PIN-photodiode based active pixel in 0.35 μm high-voltage CMOS for optical coherence tomography

This paper presents an active pixel based on a PIN photodiode for application in Optical Coherence Tomography (OCT), where a high responsivity and low crosstalk is required. The proposed pixel is built on a wafer with a high-resistivity epitaxial silicon layer and optimized for high efficiency at 850 nm, low dark current, low crosstalk, and low noise operation. Advantages of this approach over conventional approaches such as the 3T active pixel in a standard CMOS process and over 4T pinned photodiode active pixel approaches for OCT applications are explained. A test chip was fabricated in 0.35 μm high-voltage CMOS. Three different epitaxial layer thicknesses are investigated. Measured results of the OCT PIN-photodiode pixel are presented.