Optimized CMOS photodetector structures for the detection of green luminescent probes in biological applications

Recent developments in lab-on-a-chip applications have increased the need for low-power, small-footprint photodetectors to detect luminescent reporters used to monitor biological events. Presented is a CMOS photodiode structure that is optimized to detect green light, the peak emission wavelength of commonly used fluorophores and other luminescent probes. The photodiode geometry uses a lightly doped striped cathode geometry to maximize the depletion region in areas of highest light absorbance, increasing the sensitivity to green light. The devices, realized in 1.5 m CMOS technology, have up to a 63% increased signal-to-noise response for green light compared to blue-enhanced CMOS photodiode structures. These devices also generate an output 4.5 times larger than conventional CMOS detectors for detecting fluorescent emissions from a 1 M fluorescein solution. The devices are designed to be integrated in total analysis systems which rely on the detection of fluorecent or phosphorescent reporters, and which are compact, low-power, and low-cost. © 2004 Elsevier B.V. All rights reserved.