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Long-standing device gets a nanotechnology boost

It's taking a dive into nanotechnology, but the III-V tunneling field effect transistor (TFET) is finally creeping close to the widely used metal-oxide-semiconductor field effect transistor (MOSFET).

III-V TFETs are a three terminal extension of the tunneling diode, a device invented in 1957, which earned inventor Leo Esaki a Nobel Prize in Physics.  Nicknamed the "Esaki transistor/diode" in his honor, the device went largely overlooked due to low driving currents in most applicable materials.

But a team led by electrical engineering professor Sean Rommel at the Rochester Institute of Technology (RIT) has tuned the transistors to approach MOSFET performance.  A key to the tuning was the work of graduate researcher David Pawlik who grew sub-120 nanometer vertical TFETs on a test chip that allow hundreds of diodes to be tested per sample.  The research allowed multiple kinds of homojunction and heterojunctions to be tested.

Working with fellow graduate researchers Brian Romanczyk and Paul Thomas, as well as collaborators at SEMATECH (a non-profit research consortium backed by top chipmakers) and Texas State University, the team recorded a record peak current density of 2.2 MA/cm^2.

The benefit of the III-V TFET is that they operate at a much lower voltage than MOSFETs and thus consume less watts of power.  The record setting design ran at -0.3 V.

Knapps tunnel
As its name implies, a tunneling FET is similar voltage wise to driving through a hill, instead of down one, says Professor Rommel. [Image Source: NCWpics]

Professor Rommel likens the traditional MOSFET to driving down a hill, voltage-wise, while the TFET, driven by quantum effects, is more like digging a tunnel through the hill.  He comments on the record current levels, "The tunneling field effect transistors have not yet demonstrated a sufficiently large drive current to make it a practical replacement for current transistor technology, but this work conclusively established the largest tunneling current ever experimentally demonstrated, answering a key question about the viability of tunneling field effect transistor technology."

He suggests in the paper that a peak current of 10 MA/cm^2 should be possible with high levels of doping in indium-based heterojunctions.

The results could be applied in everything from smartphones to solar cells.  Professor Rommel suggests tuned TFETs could reduce processor power consumption by a factor of 10, allowing longer battery life for phones and other devices.

The work was presented at a December at the International Electron Devices Meeting (IEDM) in San Francisco, Calif.  The work was funded by The National Science Foundation (NSF), SEMATECH, and RIT's Office of the Vice President of Research.

Sources: RIT, ResearchGate [paper]

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RE: Back in the dark ages
By ShieTar on 2/1/2013 5:34:42 AM , Rating: 1
I'm not working in the field, but I have the feeling that right now the only predicted real-world application of photonic computing seems to be to remove the electronic parts from the optical transmission systems of telecommunication. Of course if this is implemented in the network providers infrastructure, it may trickle down into personal network electronics, especially once Fibre-to-the-Home becomes a mass product.

For purely computational purposes, the ongoing success of parallelisations of tasks makes single-module speed increasingly less relevant, while power efficiency becomes increasingly important, both in private mobile devices and in large-scale supercomputing installations. Since power is always stored electrically, the efficiency handicap of electrical to optical conversion makes fully photonics CPUs a lot less promising concept than it was considered 20 years ago.

The same problem will probably remain forever the case for quantum computation. While the computing atom/molecule itself may be quiete fast and efficient, it always needs to be thermally and optically decoupled from its environment, so in all likelyhood you will never be able to have a quantum computer without a high-cost, high-energy-consumption thermal vacuum chamber. I'd love to be proven wrong here, but right now I don't see even a theorectical concept on how to get there.

"Nowadays, security guys break the Mac every single day. Every single day, they come out with a total exploit, your machine can be taken over totally. I dare anybody to do that once a month on the Windows machine." -- Bill Gates

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