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news  review Soraa GaN-on-GaN LEDs break barriers


SORAA has announced the next generation of its high external quantum efficiency GaN-on-GaN LEDs.


The firm says its new LED outperforms the best-documented LED laboratory result by Nichia Chemical Co. at current densities of 100 A/cm2


and beyond as described in the


paper, “White light emitting diodes with super-high luminous efficacy,” J. Phys. D: Appl. Phys. 43, 354002).


Soraa has published a paper on its ground breaking LEDs, entitled, “Bulk GaN based violet light-emitting diodes with high efficiency at very high current density” in Applied Physics Letters, 101, 223509. In it, Soraa reports an external quantum efficiency of 68 percent at 180 A cm-2


.


“The record breaking performance from our next generation of GaN-on-GaN LEDs is a credit to the extremely talented


Solar Junction and Amonix unite to cut CPV costs


SILICON VALLEY-BASED solar energy company Solar Junction, has signed a co- development agreement with Amonix, a designer and manufacturer of utility-scale CPV solar power systems.


“This agreement solidifies a new partnership between two advanced technology leaders in CPV,” says Pat McCullough, Chief Executive Officer at Amonix. “It’s our goal, by combining our world record module technology with Solar Junction’s world record solar cell, that we can increase efficiencies while driving CPV costs down. The results of this collaboration, and its lower levelised cost of electricity (LCOE), will be revealed soon.”


In October 2012, Solar Junction surpassed its own world record, achieving 44 percent efficiency at a concentration of 942 suns. Amonix secured the world record for a CPV module in May of 2012, by converting over one-third (33.5 percent) of the energy of direct sunlight into electricity. This record is internationally recognised as the gold standard for solar power efficiency. Together, these benchmarks for high


research and development team at Soraa, and a testament to the vision of our founder and GaN-on-GaN pioneer, Dr. Shuji Nakamura,” says Mike Krames, CTO of Soraa. “But what’s amazing is that we have just scratched the surface in terms of performance gains from our GaN-on-GaN LED technology.”


Soraa says its GaN-on-GaN LEDs handle significantly more current and emit ten times more light per unit area of LED wafer material than LEDs created by depositing GaN layers on cheaper foreign substrates like sapphire, SiC or silicon.


However, the cost of GaN substrates is huge compared to its couterparts. For example, according to Lux Research, bulk GaN currently costs about $1,900 or more for a 2” substrate, compared with $25 to $50 for a far larger 6” silicon substrate. Lux predicts that HVPE (the cheaper


alternative to MOCVD) 2” GaN substrate costs will fall by more than 60 percent to $730 per substrate in 2020, while 4” HVPE substrate costs will fall by 40 percent to $1,340 per substrate.


Soraa’s GaN-on-GaN technology leverages the advantages of the native substrate, including over a thousand times lower crystal defect densities that allow reliable operation at very high current densities (the same principle that enabled Blu-ray laser diodes).


In addition to superior crystal quality, the native substrate’s optical transparency and high electrical and thermal conductivity enable a very robust, simple LED design that delivers maximum performance. Another advantage of the GaN-on-GaN approach is that it enables considerable flexibility in the choice of crystal growth plane.


Emcore wins $7.4 million contract from US Air Force


THE AIR FORCE division of the US Department of Defence has awarded Emcore a $7,364,902 cost-plus-fixed-fee contract for the “Advanced Multi-Junction Space Cell Producibility Programme”.


concentration photovoltaics confirm these companies have a roadmap to reach the forecasted 30 percent cost reduction compared to photovoltaic technologies. The National Renewable Energy Laboratory (NREL) verified both records.


Solar Junction’s new record continues to demonstrate the value of its A-SLAM materials, which uniquely provide CPV system manufacturers the foundation to deliver the most efficient conversion of solar to electrical energy. CPV panels work by concentrating sunlight onto small multi- junction cells, which Solar Junction manufactures at its North San Jose facility.


The aim of the project is to improve the manufacturing processing capabilities and qualify state of the art solar cells to at least 33 percent efficiency. In a production environment, the program is looking to qualify high efficiency, flexible or rigid, multi-junction space solar cells.


The programme is focussing on a number of critical requirements which are needed in warfight-specific satellites.


These include high performance, lightness, compactness and low cost. The cash will be used to develop Emcore’s III-V multi-junction solar cells. The basic structure of the firm’s highest efficiency solar cell (currently quoted as a minimum of 29.5%) is shown below.


The project is expected to be completed by April 13th, 2018


March 2013 www.compoundsemiconductor.net 7


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