In summary we reported photo-thermoelectric GPDs integrated on Si microring resonators By tuning the SLG coverage on top of the resonator we optimised the round-trip propagation losses inside the cavi

In this study, we have presented the development of photo-thermoelectric graphene photodetectors (GPDs) integrated on silicon microring resonators. By fine-tuning the coverage of single-layer graphene (SLG) on top of the resonator, we were able to optimize the round-trip propagation losses within the cavity to achieve critical coupling. As a result, we were able to achieve more than 90% light absorption in a compact length of approximately 6 μm SLG. This absorption led to carrier heating, which enabled high peak thermoelectric power (Te) of approximately 400 K in the GPDs. Additionally, by encapsulating the SLG channel in hexagonal boron nitride (hBN), we were able to obtain high mobility of over 10^4 cm^2/Vs. These combined factors allowed us to achieve a high responsivity of approximately 90 V/W. Our bias-free, Johnson-noise limited GPDs, which have voltage output, offer a more power-efficient alternative to commercial photodetectors currently used in optical interconnects. Moreover, the hot-carrier effects observed in SLG can potentially be leveraged for receiver architectures where current-to-voltage conversion, which is typically performed by transimpedance amplifiers, can be bypassed, thereby reducing the energy-per-bit cost and system footprint