Titanium-nitride localized-plasmon hot-electron photodetector covering the entire optical-communication band

Wide-spectrum photodetectors play a crucial role in applications such as communication, environmental monitoring, and infrared imaging. However, conventional semiconductor-based photodetectors suffer from intrinsic bandgap limitations, restricting the detectable spectral range. Hot-electron photodetectors (HE-PDs) based on plasmon-induced hot-electron transfer (PHET) offer an alternative approach, enabling sub-bandgap photodetection. Among plasmonic materials, transition metal nitrides such as titanium nitride (TiN) exhibit superior hot-carrier generation efficiency, thermal stability, and strong plasmonic absorption. In this study, we propose a HE-PD featuring conformal TiN/ZnO/TiN gratings, which enhance hot-carrier generation and collection efficiency compared to planar semiconductor structures. By employing a wide-bandgap semiconductor (ZnO), the Schottky barrier height is reduced to 0.3 eV, improving photoresponsivity and extending the detectable wavelength range into the optical-communication band. Optimized grating geometry enables nearly 100% absorption at 1550 nm, and electrical simulations predict a responsivity of 230 nA mW^-1 at 1200 nm, significantly outperforming Au-based counterparts. This work advances the development of high-performance HE-PDs, addressing the limitations of conventional photodetectors in spectral range and thermal stability.