Category Archives: LED Packaging and Testing

For the first time an international research group has revealed the core mechanism that limits the indium (In) content in indium gallium nitride ((In, Ga)N) thin films – the key material for blue light emitting diodes (LED). Increasing the In content in InGaN quantum wells is the common approach to shift the emission of III-Nitride based LEDs towards the green and, in particular, red part of the optical spectrum, necessary for the modern RGB devices. The new findings answer the long-standing research question: why does this classical approach fail, when we try to obtain efficient InGaN-based green and red LEDs?

This is a scanning transmission electron microscopy image of the atomic ordering in (In, Ga)N monolayer: single atomic column, containing only indium (In) atoms (shown by higher intensity on the image), followed by two, containing only gallium (Ga) atoms. Credit: IKZ Berlin

This is a scanning transmission electron microscopy image of the atomic ordering in (In, Ga)N monolayer: single atomic column, containing only indium (In) atoms (shown by higher intensity on the image), followed by two, containing only gallium (Ga) atoms. Credit: IKZ Berlin

Despite the progress in the field of green LEDs and lasers, the researchers could not overcome the limit of 30% of indium content in the films. The reason for that was unclear up to now: is it a problem of finding the right growth conditions or rather a fundamental effect that cannot be overcome? Now, an international team from Germany, Poland and China has shed new light on this question and revealed the mechanism responsible for that limitation.

In their work the scientists tried to push the indium content to the limit by growing single atomic layers of InN on GaN. However, independent on growth conditions, indium concentrations have never exceeded 25% – 30% – a clear sign of a fundamentally limiting mechanism. The researchers used advanced characterization methods, such as atomic resolution transmission electron microscope (TEM) and in-situ reflection high-energy electron diffraction (RHEED), and discovered that, as soon as the indium content reaches around 25 %, the atoms within the (In, Ga)N monolayer arrange in a regular pattern – single atomic column of In alternates with two atomic columns of Ga atoms. Comprehensive theoretical calculations revealed that the atomic ordering is induced by a particular surface reconstruction: indium atoms are bonded with four neighboring atoms, instead of expected three. This creates stronger bonds between indium and nitrogen atoms, which, on one hand, allows to use higher temperatures during the growth and provides material with better quality. On the other hand, the ordering sets the limit of the In content of 25%, which cannot be overcome under realistic growth conditions.

“Apparently, a technological bottleneck hampers all the attempts to shift the emission from the green towards the yellow and the red regions of the spectra. Therefore, new original pathways are urgently required to overcome these fundamental limitations,” states Dr. Tobias Schulz, scientist at the Leibniz-Institut fuer Kristallzuechtung; “for example, growth of InGaN films on high quality InGaN pseudo-substrates that would reduce the strain in the growing layer.”

However, the discovery of ordering may help to overcome well known limitations of the InGaN material system: localization of charge carriers due to fluctuations in the chemical composition of the alloy. Growing stable ordered (In, Ga)N alloys with the fixed composition at high temperatures could thus improve the optical properties of devices.

A recent paper published in NANO showed the gas-solid reaction method provides a full coverage of the perovskite film and avoids damage from the organic solvent, which is beneficial for light capture and electrons transportation, resulting in a faster response time and stability for perovskite photodetectors.

A schematic illustration of hybrid perovskite photoconductivity visible region detector with high speed and high stability. The gas-solid reaction in replace of the traditional solution methods provides a non-solvent environment during the reaction process, constructs a high crystallization and a full coverage film to increase the light capture and transportation, as well as enhance a good stability in the humidity condition, leading to a high response performance for the photodetector. Credit: Dr. Guoqing Tong

A schematic illustration of hybrid perovskite photoconductivity visible region detector with high speed and high stability. The gas-solid reaction in replace of the traditional solution methods provides a non-solvent environment during the reaction process, constructs a high crystallization and a full coverage film to increase the light capture and transportation, as well as enhance a good stability in the humidity condition, leading to a high response performance for the photodetector. Credit: Dr. Guoqing Tong

Pervoskite materials have long been considered candidates in the semiconductor manufacturing due to their characteristics of high light absorption, carrier mobility and wider light spectrum. They are widely applied in solar cells, light-emitted devices and photodetectors. However, the organic solvent in the traditional solution method will damage the perovskite film and form unstable phases during the synthesis process, which makes the perovskite film decompose quickly in wet conditions, limiting the practical application of perovskite devices. Considering the significant influence of the solvent, a team of researchers from Dongchang college of Liaocheng University and Hefei University of Technology proposed a new gas-solid process to fabricate the perovskite film. This non-solvent approach provides high crystallization and full coverage film in lower vacuum and low temperature systems.

The researchers investigated the morphology, light absorption and the crystal phases of the perovskite film at the different annealing temperature after gas-reaction to obtain the high-quality perovskite film. The devices exhibited high responsivity and detectivity of 5.87AW-1 and 1012 Jones. The response time of the device is estimated to be 248 μs/207 μs, which is faster than most previous reports via the solution method. Remarkably, the responsivity and detectivity are estimated to be 0.26 AW-1, 2.13×1010 Jones after lasting exposure in air (25oC, RH~40%) for up to two months. This improvement of the stability of the devices demonstrates that the well-controlled vapor deposition method allows a thorough removal of the residual solvents (i.e. DMF, DMSO et. al) and thus effectively promotes a high-quality crystallization of perovskite grains, reducing the metastable phases among the thin films.

This work was financed by Science and Technology Plan Project of Shandong Higher Education Institutions, NSFC and Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology of China.

Littelfuse, Inc. today introduced four new series of 1200V silicon carbide (SiC) Schottky Diodes from its GEN2 product family, which was originally released in May 2017.

The LSIC2SD120A08 Series, LSIC2SD120A15 Series, and LSIC2SD120A20 Series offer current ratings of 8A, 15A ,20A, respectively and are provided in the popular TO-220-2L package. Additionally, the LSIC2SD120C08 Series offers a current rating of 8A in a TO-252-2L package. The merged p-n Schottky (MPS) device architecture of the GEN2 SiC Schottky Diodes enhances surge capability and reduces leakage current. Replacing standard silicon bipolar power diodes with the new GEN2 SiC Schottky Diodes allows circuit designers to reduce switching losses dramatically, accommodate large surge currents without thermal runaway, and operate at junction temperatures as high as 175°C. This allows for substantial increases in power electronics system efficiency and robustness.

Typical applications for these new GEN2 SiC Schottky Diodes include:

  • Active power factor correction (PFC).
  • Buck or boost stages in DC-DC converters.
  • Free-wheeling diodes in inverter stages.
  • High-frequency output rectification.

The markets they can serve include industrial power supplies, solar energy, industrial motor drives, welding and plasma cutting, EV charging stations, inductive cooking fields and many others.

“The latest GEN2 SiC Schottky Diodes are ideal solutions for circuit designers who need to reduce switching losses, accommodate large surge currents without thermal runaway, and operate at higher junction temperatures,” said Michael Ketterer, Global Product Marketing Manager, Power Semiconductors at Littelfuse. “They expand the component options available to circuit designers striving to improve the efficiency, reliability, and thermal management of the latest power electronics systems.”

LSIC2SD120A08 Series, LSIC2SD120A15 Series, and LSIC2SD120A20 Series GEN2 1200V SiC Schottky Diodes are available in TO-220-2L packages in tubes in quantities of 1,000. Meanwhile,LSIC2SD120C08 Series GEN2 1200V SiC Schottky Diodes are available in TO-252-2L package in tape and reel in quantities of 2,500.  Sample requests may be placed through authorized Littelfuse distributors worldwide.

An international team of researchers from ETH Zurich, IBM Research Zurich, Empa and four American research institutions have found the explanation for why a class of nanocrystals that has been intensively studied in recent years shines in such incredibly bright colours. The nanocrystals contain caesium lead halide compounds that are arranged in a perovskite lattice structure.

Three years ago, Maksym Kovalenko, a professor at ETH Zurich and Empa, succeeded in creating nanocrystals – or quantum dots, as they are also known – from this semiconductor material. “These tiny crystals have proved to be extremely bright and fast emitting light sources, brighter and faster than any other type of quantum dot studied so far,” says Kovalenko. By varying the composition of the chemical elements and the size of the nanoparticles, he also succeeded in producing a variety of nanocrystals that light up in the colours of the whole visible spectrum. These quantum dots are thus also being treated as components for future light-emitting diodes and displays.

In a study published in the most recent edition of the scientific journal Nature, the international research team examined these nanocrystals individually and in great detail. The scientists were able to confirm that the nanocrystals emit light extremely quickly. Previously-studied quantum dots typically emit light around 20 nanoseconds after being excited when at room temperature, which is already very quick. “However, caesium lead halide quantum dots emit light at room temperature after just one nanosecond,” explains Michael Becker, first author of the study. He is a doctoral student at ETH Zurich and is carrying out his doctoral project at IBM Research.

A cesium lead bromide nanocrystal under the electron microscope (crystal width: 14 nanometer). Individual atoms are visible as points. Credit: ETH Zurich / Empa / Maksym Kovalenko

A cesium lead bromide nanocrystal under the electron microscope (crystal width: 14 nanometer). Individual atoms are visible as points. Credit: ETH Zurich / Empa / Maksym Kovalenko

Electron-hole pair in an excited energy state

Understanding why caesium lead halide quantum dots are not only fast but also very bright entails diving into the world of individual atoms, light particles (photons) and electrons. “You can use a photon to excite semiconductor nanocrystals so that an electron leaves its original place in the crystal lattice, leaving behind a hole,” explains David Norris, Professor of Materials Engineering at ETH Zurich. The result is an electron-hole pair in an excited energy state. If the electron-hole pair reverts to its energy ground state, light is emitted.

Under certain conditions, different excited energy states are possible; in many materials, the most likely of these states is called a dark one. “In such a dark state, the electron hole pair cannot revert to its energy ground state immediately and therefore the light emission is suppressed and occurs delayed. This limits the brightness”, says Rainer Mahrt, a scientist at IBM Research.

No dark state

The researchers were able to show that the caesium lead halide quantum dots differ from other quantum dots: their most likely excited energy state is not a dark state. Excited electron-hole pairs are much more likely to find themselves in a state in which they can emit light immediately. “This is the reason that they shine so brightly,” says Norris.

The researchers came to this conclusion using their new experimental data and with the help of theoretical work led by Alexander Efros, a theoretical physicist at the Naval Research Laboratory in Washington. He is a pioneer in quantum dot research and, 35 years ago, was among the first scientists to explain how traditional semiconductor quantum dots function.

Great news for data transmission

As the examined caesium lead halide quantum dots are not only bright but also inexpensive to produce they could be applied in television displays, with efforts being undertaken by several companies, in Switzerland and world-wide. “Also, as these quantum dots can rapidly emit photons, they are of particular interest for use in optical communication within data centres and supercomputers, where fast, small and efficient components are central,” says Mahrt. Another future application could be the optical simulation of quantum systems which is of great importance to fundamental research and materials science.

ETH professor Norris is also interested in using the new knowledge for the development of new materials. “As we now understand why these quantum dots are so bright, we can also think about engineering other materials with similar or even better properties,” he says.

The use of LEDs to illuminate buildings and outdoor spaces reduced the total carbon dioxide (CO2) emissions of lighting by an estimated 570 million tons in 2017. This reduction is roughly equivalent to shutting down 162 coal-fired power plants, according to IHS Markit (Nasdaq: INFO), a world leader in critical information, analytics and solutions. LED lighting uses an average of 40 percent less power than fluorescents, and 80 percent less than incandescents, to produce the same amount of light.

“The efficiency of LEDs is essentially what makes them environmentally friendly,” said Jamie Fox, principal analyst, lighting and LEDs group, IHS Markit. “Therefore, LED conversion is unlike other measures, which require people to reduce consumption or make lifestyle changes.”

LED component and lighting companies were responsible for reducing the global carbon (CO2e) footprint by an estimated 1.5 percent in 2017, and that number is likely to continue to grow as more LEDs are installed around the world.

LEDs have other positive environmental benefits, too. For example, LEDs have a longer life span than traditional bulbs and fewer are produced, so the emissions and pollution associated with the production, shipping, sale and disposal of the products is lowered. Secondly, unlike fluorescents, LEDs do not contain mercury. LEDs also decrease air pollution, since most electrical energy is still generated by burning fossil fuels. “While other activities affect climate change more than lighting does, it is still a very strong contribution from a single industry sector,” Fox said.

IHS Markit has tracked the market share for top LED component suppliers for many years. Based on an analysis of this data, Nichia can claim credit for having saved the most carbon overall — accounting for 10 percent of all LED lighting reduction achieved in 2017, which translates into 57 million tons of CO2 — about the same as 16 coal plants. Cree followed Nichia with 8 percent, while Lumileds, Seoul Semiconductor, MLS, Samsung and LG Innotek each have a share in the range of 4 percent to 7 percent.

Savings achieved by each company relate to the energy saved by the use of that company’s components while installed in lighting applications. It does not include a whole lifecycle analysis, which would likely lead to a small additional positive benefit, due to the longer life of LEDs.

“LED component companies and lighting companies have transformed their industry,” Fox said. “They are fighting climate change much more effectively than other industries, and they should be given credit for it. Unlike in other industry sectors, workers at LED companies can honestly say that by selling more of their products, they are helping to reduce global warming.”

IHS Markit figures are only based on the lighting market. They do not include energy saved by LEDs that replaced other technologies in other sectors, such as automotive and consumer technology.

More than 70,000 players in the electronics manufacturing industry are expected to descend upon SEMICON China for technology and innovation insights to accelerate already strong industry growth. March 14-16, 2018, at the Shanghai New International Expo Centre (SNIEC), SEMICON China 2018 will bring together top executives and technologists in six exhibition halls, the most ever in the event’s 30-year history, to find opportunities in key focus areas including Smart Automotive and Smart Manufacturing, Green Tech, Advanced Technology, and Power and Compound Semiconductors.

Concurrent with FPD China, SEMICON China 2018, the largest and most influential gathering of the semiconductor supply chain in China, is now open for visitor registration.

SEMICON China technical forums will address the most pressing industry topics:

  • CSTIC 2018: Staged in conjunction with SEMICON China, this has ranked among the largest and most comprehensive annual semiconductor technology conferences in China since 2000. March 11-12, 2018, CSTIC 2018 will feature nine symposiums covering all aspects of semiconductor technology, with a focus on manufacturing and advanced technology.
  • SIIP: Tech Innovation and Investment Forum: SIIP is a key international platform for semiconductor industry investment in China. Informed by China’s IC policy to fund key semiconductor sectors, leaders of China’s National IC Fund and municipal IC funds will join leaders from global investment institutions to discuss hot opportunities in China semiconductor investment – and applications such as Artificial Intelligence (AI).
  • Win-Win: Build China’s IC Ecosystem: Spurred by a strong market outlook, policy and the national fund, fab construction in China will surge over the next five years, with OSAT (Outsourced Semiconductor Assembly and Test) making strategic investments. Industry leaders will explore how China’s semiconductor manufacturing industry will strengthen its core competency, prioritize resources, revisit its business model, and thrive in the electronics ecosystem.
  • Power and Compound Semiconductor International Forum: Among the largest power and compound semiconductor industry forums in Asia, this two-day event features four sessions: Wide Band Gap Power Electronics, Optoelectronics, Compound Semiconductor in Communications, and Emerging Power Device Technology
  • Smart Automotive Forum – AI Inside: Top automotive, electronic, AI and technology executives will gather to discuss the future of the rapidly disrupting automotive industry.
  • China Memory Strategic Forum: Driven by market needs and policy support, three new Chinese Memory foundries are accelerating memory development. Industry leaders will explore ways multinationals can benefit more from China’s memory market, China can better leverage its technical strength, and Chinese companies can enhance research and development collaboration with global partners.
  • Green High-Tech Facility Forum: With more than 10 fabs now under construction in China,China’s semiconductor industry is entering a stage of rapid growth. Green Tech leaders will discuss how China can improve factory design and construction; optimize energy efficiency of semiconductor manufacturing equipment; enhance machine platform stability, chemicals and gas management, and wastewater treatment; and improve risk management.
  • Smart Manufacturing Forum: The semiconductor industry must be proactive in all aspects of smart manufacturing. This session will address automation, product tractability, cost and cycle time reduction, enhancements in productivity and yield, and efficiency improvements in front- and back-end factories.
  • Semiconductor New Technology Conference: The best way to promote new technology is through direct customer interaction and collaboration. Join this conference to discuss your new IC, new IOT solution, new machine or new material with more 200 customers from around the world.
  • 2018 China Display Conference-Emerging Display Forum: Join this forum, concurrent with FPD China 2018, to exchange ideas on emerging display technologies and future development.
  • MSIG International IOT Conference 2018: MEMS, sensors, IC, NB-IoT, 5G and smart application experts will share their insights on the IoT market and how to maximize the value of IoT applications.

SEMICON China also features three theme pavilions:

  • IC Manufacturing: See products, technologies, and manufacturing solutions focused on serving China’s fabless IC community, from design to final manufacturing.
  • LED and Sapphire: Learn how China has become the world’s largest sapphire manufacturing center.
  • ICMTIA: See the local IC material industry demonstrate its capabilities to support semiconductor industry growth.

Advanced Micro-Fabrication Equipment Inc. (AMEC) today announced that the Fujian High Court in China has granted AMEC’s motion for an injunction against Veeco Instruments (Shanghai) Co. Ltd. (Veeco Shanghai). The injunction prohibits Veeco Shanghai from importing, manufacturing, selling or offering for sale to any third party any MOCVD systems and wafer carriers used in the MOCVD systems that would infringe AMEC’s patent CN 202492576 in China. The patent covers AMEC’s proprietary wafer carrier and spindle-locking and synchronization technology. The injunction covers Veeco’s TurboDisk EPIK 700 system, EPIK 700 C2 system, and EPIK 700 C4 system, as well as the related wafer carriers used in the MOCVD systems. AMEC believes that the ruling should also cover Veeco’s EPIK 868 system and related wafer carriers, since AMEC believes that the EPIK 868 system also uses AMEC’s patented technology involved in the action.

The ruling, which is unappealable, takes effect immediately. The stringent injunction terms expose the nature of Veeco Shanghai’s flagrant violation of AMEC’s intellectual property (IP) and confirms that Veeco Shanghai does not respect AMEC’s IP rights.

AMEC filed the patent infringement claim against Veeco Shanghai in the Fujian High Court on July 13th 2017. The motion requested a permanent injunction against Veeco Shanghai, as well as compensation for monetary damages of more than 100 million RMB Yuan (approx. US$15 million).

The injunction follows a previous victory for AMEC relating to the same action. When AMEC filed its claim in July, Veeco Shanghai responded by filing a patent invalidation request with the Patent Re-examination Board (PRB) of the State Intellectual Property Office (SIPO) in China. A second request to invalidate the same AMEC patent was filed concurrently by an individual. The PRB held separate hearings for the two requests. On Nov. 24th2017, the PRB dismissed both requests,thereby upholding the validity of the patent.

AMEC invested heavily in R&D and IP protection for this key technology. AMEC first developed the technology, filed a series of patents to protect the innovations, and installed equipment containing the technology at a number of LED production fabs in China. Veeco later followed by using the same locking approach in its MOCVD system to improve the tool’s performance. After AMEC filed the patent disputed by Veeco Shanghai, Veeco Instruments Inc. (Veeco US) submitted a similar patent application, and subsequently used this technology in its MOCVD system, thus infringing AMEC’s patent.

“The court’s ruling and the PRB’s decisions together confirm in no uncertain terms that AMEC’s technology contains unique innovations, and that our patent portfolio is comprehensive, robust and highly valuable,” said Dr. Zhiyou Du, Senior Vice President, COO & General Manager of AMEC’s MOCVD Product Division. “We are very pleased with the court’s decision. We take IP enforcement seriously, and we will not tolerate any violation of our IP rights. Indeed, we will aggressively pursue instances of infringement, and vigorously protect our IP portfolio.”

Dr. Du continued: “As a supplier of high-end micro-fabrication equipment to leading global manufacturers of ICs, LEDs and power devices, AMEC attaches great importance to IP protection. Since our founding in 2004, we have independently developed unique technologies to enable our customers worldwide. Therefore, for more than a decade, we have defended our IP in domestic and international jurisdictions when challenged, and prevailed in every case. We respect the IP of our customers and competitors, and we expect the same regard for our IP.”

In a separate development, AMEC filed a motion on Dec. 8th 2017 to invalidate a Veeco patent with the Patent Trial and Appeal Board (PTAB) of the US Patent & Trademark Office (USPTO). The patent, US 6,726,769 filed in 2001, covers a detachable wafer carrier technology. It was asserted in an infringement action initiated in the US by Veeco US against AMEC’s supplier of wafer carriers for MOCVD systems. AMEC believes that the Veeco patent is invalid because the technology was definitively and clearly disclosed in many prior patents and publications as far back as the early 1960s. Therefore, the Veeco patent does not meet standard patent law requirements. Besides filing to invalidate the patent in the US, AMEC has already filed motions to invalidate counterpart patent families in China and South Korea.

AMEC intends to also challenge a second Veeco US patent (US 6,506,252) involved in the same US infringement action. A motion to that effect will soon be filed with the PTAB.

Dr. Gerald Yin, Chairman and CEO of AMEC, said: “We are confident that AMEC will prevail in its action against Veeco Shanghai, and that Veeco Shanghai will be required to pay for the enormous cost of its infringement beginning in 2014 when Veeco US launched its EPIK 700 system. In addition, we believe that our supplier will eventually prevail in its US case.”

Dr. Yin further noted: “AMEC is an innovative company with extensive expertise in providing breakthrough technologies that enable customers with competitive advantages. Our products have earned market success for their differentiation and value. Naturally, we prefer to focus our efforts on providing such innovative products and stellar service to customers instead of wasting time and resources on litigation. That’s why we’re fully committed to reaching a positive resolution with Veeco, and working diligently to achieve that goal.”

Cree, Inc. (Nasdaq: CREE) announces the commercial availability of the XLamp®XD16 LED, the industry’s first Extreme Density LED, which delivers up to 5 ½ times higher lumen density than Cree’s previous generation of high power LEDs. Built on Cree’s groundbreaking NX Technology Platform, the XD16 LED combines breakthrough lumen density, low optical cross-talk, unsurpassed thermal contact and ease of system manufacturing to enable innovative new designs for a broad spectrum of lighting applications, such as color-tuning, street, portable and industrial.

“Cree’s new XD16 LED delivers an incredible amount of light output for such a tiny package,” said Joe Skrivan, senior technical director at Black Diamond Equipment. “The XD16 LED’s breakthrough lumen output and peak intensity is a game-changer for our climbing headlamp products because we can design better beam control and decrease the overall size and weight compared to existing designs.”

The XLamp XD16 LED delivers a lumen density of more than 284 lumens per square-millimeter, which is the highest level achieved by a commercially available lighting-class LED. The ceramic-based XD16 LED utilizes the proven XQ footprint and successfully addresses challenges with luminaire manufacturing, thermal design, optical design and reliability faced by competing LEDs. For example, the XD16 LED reduces system-level optical loss by up to three times versus competing technologies when LEDs are placed close together on a board. This improvement translates into fewer wasted lumens and higher efficacy for lighting products.

“Cree’s new Extreme Density LED demonstrates that true LED innovation improves our customers’ system performance without forcing compromise,” said Dave Emerson, Cree LEDs executive vice president and general manager. “The XD16 LED delivers unmatched lumen density without the design and manufacturing challenges associated with inferior LED technology approaches. Now, lighting manufacturers can easily achieve previously unattainable levels of light output and efficacy in their existing form factors.”

The new LEDs are characterized and binned at 85°C, available in ANSI White, EasyWhite® 3- and 5-step color temperatures (2700K – 6500K), and CRI options of 70, 80 and 90. Product samples are available now and production quantities are available with standard lead times.

Texas Instruments (TI) (NASDAQ: TXN) today introduced the first 3-channel high-side linear automotive light-emitting diode (LED) controller without internal MOSFETs which gives designers greater flexibility for their lighting designs. The TPS92830-Q1’s novel architecture enables higher power and better thermal dissipation than conventional LED controllers, and are particularly beneficial for automotive LED lighting applications that require high performance and reliability.

Conventional LED drivers integrate the MOSFET, which limits designers’ ability to customize features. With that type of driver, designers often must make significant design modifications to achieve the desired system performance. The TPS92830-Q1 LED controller’s flexible on-board features give designers the freedom to select the best MOSFET for their system requirements. With this new approach, designers can more quickly and efficiently optimize their lighting power designs for automotive system requirements and desired dimming features.

Key features and benefits

  • Flexibility: The on-chip pulse-width modulation (PWM) generator or PWM input enables flexible dimming. Designers can use either the analog control or PWM to manage an output current of more than 150 mA per channel, to power automotive rear combination lamps and daytime running lights.
  • Improved thermal dissipation: By pairing the LED controller with an external MOSFET, the designer can achieve the required high power output while distributing the power across the controller and MOSFET to avoid system overheating. By retaining linear architecture, the TPS92830-Q1 provides improved electromagnetic interference (EMI) and electromagnetic compatibility (EMC) performance.
  • Greater system reliability: Advanced protection and built-in open and short detection features help designers meet original equipment manufacturer (OEM) system reliability requirements. The output current derating feature protects the external MOSFET under high voltage conditions to ensure system reliability.

The TPS92830-Q1 expands TI’s extensive portfolio of LED drivers, design tools and technical resources that help designers implement innovative automotive lighting features.

High-power white LEDs face the same problem that Michigan Stadium faces on game day — too many people in too small of a space. Of course, there are no people inside of an LED. But there are many electrons that need to avoid each other and minimize their collisions to keep the LED efficiency high. Using predictive atomistic calculations and high-performance supercomputers at the NERSC computing facility, researchers Logan Williams and Emmanouil Kioupakis at the University of Michigan found that incorporating the element boron into the widely used InGaN (indium-gallium nitride) material can keep electrons from becoming too crowded in LEDs, making the material more efficient at producing light.

This is the crystal structure of a BInGaN alloy. Using atomistic calculations and high-performance supercomputers at the NERSC facility, Logan Williams and Emmanouil Kioupakis at the University of Michigan predicted that incorporating boron into the InGaN active region of nitride LEDs reduces or even eliminates the lattice mismatch with the underlying GaN layers while keeping the emission wavelength approximately the same. The lattice matching enables the growth of thicker active regions and increases the efficiency of LEDs at high power. Credit: Michael Waters and Logan Williams

This is the crystal structure of a BInGaN alloy. Using atomistic calculations and high-performance supercomputers at the NERSC facility, Logan Williams and Emmanouil Kioupakis at the University of Michigan predicted that incorporating boron into the InGaN active region of nitride LEDs reduces or even eliminates the lattice mismatch with the underlying GaN layers while keeping the emission wavelength approximately the same. The lattice matching enables the growth of thicker active regions and increases the efficiency of LEDs at high power. Credit: Michael Waters and Logan Williams

Modern LEDs are made of layers of different semiconductor materials grown on top of one another. The simplest LED has three such layers. One layer is made with extra electrons put into the material. Another layer is made with too few electrons, the empty spaces where electrons would be are called holes. Then there is a thin middle layer sandwiched between the other two that determines what wavelength of light is emitted by the LED. When an electrical current is applied, the electrons and holes move into the middle layer where they can combine together to produce light. But if we squeeze too many electrons in the middle layer to increase the amount of light coming out of the LED, then the electrons may collide with each other rather than combine with holes to produce light. These collisions convert the electron energy to heat in a process called Auger recombination and lower the efficiency of the LED.

A way around this problem is to make more room in the middle layer for electrons (and holes) to move around. A thicker layer spreads out the electrons over a wider space, making it easier for them to avoid each other and reduce the energy lost to their collisions. But making this middle LED layer thicker isn’t as simple as it sounds.

Because LED semiconductor materials are crystals, the atoms that make them up must be arranged in specific regular distances apart from each other. That regular spacing of atoms in crystals is called the lattice parameter. When crystalline materials are grown in layers on top of one another, their lattice parameters must be similar so that the regular arrangements of atoms match where the materials are joined. Otherwise the material gets deformed to match the layer underneath it. Small deformations aren’t a problem, but if the top material is grown too thick and the deformation becomes too strong then atoms become misaligned so much that they reduce the LED efficiency. The most popular materials for blue and white LEDs today are InGaN surrounded by layers of GaN. Unfortunately, the lattice parameter of InGaN does not match GaN. This makes growing thicker InGaN layers to reduce electron collisions challenging.

Williams and Kioupakis found that by including boron in this middle InGaN layer, its lattice parameter becomes much more similar to GaN, even becoming exactly the same for some concentrations of boron. In addition, even though an entirely new element is included in the material, the wavelength of light emitted by the BInGaN material is very close to that of InGaN and can be tuned to different colors throughout the visible spectrum. This makes BInGaN suitable to be grown in thicker layers, reducing electron collisions and increasing the efficiency of the visible LEDs.

Although this material is promising to produce more efficient LEDs, it is important that it can be realized in the laboratory. Williams and Kioupakis have also shown that BInGaN could be grown on GaN using the existing growth techniques for InGaN, allowing quick testing and use of this material for LEDs. Still, the primary challenge of applying this work will be to fine tune how best to get boron incorporated into InGaN at sufficiently high amounts. But this research provides an exciting avenue for experimentalists to explore making new LEDs that are powerful, efficient, and affordable at the same time.