= Single-photon avalanche diode
= SPAD
{c}
{synonym}
A <single-photon detector> based on a reverse-biased <photodiode> operated above its breakdown voltage. A carrier generated by <photon> absorption can trigger a self-sustaining <impact ionization> avalanche. Quenching lowers the bias to stop that avalanche; recovery creates <detector dead time>. Random internally generated carriers can also trigger indistinguishable pulses, producing <dark counts>. <Single-photon avalanche diodes> ordinarily detect an event rather than resolve the incident <photon number>. https://hub.hamamatsu.com/us/en/ask-an-engineer/detectors/sipm-mppc-spad-questions-and-answers.html[Hamamatsu Photonics, What is SPAD? and How does a SPAD work?: above-breakdown bias and quenching]{ref}
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