A CMOS-based phototransistor for high-sensitivity biochemical detection using absorption photometry

This paper proposes a high-sensitivity biosensing system on the basis of absorption photometry and a phototransistor. Manufactured in a standard 0.35-mum CMOS technology, the phototransistor exhibits a responsivity higher than 1000 A/W for 650-nm light. The TMB/H₂O₂/HRP method is chosen as a useful platform to determine the amount of various interesting targets. For the biochemical detection, a sample volume of only 10 mul is required to be dropped on the slide above the phototransistor. Experimental results demonstrate that a high sensitivity of 2.5 muA/pM is achieved, and the minimum HRP concentration successfully detected is 2.7 pM. This detection limit is three orders of magnitude better than that of a reported silicon biosensor.