Dependence of light-addressable potentiometric sensor sensitivity on photo-induced processes in Si

The effect of photoelectron processes in n-Si and p-Si during the fabrication of the "Si/SiO₂/SiN_x/polyethyleneimine/glucose oxidase" sensor structure on the glucose sensitivity of a light-addressable potentiometric sensor (LAPS) depending on SiN_x thickness was investigated. It was found that the illumination of the n-Si-based structure during the adsorption of the glucose oxidase enzyme doubles the sensitivity to glucose compared to the adsorption of
glucose oxidase in the dark, and the best effect from photostimulated adsorption is achieved at a SiN_x layer thickness of ~ 50 nm. At the same time, the sensitivity to D-glucose, measured in the LAPS mode, is 45% higher than the sensitivity of the capacitive sensor. Illumination of p-Si during glucose oxidase adsorption resulted in a slight decrease in sensor sensitivity. The results are explained by a change in the density of immobilized glucose oxidase molecules due to a change in the electrostatic forces of attraction between enzyme molecules and semiconductor upon illumination and photoinduced charge stabilization on the surface electronic states of the Si/SiO₂ and SiN_x/polyethyleneimine interfaces in the case of photostimulated glucose oxidase adsorption.