Design and characterization of a monolithic CMOS phase-sensitive pixel based on an avalanche photodiode

In this paper we propose a phase-sensitive pixel concept based on an avalanche photodiode (APD) with a charge sensitive amplifier (CSA) readout circuit, and its implementation in a standard CMOS technology. We exploit the principle of APD gain modulation to realize the functions of optical sensing and demodulation of light signals in one component, which can be exploited in several application domains, such as contactless Time-of-Flight distance measurement and fluorescence lifetime detection. A pixel containing an APD with 100-μm active area diameter and a CSA was designed and fabricated in a 0.35 μm standard CMOS technology. The pixel phase detection capability was validated by simulations and experimental results. The results of this work represent a good background for the fabrication of a phase-sensitive pixel array based on APDs.