High sensitivity, fast response time and strong light absorption are the most important metrics for infrared sensing and imaging. The trade-off between these characteristics remains the primary challenge in bolometry. Graphene with its unique combination of a record small electronic heat capacity and a weak electron–phonon coupling has emerged as a sensitive bolometric medium that allows for high intrinsic bandwidths1–3. Moreover, the material’s light absorption can be enhanced to near unity by integration into photonic structures. Here, we introduce an integrated hot-electron bolometer based on Johnson noise readout of electrons in ultra-clean hexagonal-boron-nitride-encapsulated graphene, which is critically coupled to incident radiation through a photonic nanocavity with Q = 900. The device operates at telecom wavelengths and shows an enhanced bolometric response at charge neutrality. At 5 K, we obtain a noise equivalent power of about 10 pW Hz–1/2, a record fast thermal relaxation time, <35 ps, and an improved light absorption. However the device can operate even above 300 K with reduced sensitivity. We work out the performance mechanisms and limits of the graphene bolometer and give important insights towards the potential development of practical applications.
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We thank L. Levitov, D. Prober, P. Kim and F. Koppens for fruitful discussions. D.K.E. acknowledges support from the Ministry of Economy and Competitiveness of Spain through the Severo Ochoa programme for Centres of Excellence in R&D (SEV-2015-0522), Fundació Privada Cellex, Fundació Privada Mir-Puig, the Generalitat de Catalunya through the CERCA program and the La Caixa Foundation. D.E. acknowledges support from the Office of Naval Research under grant no. N00014-14-1-0349. Y.G., C.T. and J.H. acknowledge support from the US Office of Naval Research, grant N00014-13-1-0662. K.C.F. acknowledges support from Raytheon BBN Technologies. B.S. was supported as part of the MIT Center for Excitonics, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0001088. J.Z. carried out research in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the US Department of Energy, Office of Basic Energy Sciences, under contract no. DE-SC0012704. This work is supported in part by the Semiconductor Research Corporation’s NRI Center for Institute for Nanoelectronics Discovery and Exploration (INDEX).
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Nature Materials (2018)