Investigation of the spatial resolution of the light-addressable potentiometric sensor

The spatial resolution of the light-addressable potentiometric sensor (LAPS) is investigated both theoretically and experimentally. For a theoretical analysis, the diffusion equation for minority charge carriers in the semiconductor was solved. The results suggest that by thinning the semiconductor wafer, the spatial resolution of the LAPS is no longer limited by thr bulk minority charge carrier diffusion length. Spatial resolution in the micrometer range should thus be possible. For an experimental analysis, the effective diffusion length of light-generated charge carriers parallel to the sensor surface was measured. The results show that by increasing the doping density and by thinning the semiconductor substrate, spatial resolution of about 15 mum is obtained. (C) 2000 Elsevier Science B.V. All rights reserved.