Surface plasmon resonance sensor with photodiode integrated beneath plasmonic layer

Surface plasmon resonance (SPR)-based sensors have demonstrated exceptional sensitivity in detecting changes in the refractive index (RI) occurring near the sensor surface due to variations in concentration within the medium, chemical reactions, analyte binding with its ligand, and similar factors. However, most conventional SPR sensors rely on an external photodiode system and a complex mechanical system to measure changes in both intensity and position of reflected light. This is the main limitation of typical SPR sensors, making them non-portable and challenging to apply in experiments beyond the laboratory. Here, we propose SPR sensor chips integrated with a photodiode that eliminates the disadvantage of conventional SPR sensors. The photodiode is based on an n-type Silicon (nSi)-intrinsic Silicon (iSi) junction, sandwiched between a transparent conductive oxide layer, specifically Indium Tin Oxide (ITO), and a plasmonic material, namely Gold (Au). The working principle of our photodiode-integrated SPR sensors was revealed, and the impact of nSi and iSi film thicknesses on sensor sensitivity was investigated. Our SPR sensors enhance the efficiency of SPR-based sensors across diverse applications and facilitate integration into completed electronic devices.