Near-infrared (NIR) photodetectors have interesting roles in optical fiber communications and biomedical applications. Conventional NIR photodetectors have been realized using InGaAs and Ge, of which the cut-off wavelengths exceed 1500 nm. Si-based photodetectors exhibit limited external quantum efficiency at wavelengths longer than 1000 nm. By synthesizing a CuInSe2 compound on a glass substrate, photodetectors that can detect optical wavelengths longer than 1100 nm have been realized in this study. The bandgap energies of the CuInSe2 thin films were tuned by varying the Cu/In ratio from 1.02 to 0.87. The longest cut-off wavelength (1309 nm) was obtained from a CuInSe2 thin film having a Cu/In ratio of 0.87. The responsivity of the photodiode was measured under the illumination of a 1064 nm laser light. The photo responses exhibited linear response up to 2.33 mW optical illumination and a responsivity of 0.60 A/W at −0.4 V.
CuInSe2-Based Near-Infrared Photodetector