Dual-Schottky heteroepitaxial Nb:SrTiO3 /TiN/Si for highperformance broadband photodetection across UV-IR spectrum

Abstract

Broadband photodetectors with spectral response ranging from ultraviolet (UV) to infrared (IR) are of great significance for various applications. However, conventional silicon-based photodetectors exhibit low response efficiency in the UV region. Although heterojunction structures can extend the spectral response range through material synergy, they still face challenges such as poor stability and insufficient absorption efficiency. In this study, an Nb:SrTiO₃/TiN/Si heteroepitaxial structure was fabricated on a silicon substrate using pulsed laser deposition. The crystal structure, interface quality, and compositional distribution of the materials were characterized. The spectral response characteristics were evaluated using a photoelectric testing system. Experimental results demonstrate that the TiN buffer layer effectively reduces the lattice mismatch between Nb:SrTiO₃ and Si while enhancing interfacial charge transport through its metallic properties and localized surface plasmon resonance effect. The Nb:SrTiO₃/TiN/Si heterojunction achieves the responsivity values of 2.14 V/W, 1.34 V/W, and 4.1 V/W under 808 nm, 532 nm, and 365 nm illumination, respectively, significantly outperforming the TiN/Si structure. The dual-Schottky junction mechanism-where the Si/TiN junction dominates IR/visible response and the NbSTO/TiN junction facilitates UV carrier separation-enables balanced photodetection from UV to IR. Additionally, the photoconductive effect under 248 nm pulsed light confirms the broadband response capability of the heterostructure. This study not only provides a novel material design strategy for optimizing the performance of silicon-based photodetectors but also establishes an experimental foundation for developing high-performance broadband photodetectors.