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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 Stiggalicious on 2/1/2013 11:16:40 PM , Rating: 2
Seeing the advances taken in optical transceiver circuits and the prices of the devices utilizing them seems to be a very promising technological advancement for the mainstream.
As of right now, we're approaching the limits of using copper as a transmission medium for data over any length greater than a couple meters (I'm talking like 100Gbits). Ethernet, which traditionally runs over copper, will soon (and already are for building-to-building connections) go to optical communications. As the speed increases even further, the maximum distance for copper will decrease even further. You'll then see things like PCIe eventually be replaced with optical interconnects. The CPU, however, will remain in silicon for the forseeable future. Photonics are still nigh-impossible to manufacture at a remotely reasonable price.


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