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

TL;DR

This paper presents ultrafast, zero-bias graphene photodetectors integrated on passive photonic waveguides, leveraging a polymeric dielectric to enhance the photothermoelectric effect, achieving high-speed operation without dark current.

Contribution

The authors demonstrate a scalable, high-performance graphene photodetector utilizing a polymeric dielectric to generate a controllable p-n junction, operating at 67 GHz without roll-off and without nanoscale plasmonic structures.

Findings

Operates at 67 GHz frequency response

Zero dark current in graphene photodetectors

Enhanced PTE effect with low charge inhomogeneity

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 x 10$^{10}$ $cm^{-2}$ at the charge neutrality point, and a large Seebeck coefficient 140 ${\mu}$V 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.