure from this old fashioned approach can lead to optimal photonic designs that are much better than state of the art on many metrics (smaller, more efficient, more robust). This departure is enabled by development of inverse design approach and computer software which designs photonic systems by searching through all possible combinations of realistic parameters and geometries. We also show how this inverse design approach can enable new functionalities for photonics, including compact particle accelerators on chip which are 10 thousand times smaller than traditional accelerators, chip-to-chip on on-chip optical interconnects with error free terabit per second communication rates, and quantum technologies.
12017-503
Robust nonlinear and topological quantum photonics
(Plenary Presentation)
In person: 24 January 2022 • 9:30 AM - 10:10 AM
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In this talk we will discuss how to engineer the dispersion relation of photonic platforms to provide robust propagation of classical and quantum states of light. In the first part, we will unveil how to leverage the interaction of nonlinearity with higher orders of dispersion to create novel types of solitons, wave packets that propagate unperturbed for long distances. These objects have advantageous energy-width scaling laws with respect to conventional nonlinear Schrodinger solitons and show promise for applications in ultrafast lasers and integrated frequency combs. Subsequently, we will cover recent developments in topological quantum photonics. Topological photonics studies topological phases of light and leverages the appearance of robust topological edge states. We will emphasize our experimental demonstration of nonlinearly generated and topologically protected photon pairs and path-entangled biphoton states in silicon waveguide arrays. Further, we will detail our latest experiments demonstrating entanglement between topologically distinct modes, highlighting topology as an entanglement degree of freedom.
Session 1:
Honoring Isamu Akasaki: Joint Session with Conferences 12001 and 12022
Session Chairs:
Hiroshi Fujioka, Institute of Industrial Science, The Univ. of Tokyo (Japan), Martin Strassburg, OSRAM Opto Semiconductors GmbH (Germany)
12001-1
Remembering and honoring professor Isamu Akasaki
(Invited Paper)
Show Abstract +
My fondest memory of Professor Akasaki was an afternoon meeting solely with him in his office at Nagoya University in early Spring of 1990. He and his coworkers had just published their now highly cited paper “P-Type Conduction in Mg-Doped GaN Treated with Low-Energy Electron Beam Irradiation (LEEBI). The results and discoveries described in this paper both built upon prior ground-breaking research in collaboration with Professor Amano and served as a launch point for many additional related studies that culminated in the award of the Nobel Prize to both gentlemen. My presentation will provide additional details of our meeting as well as highlight some of Professor Akasaki’s internationally recognized, achievements including measurements of the piezoelectric effects in strained GaInN/GaN heterostructures and related quantum-confined Stark effects in these materials.
12001-2
Show Abstract +
Professor Isamu Akasaki achieved the GaN-based p-n junction blue LED in 1989, which was said to be "impossible to realize in the 20th century" and "theoretically unfeasible," and was awarded many prizes including the Nobel Prize in Physics 2014. In this presentation, we will review those great achievements of Professor Isamu Akasaki. We will also look back at the Nobel Prize award ceremony and Professor Akasaki's research activities after the invention of the blue LED. Nitride semiconductor materials have many unique physical properties that are different from other semiconductor materials, such as widely tunable bandgap, high quality heterojunctions, and giant polarization effects. Professor Isamu Akasaki used to say that "The nitride semiconductors are the ultimate semiconductor material". He was also actively involved in developing unique devices that controlled and utilized such properties. We would like to give a presentation on such efforts. Then, we would like to discuss the current state and future prospect in the research field of "Nitride Semiconductors" that Professor Akasaki has established.
12001-81
Show Abstract +
In 1989, after the first development of p-n junction in GaN-based blue LEDs by Professor Isamu Akasaki many researchers in Europe received GaN samples from him and started to investigate the optical, electrical and structural properties of group-III nitrides. This was an important step to form the first excellent centers for research in the European community. I met Prof. Isamu Akasaki the first time during the Nagoya workshop in 1995. This workshop highlighted the nitride semiconductors compared to the ZnSe competitor at these times. After this meeting and the MRS symposium of nitrides 1996 Prof. Akasaki was one of the driving forces and spirits to establish the international conference of nitride semiconductors. 2000 he founded in Nogoya the international workshop of group – III nitrides. In my talk I will review the impact of Prof. Akasaki on the nitride research in Europe.
Session 2:
MicroLEDs and AR/VR/MR I
Session Chair:
Michael R. Krames, Arkesso, LLC (United States)
12022-1
III-nitride-based RGB microLEDs for AR/VR applications
(Invited Paper)
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The developments of high performance InGaN based micro-light-emitting diodes (µLEDs) are discussed. Through novel epitaxial growth and processing, and transparent packaging we have achieved external quantum efficiencies as high as 58% EQE at 450nm for MmicroLEDs. The critical challenges of µLEDs, namely full-color scheme, decreasing pixel size and mass transfer technique, and their potential solutions are explored. Recently, we have demonstrated efficient microLEDs emitting in the blue to green at dimensions as small of 1 micron. Red InGaN based red MicroLEDs with efficiencies of 2.5% has also been fabricated.
12022-2
InGaN-based RGB micro-LED arrays
(Invited Paper)
Show Abstract +
We can grow high-In-content InGaN-based red LED structures by our original MOVPE. Using commercial InGaN-based blue and green LED wafers, we have fabricated RGB micro-LEDs and RGB monochromatic 10 X 10 micro-LED arrays. The size of the micro-LED was 17 m square. The red array showed the peak wavelength at 630 nm and the FWHM of 62.9 nm at 50 A/cm2. Its light output power density was as high as 176 mW/cm2, and the absolute EQE was approximately 0.4%. The RGB micro-LED arrays covered as good as 81.3% of the Rec. 2020 color space in CIE 1931 at 50 A/cm2.
Show Abstract +
Micro-LEDs with typical sizes from 1 μm to 100 μm have demonstrated attractive applications including display, optical communication, and solid-state lighting, due to their special characteristics of small size, localized light emission, and high heat dissipation ability. But challenges still exist in achieving full-color micro-LED display and high-speed optical communication. Recently, we have successfully realized full-color micro-LED display on a single-chip utilizing multi-wavelength multi-quantum wells (MQWs), and developed multifunctional GaN-based micro-LED and detector arrays for applications in display and visible light communication. Advanced applications of micro-LEDs in underwater wireless optical communication, ultraviolet-C (UVC) communication and energy harvesting will also be discussed.
12022-4
Ion implantation as a new strategy for micro-LED pixelation
(Invited Paper)
Session 3:
MicroLEDs and AR/VR/MR II
Session Chair:
Martin Strassburg, OSRAM Opto Semiconductors GmbH (Germany)
12022-5
Show Abstract +
MicroLED displays can have a major impact on user experience and sustainability of consumer electronics. One of the challenges to overcome for mass adoption of microLED is electrical connections of small devices to display substrate.
Electrical connection of transferred microLED into backplane requires complicated processes. In case of flipchip, it requires tall pads to be formed on LEDs and backplane and high temperature process and bonding used to connect the LEDs into the substrate. This is in addition to planarization and other metalization requirements. Furthermore, the design rules required for this process does not allow the microLED to be below certain sizes (at this point 15x30 um seems to be the limit).
12022-6
Show Abstract +
MicroLED micro-display is expected to be one of the best solutions for AR/MR applications owing to its high brightness, wide color gamut, fast response time, and good reliability. For high PPI applications, MicroLED micro-display is composed by million LED chips with the size smaller than 5 microns on silicon-based CMOS backplane. Many challenges have been discussed in this report and some solutions are provided. Finally, full color MicroLED micro-display with 1411 PPI is demonstrated. The micro-display is 0.39’’ and the resolution is 480x270 in full color. The brightness of this display is higher than 50,000nits.
Show Abstract +
This paper focuses on micro LED R, G, B emitter technologies for low power wearable displays. Selection of materials, novel micro LED architectures, LED driving schemes, backplanes and their impact on LED performance trade-off will be presented to meet long battery life wearable display requirements. An objective comparison will be presented based on strengths and weaknesses of micro LED technologies for their fit and wide adoption in displays vs. status quo. Micro LED technologies are expected to gain significant adoption in a wide range of wearable display products in near future.
12022-9
Show Abstract +
It has long been expected that near-eye displays such as AR and VR headsets will eventually take over conventional displays. Yet these technologies have barely penetrated everyday life due to the lack of true next-gen near-eye display architectures that overcome the critical issues (notably VAC). The lack of such displays is directly related to the slow evolution of image source industry.
A major issue is the light transmission efficiency, impacted by the emission angle of light sources versus the need for collimated light. Therefore there is a limit to image brightness achievable with the currently available solid-state light sources. There needs to be a breakthrough in available image-sources for AR displays to reach a comparable image quality to what the 2D display counterparts can currently offer. Be it a full-color uLED microdisplay, superluminescent LEDs, or developments in photonics, the key-challenge is to leverage these advancements enabling a next-generation near-eye display.
Session 4:
UV Emitters I
Session Chair:
Tetsuya Takeuchi, Meijo Univ. (Japan)
12022-10
Towards high efficiency tunnel junction UV-C and Far UV-C LEDs
(Invited Paper)
Show Abstract +
We have studied the design, epitaxy, and performance characteristics of AlGaN tunnel junction UV-C LEDs. We have demonstrated tunnel junction LEDs operating from 280 nm down to ~240 nm. The device operating at ~255 nm showed a maximum external quantum efficiency of 7.2% and wall-plug of 4%, which are nearly one to two orders of magnitude higher than previously reported tunnel junction devices operating at this wavelength. The realization of high efficiency far UV-C LEDs with the use of AlGaN nanostructures and BN will also be presented.
12022-11
Show Abstract +
Development of high output power 255/265nm AlGaN based UVC LEDs grown on AlN template
Myeong Seok Oh, Hae Jin Park, Youn Joon Sung, Seung Kyu Oh
PhotonWave Co., Ltd. Yongin-Si, Gyeonggi-Do 449-825 Korea
The main application of UVC light sources is sterilization, and the wavelength that gives the peak of disinfection efficiency is about 265 nm. A recent study showed that irradiation at 254 nm and 265 nm efficiently inactivated coronavirus 2 (SARS-CoV-2) double times higher than that at 280 nm. However, 255/265nm UVC LEDs still have several challenges such as output power, reliability, and manufacturability. EQEs of 265nm UVC LEDs have been reported to be about 2/3 of those for 275–300 nm.. Reliability is also known to deteriorate with shorter wavelength LEDs below 280nm UVC LEDs. In this talk recent advances in epitaxial layer, device design, and reliability for high current driven 255/265 nm UVC LEDs with output power above 100mW@500mA will be presented.
12022-12
Thin-film UV VCSELs and LEDs by electrochemical etching
(Invited Paper)
Show Abstract +
We will give an overview of state-of-the-art results and challenges to achieve high-performing III-nitride vertical-cavity surface-emitting lasers (VCSELs), with a particular focus on the requirements to push the emission wavelength into the ultraviolet (UV). Our method to simultaneously achieve high-reflectivity mirrors and good cavity length control by electrochemical etching enabled the world’s first UV-B VCSEL. The use of dielectric mirrors yielded lasers with a very temperature-stable emission wavelength thanks to the negative thermo-optic coefficient of the mirrors. We have used the same etch methodology to also lift-off fully processed LEDs from their growth substrate to improve the light extraction efficiency.
Show Abstract +
We demonstrated a high power UVC LED using a novel high-quality AlN template. The superior electrical performance is attributed to the decent quality-strain engineering with AlN/AlGaN epitaxy. Using p-type AlGaN SL instead of p-GaN as the contact layer, might reduce the UVC light absorption coefficient up to 90%, and improve the output power of the device up to 45%. The utilization of p-AlGaN layer and nPSS improved the light extraction efficiency via different mechanisms.
12022-14
Show Abstract +
Recent work on epitaxial growth of AlGaN layers for deep UV light emitters shows that hexagonal hillocks are forming in the growth of AlGaN on AlN templates and single crystals. Such hillocks exhibit an increased Ga content that may cause carrier leakage in p-n junctions and thus exhibit efficient devices. In this presentation we study the early stages of hillock formation in AlGaN layers on AlN substrates combining experimental studies by cathodoluminescence, nano x-ray diffraction, transmission electron microscopy and defect selective etching with density functional theory. Our combined experimental and theoretical results show that it is the compressive strain of the dislocations that causes preferential Ga desorption, thus reduces the incoming flux of species and locally leaves the step behind. The increasing Ga content at the step bunches further increases the strain. On the terrace that forms upon pinning, 2D nucleation starts, which is the origin of the forming hillocks.
Session 5:
UV Emitters II
Session Chair:
Matteo Meneghini, Univ. degli Studi di Padova (Italy)
12022-15
UV-C LEDs and their use in disinfection applications
(Invited Paper)
Show Abstract +
UV-C LEDs are still considered a new source of germicidal radiation, but the COVID-19 pandemic accelerated the research, development and application of these devices significantly.
Compared to conventional UV-C sources there is still a gap in efficiency and price. On the other hand, the specific properties of the LED allows completely new and even more efficient system designs which could not be realized with conventional UV-C sources before.
This presentation will discuss the unique benefits of UV-C LEDs and UV sensors in different system setups and explain the advantages in the application.
12022-16
Show Abstract +
Far-UVC LEDs are interesting for applications such as skin-tolerant inactivation of multiresistant pathogens and gas sensing. We present the development of 233 nm AlGaN-based far-UVC LEDs with an emission power of 3 mW at 200 mA and L50 lifetime of more than 1000 h, after burn-in. Additionally, the design of a far-UVC LED-based irradiation system, with a spectral filter which supresses emission >240 nm, to study the inactivation of bacteria and skin compatibility of the radiation will be presented. The system can be used to homogeneously irradiate a target area of 70 mm diameter with a mean irradiance of 0.4 mW/cm².
Show Abstract +
With this work we propose a guideline for the development of efficient and effective UVC surface disinfection systems for SARS-CoV-2 based on LED technology. The work analyze the optical and electrical characteristics of state of the art UVC LEDs. From the most recent scientific literature, optical simulations, and laboratory experiments we propose guidelines for the design of high efficiency LED based antiviral system for th treatment of contaminated surfaces. To validate the guidelines two different UVC-LED irradiation systems, for spherical and flat surfaces, have been designed, manufactured and tested. Results indicate a log-4 inactivation of SARS-CoV-2 in few minutes.
Show Abstract +
Surface disinfection has taken on a new role in the context of the corona pandemic. UVC modules based on LED chips strive to replace mercury vapor lamps. However this will only be achieved if the necessary optical performance for disinfection can be guaranteed. We would like to present the development of potting materials for UVC LED chips. The aim was to find a potting material for use at a wavelength of 250 nm, which is sufficiently transparent, easy to process and which remains stable in its properties for many 100 hours at these wavelengths. Furthermore, the total reflection in the LED base body should be minimized by a refractive index of the cured material n >> 1.4. In addition to the aspects of material development, metrological requirements and long-term studies are also presented. We have succeeded in developing a potting technology that can greatly increase the performance of the UVC LEDs by up to 70%.
Session 6:
Boron Nitride
Session Chair:
Jong Kyu Kim, Pohang Univ. of Science and Technology (Korea, Republic of)
12022-19
Efficient light-matter interaction in hexagonal boron nitride
(Invited Paper)
12022-20
Show Abstract +
In this talk, we present DUV electroluminescence and photocurrent generation in vdW heterostructures of hBN at room temperature. The external bias voltage from graphene electrodes not only efficiently flows photocarriers excited via the band-to-band transition but also enables tunneling carrier injection into the band edges, leading to prominent photocurrent and electroluminescence at DUV frequency, respectively. The laser excitation micro-spectroscopy shows that the radiative recombination and photocarrier excitation processes in the heterostructures originate dominantly from the pristine structure and the stacking disorders in hBN.
Show Abstract +
Solid-state deep ultraviolet (DUV) light sources in the 200-300 nm wavelength range are key components for a wide range of applications such as semiconductor fabrication, high-density data storage, water/air purification, and sterilization.
Hexagonal boron nitride (hBN) is the wide-bandgap semiconductor with a band of 6.4 eV and shows the efficient band edge cathodoluminescence at 215 nm as well as lasing behavior. Here I will present the efficient DUV electroluminescence (EL) in band edge emission at 215 nm as well as broad 303-333 nm emission peaks from hBN van der Waals heterostructure. I will also present the tunable DUV light emission around band edge emission of 215 nm as a function of electric field direction and discuss the possible origin of DUV EL from hBN van der Waals heterostructures. These results demonstrate the promising development of a highly efficient solid-state DUV light source at the nanoscale.
12022-22
Integrated nanophotonics with hexagonal boron nitride
(Invited Paper)
Session 7:
Long Wavelength Emitters
Session Chair:
Michael R. Krames, Arkesso, LLC (United States)
12022-23
Show Abstract +
In this talk, I will describe recent work in my lab on defect-tolerant light emitters using epitaxial InP quantum dots (QDs). We grow InP quantum dots on (AlxGa1-x)0.52In0.48P lattice-matched to GaAs using solid-source molecular beam epitaxy (MBE). We have recently demonstrated room-temperature, continuous-wave lasers on Si using InP QDs as the active region, highlighting the promise of our approach. Defect-tolerant InP QDs may enable demonstration of novel devices, such as integrated visible lasers on silicon for quantum information applications and red microLEDs with improved performance at micron-scale pixel sizes.
Show Abstract +
As a new sensing light source, we have developed a highly efficient pixelated self-emissive near-infrared OLED (NIR-OLED) light source with pixel pitch of 7.8 μm. It has realized highly efficient and stable NIR-electroluminescence by using highly efficient emissive materials and device structures. The integration with a high-definition backplane using CMOS technology is expected to realize an active-driven, high-efficiency NIR-OLED light source with a maximum EQE of 1% or more and an emission wavelength of 900 nm or more. In this presentation, we will introduce these NIR-OLED technologies and its applicability as a new sensing light source.
Show Abstract +
The advance of automated vehicles imposes increasing requirements on the sensor system. In the far field in front of the vehicle the detection of infrastructure and road users relies on camera and LiDAR systems. The aim is to improve the vision of camera systems by using active NIR illumination. A spectral comparison of the regulatory emission limits and the sensitivity of the cameras is performed to determine an optimal wavelength for additional NIR lighting. Based on a proposed illumination system, we compare the performance of a camera with the improved illumination to the performance of a camera with standard illumination.
Show Abstract +
The mid-infrared (IR) spectrum has important absorption resonances for optical sensing and has an important band for thermal projection. Mid-IR LEDs are beneficial for these applications because of the fast and stable turn on times, but suffer from low wall-plug efficiency. We present advancements in mid-IR LEDs wall-plug efficiencies using cascaded W-superlattices and thinned and textured surfaces. Further improvements were obtained with the reduction of gallium spitting during molecular beam epitaxial growth. The reduction was achieved by treating gallium sources with aluminum, which has been shown to prevent reactions with the crucible to stop gallium from forming droplets.
Session 8:
LED Technology, Manufacturing, and Reliability I
Session Chair:
Martin Strassburg, OSRAM Opto Semiconductors GmbH (Germany)
12022-27
Frontiers in LED technology
(Invited Paper)
Show Abstract +
The focus of LED technology and product development is expanding from emitter-level performance to enabling application-level differentiation. Over the past decade, the focus on LED efficiency has brought tremendous societal benefits and accelerated development. With the industry’s rapid progress, the rate of gains in lm/W for the dominant technology based on phosphor-converted LEDs has slowed. New technologies such as phosphors with narrow emission spectra and highly efficient ‘direct’ color LEDs are needed to reach the next levels in light source efficacy. At the same time, LED products are reaching new levels of complexity and functionality. CMOS/LED hybrids incorporate driving and other functions into LED-level packages are poised to bring intelligent, adaptive light sources to applications. MicroLED is the next frontier for displays and requires new ideas across all aspects of LED technology. This wave of innovation makes it one of the most exciting times for the LED industry.
12022-28
Show Abstract +
III-N light-emitting-diodes (LEDs) are subject of intense investigations, thanks to their high efficiency and great reliability. The quality of the semiconductor material has a significant impact on the electro-optical performance of LEDs: for this reason, a detailed characterization of defect properties and the modeling of the impact of defects on device performance are of fundamental importance. This presentation addresses this issue, by discussing a set of recent case studies on the topic; specifically, we focus on the experimental characterization of defects, and on the modeling of their impact on the electro-optical characteristics of the devices.
Show Abstract +
This paper investigates the effect of the properties and position of defects on the performance and reliability of InGaN/GaN Multi Quantum Well (MQW) LED. To this aim, we analyzed color-coded structures featuring two quantum wells, emitting respectively at 405 nm and 495 nm. We performed a constant current stress in order to induce degradation, thus being able to evaluate the mechanisms that limit the reliability of the devices. Then, to interpret the degradation results, we modeled the effect that different trap concentration and spatial locations have on the optical characteristics.
12022-30
Show Abstract +
Widening the range of efficiently emitting wavelengths is a goal of ongoing research on III-nitride LEDs. The so-called green gap is mainly related to the increasing severity of efficiency droop as the wavelength increases. The peak EQE in commercial green LEDs exceeds 60% but corresponds to a very low current density. In this presentation we review challenges in the development of long wavelength III-nitride LEDs. We discuss possible strategies to mitigate droop based on the understanding that nonradiative Auger recombination is the root cause. Finally, we present the current efficiency status of green, yellow and red III-Nitride LEDs.
Session 9:
LED Technology, Manufacturing, and Reliability II
Session Chair:
Michael R. Krames, Arkesso, LLC (United States)
12022-31
MOCVD technology for high-yield red microLED manufacturing
(Invited Paper)
Show Abstract +
In this presentation, we will discuss the requirements for Red microLEDs for advanced displays, the corresponding MOCVD Epitaxy capability needs,and share Veeco’s recent learnings.
12022-32
Show Abstract +
The development routes for adapted high volume manufacturing (HVM) tools are extracted based on device layer sequences related to specific applications to drive cost down and improve device performance. A considerable reduction of cost-per-Epi-layer (CoO) within the next 3-5 years is foreseen with a clear objective that GaN displaces Silicon based devices in many electronic circuits and systems.
The midterm roadmap is dominated by 2D transition metal dichalcogenides which have attracted great interest due to their unique (opto)electronic properties and the potential to be the next key material in neuromorphic and quantum computer architectures. Due to the fact that main research and development needs to be done our roadmap from single wafer reactors suitable for R&D tasks to high volume manufacturing tools with wafer size of up to 300 mm will be disclosed.
12022-33
Show Abstract +
Light emitting devices have become omnipresent in today’s world. As some light emitting devices consist of hundreds of layers, with tightly specified layer thicknesses and layer compositions, control of the complex and expensive metal organic vapor phase epitaxy process (MOVPE) can hardly be achieved without state-of-the-art in-situ metrology. In this talk we will provide an overview about today’s in-situ metrology techniques and will highlight application examples from LED and laser growth in MOVPE. We will show how precise measurement of wafer temperature, growth rate, wafer bow and surface quality can be achieved with the metrology integrated into the MOVPE-system.
Session 10:
Quantum Dots and Perovskites
Session Chair:
Juanita N. Kurtin, OSRAM Opto Semiconductors Inc. (United States)
12022-34
Show Abstract +
Quantum Dot technology is playing an increasingly important role in emissive displays including OLEDs, microLEDs and direct view emissive QD-LEDs. Applying Quantum Dot Color Conversion (QDCC) to blue OLEDs or microLEDs, can lead to lower cost, brighter, high contrast displays with wide color gamut.
Nanosys has developed new, heavy metal-free QD materials with enhanced blue absorption, high quantum yield and narrow, tunable emission. These attributes enable the fabrication of patternable QDCC films with high (>35%) photon conversion efficiency and BT.2020 color gamut coverage. These new QD materials have delivered greater flexibility to the design of printable inks and formulations. Fabrication can be done using inkjet printing or photolithography, depending on the feature size, mass production and cost requirements of the display product.
Show Abstract +
InP-based QDs have been utilized as environmental friendly materials in wide color gamut (WCG) display. However, the optical properties, such as brightness and color purity, and photochemical stability of InP-based QDs are still worse than Cd-based QDs. In this work, we introduced very bright and narrow green-emitting InP/ZnSe/ZnS QDs. These green-emitting InP/ZnSe/ZnS QDs by mixing with red-emitting InP-based QDs and photo-curable resin, and fabricating into the large area QD sheet can achieve 100% of color reproducibility to DCI-P3 standard. And those were robust enough to utilize color converter of the other types of QD displays.
Show Abstract +
Perovskite quantum dots (PQD) can be created using a ligand assisted reprecipitation method at room temperature and with affordable equipment. These PQDs can exhibit much higher photoluminescence (PL) than bulk perovskite films of the same material. In this study, methylammonium lead bromide (MAPbBr3) quantum dots were created using energetically aligned capping ligands of trans-cinnamic acid (TCA) and 3,3-Diphenylpropylamine (DPPA). The bandgap of the PQDs was adjusted by varying the quantity of ligands added to the solution during the ligand assisted reprecipitation process. Prototype light emitting diodes (LEDs) were created using the PQD thin films.
Show Abstract +
Due to all the challenges related to mass transfer processes, color conversion has become a key strategy to achieve monolithic full-color microdisplays. State-of-the-art color conversion based microdisplays use quantum-dot technology, which suffers from photostability issues and low absorption in the blue spectral range leading to at least 5µm-thick color converters (CC). This may cause aspect ratio issues for pixel lateral sizes under 5µm. Therefore, inorganic MQW CC could gain a lot of ground due to their better photostability and higher blue light absorption. This work investigates the use of photonic crystals to fully optimize InGaP/AlGaInP MQW based CC for microdisplays.
Session 11:
High-Power Down Converters
Session Chair:
Hee Jin Kim, Lumileds, LLC (United States)
12022-38
Saturation mechanisms in common LED phosphors
(Invited Paper)
Show Abstract +
Not many phosphor materials can offer stable output under high incident light intensities. Even the most promising LED phosphors saturate in high-power applications, i.e. they show decreased light output. The saturation behavior is often poorly understood. Here, I will present the efforts of Utrecht University and the lighting company Seaborough Research to unravel the saturation mechanisms of the popular commercial LED phosphor materials CaAlSiN3 doped with Eu2+, and K2SiF6 doped with Mn4+. Experiments with square-wave modulated laser excitation reveal the dynamics of absorption and decay of the luminescent centers. By modeling these dynamics and linking them to the saturation of the phosphor output intensity, we distinguish saturation by ground-state depletion, thermal quenching, and ionization of the centers. We measure and model the effects of external heating and heat transport to the environment.
12022-39
Show Abstract +
Narrow-band line-emitter phosphors have enormous potential for use in LEDs as they offer improved luminous efficacy while maintaining high color rendering. Trivalent Eu-doped phosphors are ideal from an emitter perspective, however, the major bottleneck for its implementation in LEDs is the lack of efficient blue absorption. To address this problem, we have been exploring nano-engineered interparticle energy transfer (IFRET), a new approach to engineer phosphors at the nanoscale. In this talk, the underlying physics, progress and challenges in achieving nano-engineered IFRET phosphors for practical LEDs will be discussed. The talk also explores the potential of rare-earth doped nanophosphors as downconverters for miniaturized LEDs.
Show Abstract +
Laser pumped phosphor (LPP) light sources are by now well established for generation of saturated colors in digital projection applications. But also white light sources that are compliant with the requirement of car headlights are already on the market. Lately, high luminance white light sources in the wide field of specialty lighting are of growing interest. Since requirements for color temperature, luminance and color homogeneity are different for each application, a thorough understanding of factors that influence those properties is required. We will discuss the impact of blue laser selection, device cooling, light collection optics, optical concepts and the selection of converter material and will thus derive a comprehensive guideline for material selection and optical design.
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The most common high power laser phosphor light source uses a rotating phosphor wheel. The cooling of the phosphor remains a challenge with the moving phosphor ring. This paper presents a stationary phosphor plate with a compact scanning optical system such that the focused laser spot on the phosphor plate follows a circular path providing a larger excitation area around the circumference while maintaining the etendue of a single stationary focused spot. Initial experiment with a mirror tilt angle of 1.6 with a 1.96 mm diameter circular path and a focused spot size of 0.48 mm, a power of 54.6 W was achieved before the phosphor was degraded. This is equivalent to a power density of 302 W/mm2, which is 6 times improvement over the specification of 50 W/mm2. Further analysis is being performed to study the damage threshold dependance on thickness of the phosphor plate, and the rotation speed and tilt angle of rotating mirror.
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A novel method for time efficient fabrication of PIGs using a pulsed CO2 laser is presented. Phosphor and glass powder are deposited on glass surface and irradiated by a laser to create a solidified composite. Due to the localized and short exposure to high temperature, it eliminates the need for specialized low melting point glasses to avoid degradation. It uses the full capacity of the CO2 laser for structuring and polishing the surface in a single step. Samples with different compositions and film thickness have been fabricated and effect of various relevant parameters such as composition, temperature, laser power is studied.
Posters-Wednesday
In person: 26 January 2022 • 6:00 PM - 8:00 PM Conference attendees are invited to attend the OPTO poster session on Wednesday evening. Come view the posters, enjoy light refreshments, ask questions, and network with colleagues in your field.
Poster Setup: Wednesday 10:00 AM – 5:00 PM
View poster presentation guidelines and set-up instructions at
https://spie.org/PW/Poster-Guidelines
Poster Setup: Wednesday 10:00 AM – 5:00 PM
View poster presentation guidelines and set-up instructions at
https://spie.org/PW/Poster-Guidelines
Show Abstract +
Germicidal irradiation with a dose of UVC light is an effective method for disinfecting surfaces, water, and air. New commercial devices are abandoning mercury gas-arc lamps in favor of UVC LEDs, but UVC LEDs are far less efficient. This requires optical designs that use lenses to deliver UVC light efficiently to the target. This paper presents metallic optical reflectors (MORs), made with accurate stamping processes, as a new lens for UVC LEDs. Designs are described, tested, and validated for applications in SMD packages and also in chip-on-board (COB) LED modules. Aspherical mirror surfaces in MORs narrow the beam to achieve viewing angles as small as 15 degrees with efficiencies around 93%. Simulations show that LEDs with MORs are suitable for germicidal irradiation of surfaces and air in above-room applications.
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The deep ultraviolet (DUV) light-emitting device (LED) based on ac thin-film electroluminescence (EL) has been for the first time demonstrated with neodymium (Nd) or praseodymium (Pr)-doped fluorophosphate film on semiconductor substrate. The device consisted of DUV-transparent Ni-Au top electrode, insulating layer of Al2O3-TiO2 (ATO) compound, and phosphor layer on the substrate. The LED at AC voltage above a threshold voltage of 20 V showed the sharp-line and the broad-band spectra with a peak position of 200 nm on average for Nd and Pr activators, respectively. It is attributed to the impact excitation of activators by hot electrons from the interfacial deep traps, and then their f-d transition by large energy splitting due to strong spin-orbital interaction.
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UV-C LEDs and devices need accurate characterization of optical performance. When UV-C LED devices are installed in enclosures and rooms several challenges arise including 1) under- and over-dosing due to non-uniformity of UV-C dosage, 2) poorly understood room/chamber dynamics and reflectance, 3) shadowing, and 4) sensor, material, and source degradation. We introduce a new detector portfolio calibrated at critical UV-C LED wavelengths that enables real time Irradiance measurements at near-field and far-field. Coupled with a proprietary cosine diffuser that delivers exceptional f2 response, these sensors are ideal for deployment as accurate dosage monitors in rooms, enclosures, and HVAC systems.
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The importance of automotive lighting increased sharply over the last two decades since LED based systems have been introduced successfully. Besides the recent outstanding developments for traffic safety, also design and energy efficiency aspects are getting more prominent. To fulfill the increasing set of specifications, the presented functional polymers are essential for the further development in automotive lighting solutions. Already qualified for high precision bonding tasks in automotive lighting applications, the discussed materials are also capable to manufacture Micro Lens Arrays (MLA). Moreover, they allow the design of smaller and more efficient systems as well as the implementation of additional functions.
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During the last decade, LEDs have been the norm in the field of lighting, especially in the case where small sizes combined with high illumination is needed. A more recent alternative to this type of source of light is the conversion of a beam resulting from a blue or purple laser diode into white light by means of phosphors. In this case, a larger yield is to be achieved due to greater luminance and lower electric power. In this work, three types of phosphors were mixed and then irradiated by a 405 nm purple laser diode to produce white light.
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Current micro-optical multi-aperture projectors consist of condenser and projector lenslet arrays in a fly’s eye homogenizer configuration. A buried absorptive mask is used to shape the illumination pattern leading to a loss of etendue as well as transmission. We propose a 'mask-less' approach, where light shaping is reached by individually tailored geometries of the condenser apertures in gap-free arrangements. If a complete area coverage of apertures is unfeasible the tiny residual regions are provided with refractive diffusors. Now beam shapers close to etendue conservation with high transmissions based on simpler two-sided refractive manufacturing technology arise. Based on the mask-less approach micro-lens-array projection systems are designed, manufactured and characterized.
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Both semiconducting and superconducting materials had separately revolutionized modern technology. In this work a unique GaN-based blue LED with a bottom Ge-Mg doped tunnel junction (TJ) was monolithically integrated with a superconducting NbN film. The device was successfully grown on a single epitaxial platform by plasma-assisted MBE. Low turn on voltage and high emission efficiency was achieved. Comparison of the high- and low-temperature operation will be presented. Impact of the tunnel junction and NbN contact layer will be discussed.
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With the constant development of optical devices in communication and display applications, producing Light-Emitting Devices (LEDs) on large scale wafers with silicon circuit functions is a main challenge nowadays. State of the art red LEDs are grown on GaAs substrate, which lead to a high cost and low scalability due the III-V substrate. However, the direct epitaxy of III-V materials on silicon could allow to develop devices at a low-cost solution at high scalability. The feasibility of direct growth approach is approved by developing red resonant cavity-LEDs (RC-LED) with Distributed Bragg Reflector (DBR) to favor the top light extraction.
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A fully-automated UV LED lifetime test system for large-scale measurement of surface mount UV LED devices is proposed and designed. The system allows for rapid, repeatable measurements in a low-cost set-up and is equipped for AI-enabled precise position control allowing for utilization with variable optics options. While integrated sphere-based lifetime measurements provide absolute radiometric output data, angular output can vary based on lifetimes. This can be critical for certain UV LED applications. This lifetime measurement system allows for measurement of radiometric output based on angular spread without the need for expensive goniometric apparatus.
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Micro-LED has excellent technical advantage, and the manufacturing cost is getting reduced. To be mainstream technology, the next bottle neck is the testing cost. The existing test approach has issue of performance, accuracy and throughput then it is impacting entire manufacturing cost. One of issue on test is the EL optical test performance and throughput which test LED one by one. There is strong demand want to the optical test die in parallel but should meet mass production performance. This presentation offers brand new approach of the micro-LED wafer testing especially for upcoming Mass Production. Which has electrical/optical test embedded as single setup, massive parallel test of electrical/optical test with excellent throughput. Also this approach could use for matrix/unit testing.
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InGaN/GaN core-shell microrods (µrods) are highly promising for a new generation of light-emitting diodes. We present a 3D confocal optical approach with a spatial resolution <500 nm for characterizing operating µrod devices. 3D photoluminescence maps reveal an inhomogeneous emission: red luminescence originates from the apex and green emission from the corners, while blue emission dominates at the sidewalls. A pronounced photocurrent is measured while exciting µrods in closed current configuration, indicating charge carrier losses out of the active region due to tunneling. This interpretation is confirmed by applying an external voltage, where losses are suppressed.
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In a light emitting diode-based semiconductor light source that is variously applied as a display light source, luminous efficiency is a very important optical property, and various research methods including multiple quantum wells have been proposed to increase the luminous efficiency. However, since the efficiency improvement is basically based on the planar structure, there was a limit to the improvement of optical properties. In this study, nano holes were formed through micro patterns and etching of silicon oxide, different from the conventional structure are proposed. In addition, it is possible to implement a nano sized columnar structure through nano holes of silicon oxide, and by depositing a light emitting layer on the nano structure, it is intended to present a semiconductor light source having a nano-sized light emitting structure.
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Ultraviolet sources with different emission power and wavelengths are of great interest to many research areas and their applications. Commercially available UV lamps are expensive and they do not always fulfill the needs of the application. For example, wide spectrum and high emission power may not be desirable to all applications, forcing the use of filters that increase the cost of the source. LEDs may solve the aforementioned issues. In this work, we present the design and characterization of a homemade LED based UV source with variable emission in terms of power and wavelength. We also present an analysis of the advantages and disadvantages of the proposed source for different optical applications.
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In this study, we propose an optimization method for a water tank disinfection system through flow analysis simulation and development of lighting characteristics. In order to make the 10W output water tank disinfection system compact without reducing the efficiency, it was designed with a structure that can improve the disinfection exposure area by using flow simulation. For the change in lighting characteristics, a method of controlling the UV-C LED irradiation amount via operating current adjustment was used.
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The nonlinearity of the existing DFB laser makes it difficult to obtain distance information through FMCW LiDAR. To solve this problem, we used an auxiliary interferometer to the FMCW LiDAR system. Through the post-processing process of k-linearization, the nonlinearity of the DFB laser was compensated to get the position data of the target accurately as a 3D image. The proposed system uses DFB laser to obtain accurate location information by increasing the performance of FMCW LiDAR instead of using expensive and complex systems.
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The performance of microscale LEDs was investigated by considering chemical bonding states and carrier dynamics at interfacial region between sidewall and the passivation layers (SiO2, Al2O3, and Si3N4). Ga-N bonds on the GaN surface are effectively modified to Ga-O bonds due to the lower dissociation energy of Si-O bonds which can induce lots of oxygen diffusion inward. The formation of Ga-O bonds favours the reduction of non-recombination states on the surface. As the result, the sample with SiO2 passivation layer exhibits a photoluminescence efficiency of 25.1%, which is 19% and 63% higher than that of with Al2O3 and Si3N4.
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We present a frequency-modulated continuous-wave (FMCW) LiDAR system applying a novel non-mechanical beam steering mechanism. Acousto-optic deflector (AOD), which is an optical device that changes the path of light non-mechanically, is used to diffract light along one lateral direction. The light passed AOD is diffracted again by the diffraction grating, the wavelength dispersive element, along the other lateral direction in this time. 2D beam steering is achieved based on both acousto-optics and wavelength dispersion. Frequency-swept laser is employed for both FMCW ranging along the axial direction and spectral beam steering along the lateral direction. By confirming its successful signal acquisition, we can implement a 2D non-mechanical beam steering of FMCW LiDAR.
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The FMCW-LiDAR obtains digitalized signal using a high-performance ADC and measures distance by analyzing beat frequency according to the FFT. High accuracy, SNR, and real-time operation in FMCW Lidar require high sampling rate ADC and many FFT points, a burden on hardware and signal processing.
In this study, a frequency mixing FMCW-LiDAR was designed. The local oscillator (LO) was supplied by an electric chirp signal generated by an auxiliary interferometer. By mixing the sweeping LO and the beat signal, the proposed system can be relieved a burden of hardware and software limitations by enabling frequency analysis without complex signal processing.
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Micro LED displays potentially outperform LCD and OLED displays. The primary obstacle however is costly, therefore we focused our efforts on scaling the technologies without sacrificing yield and thus improving overall cost levels. We will present how the improved As/P MOCVD reactor and latest GaAs substrates are meeting the tightened micro LED requirements. As a technology solution, we developed a fully automated MOCVD platform for red micro LED, demonstrating first results on strict uniformity (>99% area in a 4nm range, 3 mm EE) and lowered defect density (> 50% compared with legacy platform) of epitaxial wafers for high volume manufacturing.
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We demonstrated the 630-nm peak wavelength InGaN-based micro-LED arrays at a high current density up to 50 A/cm2. The device dimension was 17 × 17 µm2. The micro-LEDs obtained a high light output power density of 1.76 mW/mm2 at 50 A/cm2, which is much higher than AlInGaP-based micro-LEDs (20 × 20 µm2). The on-wafer EQE was 0.18%. We also individually fabricated the blue and green micro-LED arrays, the color gamut of RGB micro-LED arrays covered as high as 81.3% of the Rec. 2020 color space in CIE 1931.
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AlGaN light emitting diodes (LEDs) emitting in the deep ultraviolet (DUV) range typically suffer from poor light extraction efficiency (LEE). In this study, we determine the effects of nanostructure height, diameter, and emission wavelength on LEE. Changes to device morphology influencing surface to volume ratio (SVR) are studied in order to optimize device dimensions to maximize LEE. Simulations show improvements in LEE of up to 300% and 60% for structures with increased height and decreased diameter respectively, which is predicted for higher SVR structures. These results shows that engineering of nanostructure SVR could be used to improve DUV LED efficiency.
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Hexagonal boron nitride (h-BN) is a III-V compound with a honeycomb lattice structure, like graphene. h-BN has been mainly synthesized by Chemical vapor deposition (CVD) on catalytic metal substrates (Cu, Ni, Pt, Fe, Au) for high crystalline quality of h-BN films or dielectric substrates (Al2O3, SiO2) for direct application to 2D semiconductor. Here we present the wafer-scale growth of h-BN films on III-Nitride semiconducting substrates using meal-organic chemical vapor deposition (MOCVD). We found that both MOCVD grown h-BN films on GaN and the GaN substrate itself were strongly affected by the reactor pressure and carrier gas, forming a very interesting feature of suspended h-BN film on GaN nanoneedles. Furthermore, unusual photoluminescence spectrum was observed at the deep ultraviolet region for the suspended h-BN films.
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Although gallium nitride (GaN)-based electronic devices for next-generation have garnered increasing attention over the last few years, the formation of surface defects, which severely deteriorate device performances, is fundamentally unavoidable and surface passivation is highly desired.
Herein, we report the realization of the clean van der Waals passivation layer, 2D hexagonal boron nitride (h-BN), directly grown on AlGaN/GaN HEMT wafer by using Metal-Organic Chemical Vapor Deposition (MOCVD) system. It was found that the hetero-interface between ~2.5 nm-thick h-BN and AlGaN layer is the atomically sharp with very weak van der Waals interaction, observed by state-of-the-art microscopic and spectroscopic analyses in consistent with calculations.The wafer-scale direct growth of atomically-thin-yet-electrically- “thick” h-BN would be very beneficial for miniaturization of not only compound semiconductor devices but also Si-based electronic devices.
Session 12:
Advanced Emitters
Session Chair:
Jong Kyu Kim, Pohang Univ. of Science and Technology (Korea, Republic of)
12022-43
Use of electrochemistry in mini-/micro-LEDs and VCSELs
(Invited Paper)
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As optoelectronic semiconductor research reaches a level of saturation, incorporation of unconventional processes and techniques often add to new phenomena and opportunities. In this talk I will share my perspective regarding the application of electrochemistry to GaN and related compound semiconductors. Two specific examples of using nanoporous structures, created by electrochemistry, for mini-/micro- LEDs and for vertical cavity surface emitting lasers (VCSELs) will be discussed.
12022-44
2D materials for integrated quantum photonics
(Invited Paper)
12022-45
Light emission from nano- and microLED arrays
(Invited Paper)
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Nanometer- and Micrometer-scale LED arrays are useful not only for display applications, but also for specialized applications like lens-less microscopy, mask-less lithography or optogenetics. In these contexts, the spatial resolution of the optical field and precise control over the illumination pattern at the object plane is of special importance. We have studied numerically different GaN LED array designs, calculating light extraction, optical near field and crosstalk between pixels. We find that 3D-patterning can help in shaping the light emission, while optical crosstalk becomes a critical issue for small LEDs and pitches below 300 nm.
12022-46
12022-47
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We present LED profiting from the bottom-tunnel junction (BTJ) construction. The BTJ design aligns the polarization fields in a desired direction in the vicinity of active region and inverts the ordering of the layer stack in the structure. This leads the situation were conductive, n-type layer is on the very top of the structure. Since current spreading in n-type material is much better than in p-type, BTJ-based light emitters open new possibilities in heterostructure design. In this talk we present new light emitting structures grown by plasma-assisted MBE based on BTJ platform and compare prospects for bottom and top tunnel junction devices.
Session 13:
LiFi, Sensing, and Communications
Session Chair:
Christoph G. A. Hoelen, Signify N.V. (Netherlands)
12022-48
Show Abstract +
The shortage on radio spectrum forced to high sophistication in spectrum efficiency. Optical wireless communication (OWC), rather than RF communication, can be a game changer, as the available optical spectrum is sheer unlimited. In addition, light can more easily be directed to the desired user (only). Narrowing the emitted light beams allows denser reuse, even within one room and increases throughput.
The authors report their experience from creating indoor OWC systems. The communication behavior of the LED was extensively studied and new models and metrics have been created. The trade-off between high throughput in only a narrow beam versus offering a wide coverage area is discussed. LEDs allow simple ways to direct a beam, which is more attractive than phased-array used in RF. An example of a sectorized system comprising 4 segments is presented and its performance and characteristics are discussed. An outlook to next generation OWC systems is presented including multi-user MIMO.
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We propose a V-VLC system able to safely manage vehicles crossing through an intersection. Using the headlights, the street lamps and the traffic signaling to broadcast the information, the vehicles interact with each other and with the infrastructure through visible light. An intersection manager coordinates the traffic flow and interacts with the vehicles. To command the vehicles crossing the intersection request/response mechanisms and relative pose concepts are used. A scenario is stablished and a “mesh/cellular” hybrid network configuration proposed. Results show that the short-range mesh ensures a secure communication to the edge computer through the neighbor traffic light controller and enables peer-to-peer communication, to exchange information between V-VLC ready connected cars.
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This paper builds a model for the key quality factor and benchmarking of suitable LEDs for wireless optical communication. Free Space Optical communication asks for output powers comparable to that of illumination LEDs. While non-radiate recombination causes a reduction in EQE, it also contributes to the response speed of LEDs and increases the 3-dB bandwidth. We introduce the “differential-EQE”, describing the differential extra photon output for a differential change in current. LED measurements and theoretical models for the LED trade-off are reviewed and applied into communication bit-rate throughput expressions. These translate into a bits-per-square-meter quality factor, rather than bits-per-meter as often used for optical communication.
12022-51
Show Abstract +
High-speed optical wireless communication (OWC) systems based on light-emitting diode (LED), such as Li-Fi, are promising solutions for the looming spectrum crisis in 6G wireless communications. OWCs typically extend the RF spectrum by harnessing the visible light and infrared spectra, but the recent advancements in deep-ultraviolet (DUV) LED device technology allow us to further extend the OWC spectrum down to the DUV range, namely the solar-blind band. This talk reviews the recent progress of the high-speed OWCs based on DUV-LEDs including Gbps-class transmission demonstrations in direct sunlight and analyses on the microscopic structural and optical characteristics of high-speed AlGaN-based LEDs.
Program Committee
Jana Hartmann
Technische Univ. Braunschweig (Germany)
Program Committee
Soo Min Lee
Veeco Compound Semiconductor Inc. (United States)
Program Committee
Yun-Li Li
PlayNitride Inc. (Taiwan)
Program Committee
Tetsuya Takeuchi
Meijo Univ. (Japan)
Program Committee
Erin C. Young
Apple Inc. (United States)