AVALANCHE PHOTODIODES AND QUENCHING-CIRCUITS FOR SINGLE-PHOTON DETECTION

Avalanche photodiodes, which operate above the breakdown voltage in Ge iger mode connected with avalanche-quenching circuits, can be used to detect single photons and are therefore called single photon avalanche diodes SPAD's. Circuit configurations suitable for this operation mod e are critically analyzed and their relative merits in photon counting and timing applications are assessed. Simple passive-quenching circui ts (PQC's), which are useful for SPAD device testing and selection, ha ve fairly limited application. Suitably designed active-quenching circ uits (AQC's) make it possible to exploit the best performance of SPAD' s. Thick silicon SPAD's that operate at high voltages (250-450 V) have photon detection efficiency higher than 50% from 540- to 850-nm wavel ength and still similar to 3% at 1064 nm. Thin silicon SPAD's that ope rate at low voltages (10-50 V) have 45% efficiency at 500 nm, declinin g to 10% at 830 nm and to as little as 0.1% at 1064 nm. The time resol ution achieved in photon timing is 20 ps FWHM with thin SPAD's; it ran ges from 350 to 150 ps FWHM with thick SPAD's. The achieved minimum co unting dead time and maximum counting rate are 40 ns and 10 Mcps with thick silicon SPAD's, 10 ns and 40 Mcps with thin SPAD's. Germanium an d III-V compound semiconductor SPAD's extend the range of photon-count ing techniques in the near-infrared region to at least 1600-nm wavelen gth.