Abstract
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.
Highlights
Nowadays, near-infrared (NIR) photodetectors which can convert optical signals to electrical signals are getting considerable interest for night-vision imaging, optical fiber communications, biomedical imaging, vegetation monitoring, and security applications due to the strong propagation and low attenuation characteristics of NIR light [1,2,3,4,5,6]
The bandgap energies of the CISe thin films were tuned by varying the Cu/In ratio
Region, a high-quality photodetector operating in the NIR region using low-bandgap CISe thin film must be realized
Summary
Near-infrared (NIR) photodetectors which can convert optical signals to electrical signals are getting considerable interest for night-vision imaging, optical fiber communications, biomedical imaging, vegetation monitoring, and security applications due to the strong propagation and low attenuation characteristics of NIR light [1,2,3,4,5,6]. InGaAs and Ge-based photodetectors with cut-off wavelengths exceeding. 1500 nm have been used for NIR photodetectors. Si-based photodetectors are challenging when used to detect the NIR wavelength range and show low external quantum efficiency due to their low cut-off wavelength of 1100 nm [7,8]. Ge-based photodetectors suffer from a high dark current (~10 mA/cm2 ) that is orders of magnitude higher than the ~0.5 μA/cm of InGaAs photodetectors. This leads to low signal-to-noise ratio (S/N). InGaAs-based photodetectors have issues related to expensive manufacturing processes [12,13]. Cu(In, Ga)Se2 (CIGS) thin films have become considered one of the most prominent candidates for NIR photoactive layers [14,15,16]
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