Kanika Chauhan, Ankit Pandey
Infrared photodetectors have numerous applications in optical communication, thermal imaging, biomedical sensing, and the defense sector. However, efficient light absorption and its conversion into detectable current are key challenges for the researchers working in this area. This work presents enhanced absorption in a TiN grating-assisted structure, providing promising performance as a TiN/Ge Schottky photodetector. Titanium nitride (TiN) has been deemed an active material of choice due to its exceptional plasmonic properties as well as excellent thermal stability and CMOS compatibility. The proposed structure consists of a one-dimensional TiN plasmonic grating integrated with germanium (Ge) on silicon, forming a suitable platform for a TiN/Ge Schottky photodetector. Rigorous coupled-wave analysis (RCWA) is systematically carried out to investigate and optimize the optical response of the grating-assisted structure. The optimized grating exhibits a peak absorption of 89% at a wavelength of 1.3µm for transverse magnetic (TM) polarized illumination, due to strong electromagnetic field confinement and enhanced light trapping at the metal–semiconductor interface, while transverse electric (TE) polarization does not produce notable absorption enhancement when compared to a planar structure without a grating. This polarization-dependent response with one-dimensional periodic gratings confirms the existence of the plasmonic modes, which enables efficient excitation of surface plasmon resonance under transverse magnetic (TM) polarization. Furthermore, the performance of the TiN/Ge structure has been investigated as a Schottky photodetector using Fowler’s internal photoemission model, yielding a peak responsivity of 7.56 mA/W with a low value of dark current of 2.74×10 −10 A. These results demonstrate that plasmonic TiN grating-assisted absorption enhancement can be effectively harnessed to realize CMOS compatibility, providing efficient capability in near-infrared photodetectors.