The release of GAN-on-silicon LED chips in China presents a lower-cost alternative that is comparable in quality to mainstream products based on sapphire and SiC substrates.
R&D work leveraging the advantages of silicon substrates has yielded a solution for GAN LEDs, which addresses the material stress in this configuration. Lattice Power Corp. adopts a special epitaxial structure and substrate design, and growth techniques overcoming the combination of lattice and thermal expansion mismatch issue to achieve high performance and reliability. From this, the maker has realized volume production of GAN-on-silicon LED chips, surpassing efforts in the US and Europe for commercial-grade components on this scale.
Lattice opted for silicon because of its compatibility with the IC manufacturing platform, which results in a more scalable and cost-effective solution. Compared with its much smaller sapphire and SiC counterparts, substrates based on the material can be processed through silicon lines.
The supplier launched four large kinds at the beginning of its mass manufacture in June 2012. The products target indoor, outdoor and portable lighting applications. These consist of 28x28, 35x35, 45x45 and 55x55mil LED chips with power ranging from 0.5 to 2W. In cool white, the 45mil model operating at 350mA has luminous flux and efficacy of 130 lumens and 120 lm/W.
This commercialization represents Lattice's second milestone, of which the first involved the volume production of smaller models used in displays and signage.
Lattice, in fact, plans to switch production from 2in silicon-based LED chips to 6in versions in the months ahead. The company is taking advantage of the material's availability in larger diameters, which are at a fraction of the cost of sapphire kinds. This will lead to substantial reductions in outlay for downstream makers. Future cuts in LED chip expenditure can be as much as 70 percent especially when produced on bigger substrates.
With the breakthrough, Lattice has broken the monopoly of key players Nichia and Cree respectively in sapphire and SiC technologies. At present, about 90 percent of LEDs are fabricated on sapphire substrates and the rest on SiC.
