Optical properties of hybrid plasmonic structure on silicon using transparent conducting-silver nanoparticles-silicon dioxide layers: the role of conducting oxide layer thickness in antireflection

The hybrid plasmonic antireflection layer (HPAL) consisting of silver nanoparticles (Ag NPs) sandwiched between indium tin oxide (ITO) and silicon dioxide (SiO2) thin layers is investigated for enhancing light absorption within a silicon wafer. The optimization of HPAL for minimizing reflection losses from silicon is carried out by tuning the ITO layer thickness, which also affects Ag NP morphology during the growth process. Light reflectivity of similar to 10% is observed from the silicon integrated with HPAL in the 300-1100 nm spectral region, due to enhanced light forward scattering as compared to a reflectivity of 26% from the bare silicon wafer. We have also investigated the ITO-SiO2 double layer (without Ag NPs) effect in reflection reduction from the silicon, but the HPAL performed better in Ag NPs' surface plasmon resonance (<600 nm) and off-resonance (900-1100 nm) wavelength regions as compared to the double layer. With the Ag NPs, the ITO layer thickness can be reduced from 70 nm to 30 nm for the maximum reflectance reduction from the silicon surface. The thin SiO2 capping layer on Ag NPs provides a better refractive index match for further reflectance reduction, and also acts as a protective layer from degradation of Ag NPs with time.