Dark Count in Single Photon Avalanche Si Detectors

We electrically and optically tested both single pixels and complete arrays of Silicon Photomultipliers, from 5x5 to 64x64, fabricated by STMicroelectronics. Single cell devices operation was studied as a function of the temperature from -25 degrees C to 65 degrees C varying the voltage over breakdown, from 5% up to 20% of the breakdown voltage. Optical characterization was performed using a laser at 659 nm and opportunely chosen filters to vary the optical power. We determined the single pixel gain by using both the time resolved dark count signal and the current under controlled illumination. Typical gain values above 1x10(5) and above were obtained for operation times of 10 ns, while higher gains are obtained for longer integration times and lower photon flux.