

UCLA claims 300-GHz graphene transistors - rexyo
http://www.edn.com/article/510523-UCLA_claims_300_GHz_graphene_transistors.php

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pjscott
Note that just because someone's invented transistors that can switch at 300
GHz, doesn't mean that you can make a processor which will be able to run with
a 300 GHz clock speed. These are two completely different issues, and articles
with things like "300 GHZ!" in the headlines often play off this confusion to
get page views.

There are already transistors which can switch at much higher frequencies.
They're mainly used in radio communications. The promise of graphene
semiconductors is that they may be a way of replacing or supplementing
silicon, so it's nice that graphene transistors are turning out to have good
performance, but the really big issue continues to be figuring out how to
mass-produce non-trivial devices. Or even trivial ones.

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jacquesm
Light will travel about a millimeter in the time it takes these transistors to
switch, how will this be practical?

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Groxx
How would it be... impractical? That means light goes ~ 7,000 times further
than the width of the gate (140 nanometer ones have been made) in the same
time span. They're hardly pushing any theoretical limits as pertain to the
speed of light.

(light speed / 300 billion hertz) * (1 billion nanometers per meter / 140nm) =
7,137.91567 , according to Google's calculator.

~~~
jacquesm
It's a problem because in chip therms that is tiny, and you still need to
interface to the outside world, using regular wiring you're _much_ slower than
300GHz, and using optics you have a pretty serious interfacing issue.

Of course even a 10-fold practical increase would be an amazing thing, but I
just can't see the 300GHz ever becoming a reality given the constraints that
physics imposes on this.

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sasvari
_but I just can't see the 300GHz ever becoming a reality given the constraints
that physics imposes on this._

There are already proven cutoff frequencies for InP-based bipolar transistor
up to _755 GHz_ with demonstrated amplifiers with _fmax = 324 GHz_.

[http://www.ece.ucsb.edu/Faculty/Rodwell/publications/2008_10...](http://www.ece.ucsb.edu/Faculty/Rodwell/publications/2008_10_oct_rodwell_csic_digest.pdf)

~~~
jacquesm
Sure, but that does not translate in to computing speed.

I would not be surprised if that turned out to be 1/10th or less of the device
theoretical maximum switching speed.

300GHz is a frequency at which just about every conductor is a coil of sorts.
Stripline all the way :)

Or did you miss the 'in chip terms'?

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sasvari
_Or did you miss the 'in chip terms'?_

Sorry, you are right. The more complex your chip is going to be, the more
trouble you have with RF issues.

Nevertheless, what I meant is, there will be components working in the _low
THz_ range, as they are already demonstration objects. Most probably you won't
see this components in consumer products or in computing, due to cost, scaling
and implementation issues. But for some applications I think this will be
applicable.

