Multilayer Plasmonic Structure-Enhanced Near-Infrared CoSi₂/Si Schottky Photodetector via Standard CMOS Process

Imaging sensing based on silicon optoelectronic chips faces significant challenges in extending the detection range to the near-infrared (NIR) band. In this paper, we demonstrate near-infrared CoSi2/Si Schottky diodes as photodetectors in the CMOS process. To enhance photoabsorption and broaden the spectral range for detection, the CoSi2/Si Schottky diode is integrated with a fishbone-shaped Al/W/CoSi2 multilayer structure, which provides a strong surface plasmon resonance (SPR) effect. Experimental results show that, under a bias voltage of −1 V and NIR irradiation, the device enables a maximum responsivity of 1.7 mA/W @ 1550 nm and 0.1 mA/W @ 2000 nm. The rise and fall times for a 1550 nm pulse source are 16.3 and 15.8 ms, respectively. Both photoelectric and photothermal responses are observed in photodetectors, with the photothermal effect contributing more significantly at longer wavelengths. The mechanisms of these two effects and the optimization directions for long-wavelength detection are discussed. This work overcomes the spectral limitations of conventional CMOS imaging sensors, providing a low-cost, scalable solution for high-performance NIR imaging applications.