Photodiode

摘要

A photodiode (A) comprises a substrate, a light receiving layer having a band gap wavelength and including a pn-junction and at least an absorption layer having a band gap wavelength lambdg. One of the absorption layers is sandwiched between the substrate and the light receiving layer, the band gap wavelength lambdg of the absorption layer is shorter than the receiving signal wavelength lambd2 but longer than noise wavelength lambd1(lambd1