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A subthermionic tunnel field-effect transistor with an atomically thin channel

Abstract

The fast growth of information technology has been sustained by continuous scaling down of the silicon-based metal–oxide field-effect transistor. However, such technology faces two major challenges to further scaling. First, the device electrostatics (the ability of the transistor’s gate electrode to control its channel potential) are degraded when the channel length is decreased, using conventional bulk materials such as silicon as the channel. Recently, two-dimensional semiconducting materials1,2,3,4,5,6,7 have emerged as promising candidates to replace silicon, as they can maintain excellent device electrostatics even at much reduced channel lengths. The second, more severe, challenge is that the supply voltage can no longer be scaled down by the same factor as the transistor dimensions because of the fundamental thermionic limitation of the steepness of turn-on characteristics, or subthreshold swing8,9. To enable scaling to continue without a power penalty, a different transistor mechanism is required to obtain subthermionic subthreshold swing, such as band-to-band tunnelling10,11,12,13,14,15,16. Here we demonstrate band-to-band tunnel field-effect transistors (tunnel-FETs), based on a two-dimensional semiconductor, that exhibit steep turn-on; subthreshold swing is a minimum of 3.9 millivolts per decade and an average of 31.1 millivolts per decade for four decades of drain current at room temperature. By using highly doped germanium as the source and atomically thin molybdenum disulfide as the channel, a vertical heterostructure is built with excellent electrostatics, a strain-free heterointerface, a low tunnelling barrier, and a large tunnelling area. Our atomically thin and layered semiconducting-channel tunnel-FET (ATLAS-TFET) is the only planar architecture tunnel-FET to achieve subthermionic subthreshold swing over four decades of drain current, as recommended in ref. 17, and is also the only tunnel-FET (in any architecture) to achieve this at a low power-supply voltage of 0.1 volts. Our device is at present the thinnest-channel subthermionic transistor, and has the potential to open up new avenues for ultra-dense and low-power integrated circuits, as well as for ultra-sensitive biosensors and gas sensors18,19,20,21.

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Figure 1: Schematic and working principle of the ATLAS-TFET.
Figure 2: Fabrication of an ATLAS-TFET and characterization results.
Figure 3: Room-temperature electrical characteristics of an ATLAS-TFET in diode configuration.
Figure 4: Room-temperature electrical characteristics of an ATLAS-TFET.

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Acknowledgements

This work was supported by the Air Force Office of Scientific Research (grant FA9550-14-1-0268) and the US NSF (grant CCF-1162633). Y.G. was supported by the Army Research Office (MURI grant W911NF-11-1-0362). All process steps for device fabrication were carried out using the Nanostructure Cleanroom Facility at the California NanoSystems Institute and the Nanofabrication Facilities at UCSB—part of the National Nanotechnology Infrastructure Network. We made extensive use of the MRL Central Facilities at UCSB, which are supported by the MRSEC Program of the NSF (award no. DMR 1121053), a member of the NSF-funded Materials Research Facilities Network (http://www.mrfn.org).

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Authors

Contributions

K.B. initiated, planned and led the research. D.S. designed and fabricated the devices, collected and analysed the data, with input from X.X., W.L., W.C. and J.K. X.X. and W.L. performed Raman analysis. W.C. collected and analysed data on previously demonstrated tunnel-FET devices. Y.G. and P.M.A. synthesized large-area bilayered MoS2 samples. S.K. performed TEM analysis. D.S. and K.B. wrote the main Letter and the Supplementary Information with input from all other authors.

Corresponding author

Correspondence to Kaustav Banerjee.

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The authors declare no competing financial interests.

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This file contains Supplementary Text and Data 1-19, Supplementary Figures 1-22, Supplementary Table 1 and additional references. (PDF 1568 kb)

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Sarkar, D., Xie, X., Liu, W. et al. A subthermionic tunnel field-effect transistor with an atomically thin channel. Nature 526, 91–95 (2015). https://doi.org/10.1038/nature15387

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