Speeding up transistors with vacuum


SEMICONDUCTOR transistors were invented in 1947 to replace vacuum tubes, but now scientists at the University of Pittsburgh are reverting to the use of vacuums for transporting electrons.

The use of vacuum is in response to the challenges posed by ever smaller transistor sizes, which are approaching the limits of physics, putting paid to further attempts to continue abiding by Moore’s Law.

According to the researchers, transistor speed is limited by the amount of time it takes for an electron to traverse from one device to another. Within solid state mediums, electrons experience collisions or scattering.

A vacuum helps with this. However, vacuum tubes traditionally have required high voltages, and they are not suited for many modern uses. The team redesigned the structure of the vacuum electronic device from the ground up.

The scientists discovered that electrons trapped inside a semiconductor at the interface with an oxide or metal layer can be easily extracted out into the air. The electrons harboured at the interface form a sheet of charges, called two-dimensional electron gas.

The interaction between electrically charged particles (termed the Coulombic repulsion) in the electron layer enables the easy emission of electrons out of silicon. The team could extract electrons from the silicon structure efficiently by applying a small amount of voltage, and then placed them in the air, allowing collision- and scattering-free travel.

If this system is applied in vacuum channels, transistors would run faster while using less power.