Image sensors and optical devices

Which material is suitable for photodiodes that receive light in the 1.55 µm band used in optical fiber communication?

  1. ASilicon (Si)
  2. BGallium nitride (GaN)
  3. CIndium gallium arsenide (InGaAs)
Show answer and explanation

Answer: C. Indium gallium arsenide (InGaAs)

Silicon has a band gap of about 1.12 eV and absorbs almost no light at wavelengths longer than about 1.1 µm. InGaAs has a small band gap and efficiently absorbs light in the 1.3 µm and 1.55 µm bands, so it is used for optical communication receivers. GaN has a large band gap and is used in the ultraviolet to blue range.

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