Hybrid graphene/InGaAs-based SWIR photodetectors

Graphene-based infrared (IR) photodetectors are promising devices that exploit the unique optoelectronic properties of graphene, such as its broadband light absorption, rapid response, and high chemical stability. However, graphene exhibits a low absorbance of 2.3%, which limits its photoresponsivity. We previously successfully enhanced the responsivity of graphene photodetectors for various wavelength regions such as the ultraviolet, visible, and middle-wavelength and long-wavelength IR regions, using the photogating effect. In this study, we applied this photogating effect to develop short-wavelength IR (SWIR) image sensors with InGaAs PIN photodiodes as photosensitizers. Graphene field-effect transistors (GFETs) with InGaAs photodiode photosensitizers were fabricated on an InP substrate. Under 1550-nm SWIR light irradiation in vacuum, the GFET device exhibited a distinct response with the highest responsivity value of 50.4 A/W, whereas the InGaAs PIN photodiode showed a responsivity value of 1.08 A·W−1. The observed current variations in the photosensitizers and substrate suggested that the photovoltage in the InGaAs PIN photodiode modulated the gate voltage on the GFET. Owing to the high FE carrier mobility of graphene, significant variations in current were detected, reflecting the photoresponse of the device. These findings are expected to contribute to the development of high-performance SWIR image sensors.