Germanium Diodes Mean Progress Toward Silicon-Chip Lasers 66
David Orenstein writes "Teams at Stanford and MIT have each reported getting
strong light signals from germanium-based diodes on silicon at room temperature. Engineers have long sought to do this because, with further refinement into lasers, such diodes would allow for optical interconnects on chips. Optical interconnects could operate much faster and with less power than electrical (metal) ones that are becoming bottlenecks on current chips."
Ya my computer caught that flu going around. (Score:2, Insightful)
I smell a future of fiber optics and biologically based storage (aka - the brain). Clearly they have exhausted the current technology in terms of exponential breakthroughs.
Imagine a computer that was powered by liquid supplements rather than electricity.
It would be nice to know that my computer could actually feel my punches when it misbehaved.
Human implant possibilities! (Score:1)
Just don't switch it to overload!
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.... or sharks come and take your lasers away.
And it's organic (Score:5, Funny)
Wow, plant-based electronics! This will surely usher in a new age of biological computers that will be able to . . .
What? It's not a geranium diode?
Uh, how 'bout that new version of Firefox? Pretty snazzy, eh.
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Chill you coward, that was damn funny!
Re:It's made by the germans! (Score:2)
It's made by the germans! You know the Germans Make good stuff!
Oh wait, it was made at Stanford....
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Okay, this was good too! Keep em coming!
I thought they already existed (Score:2, Interesting)
I know for sure that I used Germanium diodes before and I'm pretty sure Germanium-based LED's have been developed before. Dunno what the news is.
Re:I thought they already existed (Score:4, Funny)
The news is that they've found a way to grow 'em on silicon, which lends itself well to chip production.
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That IS pretty big news.
Does anyone here have any inside details?
While SF has made great use of Tunneling Diodes, there are some genuinely freaky potential applications of this; the process outlined ITFA makes me think that they might be able to produce very strongly matching tunneling diodes....and that is just scary (in a mainly good way).
Re:I thought they already existed (Score:5, Informative)
I know for sure that I used Germanium diodes before and I'm pretty sure Germanium-based LED's have been developed before. Dunno what the news is.
They seem to have improved on Germanium LEDs by doping them differently to the point where the can look into using photons to transmit information around a silicon chip in place of electrons. I imagine they will look into building light pipes out of silicon, ie, little optical fibres.
OT: somebody should teach ascribe how to use the title tag.
Re:I thought they already existed (Score:4, Interesting)
That's cool, but with modern chip designs using electron tunneling for some of the effects, it can't be used chip-wide. On the other hand, light can cross through light, so you would be able to avoid tediously long tracks currently required.
There may be some additional interest in the aerospace industry for this. Optical circuits on the chips aren't going to be so affected by radiation, and by having more real-estate available for redundant components and optimal placement, they can improve the resistance to radiation considerably.
Not sure how much heat this'll cut down on, as the transistors are the big heat-producers. On the other hand, better placement means more even heat production which means they should be able to push the designs a little bit further.
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LOL!
Re:I thought they already existed (Score:5, Informative)
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2-3GHz is around the frequency that FR4 (fiber glass) material for building PCB starting to become lossy. You know some of the cheap plastic gets hot in the microwave oven, that's because the material become lossy and change the energy into heat. Same principle here.
We played with 3GHz and was already pushing it back then.
So transmitting that type of signals outside a chip for a long distance ~ 30-40cm to a backplane onto another card for say a router core or a blade server is going to take a bit more wor
Re:I thought they already existed (Score:4, Interesting)
The real benefit is you wont have to worry about cross talk or other electromagnetic interference. The short haul of the board level optical interconnects means we can have very high speed chip to chip interconnects without worrying too much about trace routing or length. And LED's are quite efficient when it comes to turning to electrical power into light. Metal wires at high frequencies develop a high resistance which has to be overcome by using more energy.
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how would the switching times of these lasers compare to that or a wire trace though?
Switching time is great; it's the photo-detection on the other end where the real expense is (for high speed at least).
Re:I thought they already existed (Score:5, Interesting)
The real benefit is you wont have to worry about cross talk or other electromagnetic interference. The short haul of the board level optical interconnects means we can have very high speed chip to chip interconnects without worrying too much about trace routing or length. And LED's are quite efficient when it comes to turning to electrical power into light. Metal wires at high frequencies develop a high resistance which has to be overcome by using more energy.
I'm not convinced. You can still get electromagnetic interference with light - look at TV remotes. Of course, if you use fibre optic cable it's not a problem, but that's akin to using coaxial cable to route electrical signals. While it would be possible to embed coaxial structures in PCBs to eliminate the possibility of cross-talk and noise, in practice this would be prohibitively expensive and the same result can be achieved with stripline and careful routing. The question is, what does an optical PCB look like? You'll still need copper for power distribution so the optical PCB will need to tolerate soldering temperatures. Do you have a layer of interwoven fibre optic cables? How do these interface with the components such that there is tolerance in the size and position of the terminals? Do you use mirrors and optical waveguides embedded in the substrate? If so how do you make this cost effective to manufacture? If you use fibre optics, you have a minimum bend radius, so you open up a whole new set of routing problems. While there are obviously clear benefits in theory, when it comes to actually implementing this as a cost effective PCB interconnect you'll have a whole set of new problems to deal with, and it's unlikely to be anywhere close in cost to gluing layers of copper and plastic together.
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I'm not convinced. You can still get electromagnetic interference with light - look at TV remotes.
Its not my area of expertise, but my understanding was that part of the point of lasers is the light is coherent. If it has an appropriate wavelength and you aim it correctly, you can transmit data at a high rate despite a fairly high level of environmental interference.
Vague impression? (Score:5, Interesting)
Having said that you are entirely right in your main observation. The main problem for germanium has always been fabrication; no germanium ICs. This is because there is no germanium equivalent of planar technology. It has been known for a long time that if this could be overcome there would be a role for germanium. It's just that, as with so many apparently breakthrough technologies, making it happen turns out to be very hard.
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Germanium also fabricates better PNP transistor than silicon so for a while, high performance complimentary circuits used PNP germanium transistors with NPN silicon ones. I have a whole reel of 1N270 germanium diodes which come in handy sometimes.
Ultimately though the increased leakage and lower peak junction temperature made germanium obsolete for most applications.
germanium junctions have 0.2V voltage drop (Score:2)
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The Birth of the Transistor [youtube.com]. Circuits In Stone [youtube.com]. watch and learn, kid.
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Germanium-based LEDs have most definitely NOT been developed before. The first ever LED was GaAs-based, and it was deep in the infrared.
Useful for clock signal? (Score:2)
Everybody's talking about how this will be useful when they do X. Why can't it be useful now?
If there's a nice open layer somewhere, maybe on the bottom of the chip, how about sending out a clock signal across the entire chip, faster than the current tree/mesh methods? Getting the entire chip in sync this way could probably let it run a good deal faster, too.
Or would reflections be a problem or something?
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If the light-sensitive components are not directional, you could have the clock emitter ABOVE the silicon on a completely independent layer. That wouldn't require them to perfect the transmission side, so could be done a lot quicker.
Foxhole Radios with Lasers! (Score:2)
If any of the fabrication goes wrong, they can always send out these germanium-on-silicon diodes as parts for the world's most expensive foxhole radios [google.com] ;)
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Somewhere I've the circuit diagram for those in an old Wireless World. Popular in PoW camps as well as in the trenches in WW2, apparently, as they could be easily assembled, easily hidden and the parts could be smuggled in via Red Cross parcels.
Re:Great (Score:4, Insightful)
Now, lets have that lead to jobs for the west, rather than simply giving the tech to China. All fo this American paid for RD, should require that the work stay in the west.
Do you really want to deny the West the advances in manufacturing that the Chinese have contributed?
It's a global economy now. Get used to it.
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Now, lets have that lead to jobs for the west, rather than simply giving the tech to China. All fo this American paid for RD, should require that the work stay in the west.
Do you really want to deny the West the advances in manufacturing that the Chinese have contributed?
It's a global economy now. Get used to it.
Because copying Henry Ford and making up for that with cheap near-slave labor is a grand contribution. By that standard, the plantation owners of the Old South were models of efficiency and innovation. Hell, they had a technique so "advanced", they didn't have to pay their workers at all! I'd say that one-ups the China model, though not by very much.
And if you want to dumb this down by talking about lithography and the use of it by the Chinese to make integrated circuits, just ask yourself whether it
solid state? (Score:2)
If this comes to pass, will it mean that things will not be 'solid state' inside the computer any more?
The 40-year old promise (Score:5, Insightful)
Some scientists showed off SiC blue LEDs in the '60s that shown brilliantly like laser light, but were not the read deal. The real blue room-temperature laser had to wait for Nakamura and a direct bandgap material.
Doping, adding nitrogen, and adding defects to the lattice to produce more light is nothing new. Look at your stop lights. It's working there, but don't count on these indirect materials suddenly turning into lasers. No need to hold your breath.
A quick scientific note. Photons have a lot of energy, but not much momentum. You get hot on a sunny day, but not blown over by the sun. Electrons fall almost directly down in the bandgap diagram to produce light. This makes direct-gap semiconductors useful for lasers. The trick one can use is to provide momentum-shifting impurities to the lattice of an indirect bandgap crystal. The electron creates a photon by dropping directly down, but some other mechanism shifts the electron momentum to create an overall diagonal transition. It's not efficient, but it works.
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Yes, Germanium has an indirect band-gap, but SiC, I thought, had a direct one. The problem with SiC was (is?) to grow a crystal of a determined orientation. As it is now, the crystal structure of SiC is pretty much random. That said, growing a thin layer of SiC (by simple CVD) on Si is promising.
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That "some other mechanism" is phonons-- lattice vibrations. The lattice vibrations temporarily turn it into a direct band gap semiconductor).
Even after all these years of research, it's still largely inefficient to have to create the phonons (heat) so that you can create the photons (the laser).
Optics Express and Optics Letters (Score:2)
I get empty pages when I turn to the websites of Optics Express and Optics letters to find the articles mentioned in the 'article' that was linked to. Can someone point me to the pdfs of the articles?
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The Stanford team's abstract is at
http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-12-10019 [opticsinfobase.org]
and the full paper is downloadable there
The MIT abstract is at
http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-34-11-1738 [opticsinfobase.org]
but you have to pay to read the paper
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Thank you!
Inter-chip communication? (Score:3, Informative)
I can see this technology being able to be used to help with inter-chip communication, perhaps to help with running more tasks in parallel, or locking/unlocking memory segments shared by the CPUs.
The only thing I see that would be a limit is having to mux/demux a lot of signals before they get put on the fiber optic cable. However fiber optic cables have a lot of bandwidth, so this may not be a big issue.
It would be nice if silicon chip lasers could replace most signal circuits on a PC board. Mainly because it would allow positioning of components to allow for better cooling and heat dissipation. Ultimately, if several fiber optic connections can replace the hundreds (going on thousands) of pins needed on a CPU to the motherboard, it would be a great advance in reliability.
Fiber optics on chips isn't new though. I remember talk about the PowerPC 603 having the ability to have this for better SMP communication.
speed advantage? (Score:1)
German dildos do what?! (Score:3, Funny)
What about Ironium? (Score:2)
Most Efficient Laser? (Score:2)
What's the most efficient laser tech, in terms of watts of electrical power in to watts of laser power out? Are there any all-optical laser devices in the high efficiency (>80%, or eve >50%) class, that are powered by incoming non-coherent light (like sunlight) but emit coherent light?