Fluorine- and nitrogen-co-doped carbon dots for enhanced photoresponsivity in silicon photodetectors

Silicon (Si) photodetectors are of great importance due to their many scientific and industrial applications, including optical interconnects, spectroscopy, optical communications, and semiconductor device processing. However, the responsivity of Si photodetectors drops sharply at shorter wavelengths due to their high light absorption coefficient and increased reflectivity in this range. In this report, a hybrid Si photodetector architecture is demonstrated by integrating an ultrathin fluorine- and nitrogen-co-doped carbon quantum dots (fnCQDs) layer using a facile fabrication technique. The results show that the hybrid device achieves a broadband photoresponse. The optimized incorporation of fnCQDs enhances the short-wavelength range responsivity between 300 nm and 550 nm, while simultaneously maintaining nearly identical fast rise times at the peak as the conventional bare Si device under 0 V working voltage. Moreover, the photoresponsivity and gain of the engineered optimal device are found to be approximately 0.012 A/W and 328, respectively, at a wavelength of 365 nm. Additionally, the maximum photocurrent-to-dark current ratio (@365 nm) of this hybrid device under a 0.01 V bias reaches approximately 6200, nearly six times greater than that of the standard reference device. The proposed approach and findings demonstrate the significant potential of fnCQDs for applications in hybrid photodetectors and related technologies.