| 摘要 |
PROBLEM TO BE SOLVED: To achieve efficient absorption by reflecting light in front and rear so as to pass through an absorption layer by placing the absorption layer in a resonance cavity in order to raise absorption of the light in a surface light incident type avalanche photodiode (APD).SOLUTION: A surface light incident type APD comprises: an opening (16) for incident light; and many various semiconductor layers including a doubling layer (7), an electric filed control layer (8), an absorption layer (10) for absorbing the light from the opening to a lower part. At least one Bragg mirror (14) which is arranged so as to reflect photons passed through the absorption layer (10) from the opening, and to return the photons to the absorption layer exists under the absorption layer (10). According to an extremely preferred embodiment, at least two Bragg mirrors (14, 15) in a state that one of which is loaded on the other have different reflection spectra, and reflection spectra of the two Bragg mirrors give one wider reflection spectrum. |
