
MIT creates tiny, 22nm transistor without silicon - evo_9
http://www.extremetech.com/extreme/143024-mit-creates-tiny-22nm-transistor-without-silicon
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ori_b
_"This tiny InGaAs transistor was mostly fashioned from normal semiconductor
processes — molecular beam epitaxy, electron beam lithography, and so on."_

It's important to note that these are normal semiconductor processes for low
volume manufacturing. These are not the high volume methods that, say, Intel
would use. It remains to be seen whether the material will work well with
common high volume ion implant and lithography technologies.

The reason Silicon is the dominant material isn't purely because of it's
electrical characteristics. We've already got better material that's costly to
manufacture. GaAs, for example. In addition to good electrical properties,
Silicon wins because it's extremely to manufacture chips with in bulk.

To be fair, the article does touch on this.

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Osmium
Seconded; molecular beam epitaxy is certainly not an industrial technique!
Here's a picture of some MBE equipment via Google:

[http://www.sandia.gov/LabNews/LN06-16-00/images/beam_pix.jpe...](http://www.sandia.gov/LabNews/LN06-16-00/images/beam_pix.jpeg)

It's large, complicated, expensive, difficult to optimise and run, and
ultimately can only grow very small amounts of (admittedly high quality)
material (relative to the size of equipment and the time it takes to do the
growing). On a simple level, it works by creating a "beam" of atoms which you
can deposit onto a surface to grow your crystal layer-by-layer: this most
definitely _is not_ something that scales well to industrial sizes.

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jpdoctor
> _molecular beam epitaxy is certainly not an industrial technique!_

Of course MBE is an industrial technique: A fair fraction of the semiconductor
lasers on the planet are made this way, and probably a decent fraction of the
microwave power amps for cell phones.

The thing that is interesting here: There is an optimal stoichiometry for
electron velocity in InGaAs, and it is hard to lattice match with a substrate
for that composition. Usually there is magic in the buffer layers. (IIRC)

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Osmium
Thanks for the correction; I had the article in mind, talking about it
replacing Si transistors, and can't really imagine MBE being used to produce
millions of chips, though I'd be happy to be wrong about that.

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jpdoctor
> _and can't really imagine MBE being used to produce millions of chips_

Cell phones are example application for millions of chips. There's really
nothing that magic about it.

What _is_ difficult is the large-scale integration of transistors, which is
why you don't see CPUs (for example). There's a number of reasons, mostly
relating to the nature of III-V materials. One example is the lack of a decent
oxide: SiO2 is god's gift to electronics.

However, Si is not a direct bandgap, so it is next to useless for devices
involving light. It's why the bazillions of lasers on the planet are III-V.

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crististm
So, what's new except for the size? GaAs has been around for _quite_ a while.

Discrete high-frequency and low-noise transistors are made from GaAs for more
than 15 years.

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jpdoctor
> _for more than 15 years._

Much longer than that. It was old news when I started grad school (1989).

As for what's new: The link to extreme tech is (as usual) useless. If you hit
the linked original article: [http://web.mit.edu/newsoffice/2012/tiny-
compound-semiconduct...](http://web.mit.edu/newsoffice/2012/tiny-compound-
semiconductor-transistor-could-challenge-silicons-dominance-1210.html)

you will find more info, but it's quite sketchy. The press-release say MOSFET,
but I'd be quite surprised if they didn't really mean MODFET (oxides of III-V
are a royal PITA). My guess is that this is a proof of concept for lateral
22nm devices, ie what would be state of the art litho for the silicon world.

Edit: Dear mods - it would make sense to repoint the OP to my link above.
Extremetech confuses the PR and does not enhance the original info.

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duaneb
So, silicon is virtually everywhere. How would this affect manufacturing
costs?

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jivatmanx
Yep, earth is a rocky planet - composed primarily of silicate rocks.

