New position-sensitive avalanche photodiode with single photon sensitivity and picosecond resolution

A position-sensitive silicon photodetector based on a new principle is introduced. The detector device is a special avalanche photodiode with elongated geometry, which operates biased above the breakdown voltage in the so-called Geiger mode. The exploited physical effect is the propagation of the avalanche perpendicular to the electric field. The position information is extracted from the risetime of the current signal. Experimental device structures with active area of 140 by 14 mu m have been fabricated and tested. Spatial resolution of better than 10 mu m FWHM (full width at half maximum) combined with ultrahigh sensitivity (single photon detection) and temporal resolution better than 100 ps FWHM are demonstrated.<>