Light Emitting Silicon Steps It Up

h4mm3r writes "STMicroelectronics plans to announce a breakthrough on Monday in light-emitting silicon that could lead to a new generation of more powerful computing processors and more efficient automobile components as well as potentially higher-speed optical data-transmission systems. (gotta register, free yadda yadda)"

Saab

[AssFace]

Saab's newest 9-3 sport sedan has all of its electronics talking to each other over a fibre optic line - supposedly allowing more crap to be added later with greater bandwidth for cooler new features and stuff.
I don't really see how it will have an effect on me, but I think it is a cool idea in general.

Saab is owned by GM, soi I don't know if it is a trend that all of GM is heading towards, or if Saab is somehow special.

Google partner link

[pacc]

Light-Emitting Silicon Shines Much Brighter in New Invention [nytimes.com]
Why can't slashdot become a partner to NYT?

If you don't want to give google false page hits there's always majcher [majcher.com]

Integration

[Drakula]

Being able to integrate light emitting semiconductor devices together with electronic circuits is one of the holy grails of the semiconductor industry. Not only would the benefit come to increasing the speed of processors, optoelectronic devices would benefit greatly from this technology through integration. The cost savings and increased functionality would be incredible. Can't wait for it to become a reality.

Very challenging to do

[Cutie Pi]

One of the things this article really doesn't elaborate on is just how difficult the road has been to make efficient light emitting silicon. I had a professor as an undergraduate at the University of Rochester who spent a significant amount of time trying to get it to work. The article doesn't go into the technology, but I'm guessing they're using porous silicon. Porous-Si has small nanometer scale pores in (etched via electochemistry). The pores effectively alter the band gap of the silicon, increasing it to that of the compound light-emitting semiconductors such as GaAs. While this technique works well at generating light, the problem is getting it to generate light efficiently. Hence the exotic rare-earth materials such as erbium. I'm impressed that STMicroelectronics was able to increase the light output 100-fold. Extravagent claims such as these make me want to take a wait-and-see attitude. The process might be so difficult that it wont be practicle on high-performance chips for some time. Also, the processing techniques of light emitting silicon is different than for standard logic. I'd like to see how well these two processes can be merged.

Re:Then I was like.... HUH???

[Anonymous Coward]

Here's something else (only slightly different):
http://siliconstrategies.com/story/OE G20021028S001 4

Basically, LEDs use Gallium and some other material because Silicon is horribly inefficient at photo-applications (its a electron band-gap thing, ask a physicist), but because its so cheap and GaAs is very not cheap, they still use polycrystalline Si for large solar cells.
Unfortunately, Leds are just too dim when silicon is used, so Gallium and whatever else (depends on wavelength) is still necessary there. By getting efficient light emitting Silicon, a whole pantload of money gets saved by avoiding Gallium.

End note: Why is Si cheaper than Ga? Refinement is more complex for Ga, Si is much more plentiful, and it hard to make large wafers of GaAs. Plus GaAs oxide (don't know the formula) is liquid at room temperature, so the only demand is photo applications (and stressed Si) because making IC with just GaAs means you can't use a liquid GaAs-oxide as a mask/gate/whatever.

GOOGLE News (Beta) Link

[e.m.rainey]

For those of you who don't like to register...

Google News (Beta) Link [nytimes.com]

Re:Then I was like.... HUH???

[bpowell423]

The AC that replied to you pointed out the possible benefits for solar cells, but...

The reason the Sun designer described it as "the holy grail" is timing circuitry on CPU's. What's the figure, something like 75-80% of a CPU is dedicated to timing circuitry? Think about what happens when you replace all that timing circuitry with a light pulse, and just pick it up wherever you need it. Eliminate all the wiring currently used to distribute the timing, and you get lower power, tons more silicon to devote to other things, and probably the potential for speed gains.

Re:Then I was like.... HUH???

[gus2000]

Wow, sorry but I need to correct you on a bunch of points.

Gallium Arsenide (not gallium) is used to make a variety of LED and semiconductor lasers. Silicon is unattractive for light-emitting applications because it has an indirect bandgap, making emission of photons much less efficient than in direct bandgap materials.

Making large wafer of GaAs is not so much a processing issue as a cost issue (i.e. how much would one wafer end up having to sell for, and would anyone at all even think of dropping that much money on one). HOWEVER, neither GaAs nor its native oxide(s) are liquid or even water-soluble at room temperature. You were perhaps thinking of Germanium. The problem with GaAs oxides is that they do not form into such nice layers as SiO2, and that they do not effectively passivate the GaAs surface such that MOSFETs cannot be fabricated. GaAs (and InP) and still widely used (in your cellphone for example), but in different ways than silicon and not nearly as widely as silicon.

Story on EETimes also

[BinaryForces]

Skip the NYTimes reg crap and read it here: STMicro claims light-emitting silicon breakthrough [eet.com]

Augmentation

[EEgopher]

On the receiving end, GaAs is sensitive (A/W) to a much wider range of wavelengths than Si. Silicon is sensitive perhaps up to 1100nm whereas GaAs is sensitive in the 1500nm range. The fiber optic media exhibit minimal loss in the 1500nm range, so GaAs is the appropriate choice for receiving signals.
I'm working on a GaAs project now, if you want to keep me company -- WRITE!

Nitpicking...

[mmol_6453]

Solar Cells == Photovoltaic Cells
Solar Cells != Photo-Diodes

While both are PN junctions, insofar as the construction is concerned, photovoltaic cells actually produce a voltage, while photodiodes behave...differently.

When you have a photovoltaic cell, you need only connect a load to it to use EM energy for whatever work you need done.

With diodes, you have one PN junction (meaning P-type material on one side, and N-type material on the other.). To forward-bias the diode, you attach your positive voltage source to the P region, and your negative voltage source to the N region. This causes your electrons (called current carriers) to be pushed across the PN junction toward your positive voltage supply.

If you reverse-bias the diode, your current carriers will be drawn away from the PN junction, and almost no current, called leakage current, can cross.

All PN junctions are sensitive to light in that light striking silicon will produce current carriers(disclaimer: I'm only telling half the story...it can get confusion if you start considering "electron holes"...but if generation of free electrons bothers you, feel free.), wherever they strike. If they're particularly near the PN junction, they will serve to cause an increase in the leakage current, the external measurement of which is how the information is retrieved.

A rudimentary photodiode is simply a PN junction with a glass window.

There are all sorts of things you can do with semiconductors, doped or not. I keep seeing discussion proclaiming the downfall of semiconductors, but I wouldn't count on, say, quantum computing, to be able to function without supporting circuitry for the next twenty to thirty years. I hope to retire about then. :)