Image sensors and optical devices

Which light detector is operated with a reverse bias above its breakdown voltage so that even a single photon triggers a pulse through avalanche multiplication?

  1. ASPAD (single-photon avalanche diode)
  2. BSolar cell
  3. CPIN photodiode
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Answer: A. SPAD (single-photon avalanche diode)

A SPAD is operated with a reverse bias above breakdown (Geiger mode), so even the electron created by a single photon triggers avalanche multiplication and a large current pulse. A quench circuit stops the avalanche to prepare for the next photon. Because photon arrival times can be measured precisely, SPADs are used for ranging such as LiDAR.

  • A. Correct. It is an avalanche diode that can detect single photons.
  • B. A solar cell generates power and is not used for single-photon detection.
  • C. A PIN photodiode has no multiplication.
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