A new manufacturing technology is expected to greatly reduce the cost
of light-emitting diodes (LEDs) in the future. For the first time ever,
researchers at the Siemens subsidiary Osram Opto Semiconductors were
able to successfully produce gallium nitride LED chips on a silicon
substrate instead of the much more expensive sapphire backing. Silicon
is a standard material in the semiconductor industry and is therefore
an inexpensive and easily obtainable alternative. This development goes
a long way toward 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, above all, energy-conserving alternative to
traditional types of room lighting. However, until now the
manufacturing costs for LEDs have been higher than those of other more
established types of lighting, so they have not been widely adopted for
Using this new procedure, it should be possible to use large sheets of
silicon for LED production, which would result in a major improvement
of manufacturing efficiency. Osram has already succeeded in producing
high-performance LED chips on a 150-millimeter (six-inch) wafer.
Theoretically, one such wafer would be sufficient to produce 17,000 LED
chips of one square millimeter each.
Researchers are already working on the adjustment of the production
process to handle eight-inch wafers. This would increase the number of
chips per substrate, thereby further 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 one square millimeter in a standard housing delivers a record
brightness of 634 milliwatts at 3.15 volts. That's an efficiency rate
of 58 percent. Those are excellent results for a chip of that size at a
current of 350 milliamperes.
The development of these new manufacturing technologies is based on the
specialized knowledge regarding the growth of artificial crystals that
has been gathered by the researchers at Osram Opto Semiconductors. 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. At the same time, these
silicon films are also comparable to sapphire backing with regard to
the LEDs' brightness and stability.
More information at http://www.siemens.de/pof