High-responsivity graphene/silicon-heterostructure waveguide photodetectors


Graphene-based photonic devices, such as ultrafast photodetectors, optical modulators and tunable surface plasmon polariton devices, have experienced rapid development in recent years1,2,3,4,5,6 because they benefit greatly from graphene's strong field-controlled optical response7,8. Here, we demonstrate a graphene/silicon-heterostructure photodiode formed by integrating graphene onto a silicon optical waveguide on a silicon-on-insulator (SOI) with a near to mid-infrared operational range. The waveguide enables absorption of evanescent light that propagates parallel to the graphene sheet, which results in a responsivity as high as 0.13 A W−1 at a 1.5 V bias for 2.75 µm light at room temperature. A photocurrent dependence on bias polarity was observed and attributed to two distinct mechanisms for optical absorption, that is, direct and indirect transitions in graphene at 1.55 µm and 2.75 µm, respectively. Our result demonstrates the use of in-plane absorption in a graphene-monolayer structure and the feasibility of exploiting indirect transitions in graphene/silicon-heterostructure waveguides for mid-infrared detection.

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Figure 1: Schematic of graphene/silicon-heterostructure waveguide photodetector.
Figure 2: Infrared performance of photoresponse.
Figure 3: Energy-band diagram of graphene/silicon-heterostructure waveguide photodetector.


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This work was supported by the Hong Kong Research Grants Council (RGC) research grants (Grant Nos CUHK1/CRF/12G, CUHK4179/10E, SEG-CUHK01, CUHK4165/12E and AoE/P-02/12), and the National Natural Science Foundation of China (NSFC)/RGC Joint Research Scheme (N_CUHK405/12). J.-B.X. thanks the NSFC for support, particularly via Grant Nos 60990314, 60928009 and 61229401. Z.Z.C. thanks for the Hong Kong RGC PhD Fellowship.

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X.W. conceived the project. X.W. and Z.C. contributed equally to conduction of the experiments. K.X. helped with the sample preparation. X.W. and Z.C. wrote the manuscript. J.-B.X. and H.K.T. supervised the project. All authors discussed the results and commented on the paper.

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Correspondence to Xiaomu Wang or Hon Ki Tsang or Jian-Bin Xu.

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The authors declare no competing financial interests.

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Wang, X., Cheng, Z., Xu, K. et al. High-responsivity graphene/silicon-heterostructure waveguide photodetectors. Nature Photon 7, 888–891 (2013). https://doi.org/10.1038/nphoton.2013.241

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