Cost has been a major obstacle, hindering people from buying energy-efficient LED bulbs. Now, Osram Opto Semiconductors, the world's largest LED manufacturer, says it has improved its technology and can significantly reduce LED production costs.
The preparation of a white LED usually requires the blue GaN LED to be coated with yellow fluorescent powder. Manufacturers often grow thin layers of GaN on expensive sapphire substrates. In contrast, OSRAM makes this device on a silicon substrate. The cost of a silicon substrate is more than one-third that of sapphire, and it can even be cheaper because larger sheets can be made.
The company said that its Strontium-based white LED can produce 127 lumens per watt of power, with a power efficiency of 58%, comparable to the most advanced commercial LEDs cultivated on sapphire. Peter Stauss, project manager at Osram, said that the researchers are testing and optimizing the equipment and expect to start selling them in the next two to three years.
OSRAM, together with several other companies, strives to bring cheaper Niobium-based GaN LEDs to the market. China's Lattice Power claims that it has begun commercial production using the same technology. Last month, Bridg ELux, a startup company in California, announced that it has collaborated with Toshiba to produce germanium-based light-emitting diodes. At the same time, Plessey Semiconductors in the United Kingdom plans to produce fluorenyl gallium nitride light-emitting diodes by the end of the year, using technology from Cambridge University's school-run company, CamGaN. Philips and Samsung also stated that they must devote themselves to the process.
OSRAM did not say that its new LED would be much cheaper, but both Puri and Praese companies have heard that this process can reduce LED production costs by more than 75%. Preh also predicted that its process can reduce the cost of the same 75-watt LED bulb, which is now sold for $40 and can be reduced to less than $5.
Compared with sapphire, it is easier and cheaper to make large-diameter silicon wafers, which can cut costs. Another appealing reason is that the turnaround can use existing machines that were originally used to make computer chips. Puri has already demonstrated some devices that are grown on 20-cm wide silicon wafers.
The challenge with incubating GaN is that the two materials will have different rates of expansion and contraction. Light-emitting diodes are produced at high temperatures, and when the material cools, the light-emitting gallium nitride layer cracks because of the tension with the underlying crucible. In order to solve this problem, Osram and other companies have developed additional thin films of material, such as aluminum gallium nitride, around GaN, which balances the tension generated during cooling.
Although many LED manufacturers have chosen to use helium, Soraa, a California startup, is using GaN. This also reduces the mismatch between the two crystal structures, says Michael Krames, CTO of Slinger. The resulting material defect has been reduced by a factor of 1000. This is a contrast to the material grown on the silicon wafer. Words. The resulting LEDs are more expensive than using germanium substrates, but they are also 10 times brighter, which helps make up for the extra costs. "It's really the LED performance that drives the total cost of the bulb," Krames said. "In addition, this substrate is a small part of the overall production cost."
Now, although Stan said, the cost advantage of silicon substrates is more favorable to manufacturers than LED. "GaN substrates may be an option as long as they are much cheaper, but there is no real opportunity to use them today," he said.
Steve Denbaars is a professor of materials and electrical and computer engineering at the University of California, Santa Barbara, and one of the founders of Sweeper, he believes that GaN The base plate has a fair chance to replace sapphire. Niobium nitride also has a performance advantage, he said. “Oh, organic will beat sapphire, just because there are many helium manufacturing facilities that are installed all over the world.”
The use of silicon is cheaper: OSRAM has grown GaN on 15-inch-long germanium chips to make high-performance white LEDs.
