Silicon photodiode

Note 1: Such photodiodes are useful for direct detection of optical wavelengths shorter than approximately 1 μm.

Note 2: Because of their greater bandgap, silicon-based photodiodes are quieter than germanium-based photodiodes, but germanium photodiodes must be used for wavelengths longer than approximately 1 μm.

Source: from Federal Standard 1037C and from the FAA Glossary of Optical Communications Terms[?]