Single Photon Avalanche Diodes (SPADs) are solid-state devices capable of detecting a single photon by exploiting junction breakdown in semiconductor materials. The combination of excellent performance in terms of photon detection efficiency, noise, active area diameter and temporal response provided by these detectors, makes them suitable for a wide range of applications including quantum communications. In addition, they present all the advantages that are typical of the semiconductor devices, i.e. ruggedness, compactness and suitability for the integration on the same chip of many devices and of part of the front-end electronics. Finally, they are usually operated at room temperature or moderately cooled by means of a Peltier stage with great advantages in terms of easiness of operation and reduced system costs.
In this talk we will discuss the principle of operation, the performance and the limitations of SPAD detectors. Then we will present results recently obtained at our laboratories along with prospects of future developments.