Nanostructured black TiN for enhanced photodetection under broadband visible illumination

Titanium nitride (TiN) combines metallic optical behavior, thermal stability, and CMOS compatibility, positioning it as a compelling material for next-generation optoelectronics. We demonstrate visible-range broadband photodetectors based on nanostructured black TiN manufactured by using an optimized deposition combined with a simple wet-etching process that allows strong light trapping and low reflectivity (4–15% over 200–900 nm). Under fast 5 V modulation, the black TiN devices exhibit a photocurrent swing nearly twice that of flat TiN, increasing from 55 to 115 μA. This enhancement may be associated with plasmon-induced hot-carrier effects. Under slow 0.5 V illumination, the increase is more modest (22–33 μA), indicating that the plasmonic enhancement strongly depends on the excitation dynamics. Quantitative analysis yields ON/OFF ratios close to unity (∼1), responsivities in the range of 10−4–10−3 A/W, and detectivities up to ∼3×105 Jones. These results indicate that performance enhancement in black TiN is influenced by excitation conditions and carrier dynamics rather than solely by static absorption, establishing black TiN as a scalable platform for visible-range broadband photodetection and optical sensing.