Bridgelux demonstrates silicon substrate LED that produces 135 lumens per watt

March 9, 2011 by Katie Gatto weblog

( -- Silicon substrate LED's are cool, but you won't find them in your TV, or in the headlights of your car. They simply do not throw off enough light to be used in commercial applications. Or, at least they did not used to be able to.

Bridgelux Inc., a California-based developer of semiconductor technology and solid-state lighting, has demonstrated a silicon LED with a output of 135 lumens per watt. The company believes that this is the first time that anyone has created "commercial grade" performance from a LED.

The performance of 135 lumen per watt came to fruition by using a single 1.5-mm diameter LED that is operated at 350-mA. The LED's have a color correlated temperature (CCT) of 4730K. In order to function the LEDs require a 2.9-V at 350-mA and less than 3.25-V at 1-A.

Instead of using the more commonly found sapphire or silicon carbide substrates to create the epitaxial wafers that are used to create the LED, Bridgelux decided to use the less expensive to produce, by growing, gallium nitride on low-cost . These grown wafers come in 150-, 200- and 300-mm diameters that can, according to Bridgelux, deliver a 75 percent improvement in cost.

Products based on this technology are at least two to three years to come to market. Some of the potential applications for this technology include commercial and office lighting, residential lighting applications, and retrofit lamps that the company hopes will convert to the solid state lighting. No word as to any specifics as to when you can expect to buy a GaN-on-Silicon based LED lamp.

Explore further: IMEC, AIXTRON set important step towards low-cost GaN power devices

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1.7 / 5 (6) Mar 09, 2011
This is great but i though LED lights contained lead. They're too dangerous!

3.7 / 5 (7) Mar 09, 2011
Not as dangerous as CFLs.
not rated yet Mar 09, 2011
This is great but i though LED lights contained lead. They're too dangerous!


Not as dangerous as CFLs.

ahhh you beat me to the punch line.
1 / 5 (1) Mar 09, 2011
Yah well Congress is beating all of us. Right. Down.
5 / 5 (4) Mar 09, 2011
LEDs are encapsulated, which removes any risk. Otherwise the gallium arsenide (as in arsenic) used in most modern LEDs would be in our ground water by now.

A little ignorance goes a long ways.
5 / 5 (6) Mar 09, 2011
We are being trained to ask fearful stupid questions about everything, but with no intent to learn the answer or the context.
Mar 09, 2011
This comment has been removed by a moderator.
3.7 / 5 (3) Mar 09, 2011
The article you referenced should never have been published by physorg. It is sensationalist rubbish. LED's are made of silicon carbide, aluminium and gallium with trace amounts of arsenic, indium and phosphorus as dopants, but no lead (Pb). The pins are made of copper with tin plating, and the whole thing is encapsulated in polyester or epoxy resin. Electronic manufacturers have been working for over a decade to remove Pb from electronic components in order to comply with RoHS (Restriction of Hazardous Substances)legislation in the European Union. Today, most electronic components are RoHS compliant and therefore contain less han 1000ppm of Pb.
not rated yet Mar 09, 2011
135 lumens, how does this compare to the brightness of a 60 watt incandescent bulb?
not rated yet Mar 09, 2011
Sorry everybody, i was being sarcastic.
not rated yet Mar 09, 2011
Yeah, just realised that.

@robbor, 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.
1 / 5 (1) Mar 10, 2011
Minor niggle: Put 1A through a LED and it'll burn out. That's why the LED lights you can buy for home use are always clusters of LEDs
5 / 5 (1) Mar 10, 2011
Of course, no mention of the CRI or anything related to the quality of light it produces.

Which is the major problem of LEDs. Non-continuous spectrum that is even worse than CFL's.
5 / 5 (2) Mar 10, 2011
Depends on where you use it. E.g. headlights for cars don't need a continuous spectrum. Mixing various types of LEDs can give you a (near) continuous spectrum fof applications in your home.
5 / 5 (2) Mar 10, 2011

1W LEDs are commonly rated at 700mA. 5W LEDs are rated at even more. There are certainly LEDs that will easily handle 1A continuous. Check out Luxeons or Cree Xlamps
not rated yet Mar 10, 2011
Depends on where you use it. E.g. headlights for cars don't need a continuous spectrum. Mixing various types of LEDs can give you a (near) continuous spectrum fof applications in your home.

Problem is, will the luminous efficacy remain at 135 lm/W when you introduce more colors?

There's a certain relation between lumious efficacy and color quality. If you have 1 Watt of light, and you have to make the most lumens out of it, you have to center the output at around 490 and 570 nanometers, or monochromatic blue and yellow light. Yellow light is picked up by both red and green sensitive cells in the eye, so you get red green and blue sensations which makes the light look white, but the CRI will be absolutely horrible. Anything viewed under that light will look strange.

So, there's two ways of getting more lumens out of a LED. Either you make it more efficient, or you make the quality of light worse. Guess which one is easier to do?
not rated yet Mar 10, 2011
There's several options of changing the frequency spectrum (varying from the costly to the inefficient). Any such transformation will detract from the 135 lm/W figure. However any other light source has the same problems (except old-school filament bulbs, but their efficiency is so low that they are still MUCH worse)

Upping the lm/W just tells you that even after employing any of these filter/frequency shifts you'll still have more lm/W as before. Certainly more than 13m/W
not rated yet Mar 10, 2011
The figure of 135 lumens per watt is meaningless without comparison and I am too lazy to look it up, it should have been in the article's next sentence. The article is near worthless without this info and/or research. Another poorly written article.
not rated yet Mar 10, 2011
An incandescent 100w bulb produces 1750 lumens, or 17.5 lumens per watt. It would take 13 watts' worth of this 135-lumens-per-watt device to duplicate a standard 100w incandescent. That's about 8 times more efficient. That's about equal to other LEDs. What we need is a nice cheap price. LEDs are terribly expensive compared to incandescent.
not rated yet Mar 14, 2011
I use halogen bulbs. They're about twice as efficient as regular bulbs, last twice as long, and produce a continuous spectrum of light by nature.

If you want to check out the spectrum of light your lamps produce, take a pressed DVD, split it in half and carefully peel the silver layer off. The track pattern embedded in the clear plastic works as a diffraction grating that allows you to split the spectrum of light into bands. With a digital camera and a roll of toilet paper, you can then build a spectrograph.

For example, the so called daylight CFLs give you a spectrum that is exactly the same as regular soft whites, but they have a second bright blue spike. It's nowhere near daylight, it's simply more blue.
not rated yet May 07, 2011
White LEDs do not use RGB components, they use a blue, violet or UV LED to excite a mix of phosphors. White LEDs' color accuracy is similar to fluorescents, with a strong peak in the blue and varying quality in the rest of the spectrum depending on the quality of the phosphors used.

Specifying a color temperature for phosphor lighting is misleading since not it does not emit a thermal spectrum. CRI is a more important measure of the quality of the light, with anything much less than 95 being noticeably inferior to incandescent lights.
not rated yet May 09, 2011
Can anyone say what the theoretical limit of "Visible Lumens per Watt" is irrespecitive of technology, assuming colour were not important. e.g. what's the pure energy content of 100 Lumens of light?
not rated yet May 09, 2011
Ok found it.


As I thought I knew, wasn't quite sure. See from chart 2/3rd way down, no LED's have ever gotten close the the "wall plug efficiency" of common flourecents or sodium lamps.

8.7 W LED screw base lamp (120 V) - 10.1 to 13.6%
Compact Flourescent - 15 to 18%
High pressure sodium lamp - 12 to 22%
Low pressure sodium lamp - 15 to 29%

Agreed, Sodium lamps' colour (orange) is a problem indors, but even flourescents are presently far more efficient than any LED's presently available.

Present references to dispute.

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