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Hybrid graphene–quantum dot phototransistors with ultrahigh gain

Abstract

Graphene is an attractive material for optoelectronics1 and photodetection applications2,3,4,5,6 because it offers a broad spectral bandwidth and fast response times. However, weak light absorption and the absence of a gain mechanism that can generate multiple charge carriers from one incident photon have limited the responsivity of graphene-based photodetectors to 10−2 A W−1. Here, we demonstrate a gain of 108 electrons per photon and a responsivity of 107 A W−1 in a hybrid photodetector that consists of monolayer or bilayer graphene covered with a thin film of colloidal quantum dots. Strong and tunable light absorption in the quantum-dot layer creates electric charges that are transferred to the graphene, where they recirculate many times due to the high charge mobility of graphene and long trapped-charge lifetimes in the quantum-dot layer. The device, with a specific detectivity of 7 × 1013 Jones, benefits from gate-tunable sensitivity and speed, spectral selectivity from the short-wavelength infrared to the visible, and compatibility with current circuit technologies.

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Figure 1: Hybrid graphene–quantum dot phototransistor.
Figure 2: Device physics.
Figure 3: Phototransistor device characteristics.

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Acknowledgements

This research was partially supported by Fundació Cellex Barcelona. G.K. acknowledges support from the EU FP7 IRG programme (contract no. PIRG06-GA-2009-256355). The authors thank K-J. Tielrooij for fruitful discussions.

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Authors

Contributions

G.K. and F.H.L.K. conceived and designed the experiments, led the research and wrote the paper. M.B. and L.G. contributed to device fabrication, performed the measurements and analysed the data. J.O. contributed to device fabrication. M.B. contributed to material synthesis. F.P.G.A. and F.G. contributed to device fabrication and measurements. All authors discussed the results and assisted in manuscript preparation.

Corresponding authors

Correspondence to Gerasimos Konstantatos or Frank H. L. Koppens.

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The authors declare no competing financial interests.

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Konstantatos, G., Badioli, M., Gaudreau, L. et al. Hybrid graphene–quantum dot phototransistors with ultrahigh gain. Nature Nanotech 7, 363–368 (2012). https://doi.org/10.1038/nnano.2012.60

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  • DOI: https://doi.org/10.1038/nnano.2012.60

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