[IWAR] QUANTUM tunneling transistor

From: Mark Hedges (hedgesat_private)
Date: Thu Feb 05 1998 - 12:08:13 PST

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    >Forwarded message:
    >> Date: Wed, 4 Feb 1998 11:01:53 -0500 (EST)
    >> From: physnewsat_private (AIP listserver)
    >> Subject: update.357
    >> A QUANTUM TUNNELING TRANSISTOR, an on-off switch
    >> that exploits an electron's ability to pass through normally
    >> impenetrable barriers, has been built by Sandia researchers (Jerry
    >> Simmons, 505-844-8402), opening possibilities for record-speed
    >> transistors that can be mass-produced with current nanotechnology.
    >>  In their device, the researchers control the flow of electrons
    >> between two GaAs layers (each only 15 nm thick) separated by an
    >> AlGaAs barrier (12 nm).  Although the electrons in GaAs
    >> ordinarily do not have enough energy to enter the AlGaAs barrier,
    >> the layers are so thin (comparable in size to the electron
    >> wavelength) that the electrons, considered as waves rather than
    >> particles, can spread into the barrier and, with an appropriate
    >> voltage applied, out the other side.  In the process, the electron
    >> waves do not collide with impurity atoms, in contrast to a
    >> traditional transistor's particlelike electrons, which are slowed
    >> down by these collisions.  Transistors that switch on and off a
    >> trillion times per second--5 times faster than the current record--are
    >> possible with this approach.  Although quantum tunneling
    >> transistors were first built in the late 1980s, it was originally
    >> infeasible to mass-produce them.  Previous researchers engraved
    >> the ultrathin GaAs and AlGaAs features side-by-side on a surface,
    >> something hard to do reliably with present-day lithography.
    >> Therefore the Sandia researchers stacked the features vertically, by
    >> using readily available techniques such as molecular beam epitaxy
    >> which can deposit layers of material with single-atom thicknesses.
    >> Having made quantum-tunneling memory devices and digital logic
    >> gates operating at 77 K, the researchers expect room-temperature
    >> devices in the next year.  (J.A. Simmons et al., upcoming article
    >> in Applied Physics Letters; figure at
    >> www.aip.org/physnews/graphics)
    >[text deleted]

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