Anew manufacturing technology is expected to greatly reduce the cost of light-emitting diodes (LEDs) in the future.
This technology was featured in Innovation News, which is published by Siemens and is concerned mainly with the results of basic and applied research into new products and innovative materials.
For the first time ever, researchers at Osram Opto Semiconductors – a Siemens subsidiary – have successfully produced gallium nitride LED chips on a silicon substrate instead of the much more expensive sapphire backing.
Silicon is a standard material in the semiconductors industry and is, therefore, an inexpensive and easily obtainable alternative.
This development goes a long way to making it possible for Osram to produce LED components at a much lower cost, while maintaining the same level of quality and performance.
LEDs are an efficient and energy- conserving alternative to traditional types of room lighting. However, until now, the manufacturing costs of LEDs have been higher than those of other more established types of lighting, so they have not been widely adopted for everyday use.
Using the new procedure, it should be possible to use large sheets of silicon for LED production, which should result in a major improvement in manufacturing efficiency.
Osram has already succeeded in producing high-performance LED chips on a 150 mm wafer. Theoretically, one such wafer would be sufficient to produce 17 000 LED chips of 1 mm2 each. Researchers at Osram are already working on the adjustment of the production process to handle eight-inch wafers. This should increase the number of chips per substrate, thereby reducing the cost of production.
The first commercially available LED products using silicon-based chips are expected to be on the market in about two years.
These new thin-film-based LEDs are still only at the pilot stage and will have to be tested under real-world conditions.
The blue and white silicon-based prototypes display performance characteristics that are on a par with the LEDs available on the market today. A blue chip measuring 1 mm2 in a standard housing delivers a record brigthness of 634 mW at 3.15 V – an efficiency rate of 58%. Those are excellent results for a chip of that size at a current of 350 mA.
The development of these new manufacturing technologies is based on specialised knowledge gathered by the researchers at Osram Opto Semiconductors regarding the growth of artificial crystals.
The major breakthrough was a special epitaxy process, which made it possible to slice off particularly stable silicon films without the cracking that has often been a problem in the past.