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 STMicroelectronics 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 µm in diameter, and 1000 s-1 for those of 50 µm. 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 for bigger samples. Finally, the low production costs and the possibility of integrating are other favorable features in sight of highly dense integrated 1-D or 2-D arrays.