Ultrasensitive graphene position-sensitive detector induced by synergistic effects of charge injection and interfacial gating

Position-sensitive detectors (PSDs) are essential components to the realization of displacement and vibration detection, optical remote control, robot vision, etc. The light sensitivity of PSDs is a crucial parameter, which determines the operating range or detection accuracy of the measurement systems. Here, we devise an ultrasensitive PSD based on graphene/Si hybrid structure by using the synergistic effect of charge injection and interfacial gating. Photogenerated carriers in Si are separated by the built-in electric field at the surface. Holes diffuse laterally in inversion layer and then inject into graphene to form photoresponse. Meanwhile, the electrons in bulk Si that move to the area under graphene cause a gating effect, thus introducing a high gain. With the benefit of synergistic effect, the detection limit power of our device can be pushed to pW level, which is reduced by two orders of magnitude compared to previously reported graphene based PSD. Furthermore, even for infrared light of 1064 nm, the PSD still retains position sensitivity to 1 nW weak light, as well as fast response speed at the μs level. This work provides the potential of graphene as a promising material for ultraweak light position sensitive detection.