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Photoexcitation cascade and multiple hot-carrier generation in graphene

Nature Physics volume 9, pages 248–252 (2013)Cite this article

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Abstract

The conversion of light into free electron–hole pairs constitutes the key process in the fields of photodetection and photovoltaics. The efficiency of this process depends on the competition of different relaxation pathways and can be greatly enhanced when photoexcited carriers do not lose energy as heat, but instead transfer their excess energy into the production of additional electron–hole pairs through carrier–carrier scattering processes. Here we use optical pump–terahertz probe measurements to probe different pathways contributing to the ultrafast energy relaxation of photoexcited carriers. Our results indicate that carrier–carrier scattering is highly efficient, prevailing over optical-phonon emission in a wide range of photon wavelengths and leading to the production of secondary hot electrons originating from the conduction band. As hot electrons in graphene can drive currents, multiple hot-carrier generation makes graphene a promising material for highly efficient broadband extraction of light energy into electronic degrees of freedom, enabling high-efficiency optoelectronic applications.

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Figure 1: Experimental realization and results.
Figure 2: Carrier–carrier scattering efficiency.

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Acknowledgements

We acknowledge financial support from an NWO Rubicon grant (K.J.T.), the NSS programme, Singapore (J.C.W.S.), Office of Naval Research Grant No. N00014-09-1-0724 (L.S.L.), and Fundacio Cellex Barcelona and ERC Career integration grant GRANOP (F.H.L.K.). We thank J. Versluis for technical assistance.

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Authors and Affiliations

  1. ICFO—Institut de Ciéncies Fotóniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain

    K. J. Tielrooij & F. H. L. Koppens

  2. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    J. C. W. Song & L. S. Levitov

  3. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA

    J. C. W. Song

  4. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

    S. A. Jensen & M. Bonn

  5. FOM Institute AMOLF, Amsterdam, Science Park 104, 1098 XG Amsterdam, Netherlands

    S. A. Jensen

  6. Graphenea SA, 20018 Donostia-San Sebastián, Spain

    A. Centeno, A. Pesquera & A. Zurutuza Elorza

Authors
  1. K. J. Tielrooij
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  7. M. Bonn
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  9. F. H. L. Koppens
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Contributions

K.J.T., F.H.L.K. and M.B. conceived the experiment; K.J.T. and S.A.J. performed the experiment; K.J.T., J.C.W.S., L.S.L. and F.H.L.K. analysed and interpreted the data; J.C.W.S. and L.S.L. developed the theoretical model; A.C., A.P. and A.Z.E. prepared the sample; K.J.T., J.C.W.S., S.A.J., M.B., L.S.L. and F.H.L.K. wrote the paper.

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Correspondence to K. J. Tielrooij or F. H. L. Koppens.

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The authors declare no competing financial interests.

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Tielrooij, K., Song, J., Jensen, S. et al. Photoexcitation cascade and multiple hot-carrier generation in graphene. Nature Phys 9, 248–252 (2013). https://doi.org/10.1038/nphys2564

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