Gallium nitride (GaN) based devices are attractive for harsh environment electronics because of their high chemical and the mechanical stability of GaN itself that has a higher atomic displacement energy than other semiconductor materials.

However, degradation mechanisms of GaN device under radiation environments is not clear mainly because devices consist of many different types of semiconductors, such as p-type and n-type layers in light emitting diode (LED), and each layer has different hardness to radiation.

Now, researchers at the Electronics-Inspired Interdisciplinary Research Institute (EIIRIS) and Department of Electrical and Electronic Information Engineering at Toyohashi University of Technology, and the Japan Atomic Energy Agency (JAEA) describe the physical mechanism of an observed increase in the resistance of p-type GaN irradiated with 380 keV protons compared with n-type GaN.

This image depicts two-terminal resistance of p- and n-type GaN as a function of proton fluence. This inset shows schematic of sample, and lines are guide for eyes.
Credit: Copyright (c) 2014 Toyohashi University of Technology.

The GaN-based LED structure shown in Fig.1 was irradiated with protons and the resulting electrical properties measured. Notably, the electrodes to measure the resistance of the p-type and n-type layers were produced independently using the clean room facilities at EIIRIS and the ion implanter in JAEA.

The two terminal resistance of the n-type GaN did not vary from its initial value after 1×1014 cm-2 proton irradiation, and remained of the same order after 1×1015 cm-2 protons. However, a clear increase of the resistance was found in the p-type GaN after 1×1014 cm-2 irradiation. The resistance increased further by six orders of magnitude after 1×1015 cm-2.

The observed increase of the resistance in p-type GaN is explained as being due to the lower initial carrier density than in n-type GaN due to a lack of efficient p-type doping technology for GaN, which is a key for the realization of novel devices operable in harsh environments.

Samsung Electronics Co. today introduced new chip-on-board (COB) LED package products, the LC006B and LC008B, with six and eight watts of power respectively. The new packages join five others in Samsung’s popular LC series (LC013B, LC019B, LC026B, LC033B and LC040B), to complete its COB package line-up.

“With the introduction of our new under-10 watt COB packages, we are signaling our intent to aggressively target the indoor LED lighting market,” said Bangwon Oh, Senior Vice President, Strategic Marketing Team, LED Business, Samsung Electronics. “Samsung will continue to advance its LED technology and business objectives by providing lighting manufacturers with the best in LED lighting components, delivering exceptionally high-quality LED package and engine products and services that reliably meet customer needs,” he added. “We remain dedicated to increasing our breadth of market solutions, to further grow our LED lighting component business.”

A chip-on-board LED package provides a single light source that combines multiple LED chips to achieve higher light intensity and uniformity, while simplifying luminaire design.

The LC006B and LC008B offer high-efficacy levels of 140lm/W and 142lm/W at 5000K CCT, respectively. The new packages will support a wide range of CCT (Correlated Color Temperature) specifications from 2700K to 5000K with a CRI (Color Rendering Index) over 80. They also feature a compact package size with an 8mm LES (Light Emitting Surface) and a package structure that can be easily connected with holders or screw mounts for greater installation convenience.

Samsung’s LC series has gained widespread attention for delivering high luminance from a small LES, as well as low heat resistance and outstanding light efficacy. The LC packages also feature high color uniformity with 3-step MacAdam ellipses and consistently superior light quality.

Samsung COB LED lighting solutions now can be used in a significantly wider range of applications, including downlight for home lighting, flood light for industrial lighting, and spotlight and downlight for commercial lighting.

Cree, Inc. announced a breakthrough in lighting-class LED performance with its SC5 Technology Platform. The new platform powers the next generation of lighting with the introduction of Extreme High Power (XHP) LEDs. This new class of LEDs can reduce system costs by up to 40 percent in most lighting applications.

“As a technology company, we’re focused on breaking the performance barriers that really matter to the lighting industry,” said Chuck Swoboda, Cree Chairman and CEO. “The SC5 Technology Platform redefines what is possible in high-power LEDs by doubling the lumens out of a single LED, giving lighting manufacturers the flexibility to innovate significantly lower cost systems. This new platform establishes a new benchmark for LED lumens per wafer, which we believe will define the long-term success of our industry. This also validates our belief that high-power LED technology enables the best lighting system designs and a better lighting experience for end customers.”

The SC5 Technology Platform is built on Cree’s silicon carbide technology and features significant advancements in epitaxial structure, chip architecture and an advanced light conversion system optimized for best thermal and optical performance. With these advancements, the SC5 Technology Platform achieves unparalleled lumen density and longer lifetime at higher operating temperatures than previous LED technology, which can significantly reduce thermal, mechanical and optical costs at the system level.

“LEDs are no longer the most expensive portion of an LED lighting system, but they fundamentally determine the overall system performance and cost,” said Dave Emerson, vice president and general manager for Cree LEDs. “While other LED manufacturers only promise incrementally lower LED cost, our new Extreme High Power (XHP) LEDs leveraging the SC5 Technology™ Platform directly address the increased burden that thermal, mechanical and optical elements now place on total system cost.”

The first available family of XHP LEDs is the XLamp® XHP50 LED, delivering up to 2250 lumens at 19 watts from a 5.0×5.0 mm package. At its maximum current, the XHP50 provides twice the light output of the industry’s brightest single-die LED, the XLamp XM-L2 LED, at a similar lumens per watt and without increasing the package footprint. By leveraging Cree’s latest reliability innovations, the XHP50 is designed to maintain L90 lifetimes above 50,000 hours even at high temperature and current.

Duke University researchers have made fluorescent molecules emit photons of light 1,000 times faster than normal — setting a speed record and making an important step toward realizing superfast light emitting diodes (LEDs) and quantum cryptography.

This year’s Nobel Prize in physics was awarded for the discovery of how to make blue LEDs, allowing everything from more efficient light bulbs to video screens. While the discovery has had an enormous impact on lighting and displays, the slow speed with which LEDs can be turned on and off has limited their use as a light source in light-based telecommunications.

In an LED, atoms can be forced to emit roughly 10 million photons in the blink of an eye. Modern telecommunications systems, however, operate nearly a thousand times faster. To make future light-based communications using LEDs practical, researchers must get photon-emitting materials up to speed.

In a new study, engineers from Duke increased the photon emission rate of fluorescent molecules to record levels by sandwiching them between metal nanocubes and a gold film.

This is an artist’s representation of light trapped between a silver nanocube and a thin sheet of gold. When fluorescent molecules — shown in red — are trapped between the two, they emit photons up to 1,000 times faster than normal. Credit: Gleb Akselrod, Duke University

“One of the applications we’re targeting with this research is ultrafast LEDs,” said Maiken Mikkelsen, an assistant professor of electrical and computer engineering and physics at Duke. “While future devices might not use this exact approach, the underlying physics will be crucial.”

Mikkelsen specializes in plasmonics, which studies the interaction between electromagnetic fields and free electrons in metal. In the experiment, her group manufactured 75nm silver nanocubes and trapped light between them, greatly increasing the light’s intensity.

When fluorescent molecules are placed near intensified light, the molecules emit photons at a faster rate through an effect called Purcell enhancement. The researchers found they could achieve a significant speed improvement by placing fluorescent molecules in a gap between the nanocubes and a thin film of gold.

To attain the greatest effect, Mikkelsen’s team needed to tune the gap’s resonant frequency to match the color of light that the molecules respond to. With the help of co-author David R. Smith, the James B. Duke Professor and Chair of Electrical and Computer Engineering at Duke, they used computer simulations to determine the exact size of the gap needed between the nanocubes and gold film to optimize the setup.

That gap turned out to be just 20 atoms wide. But that wasn’t a problem for the researchers.

“We can select cubes with just the right size and make the gaps literally with nanometer precision,” said Gleb Akselrod, a postdoc in Mikkelsen’s lab and first author on the study. “When we have the cube size and gap perfectly calibrated to the molecule, that’s when we see the record 1,000-fold increase in fluorescence speed.”

Because the experiment used many randomly aligned molecules, the researchers believe they can do even better. They plan to design a system with individual fluorescent molecule placed precisely underneath a single nanocube. According to Akselrod, they can achieve even higher fluorescence rates by standing the molecules up on edge at the corners of the cube.

“If we can precisely place molecules like this, it could be used in many more applications than just fast LEDs,” said Akselrod. “We could also make fast sources of single photons that could be used for quantum cryptography. This technology would allow secure communication that could not be hacked — at least not without breaking the laws of physics.”