An Open-Circuit Voltage Pixel for Low-Light Visible Imaging in a Standard CMOS Process

An imaging pixel unit-cell topology leveraging a photodiode in the forward-bias region is proposed for the visible and near-infrared spectral ranges. The open-circuit voltage pixel (VocP) architecture applied to visible imaging allows for improvement in the effective responsivity of the photodetector, leading to significant enhancement in pixel sensitivity across a wide spectral-range, while relaxing the requirements on the photodiode, and chosen CMOS process. Theoretical analysis is presented to show the operation, response, and performance benefits of the VocP. The pixel topology has been verified in simulation in a 0.13 μm standard CMOS technology, and has also been embedded in an end-to-end readout system model to show the projected performance compared against a conventional 4T-APS.