>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]
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 13:04:13 PDT