A New Generation of SPAD—Single-Photon Avalanche Diodes

Design and characterization of a new generation of single-photon avalanche diodes (SPAD) array, manufactured by ST-Microelectronics in Catania, Italy, are presented. Device performances, investigated in several experimental conditions and here reported, demonstrate their suitability in many applications. SPADs are thin p-n junctions operating above the breakdown condition in Geiger mode at low voltage. In this regime a single charged carrier injected into the depleted layer can trigger a self-sustaining avalanche, originating a detectable signal. Dark counting rate at room temperature is down to 10 s^-1 for devices with an active area of 10 mum in diameter, and 10³ s^-1 for those 50 mum wide. SPAD quantum efficiency, measured in the range 350-1050 nm, can be comparable to that of a typical silicon based detector and reaches the values of about 50% at 550 nm. Finally, the low production costs and the integration possibility are other favorable features in sight of highly dense integrated 1-D or 2-D arrays.