Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Photoexcitation cascade and multiple hot-carrier generation in graphene

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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

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

References

  1. 1

    Nair, R. R. et al. Fine structure constant defines visual transparency of graphene. Science 320, 1308 (2008).

    ADS  Article  Google Scholar 

  2. 2

    Kotov, V. N. et al. Electron–electron interactions in graphene: Current status and perspectives. Rev. Mod. Phys. 84, 1067–1125 (2012).

    ADS  Article  Google Scholar 

  3. 3

    Bonaccorso, F., Sun, Z., Hasan, T. & Ferrari, A. C. Graphene photonics and optoelectronics. Nature Photon. 4, 611–622 (2010).

    ADS  Article  Google Scholar 

  4. 4

    Winzer, T., Knorr, A. & Malić, E. Carrier multiplication in graphene. Nano Lett. 10, 4839–4843 (2010).

    ADS  Article  Google Scholar 

  5. 5

    Winzer, T. & Malić, E. Impact of Auger processes on carrier dynamics in graphene. Phys. Rev. B 85, 241404 (2012).

    ADS  Article  Google Scholar 

  6. 6

    Gabor, N. M. et al. Hot carrier assisted intrinsic photoresponse in graphene. Science 334, 648–652 (2011).

    ADS  Article  Google Scholar 

  7. 7

    Song, J. C. W. et al. Hot carrier transport and photocurrent response in graphene. Nano Lett. 11, 4688–4692 (2011).

    ADS  Article  Google Scholar 

  8. 8

    Pijpers, J. J. H. et al. Assessment of carrier-multiplication efficiency in bulk PbSe and PbS. Nature Phys. 5, 811–814 (2009).

    ADS  Article  Google Scholar 

  9. 9

    Pijpers, J. J. H. et al. Carrier multiplication and its reduction by photodoping in colloidal InAs quantum dots. J. Phys. Chem. C 111, 4146–4152 (2007).

    Article  Google Scholar 

  10. 10

    Schaller, R. D. & Klimov, V. I. High efficiency carrier multiplication in PbSe nanocrystals: Implications for solar energy conversion. Phys. Rev. Lett. 92, 186601 (2004).

    ADS  Article  Google Scholar 

  11. 11

    Schaller, R. D., Agranovich, V. M. & Klimov, V. I. High-efficiency carrier multiplication through direct photogeneration of multi-excitons via virtual single–exciton states. Nature Phys. 1, 189–194 (2005).

    ADS  Article  Google Scholar 

  12. 12

    Ulbricht, R. et al. Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy. Rev. Mod. Phys. 83, 543–586 (2011).

    ADS  Article  Google Scholar 

  13. 13

    George, P. A. et al. Ultrafast optical-pump terahertz-probe spectroscopy of the carrier relaxation and recombination dynamics in epitaxial graphene. Nano Lett. 8, 4248–4251 (2008).

    ADS  Article  Google Scholar 

  14. 14

    Strait, J. H. et al. Very slow cooling dynamics of photoexcited carriers in graphene observed by optical-pump terahertz-probe spectroscopy. Nano Lett. 11, 4902–4906 (2011).

    ADS  Article  Google Scholar 

  15. 15

    Winnerl, S. et al. Carrier relaxation in epitaxial graphene photoexcited near the Dirac point. Phys. Rev. Lett. 107, 237401 (2011).

    ADS  Article  Google Scholar 

  16. 16

    Breusing, M., Ropers, C. & Elsaesser, T. Ultrafast carrier dynamics in graphite. Phys. Rev. Lett. 102, 086809 (2009).

    ADS  Article  Google Scholar 

  17. 17

    Breusing, M. et al. Ultrafast nonequilibrium carrier dynamics in a single graphene layer. Phys. Rev. B 83, 153410 (2011).

    ADS  Article  Google Scholar 

  18. 18

    Kampfrath, T. et al. Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite. Phys. Rev. Lett. 95, 187403 (2005).

    ADS  Article  Google Scholar 

  19. 19

    Hwang, H.Y. et al. Nonlinear THz conductivity dynamics in CVD-grown graphene. Preprint http://arxiv.org/abs/1101.4985 (2011).

  20. 20

    Frenzel, A. J. et al. Observation of suppressed THz absorption in photoexcited graphene. Preprint http://arxiv.org/abs/1301.6108 (2013).

  21. 21

    Nomura, K & MacDonald, A. H. Quantum Hall ferromagnetism in graphene. Phys. Rev. Lett. 96, 256602 (2006).

    ADS  Article  Google Scholar 

  22. 22

    Ando, T. Screening effect and impurity scattering in monolayer graphene. J. Phys. Soc. Jpn 75, 074716 (2006).

    ADS  Article  Google Scholar 

  23. 23

    Das Sarma, S. D., Adam, S., Hwang, E. H. & Rossi, E. Electronic transport in two-dimensional graphene. Rev. Mod. Phys. 83, 407–470 (2011).

    ADS  Article  Google Scholar 

  24. 24

    Song, J. C. W. et al. Photo-excited carrier dynamics and impact excitation cascade in graphene. Preprint http://arxiv.org/abs/1209.4346.

  25. 25

    Bistritzer, R. & MacDonald, A. H. Electronic cooling in graphene. Phys. Rev. Lett. 102, 206410 (2009).

    ADS  Article  Google Scholar 

  26. 26

    Tse, W-K. & Das Sarma, S. D. Energy relaxation of hot Dirac fermions in graphene. Phys. Rev. B 79, 235406 (2009).

    ADS  Article  Google Scholar 

  27. 27

    Song, J. C. W., Reizer, M. Y. & Levitov, L.S. Disorder-assisted electron phonon scattering and cooling pathways in graphene. Phys. Rev. Lett. 109, 106602 (2012).

    ADS  Article  Google Scholar 

  28. 28

    Foster, M. S. & Aleiner, I. L. Slow imbalance relaxation and thermoelectric transport in graphene. Phys. Rev. B 79, 085415 (2009).

    ADS  Article  Google Scholar 

Download references

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.

Author information

Affiliations

Authors

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.

Corresponding authors

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

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 444 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing