PIN photodiode-based active pixel for a near-infrared imaging application in 0.35-μm CMOS

We present an active pixel for a spectral domain optical coherence tomography sensor on a chip, where optical components are realized in a photonic layer and monolithically integrated with the electronics, whereby light is brought to the pixels using waveguides. The core of the pixel is an amplifier with capacitive feedback (so-called capacitive transimpedance amplifier), apart from that, a correlated double sampling circuit is implemented within the pixel. The proposed active pixel is based on a PIN photodiode and fabricated in 0.35-μm high-voltage CMOS technology. We use three different epitaxial starting material thicknesses (20, 30, and 40 μm) in order to find the device with best performance. The pixel is optimized for high efficiency in a spectral range between 800 and 900 nm. We explain advantages in the spectral responsivity and crosstalk of this pixel over conventional p / n photodiode-based pixels in standard CMOS processes and over the pinned photodiode-based pixel. We also present measured pixel parameters and give comparison with prior work.