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industry  substrates


To date,we have shipped 100,000 wafers with a 6-inch diameter that have formed the foundation for the manufacture of 2 billion LED chips.And we are well positioned to increase these shipments , thanks to the construction of our new Batavia, IL, facility that focuses on crystal growth,and the new facilty in Malaysia that focuses on the polishing of large diameter wafers in high volume. The latter was recently qualified by a major customer for 6-inch sapphire wafers


Weighing in at 200 kg, Rubicon’s single-crystal sapphire boule is claim to be the largest in the world


to finished polished wafers in a controlled manner. One of our biggest accomplishments is the fabrication of the world’s largest single-crystal sapphire boules, which can be as large as 200 kg, with no variation of quality as the boule size increases. Our process expertise has enabled us to reach volume production of high-quality 6-inch diameter sapphire wafers and R&D volumes of 8-inch diameter sapphire wafers. According to the French market research firm Yole Developpément, the proportion of LEDs made on sapphire substrates that are 6-inch in diameter will increase from 5 percent this year to 16 percent in 2012 and more than 55 percent in 2015. Sampling of 8-inch wafers at the research and development stage has also commenced at several LED chipmakers.


Alternative substrates


The industry continues to explore alternative substrates for the growth of GaN LEDs, such as those made from


silicon, which are cheaper. Progress has been made, but devices grown on this platform still have a performance that lags that of GaN-on-sapphire LEDs.


One of the challenges that the R&D community has struggled with for more than a decade is the fundamental barriers imposed by the large mismatch in the thermal coefficient of expansion of GaN and silicon. In addition, there is intermixing between this pair of materials during MOCVD growth. This introduces a multitude of crystal defects, leading to physical cracking of the epitaxial layers. One consequence of this is a compromise in the long-term reliability of LED lamps.


In comparison, GaN-on-sapphire LEDs are proven in the industry, thanks to field-demonstrated, long operating service life (long-term reliability). During the last two decades, billions of these LED chips been successfully tested in multiple applications. This has led the industry to recognize sapphire as the only commercially viable, ‘field proven’ substrate for LEDs. At this time, more than 80 percent of LEDs are built on a sapphire foundation.


More and more of these LEDs are going into general illumination, but this technology will not dominate until the cost of ownership of this form of lighting is competitive with today’s incumbent, the compact fluorescent bulb. According to Dorsheimer, LEDs account for 40 percent of the bill of materials for LED light bulb. Chips costs will fall as LED makers move to larger diameters that aid operational efficiency and yield, and this will spur affordability of LED bulbs.


We believe that this growth in solid-state lighting is a tremendous opportunity for every sapphire manufacturer. Our recent completion of two state-of-the- art manufacturing facilities that deliver large diameter sapphire wafers in high volume to customers puts us in a great position to dominate the sapphire market.


To date, we have shipped 100,000 wafers with a 6-inch diameter that have formed the foundation for the manufacturer of 2 billion LED chips. And we are well positioned to increase these shipments, thanks to the construction of our new Batavia, IL, facility that focuses on crystal growth, and the new facility in Malaysia that focuses on polishing large diameter wafers in high volume.


This latter facility was recently qualified by a major customer for 6-inch sapphire wafers, the diameter that will be used to drive significant penetration of LED bulbs in the lighting market.


© 2011 Angel Business Communications. Permission required.


42 www.compoundsemiconductor.net October 2011


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