LONDON – Bridgelux Inc., a developer of semiconductor technology for solid-state lighting, has said it has demonstrated a light output of 135 lumens per watt from a GaN-on-Si LED. The company claimed that this is the first achievement of "commercial grade" performance from a silicon substrate LED, but said it may take two to three years for products based on the technology to come to market.
Bridgelux (Livermore, Calif.) was founded in 2002 and has raised about $110 million in venture capital since then.
Most epitaxial wafers for LED use sapphire or silicon carbide substrates as the starting material. But large diameter sapphire and silicon carbide substrates are costly, difficult to process, and not widely available.
The alternative is to grow gallium nitride on low-cost silicon wafers that come in 150-, 200- and 300-mm diameters. This can deliver a 75 percent improvement in cost, Bridgelux claimed.
The 135 lumen per watt performance was achieved using a single 1.5-mm diameter LED operated at 350-mA with a color correlated temperature (CCT) of 4730K. The LEDs require 2.9-V at 350-mA and less than 3.25-V at 1-A.
Bridgelux foresees optimization of the epitaxy process on 200-mm diameter silicon wafers and anticipates the delivery of its first commercially available GaN-on-Silicon products over the course of the next two to three years.
"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," said Bill Watkins, Bridgelux CEO, in a statement. "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."
" It's not so much brightness as efficiency, or more accurately, efficacy. A 60W tungsten bulb has an efficacy of about 13 lm/W, a halogen has about 25 lm/w and a spiral fluorescent comes in at around 115 lm/W. Brightness will depend onthe number of watts you put in! So, at 1A this LED uses 3.25W and puts out about the same amount of light as a 35W bulb."
so this "135 lumen per watt" is good right, it will provide slightly more light hours on a AA x2 battery pack torch or garden PV light for instance, and drain your mobile device slower as they seem to keep the pointless LED's on all the time for no good reason :P