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news on the broad LED industry, outside of general lighting, along with the
materials and technology supply chain, visit LIGHTimes
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which covers packaged "lighting quality" LEDs through subsystems,
luminaires and application stories.
QD Vision Announces Achievement of 18 Percent External Quantum Efficiency
LIGHTimes News Staff
May 16, 2013...QD Vision of Lexington, Massachusetts, a developer of quantum dot based LEDs,
reports having achieved 19 cd/A efficiency and 18 percent external quantum
efficiency. QD Vision’s latest QLED performance results are currently
published in the 21
April 2013 issue of Nature Photonics. In the article, QD Vision reports
achieving 18% External Quantum Efficiency (EQE) with a color saturated red
quantum dot-based LED.
The company claims that this puts QLEDs near the fundamental efficiency
limit of the technology which the company says is 20 percent for quantum
dots.These results are two times higher efficiency than previously reported
state-of-the-art efficiency of a QLED device. QD Vision says its current and
luminous power efficiency are better than the best evaporated OLED result of
the same color coordinate, and significantly better than what
solution-processed OLEDs have thus far achieved.
In comparison, Pacific Northwest National Laboratory (PNNL) recently
reported 11 percent external quantum efficiency for a blue organic light
emitting diode (OLED) at 800 cd/m2. However Phosphor-based OLEDs are apparently
not included in the company's comparison statement.
“This paper clearly demonstrates the fundamental efficiency
advantage that QLEDs have over any other emissive display technology. Achieving
this milestone is a great breakthrough and the result of years of hard work and
dedication to achieving what others may have thought impossible,”
said QD Vision co-founder Seth Coe-Sullivan.
While at an earlier stage of development and commercialization than QD
Vision’s Color IQTM products, QD Vision says that its QLED performance is
already suitable for use in certain products that require precision color
solutions in an ultra-slim form factor, including monochrome visible and
infrared displays, and lighting devices for machine and night vision
Researchers Use Strain Engineering to Improve Green LED Light Output
LIGHTimes News Staff
May 8, 2013...Researchers from the Chinese Academy of Sciences’ Institute of
Semiconductors, Beijing, and University of Hong Kong have used strain
engineering to improve the light output of Green LEDs. The researchers improved
the light output of a 530nm green LED operating at 150 mA by 28.9 percent [Hongjian Li et al, Appl. Phys.
Express, vol6, p052102, 2013].
The researchers note that green-emitting nitride semiconductor LED
structures tend to suffer from low light output due to the difficulty in
producing the high-indium-content indium gallium nitride (InGaN) needed for
longer-wavelength light emission. In addition to the material quality
challenge, strain induced by the lattice mismatch with pure GaN leads to large
piezoelectric effects, giving electric fields that tend to pull electrons and
holes apart, reducing rates of recombination into photons (i.e. the
quantum-confined Stark effect, or QCSE), thus reducing quantum efficiency.
The Chinese team inserted a layer of lower-indium-content InGaN before the
high-In-content light-emitting layer. Simulations suggested that such a layer
could reduce the strain-dependent electric fields in the active light-emitting
multiple quantum well (MQW) structure.
MOCVD on C-plane sapphire was used to produce epitaxial material with a
low-In-content InGaN shallow quantum well (SQW) step. A 325nm helium-cadmium
laser was used to excite the photoluminescence spectra of the materials at low
temperature (85K) and room temperature (298K). One effect of the SQW was to
reduce the width of the spectral peak full-width at half maximum (FWHM) at 85K
from 16.7nm for the conventional LED material to 13.1nm for the SQW material.
The 298K measurement reduced the conventional FWHM of 20.1nm to 15.7nm. The
peak intensity was also higher with the SQW structure, therefore the SQW
material had improved crystal quality.
The peak height for the SQW material at 298K was 55.1% that at 85K. The
corresponding ratio for the conventional structure was 24.1%. The higher ratio
for the SQW material indicates a higher rate of radiative recombination and
higher internal quantum efficiency (IQE).
The electroluminescence was measured in an integrating sphere, giving light
output power–current–voltage (L–I–V) results. The
voltage performance is similar in the SQW and conventional devices. However,
the light output at 150mA is 28.9% greater in the SQW LED (49.3mW) over the
conventional device (38.4mW).
The researchers point out that improved overlap of the electron and hole
wavefunctions in the device leads to improved recombination into photons. The
external quantum efficiency (EQE) increased from 10.2–13.3% over the
conventional LED performance.
CrystAl-N Launches 2-Inch Bulk AlN
CompoundSemi News Staff
May 6, 2013...CrystAl-N, a German maker of AlN crystals is shifting its production from
1-inch to 2-inch AlN and accepting pre-orders of the new material. CrystAl-N is accepting pre-orders now. The company was founded in 2010 as a spin-off of Friedrich-Alexander-University Erlangen-Nuremberg. The company
says that its AlN substrates will boost the efficiency of deep UV LEDs, lasers
and high-power, high-frequency devices as soon as its cost-performance ratio is competitive. Furthermore CrystAl-N says that shifting production to larger
substrates will help to improve cost performance ratio.
Company CTO Boris Epelbaum commented, "Further diameter increase in our
patented tungsten based furnaces is not limited as we are using SiC as initial
Wafer polishing drastically improved as well for the AlN substrates.
"The corresponding wafers feature surface roughness of less than 0.3 nm and
are highly UV transparent," said Octavian Filip, director of wafering.
Hitachi Cable Develops Technology for Mass Production of GaN Templates
CompoundSemi News Staff
April 29, 2013...Hitachi Cable has developed a new mass-production technology for
GaN-templates. The process grows high-quality GaN single-crystal thin film on a
sapphire substrate. The company plans to start selling these templates. The
company says that using the templates as a base substrate for an epitaxial
wafer for white LEDs allows drastic improvement in productivity of white LED
epiwafers and the LED properties
MOPVE can reportedly grow a white LED epiwafer consisting of a thin active
layer and a p-type GaN layer with a total thickness of about 1μm over an
n-type GaN layer with a thickness of about 10μm, grown on a sapphire
substrate. However, it takes a long time to grow a high-quality and thick
n-type GaN layer. White LED epiwafers can be grown only about once or twice a
day at the most.
Hitachi Cable GaN-template reportedly can solve this problem because the
n-type GaN layer is already grown on the template. Hitachi Cable says that this
can reduce the time required for growth by about half compared with
conventional methods. The GaN-templates are also said to be suitable for
high-output LEDs which require large currents because they allow both low
resistance and high crystal formation,
The firm has developed single-crystal free-standing GaN substrates used for
blue-violet lasers and developed HVPE-growth technology and machines for
mass-production of GaN substrates. Template sized 2”, 4” and
6” are available with 8” templates in development.
Epistar Signs LED Collaboration and IP Licensing Agreement With Intermolecular
LIGHTimes News Staff
April 23, 2013...Epistar, Corp. and Intermolecular, Inc. of San Jose, California USA, have
signed a collaborative development program (CDP) and royalty-bearing IP
licensing agreement to increase the efficiency and reduce cost of Epistar's LED
devices. Under this agreement, Epistar and Intermolecular engineers will
together leverage Intermolecular's High Productivity Combinatorial (HPC™)
technology platform for development and manufacturing qualification of novel
materials and processes for advanced LED products.
Intermolecular notes that in the highly competitive LED market, new
technologies created by R&D are needed to both improve light output and to
reduce costs. Intermolecular contends that using the HPC Platform, will help
Epistar accelerate the pace of R&D ten times or more compared to what can
be achieved in a conventional LED lab.
"After a rigorous review of Intermolecular's capabilities through an
initial collaboration engagement, we have seen how their combinatorial approach
to materials innovation and device integration can augment Epistar's leadership
in LED technology," said M. J. Jou, president of Epistar.
"Collaboration with our industry partners has been critical to our
world-leading R&D and manufacturing strategy. We are confident that
leveraging Intermolecular's team and technology platform will further increase
our competitive advantage."
Sandeep Nijhawan, senior vice president and general manager of
Intermolecular's clean energy group commented, "Entering into a strategic
engagement with a top-tier LED company like Epistar validates the applicability
and disruptive potential of the HPC technology platform for LEDs, a market that
continues to have tremendous room for growth and technology
Plessey Releases First GaN on Silicon LED Samples
LIGHTimes News Staff
April 9, 2013...Plessey announced that samples of its gallium nitride (GaN) on silicon LED products (p/n PLW111010) are now available. According to Plessey, these entry level products are the first LEDs manufactured on 6-inch GaN on silicon substrates to be commercially
available anywhere in the world.
Plessey reportedly uses its proprietary large diameter GaN on silicon process technology to manufacture the LEDs on its 6-inch MAGICTM (Manufactured on GaN I/C) line at its Plymouth, England facility. Plessey contends that the use of it MAGIC GaN line using standard
semiconductor manufacturing processing provides yield entitlements of greater than 95% and fast
processing times providing a significant cost advantage over sapphire and silicon carbide based
solutions for LEDs of similar quality.
The release of the availability of Plessey’s GaN on silicon LEDs coincided with a visit to the
Plessey Plymouth facility by the Rt. Hon. Dr. Vince Cable, MP, Secretary of State for Business
Innovation and Skills and President of the Board of Trade. Business Secretary Vince Cable
commented, “The government is supporting innovative companies like Plessey who are growing,
creating jobs and exporting their products all over the world. That’s why we selected Plessey’s
£3.25 million Regional Growth Fund bid for Government support, which will create 100 new, high
tech and highly skilled jobs in the region.”
“Today is a significant step for us," said Barry Dennington, Plessey’s COO. “From acquiring our
first MOCVD reactor in August 2012 to having our first product in April 2013 is excellent progress.
These entry level products will be used in indicating and accent lighting applications. We will
continue to make progress in output efficiency and are on plan to release further improvements in
light output throughout this year and into next. The operating and unit costs are on plan and we
are seeing a number of routes to enhance our cost advantage over competing technologies.”
Engineering samples can be requested at the company's website: www.plesseysemi.com.
Johnson Matthey Exits Gas Purification Market
CompoundSemi News Staff
April 4, 2013...Johnson Matthey reports that it is leaving the bulk gas purification market. The company, which makes many gas puification products suited to LED and compound semiconductor manufacturing, cited the slowdown in the LED fabrication market as the reason for its market exit. The company says specifically that it is getting out the business of selling systems for gas purification for bulk gases using palladium membrane, heated getter or regenerable catalytic purifying technology. The company plans to close its manufacturing facility in West Chester, Pennsylvania. As a consequence, the company will begin to wind down operations at its Gas Purification Technology (GPT) business with immediate effect. Johnson Matthey says it continues to stand behind its warranty obligations for previously purchased products.
Cambridge University Opens £1 Million New Facility for Research Into GaN-on-Si LEDs.
LIGHTimes News Staff
April 3, 2013...Cambridge University has opened a new facility dedicated to researching
gallium nitride-on-silicon LEDs. The facility, which is funded by the
Engineering and Physical Sciences Research Council (EPSRC), was opened March 28
by David Willetts MP, the Minister for Universities and Science. It is the
latest development in the University’s decade-long research project to
make lower cost LEDs for lighting.
Researchers lead by Professor Sir Colin Humphreys in the University’s
Department of Materials Science and Metallurgy after about ten years of work,
developed a method of growing low cost GaN LEDs on silicon substrates in 2012.
This technology was then picked up by UK company, Plessy.
The researchers expect that the new gallium nitride growth reactor will help
them further improve a method of growing low-cost LEDs on silicon substrates,
reducing their cost by more than 50% and opening them up for more general use.
University scientists are also starting to investigate the potential of gallium
nitride in high power electronics.
“At the moment, a 48-watt LED lightbulb, made from GaN on sapphire
LEDs, costs about £15,” Humphreys said. “That’s a
cost that you make back several times, because the bulbs last for so long, but
it is too much to convince most customers to buy them. The research we have
already performed on GaN on silicon LEDs, plus that which we will carry out in
this new reactor, will mean that soon people will be able to buy an LED bulb
for just £3 instead.”
Minister for Universities and Science David Willetts said, "LEDs are
highly energy efficient but expensive to produce, meaning their domestic use is
limited. This excellent new facility will enable researchers to look at more
cost-efficient ways to produce LEDs, saving money and benefitting the
environment. It will also help keep the UK research base at the very forefront
of advanced materials, which is one of the eight great technologies."
Humphreys and his team are also currently investigating the so-called
“green gap” problem in which the efficiency of red, blue and green
LEDs together in one method of producing white light is limited by the
efficiency of the green LEDs.
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