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Gate-controlled guiding of electrons in graphene

Abstract

Ballistic semiconductor structures have allowed the realization of optics-like phenomena in electronic systems, including the magnetic focusing1 and electrostatic lensing2 of electrons. An extension that appears unique to graphene is to use both n and p carrier types to create electronic analogues of optical devices with both positive and negative indices of refraction3. Here, we use the gate-controlled density of both p and n carrier types in graphene to demonstrate the electronic analogue of fibre-optic guiding4,5,6,7,8. Two basic effects are investigated: bipolar p–n junction guiding, based on the principle of angle-selective transmission through the interface between the graphene and the p–n junction; and unipolar fibre-optic guiding, using total internal reflection controlled by carrier density. We also demonstrate modulation of the guiding efficiency through gating, and comparison of these data with numerical simulations indicates that guiding performance is limited by the roughness of the interface. The development of p–n and fibre-optic guiding in graphene may lead to electrically reconfigurable wiring in high-mobility devices.

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Figure 1: Schematics of the device and guiding in unipolar and bipolar regimes.
Figure 2: Simulated optical and p–n guiding in gated graphene.
Figure 3: Effects of gating and disorder on guiding efficiency
Figure 4: Magnetic field improves gate-defined guiding.

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Acknowledgements

Device fabrication was carried out using Harvard's Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network under National Science Foundation award ECS-0335765, and was supported in part by the Institute for Nanoelectronics Discovery and Exploration, a Nanoelectronics Research Initiative Center, and the Harvard Nanoscale Science and Engineering Center.

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Contributions

Experiments were performed by J.W. and C.M, and numerics/theory by T.L. and M.L. All authors contributed to writing the manuscript.

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Correspondence to C. M. Marcus.

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The authors declare no competing financial interests.

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Williams, J., Low, T., Lundstrom, M. et al. Gate-controlled guiding of electrons in graphene. Nature Nanotech 6, 222–225 (2011). https://doi.org/10.1038/nnano.2011.3

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