Sensitive and Broadband Wavelength Sensor Based on Two Graphene/Si/Graphene Heterojunctions

High-precision spectral detection and broadband wavelength sensors have attracted considerable interest for important application in color image sensing. Due to the absorption limitations of silicon, conventional complementary metal-oxide-semiconductors have a relatively limited wavelength region from the ultraviolet to near-infrared spectrum. Here, a simple-structured device is developed by assembling two back-to-back monolayer graphene (MLG)/Si/MLG heterojunctions for high-resolution wavelength sensing applications. The single MLG/Si/MLG photodetector exhibits a responsivity of 0.18 A W-1, a specific detectivity of 1.36 x 10(9) Jones, and an external quantum efficiency of 28.5%. Thanks to the unique device geometry, the distribution of photo-generation rates in the two photodetectors is completely different, which brings about different photoelectric properties. It is found that the relationship between the photocurrent ratio of both photodetectors and the light wavelength can be fitted by a monotonic function, according to which the wavelength of incident light in the range from 260 to 1050 nm can be accurately estimated. A high resolution of 1 nm is demonstrated across a broadband wavelength from 260 to 1000 nm. This good resolution, along with good repeatability and stability, endow the present device with potential promise in future spectral sensing applications.