Detectors 187
Detectors 187 : Particle Detectors: (4.25) Single-photon Avalanche Diode: A single-photon avalanche diode (SPAD) (also known as a Geiger-mode APD or G-APD) is a solid-state photodetector in which a photo-generated carrier can trigger an avalanche current due to theimpact ionization mechanism. This device is able to detect low intensity signals (down to the single photon) and to signal the arrival times of the photons with a jitter of a few tens of picoseconds. SPADs, like avalanche photodiodes (APDs), exploit the photon-triggered avalanche current of a reverse biased p-n junction to detect an incident radiation. The fundamental difference between SPAD and APD is that SPADs are specifically designed to operate with a reverse-bias voltage well above the breakdown voltage. This kind of operation is also called Geiger mode in literature, in analogy with the Geiger counter
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