CMOS photodetector systems for low-level light applications

In this work, we have designed, fabricated and measured the performance of three different active pixel sensor (APS) structures. These APS structures are studied in the context of applications that require low-level light detection systems. The three APS structures studied were—a conventional APS, an APS with a comparator, and an APS with an integrator. A special focus of our study was on both the signal and noise characteristics of each APS structure so the key performance metric of signal-to-noise ratio can be computed and compared. The pixel structures that are introduced in this work can cover a wide range of applications, such as high resolution digital photography using the APS with a comparator, to ultra-sensitive biomedical measurements using the APS with an integrator.