Principle Investigator: Meyya Meyyappan
Vacuum tubes went away because their replacement – the integrated circuit – could be miniaturized and operated at significantly lower power levels. However, vacuum is superior to all semiconductors because electrons do not suffer any collisions and thus electron transport is the fastest possible.
The novel idea in our work is to combine the best of vacuum tubes and conventional silicon semiconductor processing to create nanoscale vacuum tubes or transistors. Why? It is possible to get high speed operation at low power levels. More importantly, for NASA and the military, the device will be inherently immune to space radiation. Thus, high performance devices can be used very quickly in missions without the usual extensive steps involving radiation-proofing steps and packaging requirements.
As a preliminary demonstration, we have fabricated a nanoscale vacuum transistor with a source-drain gap of 150 nm. Note that currently commercial production of silicon chips features a 32 nm gap in silicon based transistors, about 5 times smaller than our first effort. Our device shows an operating frequency of 0.4 THz or 400 GHz, already exceeding the performance of commercial devices. We are currently working on wafer-scale fabrication as opposed to individual devices. The processing steps in our work are identical to those in conventional integrated circuit manufacturing and thus fabrication costs are expected to be low as in semiconductor industry. In this regard, a competitive advantage exists compared to novel materials such as graphene or carbon nanotubes which are struggling to reach wafer scale production.