▎ 摘　　要

We demonstrate a high-speed chemical vapor deposited graphene-on-silicon nitride waveguide photodetector. The device is designed with grating-like metal contact to reduce the channel spacing. Benefiting from the narrow channel spacing, a calculated transit-time-limited bandwidth of 111 GHz is derived. The resistance-capacitance-limited bandwidth is also improved due to the small relative permittivity of silicon nitride. At a wavelength of 1550 nm, we measured an electro-optic bandwidth of 38 GHz under zero bias and an intrinsic responsivity of 13 mA W-1 at 0.1 V reverse bias with a 6 m detection length.