Amorphous silicon based p–i–i–n photodetector detects 12 nm thin protein layers

Various applications of photodetectors in bioanalytics, medicine and pharmaceutical research ask for low-cost, disposable sensor systems. Amorphous silicon (a-Si) based thin film photodetectors offer the unique chance of direct low-temperature deposition on plastic substrates, and of a precise application-specific tailoring of their optical properties and spectral sensitivity. Here we report on the first steps of developing integrated thin film detectors for a label-free point-of-care testing (POCT) in a university hospital. Key features are the dynamic adjustment of the spectral response of a p–i–i–n photodiode by a variable read-out voltage, and the monolithic integration of the a-Si based detector into the reflectometric interference spectroscopy (RIfS) setup. This contribution presents the first successful detection of the growth of 12 nm thin protein layers with these detectors. Experimental and modeling results of the a-Si based p–i–i–n photodetectors show good agreement.