Ultrafast, Zero-Bias, Graphene Photodetectors with Polymeric Gate Dielectric on Passive Photonic Waveguides

Abstract

We report compact, scalable, high-performance, waveguide integrated graphene-based photodetectors (GPDs) for telecom and datacom applications, not affected by dark current. To exploit the photothermoelectric (PTE) effect, our devices rely on a graphene/polymer/graphene stack with static top split gates. The polymeric dielectric, poly(vinyl alcohol) (PVA), allows us to preserve graphene quality and to generate a controllable p−n junction. Both graphene layers are fabricated using aligned single-crystal graphene arrays grown by chemical vapor deposition. The use of PVA yields a low charge inhomogeneity ∼8 × 10 10 cm −2 at the charge neutrality point, and a large Seebeck coefficient ∼140 μV K −1 , enhancing the PTE effect. Our devices are the fastest GPDs operating with zero dark current, showing a flat frequency response up to 67 GHz without roll-off. This performance is achieved on a passive, low-cost, photonic platform, and does not rely on nanoscale plasmonic structures. This, combined with scalability and ease of integration, makes our GPDs a promising building block for next-generation optical communication devices.

Photo thermal effect graphene detector featuring 105 Gbit s−1 NRZ and 120 Gbit s−1 PAM4 direct detection

“…The spectra are completely flat in the range of frequencies of the input electrical signal as generated at the transmitter side without any ripples or a drop at high frequencies. This demonstrates the high speed of operation of our detectors, as already demonstrated for a similar device in our previous work where we showed flat response up to 40 GHz 54 , 55 . The response shown in Fig.…”

“…We designed a waveguide integrated PTE photodetector based on a split-gate geometry similar to the one used in a previous work 54 , 55 (Fig. 1 ).…”

“…In refs. 54 , 55 we demonstrated the high speed of operation the PTE detector integrated on a SiN waveguide (core cross-section 1200 nm × 260 nm) using poly-vinyl alcohol (PVA) as gate dielectric. The use of PVA allowed to preserve the good quality of graphene after polymer deposition but, at the same time, posed severe limitations: large hysteresis of graphene field effect curves 56 , contact resistance larger than 5000 Ω µm, and lithographic limitations as discussed in ref.…”

“…The use of PVA allowed to preserve the good quality of graphene after polymer deposition but, at the same time, posed severe limitations: large hysteresis of graphene field effect curves 56 , contact resistance larger than 5000 Ω µm, and lithographic limitations as discussed in ref. 54 . In this work, we moved to the SOI platform to exploit the steeper mode profile of the Si waveguides, which is due to the higher index contrast with respect to SiN.…”

Finite Element Modelling of Bandgap Engineered Graphene FET with the Application in Sensing Methanethiol Biomarker

“…Using the above techniques, not only do we induce a gap in the band structure of the graphene, but we are able to tune the gap. Graphene has potential for many applications, such as graphene field effect transistor (GFET) [ 20 , 21 , 22 , 23 , 24 ], photonic devices such as photodetectors [ 25 , 26 , 27 , 28 , 29 , 30 ], phototransistors [ 31 , 32 , 33 ], and mode-locked lasers [ 34 ].…”