Sufficiently large depletion region for photocarrier generation and separation is a key factor for two-dimensional material optoelectronic devices, but only a few device configurations have been explored for a deterministic control over the space charge region area in graphene with convincing scalability. Here we investigate a graphene-silicon p-i-n photodiode defined in a foundry processed planar photonic crystal waveguide structure, achieving visible—near-infrared, zero-bias, and ultrafast photodetection. Graphene is electrically contacting to the wide intrinsic region of silicon and extended to the p an n doped region, functioning as the primary photocarrier conducting channel for electronic gain. Graphene significantly improves the device speed through ultrafast out-of-plane interfacial carrier transfer and the following in-plane built-in electric field assisted carrier collection. More than 50 dB converted signal-to-noise ratio at 40 GHz has been demonstrated under zero bias voltage, the quantum efficiency could be further amplified by hot carrier gain on graphene-i Si interface and avalanche process on graphene-doped Si interface. With the device architecture fully defined by nanomanufactured substrate, this work demonstrates post-fabrication-free two-dimensional material active silicon photonic devices.
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The authors are grateful to A. van der Zande, C. Forsythe and F. Zhao for assistance. The authors acknowledge discussions with A. Soman, T. Kananen, T. Heinz, Y. Li, P. Kim, N. Li, J. C. Campbell, C. Santori, R. Beausoleil, T. Otsuji, and V. Ryzhii. T.L. and T.G. were supported by an Early Career Faculty grant from NASA’s Space Technology Research Grants Program (80NSSC17K0526). D.M. acknowledges support from AFOSR (FA9550-18-1-0300). H.H. acknowledges the support from DNRF Research Centre of Excellence, SPOC (DNRF-123), and Y.D. acknowledges Danish Council for Independent Research (DFF-1337-00152 and DFF-1335-00771). The authors acknowledge support from the National Science Foundation with grants DGE-1069240 (IGERT Optics and Quantum Electronics) and CBET-1438147.
© 2018, The Author(s).