5 ms·

Carbon Nanotubes Finally Outperform Silicon in Transistors

154 points by xd 10y ago

traviswingo 10y ago
This is a really important advancement in circuits. We were reaching the physical limits of silicon and it was only a matter of time before we would have to find an alternative to continue the upward trends of transistor performance.
- GregBuchholz 10y ago
  There are quite a few materials which outperform straight silicon, but it is hard to compete with the gigantic amount of existing silicon infrastructure, except for very niche applications. https://en.wikipedia.org/wiki/High-electron-mobility_transistor https://en.wikipedia.org/wiki/High-electron-mobility_transis...
nutschig 10y ago
Silicon is not the best transistor material ever. For example, gallium arsenide can run at a switching frequency of 250 GHz thanks to faster electron velocity and higher electron mobility. https://en.wikipedia.org/wiki/Gallium_arsenide#GaAs_advantages https://en.wikipedia.org/wiki/Gallium_arsenide#GaAs_advantag...
- duaneb 10y ago
  > thanks to faster electron velocity and higher electron mobility. How does this effect energy transfer? This is the metric I assume most people care about as it is typically much faster than an electron can move.
- GregBuchholz 10y ago
  You can create some pretty high frequency transistors (BJTs) with Indium Phosphide (InP) (ft > 600GHz, fmax > 1THz). See page 33 of: http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_presentations/publications/2012_10_15_Oct_rodwell_CSIC_talk.pdf http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_pre... ...for examples of some 600 GHz circuits, and: http://www.semiconductor-today.com/news_items/2014/OCT/NORTHROP-GRUMMAN_311014.shtml http://www.semiconductor-today.com/news_items/2014/OCT/NORTH... ...for a >1THz circuit using InP HEMTs.
  - raverbashing 10y ago
    Wow that's crazy. I wonder how you even test a 1THz amplifier. Also what kind of natural noise might exist in those bands
    - GregBuchholz 10y ago
      >I wonder how you even test a 1THz amplifier. Most likely using a mixer or some other non-linearity to down convert into the frequency range of your spectrum analyzer.
      - raverbashing 10y ago
        And how do you get the 1THz signal in the 1st place? Maybe upconvert as well?
    - jpmattia 10y ago
      > I wonder how you even test a 1THz amplifier. The usual schtick is to measure the S-parameters a slower speeds and extrapolate out to the cutoff. (see chart 21 from the link above: http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_presentations/publications/2012_10_15_Oct_rodwell_CSIC_talk.pdf http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_pre...) For the digital people, building a ring oscillator with N stages will cause the output to divide by N, and just make sure that f/N is in the range of your oscilloscope. To actually measure things up in the THz range directly, there are more exotic methods: Superconducting bolometer is one that I've been involved with. But those are a PITA for a bunch of reasons.
  - pbhjpbhj 10y ago
    Does 'Heisenberg' or some other theory limit the top frequency, if so, what's the limit?
- klodolph 10y ago
  "Best" is a funny word, because it means different things to people who care about different things. Silicon can be built with better gates / insulators than gallium arsenide, so if that's what you care about, silicon is better.
- buserror 10y ago
  I, for one, have a Germanium transistor in my 1964 Accutron Bulova watch. So there! http://www.decadecounter.com/accutron/history.htm http://www.decadecounter.com/accutron/history.htm
  - jpmattia 10y ago
    Old joke: It's not that Germanium has a bad bandgap, it's just that room temperature is wrong. [As it turns out, having a decent native oxide is also a winner.)
ChuckMcM 10y ago
I don't doubt that eventually our chips will be structured carbon circuits on a diamond substrate. I find it amusing that should a sentient AI arise post transition, it could reasonably think of itself as a carbon based life form :-). The question I have not seen addressed is how we'll pattern the circuits. The ability to convert silicon into N-type and P-type material by doping is so "simple" compared to trying to induce the formation of CNTs of a particular geometry with the precision needed to develop a particular circuit. We are at the 'Bell labs' point where we can make individual (and volumetrically large) transistors out of CNTs or Graphene. But as we know from history, the revolution didn't really get underway until we could pattern a complete circuit on a substrate in the form of an integrated circuit. I'm still watching for the folks who come up with that breakthrough.
- deleted 10y ago
  [deleted]
- ChuckMcM 10y ago
  Interesting, not sure why shpx deleted their comment but it lead me to Max Shulaker who is figuring out how to build integrated circuits out of these things. Looks promising and I am surprised I missed it. Thanks shpx! [1] https://www.researchgate.net/profile/Zuanyi_Li2/publication/261030187_Carbon_Nanotube_Circuit_Integration_up_to_Sub-20_nm_Channel_Lengths/links/00b49536d8537cb839000000.pdf https://www.researchgate.net/profile/Zuanyi_Li2/publication/...
- Florin_Andrei 10y ago
  > I find it amusing that should a sentient AI arise post transition, it could reasonably think of itself as a carbon based life form The best of everything (X) ends up carbon-based. Life forms, computers, space towers, etc. It's just due to the carbon atom having a bunch of unusual properties. (X) - whereas "everything" is an exaggeration used to make a point
  - Razengan 10y ago
    I'm not sure if that sentiment isn't carbon chauvinism, given that the best we know so far has been carbon-based. I'm sure the universe in its infinity has plenty of surprises in store for an species that has yet to leave their home planet.
Symmetry 10y ago
I'm sure that people will be able to create very fast carbon nanotube transistors (CNTFETs) in the future but that isn't currently the problem. Generally when you're creating normal silicon transistors (MOSFETs) one out of every billion or so is bad, meaning you have to fuse off some block of cache or maybe an entire core but multi-billion transistor chips are possible when you do stuff like that. My understanding of the state of the art of CNTFETs right now is that only having one out of every 10 be bad would be a significant advance. So making 10 transistor circuits is maybe feasible but nothing larger. And even the 8086 had 20,000 transistors. There's a lot of work that has to be done before CNTFETs are ready to be used in computers.
wav-part 10y ago
Paper : http://advances.sciencemag.org/content/advances/2/9/e1601240.full.pdf http://advances.sciencemag.org/content/advances/2/9/e1601240... Previous Discussion : https://news.ycombinator.com/item?id=12429779 https://news.ycombinator.com/item?id=12429779 (39 days ago, 42 comments)
mankash666 10y ago
Even if the science becomes feasible, this domain in encumbered with too many patents.
- happycube 10y ago
  That'd explain why the military is funding it - patents don't apply to them!
madengr 10y ago
I thought it was innterconnect loss and heat dissipation that is keeping processor clocks slow, not intrinsic transistor speed.

154 points by xd 10y ago

This is a really important advancement in circuits. We were reaching the physical limits of silicon and it was only a matter of time before we would have to find an alternative to continue the upward trends of transistor performance.

GregBuchholz 10y ago
There are quite a few materials which outperform straight silicon, but it is hard to compete with the gigantic amount of existing silicon infrastructure, except for very niche applications. https://en.wikipedia.org/wiki/High-electron-mobility_transistor https://en.wikipedia.org/wiki/High-electron-mobility_transis...

nutschig 10y ago

Silicon is not the best transistor material ever. For example, gallium arsenide can run at a switching frequency of 250 GHz thanks to faster electron velocity and higher electron mobility. https://en.wikipedia.org/wiki/Gallium_arsenide#GaAs_advantages https://en.wikipedia.org/wiki/Gallium_arsenide#GaAs_advantag...

duaneb 10y ago
> thanks to faster electron velocity and higher electron mobility. How does this effect energy transfer? This is the metric I assume most people care about as it is typically much faster than an electron can move.
GregBuchholz 10y ago
You can create some pretty high frequency transistors (BJTs) with Indium Phosphide (InP) (ft > 600GHz, fmax > 1THz). See page 33 of: http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_presentations/publications/2012_10_15_Oct_rodwell_CSIC_talk.pdf http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_pre... ...for examples of some 600 GHz circuits, and: http://www.semiconductor-today.com/news_items/2014/OCT/NORTHROP-GRUMMAN_311014.shtml http://www.semiconductor-today.com/news_items/2014/OCT/NORTH... ...for a >1THz circuit using InP HEMTs.
- raverbashing 10y ago
  Wow that's crazy. I wonder how you even test a 1THz amplifier. Also what kind of natural noise might exist in those bands
  - GregBuchholz 10y ago
    >I wonder how you even test a 1THz amplifier. Most likely using a mixer or some other non-linearity to down convert into the frequency range of your spectrum analyzer.
    - raverbashing 10y ago
      And how do you get the 1THz signal in the 1st place? Maybe upconvert as well?
  - jpmattia 10y ago
    > I wonder how you even test a 1THz amplifier. The usual schtick is to measure the S-parameters a slower speeds and extrapolate out to the cutoff. (see chart 21 from the link above: http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_presentations/publications/2012_10_15_Oct_rodwell_CSIC_talk.pdf http://www.ece.ucsb.edu/Faculty/rodwell/publications_and_pre...) For the digital people, building a ring oscillator with N stages will cause the output to divide by N, and just make sure that f/N is in the range of your oscilloscope. To actually measure things up in the THz range directly, there are more exotic methods: Superconducting bolometer is one that I've been involved with. But those are a PITA for a bunch of reasons.
- pbhjpbhj 10y ago
  Does 'Heisenberg' or some other theory limit the top frequency, if so, what's the limit?
klodolph 10y ago
"Best" is a funny word, because it means different things to people who care about different things. Silicon can be built with better gates / insulators than gallium arsenide, so if that's what you care about, silicon is better.
buserror 10y ago
I, for one, have a Germanium transistor in my 1964 Accutron Bulova watch. So there! http://www.decadecounter.com/accutron/history.htm http://www.decadecounter.com/accutron/history.htm
- jpmattia 10y ago
  Old joke: It's not that Germanium has a bad bandgap, it's just that room temperature is wrong. [As it turns out, having a decent native oxide is also a winner.)

ChuckMcM 10y ago

I don't doubt that eventually our chips will be structured carbon circuits on a diamond substrate. I find it amusing that should a sentient AI arise post transition, it could reasonably think of itself as a carbon based life form :-). The question I have not seen addressed is how we'll pattern the circuits. The ability to convert silicon into N-type and P-type material by doping is so "simple" compared to trying to induce the formation of CNTs of a particular geometry with the precision needed to develop a particular circuit. We are at the 'Bell labs' point where we can make individual (and volumetrically large) transistors out of CNTs or Graphene. But as we know from history, the revolution didn't really get underway until we could pattern a complete circuit on a substrate in the form of an integrated circuit. I'm still watching for the folks who come up with that breakthrough.

deleted 10y ago
[deleted]
ChuckMcM 10y ago
Interesting, not sure why shpx deleted their comment but it lead me to Max Shulaker who is figuring out how to build integrated circuits out of these things. Looks promising and I am surprised I missed it. Thanks shpx! [1] https://www.researchgate.net/profile/Zuanyi_Li2/publication/261030187_Carbon_Nanotube_Circuit_Integration_up_to_Sub-20_nm_Channel_Lengths/links/00b49536d8537cb839000000.pdf https://www.researchgate.net/profile/Zuanyi_Li2/publication/...
Florin_Andrei 10y ago
> I find it amusing that should a sentient AI arise post transition, it could reasonably think of itself as a carbon based life form The best of everything (X) ends up carbon-based. Life forms, computers, space towers, etc. It's just due to the carbon atom having a bunch of unusual properties. (X) - whereas "everything" is an exaggeration used to make a point
- Razengan 10y ago
  I'm not sure if that sentiment isn't carbon chauvinism, given that the best we know so far has been carbon-based. I'm sure the universe in its infinity has plenty of surprises in store for an species that has yet to leave their home planet.

Symmetry 10y ago

I'm sure that people will be able to create very fast carbon nanotube transistors (CNTFETs) in the future but that isn't currently the problem. Generally when you're creating normal silicon transistors (MOSFETs) one out of every billion or so is bad, meaning you have to fuse off some block of cache or maybe an entire core but multi-billion transistor chips are possible when you do stuff like that. My understanding of the state of the art of CNTFETs right now is that only having one out of every 10 be bad would be a significant advance. So making 10 transistor circuits is maybe feasible but nothing larger. And even the 8086 had 20,000 transistors. There's a lot of work that has to be done before CNTFETs are ready to be used in computers.

wav-part 10y ago

Paper : http://advances.sciencemag.org/content/advances/2/9/e1601240.full.pdf http://advances.sciencemag.org/content/advances/2/9/e1601240... Previous Discussion : https://news.ycombinator.com/item?id=12429779 https://news.ycombinator.com/item?id=12429779 (39 days ago, 42 comments)

mankash666 10y ago

Even if the science becomes feasible, this domain in encumbered with too many patents.

happycube 10y ago
That'd explain why the military is funding it - patents don't apply to them!

madengr 10y ago

I thought it was innterconnect loss and heat dissipation that is keeping processor clocks slow, not intrinsic transistor speed.