Fast fully-integrated active quenching circuit driving an external SPAD up to 250Mcounts/s

Single Photon Avalanche Diodes (SPADs) are the enabling device for different kind of applications in which low noise, high photon detection efficiency, and compactness are required. They are capable of providing high photon count rate and picosecond timing precision. For these reasons, SPADs are the sensors of choice in many applications such as LiDAR, TCSPC and quantum key distribution (QKD). Whether the SPAD is implemented in a custom technology, allowing detector tailoring on specific application constraints, or in a CMOS process, with great benefits in terms of large-scale integration and compactness, a quenching circuit is always required, and it sets the ultimate performance that can be extracted from this sensor. In this work, we present a fully-integrated active quenching circuit capable of driving external custom SPADs up to 250 Mcps. The circuit has been fabricated exploiting a 150nm high voltage technology and extensively tested with a custom SPAD.