Dual-Color Photodetection Based On Speed-Differentiated Photoresponse With High Photogain

Dual-color photodetection can increase detection accuracy due to the specific information from different wavelengths. Traditional dual-color detectors are based on double optical modules or photovoltage devices, which suffer from huge system weight or low gain. In this Letter, a novel dual-color photodetector with Ge/Graphene/CdS sandwich profile is proposed. While visible and infrared light is mainly absorbed by the CdS and Ge layers, respectively, photoelectrical signals from two wavelengths both conducted by graphene are extracted on time-sequence with different sampling frequencies. Based on a tailored interface process and epitaxy InGaAs instead of bulk Ge layer, the difference in response speed more than 3 orders of magnitude (76 kHz/14 Hz) was realized. Due to the photogating effect, the high gain was obtained for both wavelengths, and a photoresponse enhancement originated from the overlapping of local photogating field is observed. The device provided a new solution for high-gain and CMOS-compatible dual-color photodetection.