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 semico
nductor 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 microme
ter range should thus be possible. For an experimental analysis, the effect
ive diffusion length of light-generated charge carriers parallel to the sen
sor surface was measured. The results show that by increasing the doping de
nsity and by thinning the semiconductor substrate, spatial resolution of ab
out 15 mum is obtained. (C) 2000 Elsevier Science B.V. All rights reserved.