Single-photon avalanche diode with ultrafast pulse response free from slow tails

A single-photon avalanche diode (SPAD) with a novel structure is presented. The slow tail in the pulse response, which plagued the performance of previous ultrahigh-speed SPADs, has been eliminated. The pulse response is cleaner and sharper than that of the fastest microchannel-plate photomultipliers, making the new devices almost ideal for photon timing measurements on fast optical waveforms. The typical photon detection efficiencies are 16% at 630 nm and 4% at 850 nm, and the timing resolution of the 8- mu m devices is 45 ps full width at half maximum (FWHM). Unprecedented performance is demonstrated: just 300 ps after a light pulse, a signal three orders of magnitude weaker can be easily measured.>