Two-Color Sensor for Biomolecule Detection

In this paper we report on biomolecule detection based on a two-color amorphous silicon photosensor. The revealed biomolecules are DNA strands labeled with two fluorochromes (Alexa Fluor 350 or Cy5) with different spectral properties and the device is a p-i-n-i-p amorphous silicon/amorphous silicon carbide stacked structure, that is able to detect different spectral regions depending on the voltage applied to its electrodes. The device design has been optimized in order to maximize the spectral match between the sensor responses and the emission spectra of the fluorochromes. This optimization process has been carried out by means of a numerical device simulator, taking into account the optical and the electrical properties of the amorphous silicon materials. We found that the detection limit of DNA molecules labeled with Alexa Fluor 350 is 3 nmol/l, while a detection limit around 400 nmol/l has been measured for the Cy5 dye.