Bridgelux Demonstrates 135 lm/W GaN-on-Silicon LED

Bridgelux Inc. of Livermore, California USA, announced today its first major
lab-based development, a demonstration of 135 Lumens per Watt GaN-on-silicon-based
LED Technology. GaN-on-silicon LEDs, widely seen as the holy grail of LED production
efficiency, have been an elusive goal for the many companies that have pursued
them. Bridgelux says that its demonstration represents the industry’s first
commercial grade performance for a silicon substrate-based LED. The LED had
a 350mA operating current and it required just 2.9 volts and under 3.25 volts
at 1 amp. The 4730K CCT LED measures 1.5mm by 1.5mm.

The LED was produced on a standard 8-inch silicon wafer. Bridgelux contends
that growing GaN on larger, low-cost silicon wafers that are compatible with
modern semiconductor manufacturing can deliver a 75% improvement in cost over
current approaches, which commonly use 2- to 4-inch sapphire wafers. Bridgelux
points out that when scaling up production, large diameter sapphire and silicon
carbide substrates are costly, difficult to process, and sometimes not widely
available. This has kept production costs high, inhibiting widespread adoption
of LED lighting in homes and commercial buildings.

Additionally, the Bridgelux devices are demonstrating a low forward voltage
and superior thermal resistance which make them ideally suited for high-performance,
illumination-grade applications. Optimization of the epitaxy process on 8-inch
Si wafers will make LED manufacturing more compatible with existing automated
semiconductor lines. Bridgelux notes however that “A number of the processes
[used to produce conventional LEDs] … would need to be modified to eliminate
some materials that are currently used, and which are incompatible with silicon
substrate manufacturing.”

Bridgelux sees the move to silicon substrates as a revolutionary step for the
LED industry. Over the past 5 years, Bridgelux CTO Dr. Steve Lester has shepherded
a quietly-dedicated GaN-on-Silicon R&D team. Concurrently, industry-wide research
and development of GaN growth on silicon has increased, both for production
electronic devices and in the labs for optical technology. Bridgelux says that
its GaN on silicon performance levels today are comparable to state-of-the-art
sapphire-based LEDs available 12-24 months ago. Over the course of the next
two to three years, the company anticipates the delivery of its first commercially
viable GaN-on-Silicon products that meet performance requirements of LED lighting.
“Bridgelux’s achievement is a significant reflection of the strength of
our leadership in Silicon materials and epitaxial process technology,”
Bill Watkins, Bridgelux CEO. “The significantly reduced cost-structures enabled
by Silicon-based LED technology will continue to deliver dramatic reductions
in the up-front capital investment required for solid state lighting. In as
little as two to three years, even the most price-sensitive markets, such as
commercial and office lighting, residential applications, and retrofit lamps
will seamlessly and rapidly convert to solid state lighting.”

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