Abstract
We demonstrated a middle-wavelength infrared (MWIR) graphene photodetector using the photogating effect. This effect was induced by photosensitizers situated around a graphene channel that coupled incident light and generated a large electrical charge. The graphene-based MWIR photodetector consisted of a top graphene channel, source–drain electrodes, an insulator layer, and a photosensitizer, and its photoresponse characteristics were determined by current measurements. Irradiation of the graphene channel of the vacuum cooled device by an MWIR laser generated a clear photoresponse, as evidenced by modulation of the output current during irradiation. The MWIR photoresponse with the photogating effect was 100 times greater than that obtained from conventional graphene photodetectors without the photogating effect. The device maintained its MWIR photoresponse at temperatures up to 150 K. The effect of the graphene channel size on the responsivity was evaluated to assess the feasibility of reducing the photodetector area, and decreasing the channel area from 100 to 25 μm2 improved the responsivity from 61.7 to 321.0 AW − 1. The results obtained in our study will contribute to the development of high-performance graphene-based IR imaging sensors.
Highlights
Infrared (IR) imaging has been employed in a wide range of applications.[1]
The 3- to 5-μm spectral band corresponding to the middle-wavelength IR (MWIR) region is especially important with regard to IR imaging, because this band is associated with commonly encountered temperatures
The results indicate that the MWIR photoresponse was affected by the shape of the graphene channel but not by the irradiated area or the total incident light power
Summary
Infrared (IR) imaging has been employed in a wide range of applications.[1]. The 3- to 5-μm spectral band corresponding to the middle-wavelength IR (MWIR) region is especially important with regard to IR imaging, because this band is associated with commonly encountered temperatures. There is a demand for low-cost, nontoxic, high-responsivity photomaterials so as to obtain the advantages of both types of IR photodetectors Such materials would expand the range of applications of these devices. Broadband light absorption,[5,6,7] a rapid response,[8,9,10,11,12] gate-tunable plasmons,[13,14] and a strong nonlinear optical response.[15,16,17] In addition, graphene can be obtained at low cost through a nontoxic synthetic route, unlike quantum photomaterials.[18,19,20] graphene photodetectors are expected to expand the range of IR applications due to these advantages. We have previously investigated various techniques for this purpose, including the use of p–n junctions,[25] plasmonic metamaterial absorbers,[26,27,28] and the photogating effect.[29,30,31,32,33,34] Here, we report a detailed mechanism for the photogating effect that significantly improves the responsivity of graphene photodetectors operating in the MWIR spectral band
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