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You're darn right they're part of the compounds, but we're also proud to say that the LED segment has "graduated" and can benefit from publications that are more dedicated to those topics. For news on the broad LED industry, outside of general lighting, along with the materials and technology supply chain, visit LIGHTimes Online. For a higher level view of LEDs in general lighting, you can visit Solid State Lighting Design, which covers packaged "lighting quality" LEDs through subsystems, luminaires and application stories.

Examination of Single Perovskite Crystals Reveals Much Untapped Potential for Solar and LEDs
LIGHTimes News Staff

February 3, 2015...Engineers at the University of Toronto have for the first time demonstrated some of the optoelectronic properties of pure perovskite crystals. This emerging family of solar-absorbing materials and understanding their optoelectronic properties could lead to more efficient and cheaper solar panels and LEDs. Through their examination of the properties of single perovskite materials, the researchers revealed that perovskites still have much untapped potential for use in solar panels and LEDs.

The perovskites, are particularly good at absorbing visible light, but they had never before been thoroughly studied as perfect single crystals. The researchers employed a new technique to grow pure perovskite crystals and then studied electrons move through the material as light is converted to electricity.

Professor Ted Sargent of the University of Toronto's Edward S. Rogers Sr. Department of Electrical & Computer Engineering and Professor Osman Bakr of the King Abdullah University of Science and Technology (KAUST) used a combination of laser-based techniques to measure certain properties of the perovskite crystals. They tracked down the rapid motion of electrons in the material. From this they were able to determine the diffusion length--how far electrons can travel without imperfections in the material trapping them--as well as mobility—how fast the electrons can move through the material. This week, they published their work in the journal Science.

“Our work identifies the bar for the ultimate solar energy-harvesting potential of perovskites,” said Riccardo Comin, a post-doctoral fellow with the Sargent Group. “With these materials it’s been a race to try to get record efficiencies, and our results indicate that progress is slated to continue without slowing down..”

Certified efficiencies of perovskites have reached new heights of just over 20 percent in recent years. Such efficiency starts to approach the performance of the state-of-the-art commercial-grade silicon-based solar panels mounted in deserts in spain and on roofs in California.

“In their efficiency, perovskites are closely approaching conventional materials that have already been commercialized,” said Valerio Adinolfi, a PhD candidate in the Sargent Group and co-first author of the paper. “They have the potential to offer further progress on reducing the cost of solar electricity in light of their convenient manufacturability from a liquid chemical precursor.

In solar panels, light hits the surface of the perovskite material and gets absorbed, thereby exciting electrons. These electrons easily traverse the crystal structure to electrical contacts on the underside, creating electric current. In LEDs the process happens in reverse. The slab is first powered with electricity, which injects electrons and then releases energy as light.

The Sargent Group is conducting parallel work that aims to improve the performance of solar-absorbing particles called colloidal quantum dots. “Perovskites are great visible-light harvesters, and quantum dots are great for infrared,” said Professor Sargent. “The materials are highly complementary in solar energy harvesting in view of the sun’s broad visible and infrared power spectrum.”

“In future, we will explore the opportunities for stacking together complementary absorbent materials,” said Dr. Comin. “There are very promising prospects for combining perovskite work and quantum dot work for further boosting the efficiency.”

Graphene and LEDs Made with Super-Thin Crystals Pave the Way for Flexible Electronics
LIGHTimes News Staff

February 3, 2015...Researchers from the University of Manchester and the University of Shiefield have successfully created extremely flat LEDs with grapheme and 10 to 40 atom thick crystals. Nobel Laureate Sir Kostya Novoselov led the team that engineered the LEDs on the atomic level. They published the results in the Nature Materials. The unique properties of Graphene may someday allow the creation of semi-transparent, flexible electronics, according to the researchers.

The new research demonstrated that graphene and related materials that are essentially 2D could be employed in light emitting devices for the next-generation of mobile phones, TVs, and tablets and televisions making them incredibly thin, and even flexible, durable and semi-transparent. The researchers combined different ultra-thin crystals that can emit light from across their whole surfaces. Such LEDs may one day form flexible and semitransparent displays.

One-atom thick graphene was first isolated and explored in 2004 at The University of Manchester. Other 2D materials, such as molybdenum disulphid and boron nitiride have been discovered since then, opening new areas of research and potential applications. Stacked layers of various "2D" materials, with the addition of quantum wells to control the movement of electrons have now revealed the potential for customized, grapheme-based optoelectronics.

Freddie Withers, the University of Manchester's Royal Academy of Engineering Research Fellow, who led the devices' production said, “As our new type of LED’s only consist of a few atomic layers of 2D materials they are flexible and transparent. We envisage a new generation of optoelectronic devices to stem from this work, from simple transparent lighting and lasers and to more complex applications.”

Explaining the construction of the LED device, Sir Kostya Novoselov said, “By preparing the heterostructures on elastic and transparent substrates, we show that they can provide the basis for flexible and semi-transparent electronics.

“The range of functionalities for the demonstrated heterostructures is expected to grow further on increasing the number of available 2D crystals and improving their electronic quality.”

Professor Alexander Tartakovskii, from The University of Sheffield claimed, “Despite the early days in the raw materials manufacture, the quantum efficiency (photons emitted per electron injected) is already comparable to organic LEDs.”

2015 Draper Prize for Engineering Goes to LED Lighting Pioneers
LIGHTimes News Staff

January 8, 2015...The US National Academy of Engineering (NAE) has awarded the 2015 Charles Stark Draper Prize for Engineering to Nick Holonyak Jr, Isamu Akasaki, M. George Craford, Russell Dupuis, and Shuji Nakamura for “the invention, development, and commercialization of materials and processes for LEDs. The prize will be presented at a gala dinner in Washington D.C. on 24 February.

In 1988, in honor of the memory of Charles Stark Draper, known as the 'father of inertial navigation', the National Association of Engineering (NAE) established the $500,000 annual Draper Prize at the request of Charles Stark Draper Laboratory Inc.

The Draper Prize, which is NAE's highest honor, is given to engineers for achievements that have significantly benefited society by improving the quality of life, and/or expanding access to information.

“These prize-winning engineers were the pioneers in a technology that has changed the world we live in, from the aesthetics in our homes, to advancements in our visual capabilities, and to environmental stewardship,” stated NAE president C D. Mote Jr.

In 1962, Nick Holonyak Jr created the first visible, red LED while working at General Electric. He studied III-V materials including gallium arsenide (GaAs) and found that adding phosphorus (P) to gallium arsenide resulted in a shortened wavelength. He ultimately tuned the GaAsP LED to emit visible red lightIn 1972, George Craford invented the first yellow LED and increased its brightness by adding nitrogen to the GaAsP LED. Craford also participated in developing processes for the first large-scale commercial production of red LEDs. He later led work that resulted in the first high-brightness yellow and red LEDs, available in 1992, and subsequently contributed to the development of high-power white LEDs.

Russell Dupuis developed and refined the metal-organic chemical vapor deposition (MOCVD) process in 1977, which enabled the production of high-brightness LEDs and is now the basis of nearly all production of high-brightness LEDs, and other high-speed optoelectronic devices including laser diodes and solar cells.

In 1987 Isamu Akasaki used MOCVD to grow high-quality gallium nitride crystals on sapphire substrates, creating the first blue LED (which later enabled efficient, bright, white light sources).

In 1992, Shuji Nakamura also made important contributions to InGaN-based high-brightness double-heterostructure blue LEDs, as well as laser diodes that allowed development of the high-density digital video disk (Blu Ray DVD). Nakamura, who is a professor of materials and of electrical & computer engineering at University of California Santa Barbara (UCSB), received the 2014 Nobel Prize in Physics (shared with professors Isamu Akasaki and Hiroshi Amano) for helping develop the first high-brightness blue LED.

British Reseachers Create Simulations that More Accurately Predict Properties of GaN
LIGHTimes News Staff

January 8, 2015...Researchers from University College London (UCL) worked with teams at Daresbury Laboratory and the University of Bath to reveal the complex properties of gallium nitride using computer simulations. Accurate predictions of these properties can help make better blue LEDs and predict their output before actual fabrication.

LEDs employ two layers of semiconductors: a conduction layer with electrons available and a layer with positive charges or holes. When an electron and a hole meet, they emit a photon (light particle). A cristalline film of a particular material--GaN for blue LEDs--is grown and then doped. Dopants donate an extra positive or negative charge to the material.

GaN, the key material for blue LEDs, has a large energy gap between electrons and holes (known as a wide bandgap). The wide bandgap is essential for tuning the emitted photons to produce blue light. Doping to donate mobile negative charges in the material proved to be easy. However, donating positive charges from GaN failed completely. The innovation, which won the inventors of the blue LED the Nobel Prize for physics last year, required doping GaN with unexpectedly large amounts of magnesium.

"While blue LEDs have now been manufactured for over a decade," said John Buckeridge (UCL Chemistry), the study's lead author, "there has always been a gap in our understanding of how they actually work, and this is where our study comes in. Based on what is seen in other semiconductors such as silicon, you would expect each magnesium atom added to the crystal to donate one hole. But in fact, to donate a single mobile hole in GaN, at least a hundred atoms of magnesium have to be added. It's technically extremely difficult to manufacture GaN crystals with so much magnesium in them, not to mention that it's been frustrating for scientists not to understand what the problem was."

The team published details of their findings in the journal Physical Review Letters. The team used highly sophisticated computer simulations to accurately predict the unusual behavior of doped GaN at the atomic level. While a quantum mechanical model can make accurate predictions about perfect crystals with repeating patterns of atoms, such a model has difficulty dealing with defects which do not fit the repeating pattern of atoms. The computer simulations for accurate prediction of GaN crystals with some defects requires use of supercomputers because of the large numbers of atoms and their interactions.

"To make an accurate simulation of a defect in a semiconductor such as an impurity, we need the accuracy you get from a quantum mechanical model," said David Scanlon (UCL Chemistry), a co-author of the article.

"Such models have been widely applied to the study of perfect crystals, where a small group of atoms form a repeating pattern. Introducing a defect that breaks the pattern presents a conundrum, which required the UK's largest supercomputer to solve. Indeed, calculations on very large numbers of atoms were therefore necessary but would be prohibitively expensive to treat the system on a purely quantum-mechanical level."

The team solved the the issue with an approach pioneered in another Nobel Prize winning research: hybrid quantum and molecular modeling, the subject of 2013's Nobel prize in Chemistry. The new models simulate different parts of a complex chemical system with different levels of theory. Some previously unexplained experimental results about the behavior of GaN now fit with the new simulations

Richard Catlow (UCL Chemistry), one of the study's co-authors said, "Our simulation shows that the behavior of the semiconductor is much more complex than previously imagined, and finally explains why we need so much magnesium to make blue LEDs successfully."

"The simulation tells us that when you add a magnesium atom, it replaces a gallium atom but does not donate the positive charge to the material, instead keeping it to itself," Catlow said. "In fact, to provide enough energy to release the charge will require heating the material beyond its melting point. Even if it were released, it would knock an atom of nitrogen out of the crystal, and get trapped anyway in the resulting vacancy."

"In fact, to provide enough energy to release the charge will require heating the material beyond its melting point. Even if it were released, it would knock an atom of nitrogen out of the crystal, and get trapped anyway in the resulting vacancy," Catlow added.

Aron Walsh of Bath Chemistry noted, that the team is looking forward to using the new simulations to investigate the properties of heavily defective GaN and help develop alternative doping strategies to improve the efficiency of solid-state lighting.

Startup Allos Semiconductors now Offers Licensing for Azzurro's GaN-on-Si Patents and Technology
LIGHTimes News Staff

December 16, 2014...ALLOS Semiconductors GmbH, a newly founded company based in Dresden, Germany, who specializes in GaN-on-Si technology, announced that it has acquired all the patents and technology of former Azzurro Semiconductors at an auction. In addition to its existing offering of GaN-on-Si technology ALLOS is now making the AZZURRO technology platform available through technology transfer, licencing and customised development work.

In June of 2014, ALLOS Semiconductors was formed to help meet the growing demand for technology of growing gallium nitride on silicon substrates (GaN-on-Si). An increasing number of LED and power semiconductor companies want to be able to grow 150 and 200 mm GaN-on-Si wafers to supply cost-effective high-quality GaN devices that can be processed in standard silicon fabs.

Allos complements the GaN-on-Si technology licensing with advice on business and technology strategies and support for setting up GaN-on-Si operations all the way from establishing a epitaxial wafer fab to market entry.

Cubic GaN Shows Potential for LEDs
LIGHTimes News Staff

December 16, 2014...Anvil Semiconductors and the Cambridge Centre for GaN at the University of Cambridge report having grown cubic GaN on 3C-SiC (silicon carbide) wafers using MOCVD. Anvil produced the underlying 3C-SiC layers using the company's patented stress relief IP that enables growth of device quality silicon carbide on 100mm diameter silicon wafers. Anvil contends that the process can work with 150mm diameter wafers and possibly beyond without modification and is therefore suitable for industrial-scale applications. In a project funded by Innovate UK, the MOCVD growth trials at Cambridge resulted in single phase, cubic GaN. The layers, characterized by XRD, TEM, photoluminescence and AFM, have potential for LED applications.

According to the researchers, the cubic GaN may be able to remove the strong internal electric fields, which plague conventional green LEDs, impair recombination, and make it difficult to address high internal quantum efficiency (IQE). Also, the researchers note that cubic GaN has a narrower bandgap and improved p-type electrical properties compared to the conventional hexagonal GaN phase used for LEDs. Therefore, a commercializable process to produce cubic GaN on large diameter silicon wafers may help increase the efficiency and reduce the cost of LED lighting.

The team plans to continue development to eventually fabricate sample LEDs before looking for an industry partner to commercialize the technology.

Sanan Orders 50 MOCVD Reators from Veeco for LED Production
LIGHTimes News Staff

December 12, 2014...Veeco Instruments Inc. of Plainview, New York USA, announced that Sanan Optoelectronics, the largest LED manufacturer in China, has ordered 50 TurboDisc® EPIK700™ Gallium Nitride (GaN) Metal Organic Chemical Vapor Deposition (MOCVD) reactors for the production of LEDs. This order is the equivalent of 25 EPIK700 MOCVD “C2” (cluster) systems.

“Sanan chose the EPIK700 due to its industry leading cost of ownership model and excellent footprint efficiency,” said Zhiqiang Lin, vice chairman and CEO of Sanan. “Our beta testing of EPIK700 proved its production-worthiness, and we are confident in its capabilities and value to our Xiamen business expansion plans. Veeco has been a great partner for Sanan as we have solidified our position as the top LED manufacturer in China and increased our business outside of China as well.”

Veeco's EPIK700 MOCVD system uses the company's TurboDisc technology to achieve a cost per wafer savings of up to 20 percent compared to previous generation MOCVD systems. The savings comes through increased productivity, improved wafer uniformity, and reduced operating expenses.

“This large order from Sanan, the largest single purchase order Veeco has received since 2009, speaks volumes about the EPIK700’s production readiness and the recovery in the MOCVD market,” said John Peeler, Veeco’s chairman and CEO. “We are in a great position to continue to serve our LED customers with the best MOCVD technology and customer support, and remain the industry leader.”

EV Group Establishes Nanoimprint Lithography Competence Center
LIGHTimes News Staff

December 4, 2014...EV Group (EVG) based in St. Florian, Austria, a supplier of wafer bonding and lithography equipment, announced that it has established the NILPhotonics(TM) Competence Center. The NILPhotonics(TM) Competence Center assists customers in leveraging EVG's suite of nanoimprint lithography (NIL) solutions for new and enhance photonics products and applications including LEDs and photovoltaic (PV) cells.

EVG says that in LEDs NIL-enabled photonic structures can improve light extraction, and in PV cells NIL-enabled photonic structures can improve light capturing. Additionally, NIL-enabled photonic structures in laser diodes enable device characteristic tailoring and optimization to improve performance. The Competence Center includes dedicated, global process teams, pilot-line production facilities and services at its cleanrooms at EVG's headquarters in Austria and its subsidiaries in Japan and North America.

EVG says that the new NILPhotonics Competence Center builds on the company's more than 15 years of NIL experience and what the company claims to be the largest installed base of NIL systems worldwide. EVG's NIL equipment portfolio includes the recently introduced EVG7200 UV-NIL system, which supports EVG's next-generation SmartNIL(TM) large-area soft NIL process for high-volume manufacturing. The company boasts that the EVG7200 with SmartNIL provides unmatched throughput and cost-of-ownership advantages over competing NIL approaches.

"Nanoimprint lithography is an enabling technology for the design and manufacture of all kinds of photonic structures, which can significantly shorten time to market and lower cost of production compared to conventional technologies, such as electron-beam writing and stepper systems for optical lithography," stated Markus Wimplinger, corporate technology development and IP director at EV Group.

"For example, compared with conventional lithography, our full-wafer nanoimprinting technology can pattern true three-dimensional structures in the sub-micron to nano-range as well as features as small as 20 nm, which opens up a range of new photonic applications.

With our NILPhotonics Competence Center, we're not just providing our customers with the most advanced NIL systems; we're also working closely with them during product development to help them determine how best to optimize their product designs and processes to take advantage of the resolution and cost-of-ownership benefits that NIL brings."

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