  Silicon avalanche photodiodes are the most sensitive photodetectors in the
visible to near infrared region. However, when they are used for single photon
detection in a Geiger mode, they are known to emit light on the controlled
breakdown used to detect a photoelectron. This fluorescence light might have
serious impacts on experimental applications like quantum cryptography or
single-particle spectroscopy. We characterized the fluorescence behaviour of
silicon avalanche photodiodes in the experimentally simple passive quenching
configuration and discuss implications for their use in quantum cryptography
systems.
