Category Archives: LED Packaging and Testing

The latest research from the Niels Bohr Institute shows that LEDs made from nanowires will use less energy and provide better light. The researchers studied nanowires using X-ray microscopy and with this method they can pinpoint exactly how the nanowire should be designed to give the best properties. The results are published in the scientific journal, ACS Nano.

Nanowires are very small – about 2 micrometers high (1 micrometer is a thousandth of a millimetre) and 10-500 nanometers in diameter (1 nanometer is a thousandth of a micrometer). Nanowires for LEDs are made up of an inner core of gallium nitride (GaN) and a layer of indium-gallium-nitride (InGaN) on the outside, both of which are semiconducting materials.

“The light in such a diode is dependent on the mechanical strain that exists between the two materials and the strain is very dependent on how the two layers are in contact with each other. We have examined a number of nanowires using X-ray microscopy and even though the nanowires should in principle be identical, we can see that they are different and have very different structure,” explains Robert Feidenhans’l, professor and head of the Niels Bohr Institute at the University of Copenhagen.

The X-ray images of each nanowire show the distribution of the scattering intensity and the mechanical strain in the core of gallium-nitride and the shell of indium-gallium-nitride. The strain shows that the shell fits perfectly with the core. Credit: Tomas Stankevic, Niels Bohr Institute, University of Copenhagen.

The X-ray images of each nanowire show the distribution of the scattering intensity and the mechanical strain in the core of gallium-nitride and the shell of indium-gallium-nitride. The strain shows that the shell fits perfectly with the core.
Credit: Tomas Stankevic, Niels Bohr Institute, University of Copenhagen.

Surprisingly efficient 

The studies were performed using nanoscale X-ray microscopy in the electron synchrotron at DESY in Hamburg, Germany. The method is usually very time consuming and the results are often limited to very few or even a single study subject. But here researchers have managed to measure a series of upright nanowires all at once using a special design of a nanofocused X-ray without destroying the nanowires in the process.

“We measured 20 nanowires and when we saw the images, we were very surprised because you could clearly see the details of each nanowire. You can see the structure of both the inner core and the outer layer. If there are defects in the structure or if they are slightly bent, they do not function as well. So we can identify exactly which nanowires are the best and have the most efficient core/shell structure,” explains Tomas Stankevic, a PhD student in the research group ‘Neutron and X-ray Scattering’ at the Niels Bohr Institute at the University of Copenhagen.

The nanowires are produced by a company in Sweden and this new information can be used to tweak the layer structure in the nanowires. Professor Robert Feidenhans’l explains that there is great potential in such nanowires. They will provide a more natural light in LEDs and they will use much less power. In addition, they could be used in smart phones, televisions and many forms of lighting.

The researchers expect that things could go very quickly and that they may already be in use within five years.

Ultratech, Inc., a supplier of lithography, laser­-processing and inspection systems used to manufacture semiconductor devices and high-­brightness LEDs (HB­-LEDs), as well as atomic layer deposition (ALD) systems, announced that its Cambridge NanoTech business unit, Ultratech-CNT, has shipped its 400th ALD system. The system was purchased by the University of Michigan.

Dr. Neil Dasgupta, Assistant Professor of Mechanical Engineering at University of Michigan, whose group received the ALD equipment, said, “Ultratech-CNT’s ALD system has provided a significant boost to our research productivity, enabling us to make rapid advances in the field of surface and interfacial modification of energy conversion devices, including batteries, solar cells, and catalysts. The versatility of the ALD system to address the varied needs of our research program, coupled with the depth of knowledge of their science and engineering team, has enabled us to move very quickly towards producing high-impact research. We are happy to be part of this significant milestone in receiving the 400th system, and we look forward to developing a strong relationship with Ultratech-CNT.”

Ultratech-CNT Vice-President of Research and Engineering, Ganesh Sundaram, Ph.D., said, “It has always been about the scientist and researcher, and about making them successful in achieving their research goals.  We are extremely gratified by Professor Dasgupta’s decision to purchase our ALD system.  We have known his work since his days as a graduate student at Stanford University, and he has consistently produced noteworthy results using ALD. Looking forward, we are excited by the prospects of the breakthroughs in science that he, along with all other researchers, will be making using our instruments.  For our part, we celebrate the shipment of our 400th system and will continue our tradition of providing deep expertise combined with exciting technology.”

Ultratech-CNT’s ALD Systems: 

Savannah G2 ALD System
The Savannah G2 platform incorporates a wide range of advanced field-upgradable options intended to aid serious researchers in expanding their portfolio of available ALD films, as well as allow them to characterize the films in real time.

Phoenix G2 Batch ALD System
Engineered for high throughput, the Phoenix provides maximum uptime in any fabrication environment from pilot production to industrial-grade manufacturing. Technologists and researchers rely on the Phoenix for repeatable, highly-accurate film deposition on flat and 3-D substrates alike for batch production ALD requirements.

Fiji High-Vacuum ALD System
A modular, high-vacuum ALD system, the Fiji series accommodates a wide range of deposition modes using a flexible architecture and multiple configurations of precursors and plasma gases. The result is a next-generation ALD system capable of performing thermal and plasma-enhanced deposition.

Aledia, a developer and manufacturer of next-generation 3D LEDs based on its Gallium-Nitride-on-Silicon platform, announced today the closing of its Series B financing round and the execution of development and supply contracts with major LED buyers.

The round, totalling up to €28.4 million (approximately $31 million), includes new investments from Valeo, one of the world’s largest automobile-equipment manufacturers and the world’s second-largest supplier of car lighting systems; IKEA GreenTech AB, the venture capital arm of IKEA; and the Ecotechnologies fund of Bpifrance, the French national industrial bank. Aledia’s existing international investors – Sofinnova Partners, Braemar Energy Ventures, Demeter Partners and CEAi/ATi – also participated in the round.

“This financing round, abundantly oversubscribed, and particularly the presence of two very large potential corporate customers, testifies to the interest that our cost-disruptive nanowire LED technology is generating in the customer base, as well as in the financial community,” said Giorgio Anania, CEO, chairman and co-founder of Aledia.

Aledia is developing a new generation of LEDs that are manufactured on large-diameter silicon wafers (200mm or 8-inch), promise to be significantly less expensive than traditional “2D” LEDs, and that allow for integration of electronics into the LED. The company is also working on next-generation displays.

Anania said: “We are progressing with the development of the technology and this financing round will allow us to accelerate significantly the speed of development and the customer traction. In Valeo we have a major potential customer in the automotive LED market, generally viewed as the most profitable market segment. Simultaneously with the investment, we have signed a supply agreement with Valeo.”

Maurizio Martinelli, Valeo Visibility Business Group President, said: “We are convinced that Aledia’s 3D LED technology, together with Valeo’s expertise in automobile lighting systems, has the potential to put on the market a technological breakthrough in innovative lighting systems, perfectly in line with Valeo Lighting System’s mission to provide performance and style, and contribute to the safety of road users.”

Christian Ehrenborg, Managing Director of IKEA GreenTech AB, said: “This technology will be one important part in the IKEA Group strategy to supply high-quality, energy-saving lighting products to consumers worldwide. The low-price opportunity for residential use has the potential of faster implementation of the LED technology, leading to savings for customers. The connectivity functions of Aledia’s technology also open up new interesting possibilities to make life at home more convenient and smarter.”

Anne-Sophie Carrese, Investments Director at Bpifrance Investissement, said: “Bpifrance congratulates Aledia for its success in this operation. It proposes a breakthrough technology in a growing market and positions itself as a major actor in the smart-lighting industry. Aledia also benefits from its head start to create a French and European sector in LED, among which partnerships with prestigious industrialists such as IKEA and Valeo constitute the first stage.”

Dow Corning reported today that the Korean Intellectual Property Office (KIPO) granted a patent protecting the company’s high refractive index (RI) phenyl-based optical silicone encapsulant technology, which targets advanced LED lighting applications. Specifically, the patent protects the composition of curable organopolysiloxane chemistry used to formulate Dow Corning Optical Encapsulant products, which offer numerous high-value benefits to LED devices. These benefits include improved light output, excellent mechanical protection of LED components and enduring gas barrier properties for enhanced reliability.  The patent granted by the KIPO ensures only Dow Corning products are authorized to contain the patented technology.

“The KIPO’s decision is only the latest milestone in Dow Corning’s ongoing efforts to rigorously protect its diverse and multi-layered intellectual property family of advanced optical materials,” said Kaz Maruyama, global marketing director, Lighting Solutions, Dow Corning. “We applaud the KIPO’s action, which helps to validate prior decisions from patent offices in the European Union, the United States, Taiwan and Malaysia, as well as Japan, where we began developing this advanced technology more than a decade ago.”

Granted in early March, Patent 101499709 covers the composition of industry leading products such as Dow Corning OE-6630, OE-7620 and OE-7651N Encapsulants. All deliver high RIs in the range of 1.53 to 1.55, compared to the lower RI of 1.41 that is typical of methyl-based silicone chemistries. While seemingly small, that difference can translate into about 7 percent more light output. Achieving a comparable improvement from an LED chip would require significant investment.

In addition to higher RI, Dow Corning’s portfolio of phenyl silicone packaging materials delivers photothermal stability suitable for many middle- and high-power general lighting applications. Compared to methyl-based technology, phenyl-based silicone encapsulants generally offer a stronger gas barrier, which helps protect key LED components such as silver electrodes and phosphor against moisture deterioration and sulfur corrosion. LED electrodes double as reflective elements, and phosphor is a key element of light conversion. As a result, enhanced gas barrier protection helps maintain both light output performance and reliability of LED packages.

“Patenting these high RI phenyl-based optical silicone encapsulants in Korea is an important step for Dow Corning and for its customers, who depend on the consistent high-quality and reliable high-performance that our LED encapsulants provide,” Maruyama said. “Supply chain integrity and consistent material quality will be critical competitive benefits as LED lighting aims to offer a credible, cost-effective alternative to conventional light sources.”

Pixelligent Technologies, producer of PixClear, a producer of nanocrystal dispersions for demanding applications in LED lighting, OLED Lighting, and Optical Coatings & Films markets, announced today that it closed $3.4 million in new funding. The funds will be used to support accelerating customer growth throughout the world and to increase its manufacturing capacity to 40+ tons per year starting in 2016.

“Pixelligent continues to realize increased demand for its nanocrystal dispersions, predominantly driven by the leading LED package manufacturers and the leading OLED lighting producers. Pixelligent’s high-index and transparent zirconia nanocrystals are considered the best in the world by numerous experts and are becoming increasingly important in delivering more light from next generation Solid State Lighting as well as additional efficiencies in Display applications,” said Craig Bandes, President & CEO of Pixelligent.

To date, Pixelligent has raised over $26.0M in equity funding and has been awarded more than $12M in U.S. government grant programs.

Pixelligent Technologies is an advanced materials company that is leveraging nanotechnology to deliver the next generation of high index materials for solid-state lighting and optical components and films applications

Trans-Lux today announced the opening of a new design and production facility in Shenzhen, China to complement its existing manufacturing operations in Des Moines, IA. Additionally, the company announced the formation of new technology partnerships with LED suppliers Prismaflex International (EURONEXT PARIS: ALPRI) in Haute-Rivoire, France, and Squadrat in Schwanstetten, Germany.

“Our new design and production resources in China, and the addition of two highly renowned technology partners, further support the continued growth of Trans-Lux on a global scale,” said J.M. Allain, President and Chief Executive Officer, Trans-Lux. “Our new manufacturing facility in China complements our manufacturing capabilities here in the USA and allows us to accelerate delivery times with better quality controls. Combined with our new technology partners and expanded product LED display solutions for the Out of Home (OOH) market, Trans-Lux delivers the best value proposition for LED displays in the industry.”

The new factory in China, which has already started production of TL Vision and Prismatronic branded LED display systems, further expands and enhances the company’s portfolio of LED solutions. The new China facility also provides TransLux with complete control over mission critical processes to ensure the quality and reliability of products while reducing overall costs. By combining the resources of these two facilities, Trans-Lux will achieve greater manufacturing efficiencies which are being passed to customers in the form of more aggressive pricing. In addition to an expanded role in the manufacture of LED displays, the company’s US manufacturing facility will continue to develop new solutions for the sports scoreboard marketed under the highly popular Fair-Play by Trans-Lux brand.

Trans-Lux and Prismaflex International have joined forces to service the Americas with Prismatronic branded LED displays and BBM (Billboard Manager) software solutions for the OOH market. Trans-Lux has also entered into an alliance with Squadrat to market their powerful SX LED display content management software in the Americas. Trans-Lux will commence marketing the new software offering as epic v2.0.

Led by Young Duck Kim, a postdoctoral research scientist in James Hone’s group at Columbia Engineering, a team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported today that they have demonstrated — for the first time — an on-chip visible light source using graphene, an atomically thin and perfectly crystalline form of carbon, as a filament. They attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up. The study, “Bright visible light emission from graphene,” is published in the Advance Online Publication (AOP) on Nature Nanotechnology‘s website on June 15.

“We’ve created what is essentially the world’s thinnest light bulb,” says Hone, Wang Fon-Jen Professor of Mechanical Engineering at Columbia Engineering and co-author of the study. “This new type of ‘broadband’ light emitter can be integrated into chips and will pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.”

Creating light in small structures on the surface of a chip is crucial for developing fully integrated “photonic” circuits that do with light what is now done with electric currents in semiconductor integrated circuits. Researchers have developed many approaches to do this, but have not yet been able to put the oldest and simplest artificial light source — the incandescent light bulb — onto a chip. This is primarily because light bulb filaments must be extremely hot — thousands of degrees Celsius — in order to glow in the visible range and micro-scale metal wires cannot withstand such temperatures. In addition, heat transfer from the hot filament to its surroundings is extremely efficient at the microscale, making such structures impractical and leading to damage of the surrounding chip.

By measuring the spectrum of the light emitted from the graphene, the team was able to show that the graphene was reaching temperatures of above 2500 degrees Celsius, hot enough to glow brightly.

“The visible light from atomically thin graphene is so intense that it is visible even to the naked eye, without any additional magnification,” explains Young Duck Kim, first and co-lead author on the paper and postdoctoral research scientist who works in Hone’s group at Columbia Engineering.

Interestingly, the spectrum of the emitted light showed peaks at specific wavelengths, which the team discovered was due to interference between the light emitted directly from the graphene and light reflecting off the silicon substrate and passing back through the graphene. Kim notes, “This is only possible because graphene is transparent, unlike any conventional filament, and allows us to tune the emission spectrum by changing the distance to the substrate.”

The ability of graphene to achieve such high temperatures without melting the substrate or the metal electrodes is due to another interesting property: as it heats up, graphene becomes a much poorer conductor of heat. This means that the high temperatures stay confined to a small ‘hot spot’ in the center.

“At the highest temperatures, the electron temperature is much higher than that of acoustic vibrational modes of the graphene lattice, so that less energy is needed to attain temperatures needed for visible light emission,” Myung-Ho Bae, a senior researcher at KRISS and co-lead author, observes. “These unique thermal properties allow us to heat the suspended graphene up to half of temperature of the sun, and improve efficiency 1000 times, as compared to graphene on a solid substrate.”

The team also demonstrated the scalability of their technique by realizing large-scale of arrays of chemical-vapor-deposited (CVD) graphene light emitters.

Yun Daniel Park, professor in the department of physics and astronomy at Seoul National University and co-lead author, notes that they are working with the same material that Thomas Edison used when he invented the incandescent light bulb: “Edison originally used carbon as a filament for his light bulb and here we are going back to the same element, but using it in its pure form — graphene — and at its ultimate size limit — one atom thick.”

The group is currently working to further characterize the performance of these devices — for example, how fast they can be turned on and off to create “bits” for optical communications — and to develop techniques for integrating them into flexible substrates.

Hone adds, “We are just starting to dream about other uses for these structures — for example, as micro-hotplates that can be heated to thousands of degrees in a fraction of a second to study high-temperature chemical reactions or catalysis.”

Over the past 15 years, strong growth in optoelectronics has been fueled by several different product categories at different times.  Laser transmitters for high-speed optical networks were a major growth driver before the “dot.com” implosion in 2001. Image sensors and lamp devices (primarily light-emitting diodes—LEDs) became star performers in the last decade, and more recently, laser transmitters have re-emerged as a major growth driver in optoelectronics.  IC Insights believes these three products will be key contributors to overall growth of the optoelectronics market through 2019 (Figure 1).

optoelectronics snapshot

 

Through 2019, IC Insights sees these three trends driving optoelectronics market growth:

•    High-brightness LEDs (HB-LEDs) have reached the luminous efficacy of fluorescent lights and are in a position to be a major factor in the $100 billion global lighting industry.  Since the end of the last decade, strong sales of HB-LEDs have gone into backlighting systems for cellphones, tablets, LCD TVs, and computer displays, but this growth has greatly eased with penetration rates reaching nearly 100 percent in these applications.  With production capacity growing, HB-LED suppliers are concentrating on cutting costs and improving the overall quality of light for general illumination products in homes, businesses, buildings, outdoor lighting, and other applications, such as automotive headlamps and digital signs. HB-LED 2014 -2019 CAGR forecast (sales):  9.7 percent.

•    CMOS image sensors have entered into another wave of strong sales growth as digital imaging moves into new automotive-safety systems, medical equipment, video security and surveillance networks, human-recognition user interfaces, wearable body cameras, and other embedded applications beyond camera phones and stand-alone digital cameras. CMOS image sensor 2014-2019 CAGR forecast (sales):  11.1 percent.

•    Fiber-optic laser transmitters will continue to be the fastest growing optoelectronics product category as network operators struggle to keep up with huge increases in Internet traffic, video streaming and downloads, cloud-computing services, and the potential for billions of new connections in the Internet of Things (IoT).  Laser transmitter 2014-2019 CAGR forecast (sales):  15.3 percent.

A Si quantum dot (QD)-based hybrid inorganic/organic light-emitting diode (LED) that exhibits white-blue electroluminescence has been fabricated by Professor Ken-ichi SAITOW (Natural Science Center for Basic Research and Development, Hiroshima University), Graduate student Yunzi XIN (Graduate School of Science, Hiroshima University), and their collaborators.

Professor Ken-ichi Saitow, Natural Science Center for Basic Research and Development, Hiroshima University and Graduate student Yunzi Xin, Graduate School of Science, Hiroshima University, have fabricated an Si QD hybrid LED. CREDIT: Natural Science Center for Basic Research and Development, Hiroshima University

Professor Ken-ichi Saitow, Natural Science Center for Basic Research and Development, Hiroshima University and Graduate student Yunzi Xin, Graduate School of Science, Hiroshima University, have fabricated an Si QD hybrid LED.
CREDIT: Natural Science Center for Basic Research and Development, Hiroshima University

 

A hybrid LED is expected to be a next-generation illumination device for producing flexible lighting and display, and this is achieved for the Si QD-based white-blue LED. For details, refer to “White-blue electroluminescence from a Si quantum dot hybrid light-emitting diode,” in Applied Physics Letters; DOI: 10.1063/1.4921415.

The Si QD hybrid LED was developed using a simple method; almost all processes were solution-based and conducted at ambient temperature and pressure. Conductive polymer solutions and a colloidal Si QD solution were deposited on the glass substrate. The current and optical power densities of the LED are, respectively, 280 and 350 times greater than those reported previously for such a device at the same voltage (6 V). In addition, the active area of the LED is 4 mm2, which is 40 times larger than that of a typical commercial LED; the thickness of the LED is 0.5 mm.

“QD LED has attracted significant attention as a next-generation LED,” Professor Saitow said. “Although several breakthroughs will be required for achieving implementation, a QD-based hybrid LED allows us to give so fruitful feature that we cannot imagine.”

CEA-Leti today announced that it has demonstrated a path to fabricating high-density micro-LED arrays for the next generation of wearable and nomadic systems in a process that is scalable to the IC manufacturing process.

The high-brightness, enhanced-vision systems such as head-up and head-mounted displays can improve safety and performance in fields such as aeronautics and automotive, where the displays allow pilots and drivers to receive key navigation data and information in their line of sight. For consumers, smart glasses or nomadic projection devices with augmented reality provide directions, safety updates, advertisements and other information across the viewing field. LED microdisplays are ideally suited for such wearable systems because of their low footprint, low power consumption, high-contrast ratio and ultra-high brightness.

Leti researchers have developed gallium-nitride (GaN) and indium gallium-nitride (InGaN) LED technology for producing high-brightness, emissive microdisplays for these uses, which are expected to grow dramatically in the next three to five years. For example, the global research firm MarketsandMarkets forecasts the market for head-up displays alone to grow from $1.37 billion in 2012 to $8.36 billion in 2020.

“Currently available microdisplays for both head-mounted and compact head-up applications suffer from fundamental technology limitations that prevent the design of very low-weight, compact and low-energy-use products,” said Ludovic Poupinet, head of Leti’s Optics and Photonics Department. “Leti’s technology breakthrough is the first demonstration of a high-brightness, high-density micro-LED array that overcomes these limitations and is scalable to a standard microelectronic large-scale process. This technology provides a low-cost, leading-edge solution to companies that want to target the fast-growth markets for wearable vision systems.”

Announced during Display Week 2015 in San Jose, Calif., Leti’s technology innovation is based on micro-LED arrays that are hybridized on a silicon backplane. Key innovations include epitaxial growth of LED layers on sapphire or other substrates, micro-structuration of LED arrays (10μm pitches or smaller), and 3D heterogeneous integration of such LED arrays on CMOS active-matrices.

These innovations make it possible to produce a brightness of 1 million cd/m² for monochrome devices and 100 kcd/m² for full-color devices with a device size below one inch and 2.5 million pixels. This is a 100- to 1,000-times improvement compared to existing self-emissive microdisplays, with very good power efficiency. The technology also will allow fabrication of very compact products that significantly reduce system-integration constraints.

The high-density micro-LED array process was developed in collaboration with III-V Lab.