MoS2 photodetectors integrated with photonic circuits

In recent years, two-dimensional materials have risen as an attractive platform for integrated optoelectronics, due to their atomic scale thickness, favorable electrical, mechanical, and optical properties. In particular, graphene has been exploited as an ultrafast light modulator and photodetector, operating at telecommunication wavelengths. However, materials with larger bandgaps are required for light detection in the visible range of the spectrum, with wide applications in space communication, industrial quality controls, light sensing, etc. Even though TMDC-based light emitting and detecting devices in the visible spectrum have already been realized, efficient light absorption and photocurrent generation on integrated devices has not been achieved yet. Here, we demonstrate the integration of an ultrasensitive MoS2 photodetector with a silicon nitride photonic circuit. In contrast to the limited vertical light absorption, we observe near-unity lateral absorption, which results in even higher responsivity. By fabricating an alternative device where the MoS2 semiconducting channel is combined with a hexagonal boron nitride (h-BN) substrate, we significantly improve the speed of the photodetector. Low power operation is further achieved in a third device with graphene local gates. These results pave the way for future TMDC-based integrated optoelectronic devices.