Vacuum channel transistors promise significant speed improvement in chips

Researchers think they can stretch Moore’s Law for transistors a bit further by reverting to vacuum technology. The first transistors with a vacuum channel have already been produced and could be used for communication, among other things.

The new type of transistor was developed by employees of the Ames Research Center, part of NASA. The vacuum channel transistors could be used in communication equipment: their design allows very high speeds that are not achievable with traditional silicon mosfets. The researchers’ first prototype achieved a switching speed of 460GHz, which would allow the transistors in the terahertz band to be used for transmitters and receivers.

However, it is not there yet: the prototype still works with a voltage of 10V, which is too high for use with normal transistors. However, by modifying the design, the ‘vacuum transistors’ could operate at similar voltages to normal transistors and be housed together on chips. The production of the vacuum transistors is already suitable for this: standard production techniques used in the semiconductor industry are also suitable for the production of the vacuum transistors.

The transistors work in a somewhat similar way to the vacuum tubes. the predecessors of modern transistors: however, they do not have the disadvantages of those tubes. This way they don’t have to heat up because no warm cathode is needed. Moreover, there is no need for a vacuum at all in the channel: such a vacuum is not necessary at all over the small distances, but helium can be used. The researchers are making the distance between anode and cathode so short that the chance of collisions between electrons and gas molecules is low. Moreover, the electrons with the voltages used have too little energy to excite helium molecules. The ions that would be formed could damage the cathode.

The vacuum transistors largely work like a regular mosfet, with a gate electrode that regulates the current between the cathode and anode, or the source and drain. The source and drain electrodes are sharp electrodes, between which electrons can cross. They are not hindered by collisions, as in a semiconductor material in traditional transistors. The researchers will now focus on the design of circuits with a large number of these vacuum transistors, which will probably require the use of MEMS techniques to ensure the correct helium atmosphere.