Silicon photodiode is made from a single crystal Si wafer. The band gap of silicon fits in the energy level from visible light wavelengths to near infrared (400~1100nm). The photodiode is suitable to detect lights in that wavelength range. The responsivity of a photodiode indicates how sensitive of the diode to the incident light. It is measured in photocurrent in amperes against the optical power on the diode in watts. Responsivity of the sil..