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Metal–oxide–semiconductor field-effect transistor with a vacuum channel

Abstract

High-speed electronic devices rely on short carrier transport times, which are usually achieved by decreasing the channel length and/or increasing the carrier velocity. Ideally, the carriers enter into a ballistic transport regime in which they are not scattered1. However, it is difficult to achieve ballistic transport in a solid-state medium because the high electric fields used to increase the carrier velocity also increase scattering2. Vacuum is an ideal medium for ballistic transport, but vacuum electronic devices commonly suffer from low emission currents and high operating voltages. Here, we report the fabrication of a low-voltage field-effect transistor with a vertical vacuum channel (channel length of 20 nm) etched into a metal–oxide–semiconductor substrate. We measure a transconductance of 20 nS µm–1, an on/off ratio of 500 and a turn-on gate voltage of 0.5 V under ambient conditions. Coulombic repulsion in the two-dimensional electron system3 at the interface between the oxide and the metal or the semiconductor reduces the energy barrier to electron emission, leading to a high emission current density (1 × 105 A cm–2) under a bias of only 1 V. The emission of two-dimensional electron systems into vacuum channels could enable a new class of low-power, high-speed transistors.

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Figure 1: Ballistic transport of electrons in nano-void channels in silicon MOS.
Figure 2: Energy band diagrams.
Figure 3: Measurement of electron capture efficiency at anode edges.
Figure 4: Nano-void channel FET.

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Acknowledgements

This work was supported by the National Science Foundation (grant no. ECCS-0925532).

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Contributions

S.S. carried out device processing and characterization. Y.S.J. performed FIB etching for nano-void channel fabrication. H.K.K. designed the study, provided theoretical guidance, and supervised the entire project. H.K.K. wrote the manuscript with comments from S.S. and Y.S.J.

Corresponding author

Correspondence to Hong Koo Kim.

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The authors declare no competing financial interests.

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Srisonphan, S., Jung, Y. & Kim, H. Metal–oxide–semiconductor field-effect transistor with a vacuum channel. Nature Nanotech 7, 504–508 (2012). https://doi.org/10.1038/nnano.2012.107

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